Bicycle Stays

 

The bike's frame width was 52mm. I was going to fit a standard 68mm bottom bracket tube. Of the few wooden bicycle's I had seen, most maintained the 52mm width at the BB, splaying the chain stays toward the back wheel. However, I was conscious that the bottom bracket takes a good deal of stress. I had also heard a couple of stories of cracking around bottom brackets due to these stresses. I decided, therefore, that I wanted full support across the 68mm width. The downside, to making chainstays this wide is that I could no longer run straight stays to the rear wheel, as this risked the chainring or my heel fouling on the stays. More bending would be required. I drew my plans with the CAD software and printed templates to make myself another jig for bending the bike stays. Once again, I chose to do a trial with MDF as I had no spare Brown Oak left.

bike chain stay jig

I wanted to present the stay to the rear wheel at 90 degrees, so the stays had two bends. They were made up of three laminates. Using one of my original jigs, I cut a rebate in the bicycle frame and shaped the head of the chainstay to fit neatly. Using the MDF, the chain stay seemed to come out ok. I intended to run pegs through the stays and the whole frame to add strength - hence the two holes.

bike frame chain stay trial 

To ensure everything was looking ok I built myself a bike frame alignment jig, locating the position of the front and rear wheel axles and the bottom bracket. I fitted a Shimano bottom bracket into the frame and turned a steel bar to fit to act as a temporary locator. The frame halves were still only clamped together. The chainstays seemed to line up with the rear wheel and be the right width - 130mm, to accpet the rear wheel. I was happy so repeated the process using laminates of Brown Oak and Maple.

Bike frame alignment jig

 

I made up the final chainstays. I shaped the outer layer using my jig but left the other two layers oversize. I would trim them with a flush cutter afterwards. I employed the steam bending bag once again to pre-bend the forms. Once cooled and dry I would reclamp them with epoxy in the same jig.


bicycle chain stay steaming

 

bike chainstay blanks

 

 

 

 

 

 

 

 

 

 

 

 


The bike's seat stays would be bent in order to continue the same curve created by the top tube. This meant more tapered laminations. However, as the sections were getting thinner I felt I could bend these without having to first pre-bend. The seat stays would be made of three layers - sycamore sandwiched between brown oak. The laminates were tapered then glued up in the jig.

 

Bicycle seat stays

bike seat stays 

 

 

 

 

 

 

 

 

 

I planned to run internal cable routing through the frame and thought I would run the derailleur cable through the seat stay. To allow for this I would omit one of the laminates from the central core of the right hand stay. In order that I could still bend the laminates I wrapped one of them in clingfilm so that it could be in place for the glue up but easily extracted.

 

 

 

bicycle seat stay core

 

 bike seta stay core

 

 

 

 

 

 

 

 

 

 

 

 

© Christopher Thompson