|06-03-2009, 04:47 AM||#12|
Joined: Mar 2002
Location: Middleburg, Pa. (Snyder County)
If this stuff interests you keep reseaching.
NOTE TWO THINGS:
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
The following is a statement taken from a website devoted to race car suspensions. I hope it will shed light on what we have discussed here.
"It is clear that low roll centre give little geometric weight transfer and most of the weight transfer goes through the springs (elastic weight transfer), and is therefore delayed by the time it takes for the vehicle to take a set. Conversely, with high roll centre most of the weight transfer precedes the body roll, leaving a smaller amount of weight transfer to go through the springs".
What they are talking about is that with a high roll center the mass of the vehicle weight is transferred around the low roll center and doirectly onto the outside springs. With a higher roll center the weight transfer is in more of a lateral motion which induces less body roll.
Check out the site here:
As mentioned earlier regarding the track bar adjustments we hear of during a NASCAR race what they are doing is moving the roll center up or down at the rear to either unhook the rear or hook it up more.
When we were still racing the sprints and midgets we had a bar on the front axle that worked in similar fashion ( at the time most called it a swaybar even though that was totally wrong nomenclature). By raising or lowering this bar you moved the roll center which either put more down force on the right front or less.
In the rear there was also a bar called a 'jacobs ladder' which also was adjustabel up and down for the same purposes. Lower the jacobs ladder( some call it a 'w' link because that is basically what it is shaped like) and it would plant the right rear....because the roll center was lowered and the weigth woudl transfer down on the right rear suspension. It also induced more body roll. Raise the jacobs ladder and it woudl unhook the right rear as weight was then tranferred in more of a lateral motion.
This is basic suspension stuff and is really oversimplified here.
Look back at my earlier post about the torsion bar suspension on the rear of the k bike rig. The results were pretty amazing to me. No, it was not calculated on paper but the results were what we wanted to see.
We can quote all kinds of stuff off the net and get a mindset that we are right or wrong but the proof is in the doing.
In fact (don't run me out of town on this one) think of what would happen if we coudl get the roll center above the center of mass....
Oh, by the way one of , if not THE, biggest influences of CoG location on these sidecar rigs is the operator. He or she can only be lowered so far.
Founder: Internet Sidecar Owners Klub at SCT
President: C Stanley Motorsports Inc.
claude screwed with this post 06-03-2009 at 05:21 AM
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