1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Electric cars, trucks, ATVs, NEVs - things bigger than a motorcycle.

1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:52 pm

Meet the “Elec-tow’d” Electric Tow’d
(pronounced "Electrode", but with an Elmer Fudd accent)

You may remember the thread on my Electric VW Bus conversion (CLICK HERE), which I built in 2009 and sold last year. I will be bolting-on the 9” DC motor, 180v/500a Kelly controller, and 175v/60ah factory a123 pack, built for the 3500lb Bus, into this 1000lb B.F. Meyer’s Tow’d.

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Design Objective:

Auto Manufacturers are designing Electric Cars with long range, trying to make them direct replacements for Gasoline cars. To me, that is like trying to design a sailboat to replace a water-ski boat – it won’t do either job well. 90% of commuter miles today are made by one or two passengers traveling less than 30 miles/day; EV’s excel at this duty cycle, so I think it is a mistake to design them to service the needs of the other 10% - which frankly they suck at.

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The superior energy density of gasoline makes it a far better fuel choice if you need to travel long distances, traverse many steep hills, carry heavy loads, or refuel quickly. If you are in the 10% of the population with such a regular duty cycle, then an Electric Car is a poor choice for you until commercially available batteries achieve the power density of gasoline.

However, an ICE needs to shed a tremendous amount of heat and waste gases, requiring a heavy engine block, cooling system, and exhaust system, not to mention complex infrastructure to manage and power these different systems. The weight of all this infrastructure requires a heavy suspension system, and a heavy braking system to stop it, a more powerful engine to move all that weight, and a heavier transmission to convey the extra power from the engine… And because they are all so big and heavy, we need a big chassis to protect us when another ICE bumps into us. If you are one of the 90%, then the complexity and lugging all that excess weight around makes a Gasoline car a poor choice for you.

An EV can get the same performance from much lighter electric motor/controller, which doesn’t require things like liquid cooling or exhaust. Less weight means suspension/brakes/chassis can be lighter too, resulting in a power-to-weight ratio that makes the EV far more efficient; the less mass you have to move, the less energy it takes. Since the infrastructure is modular and less complex, it is cheaper and easier to maintain. Since the EV requires less material to build, it can be cheaper to build than a gas car.



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However, Automobile Manufacturers wipe out an EV’s advantages when they include a heavy expensive battery pack rated at > 100 mile range, instead of one that sized to the 30 mile range needed by 90% of commuters. Triple the battery means triple the cost, triple the weight, triple the charge time (often overlooked), yet it still fails to offer the cross-country abilities or the performance of a gas car. To offset the weight of the massive pack, compromises are made, like using too small a motor, or the EV is built on an econobox platform instead of something fresh and purpose-built like the Aptera. Even worse is the hybrid, which adds the complexity, expense, and weight of two drive trains for marginally better gas mileage.

NEV’s are a step in the right direction, but the 25mph speed limit is too restrictive - I can’t use an NEV because my commute ends with the 45mph road my company is located on. We need a new class of EV that is restricted by weight, not speed. Since speed eats range, and range is limited by weight, speed is intrinsically limited.

I believe that the correct answer is an EV that plays to the strengths of electric power. Sizing the pack to a 35 mile range, and leveraging electric power's reduced infrastructure, yields an inexpensive lightweight vehicle, which allows for snappy acceleration and handling as well as a strong top end. I hope to demonstrate my belief with this build.





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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:52 pm

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Selecting the Donor model

A few years passed as I idly looked for a lightweight donor suitable to the task. The Ariel Atom would be perfect, but far too expensive, and everything else I found turned out to be too heavy. A tiny 1990’s Suzuki Swift seemed suitable, but it still weighed 1,900 lb and looked like an econobox – exactly the image I want to get away from. The VW bug was a bit lighter, 1,700-1,800 but still too heavy for my purposes. I liked the panache of a Porsche Spider or Speedster clone, but Jack Rickard beat me to the punch by building both with giant battery packs, and performance/weight on those cars was less than I would like to acheive. His builds helped me realize that I wanted a donor even lighter than a full-body fiberglass kit car, and more importantly that I wanted to restrict weight by using a smaller battery pack that was sized to my duty cycle.

Then I read that a vanilla B.F Meyer's Manx Dune Buggy weighs about 1,300lb, after the 500lb-600lb Bug body is replaced by a 100lb fiberglass dune buggy body, and the body pan is shortened. Not only was that in the weight range I was looking for, but it had two viable locations for a battery pack, and I could simply bolt on the electric motor/controller assembly stripped from my VW Bus conversion.

I began searching Samba and Craigslist and feeBay for the right Buggy. I also considered using a few Sandrails which had been registered as Special Construction (aka homebuilt) vehicles. They were lightweight with a full roll cage, and still I might build one some day, but I was worried my point would be lost because it looks so skeletal.



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Then one day I discovered the genius of Bruce Myer’s 1,000lb “Tow’d”. As dune buggies like the Meyer's Manx caught on, and were being towed on trailers to the desert for fun, Bruce developed a model that was light enough to be easily towed behind a regular car without a trailer. He achieved this by removing the VW pan altogether, and replacing it with a molded fiberglass body, supported by a steel hoop with mounts for a standard VW front end and rear end. Seats were molded into the body, saving even more weight. A tow-bar was built-into the steering wheel support column; every part served multiple purposes.

The offroad Tow’d generated demand for a street version, named the “Towdster.” Bruce designed a removable hood/windshield, engine cover, and fenders, so a buyer could drive it to the desert, remove the body panels to make it even lighter, and have fun. The Tow’d/Towdster went on to do well in competition, and was the father of the modern sandrail.

The Tow’d is a complete, stylish buggy, yet elegantly minimalist. Because Bruce designed it to be light enough to tow, it is also a good donor for an EV. There is plenty of room for an a123 battery pack where the gasoline tank rests between the seats – and if I wanted to cut into the roomy trunk I could even fit two full packs. I had found my preferred Donor.



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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:52 pm

Image
... Motor, CanEV adaptor plate, flywheel, clutch, pressure plate


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... Controller, charger, shunt, and contactors on an aluminum cooling plate with phenolic protection


Image
... The pack will consist of the (4) beige a123 modules in the foreground (not the green PSI modules behind them).



Doing the Math:

The VW ICE motor/exhaust weighs around 250lbs. I think the gas tank will weigh about 30lbs, and the 11 gallons of gas 88lbs, 118lbs total. Say 12lbs for the starter, and 35lbs for the 12v battery, I will be removing 415lbs of ICE infrastructure from the car.

The ADC FB1-4001a electric motor weights 143lbs, roughly 150 lbs with the adaptor plate. The a123 battery pack weights 196lbs. Cables and the controller/charger assembly weigh 35lbs with a big aluminum cooling plate. That is 376 lbs of electric infrastructure going back in. If the aluminum battery box ends up at less than 39lbs, then it will be the same weight as stock. While it is not a design criteria, I wouldn’t mind the bragging rights of being in the triple digits, weighing less than a thousand pounds.

The motor on aircooled VWs is located behind the rear wheels, which is sort of an awkward location for weight distribution, taking weight off the front wheels. Even though the overall weight will be roughly the same after conversion, the electric motor makes it 100lb lighter behind the axle, and the batteries add about 100 lb in front of the axle, so the mass is more centered in the chassis, and the front/rear balance is improved. The electric motor’s mass is more compact about the axis of rotation than the gas engine, making it faster to transition into and out of a turn.


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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:52 pm

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Finding the Right Donor:

Over an 8 month period, I looked at a dozens of Tow’ds, and considered hundreds of other dune buggies and sand rails. The Tow’d I bought one is actually the very first one I noticed. I had conversations with the seller September 2012, but his firm price was 20% more that I thought it was worth. At the end of October, I watched his ad (which had been run a few times) scroll off the end of the classifieds section and expire.

