Brake Bridge
For caliper brakes the brake bridge is critical. Best practice is to both epoxy and wrap the bridge in place. However as a road test I only used PC-7 Epoxy for securing the brake bridge with no wrap. I also used a scrap piece of walnut hardwood. Because of my woodworking I have many small cut-off pieces of hardwood which work perfect for small parts like the brake bridge and cable guides.
First off when shaping the brake bridge it is necessary to have a road caliper brake on hand. This helps with determining the correct height based on whether you have a long reach brake or not. On my current setup I run a 32c tire for gravel roads with a long reach caliper. Having a brake on hand also aids in centering the hole for the brake to attach to. There are adjustments like brake pad placement which help in locating the appropriate height in relation to the rim - having the pads be near center is a good idea, instead of being at one extreme or another. But in general since the bamboo seat stays are not going to be identical it is important to account for any asymmetry by appropriately placing the hole on the brake bridge. In some cases this might mean the hole for the brake bridge is "off-center" while being "centered" when in relation to the seat stays and chain stays. The rear wheel should already be centered to the bottom bracket, seat tube sleeve and head tube with your jig so by adjusting the seat stays and brake bridge one is fine tuning to maintain that alignment. When it comes to chain stay alignment it is important those come in contact with the bottom bracket by allowing equal distance on both sides of the rear wheel. It should be noted that I attach the brake bridge after the frame has already been built.
I have had no issues with only using PC-7 Epoxy for the brake bridge. I would not recommend using epoxy with no wrap but it is a good test of the integrity of the product. In fact I have found PC-7 to be extremely strong.
Calfee sells a brake bridge nut which is helpful. I have fashioned my own with plastic style bushings or simply using the hole in the hardwood itself etc. Using a lock nut helps to prevent the brake from loosening on rough roads - assuming one isn't using a standard road caliper bolt.
http://www.shopcalfee.com/brake-bridge-nut-for-caliper-brakes/
One last note whether one is using bamboo or a piece of hardwood for the brake bridge it is important that the part by shaped to have the same profile as the seat stays. This means the part is actually mechanically trapped between the stays. One installs it by sliding the part up until it reaches the appropriate location where it fits snug and cannot be pushed out. The epoxy is then holding the brake bridge at the appropriate location while the bamboo seat stay and brake bridge itself are maintaining strength during the braking process.
Again, I am confident of this method but best practice is to still wrap the brake bridge in place. Furthermore, it is not a bad idea to completely fill the brake bridge with epoxy when using a hollow piece of bamboo - this makes the bamboo a "solid part" while also securing the nut that Calfee sells for being epoxied.
The Process link
First off when shaping the brake bridge it is necessary to have a road caliper brake on hand. This helps with determining the correct height based on whether you have a long reach brake or not. On my current setup I run a 32c tire for gravel roads with a long reach caliper. Having a brake on hand also aids in centering the hole for the brake to attach to. There are adjustments like brake pad placement which help in locating the appropriate height in relation to the rim - having the pads be near center is a good idea, instead of being at one extreme or another. But in general since the bamboo seat stays are not going to be identical it is important to account for any asymmetry by appropriately placing the hole on the brake bridge. In some cases this might mean the hole for the brake bridge is "off-center" while being "centered" when in relation to the seat stays and chain stays. The rear wheel should already be centered to the bottom bracket, seat tube sleeve and head tube with your jig so by adjusting the seat stays and brake bridge one is fine tuning to maintain that alignment. When it comes to chain stay alignment it is important those come in contact with the bottom bracket by allowing equal distance on both sides of the rear wheel. It should be noted that I attach the brake bridge after the frame has already been built.
I have had no issues with only using PC-7 Epoxy for the brake bridge. I would not recommend using epoxy with no wrap but it is a good test of the integrity of the product. In fact I have found PC-7 to be extremely strong.
Calfee sells a brake bridge nut which is helpful. I have fashioned my own with plastic style bushings or simply using the hole in the hardwood itself etc. Using a lock nut helps to prevent the brake from loosening on rough roads - assuming one isn't using a standard road caliper bolt.
http://www.shopcalfee.com/brake-bridge-nut-for-caliper-brakes/
One last note whether one is using bamboo or a piece of hardwood for the brake bridge it is important that the part by shaped to have the same profile as the seat stays. This means the part is actually mechanically trapped between the stays. One installs it by sliding the part up until it reaches the appropriate location where it fits snug and cannot be pushed out. The epoxy is then holding the brake bridge at the appropriate location while the bamboo seat stay and brake bridge itself are maintaining strength during the braking process.
Again, I am confident of this method but best practice is to still wrap the brake bridge in place. Furthermore, it is not a bad idea to completely fill the brake bridge with epoxy when using a hollow piece of bamboo - this makes the bamboo a "solid part" while also securing the nut that Calfee sells for being epoxied.
The Process link
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