Gearbox Cradle

What method an equipment would you use to measure to such an accuracy ?
An when an how was the equipment checked to make sure it is correctly calibrated ?

The tolerance for run out of the wheel rim is normal 0.020" so if that to was not prefect then all the work to line up the other components to such I fine degree would be surely wasted?

L.A.B. said:

I think for you to say "you will have problems" is just speculation? I don't know if my Commando's swinging arm is exactly perpendicular to the frame or not, I somehow doubt that it is, but I haven't experienced any problems as such.

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It's not speculation. Before alignment bike displayed symptoms of worn swing arm bushes i.e weaving through bumpy corners. After alignment this does not happen. You say you experience no problems - how much of the rear tyre do you use i.e lean angle through corners, how fast do you go through corners, how fast do you go through bumpy corners, how does your bike steer hands off at 80mph?

L.A.B. said:

What was the actual outcome? Did you or, preferably, an impartial third party notice any improvement in the handling or ride afterwards?

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Only I have ridden the bike before and after. One person has ridden the bike post alignment albeit at legal speeds - John, NOC Northumbria branch member, at last years Borders Rally. I was on his bike. He also followed me (on his isolastic featherbed Commando) at speed through unfamiliar (to me) twisty local B roads for some miles. He seemed impressed, unless he was too polite to criticise. We were approaching 90mph in places, no problems.

What I don't understand is peoples reluctance to accept that the frame requires precise manufacture to work at it's optimum just like any other precision component. Owners are prepared to spend money on precision made brakes, fork components, rear suspension, engine components etc but when it comes to checking the frame the attitude apparently is, " what's the point - it'll be o.k". :? :?

toppy said:

What method an equipment would you use to measure to such an accuracy ?
An when an how was the equipment checked to make sure it is correctly calibrated ?

The tolerance for run out of the wheel rim is normal 0.020" so if that to was not prefect then all the work to line up the other components to such I fine degree would be surely wasted?

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I use - amongst other precision measuring tools, a granite surface table, flat to within 0.006mm over its surface area, toolmakers precision blocks and vernier height gauge calibrated using a Mitutoyo 3" gauge block.

You can get run out on spoked wheels closer than 0.020". If you use cast wheels run out would be possibly +/- 0.001".
You're missing the main point regarding the swing arm axis out of square to the steering head axis and it's effect on the rear wheel centre line relationship to frame centre line which will continually change as the swing arm moves up and down. The greater away from square the two axes are the greater the continual change in dimension between rear wheel centre line to frame centre line - hence the worn swing arm symptoms. Isolastics work; reference the Monocoque Norton.

I have got the answer that i was after and i respectfully request no further replies or comments are needed.. :roll: :roll: :roll: :roll:

Time Warp said:

If you were to clamp a laser pointer to end side of the swing arm and a target plate each side of the front down tubes then went for a spirited ride (maybe even moderate) I am fairly sure on left to right transitions the results would be eye opening. (even sweeping corners at tip in)
It would make a mockery of a cradle and components set up to the imaginary 0.001"

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So this would apply to Peter Williams monocoque too - I don't think so. The dimension 0.001" definitely exists, Multiply by a thousand and you get an inch.

One Each side is almost enough . :wink: 1 1/4 is Thewperb .

Nailing the back Iso Up - you THEN check the Side Gap at the FRONT .
SHIMS set so the gap ( 1 1/4 ) is EQUAL Each Side . This means its not lozenged & binding .
Id found past 4 1/2 clearance ' the Weave ' wasnt eliminated . Id hate to ride it at 10 thou. clearance .
At 5 it just started to get rear camber ( Road Camber ) steer . Some call that a Weave .