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 Post subject: Squat
 Post Posted: Sat Sep 01, 2007 9:02 am 
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Hi guys

I have been reading Billy Shope's Blog (s**t hes smart).   He talks about squat and says that squat isnt desirable and we should tune so we have neither squat or lift.

I presume that if the car is squatting then the time it takes to go from the normal sitting position to the squat position is time we loose from acceleration.  Correct

If so then what do we do to reduce squat, move the ic further forward and maybe harden the shocks?

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 Post Posted: Sat Sep 01, 2007 10:14 am 
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 Post Posted: Sat Sep 01, 2007 11:50 am 
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Here's a couple of vids of my car leaving, same track, same lane, same day.  

Note that the view from the pass. side shows no seperation or compression but the drivers side has seperation even with the anti-roll setup.  

Yup, you can hear the tire spin!  And these two were the good ones!  

http://kenrutledge.com/movies/rox1.mov

http://kenrutledge.com/movies/rox2.mov

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Last edited by Ken0069 on Sat Sep 01, 2007 3:30 pm, edited 3 times in total.

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 Post subject: Re: Squat
 Post Posted: Sat Sep 01, 2007 12:47 pm 
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Clinker wrote:
Hi guys

I have been reading Billy Shope's blog (s**t hes smart).   He talks about squat and says that squat isnt desirable and we should tune so we have neither squat or lift.

I presume that if the car is squatting then the time it takes to go from the normal sitting position to the squat position is time we loose from acceleration.  Correct

If so then what do we do to reduce squat, move the ic further forward and maybe harden the shocks?


When a car squats the tires are unloading, thats why you don't want squat. Separation is bad because when it stops separating, it unloads the tires. When a car accelerates it transfers weight to the rear which will compress the springs/shocks, the 4-link or ladder bars are trying to separate the rear suspension. When these two forces are balanced, you have neither squat or separation. It is unlikely you have neither during the entire launch because these forces are constantly changing.

It is VERY DIFFICULT if not impossible to see what is happening with the eye watching the run live. Video tape it and watch it in slow mo or frame by frame and you will see what is really happening. Data recorders with travel sensors on your suspension would be a great help too.

Rick


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 Post Posted: Sat Sep 01, 2007 1:57 pm 
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Vids won't work Ken #-o

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 Post Posted: Sat Sep 01, 2007 3:01 pm 
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Hummm, I did a couple of these before and they worked then?  Guess I'll have to check with my "puter expert" to see what the problem is!  That was 25 MB of uploads at 3kbps.  Took a while!

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 Post Posted: Sat Sep 01, 2007 3:33 pm 
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Billy Shope is a smart guy. His blog is based on physical law. We can't change physics, we can only use them.

The problem with Mr Shopes blog is, it uses 3 dollar words and a lot of us have 2 dollar educations. Now that don't mean that a 2 dollar education isn't smart, as we all know, it just presents problems in understanding things in some forms. Then there is the math problem. Although I did well in algebra, that was 50 years ago. Now I look at the same kind of equation with a blank stare. It is true, if you don't use it you lose it. Some of the smartest men I ever knew only had a grade school education. They. not only had the laws down pat, but had a ton of experience, because experience was their learning tool.

I keep rereading his blog and find more sinks in all the time. The laws of physics back up what we know and believe. A couple really good things in there are asymmetrical adjustments, and his chassis dyno, and how to find instant center hight. These could be real time savers if understood.

I think it would be a great idea to discuss Billy's blog and take it down to 1 dollar education words and check book math. That way more could benefit from his knowledge.

If anyone thinks this is a good idea, I will contact Billy Shope and get an ok to do it. Who knows, he may wish to participate.

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 Post Posted: Sun Sep 02, 2007 1:34 pm 
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OK, I got it now.  Some dumbass let capitol letters get into the file name and then didn't post the link with those same caps.  OOPS!  O:)

Try this.

http://kenrutledge.com/movies/rox1.mov

http://kenrutledge.com/movies/rox2.mov

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 Post Posted: Tue Sep 25, 2007 7:04 am 
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Bubstr wrote:
The laws of physics back up what we know and believe.


Yes, our observations are always in agreement with the laws of physics. Unfortunately, we can occasionally misinterpret our observations and come up with wrong conclusions.

A case in point involves the location of the rear suspension instant center forward of the rear axle. Suppose the lower links remain horizontal and we move the IC by angle adjustments of the upper links. As we move the IC forward, we observe that the lift at the front, during launch, increases. We might then conclude: The further forward the IC, the greater the front end lift. This is an example of observation misinterpretation leading to a faulty conclusion.

The reason for the greater front end lift, when the IC was moved forward in the situation described above, was because the IC was moved to a location which decreased the anti-squat. As anti-squat is decreased, the rear of the car squats more and the front end rises more during launch.

