Dimple Chain Stays Before Or After?
11-06-18, 06:32 PM
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Dimple Chain Stays Before Or After?
Do chain stays get dimpled for tire clearance before or after brazing to lugged BB shell?
11-06-18, 07:50 PM
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I think before is best, unless you forget and then after. Andy
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11-07-18, 06:07 AM
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Before is best. Dimpling bends the stay slightly, as you are effectively shortening the stay on the bent side, so it will pull the dropouts closer together.
11-07-18, 05:51 PM
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Ah haaa, thanks for the tip! Before it is. Next question: I have a short piece of hardened round stock. Does it need to be shaped into more of an airplane wing, or can it be used as is?
11-07-18, 07:38 PM
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If you are going to use it lengthwise, I would smooth the sharp edges on the ends. Whatever shape you use will be transferred to the stay and sharp edges are going to make a crease in the tube. You probably don't have a bunch of scrap tubes laying around, but it would be best to test it on some scrap first. You may want to get some mild steel tube from the home improvement store for testing purposes.
11-07-18, 07:43 PM
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Ideally you would want to shape the form as you'd like the resulting dimple to be. Of course there's some spring back in the stay and the dimple will only actually contact the form very close to the form's leading edge. The few forms I've made have been from about 1/4" and 3/8" thick pieces. They have had their leading edge ground to a rounded shape roughly equal to the piece's thickness (so the 3/8" form has rounded to about a roughly 3/16" radius at it's edge). To me more important is the long axis shape. The length also is rounded in a gradual slope. So the forms are like a blimp cut in half lengthwise. This way the ends of the dimple are gradual and there's no "edge" or surface mark of the end of the form left on the stay. I did try one form that was more rounded along it's length but decided that the dimple was very short and thus the placement was rather critical. The current forms I use allow a less specific placement, or a wider range of ring sized in the future. On a triple ring set up it's the inner ring bolt heads that are the point of contact in the frame's I've done. Andy.
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