amgtortoise

I remember a while back (2001) when a wealthy customer from northern Florida brought a custom made 4-rotor at Roger from Mandeville Auto Tech (Spartanburg, SC) with a prototype e-shaft from New Zeland (Precision Engineering) made out of chrome-moly (I think it was a one piece unit?!).

The customer broght it assembled & wanted Roger to tune it with a Motec. Apparently, Precision Engineering thought they could make a 4-rotor by putting 2 x 13b inline (unlike the Mazda 3 piece 4-rotor e-shaft which had a 90 degree between rotors). The e-shaft design was out of wack! The engine had so much vibration & flexing... it was scary at the engine dyno. The 4-rotor was not being able to be balanced & also, I think the ignition was firing 1 & 3 / 2 & 4 rotor at the same time. I've never heard from that 4-rotor again which I don't think it will ever work. The e-shaft bent too I think.

Short story said... It's not impossible to make a custom 3-rotor or 4-rotor e-shaft... it's a matter of proper engineering. And, I'm sure that project cost him lot's of money & time. And, of course how many people out there can afford a Mazda 4-rotor & have the credentials to lease one from them =P

rx-8club.co.uk

There are a few 4rotor's running around now and a number of 3 rotors with CNC'd shafts.

I'm getting one: www.4rotor.com

rotarygod

Precision Engineering is headed by a man named Jeff Bruce. He actually really does know what he is doing. There are several ways of doing a custom 4 rotor shaft. The easiest way is to machine the front and rear of 2 of them to fit together with a keyway. Another way is to completely machine 4 seperate lobes and have them all attach together with the keyways. Mazda did it a little different by machining the outer most sections to slip onto each end. Every method has been tried and worked very well.

Jeff knows what he is doing. It sounds like the error came from the wrong counterweight(s) on the ends of the eccentric shaft. As an example, the 2nd gen RX-7 depending on year model had one of 2 different weight counterweights. The newer rotors were lighter. However when you picked up the counterweights you couldn't tell one from the other. The only way to tell the difference is with postal scales since the difference is so small. If you mix them up though the engine will feel like it is falling apart. It is quite impressive how much a few ounces weighs when it is off center and spinning really fast. Inertia is a neat thing. Jeff does make very good products and I wouldn't blame the issue on him.

The Hitman in Australia is running one of his 3 rotor engines. He did bend an e-shaft but only after an oil line broke. A bearing seizure caused an instant stop to the front of the engine. Obviously the back still wanted to spin and it twisted slightly.

That engine was probably dead from other oversights. The counterweight is my best guess since you can just order an e-shaft from Jeff without them included. Many other things can go wrong. It is true that you can build one and that it does have to be engineered correctly. You also have to put the rest of the correct parts on it too.