Guru advice for super large rider

[John in CR]

Luke,
It would work on pool table flat, but that can never be the case due to driveways, etc.. Realistically he's looking at a total load of close to 900lbs, so getting him going on is where he'll use all the energy, and for cooling 15mph isn't much better than parked. The low desired speed means low voltage too to avoid riding around a high load low duty cycle, an inefficient heat generating prospect. I can't ever recommend a maybe it will work setup that's all but guaranteed to fail going up a long hill. Putting a motor with a chain or belt drive on the delta trike is so easy to implement under or behind a comfy seat, and it's guaranteed to work. Then you up the voltage and gear it down for a happier motor and a happier rider, so even on moderate inclines the system won't be stressed, because it will be able to generate the power and torque to do it. Also, MidMonster is an easier to fit diameter than common pancake hubbies.

BigRider,
While the system I'd recommend would have a peak power of several kw, that doesn't mean it will use that power all the time. You need something capable of that kind of power when the load demands it. At cruise where the load is low it will put out only the mid 100's of watts needed much of which will depend on your tires, but if you get on an incline of even just a 5% grade then you need over 1kw at the wheel just to maintain 10mph. A 10% grade requires 2kw for 10mph. Even though you don't want to go fast, you don't want to take a week to get up to speed. I'm not talking about acceleration like I have and being able to blast away from traffic when the light turns green, but you do want to get up to speed quickly and get through an intersection safely as well as not waiting for huge gaps in traffic to turn left. I promise that you'll enjoy zippy over sluggish, and gentle on the throttle will accelerate you slowly when you want. Also, when you are forced to a stop on an incline like in a parking garage or a driveway or wherever, you want confidence that the trike can get out of the hole and go.

I think everyone is underestimating the impact of your total load of 800-900lbs, and that's before putting a kid or two or a load of groceries or hardware in the back. Even with 3 common hubmotors, one in each wheel, each will see a load greater than the majority have on their ebikes. Even though 3 motors might work for your needs, I couldn't recommend it in good conscience, because it would be too great a load on the relatively small axles...maybe not when traveling in a straight line, but while turning a trike will put much more weight on the outside rear wheel. It's not just the axles either, because hubmotors aren't designed to take side loads, much less the side loads resulting from a 700lb rider. That will need to be a consideration in your wheel and hub selection. You'll need something designed for a light 4 wheeled vehicle, maybe a golf cart hub with a rim and tire for a trailer, or maybe you can take a rear end from an ATV and mate a differential from a large riding lawnmower or cart. That's the kind of stuff to plan out well before spending money, because you can't just slap bicycle stuff on there like normal size people can get away with on their trikes.

Sorry, the beginnings of a book-like post again, but your needs are atypical, but not too different from a trike build to put a family on, something brewing in the back of my mind for a couple of years.

John

 

[Mundo]

Interesting topic....what can a bi/tri/quad-cycle do?

http://www.worksmancycles.com/shopsite_sc/store/html/sur-jr.html

 

[docnjoj]

Unfortunately that surrey is not considered a bicycle in most places in the US. You can only have 2 or 3 wheels to be a bike.
otherDoc

 

[amberwolf]

I'd far rather you all trash my existing solidworks I spent the past few weekends on (practice! Next time will be faster!) than to build a bike that breaks constantly and endangers me and I've wasted a stupid amount of money and efforts on.

FWIW, before actually doing the work for computer based stuff, I highly recommend "napkin sketches". If you already have all the parts built in CAD, and are just placing them together in different configurations, CAD is faster. But if you're just working out some rough ideas and layout, and don't have all the parts built or you are not even sure what parts you're using, plain old pen or pencil sketches on scratchpaper can be a lot faster, and at least to me, more satisfying.

(I use Lightwave3D if I really want to build something in the computer, and while I'm no expert at it's use it serves well enough...but most of the time I draw it all up on paper first before I build the bits in teh computer, and it generally takes me less time that way...though I did lose a lot of designs and ideas in my house fire because of that, since they weren't "backed up" on mulitple media stored in variuos places like the LW stuff was).

 

[marty]

Others will disagree with me but I say forget about building a bicycle frame. Whenever I build something that I have never built before, I have to build a minimum of three prototypes before I get all the bugs out of it. By the time you are done designing and building you will be dead from obesity. Please don't be offended by this comment it is not my intent.

