Looking for a tadpole RWD drivetrain solution

[KrisWood]

Hi everyone. I'm trying to figure out a pedal / electric drivetrain for my tadpole project. I'm trying to keep costs down as low as possible so I'm using a treadmill motor I got for free off craigslist. Project thread is in the general discussion forum: http://endless-sphere.com/forums/viewtopic.php?f=3&t=19481

So here's a quick rundown:

• I cannot weld and have very little machining capability (the reason I'm working with wood in the first place)
• My motor according to the label it is a 120VDC Permanent Magnet motor, 2.25HP 6200RPM and 18 amps. I'll likely be running at 36v (648w) until such a time as I can afford more and lighter weight batteries. The maximum I can put through it and stay within legal limits for Oregon is 72v (6 x 12v) for 997.92w (1Kw is the legal limit) or ~1.338hp after calculating motor efficiency.
• I'd like to avoid buying any new components whatsoever.

Any ideas?

 

[recumpence]

Hey Man! I saw your thread on Bentrider! You will feel VERY welcome here, I promise you.

I am not 100% sure if I can be much help to you. I am at the other end of the spectrum (high-end stuff). However, I do much fabrication and am willing to lend some advice as I can. There are plenty of world-class fab guys here that can help you out as well.

Anyway, one innexpensive solution for drivetrain components are electric scooter parts. Their motors and controllers are relatively innexpensive. Also, I aplaud your efforts to stay within the legal limits. However, bear in mind, electric dtuff is really tough to limit specifically (power output wise). It is best to have a little extra power, and just limit your top speed to be legal.

Anyway, welcome!

Matt

 

[KrisWood]

Scooter parts might work if I'm able to find a dead one at a yard sale but I'm really trying to limit how much new stuff I buy.

Legal limits are more of a general guideline to me. I plan to have a three phase toggle switch on the controller:

• 1: Kill Switch
• 2: On Switch (legal limits configuration)
• 3: "Overdrive" Bypass switch

I plan on having a dashboard for controls that looks something akin to a WW2 bomber cockpit, full of toggle switches and meters for speedometer, odometer, power usage, watt output at the motor, and RPMs, and whatever else would be useful during testing (the production version will need less meters), none of the switches labeled of course. As long as I don't bypass the limiting circuits in front of a police officer I should be fine.

My question for this thread though pertains more to how can I connect the motor drive train to the rear wheel on the left side, or combine it with the pedal drive on the right? My best idea so far to connect a cog to the motor is to use a crank cog. the ones on my mountain bike for example use a few small bolts to connect each ring to the next. I could do something similar and tap bolt holes through a cog and the flywheel of the motor and bolt them together. No idea where the chain should go after that though!

By the way, Your high end projects are part of what inspired me on this project in the first place. Hopefully some day I'll be able to sell my own trikes for money to make the next ones, too

 

[Rassy]

Hi Kris,

There have been a lot of different examples of how to hook up a mid drive, and for mine I got ideas from many of them:
http://www.endless-sphere.com/forums/viewtopic.php?f=28&t=18606
In some ways, staying on the right side made my solution very simple, but without the internal geared hub it probably would not have worked. I am real happy with it.

My main reason for replying here, is there was no 'free lunch'. One example, I started by using a shimano freewheel on the motor. It only lasted 30 miles before it failed under power. I used a track cog (no freewheel) until I could purchase a new Eno freewheel (about $80). Even though it worked with the track cog, I wasn't happy with the drag from the motor when pedaling. I also tested the system without a freewheel on the crank, but again I wasn't happy with the system until adding the freewheel to the crank. This is also an Eno from Sick Bike Parts, so it wasn't cheap either.

Good luck with your project, however you hook it up.

 

[amberwolf]

I plan on having a dashboard for controls that looks something akin to a WW2 bomber cockpit, full of toggle switches and meters for speedometer, odometer, power usage, watt output at the motor, and RPMs, and whatever else would be useful during testing (the production version will need less meters), none of the switches labeled of course.

You could use part of something like one of these:

They should be available cheap in aircraft scrapyards up there. Parts of at least one of these will probably end up on my bike(s) eventually.

My question for this thread though pertains more to how can I connect the motor drive train to the rear wheel on the left side, or combine it with the pedal drive on the right?

My best recommendation is to do it similar to how I did on CrazyBike2, where the pedals up front and the motor (via any necessary reduction hardware) somewhere in the middle or rear both connect to the left side of a jackshaft whose rightside is the triple chainring for the bike's (trike's) regular drivetrain.

But this is going to require some fabrication, or possibly purchase of parts like a freewheeling crankset. It is possible to make such a thing; I started to do so but never got very far with it, partly from time issues, partly from lack of knowledge and equipment.

However, I have since found a way to put the freewheel on a jackshaft, if you could fasten on some bottom-bracket bearing cups to the left side of the jackshaft (a regular pedal shaft without the left pedal), you could thread on single-speed freewheels to those, and drive the rear wheel via motor and pedals thru those, while neither would backfeed the other.