By the time April 2013 rolled around I was ready to buy; I had seen enough tow’ds and dune buggies to know exactly what features I preferred, and I had been over the project in my head so many times I was burning to get it off my mind. I was about to put an offer in on a tow’d that had most of what I wanted, but that first blue tow’d kept popping into my head. I emailed the seller, hoping his ad expired because he gave up, and maybe was more flexible in his price…

He replied that he still had it, but even though the market had clearly demonstrated he was asking too much, he was still firm on price. Being fixated on a particular model, or even worse a specific example, is a quick way to pay too much, but there I was. I made several offers, but finally caved in and gave him his asking price; he had found the one rare buyer who found full value in most of the upgrades he added. I don’t think I’d get my money back if I turned around and sold it, but it is convenient because it has everything I wanted, so I don’t have to go through the hassle or expense of upgrading it, on top of doing the conversion. Here are the features I valued:


. . . . . California Special Construction Title – Used to be that people would cut the VIN tag off a bug, rivet it to the dune buggy, and register it as that bug. Word is they are cracking down on that these days, so one needs a “Special Construction” title to register them. Since this is already registered in CA, and registered as special construction, that hassle is cleared for me. My time is in short supply, so avoiding that hassle is worth more to me than most folks. This is the _only_ SPCN tow’d I found, and probably the biggest logical reason for selecting this car. Here is a nice writeup on how SPCNS works for Electric Vehicles – since we don’t need to worry about smog, it is easier for us:
SPCNS Electric Vehicle Registration in California



swing vs irs.jpg
ith Swing Axle the tire meets the road at an angle dependant on how compressed the suspension is, with IRS the tire stays perpendicular to the road throughout the whole range of compression.
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The Swing Axle is structural, the IRS axle is not so it adds a trailing arm
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. . . . . IRS Rear End - The type-1 VW (bug) came with two types of rear transaxles, that are colloquially known as “Swing axle”, and “I.R.S” (Independent Rear Suspension). This is a bit of a misnomer, since both types are actually independent. The earlier swing axle pivots about the transaxle, moving the wheel between positive and negative camber, but the IRS has two u-joints that keep the wheel square to the road.

The swing axle is 40lbs lighter and cheaper to harden for high HP engines, but the +/-camber transitions can make it unstable in corners. I have much love for the swing axle because I learned to drive on a ’66 bug. As my teenage driving got wilder and wilder, I learned to leverage this instability to kick the back end out around every curve and corner, doing what is known today as Drifting. I also mastered the bootstrap turn – at full speed, throw the wheel and tap the parking brake to break the back end loose, then pop the clutch to slide around until pointing/accelerating the other way. I kept these misbehaviors up until I rolled the bug in a Church Parking lot and my mother grounded me for life. :D I still remember climbing out the door of the bug (it was on its side), and seeing the teams, coaches, and parents from multiple little league games on the fields next to the church, pressed up against the chain-link fence and watching me…

Anyhow, this build is so light I’ll run out of traction before I can add the crazy HP I would need a swing-axle to support. Even though it went against my design objective of light weight, I was willing to trade the IRS’s extra 40lbs of weight for its superior traction and handling.



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The link pin assembly on top, Ball Joint assembly in the middle. The strut assembly on the bottom is not typically used on Dune Buggies because they don’t have a connection point for the strut.
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. . . . . Ball Joint front end - The earlier Link-Pin front end is more durable and preferred for off-road, but ball joints give better road feel. If I was building it up from scratch I’d put a $2k Red 9 double-wishbone suspension up there instead; I still might do that in the long run, but on such a light build the stock VW suspension should do fine.


. . . . . Front Disk Brakes - Although a small buggy doesn’t need much brake, I prefer the lighter weight and fade resistance of Disk. This buggy has a Kharman-Ghia front end, which comes with disk brakes.

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. . . . . Aesthetics - This buggy was the pride and joy of a 75 year old man who built and maintained it for 18 years, not to mention did a lot of nice little upgrades. The front fenders are Unique, custom fit to the shape of the wheel, whereas the stock Tow’d fenders are giant ungainly unaerodynamic wind scoops. He added a third set of Taillights to the top of the roll bar, with wires concealed inside. He added a bimini top and plexi rear window contain the passenger compartment. Thin-tube bumpers/ plate mounts, side deflector windows, custom seat padding and dash are nice extra’s, plus a sound system I might remove to save weight.

The paint is glossy and I like the shade of sky blue. The custom black rims with silver hubcaps he welded suit my aesthetic; however, I might end up trading them out for lighter rims/tires if the weight savings is significant.
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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:53 pm

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Paying the seller:

A wire transfer offers little documentation and zero protection for the buyer, and Paypal fees would be expensive for a car, so I was pleased when the seller agreed to take USPS Money Orders. The great thing about USPS MO is that they give the seller easy access to the cash, while providing security to the Buyer. The seller can cash them at any Post Office, or at least or verify their validity at the PO before depositing them in the bank. They also provide good documentation if fill out details of the transaction on the MO, so it can protect both the buyer and seller. Scams are rampant on other types of MO, but falsifying or stealing a USPS MO is an offense with Federal penalties, so it is the only type that I personally will accept.

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My bank does not have local branches, so when I need cash I use an ATM to take out the max of $400/day, which would have taken awhile. I discovered that I could use a Debit card at USPS to buy the MO; since each MO is a maximum of $1,000, I needed a few of them. However, if you buy $3,000 or more a day (or cash $10,000 or more a day) you are required to fill out some complex extra form – so I broke the purchases out over multiple days so I wouldn’t have to.

I called the Post Office near the seller, to ask them to have extra cash on hand for the MO I was sending him. They reported that they could only pay MO with the cash on hand, so that could have been a problem, but the seller ended up depositing them in the bank.

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I used USPS Express Fail to overnight the payment, and included a prepaid Express Fail envelope for the seller to return the title and bill of sale. I thought shipping USPS MO via Express Fail would give me the best documentation possible, but after my experience I will NEVER use it again.

I thought it would be delivered next day by noon, but when I checked the tracking # the next morning, it still showed the package as local, with a delivery before 3:00pm (2) days after I mailed it, not next day. Turns out if I dropped it of at a mailbox before 8:00pm, it would be there next day by noon, but if I dropped it of at the Post Office between 3:00-5:00, their commitment was pretty much the same as Priority Mail. Later the tracking had conflicting entries telling me the package was local to both the seller and I. Finally however, it showed the package was out for delivery… and I spent the next 5 hours refreshing the tracking page every 30 seconds. Finally, I called the seller to apologize for the funds not getting there… and he reported he got them 5 hours ago, depositied the MO, and dropped my title in the mail. The tracking status took (12) hours to show the package as delivered. They did feature email updates for the tracking – they sent that email (3) days after delivery. USPS doesn’t quite understand the purpose of tracking.
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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:54 pm

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Overnight shipping of a car:

A decade ago, I shipped my s2000 coast-to-coast via a company called D.A.S. for $1,000. With a corporate shipper, the car is hauled to a regional depot via truck, unloaded, and sits until it gets loaded onto a different truck and taken to the next regional depot, over and over until it gets to the recipient. This takes weeks and weeks, things can happen during the repeated loading/unloading, and no single person is responsible for your car.

DAS quoted $1,000 to ship the Tow’d 500 miles. I took a look at uship.com, which is a marketplace for individual shippers to bid on jobs listed by consumers. I got a quote from Casey at DRFTco who had really good feedback. He was just what I wanted – a single person to be responsible for my car, who would pick it up and deliver it, and since it was shipping direct no depot delays. Plus it was only $600.

