pjavon
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| posted on 12/11/06 at 10:54 AM |
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antiroll bars
I've got hold of 2 caterham antiroll bars and i'm about to fit them to my tiger, do you lads think i'm right to try the heavyest
rollbar first(18mm) or should i fit the light one(13mm).
I'm fitting them on the front of the car first to see the differnce and then i'll fit the other one to the rear at a later date
any advice please 
Always keep a big hammer and a condom in your toolbox, if you can't fix it with the hammer
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DIY Si
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| posted on 12/11/06 at 10:56 AM |
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Try the lighter one first if they are interchangable. Or if you're feeling really swish, try blade adjusters to vary the effective spring rate
of the bar.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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pjavon
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| posted on 12/11/06 at 11:00 AM |
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Mmmmm ok i'm thick what are blade ajusters
Always keep a big hammer and a condom in your toolbox, if you can't fix it with the hammer
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DIY Si
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| posted on 12/11/06 at 11:05 AM |
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The link that normally goes from the drop bar/link to the anti-roll bar is normally solid/fixed bar. If it's blade shaped/ a bit like sheet
steel it can be adjusted to give a variable stiffness. IE with the blades vertical you get full stiffness, horizontal you get minimum stiffness. It
can be done on one side or both to give more variation.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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DIY Si
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| posted on 12/11/06 at 11:07 AM |
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looks like this if that help explain things.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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pjavon
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| posted on 12/11/06 at 11:11 AM |
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Thanks DIY Si, think i'll stick to rose joints and threaded bar for now but will bare that advice in mind for future upgrades, incase you
haven't worked it out yet this whole suspension thing is doing my head in at the moment so i'll stick to what i know for now
Thanks
Always keep a big hammer and a condom in your toolbox, if you can't fix it with the hammer
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DIY Si
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| posted on 12/11/06 at 11:11 AM |
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This is a non adjustable version, but gives you the idea I think. The blades on this one are fixed,
but the overall idea is about what I was trying to explain.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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DIY Si
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| posted on 12/11/06 at 11:13 AM |
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Don't worry, I'm only just starting to learn about this stuff to! Roll centers and the like where all foreign to me a few weeks/months
ago!
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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goodall
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| posted on 12/11/06 at 11:44 AM |
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what happends if you don't have an anti-roll bar?
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DIY Si
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| posted on 12/11/06 at 12:10 PM |
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Not at a lot really. It can help with the suspension set up though. Some people use them, some feel them unnessecary.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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tegwin
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| posted on 12/11/06 at 12:40 PM |
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I was under the impression that they are only really usefull on a heavier car or a car that is having its nuts thrashed off...
My antique 1995 polo has one...god knows why!
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nitram38
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| posted on 12/11/06 at 12:55 PM |
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It depends on how you like to drive through corners.
Antiroll bars help keep the unloaded wheels in contact with the road (to a point) and therefore give better control.
The opposite is true in wet conditions as they make your car less stable in corners.
Most racers adjust them to very soft or disconnect them in the wet.
I have adjustable front and rear bars on my car but I keep the front one disconnected (rear engine).
This is because that the uk potholes give my front suspension a hammering and have a habit of forcing my adjuster collets off.
I would reconnect them for track use only.
The rears do feel better with the antiroll bar but I do not know how well they will do in the wet.
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goodall
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| posted on 12/11/06 at 01:25 PM |
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so would it be advisable to put one on a awd car that i plan to thrash the nuts off. its the reason i'm building it to do so!
is theres no real need for one on the rear i take it
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Bob C
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| posted on 12/11/06 at 04:47 PM |
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With a lightweight car on stiff springs with a low CoG antiroll bars are gilding the lily a bit...
I would have said wait till you've thrashed it a bit & if you feel it understeers put one on the back, if it oversteers more than you like
put one on the front. You could work it all out theoretically with roll stiffness front & rear, but theory doesn't always relate exactly to
practise!
I believe it is usual practise to tune handling traits thus with antiroll bars - hence the "blade" adjustable variety. Incidentally, my
understanding was that with those the blade itself bent, forming the spring of the antiroll bar - clearly it's much stiffer edge on!
cheers
Bob
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DIY Si
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| posted on 12/11/06 at 04:52 PM |
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Yup, the blade forms part of the spring, or it wouldn't really work when turned horizontal. Can't remember for sure, but I think they need
to be made from spring steel.
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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whittlebeast
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| posted on 12/11/06 at 05:00 PM |
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Remember that with almost any Locost / Super7 that I have ever seen that did not have a full cage is so flexable that the front and rear suspensions
are working totaly independently. This means that a sway bar has the ability to control sway only on that end of the car. It does not have the ability
to move weight across corners as the books assume. This is why adding a rear bar may give the effect of less overstear. This is also the reason that
adjusting the bump rebound on the shocks to full hard appears to only make these cars ride bad.
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John Bonnett
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| posted on 12/11/06 at 05:03 PM |
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It is worth bearing in mind that the more you stiffen the front, the more you will promote understeer. Similarly, stiifening the rear increases
oversteer.
John
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DIY Si
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| posted on 12/11/06 at 05:05 PM |
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This might be a question with out an answer, but would you be able to put a minimum figure on stiffness to make roll bars work "properly"?