Do a collaboration with Workman - let them build the frame for you. These are industrial grade frames. Then put moped tires on it and so forth.

Worksman frames are heavy, and durable. Trust me that they are totally unsuitable for the problem at hand. They are designed to withstand harsh use and neglect, not huge forces.

I align the front end of my Worksman Adaptable trike by just taking the bars and pulling them to the side while sitting on the seat. I weigh less than half what the OP does.

As for what I'd recommend to the OP, well, a pedicab trike would not be a bad starting point. They are designed to take the weight, and they use simpler, more rugged components than a tadpole trike.

EDIT:

Note that normal bicycle cranks and pedals won't be safe at these loads. The chain and sprockets will likely wear out unusually quickly, but the pedals and cranks can simply break off and cause a crash or injury.

The saddle and seatpost will have to be special too. And possibly the handlebars.

Chalo do you work for a bicycle shop? BigRider do you have a credit card? Send Chalo a private message and buy a bike.

After you get electric bicycle number one you will be hooked. Then you can start working on electric bicycle number two.

 

[Chalo]

I will say this: If you think you can ride a two wheeler, it is possible to build a two wheeler that will carry you, no problem. It will need a completely custom made frame, and wheels built with fatbike and/or moto components. It would be best to use a chain drive from motor to wheel rather than a hub motor, just to preserve wheel integrity.

Getting a seat to work reliably might be the biggest challenge of that approach. I think it's a surmountable problem.

 

[BigRider]

teklektik: I think we got disconnected somewhere. I did chage to what you're talking about - mostly. Delta, dual / redundant drive / etc. No mid-drive. The most likely right now is mid-monster geared to direct drive the hub (or jackshaft as you're talking about - but in either case, will be independent and direct drive in some fashion. With freewheels. We're on the same page.

I think part of the disconnect is I have flipped flopped during the thread due to advice given - and that I'm still reading at nights to get more comfortable with the topics. I read for months before opening my mouth, but I'm still a noob .

Hadn't thought about a second motor. I'll have to think about that.


John in CR: Gotcha. That's about the only thing I could come up with, but without reading that whole thread I wasn't able to get the back story and just wanted to make sure.

On the cooling mods I'm guessing that opening the motor could impact it's water handling capability. In KS I can't guarantee that the weather won't change on me while I'm out.It's not all that often and I would ride under high chance of rain, but I want to be able to handle accidental rain, or more likely if I ride to work it sometimes rains in the afternoons and the bike would be outside at work. They're getting better each year at predicting rain here, but .... it's still KS .

There are no mega hills around me but it's not super flat. Sounds like this will work.

I think the long trips will have to wait until its' easy to walk a mile again . I was doing great on that at 550 .... so I know it's not THAT far away. Hrm. Well.


LFP/Luke: Not very steep. Accelleration enough to get moving at a reasonable pace is important. Like John said - getting across intersections safely.


John: Feel free to book-like post. I like the info. You've sold me on not even considering hub motors, even before this post of your's I'm reading now . Right now my back axle is looking like 1" dia and the front 15mm axle from a motorcycle . Unless I end up changing the front wheel or rear wheels.


amberwolf: I love doing CAD work. If I weren't an EE by trade I'd probably have gone ME . I totally don't mind starting over. And yes, I started with a green spiral pad and pen to work my ideas out before starting. I'd done a lot of reading and research before committing to CAD. Then I had the great idea to ask for advice . Just because it trashes my awesome current design it's going to save me from months of work to be very disappointed. I'm glad to trade that off.


marty: You know, I agree. But part of this is also the fun of learning and the fun of building. I'm trying to over-engineer this from the get-go so the first one provides some exercise. And being home-made if I don't like something about it (say the distace between the pedals) then I don't mind cutting it off and trying again. Given how frustrating my Cannondale Easy Rider was at 460 lbs (breaking all the time), I figure over engineer. Get a rolling chassis and see what breaks. Then keep refining. I'm planning to work on this now through spring. As soon as the temps fall slightly I'm going to be done w/ research phase and start fab phase.


Chalo: I really don't think a two wheeler will work for me. I need to be able to stop and rest and I expect to be going very slowly given the heart / lung capacity I have right now. The trike will also lend a lot towards just plain stability and ability to track straight while chugging away.