However, there was a timing element – he had room on his trailer, but he was leaving Portland the same day the seller got the MO, and would pass by the seller the following day at lunch. If USPS had missed delivering the MO like I thought, or the seller wanted the MO to be cashed before shipping, I would have missed Casey’s window and had to use DAS instead, so I was stressed.

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Instead of being late like other shippers, Casey got to the seller an hour and a half earlier, and called me the moment it was loaded. Then he said he would be getting to my area after 8:00-9:00, and asked if I wanted him to drop it off then, or the following morning. I told him whenever he got in, I would be available to receive it. I realized – the seller got paid on Tuesday, I got the car on Wednesday, so from my perspective I got overnight shipping.

He called to give me status during the day, and arrived at 8:45pm. As he unloaded the car, he passed on the seller’s message that he thought he had put too much oil in… This is code for a leaky engine, I was told the same thing when I bought the Bus, which turned out to have a profound oil leak. Not a surprise on an aircooled VW, but heavy sigh.

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I drove the Tow’d down the street, and the moment it bumped up my driveway ramp, the headlights went out, and black smoke started pouring out from the center of the dash, I stopped it cold. “My god” I thought, “This car is going to burn up before I even get it in my driveway.” The only thing behind the dash is wiring, so something shorted, but the fuse blew or the wire melted, the lights came back on and the smoke tapered off. I disconnected the battery after it was in my garage.
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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:54 pm

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Doing the Math:

The VW ICE motor/exhaust weighs around 250lbs. I think the gas tank will weigh about 30lbs, and the 11 gallons of gas 88lbs, 118lbs total. Say 12lbs for the starter, and 35lbs for the 12v battery, I will be removing 415lbs of ICE infrastructure from the car.

The ADC FB1-4001a electric motor weights 143lbs, roughly 150 lbs with the adaptor plate. The a123 battery pack weights 196lbs. Cables and the controller/charger assembly weigh 35lbs with a big aluminum cooling plate. That is 376 lbs of electric infrastructure going back in. If the aluminum battery box ends up at less than 39lbs, then it will be the same weight as stock. While it is not a design criteria, I wouldn’t mind the bragging rights of being in the triple digits, weighing less than a thousand pounds.

The motor on aircooled VWs is located behind the rear wheels, so I have the added bonus of moving 100lb weight forward of that awkward spot, to the battery pack in front of the rear wheel. The electric motor’s weight is very compact about the axis of rotation, making it faster to transition.

with ADC IMG_3597.JPG
The ADC FB1-4001A motor is on the right of the engine, so you get an idea of the size comparison. The ADC will stick out almost as far as the back of the exhaust pipe.
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The pack will be the last one I had in the bus, 29”x13”x9.5”, 196 lbs. It is comprised of factory-built a123 modules configured in 49s3p of the 20ah prisimatic LiFePO4 cells. That makes it 175v60ah, 9.6kwh, with 7.7kwh usable at an 80% DOD. I expect the Tow’d to consume between 200 and 250wh/m, which would yield a range between 31 and 39 miles. Note that this pack has the same usable kwh as a 1000+lb 120ah lead-acid pack that can only support a 50% DOD and has higher resistance that wastes current and sags more significantly under load.

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Re: Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Thu Jun 06, 2013 6:54 pm

A closer look:

Image



I spent the entire weekend, 20+ hours, cleaning the tow’d and going over it in the process. It was covered in a decade of grime and dust that had hardened into a layer that would not smudge when dry, but it came up easily enough with soap, water and a bit of elbow grease. I went over the engine and it was surprisingly oil free, just a little dried oil around the pushrod tubes. Here are a few pics to give you an idea...

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The tube on the left side of the "rear bumper" has been cleaned, the right side has not, so you can see how much grime was on there.
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The front end before
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d_after IMG_3490.JPG
Look at the vertical tube in the middle of the picture (Steering column support and housing for the integral towbar), and the horn underneath, and you can see the difference
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IMG_3492.JPG
The metal strip holding the speakers under the cowl was resting on the wires... I moved it underneath, and later wrapped them in some rubber. Note the large iron dashboard mounted to the steering support colum in the center, and the outrigger iron support on the drivers side, that makes a little "hop" over the steering column.
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It was interesting to see the many innovations/upgrades the PO had added over the years, here are a few that come to mind:

    An extra pair of mounts to secure the bottom of the cowl to the chassis (but it still shakes like crazy!)

    Glassed in the nose, covering the tube for the towbar so I can't use it, but helping aerodynamics.

    A cover over the rear trunk, secured with a lock (although he cut into the body for the locking tab)

    CD Player, and speakers under the front cowl (with their sharp-edge metal strap resting on 12v wires)

    The iron dashboard – I was concerned about the added weight, but in the end I really like this.
    A thick iron plate, with a few heavy weights, to the front end. Not sure if this is intended to keep the nose down (the engine has a fair amount of torque) or improve handling. I’ll need to remove it to meet my weight target, but I am inspired to consider putting the (3) 7s batteries up front, there is more space than I thought.

    Fog lights, that only come on with the low beams (per the law)

    Clip to hold papers

IMG_3492.JPG
The metal strip holding the speakers under the cowl was resting on the wires... I moved it underneath, and later wrapped them in some rubber. Note the large iron dashboard mounted to the steering support colum in the center, and the outrigger iron support on the drivers side, that makes a little "hop" over the steering column.
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I repaired the wire that had shorted, and discovered a brake fluid leak. I removed the top of the drivers rear seat because it was too tight, now steering reach is perfect, and can work the clutch without banging my knee - it is a pretty good fit now. Put a few gallons in the tank, and drove it to the beach for its maiden voyage. Drove it to work today, one of my co-workers noticed that the fuel line rests on the exhaust manifold (wrapped in fiberglass cloth) and the tube going into the

z green IMG_3487.JPG
The burned wire turned out to be a single wire that snapped (green with corrosion) and either arced internally, or grounded out to something.
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The upper part of the seats he added, are bolted to the body. The bolts are way too long, and point straight at the gas tank, Ford Pinto style. I had to take out the one on the driver’s side, now steering wheel is at a perfect distance and the pedals are pretty good.

There is a brake fluid leak, I think it might be the reservoir, although it could be the master cylinder. I thought the reservoir was empty, but after I bought new brake fluid I discovered it was full, the fluid was fresh and clear. At first I thought it was nice that he changed the fluid (like the motor oil) but now I think he just had to keep on replacing it.

The fuel line is routed such that it rests on the exhaust manifold, although with a thermal cloth shield, which gave me concern. A buddy of mine also noticed the rubber fuel line hose is cracking where it enters the fuel pump – I won’t drive it again until I re-route the fuel line and replace the hose and wire-tie it down.

Although the motor is quiet for a bug motor when revving it in a parking lot, but it is distractingly loud on the street, because the seats are so close to the motor with nothing inbetween. The motor mounts are old, the motor really shakes while idling. I look forward to driving it without all the noise and vibration. :mrgreen:



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Re: "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby Rassy » Thu Jun 06, 2013 8:50 pm

JD, I like it. Quite a switch from the VW Van. Did you purchase it used? Looking forward to seeing your completion and how it meets your expectations.
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Re: "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby The fingers » Fri Jun 07, 2013 12:17 am

Always loved VW dune buggies and baja bugs too. The Meyers Manx is the coolest. 8)
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Re: "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby burner1 » Fri Jun 07, 2013 11:37 am

JD, I was treading your design objective whcih brought me back to some poitns I have always thought about.

One problem in looking at reducing energy consumption in travel.....is the layout of our cities. We get in a small car, get on roads, highways necxt to large trucks (like the Ford F350 I own), semi's, box trucks, etc. It is a lousy mix for small cars. Small cars are helpful. I say helpful because it is a small part of energy consumption although I think it is viewed as a lmuch larger contributor then what it is....But that's a seperate topic.

