|
Post by ryansmith on Nov 6, 2011 13:56:36 GMT 12
gahhhh another thread hijack sorry ryan... no guns this time though lol nah it's allgood go for gold, hahaha yeah..
|
|
|
Post by mikuni on Nov 8, 2011 20:50:20 GMT 12
springs are engineered items in my opinion. of course they are and suspension is not an area that should be taken lightly. It is perhaps the most important part of a vehicle, as without the suspension maintaining contact of the wheels to the road in a reliable manner, other "important" things such as tyres and brakes have no chance at functioning correctly for obvious reasons. The engineering behind springs is quite simple, a length of steel that bends, whose properties can be easily calculated with a few key parameters. Length, steel diameter, coil winding diameter and spacing. There are a number of calculators on the net that allow you to work out the spring rate of a given spring. This is one supplied to me from oldschool.co.nz which is easy to use and gives values in metric and imperial. www.pontiacracing.net/js_coil_spring_rate.htmYou may still need to change the output to kg/mm for people in this country to understand it you. As far as the fundamentals behind whether it will work on the road or not, it is a little simpler. Getting it handling is a whole different ball game. On the road you need a pliable spring rate that is suited to the valving of the shock absorbers. It is something that can be moved from soft to firm depending on what you want from the vehicle with regards to a comfortable ride or sporty handling. As far as legality goes, the main areas that must be complied with are ground clearance and travel, while maintaining spring captivity of springs at all times. Compressing a spring doesn't change its rate, as it still carries the same properties as it did to begin with. The problem being, is that now you have a much shorter spring. Not only will you need to shorten the shocks to keep it captive, the car will be sitting closer to the road with a reduced ride height, but still have the original relatively pliable and soft spring rate. This will cause it to handle poorly, hit the bump stops on big bumps or under heavy forces (cornering/braking) and worst of all, sit on the ground when carrying passengers.
|
|
|
Post by mcqunt on Nov 8, 2011 22:14:16 GMT 12
springs are engineered items in my opinion. Compressing a spring doesn't change its rate, as it still carries the same properties as it did to begin with. Sorry brad thats wrong to compress a spring you have to change its initial metalurgical structure , when this happens it significantly decreases the strength and useable lifespan of the spring, hence they collapse more often than not after compressing, even with retempering the original spring rate and material properties cannot be retained.
|
|
|
Post by opelmantagsi on Nov 8, 2011 23:07:34 GMT 12
yes I agree, reset springs can sag. but its only one of two engineered options
1) reset the spring by a reputable specialist 2) buy aftermarket ones that are engineered specifically for that vehicle
Yes Brad your correct on the legality issue, I have had that discussion with a WOF inspector and as long as they are captive then that's all that matters to satisfy current NZ codes. I understand the spring rate calculator, that's all good but with wishbones there are still further calcs needed to work out what the final ride height will be, touched on that before.
Don't over do it with the resetting is another consideration, I have only ever gone with a final ride height adjustment of -25mm.
Resetting a spring needs to be done by a specialist and involves
heat the springs to make them pliable
adjust / reset the spring while hot
quench hardening to achieve the optimal combination of strength and ductility
tempering to achieve finished hardness to resist sagging but be ductile enough to prevent breakage
shot-peened to induce favourable residual stresses in the outside surface of the spring and helps avoid cracking
scragged to improve their elastic limit and induce more favorable stresses
Once scragged, the springs are checked to ensure they’ve shrunk to the appropriate free length. The scragging process typically reduces the free length to within a couple of millimeters of the desired length
Powder coat or paint to finish
My point is that cutting springs just does not make sense to me, if I cant get off the shelf lowering springs specifically for the car, I would rather have the originals mildly reset than try to use springs out of another type of car just because it looks about right or resort to cutting the springs.
|
|
|
Post by gordo on Nov 9, 2011 1:49:23 GMT 12
Compressing - heating, comressing and retempering, will reduce the spring rate - soften it - in proportion to the shortening. One may not even need to know the initial spring rate if one knows what change one requires - I used to cut 1 1/2 coils from my front springs as it gave a 15% increase in spring rate with, IIRC, a 1" drop. I didn't do the rears as they'd no longer be captive and I preferred the rear to be a bit soft for autocross, gravel events and the like.
Basic rule of thumb - more coils will mean the spring is softer, proportional to the coils and the spring will be softer in proportion to the coil diameter* As the tortion resistance of a round wire is in proportion to the FOURTH power of the wire diameter, the spring rate will be in proportion to that.
EG, going from 10 coils of the same wire for the same overall free length, the spring will be 25% stiffer with 8 coils. Using 20% thicker wire with the same number of coils, diameter and length, the spring will be 1.2^4 = 1.2x1.2x1.2x1.2 = 2.07 times as stiff.