I plan to post pictures of the basic bike in CAD to get inputs before cutting metal. That'll probably take a couple weeks and I'll probably make it a build thread. And Chalo I would really like your opinions on it when I get it posted.



Thanks to all who continue to give input. I appreciate hearing it - even if I don't immediately agree .

 

[BigRider]

FWIW, these are the wheels I already bought and still plan to use .... till I'm convinced otherwise. They're stupid strong and have real bearings. Everyone is saying "Go small because they're stronger". Well, there's no chance in hell these aren't strong enough. And I think I can change the gearing enough to make up for the larger diameter wheels. If I need to do a dual stage gearing then so be it. Haven't done the math yet, but that's where I'm leaning.

I have three. I plan to get some pit-bike forks for the front like the green chopper monster bike and hang one in between those forks for the front of the delta trike (and stretched handlebars). Then one at each end of a 1" axle from these guys:
http://www.staton-inc.com/store/products/Differential_and_1_x_38_long_Axle_Model_141_D-179-0.html

Thinking the mid-monster to a jackshaft to the rear diff housing - high voltage, geared really low. Then put bike gear to pedals. Gearing everything to work. Yes I expect the bike gear to blow up, but it's free (old bike) and if it doesn't work I'll possibly go BMX single speed on it or even kart chain single speed for the pedals.

Pedals need to be on the order of 12" apart for my ham-hocks. So I'm thinking about a piece of 5/8" shafting with pillow blocks on the outer sides and then home-made cranks and pedals (e.g. severely oversized .

That's the thoughts anyway.

 

[teklektik]

Regarding the power required to drive this trike:

The plots below show no-pedal power requirements to propel the bike assuming the general aero drag of an upright commuter with twice the typical frontal area (just a WAG - no real statistics are available). Gross vehicle weight is set to 900lbs. The left plot shows LoadLines as found in the ebikes.ca simulator and the left shows the Wh/mi for those curves. There is some reduction in motor efficiency at very low rpms which is not represented here, but that roll-off due to throttling is relatively modest and with gearing appears at very low speeds in an uninteresting part of the curve (this is not the same as the more dramatic low rpm efficiency loss due to loading as with motor power curve in ebikes,ca simulator).


10% grades are included, but I'm thinking these may be rare in Kansas - or at least avoidable... In any case, these plots may give some feel for the impact of speed and grade on the trike. The Wh/mi plots can be folded into range estimates based on available battery capacity (Wh).

To get some notion of the power consumed to develop this power at the road, the plots below show the same curves with an overall drive efficiency of 72%. This is a guesstimate based on a mid-drive (motor/chain drive/diff) with a nominal 80% motor efficiency, two chains at 98% efficiency, and a differential with 94% efficiency (efficiency estimates may vary, but these don't seem too outlandish). This is a drive suggested in an earlier post.


Power-wise, these values seem manageable on the flat or several degrees of incline. Although suitable non-hub motors are likely available, as a basis for comparison, these power levels appear within the reach of available large hub motors if mounted up a la StokeMonkey (perhaps with upgraded sprocket bolted up to disk brake mount). Things look pretty good at 16mph on the flat and not unreasonable on even 5% incline at speeds around 10mph. The power to start out on an incline are beyond these simple calculations which lack specifics of gearing, wheel size, and a particular motor torque curve but John's remark about an available 'peak power of several kW' seems reasonable given a fixed gear ratio.

To help put these power requirements in perspective, to power an average 235lb MTN ebike at 30mph with 80% efficient motor requires about 1200W of battery power.

Anyhow - just some SWAGs to throw into the mix....

 

[teklektik]

A couple of other thoughts:

• The plots above use using a rolling resistance similar to that of a regular ebike with moderately wide grabby tires - not a knobby. It might have been better to crank this up and can do so and re-run the plots if you wish.
• Considering the load per wheel, traction is not going to be a problem so I think you should be looking at a fast road tread for your motorcycle tires to minimize the rolling resistance. Using tires with large blocky tread or knobs is going to just be throwing power away.
• Regarding the two motor idea. Normally I am very much opposed to dual motor recommendations that use different motors (generally one for the flats, one for hills) because of the control problems, terrible efficiency, and carrying the extra weight that is normally not in use. In this case however, you are looking at DD as the best available choice considering the power levels for cruising. Getaways are problematic for DD without huge amps and your case is particularly taxing. This makes me think the 'low gear' second motor may be worth considering with a secondary benefit of offering slow but workable 'limp home mode'.
  