Anyway, I think we drive big vehicles because of the roads and environment. It is our choice. If I get on the road with big vehicles I want to be in a big vehicle. It's just the way it is.

If I thought I could make a change in the grand scheme of things I would change the layout of our comunities to utilize small cars. I am ot the first to sugest this and I thing there is some effort to do this here and there.

What I see is a comunity of houses and apartments where the internal roads are for smaller cars perhaps even golfcarts as long as they did not impede cars which would go a bit faster. On the outside of the comunity your not restricted. Most places with in the comunity have inside access or outside access. Most common convieniences are available through the inside access. This would include remote offices so you could leave your house to work but you would not be driving an hour in rediculous traffic in an over sized car to get there.

I am no fan of public transportation. When a city gets so big it has to have it. Our cars are like our brief case or purse. They are our personal areas and it is hard for people togive that up. Theya re secure areas for us as well. There are something we as a society desire.

When we see the government try to dictate small cars for fuel economy and put them next to semi's going 70 mph on freeway in all sorts of road conditions, well, I don't like it. I think much of the solution is actually the infastructure itself which makes the smaller car usable and even desirable.

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Re: "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby fechter » Sat Jun 08, 2013 4:12 pm

The dune buggy looks great! Shaving 1,000 lbs or so off the vehicle weight will make a world of difference compared to the VW bus. You should be able to get some pretty good acceleration (more EV grin).
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Re: "Elec-tow’d” Electric Tow’d Dune Buggy Build Thread

Postby oatnet » Mon Jun 10, 2013 8:07 pm

Bump - I added text and pictures to the "reserved" posts above, there is a lot more to read now.

Thanks Fechter! I'm not shaving off 1,000 lbs though... The ENTIRE CAR weighs 1,000 pounds.

That is why it took me so long to select the correct donor... Basically, I am moving the powertrain that was adequate to power a 3000-3500lb Camper bus up hills, into a vehicle that is less than a third the size. I hope the acceleration will be brisk. :lol:

Thanks Rassy! Yep, I bought it used. Most of the time I was negotiating with the Son, whose 75 year old Father did the rebuild, after purchasing the tow’d from the Grandfather, who was a body repair guy who took a lot of things in trade. Dad said something about doing the rebuild 18 years ago. However, the SPCNS VIN was assigned in 2003, and I think the grime buildup looks more like a decade than 18 years… So maybe he ran it offroad before doing the rebuild. Paint is crisp, but it has about a decades worth of paint chips on it… Oh, he told me that the color was “Pepsi Blue.”

Thanks Fingers! For me, it is a tossup on whether the Myers Manx or the Myers Tow’d is coolest – depends on which way you want to go. With the custom fenders, I think the Tow’d looks kinda like a poor-man’s Ariel Atom.

Thanks Burner1! I’m afraid I must not have done a good job explaining my design objective. There is so much hype today about range anxiety in EVs, that the first question we typically get is “how far does it go?” The question they should be asking is “how far do you NEED to go?” We advocates need to educate the consumer that EVs are in a different niche from gas cars, and that Gas or EV is far superior in its own niche. Electric’s niche is actually 80% of the market, so...


Steps Forward

1) Install the Electric Motor. I dreaded this step when I converted the VW bus, but found out it the motor is held on by only 4 bolts, so it ended up being the easiest task.

I planned to bolt the motor/flywheel/clutch/pressure plate assembly from the bus straight on, until I remembered that the Bug uses a different flywheel from the bus. On the Bug the input shaft pilot bearing is in the gland nut holding down the flywheel, instead of being in the crank like the bus. Thumbs up to Randy of CANEV, who offered to supply me with the bug’s hub adaptor at a really good price – but I am a little concerned about how I am going to keep the electric motor’s shaft from spinning when I apply the 250ft-lb of torque specified for the gland nut that holds on the flywheel.

I have to replace the flywheel either way, so another option is to replace it with one that fits on the Bus adaptor, but has a feature to accommodate the gland-nut pilot bearing. A gas engine has drag, so it needs a heavy flywheel to keep RPMs up when you release the throttle, as well as smooth out surges from the series of tiny gas explosions that generate power. An electric motor has very little drag and generates power smoothly, so it does not need a freewheel – in fact, the lack of drag makes it harder to apply the clutch, because RPMs don’t drop off enough. Therefore I will have the flywheel lightened as much as possible, even cutting off the ring gear used by the starter motor.


2) Have the battery box built. My battery box will sit over the rear torsion bar, which carries the full rear weight of the car. I’ll make clamps that bolt the bottom of the box to the torsion bar, so it carries the weight directly instead of the frame. The top of the box will bolt directly to the existing Gas Tank mounts for stability. There is plenty of room in this space, but I want to tweak position to move the batteries as low and as far forward as possible, and I can’t do it until I have the Tow’d in my garage

I also considered welding a battery box cage on the front end that extended the wheelbase and put the battery mass between the front wheels, but that added complexity, weight, and lengthened power cable runs.

3) Mount battery and control system. I will use the complete control system I used on the bus, which consists of a thick aluminum cooling plate, with the controller, charger, three relays, and a shunt, in one complete package. The motor-side of the battery box will have a welded shelf to mount the controller assembly.

I have lots of 4/0 marine-grade power cables, which I can cut to size and reterminate if needed. I’ll need to design a plate to mount the throttle pot, and run wiring for the CycleAnalyst and power to drive the relays. I’ll power the lights and signals from an LiFePO4 battery, and at some point will put in a DC-DC controller with auto shutoff to replace the extra LiFe battery.

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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby JennyB » Tue Jun 11, 2013 9:26 am

It seems ironic that a vehicle designed to be towed had to be delivered on a trailer. :?

I have a mad idea: a whole class of short-range lightweight EVs, some with minimal driver accommodation, some pedestrian controlled, designed to be towable at highway speeds. Add a net-based booking system so that when you need to travel farther you can arrange for your EV to be picked up by someone with a tow hitch who is travelling in that direction. If that takes off then maybe you could have professional drivers and tugs that could handle a whole train on EVs at once. 8)
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby muffildy » Fri Jun 21, 2013 12:48 pm

the whole problem with manufacturers trying to market a new car is that they have to meet the expectations of the federal government, as well as the public.
So, the fed wants a car that is crash safe and has low emissions. got the emissions part, but that car is dead in a crash.
the general public want a car with no range anxiety, lots of horsepower, lots of interior space, and lots of luxury type features.
So, what you get when you add all that together is a VERY expensive electric car.

your project looks good, but has a few issues; its an open car so it cant be driven in the rain, you would die in a car crash, the aerodynamics of the vehicle are terrible which is related to it being an open car. That means the faster you go over 50 mph the less range you will have by a substantial amount from turbulance. Not too many luxuries possible without enclosing the car either.

You conversion and even the mainstream EVs on the market today do not meet my needs; i have a 27 mile each direction cummute; so an EV would need atleast a 60 mile range for me to even be comfortable with it. Since a 60+ mile range Ev is going to set me back oh 35k or so, its far more economical to use a diesel car.

What would work for me however is something like http://www.eliomotors.com/ and if i wasnt in the process of building my own hybrid EV i would have reserved my own even though its a gas car simply because its cheap as hell and gets extreme MPG.

In my opinion, what the chevy volt should have done is something more like this: http://www.tatamegapixel.com/key-feature.asp which would likely have been far cheaper to produce.
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby oatnet » Wed Jun 26, 2013 6:59 pm

JennyB wrote:It seems ironic that a vehicle designed to be towed had to be delivered on a trailer.

We found humor in that too!

