Cheers!

5th paragraph, 7th word... should've been transition, not treatment. I should've proof read the post before clicking submit...

Lynn E. Hanover

The fatigue you worry about is a result of repeated cycles of flexing. Like bending a strip of aluminum until it breaks. So, as long as any particular piece is used inside it's design limits, there is nothing to report fatigue wise. When you make repeated use of a piece far enough beyond it's design limit to generate distortion, the structure begins to break down. Mazda going to all stationary gears being hardened is an example. It is hard to believe that anyone would rev the **** out of a rotary, but appearently, so many owners did, that the factory finally caught on to it, and started hardening the gears.



Who could drive a rotary without seeing what the redline in 3rd feels like. And just like flying a plane, once there, who would want to leave. You become addicted to the endorphins. It feels so good to be pinned into the seat........................OOPS, I said more than I should have......



Anyway, the higher the stress, the shorter the life of any part.



Another example is lightened rotors. If you do that, you must lighten the counter weights as well. This gives you several benifits. One becomes obvious without instrumentation, and that is: a big decrease in rotational inertia. ( It winds up quicker, and pins you in the seat harder). Another is not quite as obvious, and that is it lowers the loading on the rotor bearings, the main bearings and the crank.



The crank gets bent into an "S" shape at high revs, and that misalignment causes the rear main bearing to drag along the front end a bit. Also the rotors are not running square in the housings and will drag the corners and hose the corner seals and some times the irons (or worse). If you look at the Mazda hop up instructions you see them opening up half of the rear main a bit to allow for this crank flex. I just scrape the front and rear of the bearing down to copper for about 1/8" and then open the whole thing a bit with some killed 600 silcone carbide paper in solvent. I have yet to loose a main bearing (since 1980) so i guess it works. Highest recorded revs so far has been close to 15,000 RPM. Now that did shine up the bearings and hosed the corner seals but we ran that motor the next day after a rebuild in the dirt at Road Atlanta. The REM thing works and is on the drawings for many high stress parts. The deep freeze stuff in liquid CO2 is on the drawings for many high stress parts.

Most often seen in torsionally stressed steel shafting. As in drag racing axels and helicopter parts, and similar.



But once again I have run on..........................



Lynn E. Hanover

mazdaspeed7

You just put into a lot of words what Ive always thought on cryo treatment. I just thought Id throw that out there for arguments sake. The article I read was about a bone stock SCCA racing class(dont remember the car), but brake rotors had to be OEM, as well as pads, etc. The cryo treated stock rotors lasted considerably longer than the untreated stock rotors. The untreaded rotors were prone to cracking from the heat cycling after just a couple of races, while the treated ones went the better part of the season before needing to be replaced.

j9fd3s

ive tried to quit, but um i keep falling off the wagon.....

j9fd3s

pro7/ita/e prod are other classes like that. you have to use a stock brake rotor, and the oem ones lasted longer before exploding before the aftermarket ones, but they ran out of factory rotors, so now everyone has to change brake rotors every couple of races (or keep a good eye on em) so they dont explode.



it was a whole big thing in e prod, because the 1st gen rotor is also the wheel hub, so when it explodes its dangerous

Mr. Midas

Well, looks like I'll be upgrading. After rethinking what I intend to do with this motor it would be nice to have some extra insurance here and there. I'll have to do some more checking on the rene stat gears. Anyone know what Sollo II class they would putt me in if they'er even allowed? Maybe S5 or fd's would be better in my case.



NOTE: I am not a metalurgist, chemist, or physicist...ect. I simply enjoy reading/leaning technical/scientific things. So if I get something wrong, please correct me in a kind manner. I love to learn, and am willing to accept correction.



After reading about it some more, it appears that cryo treatment doesn't make a part more hard, but instead, helps to even the hardness, relieve stresses within the part mainly from the conversion of austentite to martensite, and assist in the precipitation of very fine carbides(mainly in carbide tool steels) throughout the crystline structure, thus increasing the wear/abrasion resistance of the part so treated. As I understeand, and as an example, It does increase the life of break rotors which I believe have no austenite in them to begin with.(pearlitic cast iron) So, the heating/deep cooling/heating process is doing more and is for more than just converting austentite to martensite.



Of couse, if a part has a significant amount of retained austentite, the part will grow from the coversion process as martensite is about 4% larger than austentite. Also, it is logical and and safe too asume that a part would need to be heat treated/tempered again after cryo treatment in order to stabilize/temper the newly converted martensite. I believe NASA is one of the main research/developers of the cryo process and has cryo treated components in use.



There are many people using crygenic processing on audio/electronic equipment, and they claim it does give them a noticable improvement in audio quality.