  You might consider a MAC12 geared for a max speed of 6mph as something that would give tremendous torque and could bootstrap the DD into a reasonable working range even in very difficult situations. A MAC12 geared to these speeds would be extremely powerful and would be relatively Amp-thrifty. You could control the motors with a common throttle and a couple of Cycle Analyst V3s. The V3 on the MAC can be finagled to give some fairly good automatic control using standard features.
  • Take the V3 and compress the allowable input operator throttle range so it hits WOT at something like 30% of the operator throttle.
  • Rig it for Current Throttle.
  • Set the max speed for 6mph
  • Set fairly slow/mushy PowerGain and xxxRate settings.
  With the DD V3 configured normally with Current Throttle (some magic might be tried there, but for this example, we leave it alone), both motors will kick in off the line. The compressed throttle range for the MAC V3 will send it to WOT with very little throttle motion which should get the bike rolling without massive DD amps. As the bike passes 6mph, the MAC V3 will turn off the MAC power completely, leaving the bike to drive on the DD. When slowing down, below 6mph the MAC will spin up but slowly due to the low WGain/xxxxRate settings - this should engage without too much of a jerk and will take over as the DD efficiency is falling in the dumper.
  
  This is sort of a wacky idea, but your trike is already outside the box. I know Justin experimented with a similar dual motor with fancy controller setup on his Maker Faire setup, but he was using some fancy controllers to do the motor switch over instead of V3s. Same idea though and this would allow sizing the DD and controller to more modest capacities for more normal use instead of for worst case situations.
  

  So with the programmable ASI controllers we were able to set up the throttle mappings uniquely on each controller such that low throttle signals from the CA only drive the front motor. Then once the throttle signal is such that the front motor is putting out about 500-600 watts, the rear motor automatically kicks in as well to share the load, and at higher throttles still then the front motor stays maxed out while the rear keeps increasing. In Robbie's bike setup, the input throttle signal for the front controller starts at 1.2V and is full phase current at 2.5V, while the rear motor starts at 2.0V and achieves full phase current at 3.5V. The single throttle output signal from the V3 CA spans from 1.15V to 3.5V. In the 1.2V-2.0V range it is only modulating power to the front wheel, between 2.0-2.5V both front and rear motors are being driven with the rear eZee motor taking an increasing proportion of the load, and between 2.5V-3.0V the front hub power is maxed out, while the rear motor keeps increasing. The CA is oblivious to all of this and simply sees that higher throttle outputs results in more power, without being concerned with the distribution between front and rear drives.

  It's simple to rig a switch to ground out the MAC throttle wire a la 'CA V2 throttle override' to suppress MAC operation completely if desired.

Anyhow - just a little musing....

 

[BigRider]

Hi Teklektik. As usual you're full of great ideas / info. Thanks for both postings. I had stepped away a bit this weekend and was planning on thanking you for the data plots today .

I do have near slicks on the motorcycle tires.

I figure the midmonster, two controllers, CA, and battery pack are going to be in the 2K range. Shelling out for another independent drive is something I may consider if the first one can't cut the mustard and I'll design it in up front as far as space / battery / etc, but I'm pretty sure I'll be stretched thin all winter with the current needs . But it is an interesting idea. Though I'd proabably just throw a second throttle on the other handle. Make it a thumb lever - as backup / starting motor. Then use a nice twist throttle for the DD motor. Something like that.

I'm hoping a the moment that if I leave the bike in 1st gear I can ease it into a roll then apply DD throttle. If the bike gear doesn't blow up I know I have leg muscles to do that. But that'll have to wait till I'm ready to roll .

But I will design in a second motor / gearing. It's a very good idea.

 

[teklektik]

Sounds like a good plan. Looking forward to reading about this in your build thread as the story unfolds (hint hint)...

 

[BigRider]

Lol. I get the hint . I'll probably start it in a couple weeks - basically as I'm finishing up the CAD changes from this round of feedback (e.g. starting over .

