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Old 02-05-2003, 02:33 AM   #1
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Default Chassis flex

Chassis flex

Here you have a question, what has caused me many long evenings before sleep:

How can you get benefit out from chassis flex and how does it effect to car handling?

It is known from beginning, that stiffer chassis is better; due to suspension is working properly. You can feel e.g. spring change effect more clearly because chassis has no play.

But how this matter really is? Does it matter in what direction chassis has its flex or should it flex to all directions? Is car with torsional tension faster than car with lot of torsional flex? Or should flex be in longitudinal axis of the car?

So is there really benefit that you can get out from chassis flex or twist? Or do you always loose?
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Old 02-05-2003, 02:49 AM   #2
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iv'e alway's tried to have and keep a stiff chasise and it seem's to be very good if you want more turning put front softer spring's
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Old 02-05-2003, 04:28 AM   #3
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Chassis flex is generally not a sought after aspect of a race car, s chassis flex i an uncontrollable aspect of tuning, the chassis loads up and then snaps back causing the car to be unpredictable, most cars you look to creating a solid platform and then adjust the suspension to suit your driving style and track requirements
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Old 02-05-2003, 05:12 AM   #4
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Default pro3

for an example of a car with too much flex... see a standard pro 3 from HPI. everyone who bought this car either sold it.. or.. as i have, turned it into a static model with alot of purple aluminium, and carbon fibre ... never to be raced again

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Old 02-05-2003, 05:35 AM   #5
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well if a chassis flexes it becomes part of the suspension which is an unwanted characteristic. an infinitely stiff car makes the suspension do all the work so its easier to tune.

a flexy chasssis will give you more grip but behave like a sponge on high traction surfaces

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Old 02-05-2003, 05:45 AM   #6
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Quote:
Originally posted by schumacher
a flexy chasssis will give you more grip but behave like a sponge on high traction surfaces
Nice phrasing
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Old 02-05-2003, 07:35 AM   #7
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Can someone explain why a flexing chassis would give more grip?
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Old 02-05-2003, 09:49 AM   #8
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It allows the car to be more compliant with the racing surface.
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Old 02-05-2003, 03:29 PM   #9
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What that means, and the principle works the same with springs, etc., is that it delays the car's reaction to the track surface allowing the tires to grip a bit more before they have to actually take lateral forces (turn)

The longer you let a car roll before it actually turns, the more grip you let the tires have - it lets them get into the actual turn a bit more gently, lessening the lateral forces - it lets them grab a bit more before they're subjected to the full lateral forces of the turn.

If you have a very stiff suspension, or a very stiff chassis, the car is going to try to react IMMEDIATELY. This puts a LOT of load on the tires and will try to get them to break fast.




Something like this.

I just read this through and it seems somewhat confusing - correct me where I'm wrong and where I am just plain old wierd! (ummmm, well, not EVERYWHERE I'm wierd. . .)
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Old 02-05-2003, 05:42 PM   #10
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hmmmm,...
well,it seems that majority of the RCers don't like chassis flex,but i feel that a suitable amount of chassis flex can benefit the novice also.
it will make ur car more forgiving 2 setup mistakes and also easier 2 drive.
take the ta04r for an example,i have hop-up from the carbon reinforced tub chassis(more flex) to the carbon fibre lower deck(less flex) and i feel that the carbon reinforced tub chassis is more stable and also forgiving 2 drive...
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Old 02-05-2003, 06:39 PM   #11
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Is stock classes and on rubber a bit of chassis flex can make the car feel good, but when you are running foam on carpet and mod the flex turns into unpredictability.
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Old 02-05-2003, 08:48 PM   #12
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Default My take on chassis flex

I agree with most of the stuff said already about chassis flex. What I didn't see mentioned is that chassis in addition to making the car easy to drive also will cause the car to scrub alot speed in the corners.
This is one reason while most of the top of the line Electric/Nitro Cars have very stiff chassis structures and as an experienced driver, you will WANT the car to react quickly to your inputs.
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Old 02-07-2003, 02:40 AM   #13
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First of all thanks for all replies,

I’m not fully agreed with that chassis flex is uncontrollable aspect of tuning; it is more like tuning option without adjustments, normally. Chassis flex is a solid magnitude depending on chassis. But effect of it is a kind of “progressive” depending on spring setup. I do not mean to go to setup which has more flex from chassis than it’s springs.

How comes that chassis flex is unwanted characteristic if it creates more grip? Naturally Foam-tires require more stiff chassis than rubber tires that “sponge effect” does not happened. I am looking for how this can be specified and how more grip is greatening?

Isn’t it so that flex chassis has lower resonance frequency than stiff chassis? This should mean that if stiff chassis is bend is jumps back more quickly than flexible chassis and effect of unpredictable is then greater and the car gets nervous. If you now think about that stiff chassis bends less you are right, but when you change to foams (more grip) even stiff chassis will bend.

Boomer: You have a lot of point; somehow this flex effect is connected to tire over loading phenomenon. But how can we use it as a tuning option?

If you have a flexible chassis what are the other setup parameters to count and I’m very curious to know answer to flex direction, how does it matter?
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Old 02-07-2003, 03:02 AM   #14
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Maybe this flex issue are unwanted, because we know too little about it? For example how to adjust it and in which situtations more flex is an advantage? Somehow a stiff chassis seems to be easier to understand....

Some suggestions to adjust flex: On a twin deck car, different top-decks can be used. Or extra joints between upper and lower deck. Or rubber rings between suspension mount and upper deck. On most types of cars, you can try cut some of the shock towers. Or use softer rims. Or cut some of the suspension arms. There are probably a more you can do.....

A car as the Pro3 are doing well on slippery surfaces. And it's quite easy to setup.
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Old 02-07-2003, 05:47 AM   #15
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i think that if there was a way to tune chassis flex hara or one of the other hpi hotshots woulda run the pro 3 ey.. but.. they all went off on proto types or.. carbon fibre shod pro 3's
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