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Chassis Testing - Who's done empirical measurement? > Chassis Testing - Who's done empirical measurement?
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Chassis Testing - Who's done empirical measurement?

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Old 03-26-2018, 10:25 AM
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Default Chassis Testing - Who's done empirical measurement?

Howdy everyone,

I keep reading about "stiffer this" and "flexy that". I want to figure out if anyone has done testing on who's got the stiffest, who's got the floppiest, and what changes make what differences on chassis?

I suspect X-ray has done this, in house. (I suspect that isn't something they wanna publish). Tamiya has done it ~at least~ through trial and error, but I don't see them publishing any of it.

What numbers would you care about? Getting torsional stiffness is really easy. Getting longitudinal stiffness is a good bit harder. While we're at that, perhaps checking CG?

What are your thoughts? Do you care what the answers are?
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Old 03-26-2018, 11:23 AM
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All I know is that Al Bundy scored 4 touchdowns in one single game while at Polk High

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Old 03-26-2018, 11:28 AM
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Originally Posted by Marcos.J View Post
All I know is that Al Buddy scored 4 touchdowns in one single game while at Polk High
Bundy, Al Bundy, c'mon man
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Old 03-26-2018, 12:04 PM
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When I was 16-17 years old it was always the stiffest but now at 71 it is definitely the floppiest it has ever been.
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Old 03-26-2018, 12:26 PM
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Originally Posted by Adamska27 View Post
Bundy, Al Bundy, c'mon man
spell check sorry lol
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Old 03-26-2018, 02:35 PM
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If you're having stiffness issues with age, you should probably investigate the crowd you hang out with. Just sayin.....

Back to the subject at hand. Getting kg/deg/m measurements aren't exactly difficult, for torsion. And most chassis have a good mount built in for doing it, in the shape of shock towers. (Touring cars, buggies, minis, etc...)

Longitudinal stiffness, is still not "bad". put the chassis up on blocks, across the axle lines, and put a load at the chassis CG, measure the deflection.

Measuring CG is fairly easy too, if you have scales that are precise enough. Tip tables, and a 4 wheel scale set would allow that to be calculated. But what's the useful number? with or without a body? with or without wheels? At the chassis? At ride height?
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Old 03-26-2018, 02:55 PM
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Originally Posted by mleemor60 View Post
When I was 16-17 years old it was always the stiffest but now at 71 it is definitely the floppiest it has ever been.
Yes, I'm stiff everywhere I used to be limber and vice versa!
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Old 03-26-2018, 03:03 PM
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Originally Posted by Nerobro View Post
If you're having stiffness issues with age, you should probably investigate the crowd you hang out with. Just sayin.....

Back to the subject at hand. Getting kg/deg/m measurements aren't exactly difficult, for torsion. And most chassis have a good mount built in for doing it, in the shape of shock towers. (Touring cars, buggies, minis, etc...)

Longitudinal stiffness, is still not "bad". put the chassis up on blocks, across the axle lines, and put a load at the chassis CG, measure the deflection.

Measuring CG is fairly easy too, if you have scales that are precise enough. Tip tables, and a 4 wheel scale set would allow that to be calculated. But what's the useful number? with or without a body? with or without wheels? At the chassis? At ride height?
If my memory doesn't fail here's the deal: calculate spring,roll bar, tire and roll centre stiffnesses then raise a tire, measure suspension displacements. The remaining displacement is the one taken by the chassis.

Or even easier, replace shocks with turnbuckles and use setup wheels, raise a wheel then measure how much displacement it took to the other tire on the same side to move. Weight raised wheel to know gr/mm, measure angle to know N.deg.

Hey, do you know why we went from 5.25" floppies to 3.5" ones?
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Old 03-26-2018, 03:13 PM
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This is why some keep different versions of the same chassis in the pit box. Really it comes down to grip and driving style and will vary depending on setup.

And yes, that was a sweet game!
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Old 03-26-2018, 11:14 PM
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Originally Posted by 30Tooth View Post
If my memory doesn't fail here's the deal: calculate spring,roll bar, tire and roll centre stiffnesses then raise a tire, measure suspension displacements. The remaining displacement is the one taken by the chassis.

Or even easier, replace shocks with turnbuckles and use setup wheels, raise a wheel then measure how much displacement it took to the other tire on the same side to move. Weight raised wheel to know gr/mm, measure angle to know N.deg.
That's the hard way. That's not how they do it with real cars. And doesn't isolate out the bits you're actually changing. Bolting a pair of straight edges to the shock towers and applying torque would eliminate all the sloppy bits.

Originally Posted by AlBundy View Post
This is why some keep different versions of the same chassis in the pit box. Really it comes down to grip and driving style and will vary depending on setup.
They do. Tamiya sells 3 kinds of arms, the plastic chassis have at least two tubs, and often various other stiffeners available. Also some chassis have optional standoffs. X-ray has three kinds of arms. Three kinds of top deck. Three lower chassis plates. Three kinds of bulkhead joiners. And removable standoffs.

But... I want it quantified. Guess and check is a really terrible way to go about things. And if you want to compare between two chassis, you will end up going deep on option parts to get an equivalent experience.

The answer to that, is getting data that you can use to do real comparisons with.
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