I expect my build to literally take all winter. I'm just doing it on weekends or maybe an occasional evening - and have two kids and am a single dad . So .... can't totally ignore them ... though they're at the age where they're happy as hell if i just let them play minecraft and let them ignore me. (almost 9 yr old boy, 11.5 yr old girl).

 

[arkmundi]

http://myevergreenbiz.blogspot.com/2010/05/eccentric-eclectic-electric-evergreen.html

 

[mat h physics]

I've been waiting for you BigRider, have only checked ES a few times over the last few months. Lucky arkmundi posted when he did, caught my interest on the front page.

The trike is a great option, especially when it comes to weight. If you really like CAD and want an opportunity to design a unique piece of hardware that I have yet to find designed, consider ditching the complex chain drive all together. Should you choose a delta design, just look into the Zero Turn mower rear axle. We had a "Mud Bug" delta, and the primary way of steering was to brake the inside wheel. In addition 75-100% of a "bike's" breaking is in the front wheel, but you won't be at speeds where this will matter. You said 12" spacing for petals, this will accommodate a gear driven or variable displacement (dual input shafts, attach cranks) pump. Power assist would come from an "RC" driven pump that can be mounted anywhere. This simplifies throttle, as pressure would dictate motor rpm. Valving could establish a ratio of output power to pedal input. Regen braking would be highly efficient, over 90%. This would add more weight for high power storage, think of a well pump pressure storage tank(called hyd accumulators). The real challenge would be to design the 1st (that I know of) outrunner hydraulic motor, input pressure from a hollow shaft in one side and out the other. Tadpole will certainly need forks up front, or custom spindles to handle the turns. Rear wheel would be driven like mid drive using OTS http://www.northerntool.com/shop/tools/product_200625087_200625087 (look at press/rpm, it's overkill), and these same dive motors can be used as fixed pumps. Using different sizes to establish a ratio between master/slave units. If security was a concern, just put a ball valve in the supply line to the diving unit, no fluid no rear tire motion. The point is to replace the "transmission" by using infinitely variable fluid. You can even pedal backwards using the right setup. You could even have a lowrider drop suspension to get on the bike! :lol: If you got real complex, use a due input pump, mount an electric motor on one side and an ICE on the other.
http://youtu.be/kxloD174TJQ
Move away from round tubing, rectangular tubing like a superbike's main frame or even swing arm. Advantage is a function of modules of inertia, like an I Beam.
The frame could even hold pressure, but save that for later adv build.
Advance the modern cyclist in a new direction.

 

[Chalo]

Move away from round tubing, rectangular tubing like a superbike's main frame or even swing arm. Advantage is a function of modules of inertia, like an I Beam.

Round tubing is the best for torsion and for strength to weight ratio. An I-beam is no good at all for torsion, and a rectangular tube is in between the two.

Your hydraulic scheme sounds a lot like an engineering student team project and not at all like a practical vehicle for anyone, let alone someone with special requirements.

 

[marty]

Think you all thinking too much. What you are trying to build has already been built by others before.
http://cycle-space.com/introducing-the-slip-block/

I do understand that you all like the challenge of building stuff. I like the challenge of figuring out where to buy existing products. I think of it like hunting. I know nothing about where to buy electric pedicabs. Challenge you all to find the manufacturer of the FedEx bike in the picture above.

 

[arkmundi]

http://cycle-space.com/

I have to agree that there is a significant architectural component to making bikes & eBikes modus operandi for the urban dweller (which I am). Used to be that a single family dwelling with garage was the stuff of dreams. I see the shift, especially with the millennials towards small apartment made increasingly adequate to accommodate prime mode.

 

[Jonathan in Hiram]

Looking at the Grin simulator with 900 lbs onboard if you gear two 9C motors down so they will do about 15 mph on the flat running 72 V they will take that same 900 lbs up a 12% grade at 11+ mph without overheating. I used an 8" wheel diameter on this (to simulate gearing down a larger wheel) and moved the slider until the motor power was half the load (that simulates dual identical motors). If you need somewhat less climbing power you can set it up with a bigger wheel and get a higher cruise speed, a 10" diameter tire on the same setup for instance gives you a little over 17 mph cruise speed but climbing draws more amps from the battery and heats the motors faster.

