pusher trailer build

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izpirkt
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Last seen: 8 years 4 months ago
Joined: Wednesday, January 12, 2011 - 05:49
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pusher trailer build

I'm finally getting started documenting my electric pusher trailer build. I'm doing this for a thesis project for a design degree. I want to promote the vast amount of information and expertise that are on DIY forums like this one.

Since this is for a design project, I am not just building something that I will be able to use, but want a product with production potential that anyone, with experience or not, can use. I need to design a product for a user with less technical knowledge and tools than you guys here. I am thinking that it needs to be like an accessory that did not significantly change the bike itself. Something that will come off of the bike when you want to ride it yourself. For instance, on a mountain bike you don't necessarily want a 10lb motor unsprung in the front wheel when you are out popping roots. On a road bike, you may want the assistance for a commute to work, but then remove it for some exercise or training on the weekends.

The result of this narrowing of focus leads me to an electric pusher trailer. Pusher trailers have been around for a long time as a concept, and there are an amazing number, variety, and quality of builds on this site. However, there are few electric trailers on the market. They have never really caught on, and I think this is due to a focus on the die-hard cyclist, and not the general public that own an underutilized bike.

As far as geometry, I have seen some that attach to the seat post, but this may not be the best geometry. The closer the connection of the trailer is to the contact patch of the rear wheel, the less disturbing the mass is to deal with. There are a couple of trailers I've seen that attached to the lugs on both sides, but they were long cargo trailers. This would make city/campus/parking more difficult. I am leaning toward an extrawheel trailer. I am going to combine the lug mounted style with a hub motor to take advantage of the dynamics, and short length, and simple implementation.

izpirkt
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Last seen: 8 years 4 months ago
Joined: Wednesday, January 12, 2011 - 05:49
Points: 4
Re: pusher trailer build

One of the members on the E-S forum mentioned that a short trailer may be "twichy" in use. The intention of my first build is to test the dynamics of the trailer. I expect to have to go through several rounds of re-building. I wonder if a collapsible trailer is possible. Extend to a long wheelbase while in use to smooth it out, and then collapse or fold to make fitting into a bike rack and locking up easier.

I have a pile of parts that I have scored from various sources. I found a 400w hub motor and controller:

I also just got a big pile of DeWalt batteries:

and for those batteries to work and not damage the BMS, I need to solder up some BMS interface boards from kfong on the E-S forum:

lbz5mc12
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Last seen: 8 years 1 month ago
Joined: Sunday, July 17, 2011 - 16:06
Points: 23
Re: pusher trailer build

I was thinking of building a trailer by chopping the rear half of a bike off. This way you already have somewhere to mount the wheel and you can still mount a book carrier on it. The only problem I've run into is a way to clamp the trailer to my bike. I decided to try this because my ebike frame broke at the seat post and the hub motor is too wide to fit on any other bike frame. Another good point is that on this particular frame there is a built in mount for the battery. This would also keep the trailer from being wide and wouldn't affect your turn radius. Basically clamp it using a heavy duty two way gate hinge and some kind of extension arm. The hinge should have some kind of spring tension on it to keep the trailer from jackknifing your bike. Another idea would be to use one of those child tandem bikes that clamp on to the adult bike. You can find them on Amazon.com. Just strip all the unnecessary gear off the kid bike and the motor mounted in a smaller wheel would increase the torque.

Nehmo
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Last seen: 1 year 7 months ago
Joined: Wednesday, August 10, 2011 - 01:17
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Re: pusher trailer build

I also just got a big pile of DeWalt batteries:

What kind of chemistry are those batteries? Are they NiCds? Li-ion? And what V?

`~- Nehmo

gasdive
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Last seen: 7 years 9 months ago
Joined: Thursday, October 28, 2010 - 22:43
Points: 90
Re: pusher trailer build

DeWalt battery packs are "nanophosphate" from A123 systems. It used to be the only way to get hold of the cells was to break up DeWalt packs but they can be bought seperately now and can be quite a lot cheaper. http://stores.ebay.com.au/OMG-Battery

Jason
Blogging my Zero DS from day one http://zerods.blogspot.com/

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