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Old 06-03-2009, 03:47 AM   #91
claude
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Andy,
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:
http://www.racing-car-technology.com...sworksheet.htm

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.
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claude screwed with this post 06-03-2009 at 04:21 AM
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Old 06-03-2009, 04:32 AM   #92
Andy-Gadget
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Quote:
Originally Posted by claude
Andy,
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
1/
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.
2/
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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Old 06-03-2009, 05:13 AM   #93
claude
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Andy,
No offense taken.
The delima you expresed is exactly why I was bummed out when talking to some suspension gurus left over from our racing days as mentioned in my earlier post. That frustration led to building teh twin torsion bar rig and the results were interesting.
Any suspended machine has a roll center and a center of gravity.If the supension moves when weigth is trnaferred in a corner there is a roll center. How to calculated it on a sidecar rig? I dunno. Read my first post carefully. We raised the supenaion figuring what the heck maybe that will raise th eroll center. It obviously did. I still do not knwo how to calcualte it and was hoping someone here woudl have an idea.
Hey we're all in this together right?
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Old 06-03-2009, 05:13 AM   #94
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Roll Centre.

Keep at it Boys, we'll get there yet.
Andy is almost completely right! Claude too!
Trailing arm suspension systems do have a roll centre, and it is situated at ground level!
The centre of gravity of the average motorcyle-sidecar combination (rider included) is very high off the ground, and, as in the german textbook, it is biased toward the motorcycle, not centered within the "tipover lines"(the contact points of the tyres joined by three lines to form a very skewed triangle) Trikes and the new Can Am Spyder have a centrally located C.of G. within a symetrical triangle, and are equally stable turning left or right. Sidecars are, as we all know, prone to roll over, rather than slide, especially when turning towards the chair.This a consequence of a narrow track (relatively speaking) and a high C.of G. close to the tip over line under the bike.
Anti-roll bars (to apply their tecnical name....sway bars to the general public) do just that, they resist roll, or the tendency to load the suspension on the outside of a turn, and unload the suspension on the inside of a turn,or in other words to oppose the "weight transfer" to the outside of a turn. If over done this is like having no suspension, so any bump will cause the wheel in question to lose grip and slide, and if it grips again could cause a "highside".(Is that what you meant Claude?)

The Roll Axis of a car is a line joining a car's forward roll centre (usually above the ground with modern types)with the rear roll centre, and the inclination of this axis determines how a car will behave in a corner, understeer and oversteer are the terms usually applied.
The car blokes don't know how to deal with us because we have a two track device with only one wheel on the "other" track(the right, for europe & USA, left for OZ & UK)
We still roll, just like a car, but there is no "other" front wheel to support the front corner, so if we over do it turning away from the sidecar, we are in danger of draging the nose of the chair on the ground just like McCardigan's BMW above. [Which looks to have the sidecar axle lined up with the fwd edge of the rear wheel rim (about 9" perhaps?). A bit more lead wouldn't have hurt. IMHO.]
It's getting late, must go, more sermons later. phyllis
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Old 06-03-2009, 06:30 AM   #95
claude
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FOR PHYLLIS' NEXT 'SERMON' WHEN HE WAKES UP...LOL:
Phyllis wrote:
>>Trailing arm suspension systems do have a roll centre, and it is situated at ground level! <<

If this is true can the roll center be raised? If not, how does that explain what we did with the k bike. Not being difficult just curious what your input may be.
The pic below is really bad but you can see the torsion bars and how high they were mounted. As stated I had spun it out in a turn toward the sidecar two different times. Once with the swaybar hooked up and once without. Both times there was no body on the sidecar frame. We figured it was due to a higher roll center being acheived by the placement of the bars.
Oh, in the picture it had a 205 tire on the rear and a 195 on the front and the sidecar. Track width was close to 60 inches and lead was around 14". No lean out. The spin outs took place with 135s all around.
Prior to doing the high mounted torsion bars there was no way it coudl have been spun out the same way under the same conditions with no body on the sidecar frame.
Dang it are you all going to make me build another one of these things?
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claude screwed with this post 06-03-2009 at 06:35 AM
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Old 06-03-2009, 10:18 AM   #96
RedMenace
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Quote:
Originally Posted by claude
<<
The pic below is really bad but you can see the torsion bars and how high they were mounted. Dang it are you all going to make me build another one of these things?

Can you draw us a diagram of this set up?
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Old 06-03-2009, 02:30 PM   #97
claude
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Quote:
Originally Posted by RedMenace
Can you draw us a diagram of this set up?
I don't have any real figures on it Vernon. The torsion bars were mounted quite high. The torsion arm rested on a roller above the rear end housing. The roller is barely visable in the picture.
That rig had quite a few other weird ideas built into it but that is another story.
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Old 06-03-2009, 04:27 PM   #98
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Quote:
Originally Posted by RedMenace

Can you draw us a diagram of this set up?
I assume that the lower tube and short lightened arm in the photo is the front torsion bar termination.
And that there is a similar termination of the top torsion bar at the front.

Interesting set up, but I can't see how it can have any influence on roll centre, as it is the suspension pivot points that determine this, not the springing arrangement, and the back pivot points appear to be standard K bike, I assume the front is a leading link of some sort.
The tyre offset outwards would have much more of an affect on stability than the torsion bars.
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Old 06-03-2009, 05:27 PM   #99
RedMenace
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Quote:
Originally Posted by claude
I don't have any real figures on it Vernon. The torsion bars were mounted quite high. The torsion arm rested on a roller above the rear end housing. The roller is barely visable in the picture.
That rig had quite a few other weird ideas built into it but that is another story.

