Your GM engineer kind of agreed with my post saying parts were designed to last x number of cycles, huh? Did he say how many cycles the Cup cranks should last? If the crank is going to break, let it be during the winners burn out! I hope he didn't do Gibbs' cranks.

I'm not quite sure I understand your "strong metal" question.
Like people, it's all relative.

Why don't we have 98 lb. guys playing defensive tackle for the Lions? Because they, while people, aren't physically suited to the job. Same thing with material choices. Choose the material that meets all of your criteria for strength, durability, cost, availability, etc. A part (not just the material) is strong enough if it does the job for its intended life and doesn't fail. Easier said than done, however.

BTW, Reggie Bell was an Associate Prof. when I knew him. He's probably 70+ now.

 

Yes he did actually say that. He siad "if it can go longer, its too heavy." He works with the 4 GM supported teams- so lets hope they aren't Hendrix's (hendricks?) cranks


JB-
check your email. We just built a new ME wing that opened this term or last term. They are naming it after him.

Prof Bell still teaches. Still no phone, computer or pager- It keeps him away from his students.

 

I am very interested in the non-destructive inspection techniques and equipment they use to determine how much fatigue the crank has experienced after 1 or more races. Please ask you source if he will share that information. I have a need. PM if you wish. TIA

 

Re-using internals on a Winston cup car is "unheard of" according to our guest speaker. Pardon me if I take the word of a first hand source rather than that an internet superhero's friend's old boss. Unless you have some kind of documentation of this, I’m stick by what seems logical to me and the first hand source. No offense to your friends or their former supervisors.

 

And an observation: I once saw two pallets of cranks in transit. They were headed for a professional drag race team. Looked like there were 20 on each pallet. I dunno, but I'd guess this was not more (and maybe less) than one season's worth. Must have been close to $100,000 in cranks. I can't imagine they like to replace more than they have to, but OTOH, they can't afford too many failures. It would be interesting to know if they replace them on a schedule, just do some sort of a visual inspection, or have some more sophisticated way of testing them.

Rich Krause

 

My manufacturing company produces some very highly-stressed 4340 shafts used in multi-thousand hp drag racing engine superchargers. We do everything we can to increase their lifespan, which is measured in minutes, at most. Even though the blower is only a small fraction of the cost of the driveline, if it goes toes up in a run, the effect is the same as if the engine gernaded.

I am unaware of the techiques your source uses to assess fatigue life, and thought he might share. There should be no conflict of interest. Isn't Advanced Tech a place where this kind of info, which I think is advanced, can be disseminated to folks who can use it in racing engines? I suggested the PM only if the equipment was proprietary enough to warrant non-disclosure to the internet in general.

quote:
I'm just not a nice guy and even though my time is spent safeguarding information that would compromise our country and it's citizens, I'm beligerent and untrustworthy.... or so you would be lead to believe.

I knew part of that...the part about your job, anyway.

 

Most intereresting information. I was surprised by some of it.

Increasing strength "up to 50%" by cryotreating metal seems high to me...by at least a half-order of magnitude.

290,000 psi is about double the strongest Ti alloys I am familiar with. Exactly which alloy is this strong?

Sometimes the highest strength metals achieve is in pure compression, but not in tension and bending. Bearing rollers or ***** aren't made of exotics, but because they are hardened to over Rc 60, they can have 350,000 psi compression strength. You wouldn't want to use them in bending, however.

CF gearboxes have been a big challenge in F1, as you know. They aren't universal there yet. As I recall one of the top teams still uses metal, and they have more money than the Almighty. Untimate fibre strength isn't necessarily everything.

AFAIK, halfshafts on F1, and virtually all high-powered open-wheel cars are some form of steel. Even some of the CF rear suspension links were replaced with metal when a cracked exhaust pipe allowed exhaust gasses to soften and fail the CF link.

