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Post by oldroadietehachapi on Sept 27, 2021 4:47:26 GMT
I am starting on my projects and found the down tube to be slightly bent (about 2 mm with no kinking) on one of my frames. I see it as a challenge to fix it. I also would like to save a vintage silver soldered Reynolds 531 Trek.
Cheers Jim
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Post by brianbutler on Sept 27, 2021 11:34:52 GMT
The FFS-2 looks pretty versatile and might work, depending on the exact nature of the bend. For your quality of restorations it makes sense. I am a bottom feeder and would probably call a 2mm defect a battle scar and live with it. I completely agree with you about ignoring Sheldon Brown's frequent sledge hammer advice. I think he listened to too much Peter Paul & Mary.
Brian
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Post by wheelson on Sept 27, 2021 12:31:09 GMT
I am starting on my projects and found the down tube to be slightly bent (about 2 mm with no kinking) on one of my frames. I see it as a challenge to fix it. I also would like to save a vintage silver soldered Reynolds 531 Trek.
Cheers Jim
I have used both tools (or iterations thereof). Both work, the HTS-1 obviously would be ideal. There is a basic difference in the two, the HS-1 style can be used in the repair stand as shown as the pressure end points are both on the frame itself whereas the FFS-2 is more like a breaker bar and a sturdy bench vise will be needed. There was at one time a product called Lil Brute that was much like the HTS-1 but incorporated a car bumper jack-like device. The shop I worked at in the ‘60s-‘70s had one of those and I straightened countless frames and forks with it. Lil Brute also made a straighten-in-place lawnmower crankshaft straightener that saw extensive use at the shop. Best, John “wheelson”
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Post by brianbutler on Sept 27, 2021 12:55:25 GMT
I see RJ the Bike Guy has a video about the Li'l Brute fork straightener. At the end of his demonstration, he recommended against actually straightening a fork due to weakening, which sounds like good advice. I avoid any frames or forks that are obviously cracked or bent, or have stuck seatposts or stems. I have finally decided to scrap my Viscount Aerospace Pro frame with the cracked BB/seattube joint. I would just never be comfortable using it and I got more than the purchase price ($50) of parts from it so another bites the dust.
Brian
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Post by wheelson on Sept 27, 2021 13:25:04 GMT
I see RJ the Bike Guy has a video about the Li'l Brute fork straightener. At the end of his demonstration, he recommended against actually straightening a fork due to weakening, which sounds like good advice. I avoid any frames or forks that are obviously cracked or bent, or have stuck seatposts or stems. I have finally decided to scrap my Viscount Aerospace Pro frame with the cracked BB/seattube joint. I would just never be comfortable using it and I got more than the purchase price ($50) of parts from it so another bites the dust. Brian Most of the frames we straightened “back in the day” were heavy Schwinn-type with Ashtabula forks. I would have no problem riding these. Also consider that forks are sometimes recurved without question for a more appropriate rake. For Jim’s small amount of correction I also wouldn’t have a problem. Now if the frame or fork were bent such as to make the bike totally unrideable, or if the frame were made from super light tubing (Viscount??!!) then that’s a job I wouldn’t want to attempt. I once passed on a beautiful Trek 760 frame (Reynolds 531) to a co-member of another list as I just was not comfortable straightening it. He was a frame builder and had no problems doing so and passed it on to a friend. As with any repair, my standards as a mechanic have always been “would I ride this bike or would I put my child on it?” Of all the bike frames, forks, and lawnmower crankshafts we straightened back then, I don’t remember any reports of later failures. I guess we must have made some good decisions on where to draw the line. Best, John “wheelson”
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Post by oldroadietehachapi on Sept 27, 2021 14:00:26 GMT
Thanks for the input; very helpful indeed! Despite being only a couple of mm, the bend stands out to my eye. It appears to be even more noticeable in the photo below; I think the bit of primer makes it stand out. I suppose since a bend puts 2mm on one side, it is accompanied by another 2mm on the other. The eye is very good at seeing such things. As for me, I cannot look at the frame without seeing the defect. It may never be perfectly straight but perhaps I can work it to a point where it is not so noticeable. I am thinking of inventing my own solution; which will be fun. I enjoy things like this. Trek 710 1979 1 by Jim_Gude, on Flickr Ride Happy Jim
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Post by dracco on Sept 27, 2021 16:43:36 GMT
"Of all the bike frames, forks, and lawnmower crankshafts we straightened back then, I don’t remember any reports of later failures"
- Dead men tell no tales.
