Modifying the Anchor for an Arai Brake
I am in the process of stripping the frame of a 1994 Burley duet. There is a lot of surface rust that mandates the stripping and refinishing. This bike was stored near the coast (east) and has suffered corrosion on all the parts. Fortunately the corrosions can be addresed without significant degridation in appearance for nearly all parts. All the parts are being disassembled, cleaned, lubed as needed and reassembled.
In fitting the rear wheel, I found the Arai brake drum anchor in what I would call a strange location. It is above the chain stay, rather than below. I was thinking of removing it and relocating it below. The reason is the arm of the Arai needs to be bent to align properly. It almost has to be S shaped to fit correctly without interference with the frame. Bending the arm can imact the shoe plate, which is a challenge. The picture shows the bare frame with the line of paint removed as a result of the interference from the arm. This also makes removal and installation of the rear wheel a bit of a challenge, forcing misalignment of the axle in the DO's. The picture is fuzzy becaue it was not the focal point and is a cropped portion.
Finally the question! Do you folks see any risk associated with moving the anchor to below the chain stay? The only one I can think of is that the joint will experince a tensile load instead of a compression load. If the weld is done correctly, I really don't believe this will be an issue. The frame is made of 4130.
Arai Brake anchor.jpg
Andrew R Stewart
I rode an first generation (serial #0069 ) Duet for about 20,000 miles, great bikes for the price but it did handle like a semi truck. The few handfuls that I sold from my old shop had happy teams too. But our tandem experience was much nicer with a long trail design that we got for our 10th anniversary (CoMotion).
There is no real difference in braking performance with the torque arm above or below the chain stay. But there is if the shoe backing plate is distorted. So the first solution is to bend just the torque (reaction) arm to fit. The second solution is to use a longer bolt that allows a spacer between the pack man (the braze on fitting that traps the bolt). I have used a bolt with lock nuts on either side of the arm to have the bolt's length and position fixed, one less thing to align during wheel re installation. The pack man located above the stay will have the arm's torque acting as a compression, forcing the braze on into the stay. If mounted below, as many brands do, will have the forces acting to open up the pack man's slot. But with a strong enough design this won't be a problem. Under the stay mounting does make wheel re installation a bit easier.
In the many tandems I've serviced (worked in a couple of tandem selling shops for many years) a problem I've seen but rarely heard a complaint about is the torque arm's bolt not being fully seated against the side of the pack man's slot that the arm wants to push against. If the bolt is above the slot's surface it will strike the surface with brake application. A few times i have heard a click/clunk as this happened, while on test rides. Over time an axle will create indentations in the drop out and tend to settle into one rotational position, if the torque arm is not rotationally positioned just so, it's bolt might not sit against the slot. My solution in these few cases is to use a hose clamp to pull the arm and it's bolt down and against the slot. I have also used this hose clamp to augment or serve as the arm's securement, when there was a weak or missing pack man. I have never seen a weak braze/weld but have seen the slot bent open. Andy.
After posting, I thought about the possibility of the slot opening. Clearly the design is for it's current location. I am not sure there would be enough braking force to open the slot. I imagine it would open from abuse. I did find a nearly new Arai assembly that I am going to use with a straight reaction arm. The arm has a offset in the face for strength which makes bending the arm difficult. I would rather not have to modify the arm at all and leave it straight. I know of a frame welder that can transfer the part from top to bottom for a reasonable fee and we can align it for best engagement to avoid too much slop!
As this is my first tandem, and my stoker is not a bike riding enthusiast, I think this will work out great. We can always upgrade and I expect to be able to break even or close, when and if we sell it. My stoker wants to use it to visit battle fields in Virginia and I want to get her on some of the trails around here.
Thanks for the response!
Have some vague mental image of them having the Arai hook on the bottom, at one time.
Being of the era that ATP was building the Frames , for Burly, (walking distance from the final assembly shop)
Alan the founder of Bike Friday was the owner of ATP, then took up the BiFri Making ,
when Burly started to make a conventional straight tube frame, in their Own Shop.
I worked with a gentleman who owned a single Burley. It was well made and he put a lot of hard miles on it. It is the only Burley single I have seen or known about. Don't know how many they made or over what period of time. I am aware of the Burley/BF connection. In fact I posted questions on BF NWT frame repair on this forum about a year ago: http://www.bikeforums.net/showthread...ighlight=Frame also talked about the fix on the folder forum: http://www.bikeforums.net/showthread...ighlight=Frame.