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2 stage pistons...Do they work?

2 stage pistons...Do they work?

Old 11-21-2011, 07:15 PM
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Originally Posted by mattnin View Post
Manning, there are several sites that explain how to set the bump and rebound. Just google "setting bump rebound". Most of them say almost the same thing Race Car Vehicle Dynamics say though (they even paraphrase that book and give no credit!) Regardless, here is a site that gives a list of instructions http://www.bimmerhaus.com/tech/shocktuningTN.html

Like Fred Swain does, set the springs first, but then here some do it differently. Some instructions list to set rebound first and some like RCVD say to set bump first. I suggest that if you flip the pistons, to set bump first because you don't really want to drill out anything just yet. After bump is set, drive it around and see if it rolls right. If it rolls too slowly, you can drill out the rebound piston, but if it rolls too much, not really sure what you can do. You certainly would want heavier oil though, even if bump is already too stiff. Is there a way to drill out the bump a bit and go to a heavier oil to keep the bump coefficient about the same?

-Matt

if you're going to discuss this issue, then make a new thread about it, this thread is in regards to v2 shocks.

secondly, you've avoided anything said to you but that's ok. don't pollute this thread with your hypothetical theories, again, make your own threads for that.

time to get back on topic.
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Old 11-21-2011, 08:18 PM
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Originally Posted by SourDieselX View Post
if you're going to discuss this issue, then make a new thread about it, this thread is in regards to v2 shocks.

secondly, you've avoided anything said to you but that's ok. don't pollute this thread with your hypothetical theories, again, make your own threads for that.

time to get back on topic.
AGREED!
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Old 11-21-2011, 08:20 PM
  #843  
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On that note. I have the SC10 4x4 Pistons coming.

I was wondering if anyone had some information for me on what they've tried for an indoor clay track? It medium size and high bite!

I was planning to start with Marcus's setup and possibly even get the Exotech chassis but it occurred to me that he ran his most recent setup outside so there should be some differences.

Thanks!
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Old 11-21-2011, 08:34 PM
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Originally Posted by Oso Negro View Post
On that note. I have the SC10 4x4 Pistons coming.

I was wondering if anyone had some information for me on what they've tried for an indoor clay track? It medium size and high bite!

I was planning to start with Marcus's setup and possibly even get the Exotech chassis but it occurred to me that he ran his most recent setup outside so there should be some differences.

Thanks!
The outside track he runs at, i.e. mikes, is smooth and has good grip, so i would assume his setup should work well indoors. His truck looked pretty freakin dialed lsat friday!
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Old 11-21-2011, 10:58 PM
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Originally Posted by symmetricon View Post
The outside track he runs at, i.e. mikes, is smooth and has good grip, so i would assume his setup should work well indoors. His truck looked pretty freakin dialed lsat friday!
agreed, the truck was definitely dialed in!
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Old 11-22-2011, 04:35 AM
  #846  
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Originally Posted by SourDieselX View Post
agreed, the truck was definitely dialed in!
couple of questions:

is Marcus using a saddle pack with the exotech chassis? Their website says saddle pack configuration "coming soon"


where are you guys getting your clutch baskets?
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Old 11-22-2011, 05:52 AM
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He is using saddle packs, and the rest reguarding his slipper assembly is top secret. But from personal experience, I have not had to use the clutch basket, only the garodisks with the pin mod.
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Old 11-22-2011, 06:08 AM
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Originally Posted by mattnin View Post
Manning, there are several sites that explain how to set the bump and rebound. Just google "setting bump rebound". Most of them say almost the same thing Race Car Vehicle Dynamics say though (they even paraphrase that book and give no credit!) Regardless, here is a site that gives a list of instructions http://www.bimmerhaus.com/tech/shocktuningTN.html

Like Fred Swain does, set the springs first, but then here some do it differently. Some instructions list to set rebound first and some like RCVD say to set bump first. I suggest that if you flip the pistons, to set bump first because you don't really want to drill out anything just yet. After bump is set, drive it around and see if it rolls right. If it rolls too slowly, you can drill out the rebound piston, but if it rolls too much, not really sure what you can do. You certainly would want heavier oil though, even if bump is already too stiff. Is there a way to drill out the bump a bit and go to a heavier oil to keep the bump coefficient about the same?

-Matt
Actually, what I meant to say was tune for the setting where the pistons are locked up first, so that would be rebound, not bump. The only reason I say this is because oil changes or drilling during this step affects both bump and rebound. After this step, you can do a change just changing bump when the pistons separate. So I guess it may be a good idea to tune for body roll first. It may even be a good idea to remove the roll bars during this step.
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Old 11-22-2011, 06:56 AM
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Here I found a graph of a motorcycle racing shock. Even a motorcycle racing shock has about 1.5 times more damping resistance during rebound than bump. This is from the Penske website http://www.penskeshocks.com/files/89...ies_Manual.pdf



How to interpret this graph:

If for example, you take the damping coefficient at 4 in/s, it is 200lbs for compression, or 50 lbs-s/in. The damping coefficient for the same shaft rate of 4 in/s during rebound is 260lbs, or, 65 lbs-s/in.

You can use these numbers to calculate shaft speed for the same amount of force applied. Since p = damping coefficient, and the formula is p=f/v, solve for v = f/p.

