Plywood Rocket

Samlingsplatsen för oss som vill ligga!

Liggist.se

info@liggist.se

In the beginnig there was a man with a dream, to have a recumbent bicycle.

The dream was nurtured as a child, many ideas were born but all of them were put to rest for one reason or another.

But at last, the pressure became to great, something had to be done.

This is the story of the birth of the mighty PlywoodRocket!

 

The problem hasnt been the desire, energy, money or time, but the lack of space.

One can build a bike in ones kitchen, but that requires a VERY understanding and patient partner.

I simply didnt have the guts to take that chance.

 

But when i moved into my current apartment, i realized that i could use a wood workshop, a small basement shop thats for everyone to use, free of charge.

It includes some handtools and some powertools like a bandsaw and a lathe.

 

Some things are impossible to do without special tools or knowledge, therefore its a great resource to have good friends.

Without their help, this project would never have been possible.

 

Johan Carlsson, welder, painter, technical advisor.

Per Tjerngren, developmental aid and seat manufacturer

And last, but certainly not least, my dear father in law, Göran Holm, Smith, knowledge source, welder.

 

The first step was to find a donor bike with full suspension, tear it down and cut off the head tube.

 

The bike had been lying in my basement for years, unused and shamed by many years of neglect and abuse.

 

Step two was to produce a blueprint in full scale, old school.

We simply taped a sheet of paper onto the floor, placed the rear and front forks ontop of it and layed down on our side in the desired seating position and skectched the contours.

Shape and dimensions were ajusted as the blueprint was developed, but since this was our 3rd attemt at a wooden bike, we had most of the rough idea and measurements already completed.

 

The next step was to transfer the blueprint onto a template, a sheet of wood particle board, also called a chip board.

A set of holes were drilled to provide fixing points so repetitve acurracy could be achieved.

This template was then used to transfer the contours onto a sheet of plywood.

 

The fixing holes were also transfered to the plywood, this time to simplify the layup of the individual sheets.

 

The sheet of plywood were cut into 4 frame-sheets with a handheld powersaw, before the framesheets were screwed together thru the fixing holes and the outer contours were perfected with a handheld beltsander.

In retrospect i must admit that this step was the most time-concuming part of the project.

If and when i build another wood frame i will put much more time in creating the template to reduce the labour-consuming shaping of the individual sheets.

With a good enough template, i could cut the finished frame-sheet directly from a sheet of plywood using my handheld router.

This would only take 1/4th of the time i spent on this particular part of the project.

 

The outer sheets were given a tapered outer edge with a handheld router, the inner sheets were given a internal pocket structure to reduce weight.

I then placed the inner sheets ontop of the outer sheets and used the weight-reducing pockets to mill off the pocketed areas on the inside of the outer sheets, to further reduce weight.

The sheets are 15mm each and i removed about 4-5 mm on the pocket walls on the outer sheets.

 

I glued the frame togheter with a polyurethane glue that creates a foam where there is space, to fill up any uneven surfaces on the planes of the sheets.

You apply the glue on one part and water on the other, then press the two pieces together.

I used a wet rag.

The fixing holes provided the desired location of each piece and screw clamps provided the needed pressure for the frame to cure.

So there is no screws or nails that holds the frame togheter.

Some screws were used, but merely to fix other parts to the frame.

 

After curing, i used a belt sander and other handheld tools to complete the rounded edges around the frame exept where the seat is located, that area was kept square.

 

Finally the time cam to drill holes for the rear fork, bottom bracket and front fork.

 

The bottom bearing was screwed in place as it would have been if the frame was metal, the bearing cups screwed directly into the plywood.

This turned out to be sufficient to hold the bottom bearing.

Initially i only used one of the bearing cups, the frame provided the other one.

But this turned out to be less than optimal and the bottom bearing came loose at the unscrewed end.

 

The head tube needed a anchor to prevent lateral slip.

Glue alone was not sufficient to hold the headtube in place, it came loose while road testing.

So i had a small pin welded on the headtube that the frame rests on before i glued the headtube in place.

This prevents the headtube from slipping thru the hole.

 

The head tube angle and position is CRITICAL, it must be dead center, have the correct angle aswell as being perfectly straight, viewed from front.

Therefore i suggest that you use a drill jigg for this operation.

 

When the wood work finally came to an end (after about 5 weeks), it was time for surface treatment.

We decided to use a mahogony stain (oil based) to make the wood grain pop and then finish with a boat varnish as top layer.

This makes the wood water-proof aswell as creating a harder surface to reduce the risk of dents.

The bike is supposed to withstand rain and snow, not only sunlight..

 

The seat was eventually created out of 0.5mm aluminium sheet and fixed onto the frame with two rows of screws, about 18 screws were used.

The seat shape creates sufficient stiffness and the edges got folded and fitted with a rubber edge as found around car doors.

 

The seat is a bit flimsy on its outer edges, but feels sturdy enough for every day use.

The next seat version will adress this issue.

 

When the bike had recieved its paint job, got assembled and finished, it was time for a VERY exiting test run.

 

Eventually i fitted some extras, fenders, carrier rack, and a new, better front fork that provided better commuting experience.

 

This project hasnt been that expencive, i´ll try to sum up the cost here:

Currency is Swedish Krona,

1sek≈9 euro or 7usd

 

Bike Parts:

donorbike: 700:-

Front fork+head tube bearings, brake/gear cables: 550:-

Fenders+carrier rack: 170:-

Tires and tubes: 230:-

chain tube and fasteners: 180:-

chain (3pieces): 200:-

bottom bearing: 100:-

 

Wood stuff:

plywood and glue: 500:-

Paint and varnish: 350:-

seat cushion: 60:-

 

Tools:

Handheld router: 950:-

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Total cost: 3 990:-

Total build time: about 2 months, or aproximately 100-150 work hours.

 

Total pleasure: about 4.7googolplex.