Trailer hitch

Dawud · #1 (**permalink**) 08-30-2009, 09:00 PM

After all the parts fetching and the first tack welding I just realized something. I don't have a clue how to attach it to the seat post. This is going to be a pusher trailer. Any ideas? Pictures would be greatly appreciated. Thank you

geeksquid · #2 (**permalink**) 08-31-2009, 02:41 PM

Quote:

Originally Posted by Dawud

After all the parts fetching and the first tack welding I just realized something. I don't have a clue how to attach it to the seat post. This is going to be a pusher trailer. Any ideas? Pictures would be greatly appreciated. Thank you

There is more than one way of doing it, but first of all, it entirely depends on if your trailer is a two wheel or single wheel.

deacon · #3 (**permalink**) 08-31-2009, 05:00 PM

I made an electric push and attached it at two points down by the wheel to the bike frame. It seemed to work very nice except it has hard to make tight turns. It was very stable though,.

Dawud · #4 (**permalink**) 08-31-2009, 06:02 PM

Quote:

Originally Posted by geeksquid

There is more than one way of doing it, but first of all, it entirely depends on if your trailer is a two wheel or single wheel.

I was shooting for either a two or four wheeled trailer. The four wheeled trailer would be set for the front two wheels to pivot like an old wagon.

Quote:

Originally Posted by deacon

I made an electric push and attached it at two points down by the wheel to the bike frame. It seemed to work very nice except it has hard to make tight turns. It was very stable though,.

How exactly did you hook that one up that low. Tight turning isn't greatly important as this rig will be used for in-between city travel(Approx. 20 miles one way).

Dawud

denbecr · #5 (**permalink**) 09-01-2009, 02:52 AM

On a push trailer with 1 wheel (simplest, lightest, narrowest, cheapest, easiest to build) you want a u-joint type hitch that allows the trailer to turn and go over bumps but not to be able to flop over sideways. You want it to lean only when the bike leans.

electricbicycletrailer.com Open, then click "learn more". Here's the best design I've seen for a seatpost pusher trailer hitch for a single-wheel pusher. It's simple and strong. Like most seatpost hitches, your frame must be small enough for you to reach your pedals when enough seatpost is exposed to accommodate the hitch.

Look at the picture of the hitch at the bottom of the page, then watch the video at the top of the page. He removes the seatpost, inserts it through the hitch, then reinstalls the seatpost into the frame. The hitch is free to rotate on the seatpost to allow the trailer to turn. The hitch needs only a horizontal hingepin so the trailer can lift over bumps.
A quick release seatpost would be best for this hitch.
The seatpost part of the hitch should be made of wood or plastic which could be bored through with a spade bit. Metal would erode the seatpost unless complicated with bushings/bearings/sealed lubrication etc. The ideal substance for the seatpost block would be UHMW (ultra high molecular weight) polyethylene available as industrial surplus offcuts on eBay.

Below is my version of a hitch that works like a u-joint and adapts to a regular upright diamond frame bike or a recumbent. Click twice to enlarge text to legibility. If you have no need to accommodate a recumbent the yellow portion could be one piece. Two pieces are necessary for a recumbent seatback which can't be inserted through the hitch like a seatpost can.

If you insist on 2 or more trailer wheels, any simple hitch will do that flexes in all directions, so the bike can lean independently of the trailer. This could be a piece of tire sidewall wrapped around the seatpost and bolted together, then bolted to the tongue. You could use an air hose quick coupling or one of very many hitches from bike & motorcycle trailer plans you can Google or find with a search of this forum.

Dawud · #6 (**permalink**) 09-01-2009, 12:20 PM

Alright, I took apart my tack welds and ground it back to just metal stock for the frame. Attached are a few sketches of what I am shooting for now. The upright box on the trailer is the engine while the wire framed area next to it just shows where the sprocket/ belt drive will come off the engine. You have the drive shaft off the engine as well as a centrifugal clutch. The bar on the very back is a jack shaft running to sprockets on the outside of both wheels. The reason the engine is centered between the tires is because it is a heavy engine and I would like to keep as much weight off of the bicycle as possible. the cargo area in front of the tyres is 3.25' by 4'. I still haven't figured out yet how the trailer will hook to the bike, but I figured this will give you all an idea of what I am shooting for. It is mocked up with 20" wheels. The engine weighs 121 lbs.

Regards,
Dawud

deacon · #7 (**permalink**) 09-01-2009, 04:51 PM

this is my pusher build...

Kevlarr · #8 (**permalink**) 09-01-2009, 05:04 PM

Never built a pusher but something that works good for a pivot is a small U-joint off the steering shaft of a Japanese built vehicle. Go to your local junk yard and look for a Toyota or a Nissan pickup. Cut the steering shaft just above and below the joint. Grind town the splines on the shaft, drill out the splines on the joint, drill out the threads for the keeper bolt and put a small clevis pin in it's place. You'll have a quick release six axis joint for around $5.