Torsion beam roll centre
Torsion beam roll centre
(OP)
Or sometimes called twist beam.
How is the roll centre calculated?
Google is failing me, as is Fred Puhn, Ive been looking now for days.
I hope this is not a stupid question, may be the reason Im not finding an answer!
Is it at wheel centre height?
Is it at pivot height?
Is it somewhere else?
Id also like to know the calculation if the 'trailing' arm back to stub axle is not directly inline with the front pivot bushing, as in, trailing up/down as it extends to the rear when viewed from the side.
Thanks in advance.
BG.
Beam in question below,
How is the roll centre calculated?
Google is failing me, as is Fred Puhn, Ive been looking now for days.
I hope this is not a stupid question, may be the reason Im not finding an answer!
Is it at wheel centre height?
Is it at pivot height?
Is it somewhere else?
Id also like to know the calculation if the 'trailing' arm back to stub axle is not directly inline with the front pivot bushing, as in, trailing up/down as it extends to the rear when viewed from the side.
Thanks in advance.
BG.
Beam in question below,





RE: Torsion beam roll centre
http:/
the second one is more "hands on" and provides some simple calculations which can also be applied to de Dions, like the old pre-war Mercedes Grand Prix cars, and the infamous Rover 2000 to name two. It's in the attachemnt
((eng-tips seem to let attach only one link at a time)
Hope this helps.
RE: Torsion beam roll centre
Thanks a million, I dont know why I could not find the second link, I did find the first one.
To the drawing board...
BG
RE: Torsion beam roll centre
I'm at mine this weekend too. (I use pencils, however..well.. actually, more like erasers.)
RE: Torsion beam roll centre
I was drawing a suspension the last day on my room wall, and the intersection points of two lines ended up following on into the other room which involved removing a door and some paintings to pull a string line. LOL.
The joys of the pen! Still...never crashes, breaks down, or gets a virus! Except of course, when I get all those symptoms!!
Brian!
RE: Torsion beam roll centre
Norm
RE: Torsion beam roll centre
RE: Torsion beam roll centre
The Design of Trailing Twist Axles
Date Published: 1981-02-01Paper Number: 810420
Author(s):
Terry L. Satchell - Pontiac Motor Div. General Motors Corp
Trailing twist axles represent a relatively new type of rear suspension system that is becoming more common with the increasing number of front wheel drive vehicles.
The design of the axle structure must account for the complex interactions of the placement and type of sub-components used to meet the load carrying, geometric, and roll control requirements of the suspension. The crossbeam placement is the primary variable in controlling suspension parameters.
RE: Torsion beam roll centre
Well i'll wait for the photocopy before deciding how much handwaving is involved.
Three questions
1) will the properties of the bushes affect the RCH?
2) Will the torsional stiffness of the beam affect the RCH?
3) will the tire vertical stiffness affect the RCH?
Cheers
Greg Locock
New here? Try reading these, they might help FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm?
RE: Torsion beam roll centre
But, the ability to have a decent, load dependent roll understeer coefficient (as the payload increases, the total vehicle understeer can essentially be maintained constant) makes this suspension design quite attractive.
Still, the ability to sense and measure the effects on the amount of roll is so dwarfed by the influence the same parameters have on lateral force steer and camber and roll steer, make the study of such things a good academic exercise only, IMHO.
The coolest thing you can do to teach new handling evaluators is to connect the cross beam of a twist axle to the control arms using something similar to a pipe flange using, let's say 6 variable bolt positions. By rotating the V beam around these 6 positions and driving the car with the same tires, your Grandmother could tell the difference bewteen the best and the worst case. Anybody who claims roll oversteer is good for a car's handling rating will have to admit the error in their thinking.
I'm a firm believer that a twist axle would make a very nice package for a small pickup truck because of the load dependent geometric properties. Having a constant steering gain truck, no matter what the load, is a nice, safe package. Just don't put in Level Control to screw up the advantages...
RE: Torsion beam roll centre
''Three questions
1) will the properties of the bushes affect the RCH?
2) Will the torsional stiffness of the beam affect the RCH?
3) will the tire vertical stiffness affect the RCH?''
You really did have to ruin it and throw all that into the mix didnt you...;)
cibachrome, Ill have to digest all that over coffee later, thank you.
Brian,