Monowheel bike trailer for luggage



20.9.2005
During our recumbent meeting in Nivnice one friend appeared with a new trailer, Czech made imitation of BobYak.


I still have a tailbox from my old bike. During an accident last autumn (see Lehobrno) it destroyed front fender of a car and survived with some minor dammage, few scratches, hatch broke off. It was the very first fiberglass thing I've ever made and it's much overbuilt.
I decided to cut out useles parts from inside, blind some of the hatchtes on the sides, add a joint to the rear wheel of the bike and a wheel and use it as a trailer.
The most important is to get some experience with fiberglass. So I decided to make my own suspended fork and make the old shock absorber lying in the drawer finally useful. The same time I'm not going to complicate it more than necessary or go to some serious mathematics about it. After all, I'm not gonna riding it, just tow it, so the risk to my health in case of structural integrity failure is not so high:-).
This is all planning made, and the bill for the bike parts above (the book is just holding it flat, with no relationship to the trailer):

After measuring the tailbox I found out that trying to use bigger than 12" wheel would be rather difficult. Fortunately they had one 12" rim (60K), one tire (95K), a tube (55K) and cheap hub (95K).
To obtain so short spokes is difficult in Czech Republic and costom made are expensive and takes long time to get them. Making such wheel with 36 holes in the hub and 20 in the rim is not tampting idea to, so it's an opportunity to another exercise with fiberglass - tri-spoke wheel.
No such aerodynamic wheel like on Armstrongs road bike. I want just to attach cheap rim to cheap hub without modificating them. The result should be goodlooking functional wheel.
This photo shows old tailbox (right side) and the paper template for the spokes:

The template is just cut out of hard paper. To mak it more durable I put one layer of 80g/m2 glass fabric.
To avoid excentrity of the wheel I made sipmle wooden jig to hold the hub and the rim in exact position. The rim lies on three wooden cubes around, hub is screwed to the hole in the center. It's made of some piecese of wood lying in the shop:

I put the tamplate on the center of the hub, glued it to the in end from the inside to those holes fot spokes. Then I turned the hub this end up, put some layers of fiberglass on to it, so the tamplate became part of the hub. Then i turned it over again, bent the spokes to the rim and attachet them with same few layers again:

I use method from the website of Greg Kolodziejzyk from Canda (http://www.adventuresofgreg.com/hpvlog/). To prevent the fabric from moving around and to hold it where I want it I spray some contact cement on the place or on the fabric already there, when making more layers at once. You just have to be careful to put the resin everywhere and make it soak into all layers. I've already tried three layers at once without difficulties.
When the resin starts hardening I put it into the "oven". It's a box of some boots with a hairdryer and a temperature sensor inside. Regulation is manual - switching the dryer on and off and on and off and on... I don't have to wait to the next day, when heated to 50C it's cured in one ore two hours.

For now one side of the wheel is completed. I put the tire on and it looks good. It'll look even better when painted red and silver (whole trailer will be probably those colours):

The spokes are not visible when spining and it's like semitransparent:

To be continued...

26.9.2005
After finishing same three spokes on the other side I've sanded the whole thing a little, sprayed with filler, then red colour. Then I've played with a masking tape for three hours and then sprayed the result with a silver metalic colour. The manual says to let it harden for five days. I was impatient, so i heated it to 50C and gave it one day. I seems to be hard, so I've ripped of the tape and put on the tire. This is the result:


Now I have to clean the hub from some glue rest of the tape and than I'll probably try to refine few details using small paintbrush. Manual of that metallic colour recomends to put a layer of clear spray onto it and I'll do so.
To be continued...