I do agree that some of the claims sound like baloney. But I can see how brass/metal musical instuments could also benefit if it truly does help to relieve internal stresses of the metal. That is why some of the best and well known wooden instument makers use/used aged wood. The longer a given piece of wood is aged the less internal stress it has, and thus better resonating properties. To me internal stresses are like static energy. They are constant forces fighting to find their own ballance while they are held in place. Instead of being happy together, some of residents in the crystaline latice are fighting. Any energy attempting to pass through a stress point will be impeded, distorted, reflected, or absorbed somewhat as it passes through. The weakest link in a chain always breaks, and so on and so forth...



Wether-or-not cryo treatment makes a big enough difference for us is another debate, and it apears most of you don't see any good enough reason to use it on anything other than brake rotors. I can say after doing more research, I can mostly agree. I would not do this on parts that need to have precise dimensions, unless I knew the exact percentage of retained austentite, or the part still needed to be set to the required dimensions i.e side seals. It seems better suited for use in production where it could be used before the final machining/finshing takes place.





I hope this made some kind of sense... I definitely think something contagious is in the air...



Oh no!... I've got E-NDLP (Electronically-transmited Neuro-Degeneration from Long Posts )





Thanks allot guys!

j9fd3s

ive seen 1 engine failure that was the stat gears (driver downshifted into 3rd, but got 1st instead, engine ran but it clicked...)



and 1 engine failure that might have been the gears, but it could have been a bunch of other things too, we're not sure, every peice of the motor was broken....

Cheers!

Your first remark about converting austinite to martinsite at below zero degrees celcius is wrong. I'm not attacking you but that is just wrong.



NASA does not cryotreat anything. I may not work directly for NASA but my company is a customer of NASA as we do the canada arm for the space shuttle and for the international space station and we have every single NASA standard in our database. I reviewed all the NASA standards at one time since it was required when I started there, along with all Military specs, DOD, and ASTM specs and there is nothing written on cryotreating. Unless foriegn companies are excluded from certain NASA docs I believe we have the entire library. We design and manufacture based on NASA standards.



I also did a search using the SAE database for AMS docs pertaining to cryotreating. Nothing. If all these organizations do not have a standard or process for cryotreating that leads me to confirm my original conclusion that cryotreating is BS. I got a quick asnwer from my materials professor 1 year ago when I was taking a materials design course in my 4th year of engineering. He told me nothing happens below room temperature. I remember the lecture where I asked the question, his response was nothing happens below room temperature to the strength of a material even if you submerge the peice in liquid helium at 2.17 kelvins and raise the temperature back up.



I do know electrical properties change for certain ceramics as I had a 3rd year lab on super conductivity of

YBa2Cu3O7 and NbTi



Wood and metals are completely different materials. Please do not compare them. It is even worse than comparing apples to oranges. Wood is a composite of organic fibre which have closer correlation to carbon fibre and fibreglass, where the basic property of wood is carbon, carbon being an element. Metal is metal for sake of better words. The 1st year mateirals/engineering courses describe it as lattice structure of atoms with electronics freely moving in the lattice (or a pool of electrons).

Cheers!

I'm not 100% sure what alloy the gears are made from but it is probably some sort of Low Alloy steel which means it's heat treatable. If you wanted every last once of performance/strength/hardness I would find a reputable shop hopefully with ISO certs that can heat treat your gears.



Tell them you want to heat treat them to AMS-H-6875 (Heat Treatment of Steel Raw Materials).



Write: Heat treat to general requirements of AMS-H-6875 for 4130 alloys. Have them stick an additional peice of stock chromoloy. Tell them, verify that mechanical properties meet requirements in AMS-6350 with tensile test peice made from same stock and subject to same treatment as part. Test in accrodance to ASTM E8.



Then if you are super **** you can have the gears magnetic particle insepcted.



honestly how far do you want to go? I didn't realize rotary engines were meant to operate in space.

Cheers!

I forgot to put nitriding.



Tell the same shop you want the following.



Nitride as per general requirements of AMS-H-6875 for chromoloy alloys. Include additional peice of same stock and subject to same nitriding. Verify surface hardness of additional peice exceeds HRC 40.



Then stree relief gears as per AMS-H-6875 30°F below aging temperature. Tell them you want to have it reliefed at 50°F below aging temperature to account for variations temperature probe.



Then you need to inspect the part and insure that no single dimension has changed by more than 0.025 inches. If parts can not meet 0.025 inches variations after corrective machining then discard parts.



Don't forget to ask for certification of conformance and test results so you can analyze each and every single process.