Suspension springs vs. Valve springs

[twistedneck]

Hi everyone, being a coil spring engineer i'm trying to broaden my horizons by looking at other industries, in this case automotive coil springs.

I've got some friends who drag race and they go through springs a couple times per season due to huge valve lift, high rpm, large heavy valves, etc..

They all seem to love a nascar associated company called psi springs

http://www.cvproducts.com/cv/products/specItem.aspx?prodID=2245&brandID=61

They do some pretty cool heat treatments and 'air' tool winding, however i'm trying to find out ins and outs and contast to a pick up truck coil over spring for example.

i already found terms like 'beehive' vs. 'double pig tail' etc...

alloys? hardnesses? cold wound? thanks all

Twistedneck.

 

[sbozy25]

Wow this is an area that could take pages upon pages to discuss. My company makes the suspenssion springs for most Nasscar, Indy Car, Truck Racing, and even quite a few drag race teams. The company division name is Hyperco, you can check out their website if you would like...

http://www.hypercoils.com/

I can't really get into any details about how we process our springs, because we try to stay a step ahead of our competitors. However, if you go to the website you can look at the catalog and see what we have, also you can click on the "contact us" link and ask specific questions.

 

[NickE]

Twisted- you also might wnat to get the spring book from one of the other devisions of a company I work for:

http://www.associatedspring.com

 

[twistedneck]

sbozy, i also work for a big coil supplier.. I guess what i'm getting at - how do valve springs and coil springs really differ in peak stress, load loss, etc..

A couple points so far

1. Clean tempered wire is critical for valve springs as most fail due to aluminum oxide inclusions (not sulfide stringers for example)

2. Cold wound is possible on small wire diameters - not possible with larger car / truck diameters without issues.

3. faitgue cycles are much greater with valve springs

4. dynamic issues are a big concern i.e. surge and fuss points.. check out this video of bounce and spintron testing:

http://www.racingsprings.com/movies.htm

I'm not sure what fuss is.. a version of surge? Also, what are the main drivers for double and tripple springs? I realize rate and load are effected, is it coil clearance?

 

[sbozy25]

Ok now I understand your questions, I think.... if I am right in my assumption, since we are talking automotive racing, I will treat coil springs as suspension springs...

1. Yes, clean tempered wire is critical for valve springs, where as you want to go with a high tensile (slightly better than valve quality) wire for suspension of race vehicles.

2. Again, you are correct. For suspension springs we try to not cold coil anything over 7/8" wire diameter. Anything bigger and we have trouble keeping a consistant path which is critical to the performance.

3. Fatigue cycles are greater in the valve springs, this is because the suspension springs are designed for a much higher stress. You really do not need a suspension spring to last more than 1 race. But then again, a lot of teams change their valve springs after ever one as well. But, the suspension spring is designed to compress to just about solid height so the car can get as close to the ground as possible when racing. Because of this, the spring is in just about constant compression for the entire race.

4. From what I can gather with a brief search of the internet, "fuss" was used interchangeable with surge. I have never heard of that term before, but the definition I came across seems to be the same as that of surge. "The point when a spring becomes instable..." And yes these are concerns for valve springs, but I have never heard of anyone really paying much attention to them in suspension spring design.

 

[TVP]

twistedneck,

Kobe Steel is not just the leader in suspension spring steels, but also for valve springs. The following article is an excellent summary of steels for valve springs:

http://www.kobelco.co.jp/technology-review/english/pdf/KTR_26/021-025.pdf

Haldex Garphyttan is one of the leaders in converting steel rods into spring-quality steel wire. They have quite a bit of technical information available from their website. Use the following link for more information:

http://www.hgse.haldex.com/ver02/main.asp?mainDeptID=50

Other good sources of information are SAE Technical Papers and Wire Journal International articles.

Without getting into the particulars of racing springs vs. high volume automotive springs, one can summarize valve spring technology as follows:

1. All springs are cold wound from previously quenched & tempered steel wire.
2. Wire rods are shaved prior to cold drawing in order to reduce surface defects.
3. Wire is eddy current inspected for surface defects
4. High silicon alloys (~ 2% Si) are used to reduce sagging/compression set.
5. Japanese auto companies are specifying the use of gas nitrided springs due to the increased strength and resistance to compression set. After nitriding the springs are shot peened with very small diameter, extremely hard shot to induce maximum residual surface compressive stresses.

 

[twistedneck]

Wow, thanks for those awesome responses.

Reading as much as i could, there seems to be less and less difference between racing suspension coils, valve springs, or high production hot wound springs.

The reason i say this, weight reduction and fuel economy - this is driving the OEM's to higher and higher peak stress, greater need for sag resistance, more important surface preps etc..

Sbozy, i had no idea that racer guys (especially oval track guys) pretty much run solid the entire race! one thing you dont have to worry about is coating removal and corrosion issues. coil clash is strictly prohibited in active coils for production cars anymore.. coating gone, your looking at a recall (been there on taurus and windstar, at least helping mop up).

also, not many springs are in the as rolled condition anymore for the same fuel economy reasons. centerless grinding is going away and turn + burnish is the high volume choice.. i wonder what you racer boys do?

TVP, i'm going through those links today - great as usual.. i'm sure this is going to be a challenge catching up with the latest trends. I supply suspension springs for the japanese, and i'm wondering if they will ever want to gas nitride the surface? hmm.. for us hot wound folks, gas nitriding is not necessary as our surface is pretty darn good and 'squeezed' if you know what i mean.

last, did you guys check out those videos? crazy how the surge and 'fuss' looks under high speed cam. looks like its made from rubber!

 

[sbozy25]

Yeah the videos looked rather intense... I also was amzed that they look rubberish.

Well, on our racing springs we really do not do a bunch as far as surface preperation. We do have strict requirements on surface defects of the wire, but other than that we run them as rolled. The only reason we do not have much done to the surface, is because we peen the multiple times, and any of those surface treatments would become null and void. However, we do have a few customers that require the wire to be electropolished with certification. Personally I think this is a waste of time, but if they want to pay for it, I suppose it is no big deal. Now, when we get into our hot coiled springs, yeah we either have the bars turned and polished, or we will centerless grind them in house (we have 5 centerless grinders in house).

What is funny, is yeah we do not have to coat the racing springs, but we do have to coat the drag racing springs. Those racers seem to be hell bent in thinking that the springs will rust and break within a day of racing. Sometimes ignorance makes me smile!

 

[TVP]

sbozy25,

Just out of curiosity, what type of coating is used for drag racing springs?

 

[sbozy25]

Powder Coating