Saturday, September 12, 2009

"So sleep die ding" (That's how it tows)

Gert Swarts has taken the proverbial bull by the horns, his red "Gerrie Visser" is one busy bike. Gert looks after a number of properties in town, so being mobile is vital.

A week ago, Gert mentioned that he needed a trailer to haul his tools, compost and other work-related stuff around town. This clearly intersected with one of my needs (to make a bike trailer). I said to Gert that if he supplied two old steel bike frames (carbon doesn't weld so easily), I'd build him a trailer.

Anna's husband, Ampie generously donated another old steel frame from his scrap yard and , voila, we were in business.

After some not very fruitful internet research, I felt that I'd just follow my instinct and make the trailer. I'll describe this bit in detail, in case there are others who want to do the same. Unfortunately, I'm not good at documenting this kind of process, so the pics are all "after".

Part 1 : The Trailer

I took two old steel 26"(wheel size!) mtb frames (it helps if they are dimensionally similar, but that's not essential. The older, the better. (The older bikes have thicker steel sections which make for easier welding)

Strip the frames, re-cycle the bits.

Using two one-metre long pieces of 10mm threaded bar, fix the two frames alongside one another, this aids in alignment. I put one through the rear drop-outs and the other through the bottom bracket shell (Here I made large wooden washers)

Now it starts to look like something. You should have two frames, side by side, with a 10mm rod fixing them at the rear drop-outs and the BB. Don't worry about wheels at this stage.

Look at the inside chain stays, this is where you will attach the supports for the load bed. Depending on your design, you can probably remove the "front half" from the frames at this stage. Cut the top tube just in front of the seat tube and cut the down tube just in front of the BB.

The picture gets clearer, you now have two rear triangles which will form the wheel arches of your trailer. And not unsurprisingly, they will fit a standard 26" mtb wheel - what a bargain.

At this stage, you will need to attach the cross supports between the two inside chain stays. I welded them, but I'm sure one could also rivet or bolt them.

You will need to extend the load bed behind the axle in order to spread the load evenly over the axle. Again, welding and flat bar come to the rescue.

I then welded a length of flat bar between the tops of the two seat posts. All nice and rigid now.

Use a decent bit of steel for the goose-neck to attach the trailer to the bike (I used 20mm x 1,6mm square tube)

Old steel frames are much easier to work with (easier to weld) and can be bent to exacting tolerances. Remember, we are using two rear triangles and would ordinarily need to use two rear mtb wheels. Once you have welded the load bed together, it's a simple matter to bend the outer chain stays inwards (carefully) to bring the drop-out width to something approximating a front wheel (110mm, plus or minus half a brick). Because we are weight weenies, this is an important detail.

Put wheels (mtb slicks work a treat) on your trailer and suddenly you feel like this could actually work!

Part Two: The hitch

Gert wants a trailer to carry up to 25kg bags of compost, so I made the hitch accordingly. Gert's bike has mounting points for a rear rack, so I made up a rudimentary rear rack of flat bar and fabricated a simple hitch. So simple that I can't describe it, so look at the pictures please!

The idea is that the trailer is put at 90 degrees to the bike, the hitch is inserted and then off you go. The trailer and the bike have to be at 90 degrees to each other for the hitch to be removed.

This trailer can carry 100kg, although Gert will probably not carry much more than 25kg at a time.

I would appreciate any comments as I think this is the first of many trailers........

Trailer incomplete, rear view

Hitched to bike, almost complete


Close up of rack.

Close up of hitch

Hitch pin (12mm square bar)

Trailer at 90 deg. to bike

Hitch pin going in

Hitch pin in


1 comment:

  1. Wow - you've been incredibly busy down in the "dorp". Earth Angel indeed. Pity you couldn't be Pres. A lot more would get done.