Hi everyone, here is my first real post about my bike & newly made trailer.
Here is my cheapo S/H plain 26" Mountain Bike - sacrificial testbed. Notice the front forks are actually rear forks, for experimental (too noisy) front derailler drive.
I used rear forks off another 26" bike & welded them in same axle position as normal front forks, re-installed the derailler gears, and a small electric motor. It ran with a big gear reduction from motor to crank shaft, across the crank axle to standard shimano derailler gears - proof of concept, but it was so noisy, and the small motor was heavy; the whole front end was too heavy and noisy. I removed the derailler and motor, and keep rear wheel in there since it fits, and is a spare geared hub (in case). It makes the front a little heavy (not too bad), adds
about an inch of fork length, and looks chunky / gnarly. Future front wheel drive on it will be a small electric hub assistance next time, I think.
I'm lucky and have a small arc welder and angle grinder; I can fabricate thin steel to any shape, so sturdy adaptable fixable steel is my material of choice.
Using S/H 26" bikes and bits, I used 2 front forks to hold the trailer's wheels, since they're made for that, mudguards and brakes may be easily fitted. The home made drop-outs I saw in
the forums were looking a bit weak. With 26" capability forks, I can always use smaller wheels later if needed, eg. 16" or 12", or even 6" lawn mower / trolley wheels.
The frame was designed to become a bed, of sorts, with the width between the angled braces being just wide enough for me to lie between (I'm a bit skinny), while giving good wheel
rigidity, and not too wide a track. I used square seam welded 1.2mm or 1.6mm, painted steel tubing of 25mm sq., with 20mm sq. sliding pieces inside to extend lengths at front and rear if
needed. The draw bar extendable sub-frame is of 20mm sq. tubing.
The round holes of the cut off fork tops can be fitted with a surfboard / canoe carrier, umbrella, solar panel holder, fishing rod holder, canvas roof, etc. Any sort of brackets can be welded or bolted on the top or sides, just use imagination. The height of the fork tops poses little top heaviness, and can even protect the load, if kept small, like a roll bar.
The draw bar is a half of a 26" bike front fork with a large washer welded to the underside of the axle slot, for a smooth weight bearing surface on large nylon washers. I used these
plastic washers because I had a stack of them, some other slippery plastic may be better ("Oilulon" oil impregnated plastic ?). The fork is flattened out a bit at 90 deg. to the draw plate
washer, and hammered around in an arc to clear the bike's back wheel at more than 90 deg. turn, - made to fit with/using my special rear axle mounted bike trailer bracket (below), from
180mm behind bike axle. Top and bottom 2mm welded steel gussets hold the draw bar level & in line with the trailer frame, pulling down along the trailer's centreline , and it can then hold
a static 60 Kg on the draw bar alone, without permanently bending.
The front fork arm used is seam welded tubing, so over working it with a hammer may split the weld, making it weaker, and being thin cheap steel it is hard to weld, - blow holes. I also welded over the arm's original axle slot plate & lower fork join, because I don't trust the brazed fittings after my hammer & welding abuse.
Bike's-trailer mounts (in yellow paint) are both steel plate, with a reinforcing rib of 2mm X 10mm welded in a zig zag along most of the outside, to minimise sideways flex, and reinforce the
bends. Hose clamps hold short stabilising arms in place hard against the bike's forks, preventing the bracket plates from pivoting or twisting. The brackets fit the bike axle with a neat fit, no slot, and the end mount holes are both 180mm to rear from bike axle, and 50mm down. This position keeps trailer lateral movement from the bike to a minimum (Unlike seat stem mounts), and will support 60 Kg without lifting the front wheel up with leverage, as rear mounts do. The width distance between LH & RH bracket's end mount holes is 200mm, and the
bike can still be laid down (fall down) easily, without the trailerless brackets causing problems. Unless you have clown feet, your heels should be far from the brackets & clamps. Due to
the derailler gear pack width, the RH side plate has less bend in it than the LH side, keeping the wheel as centreline, and both bracket outers at 100mm from centre.