My $.02

 

Jon, I’m not sure that I’m getting you point in your last reply to me, so I’m trying to clarify (sorry if I got long winded):

Not significantly. 1018 DOM has a yield of 70K psi, normalized 4130 DOM is 74K. That’s the average, their possible range overlaps, so the 1018 _could_ be stronger (info from a Mark’s engineering handbook and my father, who spent the last 40years of his life as an engineer in the aerospace and then steel industries). If you can find it, 1026 DOM is stronger then both (originally invented for airframes + easy welding but hard to find).

yea, don’t really need much of a lesson in metallurgy… I pretty much knew my steel alloys and the basics of forming assorted parts by the time I was about 12, related to being the son of an engineer in the industry

My confusion on this topic is based on what I’ve seen which seems very contrary to what happens in the ‘racing world’

4140 is, but from what I’ve seen I’d be very surprised if anyone could harden 4130 to a depth of more then about .120”. In most cases that I’ve seen recommendations (assorted aircraft stuff and a few racecar sources) it’s usually been “don’t bother trying with over .065”.”

Exactly my point… well, with the added condition that I don’t see the point of spending the extra money/hassle of using 41x0 unless you’re going to weld it with matching filler rod and then get it heat treated into the 120-130K psi range (you can get it harder, but at that point it becomes just about useless for any kind of structural part)

FWIW, never brinelle test the part that you’re actually getting hardened, have another piece of the same material done with it. The mark that’s left after testing creates stress risers it _will_ be the start of a crack.

Second, I’ve never seen anyone making ‘speed parts’/welding cages out of chrome molly use anything besides ER70Sx filler (mild steel), so you end up with a weld that’s about the same strength/hardness as main part of the normalized tube with a small area of contact quenched, hardened chrome molly around the weld. On impact (I’ve seen airframes built this way that have taken hard landings) they crack right next to the weld and usually crack to a sharp point (I consider that dangerous for a roll cage).

If you harden the whole part, you end up with weaker welds. If you re-normalize the whole part you end up with something with a similar strength but inferior elasticity before failure then if you made it out of mild steel (for that matter, you can’t really normalize steel with a torch like many fabricators assume, if you don’t get the whole part up to temp at the same time the cooler areas end up quenching the warmer areas)

FWIW, once you reach yield, 4130 typically has 1/3-1/2 less elasticity then mild steel (meaning that a mild steel part is more likely to bend, where the 4130 part is more likely to break).

Hum… so are you saying that 4130 is specified in many rules because it’s more likely to be DOM and it’s difficult to check otherwise?

Right now I’m looking at the NHRA’s cage rules, and it basically lists the minimum OD for each tube as being the same for CM or MS (mild steel), but it all has to have a minimum thickness of .118” if it’s MS, and thickness ranging from .049-.083” for CM. (I thought that it specified DOM for both, but I can’t find any mention)

Now even if we were to assume hot rolled, welded MS tube (I don’t think that it’s a legal material, but it has about 65K psi yield), that .118” (usually more like .120-.125” in the real world), comparing it to the same OD, .049-.083” cold rolled, DOM CM, every one of the mild steel pieces will be stronger, and I believe that the cage would better protect the driver on impact (if hit hard enough to yeald either material, it would be more likely to deform and absorb energy, where the CM would be more likely to crack and spear the driver).

Taking a quick look around, I noticed that the mild steel rollcage supplies available are what appears to be DOM (I was under the impression that welded tube was illegal), CE lists all their stuff as ‘mandrel formed’ (I know, that could mean anything… I may have to take a good look at the cut up roll cage I’ve got sitting in the garage). Hum…

 

That’s being kind. I’ve seen similar claims, but the testing I’ve seen usually puts it at 0-3%.

Of course, there is always the chance that whoever was doing the cryotreating has their head up their butt or is ripping people off.

hum… yea, I’m thinking the same thing… the strongest useful temper that I can find for Ti puts it at about 180,000.

You can always heat treat/temper most metals harder, but at some point they become just about useless for just about anything structural. EX, 4130 past Rc in the low 30’s becomes so brittle that it is not very useful for anything structural, even though I know that it can be heat treated past Rc 50.

