Rotary powered Dolmar KMS4

[kansei_rotary]

*Big Grin*

Sorry for just jumping in here (*newbie*), but I got a kick out of some of the replies posted here about the Wankel rotary in the KMS4 and in general. I am not an arborist, but an obsessed Wankel Rotary enthusiast and collector for a little over 14 years. Most of the posts about who has the rights to Wankels in the US, when they were put in what, etc. is a bit off (saying it to help, honestly not being an arrogant prick!). I would never challenge anything anyone here says about the KMS4, as I do not own one, but have been searching somewhat dilligently for around 8 years now (always get outbid or come to the party late), all I have on the KMS4 is a NOS service manual, though I have had my hands on two my friend owns (consecutive serial numbers too!!), though he does not use them, they are part of his collection. I do however have over 12 Mazda rotary vehicles (have had over 50), have multiple rotary snowmobiles, had an RE-5 Suzuki, etc., etc. If anyone has questions about the whole Wankel history, not to sound arrogant, I can probably answer it. If not, I guarantee you I have the lit or a book where I can find it. As most of you probably know, the whole Wankel rotary as we know it goes back to the 40s (but the principles date back to Aristotle), and since then has been put in not only cars, snowmobiles, motorcycles and the chainsaws, but also lawn mowers, boats (outboards and inboards), airplanes, generators, tanks, refrigeration units, helicopters, blenders (?!), etc., etc. The post of Alan Marr's site (www.monito.com) was a good one- he has a TON of info there. Definitely something to check out!

Neal "kansei" Swigert
www.kanseirotary.com
I'm obsessed, I tell 'ya!

'Cause the world goes round and round, not up and down!

 

[Chris J.]

Don't know jack about the saw, but now I'll definately keep my eyes open. What prices DO they command?

The Mazda RX7 owners that I've spoken with over the years love the rotary engine. I wouldn't mind a turbo RX7 just for kicks.

Many years ago a neighbor had one of the early models, a little econobox Mazda I think, and when the weather turned cold (cold relative to Houston) he'd have to let it warm-up for 15 minutes before he could drive it. A friend who was an fluids engineer and a total gearhead explained that in the early engines the 'flaps?' would wear down, and the engine couldn't build any compression until the metal got hot enough to expand and make contact with the 'flaps?.' I can't recall what the flaps are actually named, but he did say they started making the 'flaps' out of a longer lasting material.

 

[kansei_rotary]

Knot Whole...

Interesting you call the apex seals "flaps" because most (but not all) of the ex-employees I have spoken with over the years about the Wankel projects at Curtiss-Wright, John Deere, Sachs and even Mazda call them one of four things- apex seals (technically correct), flaps, tips and the Sachs' apparent favored term "wipers". Everyone I have spoken to calls all the other internal seals the same thing (corner seals, side seals, oil control o-rings, etc.). I have on occassion heard one or two people call the springs (such as apex seal springs, etc.) "coils", which I never really understood, since they are more akin to a leaf spring than a coil one.

Most of the early Mazda rotaries could have been called "econoboxes", but chances are your neighbor had an R100 (if it was really tiny) otherwise the other two smaller models were the RX-2 and RX-3. The RX-4, though roughly the same size, looked larger to most people due to it's styling, and the RX-5 Cosmo and REPU (Rotary Pickups) looked quite long unless parked next to one of the smaller models. I highly doubt he had a 110S Cosmo, unless he was a dealer or fairly well off back then. Those are very rare (less than 2k ever produced, less than 10 were ever brought here back then).

The warmup on the seals is basically accurate as it was told to you, but it wasn't the apex seals so much that relaxed in the cold as it was the seal springs, which therefore allowed the apex and side seals to "tuck" into their seal grooves on the rotor sides and apexes. As the engine grew older, then the apex and side seal surfaces would of course wear down, which increased the gap, and as the seal springs wore down (collapsed), the problem in cold weather starting only got aggravated (here's where the good 'ole ATF trick comes in). It also did not help that the earlier engines (pre-1974) had carbon alloy based apex seals, which wore down rather quickly compared to today's seals. The carbon based seals are still preferred for racer's today for one main reason- their softness. When an engine would detonate, the softer compound seals did not cause catastrophic results as often as today's seals do, because they would get broken into smaller fragments, and sometimes even find their way out the exhaust, often without completely destroying the rest of the engine, since they did not often get 'hung-up' and seize the engine, thereby ruining the rotor, housing, and possibly the eccentric shaft and forcing it at an angle off center. The phrase "blew an apex" really comes from the fragments getting "blown" out the exhaust system after failure (the older engines). Ianetti makes carbon based seals to this day as does Mazda for racers and are sold through Mazdaspeed, Mazda's old Competition Parts Department. The Ianetti seals can be found alot of other places in the aftermarket as well. Alot of the older Sachs and Curtiss-Wright engines have either really hard seals or really soft ones, as an ideal compound was not really found until the mid-80s by Mazda. Keep in mind most of the time, the engineers were more focused on creating a longer-lasting seal, not so much one that did not destroy the engine if it failed. That would have been a bonus to overcome.

Neal "kansei" Swigert
www.kanseirotary.com
I'm obsessed, I tell 'ya!

'Cause the world goes round and round, not up and down!

 

[Chris J.]

To repeat the question, and keep this about a chainsaw, what DO these saws sell for?

Neil, thanks for the detailed explanation. I sometimes drop in at the Stock Car Club of America (SCCA) gathering, and notice that the RX7 is still popular with a some of the drivers. It's not unusual to see a couple of early RX7s stripped down to the bare bones, and a few of the guys snatched up the 'jello mold' models before Mazda dropped the RX7.

 

[jonrodman]

Rotary Engine Seals

My understanding is that when the rotary engines were built during the seventies and eighties there was not a suitable material available to create the three seals between the rotor and the block. This resulted in inefficiency and short life expectancy.

Since then a material has been developed that works well for those seals and the rotary engine now has a chance.

Jon

 

[Chris J.]

I think that RX7 proved the rotary engine will work, but it doesn't appear that any major automaker is going to revive it for passenger vehicles. Maybe they're used in auto racing (which I don't follow, but my gearhead b-i-l does).

Aw ra best! Chris J.

 

[2Coilinveins]

Google "RX8" sometime. Modern production rotary.