Casting Al356 rotor housings
 

I wasnt really sure where to post this, but i figured id get more exposure here than elsewhere...
I am a college student with an '87 tII FC. I've blown a couple motors now, and im tired of spending money buying jdm motors...

so im going to try to cast my own housings.
So far i have a huge ingot of T6 a356 aluminum (the same used by mazda for factory rotor housings... and a fairly non-toxic recipie for sand.

My school gives me access to furnaces big enough to melt 50 or so lbs of aluminum at once, which i can then cast in a mold that i prepare based off of one of my old housings. I will have to lose some of the external features (the smooth indentations on the outside of the rotor housings, the oil injection ports, etc...)

I have access to Three six axis liquid cooled CnC machines to mill the rest of the housing out, and smooth the inside of the rotor housing.

Then i plan on coating the inside of the housings with either the factory (TiN, titanium nitride) coating, or perhaps trying to 'use' one of the many patents for DLC (diamond like carbon) or other ceramics which i can apply using the plasma spray gun which i use for my work.


My question is... has anybody ever tried this... or know anybody else who might know anybody who has? I think Rb casts their own housings... does anybody work for them??? I have some concerns with casting it due to my inability to ensure small, equiaxed grain size within the metal (i may be able to anneal or otherwise heat harden the metal after the initial casting) My only other concern is with coating thickness/tolerance for the sliding surface of the rotor housings.
:sadwavey:

Well, there are recoatings of rotor housings done in cermet, cermet a and b are the 2 types. The main issues is chipping of the surfaces. Perhaps it'd be easier to do that, machine your old housings and respray them with cermet?

The old housings both have huge gashes from apex seal chunx. was thinking about machining and coating but i would have to machine out like 2-3 mm deep, which would start to push into oil o-ring territory.
Plus, a cermet that thick would be too brittle i'd imagine.

That's a few steps beyond an oil change and installing an efan, eh?

I don't think anyone has made their own rotor housings, not even RB.

Please post pics of your attempt though...I'll bet such a post would set forum viewing records.

look, Mazda has spend BILLIONS since they bought the patents from NSU in order to come up with the best combination of metals to ensure that the housings are STRONG enough AND so that the apex seals don't wear down the surface.

I doubt you will come up with any better combination of iron, aluminum on top of the treatment bath for it's strength. I would not try to "solve the flaws MAZDA housings have " as much as I'd be look into HOW YOU'RE KILLING MOTORS.

I don't think this is a case of faulty housings, flawed engineering/design as much as it is driver error. You're either very smart or you haven't done any research into WHAT MAZDA DID to reach the final product it has mass produced. I forsee an NSU-like housing life of ~50K miles if you even create a finalized motor. Feel free to try and shut me up but I expect you to do the same 1500hour testing that Mazda did to the 5000+ motors it built while trying to come up with the final combination of metals for our housings/motors.

In response to phoenix 7:
Mazda did not design their own alloy to make these rotor housings, they used al356 T6 which is a COMMON aluminum alloy. They also did not design any new materials to coat the inside of the housings, they used Titanium Nitride, which is a CHEAP and WIDELY USED hardening process. Most of the testing that mazda did is already done for me, in the design and shape of the housing, which i intend to replicate with a housing that i already have.

in addition to this... What do i have to lose? i will learn a lot, and if my housings come out of the furnace, go into my motor, and explode, i will still be ahead of where i started, because i will have learned a LOT

Oblio...

Given your access to the sophisticated 3-axis CNC mill, wouldn't it be simpler to just machine the part from your billet piece rather than cast it?
That would eliminate your concerns with casting uniformity and integrity.

Casting makes sense for volume production and/or if you have blind recesses to produce...neither of which is the case here.

Just wondering.

I did consider simply machining a new piece, but even using a mold and sand-casting the rough shape, planing and lapping that down would be faster than machining a rough or rectangular block. sand casting is totally easy, plus, with casting it, i can ensure that the aluminum has small and equiaxed grains (due to slow and minor undercooling during the solidification process) which will enhance its hardness.