You conversion and even the mainstream EVs on the market today do not meet my needs; i have a 27 mile each direction cummute; so an EV would need atleast a 60 mile range for me to even be comfortable with it. Since a 60+ mile range Ev is going to set me back oh 35k or so, its far more economical to use a diesel car.

I agree, you are one of the people with needs not well-suited to an EV, although if you can charge during the day, even this 35 mile build would service your commute. However, "Mainstream EVs" like the Leaf or MiEV could meet your needs for oh 20k or so, after tax credits, without diesel pollution.

Anyhow, on with the show...


Demolition:

My original plan was to measure out the space for the battery box, design it, and drive the tow’d as a gasser until the box was built. However, the car had 2 issues that needed addressing immediately. First was a pretty bad brake fluid leak, which turned out to be only a cracked reservoir, not a bad master cylinder. I found a neat trick of using the reservoir from a 1985 Volvo station wagon (I’ll show pictures when I install it) but here is the old one:
a1 IMG_3732 cracked reservoir.JPG
Multiple cracks around the cap, and along the seams that join the upper/lower halves.
a1 IMG_3732 cracked reservoir.JPG (208.47 KiB) Viewed 12377 times


The other issue was the gas line, which was run such that it rested on the hot intake, right over the cylinder head; it had a tube of fraying thermal material “insulating” it, but at best it was risking vapor lock, and at worst it was a fire hazard. Worse, when I bumped it with my hand, gasoline squirted out from the fuel filter area directly onto the exhaust. If the engine has been hot, it would have made a good size fireball. The engine shakes a whole lot because the motor mounts are trashed, so I was a little worried about squirting fuel fire hazards. I decided I’d better replace the fuel line before driving it again, but I didn’t find 5mm VW fuel line locally, just the standard ¼” (6mm) stuff, so I’d have to buy it online.
aiMG_3627 fuel line.JPG
the intake is silver in the lower right, the fuel line is in the sleeve on top of it, and leads to the gas-squirting fuel filter behind it.
aiMG_3627 fuel line.JPG (188.78 KiB) Viewed 12377 times


Further, I was having trouble designing the battery box. Because the tank is 10.5” diameter and the battery pack is only 9.625” tall, I thought I would have plenty of room… But the top of a square battery can’t fit as far up into the “peak” behind the driver’s seat as the round gas tank (duh), so space is tight, and the elegant square box I envisioned, instead needs to be complicated and convoluted. I started to realize that I was going to need to get the gas tank out before I could sort a proper design with cardboard. I’d need to take the fiberglass body off the frame to do that, which would require me to dissect most of the controls, including the brakes, emergency brakes, clutch, accelerator, stick shift, center plate…

I needed to do the teardown because the project was being held up by battery box design, but it took me a few days to resolve myself to it. Once I invested the time to take the buggy apart, it wasn’t going back together until it was electric. Something in my heart aches at the thought of rendering a fully functional machine into a pile of parts, and leaving it like that for weeks or months before figuring out how it goes together again - but that is what was needed.


bIMG_3717 rerar fender standing .JPG
the rear fender resting on one side, it is taller than I expected!
bIMG_3717 rerar fender standing .JPG (181.71 KiB) Viewed 12377 times

I started with the rear fender. At first I was stymied by bolts that were blocked by taillight supports welded on by the PO, until I realized those bolts secure the fender to its imbedded support beam, not to the frame, and found hidden bolts that were keeping me from taking it off. The Tow’d rear fender is huge, but weighs only 25.20lbs, half of what I projected. The front canopy, complete with windshield, mirrors, and wiper, weighs 47.00lb.

cIMG_3708 rear fender off .JPG
rear fender off
cIMG_3708 rear fender off .JPG (240.27 KiB) Viewed 12377 times


dIMG_3705 rear fender off .JPG
rear fender off
dIMG_3705 rear fender off .JPG (231.11 KiB) Viewed 12377 times


eIMG_3703 crack .JPG
The area I cleaned looks much nicer than the dirty area that was under the fender. I was disappointed to find a tear in the fiberglass body – see it under the back of the rollbar? Gonna have to get that sorted.
eIMG_3703 crack .JPG (244.61 KiB) Viewed 12377 times


fIMG_3715 roll bars off.JPG
Then I got the roll bar off, with 4 simple bolts, and it weighed in at 33.40lbs with the plexiglass and third brakelight.
fIMG_3715 roll bars off.JPG (233.98 KiB) Viewed 12377 times


gIMG_3734 stripped.JPG
Canopy, Fender and roll bar off – with a 12s a123 prisimatic pack on the back for scale.
gIMG_3734 stripped.JPG (219.81 KiB) Viewed 12377 times


hIMG_3737 stripped.JPG
Canopy, Fender and roll bar off
hIMG_3737 stripped.JPG (221.21 KiB) Viewed 12377 times


I tried to press the body up off the frame a little bit, but it didn’t budge. I pulled the stick shift handle, shift rod, and parking brake to remove the center tunnel cover. Then I found out the metal box the pedal assembly is mounted to, is welded to the center tunnel cover – oy. I removed the clutch cable from underneath, the throttle cable from on top, unbolted the master cylinder, and unbolted the pedal assembly. Finally, I was able to remove the center cover.
jIMG_3963 clutch cable.JPG
clutch cable, in the tunnel under the body.
jIMG_3963 clutch cable.JPG (173.77 KiB) Viewed 12377 times


kIMG_4063 gearshift plate.JPG
gearshift mount, SPCN VIN tag in front of it.
kIMG_4063 gearshift plate.JPG (176.63 KiB) Viewed 12377 times


After the center cover came off, the original Tangerine Red gel coat peeked out – and a B.F. Meyers Inspection Tag! Given the condition of the Meyer’s serial number tag, I still considered that it could be a Sandhopper body made after the molds were sold, but now I am confident this is a genuine tow’d.
lIMG_4082 tag in place.JPG
On the bottom, notice the center cover with the pedal box welded on. Also, the kludgy strap-mount that cracked the brake reservoir, and patch of paint removed by leaking fluid. Finally, original gel coat under the center tunnel, with the B.F. Meyer’s sticker in the middle!
lIMG_4082 tag in place.JPG (188.54 KiB) Viewed 12377 times


mIMG_4079 Meyers tag.JPG
The Meyer’s Inspection Tag, close up. This discovery adds value to my purchase, which means I overpaid less than I thought. OTOH, the black nub below the sticker is my throttle cable. Gonna have to re-engineer that.
mIMG_4079 Meyers tag.JPG (223.24 KiB) Viewed 12377 times
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby oatnet » Wed Jun 26, 2013 7:12 pm

Designing the battery box:

Still, no joy – the body did not budge even though I could not see anything binding, until I took off the seat bottoms. While the PO had secured the seatbelts to the side of the fiberglass body, 5” up he put a small screw through each seatbelt, and the body, into the frame. Not sure what purpose they served besides chewing up the seatbelt, but once they were out, the body lifted right off – finally!

nIMG_4065 body lifted.JPG
I put a board under the body, and jacked it up just a little. You can see the rail of the frame, and the roll bar supports, peeking out orange and dusty.
nIMG_4065 body lifted.JPG (201.13 KiB) Viewed 12375 times


o1IMG_4131jacked up.JPG
after checking things out, I jacked it up as far as it will go without removing the cable runs from the body too. This exposed the full roll bar support on top of the frame rail, which is directly over the torsion bar/gas tank support under the frame rail.
o1IMG_4131jacked up.JPG (244.09 KiB) Viewed 12375 times


o2IMG_4086 body lifted and tear.JPG
the body jacked clear of the frame, the end of the torsion bar jutting out ahead of the rear wheel. The gas tank is mounted over the torsion bar, and its end is hidden by the orange, dirty roll-bar support. Also, another shot of the tear.
o2IMG_4086 body lifted and tear.JPG (144.56 KiB) Viewed 12375 times


pIMG_4072 gas tank.JPG
the gas tank before removal. I am going to have to neaten up that wiring mess, and probably re-route the brake lines.
pIMG_4072 gas tank.JPG (191.12 KiB) Viewed 12375 times



