Bicycle Main Frame - part 2

I had two more layers to make for each bike to complete the main frame. For the top tube I needed to laminate all 8 layers. I kept the sawn, tapered pieces in order so maintain grain pattern integrity as much as possible. I used the same jig as before, pre-steaming, then once cool and close to shape, gluing them up. The final layer laid onto the core. I wanted the join lines to overlap the finger jonts as I thought this would help strengthen the joint. I also trimmed the core and fixed a separate piece where the head tube will fit (but forgot to take a pic).

bike outer layer

 

 

road bike final layer

 

 

 

 

 

 

 

 

 

 

 

 

 

I couldn't afford for the bike frame halves to be twisted in anyway, so when gluing on the last layer I decided to clamp the frame to my table saw, as I know this to be a machined flat surface. I clamped the top tube but used screws in the waste area of the down and seat tubes as I couldn't get clamps to reach. I repeated the process for the other halves. If all was good then I would be ready to try out my hollowing jig.

bicycle frame layer 3

The bicycle frame could be repositioned into my jig because of the index pegs. I flipped the jig over and used a 1" round nose router bit with a 27mm guide bush. I had drawn this out on my CAD drawings to make sure I ended up with a 5mm wall thickness. It was a bit scary to start cutting the material away, and not the most pleasant of jobs, but all seemed to work ok.

 

hollowing the bicycle

 

bike frames ready for sanding flat 

 

 

 

 

 

 

 

 

 

 

 

 

 

The Brown Oak was a very dense piece of wood, and consequently, very heavy. Even compared to similar 'normal' oak planks I had, the Brown Oak weighed a ton. Hollowing it out made the frame start to feel a lot lighter, which pleased me. It would never make a super light bike, but I hoped the oak would be beautiful, and now I'm closer to 60 than 50, my fastest days are behind me anyway, so who cares about a bit of weight? Once hollowed, I wanted to sand the matching faces as true as possible so I wouldn't need to force the halves together with lots of clamping pressure. To that end, I used my table saw bench again, as this is a heavy, machined flat, cast iron top. I fixed sheets of 80grit paper to the whole bench top using double sided tape, marked the bike frame face with red crayon and sanded them flat. Fortunately it didn't take too much sanding.

 

 

hollowed bike frame

sanding bike halves

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I Loosely clamped the two halves together to check they were reasonably true. After so much work this was the first time anything actually looked like it might become a bicycle frame! I had made and added a couple of extra sections to make the seat post extension. I used the same method, employing my jigs.

Maple bicycle frame clamped up

 

Brown oak bike frame clamped together

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I did some basic shaping of the outside of the frame with a roundover cutter in my router table. (No pics, sorry). I now wanted to make the stays and fit it into a frame alignment jig just to be sure all was ok. I set about making the stays and the alingnment jig.

© Christopher Thompson