Why not aluminum like the rotor housings, its much lighter and would expand at the same rate. Why did they use iron on the side housings and aluminum on the rotor housings??

 

my first guess would be the cost of production.... just a thought...

 

Could also be wear issues.

I know the original L10A Cosmoa had ally side housings...

 

That would be my guess as well.

 

why not chrome plate the face of it like they do on the rotor housings? should reduce wear especially considering it get's a lot more oil lubrication than the rotor housings.

 

You can always just order the aluminum housings from Racing Beat.
https://www.rx7club.com/forum/showth...threadid=90000

 

there goes my college education

 

The rotor housings are a different story. They are not chrome plated aluminum. They are chrome plated steel with aluminum cast around it. (They start with a steel hoop, form it into the peritrochoid shape, cast the housing around that, and then chrome plate the seal surface. Ignoring about a half million important machining operations... )

 

damn where the hell do you guys find out these kinda of things??? fill me in somebody

 

SAE documents and various books

See the "Resurfacing" thread, p11 for a select few papers that will get you started.

Brandon

 

yea, i know racing beat offers the aluminum ones, thats what made me wonder... why mazda didnt do it in the first place.. hmm

 

Based on the price of the RB housings, I would guess it was an economic decision for Mazda to go with the iron.

 

bleh, i doubt it was the cost.
Mazda went on an aluminum overdose for the FC. Screw cost, we hate weight!
If changing to aluminum could've cut some pounds they would've done it

 

maybe it was a strength issue , the side housings have the bearings and stationary gears feeding loads into them , perhaps an aluminium casing isn't rigid enough to be reliable in the long term ?

 

I personally think the seals would just eat the hell out of the aluminum, and lead to bad compression leaks

 

That's fairly obvious. Of course the housings would need some sort of steel insert similar to what is done with the rotor housings. But this was previously mentioned in this thread.

 

The aluminum housings work great on the track, and are highly sought after by endurance racers. From what I understand, Mazda Comp supplied a limited number of aluminum housings to its sponsored race teams, but these housings are no longer available. I don't know if RB was the original manufacturer, or if they are just offering a solution to the discontinued housings.

From Racing Beat:

“After each aluminum housing is cast, using A356 Aircraft Alloy, it is heat treated to “T-6” hardness and the CNC-machined prior to being flame-sprayed and ground to a final finish. The greatly increased wear resistance is the result of this aerospace originated flame spray (or plasma spray) process that imbeds into the wear surfaces a proprietary carbide material whose durability greatly exceeds that of the nitride surface found on the stock cast iron housings.

During development testing, and the subsequent application of these housings in very high horsepower, turbocharged engines, it was not uncommon to find no measurable wear on these housings. We have found the flame spraying process to be so effective that we utilize the process on stock side housings with the same excellent results.”

 

On early prototypes of the RENESIS they used Al plates. Sadly, that idea got ditched. Dooming the 13b to be "not as light as it looks" once more.

-pete

 

If they could be made from billet aluminum and have a protective coating/plating on the wear area that would be great. But I am not aware of any production motor having any large components made from billet.
The amount of machining time would go through the roof compared to casting the parts and only machining the areas that required machine surfaces.

If someone here with the skillset could workout the CNC programs for each component that would be a start

 

Can endplates even be milled? When I looked into it, I was told that they have "interior features", and could only be cast using a, uh, "lost wax"(?) method.

Thoughts?

Brandon

 

That is a very possible problem. With a lot of parts made from billet and even cast parts they have to open up areas for things like water passages etc., and they use threaded plugs and other means to seal off the access point.
There are some areas you can see in this cutaway (from Mazdatrix web site) of a rear housing that illustrates the nightmare that would require some serious redesigning.
The only way I can see doing it is to make the entire oval area within the inner water o-ring seperate so you could access the area underneath to mill.
If you were going to run a pport housing and you got that far you would be in real good shape.
If you had any ports coming in from the sides you would probably have to tig weld in the port area where the two pieces met. The sealing when the oval cutout was put in place would be another challenge but it could also allow you to use another alloy altogether for this piece since it is subject to high wear.
If you got that far though that would be easy

 

They could make billet end housings, just like they make billet cylinder heads and billet blocks. And just like billet cylinder heads and billet blocks, billet end housings wouldn't have any coolant passages.

I wonder how long a coolant-less rotary (solid cooling jackets) would be okay running. 30 seconds to a minute should be enough time.... burnout, staging, run, coast to the end of the shutdown lanes, and get towed back to the pits.

 

I wish I had the knowledge and the mill it would take to pull off making a set.
I could not bring myself to eliminating the cooling system though. You make a very good point on that, but it just goes against everything in my being.
Trying to tune before it melts down would be a challenge for example.
But one point thing that may work would be to use a flycutter to open up the area (kind of hollow out) in the center plate where the eshaft comes through. If you could get it fairly hollow and use some crossdrilling from the opposite side of the rotor housings on each end plate you may be able to do them in one piece and still get the cooling you need.
You have water passages between most of the tension bolt holes to cool the outer area and the middle gets a lot trickier.

Damn I would love to pull that off!

 

How do you think they tune jacketless boingers?

 

Very quickly!