I had some trepidation about draining the tank because I’m not used to working with gasoline, but it has a fuel shutoff valve underneath so it was pretty easy to stop/start flow to safely fill gas cans. Two long u-bolts secure the torsion bar to the frame at the bottom, and the gas tank’s flanges at the top. Once the nuts were removed the u-bolts came out very easily. I had to wrestle with the empty tank to extract it, because the loose throttle/clutch/ebrake cables were in the way. The 11 gallon tank weighs 28.8lbs, is 35” long, and 10.5” diameter at the larger end plates, but 10.125” diameter across the body of the tank. Since gasoline weighs less than water (6.2lb/gallon) the full tank would have weighed 97lbs.

qIMG_4129 empty space.JPG
Open space after tank removal. You can see the depression for the “trunk” sticking out under the fiberglass body. Note that the trunk’s left front is deeper than the rest – this is where the ICE battery went. If I was willing to cut out the trunk area, I could fit a HUGE amount of battery… but my challenge is to size the pack to my needs, and fit it into this space WITHOUT damaging the collectable bodywork.
qIMG_4129 empty space.JPG (217.93 KiB) Viewed 12375 times


rIMG_4130 empty space.JPG
Another view, the cables make it look more cluttered than it is. See the fuel line resting right on the intake?
rIMG_4130 empty space.JPG (242.64 KiB) Viewed 12375 times


sIMG_4109 empty space.JPG
from the drivers side rear. The transaxle is in the lower right of this picture, with the starter painted blue above it. Top center, you can see the passenger side of the frame rail, with the roll bar support above, and the “V” of the torsion bar support below. The flange of the gas tank rested on the top of the “V” of the torsion bar support. Upper left, the assorted cables coming out of the body.
sIMG_4109 empty space.JPG (183.76 KiB) Viewed 12375 times


t3IMG_4110 empty space.JPG
Looking towards the body from behind, with the jack holding it up. The bulge for the ICE battery is upper left.
t3IMG_4110 empty space.JPG (183.08 KiB) Viewed 12375 times


uIMG_4122 empty space.JPG
Looking towards the drivers side from the passenger side. In the center of the picture you see the inside of the driver’s side roll bar support, above the “V” of the torsion bar/gas tank support.
uIMG_4122 empty space.JPG (213.13 KiB) Viewed 12375 times

I want to fit a 7s3p and a 27s3p module into the 36.35” space where the gas tank was. The 7s a123 module is 8 9/16” long, and the 28s module is 27.75” long (both are 9 5/8” tall and 6.50” deep), which would make them 1/8” too long for the space and leave no room for cabling. However, if I turn the 7s module sideways it uses 6.5” in that dimension instead of 8 9/16”, the pack becomes 34.25” wide, so I have 2” left for cables and the walls of the battery box.

However, turning the 7s module sideways makes the pack 2” deeper, so I can’t push it as far up into the peak behind the seats as I hoped, which in turn crowds the other two 7s modules that go underneath.

wIMG_4089 center plate.JPG
center cover and box for the pedal assembly weigh 9.8lbs
wIMG_4089 center plate.JPG (87.49 KiB) Viewed 12375 times


wIMG_4090 pedals.JPG
the pedal assembly weighs 4.8lbs
wIMG_4090 pedals.JPG (118.07 KiB) Viewed 12375 times


wIMG_4091 shift rod.JPG
shift rod and collar weigh 1.6lbs
wIMG_4091 shift rod.JPG (92.83 KiB) Viewed 12375 times


wIMG_4097 Pb batt.JPG
Pb battery weighs 28.8lbs.
wIMG_4097 Pb batt.JPG (86.97 KiB) Viewed 12375 times


wIMG_4099 u hooks.JPG
U bolts weigh 1lb each, 2lbs for the pair. The “U” part holds the torsion bar against the support, and the bolts on top hold the gas tank to the support. I love the way so many parts of the tow’d serve multiple purposes.
wIMG_4099 u hooks.JPG (148.88 KiB) Viewed 12375 times


x2IMG_4105 gas tank diameter.JPG
The end of the Tow’d gas is 10.5” in diameter, but it sticks out 3/16” out from the body of the tank, which is 10.125” in diameter. Note the flange on the end of the gas tank, which is held down by the nuts on the u-bolts in the last picture. The fuel line and filter are still attached.
x2IMG_4105 gas tank diameter.JPG (153.12 KiB) Viewed 12375 times


x1IMG_4101 gas tank.JPG
The empty gas tank weighs 28.8lbs
x1IMG_4101 gas tank.JPG (143.98 KiB) Viewed 12375 times


z2IMG_4180 layout.JPG
This is a mock-up of the battery box’s main plate. It will have (2) clamps underneath that will secure it to the torsion bar, which is seen extending from the bottom left corner of the picture into the middle. I expect this plate to be 1/4” aluminum, and the upper /lower compartments to be 1/8” aluminum, welded and heat-treated. The a123 modules will be bolted to this main plate, via the mounting holes in the modules. Note the wide slot in the middle that the cables are passing through. I will need to fabricate and re-run the rear brake line through this slot, a new skill to learn.
z2IMG_4180 layout.JPG (172.31 KiB) Viewed 12375 times


z1IMG_4172 layout.JPG
I built cardboard mock-ups of the 28s and 7s packs. The 28s has blue tape, and is roughly where the gas tank was. The 7s is below that. I will have an upper compartment that loads a 28s and 7s from the back, and drivers/passenger side each will have a lower battery compartment that loads a 7s from below, with control cables running between them. The piece of cardboard between the upper/lower compartment will be the main plate shared by both compartments.
z1IMG_4172 layout.JPG (190.58 KiB) Viewed 12375 times
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby Tommy L » Tue Jul 09, 2013 9:44 pm

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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby fechter » Thu Jul 11, 2013 2:36 pm

I like your use of CAD (cardboard aided design) for the batteries.
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby oatnet » Sun Jul 14, 2013 5:13 pm

Welcome Tommy!

fechter wrote:I like your use of CAD (cardboard aided design) for the batteries.

Thanks Fechter!

I’ve been getting a lot of traction locally with the CAD pun. :D I thought I would be able to take measurements and use Computer Aided Design to sort it out, but Cardboard Aided Design turned out to be an essential part of the process. I built up a spreadsheet to sum the width of materials in each axis (ie wall 1/8”, gap 1.5”, removal strap 1/16”, battery 6.5”, removal strap 1/16”, gap 1/8”, wall 1/8”) so I could make sure I was keeping every element, and the space it requires. I used that data to to make dozens of designs on paper, a few of which survived long enough to be rendered in cardboard. Each cardboard design, once installed, highlighted features I would not have otherwise considered.

-JD


aIMG_4779.JPG
a) The boxes on the right side are the dummy 28s3p and 7s3p a123 modules I used. On the left side are the three battery box designs that made it to cardboard.

The box in front is the first design, which featured a thick main plate (the part laying flat on the ground) with an enclosure for the 28s on top, and 2 enclosures below the plate for the 7s (not pictured). Once it was in place I saw a way to build it lighter and more elegantly.
aIMG_4779.JPG (209.03 KiB) Viewed 12115 times



bIMG_4777.JPG
The box in the middle was my second design. The 7s batteries would go into the pods in the bottom, and the 28s into the upper box. The 28s Battery has to have its smallest dimension (6.5”) front to rear, so that it can fit as far as possible up into the peak between the drivers seat and rear trunk.

