I bent a brake lever on my Hygia SLP brakes . I'd already tried to got in contact with the local distributor about a bleed kit and olives. Disappointingly, I didn't hear anything back from them. Is it really too much to ask to reply to an email asking a simple question like "where can I buy a X, I live in Y?". The local distributor has set prices about 50% higher than what they sell for off fleabay so there really should be some margin for them to answer emails about where to buy their stuff.
Once I bent the brake lever back into shape I got thinking about making a stronger lever from carbon fiber.
Here's what I did:
Make a mold
The first step is to make a mold of the existing brake lever. I used the lever from the side that wasn't bent (the levers on the Hygia SLP and identical left to right). There are plenty of articles on the internet about how to make a fibreglass mold of a plug or part. Check those out for the details. The only real trick here was to use an appropriately bent aluminum plate to support the lever:
Make the lever using the mold
I get any pictures of this part of the process. You'd really need someone just operating the camera. Once the expoxy resin is mixed you want to move quickly and with sticky resin all over your gloves its not really conducive to getting the camera out.
For layup I used alternating layers of unidirectional and cross weave fibre in 25mm ribbon. There are 9 layers of carbon fiber in the lever blade. It is hugely over-built compared to the pressed aluminum original. The carbon fibre version is twice as thick.
I vacuum bagged the lever once layed up using nylon release cloth at the back of the lever.
Pop it out of the mold
Here's the original aluminum lever and the carbon fiber lever fresh from the mold. You can just see a corner of the fibreglass mold in the top right of the picture:
Machine in the holes and slots necessary for the pivot and brake actuator/adjuster:
Reassemble the brake with the new lever:
The original lever weighed 8 grams and the carbon fiber lever weighs the same. This may seem surprising but the carbon lever is about twice the volume of the aluminum lever. It is much stronger for the same weight.
Material quantities used
The 25mm carbon weave ribbon weighs 6.92g/m. The unidirectional carbon ribbon weighs 8.66g/m. In total I used 5 x 14cm of weave and 4 x 14cm of uni ribbon. So a total of 9.7g of carbon fibre. There was not too much excess trimmed, but I didn't weigh the off-cuts. Assuming 30% was trimmed then there is about 6-7g of carbon fibre in the lever and 1-2g of resin.
Glossy... (finish coat of gloss 2 part polyurethane)
On the bike:
For the next set of levers I am going to make a new mold. My first mold was pretty quick and dirty, just to check out the entire process and workflow. For the next mold I will use tooling gelcoat before beginning the fibreglass layers. Also, I will attempt to include in the mold the little slot in the front of the lever for the engagement point access. It was quite difficult to cleanly machine in this slot. Having at least its outline or a depression as part of the mold would produce a much neater end result.
I am also tempted to produce an ultra-light lever version. These would incorporate a layer of kevlar and less layers of carbon fiber in the lever blade. The kevlar will not add to the strength of the part but should hold things together in the event of a catastrophic failure.
Hygia are now making carbon fibre brake levers for the SLP. They are about 2g lighter than the aluminium levers.