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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[mk1]

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-trailers/images/YAK_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-E-Trailer_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

 

[Miles]

Yes, you can certainly get 16" rims with 36 holes.

For instance: 36h Sun CR18 16 x 1 3/8 (349) silver alloy rim wit

 

[kraeuterbutter]

thx...
wow.. i hope there is somewhere a cheaper source...
the rim alone costs more than the whole trailer sofar !!!

1.) the trailer does not need to carry more than 30kg.. so no ultra-strong rims are needed
2.) the torque from the motor will also be limited (not that much grip on the ground with light trailer) -> so no ultra-strong rim is needed

 

[Miles]

Alesa make a 16" (349 or 305) rim with 36 holes - that should be much cheaper.

 

[Footie]

It seems this idea may be re-kindled.
With the expected arrival of my new LiFePO4 battery I will have 3 12-volt batteries looking for a new home.
At the moment they may either go as spares for my campervan (for my solar panels) or be used in a push trailer project - can't decide.
I was hoping to get a spare battery box and make up a second battery for my ebike, but I have been informed that my battery box is no longer available, so had to scrap that idea
.

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

How's your push trailer going?
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[b4bob]

Hi I've got one of those trailers and use it to take house-hold rubbish to the skip. Part of the run is downhill (not dragging laden uphill if if can avoid it!) Note the pivot. I find as soon as the weight of the trailer gets out of line on a curve there is a distinct push at the rear as the thrust goes off centreline and the trailer tries to steer from the rear.. If you have power how are you going to keep the thrust in line, -lock out the pivot?

 

[Footie]

Hi I've got one of those trailers and use it to take house-hold rubbish to the skip. Part of the run is downhill (not dragging laden uphill if if can avoid it!) Note the pivot. I find as soon as the weight of the trailer gets out of line on a curve there is a distinct push at the rear as the thrust goes off centreline and the trailer tries to steer from the rear.. If you have power how are you going to keep the thrust in line, -lock out the pivot?

This is unknown territory for me, as I have never had a bicycle trailer.
flecc has already mentioned there may be a side-ways thrust from the trailer.
If locking out the pivot is necessary to stop the trailer taking control then I may have to do that.
All a bit "up in the air" untill I see and try the trailer out.
Thanks for the warning though
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[Footie]

Work-shifts and plenty of heavy rain have kept me from fitting and testing the Mule trailer until today.
Before going anywhere I had to attach it to the bike.
The trailer is supposed to fit onto the wheel nut on the left hand side of the back wheel but that would have meant disturbing the power cables going into the back wheel - no-way was I going to mess that up.
So I made a bracket (from a part off an old trailer tent) and bolted it to the frame.
I was then able to bolt the trailer pivot to the bracket, leaving the wheel undisturbed.

Mule Trailer on Flickr - Photo Sharing!

I’ve just got to remember the trailer makes the bike set-up very wide

It's great though
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[Bikemad]

I realise this is an old post, but I thought this would be the best place to post the following:



I came across the above 1000W powered trailer from Germany on eBay which has now got me thinking.

Here are the specifications:

1000watt Motor
24-36volt electronic control system
Proportional throttle control for Handle bars.*(Travel at any speed you wish. You have full control)
Battery not included leaving the option open to how much range is desired. The Higher the Ah rating of the battery the further you can travel.
30K/h on 24volts
45K/h on 36volts

It is also fitted with a Freewheel to reduce drag when the motor is not being used.

Now the interesting bit, the ad states that, "They also pass European laws and many Countries' Laws for maximum allowed Watts because the motor is not attached to the bike frame or wheels of the bicycle."

If this information is correct, presumably you could have a 10-20KW motor powering a trailer full of batteries and still legally use it as a pushbike?

Could this be a genuine loophole for getting around the UK 200Watt 15mph legal limits?

If anyone in the UK has any experience or details regarding the laws on motorised trailers, I would love to know the exact legal requirements.

Alan

 

[flecc]

The truthful bit might the lack of attachment to the bike, but that's very doubtful since the
trailer hitch attaches to the bike and the trailer can be interpreted as a power unit in the same way that a motor in a wheel is.

In any event, with that power available it is a motor vehicle subject to needing type approval anywhere in Europe, plus registration, number plates, VED and an appropriate driving licence.

 

[Bikemad]

So, if the trailer had a wireless throttle and was only attached to the rider via their belt etc. and not attached to the bike, I wonder how it would be interpreted by the law?

Alan