Bubba's Experiment

I have wanted to do an electric bike for a while, but with the daughter in college, I don’t have much spare money. To keep from having to modify my bike, I went with a pusher design by using a trailer. Bought some inexpensive parts from TNC Scooters and started construction. Just to give it a try, I bought some cheep small tractor batteries and strapped them in. It was a thrill taking that first ride and a learning experience. I have no instrumentation on the bike, so I don’t know watts, amps, or speed.

In the back of my mind is a desire to ride to work. That would be a 30 mile round trip. I am thinking that a bike with a 40 mile range would be about right. Seem like that desire might take about 80 lbs of SLA batteries. Advice is welcomed.

What I learned:

• A pusher design seems to be workable.
• A fully loaded one wheel trailer is not stable enough.
• Three or more wheels are needed on the trailer.
• I really would like to have a lipo battery.
• I have a lot to learn about electric bikes.
• The bike slows down on hills a lot more then I expected.
• Using the brake light output from the controller to activate a trailer break might be a good idea.

Bubba

http://s332.photobucket.com/albums/m357/dontsendbubbamail/?action=view&current=IMG_4707.jpg

Looks like you do some quality work there, Bubba. :wink:

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Good effort! Don't have much experience with trailers but I saw a 3 wheel Trike that had a gas powered one wheel type "arm" type trailer that swung from the center of the axel to the ground.(At least from the looks of it when it went by). It was really noisy but I could see the gear and chain going to the weedwacker type engine.

Bubba, good job with the BOB trailer. In the last year and a half I have played around with several pusher trailers. all but one used the WE BD36 hub motors. The list of successes includes: A 26" two wheel two motor trailer pushing a mountain bike using a left side tongue attached near the bike hub; a 20" two wheel two motor trailer pushing a recumbent delta trike; and a 20" one wheel BOB trailer pushing a LWB recumbent bike.

With the two wheel trailers, both on the bike and the trike, you don't even know they are there, except for the surge of power when you hit the throttle. With the one wheel BOB trailer there is a tendancy for it to wag a little at speeds over 20 MPH, particularly when hitting a rough spot. The non-motorized BOB trailers will do this also. I don't really like to ride over 20 anyway, so no real problem.

The extra weight can be a problem when going down long hills, so I fitted both of my current trailers with plug brakes.

My biggest concern with any two wheel trailer is the extra width and multiple wheel tracks (makes it hard to miss obstacles) when riding on the edge of the highway.

As far as batteries and range, I am sold on the LiFePO4, except for the price. The range will depend on your speed, terrain, and how much you peddle. Using the recumbent bike and BOB trailer I have gone as far as 45 miles on 8AH when using 48V 12AH SLA. On my last little trip with the same setup but using 48V 20AH LiFePO4, I used 11 AH for 35 miles (more hills and I knew I had a better battery).

Good luck with your ride.

Edit: I just looked at your picture and re-read your comments. I would expect your trailer might be unstable with the load you have on it. On a couple of trips my brother found he had to repack his gear with all heavier items down low (non-motorized BOB) to keep it stable. Also, my BOB weighs about 75# with the SLA and 60# with the LiFePO4.

aww, cute.
It's a baby safe001.

Now that I got the first ride out of my system, it is time to make some changes. I am in the process of moving two of the batteries to either side of the wheel and just in front of the axle. This should make the handling a little better. If I still don’t like the handling, I may go with a two wheel design constructed out of wood. It doesn’t matter if the design is successful or practical because I just like to tinker. I will post some more pictures just as soon as I figure out how to embed in the note. I hate to say it, but I am blog challenged.

Bubba


P.S. Looks like I figured it out. I could not get the attachment to work on my first post. This is my not so special wheel. I machined a 1/8 inch Al plate on my CNC machine to clear the spokes and sit almost flush to the flange. The hub flange is at a bit of an angle, but I am not good enough to cut the slope. I also cut a circle out of some scrap so that the sprocket would be centered.