I appreciate most 7's aren't the stiffest of chassis, but what type of thing would be? ie would most monocoque's be up to it?
“Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.”
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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goodall
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| posted on 12/11/06 at 05:24 PM |
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can't have enough oversteer, its the whole fun of these cars unless shes incontrolable 
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C10CoryM
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| posted on 12/11/06 at 06:15 PM |
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quote:
Originally posted by DIY Si
This is a non adjustable version, but gives you the idea I think. The blades on this one are fixed,
but the overall idea is about what I was trying to explain.
Actually thats just a regular torsional swaybar. . The first one posted was a blade type though. Bob is right, the blades swivel (sometime
driver controlled) and can go from 0-200lbs/inch or more.
As to how much is torsional stiffness is required I would say not very much. Even completely un-modified cars with less than 4000lbs-ft/degree will
be affected. Most race cars have at least 10,000lbs-ft/degree and I think F1 cars are nearly double that. Can't remember for sure though.
Speaking of F1, even they run swaybars and they are light cars with very high springrates and little wheel travel. A heavier car with softer springs
and more wheel travel will probably always benifit from a swaybar.
Cheers.
"Our watchword evermore shall be: The Maple Leaf Forever!"
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whittlebeast
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| posted on 13/11/06 at 01:41 AM |
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Take the weight of the car with driver in lbs and multiply by 3 to get the ft lbs / deg where the swaybars and springs realy start to behave per the
books. At 1 times nothing appears to work as the books claim. My new Locost that we started to build this weekend is close to 9500 ft - lb / deg but
it does have a full cage. It is possible.
AW
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gazza285
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| posted on 13/11/06 at 02:09 AM |
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quote:
Originally posted by nitram38
Antiroll bars help keep the unloaded wheels in contact with the road (to a point) and therefore give better control.
You had better explain this one to me as I was under the impression that an anti roll bar worked in the opposite way, the loaded wheel pulled the
inside wheel with it, therefore reducing roll. It's pulling the inside wheel away from the road, not helping to keep it in contact.
DO NOT PUT ON KNOB OR BOLLOCKS!
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whittlebeast
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| posted on 13/11/06 at 03:32 AM |
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Let me try to explain whats going on with anti sway bars. Lets assume we have a car with identical front and rear suspensions. Also assume that the
car has a 2000 lb weight with 50-50 weight dist. and is coasting around a corner. The front of the car weighs 1000 but weight transfer makes the
outside tire hold up 750 lbs and the inside tire holds up 250 lbs both front and rear.
Now we add a rear sway bar that at this cornering load will add 100 lbs to the outside rear tire as the new rear bar tries to hold the chassis more
level than the springs alone can do. The rear tire is now pushing down 750 + 100 or 850 lbs. The rear of the car still weighs 1000 lbs so the inside
rear tire is holding up 1000 - 850 = 150 lbs. The weight that gets twisted into the chassis has to get transfered forword thru the chassis and ends
up on the inside front tire or 250 + 100 = 350 lbs. Last the outside front tire holds up 1000 - 350 = 650 lbs. The right rear tire is more
overloaded of the inside front tire is less overloaded so the car feels more lively. This all assumes the chassis is capable of transfering this sort
of torque from the outside rear, forword to the inside front tire.
Reading the Staniforth book will help clear some of this up. The link below is based on his book.
see http://www.ncs-stl.com/Files/ChassisCalcsPublic.xls
Hope this helps
AW
[Edited on 13/11/06 by whittlebeast]
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nitram38
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| posted on 13/11/06 at 09:07 AM |
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quote:
Originally posted by gazza285
quote:
Originally posted by nitram38
Antiroll bars help keep the unloaded wheels in contact with the road (to a point) and therefore give better control.
You had better explain this one to me as I was under the impression that an anti roll bar worked in the opposite way, the loaded wheel pulled the
inside wheel with it, therefore reducing roll. It's pulling the inside wheel away from the road, not helping to keep it in contact.
Quite simple really, the answer is in the name "antiroll bar".
Forget the wheels, we are talking about body roll which will lift the unloaded wheel off the ground.
By linking both wheels together (remember that the bar is attached to the body), when one wheel lifts, the other will too, keeping the body from
rolling.
This means there is more force on the normally unloaded wheel.
Think about it this way, stand on one leg and you have to tilt your weight slightly onto the other leg to stay balanced.
Next try lifting both feet off the floor together.........
Can't be done.
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whittlebeast
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| posted on 13/11/06 at 11:45 AM |
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It's more like a dog standing on four feet with you pushing on the body of the dog. Rover can still pick either on of his feet on your side.
frond or rear. Pick any one. Push harder and Rover can pick up two. Push even harder and rover falls over. That simple.
If the chassis is floppy enough and the roll bars are hugh enough, then the chassis starts behaving like a race kart. An entire new set of math.
With the 1000 lb and 3000 ft - lb / deg car at the left I did manage to put too large of bars. The car would not accelerate straight. It has a $2500
formula 3 torque sensing dif and the weight transfer accross corners at 1 gee acceleration was a fright coming off bumpy corners. The power would
hunt from the left rear tire to the right rear tire and back. That seup only lasted one event and was removed as a lesson learned.
[Edited on 13/11/06 by whittlebeast]
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