Most important things, as some of you have mentioned, is that the spring ends match the seat, the spring diameter is correct for the seats and, of course, that the spring is held in place in full droop.
|
|
|
Post by mikuni on Nov 9, 2011 7:00:30 GMT 12
We'll agree to disagree ;D
|
|
|
Post by ryansmith on Nov 9, 2011 7:13:50 GMT 12
Cutting them seems the easiest option to get the height you want, and from what i've seen here on this page either way, if cutting or compressing, there is downsides and positives to each. Might see how my springs bed in then see from there if it is sitting how i want it, back seems fine just the front is above the tyres, would like there to be no gap and the car to sit level.
|
|
|
Post by mikuni on Nov 9, 2011 7:42:36 GMT 12
Cutting them seems the easiest option to get the height you want, and from what i've seen here on this page either way, if cutting or compressing, there is downsides and positives to each. Might see how my springs bed in then see from there if it is sitting how i want it, back seems fine just the front is above the tyres, would like there to be no gap and the car to sit level. If you were to cut them, you could do what I have done in the past and have the end of the spring heated, bent to flat and the whole spring retempered. This means the spring will still sit correctly in the seat and the only other thing to watch is that it remains captive, which it should do in the front of a Chevette with the double wishbone setup. It does cost extra, but it is much cheaper than custom springs and you should achieve a good spring rate at your desired ride height.
|
|
|
Post by ryansmith on Nov 9, 2011 8:07:40 GMT 12
Thats what i was thinking, my old man won't be impressed with my thoughts of cutting and or re heating ha ha! spose i should wait and see what the ride height is like when it beds in surely. Or out comes the gas axe/grinder.
|
|
|
Post by zep on Nov 9, 2011 8:40:56 GMT 12
Brad, what did you pay for that process...? With the SSRs I want to come down about 1/2 an inch in the front and am not keen to buy new springs just for that.
|
|
|
Post by opelmantagsi on Nov 9, 2011 9:40:04 GMT 12
Cutting them seems the easiest option to get the height you want, and from what i've seen here on this page either way, if cutting or compressing, there is downsides and positives to each. Might see how my springs bed in then see from there if it is sitting how i want it, back seems fine just the front is above the tyres, would like there to be no gap and the car to sit level. If you were to cut them, you could do what I have done in the past and have the end of the spring heated, bent to flat and the whole spring retempered. This means the spring will still sit correctly in the seat and the only other thing to watch is that it remains captive, which it should do in the front of a Chevette with the double wishbone setup. It does cost extra, but it is much cheaper than custom springs and you should achieve a good spring rate at your desired ride height. I dont have a problem with this suggestion Brad as it involves the retempering process used to reset the springs. I think Ryan is thinking he will simply heat and bend with the gas set, which isnt want I think Brad is inferring? Its all good debate guys and interesting to hear your opinions, all positive stuff as it gets the brain working. I dont mind being proved wrong either, we all have an opinion or understanding, many times I have been proved to be barking up the wrong tree but will be the first to say I have Barry Whiteed up if I can be convinced I was on the wrong track, I think everyone has raised valid points on the subject and its good that we can share these on the forum as it does help everyone get a better understanding in the long run.
|
|
|
Post by mikuni on Nov 9, 2011 12:27:14 GMT 12
By all means you can cut and reshape with heat at home, but the retempering process will likely need to be carried out by a professional Ryan. Basically a big kiln/oven when they heat the entire spring up to a given temperature and cool it back down to restore to metallurgical properties. Brad, what did you pay for that process...? With the SSRs I want to come down about 1/2 an inch in the front and am not keen to buy new springs just for that. I can't remember now, but it wasn't as cheap as I was hoping. Around the $150 mark. Sure custom springs were around the $200 mark but I don't trust the guys down here to get everything right, as I've seen a few issues even with resetting or compressing springs over the years.
|
|
|
Post by ryansmith on Jan 17, 2012 18:12:02 GMT 12
dug these up, sound stream 900w 12' sub, 1400w soundstream amp, 2 6x9 soundstream speakers from pioneer 280w amp, pioneer head unit, running off a huge truck battery ;D
|
|
|
Post by cul8r on Jan 17, 2012 18:46:49 GMT 12
nuts, thats a super tidy install! Im impressed!
|
|
|
Post by crazytim on Jan 17, 2012 22:56:50 GMT 12
COULD SEE IF MY MATE STILL has surplus Tarantula Sub Grills... good if you wanna chuck a bag in there although u do have back seat... just good protection. He used to be part of TEAM STREAM with a V8 Nissan Patrol featuring 4 x 15s, Goliath Amp (worth 10k back then) was fikn mean till the fire...
|
|