If you apply 200lbs of pressure both ways, during compression the shaft will move at 4 in/s. At rebound, v=f/p = 200lbs/65lbs-s/in = 3.08in/s

Last edited by mattnin; 11-22-2011 at 07:18 AM.
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Old 11-22-2011, 07:06 AM
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Seriously mattnin, please give it up. This thread is not for 1:1 scale cars and motorcycles. You assume the assumptions in the algorithms used to determin bump and rebound in a 1:1 scale vehicle are the same in an rc car, they are not. You cant use the same algorithm applied in determining flight charictaristics of a paper airplane to a jet, or vice versa. There ar far to many different variables for the arguent to translate equally.
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Old 11-22-2011, 07:36 AM
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Originally Posted by MantisWorx View Post
so if slower rebound is the way to go then why do Motocross and Real shortcourse trucks use faster rebound?
Originally Posted by MantisWorx View Post
Im not new to this either guys, pro mx, SCCA and pro drag racing! Rebound has to be faster to get the chassis back,to level as quick as possible to get ready for the next obstacle.

There are plenty of books on this as I have a few of them and they all claim the same facts as what I am saying, rebound is always quicker and usually a 3:1 ratio in most situations.
Originally Posted by MantisWorx View Post
or maybe you can explain how EVERy motocross team on the planet sets their suspension up with quicker rebound. i kinda think you may be confused on rebound. and no my numbers are not mixed up its 1:3 im looking at a setup sheet for an arena truck right now thats going to race on a very bumpy track this weekend.
I am not the one who made that assumption symmetricon.

You may be right, RC shocks might require faster rebound than bump but I'm not so sure about that
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Old 11-22-2011, 07:54 AM
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Originally Posted by mattnin View Post
Here I found a graph of a motorcycle racing shock. Even a motorcycle racing shock has about 1.5 times more damping resistance during rebound than bump. This is from the Penske website http://www.penskeshocks.com/files/89...ies_Manual.pdf



How to interpret this graph:

If for example, you take the damping coefficient at 4 in/s, it is 200lbs for compression, or 50 lbs-s/in. The damping coefficient for the same shaft rate of 4 in/s during rebound is 260lbs, or, 65 lbs-s/in.

You can use these numbers to calculate shaft speed for the same amount of force applied. Since p = damping coefficient, and the formula is p=f/v, solve for v = f/p.

If you apply 200lbs of pressure both ways, during compression the shaft will move at 4 in/s. At rebound, v=f/p = 200lbs/65lbs-s/in = 3.08in/s

you guys are forgetting one MAJOR issue and that is spring force. on a 3500lb truck with springs that relate to over 1000lbs of force of course you will need more damping on the rebound to compensate for that, our tenth scale springs are nowhere near that type of force therefore, it simply is not the same our springs do not "Spring back" near as quick or with as much force as a 1:1 car. and most of the 1:1 cars use progressive springs and valving that also controls the fluid rates on the inside, we dont have that luxury.divide everything by 10 and see what happens. and once again guys try them first and THEN come back and comment, right now you are all just quoting paragraphs with no real experience. i have actually tried it during testing and it simply doesnt work as well as quicker rebound and this holds true even to this day. i am currently tuning my dex210, there is a washboard section on the back corner and with my 4 hole 1.1/1.2 20wt combo in the rear it keeps bucking the rear up and is not stable at all where as on my SC i can literally punch through it and gain positions over anyone who is not running the pistons. so i opened up the lower holes to 1.3 went down to 17.5 fluid and it now floats through like its supposed to! so in effect what did i do, i quicken up both but i quicken up the rebound more. i will say that yes if your rebound is too fast it can definately be counter productive there is no argument there. if you look at the video on my homepage there is a shot of the buggy going down the straight from the rear, it actually has too much rebound.
http://www.youtube.com/user/Mantiswo.../4/vGop6ZpNMQ8
there is another shot of the car coming straight towards you and on that shot i slowed the rebound down via smaller rebound holes and you will notice on that shot the the car floats. so right there we have some proof of what the effects are.
another video on my channel shows a 1.0/1.1 combo
http://www.youtube.com/user/Mantiswo.../3/E3P-0GBUaRs
this was during some prototype testing and these pistons were designed for a smoother track. as you can tell the truck bounces around ALOT it was controllable but with the slower rebound all you see is air under the tires and that means less traction!

on this video the truck weighs more and has 1.1/1.2 holes with looser piston clearances and 25/20 oil as you can tell the truck is much smoother and has much more traction in all aspects. the truck on this video is over a second quicker per lap(1.7 on fast lap) than the other video my avg time was better than the quick time on the other vid.
http://www.youtube.com/user/Mantiswo.../0/MjlWBzWNjkE

so you guys that want to test slower rebound please take some vid its much easier to see whats going on than to just talk about it!
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Old 11-22-2011, 08:08 AM
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Personally, I can't wait to try them out . This is the most excited I have been about RC in a while!
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Old 11-22-2011, 08:14 AM
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Originally Posted by mattnin View Post
Personally, I can't wait to try them out . This is the most excited I have been about RC in a while!
they will go out today priority, but because of the holiday you probably will not get them until sat or monday.
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Old 11-22-2011, 08:25 AM
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The biggest thing being forgotten when it comes to compression vs rebound rates is gravity.
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