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Old 09-22-2009, 12:06 PM   #16
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Davidka

Yeah...
i saw Thunder Tiger EB4 S3...
that people really under stand wath is Stiffnes....

may be they have more words that me to explain haw you donīt want that the chasis flex or twist...

Clap my hands to Thunder Tiger EB4 S3...

Diego.
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Old 09-22-2009, 01:03 PM   #17
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Only one more question...
If the chassis works as a part of the suspension, the only way for this is that the energy canīt be absoerved by the shocks and they bottom up, because if they donīt bottom up, they can continue absorving for a example a landing.....
the other possibility is that the movement of the piston across the silicon is less faster than the impact, so this is distributed to the car and chassis....
Am I right ?????

Because, If the shocks works good.... why the impact will be absroved by the chassis.... maybe you need a little of flex for frontal hits where the shocks cant work.... I donīt know...

In the other hand, somebody tell me something related with the dumping speed... but in our cars... first reaction is on the shocks... and then on the chassis... so, if the shock reaction is not to fast, why the chassis will compensate this ...

Thanks !
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Old 09-22-2009, 01:27 PM   #18
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Quote:
Originally Posted by PTP Racing View Post
I was speaking about the brand name Matrix carbon chassis for the 8ight. I assumed Integra was also.

I just yesterday for the first time saw a carbon chassis for the CEN Matrix which I think they said they are just now beginning to test.
I sure was....and ive seen the stuff from Monsoon and the pics leave a little to be desired.....also i dont know how they plan to address the droop screw's...i dont see any protection build in....also a motor plate like how Robert did his....there needs to be a solid mount or the CF would round out over time and cause motor alignment issues if the screw's were ever to come loose...also the motor mount over time will wear itself into the chassis and eventually will need replacing where as Matrix's version its a bolt in plate that can be replaced if needed...Not to mention the replaceable droop tabs and the Front and rear skid's that are replaceable...CF wear's a lot faster then alum and you NEED protection or the chassis wont last a season.
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Old 09-22-2009, 01:27 PM   #19
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Barlarito...

in fact.. the chasis is a plate.. a master piece where the suspension parts must be mounted...

The chasis is a suport for the suspension parts...

The chasis IS NOT a part of the suspension...

Diego.
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Old 09-22-2009, 01:48 PM   #20
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I see what your saying but our cars frequently hit the chassis on the ground. If they didnt they wouldnt be wearing out.

If the shocks were set-up stiff enough that the car didnt slap its chassis then our cars wouldnt handle as well as they do. Thats why there is no real world equal for our cars. The real life buggies cannot do the same speed or jumps to scale without self destructing.

Also FYI I drive a RC8 and the big bore shocks do have a rubber up stop that is part of the shock boot.
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Old 09-22-2009, 02:34 PM   #21
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Quote:
Originally Posted by Dieguito View Post
Barlarito...

in fact.. the chasis is a plate.. a master piece where the suspension parts must be mounted...

The chasis is a suport for the suspension parts...

The chasis IS NOT a part of the suspension...

Diego.

In an all out racecar; in 1:1, this is generally true.

However, things do change in scale for various reasons. Biggest reason being the lack of shock technology. Also, if you actually run a scale and compare tire width/sizes of scale vs 1:1 you'll find that our tires are also relatively out of scale, which contributes as well.

I've had multiple experiences with your idea of "let's stiffen the chassis and let the suspension do it's job"...with an original MBX-4 I added CNC braces running from each diff housing to the aluminum center diff mount. So rear diff to center and front diff to center; all tied together with CNC aluminum beams, basically gave the car a spinal cord. This car was STIFF. Now, on a smooth medium (or even low) bite track; the car was spectacular. It couldn't be touched and drove like an onroad car; super precise and very smooth.

I tried something similar with the next gen. Mugen; MBX4-XR and on a rougher track with more jumps; it was HORRIBLE. I put the standard link back in the rear, allowing more flex, and it calmed down.

Then, with the Jammin' X1-CR buggy (small bore shocks) I went through the same thing. Wound up ditching the CNC rear brace and going to the molded plastic one; same results. Car was smoother, much more fogiving and had more corner bite with the added flex; whereas the car was virtually impossible to drive with the CNC braces installed.


Good luck in your testing, but until you find some better shock technology I think you're going to see why it is a necessary evil in scale racing.
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Old 09-22-2009, 03:02 PM   #22
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+1, on RC cars, especially 1/8th buggy/truggy the chassis is part of the suspension. Xray even offers different hardnesses of suspension parts and chassis plates/components for their current TC cars. They did this on the XB8 buggy too.
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Old 09-22-2009, 04:30 PM   #23
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Quote:
Originally Posted by mblgjr View Post
In an all out racecar; in 1:1, this is generally true.

However, things do change in scale for various reasons. Biggest reason being the lack of shock technology. Also, if you actually run a scale and compare tire width/sizes of scale vs 1:1 you'll find that our tires are also relatively out of scale, which contributes as well.

I've had multiple experiences with your idea of "let's stiffen the chassis and let the suspension do it's job"...with an original MBX-4 I added CNC braces running from each diff housing to the aluminum center diff mount. So rear diff to center and front diff to center; all tied together with CNC aluminum beams, basically gave the car a spinal cord. This car was STIFF. Now, on a smooth medium (or even low) bite track; the car was spectacular. It couldn't be touched and drove like an onroad car; super precise and very smooth.

I tried something similar with the next gen. Mugen; MBX4-XR and on a rougher track with more jumps; it was HORRIBLE. I put the standard link back in the rear, allowing more flex, and it calmed down.

