Project
Custom bicycle trailer for transporting RC models and more
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Published
May 03 2014 by FaTe
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Getting my models to the flight club and back is a bit of a pain without a car. I cycle to the club and have straps to carry bigger models but recently some of my builds have had fuselage sizes in excess of 1.3 meter. The idea is to build a trailer that is big enough to carry large models, simple to assemble and takes little storage space.

My trailer design allows the frame work to pull out upwards and the cover folds up, the tow bar pulls out of the trailer and disconnects from the tow bar on the bike. This leaves the trailer base as just 40CM thick when placed on its side which takes very little storage space. However when assembled it turns into 60*60CM with a height of 1.2 meters.
/media/trailer/1-trailer-base-axle
I'm using 8mm ply starting with the initial 60*60cm base to mount the trailer axle on. The axle bar itself is 80cm long for wheels and stoppers.
/media/trailer/2-60cm-square-30cm-deep
I added sides with support braces at each corner and bottom at different points to offset the stress when in use. Mikey happy demonstrating its his now.
/media/trailer/3-axle-fitted
Bottom view of the basic box frame.
/media/trailer/4-painted
I removed the axle and first sprayed the base in various colours I had left being honoust and then give it 2 coats of lacquer to seal the paint and weather proof it.
/media/trailer/5-framework
The frame work slots into wider diameter pieces I cut out and created custom brackets for using 15mm wide 3mm thick aluminium bent with hand tools only. These are very strong and don't move.
/media/trailer/6-removable
To allow the front frame section to slide in with the 2 rear support rods I had to create more custom brackets to suit the purpose.
/media/trailer/7-sbach-test
Testing to see how the Sbach fits being my biggest model (fuselage wise), fits super with loads of space around it left.
/media/trailer/8-custom-fittings
The fittings are all bolted through the frame and not clamps or such, it was easiest and its strong.
/media/trailer/9-frame-complete
Now all the framework is trimmed to size I can start to see the shape.
/media/trailer/10-removable-cover
For the cover I'm using plastic sheeting which has glass fibre embedded. To fit it all I'm simply using a decent 3M duck tape.
/media/trailer/11-tape-re-enforced
Continuing the tape around the access hole and sides etc.
/media/trailer/12-cover-finished
The cover piece is a bit of strange shape to fit the Sbach tail slightly sticking out. However I can make additional cover pieces in any size I want now, so I'm not limited by this one design.
/media/trailer/13-cover-fitted-demo
Now the entire top is in place which uses velcro all round the sides and top for a very secure seal.
/media/trailer/14-brace-bar
After some initial testing I didn't like how much stress was being applied on the front of the trailer. So I added an aluminium box frame piece that has a bracket bolted to the coupling at the front. This runs down the length of the trailer inside.
/media/trailer/15-brace-to-axle
Then from below you can see the box frame is also attached to the axle. This transfers forward motion stress from the coupling along the aluminium box frame and pulls up on the axle, removing almost all the stress from the wood frame itself.
/media/trailer/16-reflectors
There are no real "you must do this" laws on bikes past having night lights. However a bit common sense should tell you that a pair of cheap reflectors could avoid some idiot driver from clipping the back.
/media/trailer/17-foam-protection
Now to protect the models that sit inside. I'm using 3cm thick foam all around the sides but on the bottom its a double layer making it 6cm. I also have an extra 20*20cm cut out I can use to put under the Sbach nose cone making 9cm total.
/media/trailer/18-tow-bar-coupling
This is the correct coupling piece for a bike. It should be placed around the seat post however as I have a saddle frame that's not possible.. back to making more custom pieces!
/media/trailer/19-tow-bar-custom-fitting
So I bent a 3mm piece of aluminium so that the coupling can bolt in at the sides, the bracket then double bolts to the actual frame locking it in place.
/media/trailer/20-tow-arm-fitted
Finally its looking like a trailer. So you can see how the trailer bar slots into the trailer itself at the front and uses a bolt to lock it in. On the bike side the trailer coupling clips on and then has a screw on the side to prevent it coming out.
/media/trailer/21-fitted-to-bike
Now the saddle frame is on the bike and I drilled 2 holes through the clamp > through the seat post and back out of the other side. Then fitted 2 bolts cut to size through each eliminating any possible twist motion.
/media/trailer/22-additional-support-brackets
While the seat post with custom bolts on removed twisting the aluminium saddle frame still shifted 5MM left right at the back. When towing with additional stress it would translate into something braking.

So I used 10/6mm aluminium tubing to make my own 2 brackets that go from the bottom of the saddle frame to the chain rail holes on the bike frame. These push the aluminium frame up by about 4mm each side disallowing any movement at all, finally the frame is solid and test worthy.
I first took it out on the street which is all cobble road, an ideal "shake" test and stress test (especially for first try!). After I was convinced it was stable I carried the trailer inside and loaded my models in, carried the whole trailer back down stairs and just clamped it on.

I rode all the way to the flight club (4.5km away) which covers cobble road, tarmac, mud patches and grass (riding on to the field itself). I had no issues at all and after flying at the flight show returned home and simply reversed the process, carried trailer upstairs to unpack it. Removed the frame and carried the now empty small trailer to the shed until next time.

All in all for a home made trailer it does exactly what I want without compromise - the best way :)
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