I moved two of the batteries out of the basket to just in front of the axle and lowered them. This made the handling a lot better, but not what I would want to use long term. Went for a ride using just the batteries and was able to go 25 miles at an average of 12 mph. It is geared low, so top speed was around 19 mph. The batteries are made for starting small garden tractors, so I am guessing that they are in the 20Ah range. Looks like two 36V 20 Ah Ping batteries would make this a usable rig.

The master link broke and the chain jumped off a few times. The chain seemed to want to jump off when the trailer wheel bounces on large bumps. It was a bit of a pain breaking and making the chain without a chain tool. I may try a chain tensioner to see if that stops the chain from jumping.

I am going to add a kick stand to the front of the trailer. Something is needed to stabilize the trailer when I stop and get off the bike. It will make putting the chain back on a lot easier.

As soon as I find the usb cable to my camera, I will post a picture.

Bubba

Looks really good for a first attempt. I like the trussed design.

Yes, batteries are everything. Lipos are BY FAR the most energy dense of any type easily available. My 48 volt 10AH pack weighs only 5 pounds with wiring. But, yes, Lipo batteries are dangerous. You need to be well aquainted with chargin them, you must have a very high end charger, and you must treat them with care. I have years of experience with them in RC and know exactly what I am doing. I have a hard time recommending Lipos to anyone other than a relative expert in this. But, Ping batts are a good (safer) option. They weigh more, but work well. You could also go with Nicads. But, your lead acid batteries may turn out to be fine if you can work out the handling.

I love the rig.

Matt

Did my electric power + human power test today. Tried to keep my speed down so that it would be a more apples to apples comparison to electric power alone. Went on one of my regular shorter bike loops that brought me back to the house at 25 miles. My 25 mile average was 14 mph. I then switched to a two mile loop, because I didn’t want to have to drag the dead batteries far. It was 90 deg so I use more electric power for the next 5 miles and the overall average was 14.4 mph. By this time, I was running out of water and my butt bone was saying stop. Switched to electric alone with WOT and got another 5 miles and the overall average was 14.8 mph.

Bubba

Man, I am really liking your rig. Very nice layout, great design, and good bends and welds.

Top notch.

Matt

Just to be clear, I bought the trailer. Wish I could take credit for it. Bought it from Bike Nashbar for $90. Don’t think I could have built it for less. My additions are all the angle iron and square tubing.

Bubba

Performed the WOT all electric power test yesterday. I went 25 miles with an average of 18 mph. The distance was the same as my 12 mph all electric power test. I am not sure what that might be telling me. I would have expected the distance to have been less.

Bubba

I have decided that my next step is to try a lipo battery. Did some bidding on ebay and won a 48v 20ah lipo battery from jimmywu66. He doesn’t seem to communicate as much or often as Ping does, so you are in the dark. People tend to start thinking the worst when they are given scant information. Some people seem to have had a good experience, so I am hopeful that I will too.

The next phase of my experiment will be to use an RC motor on my trailer. It is in the design phase. Right now it is looking like I will be using a 2000 w motor with a HV 85 amp controller, and one jackshaft. I really like the idea of using a roller clutch for freewheeling. When I am pedaling, I find that I am fighting the motor if I try to go faster then the motor can push and the freewheel will solve this. Number 25 sprockets and chain will be used. I hear that this may be a little noisy, but I can go to belts later.

I have a cnc machine that I built from mostly hardware store items. I don’t think it is accurate enough to cut a hole for a press fit. My cnc machine can cut Al, but I never have tied to cut steel. It will be use to cut some of the parts, but I think anyone with some basic tools will also be able to create a similar design. My goal is to obtain similar results as Scott and Mat without the fancy machining. Mat thinks that my idea of using a slip fit and red lock tight might work for attaching the sprocket to the clutch. I will also look for some industrial glue that will do a better job and is reasonable priced.

