Rear End Spacing - Reduces After Welding

[Tom Gagliardi]

On the six frames I've built so far the rear end spacing is reduced after welding. I'm TIG welding my frames. I tack in the frame jig with the proper rear end spacers (i.e. 135 mm for mtb and 130 mm for road) and then take the frame out of the jig for welding. I've been welding with the rear end spacer in place in the dropouts.

On all of my frames so far, after welding and putting in the bridges, the rear end spacing is about 2-4 mm less than where I started, and I need to do some cold setting to get the spacing right.

Any suggestions would be greatly appreciated. Thanks in advance.

[sam]

What are the deminsions of your spacers, many people use a dummy axle that is slightly oversized to help compensate. And of course the better you get the better it will get, im not there myself so im sure someone else might have some better info

[Tom Gagliardi]

The spacers are the exact spec'd size. I have 130, 135, and 142. I thought about just sizing up, but was hoping for a better solution.

[Willie1]

Using a weld sequence that works for you and sticking to it is what you want to accomplish. Know the "pulling power" of the last weld in regards to changes in angles, and have the joint set to compensate for the weld pull when setting up the jig. Differing heat settings, filler material, and filler size will all affect the pull. Experience is the only way to get it right where you want it, and that comes from keeping track of the variables, and sticking to a routine. I am learning the same things right now. I haven't had one come out perfect yet, but am getting closer.

[steve garro]

I tack in the frame jig with the proper rear end spacers (i.e. 135 mm for mtb and 130 mm for road)

On all of my frames so far, after welding and putting in the bridges, the rear end spacing is about 2-4 mm less than where I started, and I need to do some cold setting to get the spacing right.

Any suggestions would be greatly appreciated. Thanks in advance.

That's why dummy axles are 132 & 137.
- Garro.

[MiWi]

Me too.
+2mm compensation with every dummy axle gives me a spot on spacing when finished.

[Tom Gagliardi]

Steve - when you measure the spacing do you measure the 135mm (mtb) from the inside of the dropout or the middle of the dropout?

My dummy axles set it up so its 135mm from the inside of the dropout plates.

[jon_norstog]

Happens to me too. I usually weld or braze up my stay assemblies on a plate jig, then miter them. As to the pulling in, I set the dropout spacing about 4-5mm greater than what I want for a result. Metal moves when you heat or cool it. Just go with the flow and prosper.

jn

"Thursday"

[echelon_john]

Yes on dummy/wider axles to fight what is generally SOME inevitable 'suck-in.'

But the other thing to look at and think through is whether one or the other side is moving more; this might help you refine your process. I.e. are the two sides sucked in from the centerline equally, or is the left or right CS further in off the centerline? If they're equal, then the wider dummy should help a lot. If they're unequal, think about your sequence and experiment.

[MacLaughlin]

RE: ^^^3 posts up^^^ The inside. 130 is the Outer Locknut Dimension, which will come to rest along the inside of the dropouts when a wheel (or dummy axle) is installed.

[Eric Estlund]

Make sure your bridges are proper length and mitered well. Gaps here can suck in and bring the whole thing together.