I say its well worth trying regardless of the odds of it working so long as you have the finances to do so, and you really want to. Even if it doesn't work then you still have the ability to say you tried and threw all that money into something worthwhile. If it does work out, then all the things that you've described as better than the standard four rotor would be a huge benifit. The only thing I could think of that may help with the flex of the engine would be to find a means to custom fabricate a type of cage around the engine to prevent flex, and perhaps even finding a means to have an apex seal that goes through both rotors per chamber instead of having two seperate apex seals for both rotors. I personally want to see this done. If I ever have the money I intend on doing a four rotor, but my main concern now is getting the money to fix the brakes in my rx-7.

 

i was also wondering how you planned on doing the apex seals, i would think the best way would be a single seal all the way across both rotors, but that cost even more in fabrication. I'm pretty sure mazda built some wider engines than the 13b in prototype engines, i wanna say they built a 2.0L two rotor with wider rotors, but i can't recall for sure at the moment.

I would also think mazda made the right decision with going with smaller rotors, im sure they ran into lots of issues with chattering and such with such a long apex seal. Good luck with the project anyways, and keep us updated.

 

You got the Mazda 15A engine: http://www.der-wankelmotor.de/Motore...mazda_15a.html and the 21A: http://www.der-wankelmotor.de/Motore...mazda_21a.html, apparently they stopped it because of the oil crisis.

Also if you wider the rotors the chamber will become more square which is better then a rectangle because a square is closer to a sphear.

 

the problem i see is getting an evenly mixed intake charge across the whole thing. unless you add a p-port in the middle, youre going to have a wierd distribution across the face of the rotors, with more charge on the sides. im not sure you will make significantly more power, because you wont be pulling too much more air. if you had one big rotor, that would be better, but attaching 2 together seperates the combustion chambers from each other. i think you might just end up with a hot spot on the outside of each rotor, with the middle area not really doing much.

pat

 

The thing I don't get is how are you going to seal the 2 rotors? If you are butting the 2 up against each other your going to have to seal them up some how or you will run into major compression leak between the 2 rotors.

 

you could TIG them together, but that still wont help with the 2 seperate compression chambers.

 

If your going to spend the money for a custom Eshaft, why not go ahead and wax mold a custom rotor? Then you can just design it all to work correctly from the get go with a proper shaped chamber. Then I'd call someone that makes custom apex seals like Atkins or Rotary Aviation, ect and see if they can have a set made thats long enough for your bigger rotor.

You better use some HIGH QUALITY material for that eshaft, I'd also make it a little thicker in that stress areas. Your going to be slinging a LOT more weight around that thing. The bearings will need to be some high quality material as well.

 

I dont know if this has been mentioned but you will not be able to run the four plugs per cumbustion chamber... You will have two flame fronts coliding cousing uncontrolible detonation...

Justin

 

I have been dreaming of this for a while too.

My only hang up is the housings support ---there is no way I can see to have a single apex flow over the seam as it flexes.

I think a strong, wider housing would need to be created then maybe coated with cermitB.

I'd like to see an over sized scale made of the 13b, mostly made out of titanium.

 

titanium is not a good metal for engine internals as a rule.

 

I just don't see how it would work well. Hats off to you if you can get it to work though. I see issues of uneven combustion compression leakage and just sheer rotational mass in a small area. I'd think almost every single part would have to be mada at a machine shop. I think Mazda tried larger displacement but ran into combustion and effeciency problems.

 

DO IT!! And document everything with video.

 

yea i was goan post it but you beat me to it. tig the 2 rotors together then machine out the apex seals to 3mm just to make sure they are perfectly straight. wouldnt want to do it to 2mm incase of some bad warpage. then just find 1 piece 3 mm seals and use those. hell if you send me 4 rotors i will do the machining and welding for free.

 

o and im willing to help with as much machine shop stuff as i can. no CnC over here, well not one worth using, so it would all be by hand but i can promise quality work. we do build FSAE cars so doing a little welding and maching on a engine can be done easy .

 

Your still going to have the joint between the two housings right in the middle of the combustion chamber. Unless you plan on welding the two housings togeather?

Steve

 

i think welding might be the only solution there again... but that would have to be done VERY slowly to avoid warpage.

 

This is what you want. $9500 AUS. 4 Rotor E-shaft.

http://kiwi-re.com/wwd_showroom_cat10_2.php

They have extemely sick products...just wish I could afford them.

 

You know, you could always use 8 plugs but only fire 4. You could fire the 1A leading, 1B trailing, 2A leading, and 2B trailing (alternate which you fire) which might clean up the flame front propagation if using all 8 plugs is a problem.

 

I would say that if you fabricate a side seal that is a little taller you could set it in between the 2 rotors. Suspend it in the slot with a spring in each rotor and it should float free and seal.

To keep the 2 rotors together use corner seals that are twice as tall and suspend them with springs on both sides that should keep it all spinning at the same rate if there is a stationary at each end.

The oil cooling inside the rotors will not be a problm either. There will be a gap between the 2 rotor bearings. Put the jet there. There are slots on the gear side of the rotor where the oil can come out of. If I had the resources to make those couple of parts I would build one too.

I would use renesis rotors to help cut down the weight a bit. But that is just what I would do. I hope these ideas can help you along.

 

I've got to disagree about using seals to ensure the phasing of two joined rotors. Even if both will be phased with a stationary gear, one will always make contact before the other, such that one rotor will always be a little behind the other. When that rotor goes to transmit torque, it will definitely put a shear force through the side and corner seals, and I'd espect they'd snap very quickly. Whoever suggested aligning them very carefully and welding them together was on to something, I'd think.

 

why not cut two rotors and make one. cut the inside of each at the "dimple". then, weld them together. this is shorter than your plan, but a better setup IMO. i dont know what the displacement would be, but itd be larger than a 13b for sure. by cutting the side that has no stationary gear, your simply getting rid of the oil seals and all the extra dead weight that wouldnt be used. the only problem with that is. . . . finding a rotor housing that would work. cha-ching!!!

 

I would guess as long as your cutting things I wouldnt be hard to cut the housings also. Take an even amount off the matting surface of both housings bringing the spark plugs together.

 

Don't know if this helps...those KIWI-RE kits run 13B housings and use modified center-bearings and regular center plates...not the large, regular 20B center plates.....They call them "short-crank" 20B's....same work for 26B, check out Fourre, that red four-rotor FD, same principle.

Those kits include a shitload of parts to help the build...maybe $30,000-$40,000 for a 4-rotor complete. Compare that with trial and error fabrication.

THis pic is off a New Zeland Rx2. Short-Crank 20B P-Port/injected. SICKNESS.