Electric Push Trailer

[Footie]

Since I got my electric mountain bike in June 07 my old 21-gear mountain bike has sat idle in the shed. This is starting to get to me, as this is a great bike. As a bit of a project I have been looking around for ways to add power to this bike although I am reluctant to spend £700 on a hub motor.
Also, I’m not looking to use it for commuting - it will be more of a play project.
One option would be to build something that pushed it like a powered trailer. I have look at several sites and at many different designs. The one I like the best for ease to make and simplicity is the Bidwell Bike Pusher. This is based on buying and dismantling an electric scooter and using the bits to make the pusher. This gives the builder everything they need including, throttle twist, battery and charger. So it’s a cheap way to get hold of the basics.

Bidwell Bike Pusher:* A Removeable Power Source for Your Bicycle..

I have found this possible donor electric scooter.

X300 Electric Scooter on eBay, also Other Electric Scooters, Electric Scooters, Scooters, Sporting Goods (end time 10-Feb-08 11:08:09 GMT)

Has anyone had any experience with these types of powered push trailers?
Are they any good?
And were I to go down this road, would a 300-watt motor do the job?
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The single wheel Bob Yak type have been used as pusher trailers. I am not sure how effective they were though. I wonder how stable the 2 wheel chainstay mounted type would be?.

[flecc]

There are two bike ones on the market. One uses the Currie motor inside the offside 20" wheel and has a flat platform for mounting anything or direct load carrying. That's about 400 watts, but not too satisfactory having one sided drive. Can't remember the maker at the moment.

The Dutch Cab Bike company make a smart one, but i don't know the power, Motor and battery in the bottom half, goods in the top. It's for bikes, BobYak fashion, as well as the trike attachment shown.

From these I'd conclude they're practical.
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[Footie]

Seems like someone else has recognised the gap in the market and are using Currie electro-drive to make powered trailers.

electro-drive Trailec :.07974 723996.:

£499 not cheap - could do it cheaper (under £250) if one did all the work one's self.
Is do-it-yourself worth the hassle? .... Have to think about it.
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[flecc]

The other Currie motored one I mentioned was £400, so DIY is probably worth it if you have the facilities.

I'm still not too happy about the one wheel lop-sided drive though, particularly as it's the right wheel driven. That will tend to push trailer and bike to steer left, which the UK drive-on-the-left road camber will make worse.
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[Footie]

Point taken flecc, about the tend to push the trailer and bike to the left.
Do you really think the push to the left would be that noticeable?
Of course if one were to reduce it all to a single wheel, then you have the worry that a single wheel (12.5" x 1.25 in this case) would be man enough to take all the weight?
Is there any way an amateur can work out the maximum weight a wheel should take?
Would be better than playing a guessing game and when it all collapses say "Oh dear, too much weight"
Anyone have a system to-work-it-out they could share?
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[flecc]

I doubt a 12.5" wheel will be up to much weight, as it probably hasn't got many spokes.

The sideways push will be like the side to side twisting that a badly balanced trailer with a long tail overhanging load gives a bike, tail wagging. It's a bit disconcerting as it throws the bike off balance into a bank and needs rebalancing with the body weight each time it occurs.

I've no idea how severe it will be with that motor, but it's quite powerful and will have loads of torque on a smaller trailer wheel. The main thing in practice would be to feed in the power gently to avoid a sudden surge in side load on the tow hitch.
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[Footie]

Thankyou for that flecc.
So, I would need to take care in use (avoid too much power too soon) but in theory it should be ok. Best to use the two wheels (three spokes per wheel) to take the loads - and like you say, good torque, being a small wheel.
Would be ideal for these wonderful Cornish hills “we av ere”
The idea of a DIY trailer is sounding better and better.
Have to think a bit more on it.
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[flecc]

I'm sure it will be better than this top heavy effort from someone on the International Human Powered Vehicle Association site:

Power Assist Trailer

Sort of conflicts with the human powered bit somehow.
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[kraeuterbutter]

hey.. what a interesting topic (for me)
iam currently trying to build also an push-trailer..

first: i have bought this one:
here a pictures:
bought it for 45 Euro
(there are a lot of this trailers at ebay)
its rated: 6kg empty weight
35kg payload possible
16" wheel

there are also very similar, but better quality trailers (but of course also a lot more money)
for example BOB-YAK: http://www.bikesandtrailers.com/bike..._2005_zoom.jpg
or the BOB-IBEX with suspension !
http://www.pedalkraft.de/_borders/ibex.jpg

so..
iam in the moment waiting that i get the trailer..
i hope that it will be possible to use parts (you can order single parts of the kit) of this kit to motorize the trailer:

but i want to use not the original Motor with the (i think not so quiet) planetary-gear
the unit has a free-spinning-unit, so no drag when driving without motorpower

i want to build my own motor for it...
(brushless outrunner, weight: about 300g light, ~300rpm/Volt
--> with 15V that would be around 4500rpm at the motor
with the 1:10 gearing of the chain i would not need any planetarygear
-> the wheel would spin with 450rpm -> ~500m per minute -> 30km/h topspeed -> benefit of the small 16" wheel (don´t need that high gearing)

for a gimick: i want it to be able to switch between triangle and star-configuration.. example:
20km/h with Star for hills -> 35km/h for flat when using in triangle-configuration

however:
for the above shown kit i need rims with 36 spokes !
have heard, that there are 16" wheels availabe with 36 spokes

without any payload i think the whole unit will be ~10kg including the batts..

question is: how much traction will the trailer have with only that few weight (some of the weight is even not carried by the 16" wheel but by the rear-wheel of the bike...)

i mean: on a steep hill, this 10kg trailer (with less than 10kg load on the 16"-wheel) will maybe loose traction and not be of great help.. we will see...

if it works out to be good, maybe i will invest in one of these (which looks much cooler):

Extrawheel – Fahrradanhänger :: Einradanhänger :: Anhänger

26" or 28" wheel... this with an hub-motor might be cool..

here a very nice Picture of it:
http://www.bobtec.de/img/Extrawheel-...r_FN-Trike.jpg

for more pictures of different electric push-trailers look here:
BobYak Fahrradanhänger mit Elektromotor


also nice and motorisable:
Oxtail Fahrradanhänger - Der Anhänger
(look in the gallery)

and more price: Weber Products Online. Fahrradanhänger | Kupplungen | Zubehör

there are already 2 pics of a motoriszed version:


more detailed picture of the drive unit: http://www.bobtec.de/img/monoporter-detail.jpg