[QUOTE][B]AFAIK, halfshafts on F1, and virtually all high-powered open-wheel cars are some form of steel. Even some of the CF rear suspension links were replaced with metal when a cracked exhaust pipe allowed exhaust gasses to soften and fail the CF link.[QUOTE][B]

There’s actually a better reason then that that halfshafts are usually steel. CF can only be made to be very strong in one direction and is also very brittle and has very little elasticity. Most normal cars need some elasticity in the axles to deal with the forces trying to wrap up the axle shaft under acceleration. Most open wheel race cars have inboard brakes and do not only exert that force under acceleration on the half shafts, but also a similar or even greater force in the opposite direction under braking. That constant cycling in the direction and magnitude of the force on the halfshaft requires that it be made of something that is somewhat elastic and not brittle. CF and even CF hybrids (mixed with glass or armid) usually are not to happy in an environment where the stresses change direction.

So what’s all this noise with Mindgame? I’m almost tempted to take him off my ignore list… I feel like I’m missing a good show.

 

Mark,

Not trying to give you lessons in metallurgy. I was trying to compare DOM to plain welded "muffler moly". Not everyone who reads the posts is as knowledgable as you. Sometimes a little background info helps.

Had to laugh at "That’s being kind. I’ve seen similar claims, but the testing I’ve seen usually puts it at 0-3%."
Originally I wrote "an order of magnitude or less". Wouldn't it be convenient if we could take a MS part, deepfreeze it and magically increase it's TS & YS 50%? All these high-strength steels in vehicles and bridges etc. wouldn't be needed.

As for halfshafts, I agree. Also, on open wheel cars they are in the downforce airstream and need to be small. Most high-powered open wheel cars have outboard brakes now, I guess.

 

Thread edited to get back ontrack of the intial post/question and to cut out the stuff that is not relvant.


I'll miss ya Alan

 

all i can figure is that you too must have some personal issues (take it up in e mail) cause if you're putting the guy on "ignore" from a technical standpoint then you just have poor judgement or you already know everything and don't want to learn. don't know ya, can't say but that was a pretty tactless remark in my opinion. searching through the guys posts (now that i know how to search) he's sharp, and you'll all be losing out if people leave for these reasons. same has happened on a few boards i can think of. too bad.

JB

 

Sorry, I was worried that that would come across like that.

Your response was appropriate to the topic, and most people reading it here learned something from it. My point was more that I was fairly certain that I had some of the finer details of it down, and based on them I wasn’t understanding what people were thinking.

I still have to ask: are you saying that the sanctioning body rules are written the way they not for strength or safety reasons as much as they are to make it more likely that they can be tested (easier to test for 4130 then it is for DOM tubing)?

If that’s the case then I would say that that is very short sited by the sanctioning bodies. FWIW, I have spent some time looking for a real answer here and have found that most related ‘experts’ do not have an answer and consider these same rules stupid at best and dangerous to the driver at worst.

I guess an order of magnitude would put it at 5%, huh…

Yea, it would be great, of course, based on the design of the ‘speed parts’ that you can buy out there you could get similar increases without greater weight… if the manufacturer’s paid attention or knew something about properly engineering pieces for the loads that they will be under. It’s amazing how much better you can make things by just cleaning up and properly fitting parts as opposed to just slapping them on.

To be blunt, he's been rude with me and others, is full of it on some of his finer details, and expects people to bow to his "knowledge" because he's been involved some related software development. Anyone who doesn’t is treated like they are launching a personal attack on him.

FWIW, it turns out that I’ve recently figured out that I’ve met him in person (we work in the same field in the same area) and that didn’t help my opinion of him.

(sorry about the off topic BS, but enough people have asked... back to real stuff)

 

Just want to state my opinion.Mindgame,please stick around! Your presence makes this a better place for all.People dont have to like each other to have a little respect for another.Its quite easy to take things the wrong way,especially over the net,

 

No arguments there.

I've seen too many aftermarket or purpose-built racecar parts "designed" for convenience of manufacture, installation or access rather than for strength with minimum weight. Also the locomotive school of design which preaches "if some is good, more is better" seems to have many fans.

Back on topic: I see the driveshaft diameter on the Cadillac CTSV (LS6 engine) was increased to 70mm, probably for strength to hold the 400 hp and to minimize whipping at the 7500 rpm or so it turns at 160 mph. It's relatively short with CV joints also.

My $.02