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New jig design

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New jig design

Old 02-22-22, 05:52 AM
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guy153
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New jig design

So far seems to be working quite well. The design-goals here were to have something quite small that would go on the top of the table; be nice and solid to hold everything still; and have independent adjustment of HT spacing and angle, so that you can get each right one at a time. The ST is vertical at all times (the HT angle is relative). This simplifies the design and keeping things vertical is much better when getting the side-to-side alignment with a laser level box. There is nothing for the rear axle because I attach the CS first using this simple fixturing:




So here is the new jig (it looks all shiny like that because I painted it with owatrol):






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Old 02-22-22, 06:56 AM
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unterhausen
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I was thinking you could attach the chainstays first by swapping the seat tube around and then I read your text.

I'm making a chainstay fixture right now, attempting to only use things that are in my junk pile. I think I figured it out.
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Old 02-22-22, 11:21 AM
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A follow-up with a couple more pictures showing the use of the laser:

Step 1: get it all nice and level. Note that the laser line has to pass through the centre of the rear axle as well as the centre of the BB shell. That means we're really on the centre plane of the bike.



So now step 2, without moving the laser, drop the seat tube down, so that the laser can see the HT. It's also sweet that with it rotated around the laser is still hitting the centre-line of the axle (although this isn't actually critical at this point-- what matters is just that the ST goes right back to exactly where it was).


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Old 02-22-22, 11:24 AM
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Originally Posted by unterhausen
I was thinking you could attach the chainstays first by swapping the seat tube around and then I read your text.

I'm making a chainstay fixture right now, attempting to only use things that are in my junk pile. I think I figured it out.
Yes I did think of using it the other way around to do a CS fixture. Could basically use the same assembly that holds the HT to hold the rear axle. But I like my existing system for doing the CS just using the table. It works really well for me so why change it. I can also draw out the position of the tyre and the chainrings onto the table which is helpful.

I did fit the actual BB and chainrings after tacking those CS just to be sure though... You can't be too careful. This is a touring frame so a road-triple with a 68mm shell and 135mm rear spacing. Always a bit tight!
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Old 02-22-22, 06:09 PM
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Where is the laser?

The theme of my new chainstay fixture is "everything is round if all you have (working) is a lathe"
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Old 02-23-22, 02:49 AM
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Originally Posted by unterhausen
Where is the laser?

The theme of my new chainstay fixture is "everything is round if all you have (working) is a lathe"
That should work. My approach is to rely on the laser and try to make everything else adjustable. So the things that hold the ST and HT are based on kind of dropouts. This means I can file one side or the other if things are not perfectly square, or even in theory offset the BB fixture in the dropouts a little bit if the BB shell is not quite square to the ST (cue arguments about how to align frames but the reality is that on a TIG frame that ST/BB joint is not going to change its angle after it's welded-- all you will do is put a bow in the ST if you try to correct it).

The laser is off to the right on a little adjustable stand type thing:


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Old 02-23-22, 09:52 AM
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All I can say is that your domestic partner must be very understanding in tolerating such a mess so close to the washer and dryer My wife would not be happy (and you know what they say about a happy wife). Andy
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Old 02-23-22, 11:17 AM
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I'm very fortunate to have such a tolerant spouse
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Old 02-23-22, 11:23 AM
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Originally Posted by Andrew R Stewart
All I can say is that your domestic partner must be very understanding in tolerating such a mess so close to the washer and dryer My wife would not be happy (and you know what they say about a happy wife). Andy
She does make me clear a path to it (on the threat of knocking over all my stuff
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