I dunnnnno. This is the first case of "I've blown too many motors so imma make my own housing" that I've ever seen. I'm glad you'r enot letting my negative nancy-ism and skepticism get to ya. I still don't know what you're trying to accomplish but get to it.

its not that 'ive blown too many motors', and it is that ive blown too many motors. i bought the car with a 'fresh rebuild' and spent more on it than i should have. on the way back from buying it, the motor blew. so i rebuilt it myself, using the same housings and rotors, and that one didnt last long. so then i bought a jdm 13b-re and built that with single piece titanium seals, and ran a 1.7 chipped ecu from rtek. that one lasted for 40k mi, but it blew when i came down to college and drove it for several weeks without really letting it warm up, or ever running it hard. when i finally did run it hard, there was (i guess) some carbon buildup inside which broke 4/6 apex seals and took out my housings...
im in college, and have little money, but have access so many tools that i will never ever in my life be able to access again. i have PHd's trying to help me decypher/redesign various rotary housing cermet coatings... i have a freakin foundary and plasma spray gun at my disposal! its just something to do.. a project for my beloved rx that i cant afford a jdm motor for right now

well here is a link in case you haven't gone here yet:

http://www.sae.org/servlets/index

very intersting rotary articles/papers.


i WOULD STILL TRY TO BUILD SOMETHING ELSE WITH THat machinery and leave the housings to mazda but :dunno: that's just me.

Go for it, buddy. As you said, even it it fails you still learned a lot.

whatever happened to that one thread with the guy regrinding and recoating housings with this special coating? I got up to the part where he gave some p-port housings to a drag racer friend, and after a day at the drags, they looked great... havent heard anything past that... did the project fail or something? Because the dude even built all these mills for this and stuff.

ahha phoenix7 doesnt get it...

but he is being nicer about it.

he isnt really trying to out engineer mazda to my understanding, i think he just cannot afford anything right now and want to try to get new experimental housings for free except time :)

i mean why not try heat harden the housings, or whatever he is trying? hell if it works out... its something for us to know and use for future references.

why do companies try to out engineer oem seals? to my understanding to sell something it has to be consistent, and the combination mazda used may just be the most consistent at the time.

I love articles/threads like these. Although the better title would have been:
"Here we go! Gonna try to make my own housings!" and then in that thread keep us posted on how it went.

I do so want to see things continue to move. Unfortunately though, it often turns out that we are always trying to reinvent the wheel. I offer you my wishes and all the best luck. Now get to casting and take lots of pics! I want to see you succeed.

I guess you missed the part about the press-fit "sleeve" that's made out of stainless steel and chromed?


-Ted

You know the Russians built some rotary engines that were very similar to mazda's. It's possible they did the same thing you are planning. I think there are even a couple members on here with the russian rotaries. check it out.

Russians were famous for reverse engineering things such as planes, etc.

go for it oblio, sounds like you have a solid plan

subscribed! I really want to see some pics of this!

This thread has potential not usually seen on forums....

Go for it. If its something that you want to do then do it. If it turns out great then ill have to get you to built me one too. If you have the tool you might want to do it now because there might not be another chance like this again.

i'd like to see this happen as well, seems that most housings that you get, are all used.

i can think of a list of reasons why this won't work, of which i am too tired to list right now.

I'm sure that list would probably help though.

Mazda did a good job on the rotor housings- just use them (with a proper apex seal material!)

They totally cheaped out on the side housings after the Cosmo Sport 10A and early race engines since the cheap cast iron worked just as reliably as the flame sprayed aluminum.

So, take the cast iron side housings, add some material to the dowel areas for strength and port runners for portability, cast them out of alum, machine them, plasma spray them, sell them and buy all the Mazda rotor housings and ceramic apex seals you want!