My 36v 1000 w brushed motor may go into another project. I saw an ice cream cart tricycle and thought that a similar design might work for a lead acid eBike for long distance commuting (30 miles round trip). Putting the lead acid batteries in a box over the front axle might make for a usable bike. The lead acid batteries on my one wheel trail make for poor handling. In my limited experience, I have not seen this style of design. It may be an indication that is just a bad idea. Has anyone seen this type of design implemented?


Bubba

dontsendbubbamail said:

Performed the WOT all electric power test yesterday. I went 25 miles with an average of 18 mph. The distance was the same as my 12 mph all electric power test. I am not sure what that might be telling me. I would have expected the distance to have been less.

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There are discussions in progress regarding controller losses (in the tech section)... very few controller losses are expected at WOT, if the current limit has not been reached (no PWM switching). That efficiency may reduce the expected losses from air-drag at the higher speed.

A CNC is on my to-do-list. Did you find plans online, or design your own? 8)

TylerDurden said:

A CNC is on my to-do-list. Did you find plans online, or design your own? 8)

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[/quote]

It was a little of both. Plans can be found at http://crankorgan.com/plans.htm. My Super Phoenix has a 2' X 2' cutting area and is good for wood and plastics. The Jester has a 6" X 6" cutting area and can cut Al. To make the Jester stronger, I took out the PVC from the design and replaced it with 1/2" brazed steel tubing and angle iron. The CNC zone has some free plans for a design that can cut wood and there are a lots of thread on other designs. The good thing is that there is free software out there for controlling the machine and doing Cad/Cam. Mat does the Cad/Cam by hand, but I prefer the software method.

Bubba

Safe,

I like your suggestions of using gears and adding NiCads. The handling of the trailer is being addressed by going with an RC motor and lipo battery. The good thing about using the trailer is that I can experiment without having to worry about how to hang stuff on the bike. There is lots of room to mount things and a more compact design can come later.

I do plan to circle around and try some of your suggestions. My preference is for upright bikes and I think a trike with the wheels in the front is appealing. The three points of support and the batteries being over the front axle would solve some handling problem. My wife is having balance problems, so this might be something she can ride. The 1000w brushed motor could use some gears. I envision the batteries be mounted low, the motor higher, and above it a jackshaft being driven through gears. The jackshaft would have a one way clutch on each end driving the wheels. It is just a thought in the back of my mind for now.

Bubba

I have been thinking about how to adjust chain tension. The picture show two methods.

1. If I let the flange bearing on the 54 tooth gear slide, I am not sure that enough meat is left to support the bearing. Between the mounting hole of the flange and the outer edge of the bearing is a smidge less the 1/4".

2. The other way is to use the 19 tooth idler, but that adds another part.

Bubba

Bubba,

I can PM you my number if you would like to talk. I am more than willing to give you any advice that is helpful to you.

Let me know if you would like to talk.

Matt

Matt,

Sound like a plan to me. I will take all the help I can get. My clocks are on EST.

Bubba

PM sent.

Glad to be of any help I can.

Matt

dontsendbubbamail said:

I have been thinking about how to adjust chain tension.

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Many setups move the motor to adjust: the motor is usually mounted on a plate that can slide fore/aft and be locked in position. That way your bearing keeps plenty of support.

Has anyone tried to use the 555 timer based servo tester in the link with a Magura® 5k Ohm Twist Throttle and an RC ESC?

http://www.drivecalc.de/circuits/Servotester.html

Bubba

dontsendbubbamail said:

. My preference is for upright bikes and I think a trike with the wheels in the front is appealing.

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I like the idea of the reverse trike myself Bubba, i have had a look about the net while back on designs to get a few ideas, the following are a few 'styles' that i found appealing and had elements i thought worth of replicating for an revers trike e-bike...(none are actually e-bikes and only one is a 'bicycle' were just gathered for ideas/inspiration )



Not an upright but still i thought a solid design.



and prolly my fav-->



[

Would LOVE to have a crack at a tilting design...if i can workout how it all goes together :-S



Might give you a few ideas anywayz...best of luck with the continued experimentation with the trailer/batteries/design etc

Kim