It's not impossible, it's just not practical. You are correct in a number of areas. The espense of creating functional rotors is enormous. One has to justify that type of expense.

I'll be frank here as I have before; I'm not the REAL expert on any of these topics although I know more than most. I do hang with some of the most experienced and knowledgeable people in the rotary game on the planet. You're also correct in that these folks are seldom on the internet and hardly ever post anything.

I retract the statement that it won't happen and instead will state that I will be pleasantly amazed. Both at the completion of them and to their functionality and durability.

 

220hp with 2 rotors? 1308cc?
________
DADSBOY

 

that's exactly true - torque is just a rotational force which is a product of force and the lenghth of a rotating arm. In other words Force = acceleration * mass - if mass goes up, acceleration goes down (with constant energy) if mass goes down acceleration goes up and all that has no effect on torque. It may have an effect on power though. Less mass - higher acceleration thus the same work can be performed in shorter time - power goes up.

 

It's true aluminum absorbs heat faster than steel, but it also trasnfers heat faster than steel. So the expansion rate isn't exactly black and white, because oil can cool the aluminum rotor. But still, it will expand too fast because rotories inheritly run hot (just guessing).
But I wonder if Mazda ever experimented with different rotor types, like billet or titanium. Titanium would be nice, obviously because of it's superoir strength and lightweight, and it's heat characteristics are similar to steel. Another could be magnesium, which is lighter than titanium, but britle. And I also think magnesium can catch fire (burn) if I recall correctly.
But a titanium rotors price would be ridiciulous. But that doesn't mean it isn't possible. In motorcycles, titanium valves are becoming popular, and I know the valve doesn't undergo as much stress as a rotor would, but it's a step.
And I've heard of a few aluminum rotor single-turbo RX-7s, but the most they ever get is like 100 to 200 miles before the tolerances become too great and the engine locks up. Too pricey and not really worth it.
And I love how everyone gets hung-up on redlines, like 9 or 10 thousand RPM is a big deal. Because of the rotories orbital nature, a 30,000 rpm redline isn't that far off. It just isn't practical. And don't say there aren't materials that can handle that stress. The 2006 Yamaha YZF-R6 crotch rocket has a 599cc DOHC fuel injected in-line 4 cylinder piston engine that revs to 17,500 rpm redline. And before that, in the late '70's, Honda made a limited quanity of a CBX racing bike with a 600cc and 750cc in-line 4 carbed versions that revs to 22,000 rpm. And, if anyone here is into R/C cars, there are nitro 2-stroke cars with engines that displace 0.15cc, that rev to 55,000 rpm (basically because they have a 3mm stroke and they wouldn't make any power otherwise). So 10k isn't that much, and with reduced rotor weight, any redline is possible.

Dave

 

I think this would be the way to go, but would it be practical and cost efective?
how about raplacing the ceramic for titaniun?

any updates on the ALUM rotors?

 

Interesting...I'd love to read their results! Anyone know East Coast Parts? Has anyone invited them to the board to discuss their project?

<snip>
Billet Rotor

This Rotor is being machine from certified T6061 Aircraft quality aluminum. We are going to be testing this part in the next few months and we will keep you updated with our results and specifications.
</snip>

 

I still want to know how they are going to machine the inside of them. Rotors are hollow to allow oil to get inside and cool them. This is practically impossible to machine which is why they are cast.

 

Thinking out loud and fishing for forum napalm....

Why not just take the expansion into account for an AL rotor...and load the seals such that they can stick out or slide back in for expansion? I thought the seals now use gas pressure to "push" outwards anyways?

 

if the rotary engine seals were so easy to design everyone would be making one, rather than all the major manufactures except Mazda throwing in the towel ...

 

The aluminum rotors that were used in the HE-10X hydrogen concept car were far more than just a machined chunk of aluminum. They too were cast. Mazda went through alot of effort with them though. The seal locations were made from ceramic. These ceramic pieces were machined and then inserted into the mold where the aluminum was poured around them making them an integral part of the rotor. This meant the seal grooves didn't expand but they were also very slippery. Mazda's approach to the aluminum rotor was much different than this attempt. This is literally taking a chunk of aluminum and machining it to the proper shape. I just don't see this happening successfully.

 

First, we apologize for not being part of the topic in hand. We are so busy that we don't have time to surf the web or go into chat rooms.

About the rotor, well every one is kind of correct. Yes, this project has been very difficult but not impossible. We have spoken to people such as Alex Lopez, Rohan at Xtreme rotary, Carlos Lopez, Chris (Crispeed), Siguel Torres, Gabby Skern and many others. They are very excited.

Expansion is one of our chief concerns, since it expands twice as fast as steel. (not Cast) Our concern is that aluminum and its alloys lose part of the their stregth at elevated temperatures, although some alloys retain good strength at temperatures from 400 to 500 degrees. We have taken all this info into account to help with the design. We are using T6 aluminum from plate and certified for reassurance of its quality. Plate is usually better quality than extrusion but is more expensive.

Tolerances, our research shows that the rotary engines are not in such high risk in tolerance like piston engines. What is interesting is the way it was design. For one the shape of the rotor.

I have contacted top fuel teams about the expansion rate of the piston and their info has helped us alot.

We started this about a year and half ago and we are still learning. We are now in the last stages of the project and hope to have one ready for the upcoming PRI Convention in Orlando next week. We had to design a machine to cut the side seal grooves and this is the reason why the rotor has taken so long. The groove of the side seal is .032 thick and is .14 deep. There is no end mill that can cut this so a custom cutter was designed to make this cut.

This rotor will be coated for heat and lubrication. We feel that this could work and our hopes are high. We have our own dyno and have Alex Lopez assisting with the assembly. Once we get back from the convention, we will begin balancing and coating the rotors for assembly. The entire procedure will be recorded and placed on our web site. We know that the drawing board does not end here and we will visit often, but our hearts right now are in getting this to work at an affordable price. Street use is still far away but we will see what the future holds.

Wish us luck and we will stay in touch.

thank you
Edgar Perez

 

Does the rotor have to be solid on the ends? Wouldn't reducing the steel at the ends reduce the weight? (i.e. put holes in the ends)

 

a website or url would be nice to post if possible...

just thinking out loud here but...why not simply use a steel with AL "inserts"? Might be easier...

 

The steel rotor is hollow in side and if you machine to much it will leak. I have talk to Jesus Pedilla from kilo racing and the most weight that he has removed is 2 pounds for the original.

 

Arent the stock Renesis rotors aluminum?

 

Uhh...the post prior to yours stated its steel...btw...

 

cast iron.

 

thx!

 

In case anyone was wondering... it runs!!!!!!!!

http://www.youtube.com/watch?v=eStMcTUkou8&NR=1

 

Cool! I'd love to know how they hollowed out the center of it.

 

Any educated guesses as to how such rotors would affect performance? (ie. hp/tq/rpm's, ect)

Is there a "rule of thumb" type of performance scale utilized depending on how much weight is saved on the rotors (ie. if the RB rotors are .2 pounds lighter and that effects performance by X amount, how much would the performance increase by decreasing weight at .1 Ilbs increments)

 

If they hit the projected 6lb mark as was mentioned in this thread it would GREATLY decrease bearing wear.

I think only testing would be able to show the type of performance gain would be attainable.

For a guess you could take the older 10+lb rx7 rotors and build a n/a motor in a renesis core and see what kind of power increase you get when you throw the renesis rotors into the same build.

 

the idea is right, but it cant be done, the REW rotors wont go into the Renny