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Counturemarc, are you sure it's that shallow? four to seven tenths of a thou? gas nitriding is only $100 for .002 (not sure about the cost of liquid nitriding yet) sounds good to me.
I don't doubt the $300 to $400 per face price, the setup is a bear to make sure everything is as flat and paralell as necessary.
Lapping is another thing I am going to have to figure out, can I actually just sit there with two side housing face to face with lapping compund inbetween and lap away?[/QUOTE]
Like i said, the "effective" depth is only about 0.0005". The total penetration might be 0.002" or slightly more but after 0.0005" it has little effect on wear resistance and really just helps provide a bit of extra corrosion resistance. Just seems like a lot of effort and time to get a part that not quite as good as a stock part, whenever i modify i tend to upgrade where possible.
I called around today and ended up talking to a guy who really knew his stuff and explained in the process in depth. He was definetly in favor of Ion nitriding due to it's lower processing temp and less white layer formation. (read rotariesrule's post)
Cost compared to gas is about .004 @ $175 (ion) as upposed to .002 @ $100 (gas). Sounds like a winner to me.
Time to get griding asap, hopefully this weekend, I'll be sure to get pics.
I only re-nitrided used housings that were scrap for an experiment to see if they warped or not and what the characteristics were for hardness/wear resistance. My good housings were all new (except for the endplates) and all the irons were lapped to assure they were very, very flat. I am not using a nitriding you guys are planning on using either.
Yes, we also used a stone for truing which was good to within (if I remember correctly) 0.00001" in addition to the mic which was used to check OEM tolerances. If it warped a mic would indeed catch some of it as well in the oil/coolant O-ring grooves.
The cost of nitriding depends upon the chemical being used. Don't assume that because of the process being used the cost should be X or Y.
I resurfaced the magnetic table today, flat as a pancake. I should get to grind my irons tomorow. Gotta remember the camera or I will be kicking myself black and blue.
One of the people you can speak with at Diversified is Bill Groschen, pronouned "grow-shen", he is the president and one of the board members of the Vintage Sports car racing club in minnesota. He is a great resource for information on cryogenics and how their process works.
OK bad news is that it's 10pm sunday and I just got home, 14hr day. The good news is that I did get some time to set up the grinder and take .002 off. I will probably have to take another .002 to reach the bottom of the worn grooves. I would put some pics up but it's late and I'm tired. The port edges are razor sharp... I cut myself.
I have 400 600 and 800 grit lapping comound, anyone have any recomendations on which one to use? I will get surface finish pics up tonight of the grinding finish. I was reading on Yaw Power's site that too fine of a surface finish will not retain oil due to low surface tension. I might just have to do some testing on some experimenting.
Pics Attached!!!
I haven't lapped yet. This is the finish the grinder produces. The hydraulic cylinder that moves the table back and fourth finally gave out and coughed up a rod seal. I made a new one out of 1/2" neoprene sheet and should have the machine back up tomorow, should be good for a nother 50 years. I had to take the whole damn table off so now I will have to resurface the chuck again when I get the table back on. I now have a 5-gal. bucket full of saturated oil absorbent, it was a mess.
So it's been a while since I updated this. I finished grinding all my side housings and have had great success lapping the housings ground face to ground face since they are already very flat and lapping removes such little material it is a great way to just get the surface finish right. The housings are really flat (straight edge and .001 feeler gauge shows no recesses or warping) and it's paralell to under .001in. Needless to say I am really happy with the results. I am building a fixture now to do the lapping with power supplied by something other than me. (weak little arms) I will hopefully get them out to the nitrider within a week. I will get some pics up of the surface finish soon.
I removed .003" with the surface grinder. The grinder leaves a surface that it not very suitable for the side seals. You can see the post grinding surface finish in the 3rd pic of my last set.
The lapping is just to remove the grain of the surface finish. I have used 400grade so far which is classified as "very fine". I have 600(very fine) and 800(extra fine) that I have not tried yet.
I am basicaly following Paul Yaws procedure except I am nitriding the housings again because the hardness of the iron after nitriding diminishes with depth. Nitriding should produce a hardness of 60-70C and I could tell with just a file that there is no way it was that hard even after .001 was ground off.
From Yawpower.com:
Housings are ground flat, and then lightly lapped to provide a minimum surface finish of 15rms measured across the grain.
We prefer grinding to lapping for 2 reasons.
1. Grinding insures that the opposing surfaces remain parallel. Lapping provides a flat surface, but does not have a mechanical reference to the opposing surface. Grinding involves mounting the housing to an electromagnet which is parallel to the grinding wheel travel so that dimensional accuracy is maintained.
2. A housing that is lapped mirror smooth will have little or no oil retention. This is clearly illustrated when applying assembly lube to a mirror finished housing. Rather than spreading evenly across the surface, the lube will bead up much like water on a freshly waxed car. Our process leaves some grain intact to hold oil on the surface, and the light finish lap flattens the top of the peaks insuring that the seals have a smooth finish to ride on. This approach is more time consuming, and so more expensive, but has proven to us to give the best housing and seal wear, along with a quick break in period.
lapping is bad idea on worn housings unless you first grind them flat. If you lap it the material is first removed where it is the highest, because the area of wear at spark plug side is alot more then on opposite side the spark side wears way more quickly due to the higher area pressure. For a center housing if you lap away the wear u end up w 2 perfect surfaces but they aren't parallel anymore. This is bad. Especially on 3 or 4 rotor engines.
I managed to buy a pre war Blanchard grinder. After some work it now grinds perfectly. Thickness measured w a micrometer on inside or outside is within 0.02mm.
I do not think I will lap the housings anymore after nitriding as I guess the superficial scratches help to retain oil just like honing grooves in a cylinder.
16yrs wow, hell of a zombie thread resurrection. For what it's worth 2 of the 3 irons are still running from my original post. It took forever for me to get the engine together and it ended up in my RX8. First NA, now running 15psi of boost. I cracked a front iron due to some careless tuning by yours truly. The cracked iron still measures great. Some wear marks but nothing measurable.
with REW rear auto trans iron plates being NLA, just looking/asking if theres been any progress made on the possibility to restore/build-up iron plate wear surfaces?
I had to go dig up a used REW auto iron in Japan and import it just to get my hands one even. I know the early engine owners are faced with this reality and am hoping that some progress may have occurred as technology moves ever forward.
the intended racing class requires using the OE “block”; essentially plates & rotor housings on a Wankel, in contrast the rest of the engine is wide open, anything goes.
So price is not as relevant when you just have to do whatever it takes. However, I may have to weigh it out against machining off the side of a manual iron instead. The auto starter would mount to the trans adapter. So the iron mounting holes for the starter aren’t needed.
It doesn’t even have to be machined. One person used cutting and grinding wheels to modify a manual iron. At which point the auto iron will only serve as the reference guide for doing that instead.
It just seems like there may have been some advancements made on plasma spray materials and such 15+ years after this thread took place.
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11-08-05, 10:33 PM
