Treadmill powered pusher trailer for bike
 

I have a 1.25 hp permanent magnet DC motor from a treadmill that I'd like to use in a bicycle pusher trailer.

What is the best way to do this? Since I have the PWM circuit board from the treadmill, it seems that I could simply install a 12v battery and an 1000w inverter on the trailer, and a throttle potentiometer to the handlebar but I'd like a more elegant solution, partly because the controller has behaviors baked into it for treadmill use such as a delayed soft start, and partly because I'd like to skip the inverter.

If it's a 110v DC motor, then you can get a Kelly Controller, they are a cheap, Chinese made controller that tend to be under built and they self destruct of you push them at all to their limits, but they do make a 120v (18v to 136v) 100 amp (40 amps continues) speed controllers that they sell for around $300, so while I wouldn't normally suggest that a Kelly controller be used, their 100 amp controller would handle 16 peek HP for one minute, and 6.4HP continues, so it would be way more then you would need on a bicycle.
At that point you would just need a high voltage battery pack, a high voltage pack is going to give you slightly better range because of less line loss at the higher voltage.
Depending on your speed, it seems like bicycles tend to use 15 to 30 watt hours per mile, the faster you go the more energy you use, so lets say you get 10 12v 10amp hour lead acid gel batteries, that's 1,200 watt hours, lead acid gel batteries can handle slightly deeper discharges then flooded, so figure to 80% depleted you have around 30 mile range at 30 watt hours per mile, if you end up only using 20 watt hours per mile then you have a 50 mile range.
You could of course do some crude testing with your motor and a 12v or 24v battery pack and a simple switch to see how much push it gives you at a lower voltage to see if you could get away with running it at 72v or even 60v if you only want to go with 5 12v batteries, it would give you less speed, range and over all power, but it might be enough to fit your needs, or you might find it to be completely gutless, but it would let you find out without a huge investment in batteries and a speed controller.

Here's another company to consider for a controller - Alltrax Products Page

We are using a SPM 48400 for an EV project (36V w/Mars motor). Fully programmable for all sorts of functions. Good people to deal with and knowledgeable customer service if you have questions.


Jay

I have an Alltrax controller in my electric car and I really like it, but alltrax makes low voltage high amperage speed controllers, their highest voltage controller is 72v and 200 amps costing about $450 on Ebay for their 300 amp two minute rating, (200amp 5 minute, 125 amp 1 hour) speed controller, granted their specs say the 72v controller can handle up to 90v but my 48v speed controller says it can handle up to 60v and if I pull the charger off and try to drive I have to wait till my 48v pack rests for a few minutes and the voltage drops down to 56.4v before the controller will power up due to over voltage protection, so I suspect that the same will hold true for the 72v speed controller, that it would never turn on if you had say a 84v pack.

So if you want to try running a 110/120v motor at only 72v you might still get almost 1hp out of it and you are going to have a much better quality speed controller that is made in the USA, but if you want to get the max speed and power out of your motor that is possible you are going to need to be able to run it at 120v, your other option of course would be something like the Open ReVolt speed controller, 144v max and 500amps, but that would be a speed controller on a bicycle that is powerful enough to work on your car.

Testing your motor on a 12v and 24v battery pack without a speed controller, like I said is going to give you a better idea of what you can expect from that motor at lower voltages, you might find that it has plenty of power or you might find that at 12v you can stop it by grabbing the motor shaft.

When I read this thread title, I thought it was going to be about a person on a treadmill on a trailer, all of which was somehow powering the trailer to push the bike.

Nope.

That would be funny as hell to see a guy running on a treadmill to power the trailer to push the bike.
A bicycle built for two.. one rider , 1 runner.

I would mount the motor on the bike and tow the batteries. It just seems like you would have much better control / steering.

This.

Jeff, any deviation in the trailer's center of thrust, including differences of traction, will try to push the rear wheel off-track. Powering the cart with one motor would mean a differential is necessary. By the time all is said and done, you would be better off having built (or bought) a badass e-bike with additional battery capacity in the trailer, as Ecomodded suggested.

edit: I'm not saying it can't be done, but. You would need traction control of some sort to make it safe.

Is this known from experience or speculation?

The pusher trailers I've seen online are two wheelers with hitches mounted to the rear drop out area. I'd go for a frame mount motor. If you are planning for low speed torque, use a parallel battery connection. Is there an rpm rating on the motor?

I have seen one of these trailers with a purely DC system. You don't want to jam the throttle with the trailer cocked sideways with around 1000w of power, but otherwise there were no control issues. Gas powered trailers like this are very common.

Random day at work:
http://a7.sphotos.ak.fbcdn.net/hphot...86607991_n.jpg

I don't know it all, but I've got some experience on the subject of alignments. There are other considerations as well, like higher than normal tongue weight or length to counter the torque lifting the rear of the bike.

Perhaps all these forces are negligible, however. You cannot deny their existence.

Having had several one-wheel-drive go karts and such, and knowing King Midgets were also 1WD, my experience is that there may be a slightly noticeable effect upon "hard" (they had low power) acceleration; it was negligible and I'd do a 1WD vehicle again.

However, I've not ridden a bicycle powered by a trailer so that's why I asked. My intuition says the effect is probably noticeable yet manageable or even ignorable.

Aha! I had it stuck in my head that this was to be some sort of two-wheeled load-carrying device that hitches up. If this is just a one-wheel affair, then all is well. Just get it tracking straight and you're good to go.

If it were a more traditional design, like those little child carts you see, then things get a little more interesting.

I would imagine if it's to carry a heavy load of batteries a 2 wheel layout would be better? Or if it doesn't have many batteries 1 wheel should be OK.

1WD and having one wheel on one end are different things.

I had not settled on 2 wheels or one.
 

But I do mainly want it for carrying loads between workshops a couple of blocks apart. I think 2 wheels with one driven, hitched to the seatpost would be best if odd handling could be mitigated.

10 batteries? Ouch. Given the constraints of a bike, what is the most practical battery bank? UPS batteries?

I will do some 24v testing, maybe the inverter is a reasonable interim solution.

I don't see a problem with a single wheel trailer, people really like the Bob trailers that have a single wheel, but if you want a larger trailer like the Bikes At Work trailers and if you want it for hauling stuff then I think that a two wheeled trailer is going to be easier to load stuff on to.
As far as drive wheels, I see a few options, a single wheel drive on a two wheel trailer and design the hitch to be as low as possible so the trailer doesn't knock you over then just live with the effects and handling that it will cause, or you can do a two wheel drive trailer either with a differential from an old ridding lawn mower or go cart, you can buy one new from Northern Tool for $100 and it will weigh around 10-12 pounds, or you can put a free wheel on each drive wheel so the wheel that is going faster freewheels when you go around a corner, this is going to give you some odd handling and is not going to allow regen braking but it would be simple, cheap and light weight.
Another option that might give you the best handling is to mount the electric motor on the bicycle, put the batteries and controller in the trailer with a quick connect plug so you can leave the trailer behind if you want to ride the bike, then you'll be left with only the weight of the motor on the bike.

As for options for your high voltage battery pack, if you don't need a lot of range you could also go with lithium batteries, I have 4 lithium battery packs on my electric bike, they are the 36v (really are 33v) and can be wired up to give you 132v and those 2.6amp hour packs would give you around 10 to 15 miles of range and take up as much space as 4 bricks.