For you engineer types: hot and cold facts

Jack Olsen · 10-29-2002, 04:27 PM

Seeing the current 'wider tires' thread, and fondly remembering the many 'cool collar' threads and 'brake pad friction and heat dissipation threads', here's a problem I'd like you math-and-science guys to answer for me.

Heat-cycling tires and cryo-treating rotors.

I know it's generally accepted that there are benefits to both, but whenever it's explained to me, it sounds an awful lot like ads for nutritional supplements or oil treatments.

The molecules line up differently after a temperature change? Really? But they didn't get around to lining up all nice and stable when the components themselves were being molded/forged/cast/whatever?

I want the Pelican brain trust to explain this or debunk it, once and for all.

makaio · 10-29-2002, 04:35 PM

Very good question Jack. Sorry I can be of no help. But I would like to know what the others think.

ChrisBennet · ChrisBennet's Garage

I don't know the answer but I have a few data points:
1. Cryo treating is used for match rifle barrels last I knew.
2. Castings for some machines (Bridgeport's) are aged to make them more stable before they are used.
3. According to a machinist friend, some tools are hardened using a cryogenic process.
-Chris

masraum · 10-29-2002, 04:56 PM

Unfortunately I didn't pay enough attention in my materials class, but I'm dying to know the answers.

The cryo rotors have always had me wondering.

pwd72s · 10-29-2002, 05:09 PM

Chris? Did you happen to check the article in "American Rifleman" about the cryo frozen barrels? They (the NRA...those horrible non pc folks) did some pretty extensive testing, with both sporting and target barrels. The conclusion I made after reading the article? In the NRA's words..."tests inconclusive". In other words, it might help, but if it does, any progress is indeterminable.
Brake rotors? I haven't a clue. On those, I think perhaps slotted is gaining favor over holes, but even that is up to much debate.
Heating tires? It must work, right? I mean, if they do it in F-1 racing...Me? I sometimes forget to check tire pressure before heading out for a road run.

autobonrun · autobonrun's Garage

In my line of work in oil refining, it is common to heat treat a metal vessel that has been welded on if it is going to be used in an application where there is a danger that the chemical contained in it will attack the metal.

The welding changes the molecular size and structure around the weld. Where the different size and structured molecules meet the unheated metal molecules is a region of instability and weakness. We remove this weak region by reheating the entire piece so that there are no regions where the molecular size is different. This would work for car parts also where the molecular structure has been weakened by a process like welding and could be susceptible to corrosion, like on an exhaust. Fortunately there are not as severe problems with chemical attack as in refining, however, you'll note that the weak point on exhaust systems is around the welds.

Guidelines for heat treating material are published by an organization called NACE, National Association of Corrosion Engineers.

The web site is pretty much limited to members but this is it.

http://nace.org/nace/index.asp

RoninLB · 10-29-2002, 05:24 PM

well, not a pro on this, but I often reduce some equations to something kinda simple minded..if I'm talking to a pro about brain damage, I reduce his complicated explanation to throwing a handful of pennies on the floor..a good unit will jump past some pennies to reach others to complete the circuit..a bad unit will take the easiest path to the closest penny...and if books say poly-urethane paint is stronger than acrylic-urethane paint because it has a longer molecular chain, which I envision as a simple hardware store metal link chain..it becomes easy for me to process that "proper heat cycling" of tires creates longer/stronger molecular chains.......Ron

autobonrun · autobonrun's Garage

Quote:

Originally posted by RoninLB
well, not a pro on this, but I often reduce some equations to something kinda simple minded..[/img]

I agree with you. Simplicity is the best. I am definitely no metalurgist, don't even know how to spell it. But the way the molecular thing was explained to me is that it's like velcro. What makes the velcro stick together is that every little curled piece is exactly the same size and shape. The same thing applies for metal molecules. Same size and shape mean more strength. Or so I was told.

island911 · 10-29-2002, 05:50 PM

Quote:

Originally posted by JackOlsen
. . .I know it's generally accepted that there are benefits to both, . . .

There's the rub.
If you don't have specific knowlege/understanding of the claims being made, you can only rely on "generally accepted" and the twisted twisted logic of a sales pitch. You couple that with people who want there wiz-bang purchase to be the winning horse, and you then have a whole lot of folks who will go to great ends to blindly defend junk.

Debunking products is not popular. Remember the E-Ram? Thom did a great service for those who needed proof; and got slightly abused just for being the messenger.

Most that are in the know of a products shortcomings, don't go down that road. Teaching engineering principles is not an easy thing. (As I said in the tire post, it takes 4-5 years, even for smart guys.) With everyone wanting simple answers; Bill here put up the best post I have seen on this board.

Quote:

Originally posted by wckrause
The Cool-collar works on the principle of thermal conviction. The amount of cooling you get is proportional to the amount of faith you have that it will work. The more you spend on it, the greater that faith. Also, the harder it is for you to install, then greater the faith. Can we have an AMEN!