When viewed from the side of the car, lines of constant anti-squat  can be visualized as a Japanese fan, with a common intersection at the rear tire patch. The line with a slope equal to the ratio of the center of gravity height to the wheelbase is the 100% anti-squat line. Those lines with lesser slope have less that 100% anti-squat; those with greater, more.

The IC location is found at the intersection of lines drawn through the upper and lower link pivot points. So, if the lower links remain horizontal, the movement forward of the IC would have placed it on a line having decreased anti-squat. But...consider this carefully..., if the lower links had also been involved in the adjustment, it would have been possible to move the IC forward the same amount and have DECREASED front end lift. This would be because the IC would have been moved up to a line having GREATER percent anti-squat than before the adjustment.

Bubstr wrote:
I think it would be a great idea to discuss Billy's blog and take it down to 1 dollar education words and check book math. That way more could benefit from his knowledge.

If anyone thinks this is a good idea, I will contact Billy Shope and get an ok to do it. Who knows, he may wish to participate.


The goal of technical writing is to communicate. And, if I'm not doing that, I'm not a very good technical writer. (If you'll recall the last time you installed software or attempted to assemble an entertainment center, you must realize that I'm not the only one who has trouble communicating.) I try to "aim" my material to the non-engineer. I really do! But, at the same time, I don't want my engineering friends to find that I've introduced errors as a result of any simplifications. It's not easy! For instance, an engineer could jump on me for my statement above that the lines of constant anti-squat intersect at the rear tire patch. Actually, because of the weight of the rear axle assembly, they intersect an inch or so below the tire patch. Big deal!

I can only suggest that, if one reading my site doesn't understand something, please call or fax at the number on the home page. As a result of that contact, I might be able to clarify it for others.

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 Post Posted: Tue Sep 25, 2007 12:51 pm 
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Nice to see you in here Billy Shope. Welcome.

I have always maintained that how far out or in the instant center was, as long as the % stayed the same as to hight, (as you stated a same plane as the center of gravity to the wheel base) It did the same work, but there was a slight difference in how quick it does that. If set correctly for a drag car, this should be a non issue, as there should be little to no compression or separation.

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 Post Posted: Tue Sep 25, 2007 1:27 pm 
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Please define "unload?"

As in unloading the tires?  I think I understand the concept, but it sure can't hurt to ask.

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 Post Posted: Tue Sep 25, 2007 1:48 pm 
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Margaritaman wrote:
Please define "unload?"

As in unloading the tires?  I think I understand the concept, but it sure can't hurt to ask.


think of it as down pressure on a tire. If you lose this down pressure or don't have the ability to get transfered down pressure, you have unloaded a tire.

Put you hand flat on the desk in  front of you, press down and slide it to you. Now don't press down and slide it to you. You just unloaded your hand and it slides easy. Loss of traction. You will notice if you do this several times, you can feel a little heat in your unloaded hand. This is energy that could have propelled you car turning to heat.

If and when you see a wheel going up into the wheel well, it is in fact unloading. Some would say it's weight transfer, but if it is, it stopped transferring when the suspension on that side unloaded the tire.

There is another way to unload, If you was ever in the military, think of the push ups where you clapped your hands in between each one. Yep you unloaded both hands.

This is why separation or compression is not good.

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 Post Posted: Tue Sep 25, 2007 2:24 pm 
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Bubstr wrote:
Put you hand flat on the desk in  front of you, press down and slide it to you. Now don't press down and slide it to you. You just unloaded your hand and it slides easy. Loss of traction. You will notice if you do this several times, you can feel a little heat in your unloaded hand. This is energy that could have propelled you car turning to heat.



But my desk is covered in oil.  8-[

That makes does make sense though. \:D/


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 Post Posted: Tue Sep 25, 2007 3:27 pm 
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Jeff on a ladder bar suspension this might be more noticeable than on a 4 link car.  When you hit the tire, the ladder bars tend to react and lift the body of the car.  When they have lifted as far as they can go then some amount of pressure is lost on the tire and the tire will start to spin sort of like Bubstr's push up thingie.  Then the body falls back down and the cycle is started all over again.  The way to stop this on a ladder bar car is to slow down the lift part with the shocks and also by moving the IC up or down.  I would guess that the ideal thingie there would be to slow rear suspension travel down where it takes as long as the car needs to get moving before it runs out of lift.  On 4link cars that are setup correctly you don't see a whole lot of body to suspension movement.  On my car most of the rear movement is because the sidewall of the tire collapses causing the whole car and rear suspension to drop down.  In the videos there is no up or down movement on the passenger side but a slight amount of separation on the drivers side, which is probably caused by engine torque.  

So if you're at the track and you're watching some of the ladder bar cars going up and down in the rear during launch, then that is what is known as unloading the tire.

BTW, the 4 link adjustment I made a couple of weeks back is doing that on my car now.  The tire is unloading about 4 ft off the starting line.

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 Post Posted: Tue Sep 25, 2007 4:01 pm 
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What's your  opinions of my car leaving?  Thanks..Click on full size for better view.

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