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Old 06-03-2009, 04:32 AM   #92
Any bike can go anywere
Andy-Gadget's Avatar
Joined: Jul 2006
Location: Hobart, Tasmania
Oddometer: 1,363
Originally Posted by claude
If this stuff interests you keep reseaching.
1) Any vehicle that has more than a single track and a supension will have a roll center.
2) Sidecar outfits are no longer motorcycles.

Too many times there is the assumption that sidecar rigs have no suspension on them. Even some of the books written have been guilty of this
But how do you calculate the roll centre on a system that moves the way a motorcycle and sidecar swinging arm system moves, EVERY bit of information I can find assumes that the suspension pivots inwards, not the way a bike system works.
Saying it has one isn't showing how it is calculated.
If you can't calculate it, does it exist in any meaningful way at all.
It will be from the tyre contact patch, that is the only consistant bit of information I have found, but to where is the line extended.
Is it along the ground?
If so then it can be ignored as it has the same vertical distance to the C of G as the tyre contact patches.
They are still motorcycles as far as the planes the suspension works in are concerned, not talking about steering dynamics here, but about suspension interaction, and mostly back and sidecar suspension.
Trikes have a roll centre that can be calculated, because they have symetrical car type suspension, but we aren't talking trikes here.

I am not winding you up specifically Claude, this isn't in any way a personal attack, just trying to understand how it works, and I am more and more coming to the conclusion that it can't be calculated, doesn't exist in a useful form, and so treating it empirically is the only way to go.
This is how all the "Manuals" for sidecar set up go, Phil Irving said as much in the quotes I have seen so far.
So either through ignorance or knowledge the "old" systems are the ones to use.
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An investment in knowledge always pays the best interest"
Benjamin Franklin.
'95 Sport 1100 Guzzi,'84 Cali 2 Guzzi, '95 Guzzi mille, '84 R65LS, '84 R100, '82 R100RS, '05 DL650, '72 Bultaco Sherpa T 350, '78 Montessa 348, "00 XR650R
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