Alright, I'm not finding much information on this so I thought I'd throw it out to the experts and fellow rotor junkies:

I've read that older rotary engines had a horrific catch. Changing the spark plugs required disassembly of the engine. What's the story with that?!? Was this just in NSU's engines? I can't seem to find any diagrams that details why this would be. I did 'read' something (in a language I don't speak...) that the spark plug may have been on the rotor itself. It makes me think that the distributor would have been integrated into the housing... Does anyone know anything about this?

Thanks in advance.

 

I think there was a design where the rotor was stationary and the housing rotated. You'd need the plugs to be in the rotor in that case, I would think. Either that or some very long plug wires

edit - ok here's more. This was the "DKM" variant of the rotary (Drehkolbenmotor
). Both rotor and housing spun on different axes.

http://cp_www.tripod.com/rotary/pg05.htm

Here's another link which mentions the DKM. The site is interesting because if you go to their site (starapex.com) and navigate through their annoying "next....next...next" links you get to see some 5-lobed and even 9-lobed rotary engine internals.

(this one is google cache only)
http://64.233.167.104/search?q=cache...2Brotary&hl=en

 

It most likely was a DKM

 

not on a modern rotary engine. They sit off to the side like any car. I watched Rotarygod yank them out of his 1stGen on Saturday with ease.

 

It was the first rotary design that Felix Wankel came up with that had a plug directly on each face of the rotor. The rotor spun inside a housing, and the housing spun inside yet another housing. It revved much higher because of this since each stage only revved a portion of the way towards to total. In order to change the plugs, you pulled the engine apart. Not very efficient when it comes to servicability.

 

My prior Mazda rotaries were a '72 RX3, '79 RX7 and '86 RX7. The plugs were all on the side, easily accessible to change. The older ones fouled faster, so had to change more often. The older ones were actually easier to change since there was less plumbing in the way.

 

That's what I figured. Thanks guys. I was fairly sure that Mazda never had this catch. I was just wondering how many did and why.

Just the one then... I found the diagram I was looking for:

http://www.nsumotor.onlinehome.de/dkm.htm

So after looking at it, it appears that the outer rotor served the same purpose as the E-Shaft does. That's pretty wild. However, they comment that it operated up to 17,000rpm. Is that the output rotor? It seems a bit high... Or can it because it was so small?

I'm thinking that understanding German would make it easier to find information on these initial rotaries...

Thanks again.