I don't want figures, just a clearer idea of how it all goes together
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Old 06-03-2009, 05:42 PM   #100
Nemo DeNovo
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New concept for roll control

I'm sorry to change the subject somewhat, but I want to throw this out there and see what you all think of this idea of mine. I've been thinking of this for years, since the days when we used to play with stock cars. We were always looking for an advantage that hadn't been outlawed yet, and I never had the chance to try this one out.

I've seen alot of you hack purists making a big thing over sway bars. I thought of a way to do the same thing with pneumatics and make it fully adjustable, even so far as to enable left or right turn preload. I think this would be easily applied to hack rigs, and may make roll control much more easily installed than with a steel bar.

Picture 2 hydraulic cylinders installed like shocks. The lines attached independantly from the bottom port on one cylinder to the top port on the other and vice-versa. Then charge these separate lines with air or high pressure gas. As long as the pressure remains the same in both lines, the rig would remain level. But if the rig tries to lean, it will load the top of the outside cylinder which will transfer pressure to the bottom of the inside cylinder....pulling that side down.

If large diameter lines were used so gas flow was not restricted no effect would be felt when both wheels encounter the same bumps, because as one side's top was compressed it would feed the other side's bottom as it retracted. This setup would only operate when there is a difference from one side to the other. Increasing the gas pressure would have the same effect as increasing the thickness/stiffness of a sway bar. And in the case of oval track racing, one side could be given higher pressure to preload for cornering.

I don't know if this has ever been tried, but I have no doubt that it would work. My knowledge of hydraulics tells me that the best choice of cylinders would be ones with the smallest possible rods in comparison to cylinder diameter, to keep the differential as small as possible. I don't have the $$ or the facilities to build a setup to test this, but I bet Richard or some of you other "well connected" FF's can find a willing and worthy test bed for this. I want a ride report, that might be a billion dollar patent I just gave away
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Old 06-03-2009, 06:36 PM   #101
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Quote:
Originally Posted by Nemo DeNovo
I'm sorry to change the subject somewhat, but I want to throw this out there and see what you all think of this idea of mine. I've been thinking of this for years, since the days when we used to play with stock cars. We were always looking for an advantage that hadn't been outlawed yet, and I never had the chance to try this one out.

I've seen alot of you hack purists making a big thing over sway bars. I thought of a way to do the same thing with pneumatics and make it fully adjustable, even so far as to enable left or right turn preload. I think this would be easily applied to hack rigs, and may make roll control much more easily installed than with a steel bar.

Picture 2 hydraulic cylinders installed like shocks. The lines attached independantly from the bottom port on one cylinder to the top port on the other and vice-versa. Then charge these separate lines with air or high pressure gas. As long as the pressure remains the same in both lines, the rig would remain level. But if the rig tries to lean, it will load the top of the outside cylinder which will transfer pressure to the bottom of the inside cylinder....pulling that side down.

If large diameter lines were used so gas flow was not restricted no effect would be felt when both wheels encounter the same bumps, because as one side's top was compressed it would feed the other side's bottom as it retracted. This setup would only operate when there is a difference from one side to the other. Increasing the gas pressure would have the same effect as increasing the thickness/stiffness of a sway bar. And in the case of oval track racing, one side could be given higher pressure to preload for cornering.

I don't know if this has ever been tried, but I have no doubt that it would work. My knowledge of hydraulics tells me that the best choice of cylinders would be ones with the smallest possible rods in comparison to cylinder diameter, to keep the differential as small as possible. I don't have the $$ or the facilities to build a setup to test this, but I bet Richard or some of you other "well connected" FF's can find a willing and worthy test bed for this. I want a ride report, that might be a billion dollar patent I just gave away

Looks like we came out of the same stock car school. We tried something very similar many many years ago. 2 year suspension from the sport Young and stupid.
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Old 06-03-2009, 07:29 PM   #102
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Quote:
Originally Posted by Clancy
Looks like we came out of the same stock car school. We tried something very similar many many years ago. 2 year suspension from the sport Young and stupid.
2 year suspension?!?!?! It must have worked REAL GOOD!!!
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Old 06-03-2009, 07:49 PM   #103
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Quote:
Originally Posted by Nemo DeNovo
2 year suspension?!?!?! It must have worked REAL GOOD!!!

Yeah, it worked fine. Mine was hydraulic, with a couple of pumps that were activated at preset suspension travel limits. We won a couple of decent races but then they inspected us from top to bottom. Like I said, young and stupid.
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Old 06-03-2009, 08:07 PM   #104
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Airbag suspension on trucks works similar.
Load up one side while taking weight off other, transfers the air to the weighted side. Also constant height due to air level valve. More weight, more air is supplied.
You still need shockers though.
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Old 06-03-2009, 08:21 PM   #105
Nemo DeNovo
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Quote:
Originally Posted by johno
Airbag suspension on trucks works similar.
Load up one side while taking weight off other, transfers the air to the weighted side. Also constant height due to air level valve. More weight, more air is supplied.
You still need shockers though.
Yes, this would be in addition to shocks. And compressing one side would cause the other side to actually pull down. A little different than airbags, they can only lift...or not lift.
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