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Post by wheelson on Sept 27, 2021 16:59:24 GMT
"Of all the bike frames, forks, and lawnmower crankshafts we straightened back then, I don’t remember any reports of later failures" - Dead men tell no tales. But dead men’s lawyers do! Don’t forget I’m in the USA, probably the most sue happy spot on earth. Best, John “wheelson”
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Post by brianbutler on Sept 27, 2021 20:13:59 GMT
Despite being only a couple of mm, the bend stands out to my eye. I agree, it is noticeable. Part of it may be the shading or discoloration on the frame but no doubt it is bent. I did not mean to imply that nobody should do these fixes, just me. I don't have any way to tell if I'm doing it right or wrong. The main tubes are probably good candidates to unbend. I don't know about the stays, although I have spread them. I would not trust a repaired fork but it is replaceable anyway. For me, the bottom line is that I don't work on any frames that are valuable enough to fix - mid range vintage production bikes I can get for $50 complete, frames are often free.
Brian
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Post by oldroadietehachapi on Sept 28, 2021 17:51:51 GMT
I have invested in a Port-Power with a hydraulic puller. It is cheaper (and I think better) than a used HTS-1. My plan is to build small cradles for the down tube, mount two of them them to a very heavy duty outdoor work bench, and while gently pulling on the third cradle, pull the tube into place. You could probably make do with a come-along but I always wanted a Port-Power set and it is more precise. I also have a junk frame to practice on.
I am comfortable with straightening a steel tube so long as the correction is small and the tube is not wrinkled or kinked. Of course some strength maybe lost. Also the thinner the tube wall, the more likely for it to kink.
I will post my work as it progresses. Jim
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Post by wheelson on Sept 28, 2021 19:29:31 GMT
I have invested in a Port-Power with a hydraulic puller. It is cheaper (and I think better) than a used HTS-1. My plan is to build small cradles for the down tube, mount two of them them to a very heavy duty outdoor work bench, and while gently pulling on the third cradle, pull the tube into place. You could probably make do with a come-along but I always wanted a Port-Power set and it is more precise. I also have a junk frame to practice on. I am comfortable with straightening a steel tube so long as the correction is small and the tube is not wrinkled or kinked. Of course some strength maybe lost. Also the thinner the tube wall, the more likely for it to kink. I will post my work as it progresses. Jim Great plan, Jim. You always amaze me in that your solutions make good sense. I worked in an Engineering Mechanics Lab for over half of my career with our work centered on failure analysis of steel and carbide. Your analysis seems reasonable to me. Best, John “wheelson”
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Post by oldroadietehachapi on Sept 28, 2021 19:46:54 GMT
Thanks John! I have worked on steel frame (thin wall 4130) race cars and airplanes. I basically follow the same repair guidelines.
All the Best Jim
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Post by oldroadietehachapi on Sept 29, 2021 16:10:32 GMT
Broke out the calipers today. The tube in question is still round and distortion free. It is more like it is warped than bent. Excellent!
Jim
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Post by oldroadietehachapi on Sept 30, 2021 13:50:03 GMT
What did I learn? I think it highly unlikely that our half century old frames are still in alignment. I am not sure if they have to be perfect; if they were, I doubt they would stay that way for very long. I suspect that alignment is why supposedly identical frames, ride differently. I am amazed at how much force can be exerted on a steel frame. I am surprised that using a flat surface for a fulcrum does not bend the tubing. I think I want some alignment tools. I gained a lot of confidence on working with steel frames and now have little or no concern about cold setting drop out spacing. I doubt as much can be done with aluminum frames, hence steel is better. Carbon frames cannot be aligned. For a carbon frame to be properly aligned it would have to be built to a very high standard. Therefore, cheap carbon frames are at best, a bit junky.
Ride Happy Jim
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Post by wheelson on Sept 30, 2021 15:57:42 GMT
What did I learn? I think it highly unlikely that our half century old frames are still in alignment. I am not sure if they have to be perfect; if they were, I doubt they would stay that way for very long. I suspect that alignment is why supposedly identical frames, ride differently. I am amazed at how much force can be exerted on a steel frame. I am surprised that using a flat surface for a fulcrum does not bend the tubing. I think I want some alignment tools. I gained a lot of confidence on working with steel frames and now have little or no concern about cold setting drop out spacing. I doubt as much can be done with aluminum frames, hence steel is better. Carbon frames cannot be aligned. For a carbon frame to be properly aligned it would have to be built to a very high standard. Therefore, cheap carbon frames are at best, a bit junky.
Ride Happy Jim
Sounds good, Jim. Alignment is not horribly difficult. Those are good resource videos, as the author is a well-known frame builder in his own right. Aluminum for me would be a no-go. It’s always good to know in general what type of tubing you’re working with as some crazy light stuff can actually be flexed between thumb and forefinger. And always brace up points like rear brake mounting before spreading rear spacing so to not break anything loose. Common sense is always your best tool. Best, John “wheelson”
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