I was concerned about ground clearance, so I placed the 7s modules on their side so the 6.5” dimension ran top to bottom. The 8 9/16” dimension barely fit into the space front to rear, and the 9 5/8” dimension ran left to right. This configuration allowed me to run a bolt from the top, through the upper battery, through the lower battery, and secure it with a nut on the bottom. I planned on putting one of these bolts on each side.

However, this also meant the upper part of the box was 6.5”, and the lower part of the box was 8 9/16”, which was awkward. Once it was in the tow’d, I could see how cumbersome it was to fit the Faux a123 modules through the open back, let alone keep them there with the box tilted back on the same angle as the seats. I also realized that the open back left the pods underneath inadequately supported, and that I had enough ground clearance to put the 8 9/16” dimension top-to-bottom, so the upper and lower battery compartments could be the same 6.5” front-to-rear.
bIMG_4777.JPG (144.21 KiB) Viewed 12115 times



cIMG_4781.JPG
c) The box on the left/front is my current, and perhaps final, design. Note that because of the orientation of the modules, it is taller and skinnier than its predecessors. The 7s modules go into the pods in the bottom. A ¼” plate goes over them, and is bolted to the “bridge” in the middle.

While the design is far simpler, it gave me a few challenges as well.

First the bolts that secure the a123 modules to the box – with the 7s reoriented to fit this box, the bolt holes run front-to-rear, instead of top-to-bottom like the 28s. This not only means I use the same bolt to secure both modules, but the 7s module blocks the path of bolts going through the 28s. I resolved this by tapping threads into the holes in the ¼” plate, so the bolts can screw into it after passing through the lid and 28s module. I also went from 2 bolts to 4 bolts on the 28s module, because ¼” doesn’t allow for a lot of thread. I originally planned on a 3/8” plate, but reduced it to ¼” as part of an effort to keep height.

I just need (1) bolt on each of the 7s modules, passing through the front and the rear of the battery box.

Then the cable path was a problem– the thicker design of its predecessor left space for cables across the back, my new leaner design did not. Since I have 36” of space inside the frame, but the 28s module is just under 28”, I have a 4” gap on either side, which sits right over the 1.5” gap by the 7s module and its terminals – plenty of space.
cIMG_4781.JPG (198.17 KiB) Viewed 12115 times



dIMG_4780.JPG
Note that the “bridge” on the left design, is much wider than the middle design, which unfortunately pushes the 7s modules further from the axis of rotation, and makes the gap smaller on the terminal side of the module than I would like, but I’ll explain why I made this tradeoff in a few minutes.
dIMG_4780.JPG (87.76 KiB) Viewed 12115 times



eIMG_4783.JPG
Another shot. The main plate in the first design (left) extended out the back to hold the controller assembly, but once installed I realized I did not have enough room. In the middle, you can see how I tapered the box from the 8 9/16” width to the 6.5” width. On the right, you can see the inside of the bridge; the plate supporting the 28s will extend 7+” on either side.
eIMG_4783.JPG (191.81 KiB) Viewed 12115 times



fIMG_4774.JPG
The box design sitting on the towd, right above where it will be placed.
fIMG_4774.JPG (191.86 KiB) Viewed 12115 times



gIMG_4775.JPG
The box design sitting on the towd, right above where it will be placed.
gIMG_4775.JPG (166.01 KiB) Viewed 12115 times



hIMG_4794.JPG
The box design installed on the towd. It has space to rotate forward or backwards, so that it rests against the seats as shown here, or rests against the torsion bar assembly behind it. The previous design, with the 8 9/16” dimension front to rear, filled the entire space between the seats and the torsion bar.

Resting against the seats as pictured, moves the battery mass is as far forward as possible (VWs put too much mass in the back), gives the best ground clearance, and promotes good airflow off the bottom of the seats. However, it is far forward of the hard points on torsion bar, which makes it a challenge to support. Also, the seat cushions have bolts that go through the back, so in this position I would never be able to bolt cushions on again, they would have to float.
hIMG_4794.JPG (232.41 KiB) Viewed 12115 times



iIMG_4798.JPG
i) In this position, I have rotated it against the torsion bar, and I have a gap where I can place and access bolts for the seat cushions. Note you can see the bolts for the passenger seat in the upper area of this gap. Huh, there is a 7s module on the other side of the gap.
iIMG_4798.JPG (209.76 KiB) Viewed 12115 times



jIMG_4813.JPG
And now for the explanation I promised. Here, we are looking from the front of the car, towards the rear. The edge of the seats is in the top of the picture, with cables/wiring running front to rear. The horizontal pole is the actual torsion bar, and the “bridge” section of the cardboard model surrounds the back of the fork that supports the transaxle.

Try to isolate the dumbbell-shape of the transaxle support, where it was cut off from the VW pan (too far back IMO). I made the bridge just wide enough to clear this dumbbell, so the battery box could rest right against the transaxle, and get the best support possible. I had planned to design clamps that go around the torsion bar and connect to the battery box, but once the CAD was in place, I realized I could bolt the box directly to the sides of this dumbbell-shape, no clamps needed.
jIMG_4813.JPG (210.29 KiB) Viewed 12115 times



kIMG_4839.JPG
this is a shot of the bridge from the other side, looking at the back of the dumbbell shape. Right above the “55” mark on the box, I’ve added a ½” thick flange, flush with the inside of the bridge, so I can put a bolt through it and into the dumbbell. This is the first of (3) supports on each side.
kIMG_4839.JPG (228 KiB) Viewed 12115 times



lIMG_4833.JPG
This picture is also from the rear of the box, torsion bar on the bottom, and the frame’s torsion bar support on the right. There is a wink of silver on the torsion bar support – this is a bolt the PO added, as part of an extra brace for the torsion bar. I’m going put another ½” thick flange, flush with each side of the battery box, so I can use this bolt hole as a second of (3) supports. Once I locate the dumbbell flanges, I can drill straight through this bolt’s hole to locate a new hole on the battery box’s flange. I would not have thought of this without a cardboard mock up.

The third support is the flange that held the old gas tank, and I would love to have the battery box builder weld on a tab, but I can’t locate it precisely enough. Once I get the other bolts installed, I’ll line up some angle iron, and drill holes through it and the wall of the battery box; it won’t be as strong, but it will be precise.
lIMG_4833.JPG (163.44 KiB) Viewed 12115 times



mbox 7 front.png
With the CAD out of the way, I started on the CAD. I have a student copy of Autodesk Inventor that I puzzled through when I took Machine Tool Technology at a local community college. Unfortunately, it was just too inelegant and obtuse for me to make a design. Besides, I have an issue with Autodesk because they went all the way to the supreme court to block customers from re-selling their copy if they don’t want it anymore. As a result, once you have purchased their software, it has absolutely no value because you cannot resell it – I won’t invest in such a business model, and I don’t want to build up skills that would tie me to that business model.

I tried a few packages, until I landed on Sketchup, which I had seen a few folks here using. Three minutes into the first tutorial, I had all the skills needed to complete my design, whereas I have spent 30+ hours on Autodesk Inventor over the years, and bought a “dummies” guide, and couldn’t get anywhere.

