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Fork Blade Has Ripples

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Fork Blade Has Ripples

Old 12-06-19, 04:40 PM
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TiHabanero
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Fork Blade Has Ripples

Had a single fork leg sitting on the shelf and a conduit bender so I proceeded to bend the blade. There is a series of very minimal, low profile ripples that can be felt, but not seen on the inside radius. Is it correct to assume that if the blade had been packed with sand these ripples would not have formed?
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Old 12-06-19, 06:50 PM
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I've never packed the blades with sand when bending them. Can you post up some photos of both your bending setup and the ripples themselves?
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Old 12-06-19, 07:40 PM
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I have ruined blades by flattening the inside, but never gotten ripples. My thought is that you really want to bend with a vee shaped form. Have thought about trying to match the shape of the blades better, but I don't think that is going to happen.

I would also like to see the ripples. If you can't see them, maybe they are okay
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Old 12-06-19, 09:02 PM
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Did you braze in the drop out first? Andy
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Old 12-07-19, 07:30 PM
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Ends not brazed in. Just a fork blade. Put it in the conduit bender to see if it could be used as a blade bender.
The rippled can't be seen, but can just be picked up when I run a finger over iit. Look op conduit bender and you will see exactly what I used, no mods.
Unable to correct typos again. Stupid tablet.
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Old 12-07-19, 07:39 PM
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Can you post up some photos
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Old 12-07-19, 08:52 PM
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in comparison to a fork blade, a conduit bender is a flat cylinder. And the surface may be rough enough to put dings in a blade. What blade was it?
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Old 12-08-19, 06:54 AM
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Can't remember where I got the plan, Henry James maybe (Hank), but I made a simple bending pattern out of wood which works well. Took a large round file and contoured the bending radius so the blade nestles in securely. That form works just fine to bend blades without ripples like being mentioned. With such a simple apparatus available using a conduit bender won't be needed.
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Old 12-08-19, 10:13 AM
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Packing a blade with sand is more about keeping the blade from widening/flattening in cross section at the bend then is about making the bend consistent. But I've never done it so what do I know. Andy
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Old 12-09-19, 05:32 PM
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Blade is a Reynolds 531. I will post images as soon as possible. Will need to do a quick sanding of the tube to remove the surface rust from years of storage.

Andy, the blade did flatten out a bit, which I was not expecting.

Nessism, I can easily make a bending block, and will likely go that route, just wanted to use the conduit bender as an experiment to see how well it worked. Overall, it works, except for the flattening, and ripples that can be felt, but not seen.
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Old 12-09-19, 09:37 PM
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Some builders will over rake their blades then squeeze the flattening out a tad which un rakes the blade a small amount. The blade trapped between boards in a big vice do a good job at this. Generally the thinner the blade's wall or the tighter the bend the more it flattens or ripples. Andy
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Old 12-10-19, 10:46 AM
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I thought about making a rounded bending die, but I came to the conclusion that a vee shaped grove is your best bet. Just make sure that it's wider than the blade. I cut a slot with a tablesaw and then used a chisel to make the rest of the vee. I thought about setting up a router to do it, but I feel pretty good about the way I did it. BITD, a friend had some flat fork bending dies that I used. They worked fine on thick 531, but they would flatten thinner blades.
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Old 12-10-19, 11:57 AM
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After 10 minutes the pic is finally available. Not sure why, but Android, Chrome, and me do not get along. In the pic you can see the three ripples as they are contrasted quite nicely as high spots.
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Old 12-10-19, 03:06 PM
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Interesting. I imagine there are a lot of forks out there with bigger ripples than that
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Old 12-10-19, 03:43 PM
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I'm seeing the discoloration, but the bumps are difficult to visualize.

I'm wondering if your jig needs to be better contoured to the tubes. Also make sure your jig is smooth.
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Old 12-11-19, 11:15 AM
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Although this blade will not be used, I must ask if the ripples in the blade will affect the integrity of the tube leading to failure? Has anyone seen this before? Has anyone seen this on a production bike?
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Old 12-11-19, 11:48 AM
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I don't know that I have examined any blades to that degree. I have some pre-bent 531 blades, I wonder if those have any rippling. I can't imagine it would make them much more likely to buckle. Probably if you were to crush them to failure these would fail a little earlier.
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