I used a car's engine mount bracket (which happened to be near enough to size), for the LH side prototype, of 4mm steel plate, down low for centre of gravity, and able to mount a
(shortened) rear bike kick stand to it, via a bolt almost directly under the axle & 50mm down; re-bending and cutting 50mm off the old stand's leg. The RH side fabricated from steel 40mm X 5mm flat bar, and using the same short stabilising arms, goes up and over the derailler to give it plenty of clearance, then down at the rear to the same level as the LH side, with both end pivot holes lining up perfectly together 180mm from the bike's axle, & 50mm down, together making a double pivot mount for a single wheeled trailer in the near future.
The LH side trailer bracket's coupling (used for this 2 wheeled trailer) is through bolted 40mm X 40mm X 1.6 (- 2mm) square steel tubing, with 1/4 " holes drilled on centrelines at 16mm
(not 20mm) from end/side, so 5/16" bolts can cross past eachother inside. Start with 1/4" holes and bolts until worn out, then drill out to 5/16" for bigger bolts when 1/4" is too worn out
& sloppy. The outer tube square is set up a little higher than the inner, allowing free horizontal movement to the tow arm. Large steel flat washers sandwich large nylon flat washers to
give silky smooth pivoting action in all planes, with no noise, rattle, or shimmy. Double nuts and nylock nuts hold it all together. A quick release trailer pin will be made one day, maybe.
Phone company used cable pulling rope is seen in the pictures wrapped around the frames for a makeshift platform. I sat very comfortably in the front half with the bike on its stand, on a
board so the stand doesn't sink in the lawn (needs a large washer or pad welded on); I could have easily dozed off there. With bamboo crossbeams tied on, a lightweight flat sleeping
platform could be made. I'm sure it could carry 150 - 200 Kg, or more than a regular bike anyway, if balanced on a solid floor plate, over or under the axles. A seat could be put at the
front, and a small utility bin or platform at the rear, or any combination.
With the trailer bolted on, almost all movement is enabled, from 90 deg. + turns, sharper than you can ride in tight circles, up, down, almost 360 deg rotation. When bike falls over, trailer
is still happy. It is all very solid, and a little bit heavy, but I can't see anything breaking in a hurry. If not for the trailer's curved tow arm, it could be rotated 180 deg, which would make
repairing flat tyres on bike or trailer easier, (but only with a straight draw bar).
[Ding ! idea - on 2 wheeled trailers, large flat washers & bolt through allowing 360 deg. rotation at or near the trailer / tow arm gusset joiner, so bike or trailer can go upside down for maintenance. But a weak point to break.] A couple of steel loops will be welded on trailer and bike, for a security chain, and possibly to help stop trailer fliping over big bumps.
If re-making the brackets again, I would use 3mm steel plate for both sides (I used 4mm & 5mm), with the fully welded reinforcing rib of 2mm X 10mm flat bar, and maybe a little more
extra reinforcing where needed at the bends, to resist twisting of the thinner plate.
For the single wheeled trailer setup, (yet to be made), the bike brackets will have two brass/bronze bushes (or something) which will vertically pivot (up & down only) a reversed 12" - 16" bike's rear fork (going around the back tyre). The second rearward vertical plane pivot (side to side only), of the semi-rigid link, joins on the front of a narrow single wheeled trailer.
Adjustable suspension is provided via a vehicle's rubber V belt take-up adjuster, or a lump of rubber (or something), a strong swing arm front pivot (removeable), and a single (or double
together side by side), 6" - 8" - 12" - 16" wheel on forks, possibly with a brake. Even a 26" wheel could work for very light duties, but probably ungainly & useless unless used for
saddlebags. A well braced & extendable draw bar, pulling a small bullet shaped, mid wheeled utility flat bed top, with no wheel hump, with extendable sides, and pulling out to ~ 2 metres
long, obviously a bed sized platform at full size. Or small box sides fold down to make a larger, wider flat bed.
Accessory ideas: fold down locking corner legs (angle iron/aluminium) for free trailer stability when off bike, removable tub, BBQ mesh, & BBQ plate floor sections, extendable base length
and width, occy strap loops/holes around edges, small underslung boxes near wheel, safety flag bracket, able to use larger or smaller wheel for replacement.
That's my trailer story so far; I hope it was as enlightening for you as it was fun for me.