Anyhow, this is the side of the battery box that faces the front of the car.
mbox 7 front.png (201.72 KiB) Viewed 12115 times



nbox 7 drivers rear.png
This is the side of the battery box that faces rear, from the drivers side. Note that the flanges on the outside are completely square, but the bottom of the flanges in the center is at 110 degree angle, to clear the torsion bar.
nbox 7 drivers rear.png (231.43 KiB) Viewed 12115 times



obox 7 passenger rear.png
Same from the passenger rear. Note that the flanges in the center span over and under the bridge to support it.
obox 7 passenger rear.png (245.24 KiB) Viewed 12115 times



Image
A shot from underneath


qbox 7 top.png
a look inside the box
qbox 7 top.png (177.88 KiB) Viewed 12115 times



rbox LID.png
the lid, upside down. I haven’t located holes for the 28s module’s (4) bolts.
rbox LID.png (29.25 KiB) Viewed 12115 times



sbox_plate.png
the middle plate. I haven’t located holes for the 28s module’s (4) bolts yet, or the holes for the bolts that will secure it to the bridge.
sbox_plate.png (18.81 KiB) Viewed 12115 times
Attachments
pbox 7 bottom.png
Last edited by oatnet on Sun Jul 14, 2013 5:20 pm, edited 1 time in total. View post history.
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby oatnet » Fri Aug 09, 2013 6:18 pm

I let the final battery box design percolate for a month, but when I didn't think of any additional modifications I realized it was time to have it made. I was planning on sending it to one of the custom aluminum box builders I've checked out online, but a freind pointed me to a local metal shop, Phillips Steel in Long Beach. Yes, I would pay sales tax, but save on shipping (cost and environmental impact), plus the sales tax and purchase cost both benefit my local economy. In addition, now I have established a relationship with a local metal shop for future projects, I know that if send them a sketchup diagram they can build it.

I pulled into their lot, right next to a red 1969 BMW 2002, which oddly has the "Carpool lane OK" stickers typically seen on Hybrids. I am on my lunch hour and rushed, but I peek under the rear bumper, and see no exhaust, but what looks like the bottom of a battery box... None of the guys inside knows anything about it, but they mention their Boss has an electric car - wonder if it is custom, or a Volt/Tesla/MiEv/Leaf/Fiskar. When I left, the red BMW was gone and I regretting in my rush I forgot to take pics, but I am pretty sure it is Einar Lorentzen's build (Click Here), looks just like it and he lives in Long Beach.

a_IMG_5870.JPG
Here is the box and lid as it sat at Phillip's Steel when I picked it up.
a_IMG_5870.JPG (177.34 KiB) Viewed 11688 times


Image
The lid is off, the center plate in front of it, with the cardboard mockup of an a123 28s3p factory module sitting in place.


c_IMG_5881.JPG
The 28s3p mockup removed, you can see the 7s3p mockup in one of the legs of the box.
c_IMG_5881.JPG (179.05 KiB) Viewed 11688 times




As mentioned earlier, the towd has a bug tranny, but my adaptor is for a bus tranny, so I need a different adaptor kit or a custom flywheel. The Gland nut that secures the flywheel is a pain to torque on or off, so I prefer the bus flywheel that is secured with (5) bolts. The problem is that the Gland nut holds the Pilot Bearing for a Bug's input shaft... And the solution was the T4-T1 custom flywheel from Kennedy Engineered Products, Inc (Click Here). They press-fit a T1 pilot bearing into a custom hole milled into a T4 flywheel for $230, plus I paid extra to have the flywheel lightened to 12lbs, including milling off the ring gear (no mo starter!). They didn't skip a beat when I mentioned an EV, just asked me whether or not I needed the clutch surface, sounds like they are used to meeting EV builder needs.
Image
One side of the KEP flywheel, note the pilot bearing in the middle


e_IMG_5692.JPG
the other side of the KEP flywheel
e_IMG_5692.JPG (226.88 KiB) Viewed 11688 times



We lost a torsion spring on the roll-up door on our garage - the door fell with a hefty BANG when it went that convinced me to never walk under an opening garage door. I had to wheel the towd outside so the garage guy could replace the springs (he had to splice and torque the broken torsion bar to get the door open, and was pissed about that), so that gave me a chance to shoot a few pictures of the towd from new angles.

f_IMG_5670.JPG
From above, full of tools and parts, including the cardboard mockups of a123 Modules
f_IMG_5670.JPG (116.93 KiB) Viewed 11688 times


g_IMG_5660.JPG
I like the front suspension from this angle
g_IMG_5660.JPG (116.16 KiB) Viewed 11688 times


h_IMG_5646.JPG
yet another shot
h_IMG_5646.JPG (110.96 KiB) Viewed 11688 times


Duplicate pictures:
Attachments
b_IMG_5880.JPG
d_IMG_5693.JPG
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby litespeed » Fri Aug 09, 2013 8:04 pm

Looks excellent!

Tom
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby hillzofvalp » Sat Aug 10, 2013 12:29 am

that thing is going to be frickin' sweet. I like your range goal.. I would probably do more like 50 miles in case I took a wrong turn or something on an adventure.

I believe that the correct answer is an EV that plays to the strengths of electric power. Sizing the pack to a 35 mile range, and leveraging electric power's reduced infrastructure, yields an inexpensive lightweight vehicle, which allows for snappy acceleration and handling as well as a strong top end. I hope to demonstrate my belief with this build.


I think this range is Especially very great if it has high C-rate charge capable cells such as yours AND you have a frickin huge charger sitting around. I want to some day charge my 10kWh pack at 10kW with the option of 20kW.. though probably would need more like 15kWh to reach my 50 mile goal

Looks good.. wish I could have a drive when it's done.

edit: one other thing I'm not sure about: your battery placement. How much does your pack weigh? 250lbs? Best put that under the seat or something.
Last edited by hillzofvalp on Sat Aug 10, 2013 12:30 am, edited 1 time in total. View post history.
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby Martin A » Sat Aug 10, 2013 5:57 am

hillzofvalp wrote:
edit: one other thing I'm not sure about: your battery placement. How much does your pack weigh? 250lbs? Best put that under the seat or something.


+1

Having weight in the middle is not as good as having it low. Weight high up can give tricky on the limit handling. May be better sticking the batteries where the engine used to be.
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Re: 1,000lb "Elec-tow’d” Electric Tow’d Dune Buggy Build Thr

Postby oatnet » Sat Aug 10, 2013 9:40 am

Thanks for the good words guys. :D

Unfortunately there is not enough ground clearance to put the 166lb of batteries underneath the seats that are moulded into the body. :?

The battery box is going behind the seats, and ahead of the trunk. This puts 106lb 28s28p module in the exact same spot where the 11 gallon gas tank and lead-acid battery used to be, precisely maintaining the factory weight distribution, so no undesriable changes there. The pair of 30lb 7s3p modules are new masses to this space, directly underneath the 28s3p with their midpoint below the centerline of the wheels, lowering the COG.

The lightweight frame is also a concern when placing the battery box. In my design, the battery mass is tied directly to the wheels/Torsion Bar/Motor assembly, so there is no flex. If it were mounted under the seats, the sparse frame would be between the battery mass and the torsion bar mount, adding new loads to the frame that would make it twist and present undesirable handling characteristics.

With the ICE motor hanging off the back, the dune buggy had weight distribution something like 25% front 75% rear, because the motor is far behind the centerline of the rear wheel, effectively lifting the front end like a lever. This is great for riding dunes where you want the front wheels to float, not so much for the street. Every gram I can move forward improves weight distribution and consequently handling - I figure the lighter electric motor and battery box placement changes it to 42% front 58% rear. If I put the batteries where the motor was, I lose this benefit and street handling suffers.

I believe that the notion of paying for and hauling around the extra capacity for 'adventures' is at the root of the problem with EV design these days. This build is intended to show that if you dispel that myth, one can truly leverage the benefits of an EV - lighweight, cheap, simple, and effecient local transportation. The range from this 166lb pack is more than double what I travel 361 days a year on my electric motorcycle, probably triple if I dont stomp the throttle. The other 4 days I take one of my gas cars.

-JD

PS - Having weight high - which I hope you now see is not the case here - is NOT always bad. If this was a two wheeler, putting the weight higher means better handling and decreased stability, so location depends on whether you want performance or stability. I like commuter bikes with the weight low, but my fast bikes have the weight as high as I can get it.
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