Then, with the Jammin' X1-CR buggy (small bore shocks) I went through the same thing. Wound up ditching the CNC rear brace and going to the molded plastic one; same results. Car was smoother, much more fogiving and had more corner bite with the added flex; whereas the car was virtually impossible to drive with the CNC braces installed.


Good luck in your testing, but until you find some better shock technology I think you're going to see why it is a necessary evil in scale racing.
Thanks for your time to answer me !!!!
As you mention, I'll try it considering your explanation. And we are going to work with a stiff chassis, going to a flex one to find the differences.

Thanks again
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Old 09-22-2009, 06:02 PM   #24
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It's quite simple actually. The shocks dampen bumps/shock in a linear fashion. They can only move in a line. The arms are a flat plane and can only swing around the hinge pin. Both only move in one basic direction. Bumps, jumps, crashes induce force into the car at all kinds of angles.

Angles that the shocks may not be too good at soaking up because they aren't inline with what ever shock is applied to the car.

A softer chassis and arms allow the car to flex.

Think of it this way. A Sport motorcycles suspension is pushed up and down by bumps in the road. When the bike leans over it the suspension still works but some sharp vertical bumps like the gaps between concrete slabs send shock straight up. The bike is leaned over so it can't absorb such a huge shock with its forks, because the shock is coming at an angle that isn't in line with the movement of the forks.

So some sideways flex needs to be desighned into the forks. Yamaha found this out years ago in GP racing that they went a little too far with makeing forks stiffer and stiffer. Eventually they needed to find a way to predict how much flex the fork tubes need. Exactly what frequency the stiffness needs to be tuned to is an art.

Real cars are usually so floppy that they are allway trying to siffen the chassis. A tuned flex losi with its braces sawed in half still has a way, way stiffer resonance frequency than most real race cars. If you could pick a F1 car up with your hands like you can a model. You could bend it just as much.

We have actually used large vibrating pads under a race car set to shake at similar frequencies that the car would see on track. It can show all kinds of problems like rubber motor mounts that are too soft. As you dial in the shakes you get to a point that the engine starts to dance the opposite direction of the car, like Lenny Kravits old hair style.
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Old 09-22-2009, 07:28 PM   #25
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my xray 808 handles better now with a worn down chassis than it did when it was brand new. My car is smooth as silk, and I've been told that several times by almost everyone I race with.
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Old 09-22-2009, 09:00 PM   #26
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I used to use all the hopup alum parts on my cars for durability & it changed the way the car feels esp in corners & blown out tracks. I started putting the plastic cars back on & eventually learned that going back & installing the older less buff parts & my times got more consistent.

It may sound odd but as my chassis wore my cars also felt easier to drive.I now will not even consider any hopups that make my car stiffer.It might be the way I drive & not correct IDK but its what I like.
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Old 09-22-2009, 09:24 PM   #27
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Honda actually took some strength out of the head area and rear swingarm years ago to let it flex some when the bike was leaned over due to the forks/rear suspention not being able to work in a normal manner when the bike was on its side. It ended up working a lot better once this was done, the rick is finding the right amount of flex. There is a fine line between too much and not enough, kind of a give and take.
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Old 09-22-2009, 09:29 PM   #28
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I had the EB4 S3; the chassis was exceptionally rigid and it hurt performance on many surfaces. In full scale cars you want the most rigid chassis you can get because the suspension can handle the work load (coilover and bypass shocks); it boils down to sprung vs unsprung weight.

It goes against all things logical but there needs to be some flex.
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Old 09-23-2009, 02:32 AM   #29
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as mentioned above,

shocks = LF
tires=MF
chassis=HF

shocks by essence cannot soak up HF, as the oil flow through the piston holes becomes turbulent with speed, and they start packing. That's where chassis flex comes into play. Oil damping on articulated chassis (as done on the old Crono Europa cars mid-90's) doesn't make much sense because then you make it a LF tool again.

I have the fioroni "unlockable" rear brace on my mbx6 - on rough tracks, it definitely works better (ie easier to drive for me at least) in the flex mode

The reasoning is very different in onroad - then it's torsional flex that's highly sought after to regain corner speed.

Paul
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Old 09-23-2009, 04:22 AM   #30
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Quote:
Originally Posted by Zerodefect View Post
It's quite simple actually. The shocks dampen bumps/shock in a linear fashion. They can only move in a line. The arms are a flat plane and can only swing around the hinge pin. Both only move in one basic direction. Bumps, jumps, crashes induce force into the car at all kinds of angles.

Angles that the shocks may not be too good at soaking up because they aren't inline with what ever shock is applied to the car.

A softer chassis and arms allow the car to flex.

Think of it this way. A Sport motorcycles suspension is pushed up and down by bumps in the road. When the bike leans over it the suspension still works but some sharp vertical bumps like the gaps between concrete slabs send shock straight up. The bike is leaned over so it can't absorb such a huge shock with its forks, because the shock is coming at an angle that isn't in line with the movement of the forks.

So some sideways flex needs to be desighned into the forks. Yamaha found this out years ago in GP racing that they went a little too far with makeing forks stiffer and stiffer. Eventually they needed to find a way to predict how much flex the fork tubes need. Exactly what frequency the stiffness needs to be tuned to is an art.

Real cars are usually so floppy that they are allway trying to siffen the chassis. A tuned flex losi with its braces sawed in half still has a way, way stiffer resonance frequency than most real race cars. If you could pick a F1 car up with your hands like you can a model. You could bend it just as much.

We have actually used large vibrating pads under a race car set to shake at similar frequencies that the car would see on track. It can show all kinds of problems like rubber motor mounts that are too soft. As you dial in the shakes you get to a point that the engine starts to dance the opposite direction of the car, like Lenny Kravits old hair style.
The only thing I can say is... wow.... thanks to all of you .
Your explanations & examples are very clear for me !

Once again, thanks.
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