Frame dimensions for correcting Headstock angle.

Looking at the pics the assumption is that the head tube is in perfect perpendicular alignment (ie no twist from vertical) and no jig or bracing is required?

In the comprehensive frame measurements it shows 26.5 deg rake? I thought they'd be in the region of 28 deg standard.
 
The frame is at 28° Quentin. The fork stanchions at 26.5°... there's those odd 1.5° through the angled drilling of the yokes!

piet
 
When I have a Frame I need to measure, I put it on my welding table so I have a stable starting point, then I can start with my measuring tool.
 

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piranha-bro2 said:
Ah, I would have hope they were left out of the useful equations!! What a horrible idea.
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The reverse of what the chopper chappies did a few years later.

Not such a dumb idea Quentin. The factory chose the head angle possibly for straight-line stability, but needed a lot of yoke offset to afford decent steering lock. This would have increased wheelbase (making the bike less agile) and reduced trail (bad for stability). The angled stanchions brings the trail and wheelbase back to acceptable levels while retaining the head angle for a decent level of stability.

A U-turn on a bevel SS Ducati (flat head angle, minimal yoke offset, mile-long wheelbase and steering lock not worth mentioning) is a challenge, easy-peasy on a triple. Not much in it in straight-line stability, but the triple is so much more agile.

piet
 
With bare frames, I like the idea of adding long tubes through the open steering head and swingarm pivot. Having these plumb and square to each other is a critical first step. In building, there is a term called winde or being out of winde. It referred to being twisted out of square. It's hard to measure accurately as moving something in one plane of reference throws it out in another plane, you can chase this a lot before getting it right. I just watched Brook Henrey true a Ducati crank, and it's exactly the same thing. Fascinating to watch.
 
The last time I did a U-turn on a Bevel, I hit the lock stop mid-turn, and if I hadn't got a leg out, I would have dropped it. Not good.
 
Vince said:
The last time I did a U-turn on a Bevel, I hit the lock stop mid-turn, and if I hadn't got a leg out, I would have dropped it. Not good.
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Not the first and certainly not the last, Vince! A couple of mates had bevels, their starting and handling antics were circus-rife at times.

piet
 
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