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Author Topic:   coil spring rater
donslink1
Dirt Freak

Total posts: 318
posted September 13, 2005 06:31 PM  
Looking to get a spring rater and was wondering what people thought of the different brands and the pros-cons of each of the ones you have used.
And what would be the most accurate with out paying $10,000.00

rocket36
Dirt Freak

Total posts: 209
posted September 14, 2005 02:10 AM  
if you have a set of scales that you weigh your race car on, you can connect just one pad and put it in a press, place the spring in position, compress more than 1/2", zero scale reading, then press another one inch. read your spring rate. pretty easy really and will save some bucks.
i would recomend, for safety, making a mandrel to fit your springs & press head so the spring cannot come out while depressed.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted September 14, 2005 04:36 PM  
I was planning on doing the very same thing myself. Using my scale pads and building a fixture. I was worried thou that there might be some un-foreseen problem and mess up my scales. LOL! Of course I don't see how it could hurt it cause your putting a lot more weight than that with the car but that would be my luck to tear something up! I think my pads are rated at 1500lbs each so I'd never see a spring that heavy anyways.

rocket36
Dirt Freak

Total posts: 209
posted September 14, 2005 09:46 PM  
i tried to build one using a hydraulic pressuer guage with a port-a-power once, but it was very in consistent. i have been using my scales for this ever since (3 years) and it works well. you really start to learn and understand alot about springs once you start playing around a bit.
you modified guys seem to run much stronger springs in the front than we would in our late model, so you would definitley want to make a mandrel of some sort to help locate the spring in the press, so one can't escape while under alot of pressure. if your springs aren't ground flat on the bottom (like a coil-over type) then you may want to try an use a spring cup/platform from an old front arm, top and bottom.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted September 14, 2005 11:47 PM  
got a question for you rocket...why do you say compress it more than a 1/2" then zero?? I'm sure thats to tack up all the slack but the reason I ask is because you say MORE than 1/2" have you found something with that???? Oh, we have to run heavier springs up front because we use the stock locations for the springs, whereas you guys use coil-overs which are mounted much closer to the wheel. (I'm sure you probably knew that but I figured I'd throw that in cause the way you said we "seem" to run heavier springs. Just some FYI) Thanks for the help!!!!

donslink1
Dirt Freak

Total posts: 318
posted September 15, 2005 04:48 AM  
thanks for the ideas but I just want to buy one and I was wondering if a electronic one is worth the money or not, I have seen different types.
Ones with bottle jacks and ones that you scew down
Just wondering what one is the best for the buck.

rocket36
Dirt Freak

Total posts: 209
posted September 15, 2005 05:04 AM  
fly-n-low, the reason you need to compress 1/2" or more is so that a true reading can be taken (the same as the manufacturers) so the spring sort of takes a set. the reason i said or more is simply because you can start your measurement from anywhere really as springs are measured in pounds per inch, so it basically doesn't matter how much the spring is compressed to start with, the next inch will take "x" amount of pounds to compress. this is one of the things i learned by being able to rate springs. putting that into practice is why when you screw down on a weight jacker, the springs rate doesn't change and cannot change, it is simply pre-load or standing height. this is of course assuming we're not checking variable rate (rising rate) springs.
here in australia we don't have modifieds like you guys run (we do have a much more basic modified class called AMCA) so i only really know what i read on here etc. the class seems to be a very good concept though, and i ahve often thought about taking a trip over there and trying to get a drive in one.

donslink1
Dirt Freak

Total posts: 318
posted September 15, 2005 02:31 PM  
Sorry, But I will have to disagree with you rocket. That is why some people run 1/4 preload on a pull bar spring and some will run 3/4 and so on. It changes the first one inch of travel and so on depending on the amount of preload.

rocket36
Dirt Freak

Total posts: 209
posted September 15, 2005 03:02 PM  
take a 500lb spring, compress it any amount, it can not become a 550lb spring.

andykmod
Dirt Freak

Total posts: 351
posted September 15, 2005 03:33 PM  
Say you have a 1100lb pull bar spring and it is not pre-loaded, the spring has no rate at this point right, if you would pull it 1 inch it should be 1100lbs. So you now preload it a half inch which you would hardly notice on a spring rater being that it is within the first inch of travel because the way a spring is wound(the end coils) and you move it 1 inch also. Wouldn't the spring end up being about 1650lb at that point? The spring should increase the rated amount every inch it travels i would think unless it progressive or has a spring rubber in it.

dogwalker
Dirt Full Roller

Total posts: 65
posted September 15, 2005 04:13 PM  
A 1100 lb spring will compress 1 inch for every 1100 lbs. of force. ie. an 1100 lb. spring will compress 1" with 1100 lbs., 2" with 2200 lbs. ect. Preloading is adding initial weight. Just because a spring is preloaded 1/2" does not change the spring rating; it means you added 550 lbs. In the case of a pull bar, it will take an additional 550 lbs. for each incremental 1/2" of travel.

donslink1
Dirt Freak

Total posts: 318
posted September 15, 2005 05:57 PM  
correct, If you put a spring in a spring rater and rocket said you can compress it to anything you want and then compress it one more inch and it will come out the same.
That is not how it works I dont think.

rocket36
Dirt Freak

Total posts: 209
posted September 16, 2005 03:42 AM  
what you guys are saying is correct, and the same as what i was trying to say, maybe my description was not very good.
if you compress a spring to any point, then zero your scales, and compress one more inch, that will be you spring rate.

FlyNLoIMCA17
Dirt Forum Champ
Total posts: 753
posted September 16, 2005 05:54 PM  
I see what your sayin' Rocket. If you don't zero the scales after preload you'll get off readings, but once you zero it the preload doesn't matter! Thanks for the help man!!

rocket36
Dirt Freak

Total posts: 209
posted September 17, 2005 01:43 AM  
correct fly-n-low, sorry for my poor explanation the first time around.

i8uracing
Dirt Roller

Total posts: 18
posted September 17, 2005 08:08 AM  
Pull bar springs can be different. I agree with rocket that a spring rated at 500 lbs/in is pretty linear. But alot of people are using progressive springs on there pull bars. Pre load will change the rate of those.

donslink1
Dirt Freak

Total posts: 318
posted September 17, 2005 12:01 PM  
so your saying you take a 500# spring compress it 2 1/2" then zero out the scale, compress it one more inch and it will read 500#

andykmod
Dirt Freak

Total posts: 351
posted September 17, 2005 12:51 PM  
Don, i think that would be correct. Also you gave me too much money for that shirt. I owe you a 5 bill.

donslink1
Dirt Freak

Total posts: 318
posted September 17, 2005 02:04 PM  
you think so, I am going to buy one and do some testing. I know I gave you too much, dont worry about it, It was real cool you did that for me. Ill bring a DVD player you bring the race videos to chilton, what do you say. I would like to see them

donslink1
Dirt Freak

Total posts: 318
posted September 17, 2005 03:46 PM  
you know what Andy, After thinking about it for a hour or two, I think rocket is right.
Im still going to get one and check it out but it does make sence, SORRY ROCKET

rocket36
Dirt Freak

Total posts: 209
posted September 17, 2005 08:33 PM  
no big deal.
remember the unit that springs are measured in, POUNDS PER INCH, not total carrying capacity before bind.

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