Homebuilt  Power Assist  and other Bike Trailers

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Power assist trailer version 1

This power assist trailer had multiple  dc output voltages,
110 vac and was also a source
of compressed air.

This trailer has it’s own page showing the original setup. 
Just click
HERE or on the picture.

Power assist trailer version 2

This trailer used a 2.5 hp engine I bought from Harbor Freight turning a 24v alternator.  It did work but  could not put out enough amperage to effectively run the trike without stalling the motor all the time.

Click on any pic for a large view

Power assist trailer version 3

This is the latest version that is now in use.  I took the 6.5 hp engine off the other big trailer  and the 24v alternator off the smaller one.

This setup works very well.


Click any pic for a larger view

                                                                                 Dump Truck Trailer

This trailer was built to move some dirt around in the yard. The funny part was my wife got some kids to shovel the dirt for her before I got done building the trailer. Oh well……

It was built on the frame of the big power assist trailer since I rarely used it.  It’s not fancy but it gets the job done and I can pull it around with my mobility scooter in the yard.

                                                                  Power pusher 49cc gas assist trailer Version 2

I built this trailer mainly because I got tired of never having enough range with the batteries on my electric assist trikes.    I got a 49cc mopped from someone for cheap due to the fact the bike had some problems and the owner didn’t want to bother with it.  The engine turned out to be OK but the frame of the bike was totally rusted out and not worth the trouble to repair.

 I have changed all the electrical parts, the carburetor and the starter motor and bendix on it simply because the bike was about 7-8 years old and I didn’t want problems. Moped parts are pretty cheap so it wan’t expensive to do so and it gives a little peace of mind.

The frame I built is made from bed-rail angle iron and some heavy walled steel tubing I had in my shop. It’s not a lightweight frame and is very solid for what it is.  I recycle just about everything I can and I had some heavy duty store quality wire shelving I made baskets from for the trailer.

I had a bit of trouble getting the throttle cable working properly at first as  I wanted to be able to disconnect the trailer from my trike. I came up with a simply was to connect and disconnect the cables but it turned out the return spring on the carburetor wasn’t quite strong enough to pull all the extra cable and return to idle when I released the throttle on the trike. 

 I tried a couple of different spring setups before I found one that worked well meaning the carb would idle and I could turn the thottle without needing a pipe wrench to do so!  It works pretty well now.  I added an extension mounted on the carburetor piece that holds the throttle cable that allowed me to add another cable in reverse with a small spring. It looks a little odd but it works well.

I also took off the vacuum operated fuel valve and used a simple manual valve to turn the fuel on and off.  The engine starts better and seems to run better too this way.

Only thing worth saving… engine and rear wheel      Building the trailer frame

simple plans       

Initial mounting and basket installation on frame.           Frame sandblasted and primed


Frame and baskets painted.                            Control panel and wiring done. On/Off  Start/KIll switches


Trailer mounted on trike with first throttle cable spring mess.    Final throttle problem fixed.


Trike with trailer mounted on the back.  The trike normally has a back deck and basket mounted on it.  I had it off for electrical wiring when I took this picture.

                                                                  Power pusher electric assist trailer Version 1

Side view

Hitch detail

Front view

This trailer was built for a friend of mine that kept commenting that he would like to have power assist on his bike. There was a slight problem though is he has a full suspension mountain type bike so the only motor setup I could think of that would be really available to him was to get a rear wheel with a built in motor. 

 Unfortunately he can’t afford the prices that are asked for those so I decided I would try a different direction. I had a few motors around the shop and an old rear section of a scooter.  I built the scooter section into a one wheel trailer that has a 36v 750w motor on it. The basket was pieced together from a few bits of wire shelving.

The tow bar that connects to the front of the trailer was made from the rear triangle of an old 26″ bike.
It pivots side to side at the front of the trailer and up and down where it mounts to the towing bikes rear axle with a couple of small plates that have nuts welded to them.  The front of the towbar also has 1/2″ nuts welded to them and 1/2″ bolts connect the bar to the bolts on the smal plates with about 1/8″ space between them. This allows the tow bar to swing up and down.

 I used car trailer light cables to connect the motor controller on the trailer to the throttle control on the bike so it can be disconnected easily when the trailer is not in use.

 It has more than enough power to push the bike at a good speed (15-18mph) and carry stuff like groceries in the trailer. He has been happy with it.

                                                            Click any pic for a larger view 

                                                          Grocery Trailer

View showing hitch

Rear View

Larger View

Hitch close-up

  This one uses bed frame angle iron as the base material and 1/2″ electrical conduit as the rails.
All the rails were brazed together top and bottom. The hitch triangle and forks were welded on. The bottom is 1/2″ plywood that has been painted with fiberglass resin on both sides and bolted and glued down with more resin to the bed rail frame. Actually all the bed rail parts, brazes and welds on the frame was painted with the resin first before being painted blue. – an extra rust preventative measure.

  The thing is painted blue instead of green to match the trike because that is what color paint I had on hand and needed the trailer done quickly.

  The forks that hold the scooter wheels are from 20″ bikes and were cut down to fit and then pieces were brazed on at the bottoms where the axles are mounted.  The pictures don’t show it but the forks are actually welded/brazed  for about 3″ on that side where it is connected to the trailer. There is another piece of bed rail that goes across the middle on the bottom and is also welded to the frame and the forks.  The forks are very solidly mounted with no give at all.

  1/4″ plastic rope was used to net the sides and help keep the weight down some. That type of rope does not like to be tied in that manner either and so I ended up using some wire ties on the top, middle, and bottom rows to keep everything in place. 

 It has held quite a bit of weight so far in use. It will easily hold an entire full size grocery cart quantity of food. 
                                                          Click any pic for a larger view