#11
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Springs cannot be define by rate alone, the unfitted length is also a big consideration. For suspension to work as well as it could, then both the rate and the length must be right.
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#12
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????
Explain, for dummies. David |
#13
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Let's take a simplified example. vertical spring damper with 400lbs of weight on it. If the spring is a 200lb spring, then it will compress by 2 inches. If it started at 10 inches long, it will now be 8 inches. If, on the other hand, it was a 400lb spring, then it would only compress 1 inch. If it started at 10 inches it will now be 9 inches long. What I am getting at is that the two factors, rate and length are interdependant, and should both be chosen carefully to get the correct ride height and rate. Of course the adjustable spring base can be used to change the ride height, but people should be wary of using up the available suspension travel to compensate for having springs of the wrong length. |
#14
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Quote:
That said, Mr Henderson makes a good point. If I understand it right then for two up each around the 100Kg mark 250's that are a wee bit longer should do the trick then.
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Regards (The mad Sarf Efriken) Last edited by Land Locked : 7th October 2009 at 09:15 AM. |
#15
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I just spoke to Dave at dampertech and it cost £340 delivered
He said i will have them on friday Cant wait to take the the square box out thats been moonlighting as springs and dampers for the last few months since i got my chassis rolling |
#16
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Good to know, cheers
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Sean |
#17
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Sorry Mr H.
I'm struggling with this one... Wouldn't a longer spring wound up to make it stiffer (i.e. shorter) have the same effect as a heavier one? I'm happy with the ride height. It's the bottoming out on humps and bumps I want to stop. Sorry if I'm being thick..... David |
#18
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Quote:
The stiffness is set by the spring rate alone. The length of the spring controls the ride height. Let's ignore the adjustable spring platform for the time being. Let's continue the example from before- vertical spring with 400lbs sitting on it. The bottom of the spring is fixed to the wheel, and the top to the chassis. Let's suppose that the desire ride height is 5 inches. Let's suppose that it is found that if the spring is compressed to 8 inches then the ride height will be correct. So the target is to get the spring length to 8 inches. If a 9 inch 400 lb spring is fitted then that will produce the correct height (in this example). If a 10 inch 200lb spring is fitted it will also produce the correct ride height (because it has been compressed by 400lbs, so it is compressed 2 inches). Now the thing to consider is what hapens if some EXTRA load is imposed, suddenly, such as a bump in the road making the wheel want to go upwards. If that bump was to procude a force of 800lbs (extreme example to make the point), then the 400 lbs sppring would be compressed by 2 inches, but the 200lb spring would be compressed by 4 inches. From that example we can see that the 400lb spring is indeed stiffer than the 200lb spring. If the ride height is changed using the adjuster then all that is changed is the ride height, the spring itself cannot be made stiffer. It won't even be made shorter, as the car will simply rise as the adjuster is wound upwards (until the shock runs out of travel). The above example ignore the change in the corner weight that would happen on a car, in other words the weight on that corner would increase as the ajuster is wound up, but as both rear corners are being considered, that's ok. It's a complicated subject, but the basic principles of springs are straightforward. Mike Capon, who contributes to locostbuilders from time to time, has written a spreadsheet that will enable the determination of the correct spring rate and length if one enters the variables such as the angles dimension and weights. Sorry, I don't have a link to it. |
#19
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Just looked at my invoice and paid £458 delivered from ProtechShocks. Think i'll be going to Dampertech next time. Also just looked at my SVA brake test and Axle 1 weight with driver is 272kg and Axle 2 weight with driver is 298kg so i think the 250 or 300lb/in springs would be more suitable. AndyH |
#20
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Ash said to mention his name from CKC and speak to Dave to tell him he should give me a good deal Not sure if this had any reflection on the price, but i was pleased when he said 340 delivered it is a very good price. He also said if i find the 250 rear springs a little too much, a set of 225 or 200lb springs are only £44 if i want to change them. |
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