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Old 05-04-2022, 10:19 PM
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Default Acid Etch or Sand for Weight Reduction

You guys remember when they built the Thunderbolt drag cars, and they acid dipped the unit body to make it lighter?

I am going to bend steel some mild steel tubing for a bicycle, & the wall is a little heavier than ideal for my project. So I am considering, after I bend the tubing, I might acid etch it on the inside by repeated swabbing. It would be nice to knock off 0.025”. I’m afraid that is an awful lot to remove.

I might do some tests to see how long it takes with the acid that I have. Of course my goal is to have a uniform weight reduction of the tubing.

My other thought is that I could make a Roto-router sanding device and sand the inside of the tubing repeatedly until it is thin. Most of the tubing will not have sharp bends, but very gentle curves.

Guys who build racing machines are probably doing this stuff but I don’t have any clue about the whole business. All I know is the tube I want to use is too thick and if I could get it any thinner, I will probably not get a good bend.

Anyhow I already have the tubing that I’m going to use in hand, and I was hoping for some sage advice.

Also the acid etching could produce a huge quantity of fumes and I do live in suburbia so I don’t want to offend my neighbors interminably.
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Old 05-04-2022, 10:43 PM
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Fill tube with dry sand . You will be able to bend without kinking . Try it on a smaller piece of thinner material . .025 is a lot to etch or sand .
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Old 05-05-2022, 01:04 AM
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I believe when racing bikes were still made of steel that the best frames had the tubes drawn out. So they were cut short and stretched. The stretch would not be uniform, the ends would be thicker and stronger because that's where the joins and hence stress was.

Was half art, half engineering. Fell by the wayside when composite frames came to be.
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Old 05-05-2022, 09:10 AM
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Chemical milling is done on aluminum...
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Old 05-05-2022, 04:41 PM
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I remember a story about Smokey Yunich doing his own interpetation of NASCAR rules when they forbid polishing manifolds. He built a rig out a washing machine pump that circulated water and blasting sand through the manifolds and smoothed them out. He said it worked almost too good you had to watch you didn't wear a hole in them on the sharp corners
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Old 05-05-2022, 05:30 PM
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I think you will be spinning your wheels, and not the bicycle kind!

Without some kind of proven method and/or a lot of trial and error on sample pieces, I think your acid metal removal will prove to be inconsistent, especially where the tube has been welded longitudinally during manufacture.
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Old 05-05-2022, 06:02 PM
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The total practical weight of a bicycle is bicycle plus rider. it seems easier to remove 1% of the riders weight than to remove 10% of the bicycles weight
assuming a 10to1 weight ratio. boxers play with the weigh in weight via dehydration to meet limits then go into the ring at a heavier weight to maim each other
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Old 05-05-2022, 06:29 PM
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Quote:
Originally Posted by Whitetrash View Post
I remember a story about Smokey Yunich doing his own interpretation of NASCAR rules when they forbid polishing manifolds. He built a rig out a washing machine pump that circulated water and blasting sand through the manifolds and smoothed them out. He said it worked almost too good you had to watch you didn't wear a hole in them on the sharp corners
There used to be a company that specialized in something similar. They would pump an abrasive putty thru cylinder head ports, cylinder ports on 2 strokes and jet pumps on Jet Skis. Can't remember the name of the place, probably back in the late 80s. Didn't change the port shape much but they sure were smooth
There was another company at the same time that would polish transmission gears and shafts. I think it was called Supertech or something similar. The Honda racing guys (HRC) used them for all their motors.
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Old 05-05-2022, 07:39 PM
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Irregular action was my fear.

Also I didn't want to wait a week.

But I found some better tubing. It will need a little body work, but the thickness is perfect. I was thinking about a special belt sander setup to do the OD of the tube.

I won't have to bother.
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Old 05-05-2022, 07:46 PM
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Quote:
Originally Posted by terry lingle View Post
The total practical weight of a bicycle is bicycle plus rider. it seems easier to remove 1% of the riders weight than to remove 10% of the bicycles weight
assuming a 10to1 weight ratio. boxers play with the weigh in weight via dehydration to meet limits then go into the ring at a heavier weight to maim each other
I'm building a big scratch custom bicycle. It will be heavier than a factory cruiser bike.

I will be adding to the weight, so more inertia (yay!) but I wish to add as little as possible. One mm tube will be fine, but the .065 stuff was gonna be chunky.

It's for exercise, not racing, so a bit heavy is OK. 40% heavier is awful hard to take though.
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