 

[BigRider]

So apparently my notifications aren't working. I hadn't realized people had been posting on the thread. Notifications worked for a while.

I also figured out my weight was going to require something like 4000ish$ to do just the electrics. I wasn't really thrilled with that. Now we're talking 6K to finish a bike that MIGHT work..... but most likely would require that three revs to get right thing.

So I decided to just KISS. Go back to basics and just make a regular bike first. Make Rev 1 just muscle power and pedal around my boring old flat neighborhood. Then work on electrics for Mark 2. I am keeping part reuse in mind with the new version, but I'm mostly just sticking with the idea that never electric on rev 1.


Arkmundi: That's a helluva trike.

mat h physics: Dood. I'm an EE by trade. I'm fairly mechanically competent, but that steps so far out of my comfort zone as to be impossible . At least any time soon. I understand gears and chains. I think I'll stick with that for Rev 1

Jonathon in Hiram: Thanks for the sims. I think for now I'm out for electrics. It's an interesting idea. I have thought maybe going to a more traditional smaller version and just gearing it down to stump puller speeds. But if I stay in my neighborhood I don't really need anything at all.

 

[mat h physics]

BigRider, I take it you want something no one else has, for the most part. Was hoping you would recognize the cantilevered motors used OTS, they would make for solid wheel mounts on the front of a tadpole. Don't let it scare you, just basic plumbing. And like any circuit, hydraulics have logic functions just like electrical devices. There are even logic functions in hydraulics that don't even have an electrical counterpart. Yes, it will take some learning of new material, but this is why the opportunities are so vast for this product. The fact you have experience in EE is going to give you a head start in understanding the circuit functions. You want to build conventional first, go ahead, to upgrade to power assist is a matter of just adding a pump. For the price of chain components, you can buy a pedal pump, and it's not going to wear out due to your high torque output. Chains are SPECIFICALLY for saving weight, the friction factor is trivial as hydraulics are in the 98% eff range. Some hydraulic systems are considered 100% eff, but these are specific systems such as water locks to raise and lower boats. There are many hyd wheel motor designs available: http://youtu.be/27EwDHMFvSU
Many motorcycles can be found sporting hyd, here is a 2WD R1 superbike: http://youtu.be/5TrvXwoGKKU
Notice he says the pump and motor are the same.
These MC systems don't use energy recovery, due to the high energy speed brings. You don't have that problem. There are components that will raise pressure for KE storage in high pressure accumulators. Most systems use electrical controls: http://youtu.be/JsFcfudj3rE
Expand your understanding of energy control, if it were easy everyone would do it.
Take trains for example. They use diesel engines to turn generators to power motors. These are not perm magnet motors like bikes, they are designed for high torque. Even though the generators are not much higher than 50% eff, the energy is saved through steel wheels on steel rails. This is why your large motorcycle tire will not be used long, lots of friction. Everything from bobcats to bulldozers use hydraulics for high loads/torque.
Do yourself a favor and at least look into it. For all you know, the road less traveled may lead to a pedicab, food delivery chains want to buy in quantity.
Hydraulic system are very powerful/simple/efficient.

 

[John in CR]

Whoever was trying to sell you on $6k-ish was trying to rob you. $2k for everything but the trike is easy, and that includes an easy pathway to much better than 15mph. By "easy" I mean change the sprockets and the system still isn't stressed.

 

[Chalo]

Chains are SPECIFICALLY for saving weight, the friction factor is trivial as hydraulics are in the 98% eff range.

If this were true (it isn't), then you'd think that you'd be able to find hydraulic drive on some kind of vehicle where gross efficiency is a main criterion. But you can't. You only find hydraulic drive on earth movers, tractors, forklifts, etc., where other factors outweigh efficiency.

Why wouldn't train locomotives, for instance, be diesel-hydraulic instead of diesel-electric? I know the answer to that question. You evidently don't.

Here's a hint: Hydraulic friction losses rise exponentially with flow rate. Here's another hint: Pressure seals always drag, always.

 

[Soj]

@Marty: Here's one manufacturer of electric pedecabs:

http://www.coasterpedicab.com/

@OP - I think the folks at Lightfoot Cycles are your best bet. You need a custom build, and I'm pretty sure he's done builds for "super large riders" before.

 

[amberwolf]

So how did this project work out so far?