------------------
Bill Krause

Damn, thats good.

That said; cryo-treating rotors -

Heat-cycling tires - neutral -. ..heat can change the molecular structure, but does it change for the better? YMMV

If you want an engineering degree, I highly recommend it.

Dantilla · 10-29-2002, 05:59 PM

Last Spring our local PCA region had a tech session at Fordahl Motorsports- The guru of gurus of setting up Porsche suspension systems. He explained in detail the importance of a proper heat- cycle of tires, and why it has to be done on the car, not in an oven like Tire Rack does.

Unforunately, I was at an SCCA meeting at the other end of the building, and missed it.

Bill Verburg · Bill Verburg's Garage

Cryo treating rotors is a great profit center for the vendor, a total waste for the end user.

Heat cycling tires is a total different and desireable process.

RoninLB · 10-29-2002, 06:14 PM

Dan..thanks for info..don't feel like I may be wasting my time on heat cycling tires..I think tirerack gives a procedure for "do it yourself"..anyway, I drive new sneakers on Hy. for 20 miles, then jack up all 4s [home lifts are great], leave all 4s in the air for a full day..that should cover my act..but I do it all a second time/911 neurotic personal problem........Ron

82SC · 10-29-2002, 06:20 PM

jack

pick up a copy of the newest POC velocity...there is a whole section on cryotreating rotors

they usually have a stack at the willow springs office

MJ

TimT · 10-29-2002, 06:20 PM

Yikes another NACE member on the board. How many AWS members are hiding too?

The example of heat treating weldments is a good one. Welding imparts stresses to the welded member. If these stresses are not removed, the weldment has what are called residual stresses, these can lead to premature failure of the weld.

To relieve stresses weldments are normalized (normalized or relieving). Normalizing relieves the stresses in the weld metal, and the base metal. Metals can be stress relieved by heat or cryo treating.

Large weldments are pre heated, then post heated. with a controled period of post heat gradually reducing temps to ambient.

I dont know enough about the cryo treatment, but the principles are the same. Whether it benefits a cast iron rotor is debatable.

Heat cycling has something to do with combing the long chain rubber molecules to make them more resistant to the heat cycles they will see (I think). Didnt do well in chemistry...

RoninLB · 10-29-2002, 06:32 PM

Hey Tim...what does "combing" mean..tried the dictionary/nodda......Ron

RarlyL8 · RarlyL8's Garage

I understand the thermodynamics involved in cryogenic metallurgy, but it really doesn't matter. The important issue is that the desired effect that supercooling has on the rotor is not significant enough to warrent the expense. If it were significant you would see it applied in every form of racing. It is not.

As for heat cycling tires, I can see scubbing them in for surface abrasiveness. I don't see how any temperature cycling could significantly change the heat history that the tire sees during the vulcanization process.

TimT · 10-29-2002, 06:36 PM

oops typo combining...

when you said combing I had to think cuz my top end is a little sparse these last few years . I dont think I know where my comb is anyway LOL

Jack Olsen · 10-29-2002, 06:38 PM

" Heat cycling has something to do with combing [sic] the long chain rubber molecules to make them more resistant to the heat cycles they will see (I think). Didnt do well in chemistry..."

That's just it, though. What the heck goes on when a tire gets made? Are we supposed to believe it's a cold process? Do they whittle a tire out of a solid peice of rubber they find in a jungle? My guess is that there's a whole lot of heat involved, under much more controlled conditions than doing fifty loops in an abandoned parking lot (which I just did -- so if my spelling's bad, it's because I'm dizzy). I'll grant that some time has passed since the tire was manufactured, but why would that make a difference in the benefit of a heat cycle? And what exactly happens during the 24 hours of 'cool down' time after a tire gets its first dose of heat?

I'm not ready to say heat cycling tires is folklore. But if it does make the tire better/more durable/whatever, why don't tire manufacturers come up with a way to do it? It would seem that in the ultra-competitive marketplace of R-compound tires, any improvement would become a selling point.

Superman · 10-29-2002, 06:41 PM

It seems to me I recently noticed that someone who has changed a lot of 'tracked' rotors was convinced the cryo-rotors wore no different. I dunno. But I have had the tire experience. Michelin Pilot XGT's. They were slippery enough I complained to Tyson who said they just need some heat cycling. Well you know me, I just hate to open the throttle and load the suspension and mash the brakes but if Tyson says that's the thing to do....

And it made a HUGE difference.

TimT · 06:45 PM

Maybe its economics.... the manufacturer will have you heat cyle and prepare your tires. Instead of them optimising your tires.. heat costs money. let the buyer provide it. Then Hoosier, Goodyear, Michelin etc dont see the heat go up there smokestacks.