4 stroke or rotary saws???

[Ironmower]

OK, since I got your attention ;D, is any of the manufactures workin' on one ??? I love my 2-strokes just as much as the next fella, but we all know things are going too be very different soon >:(. Having alittle mechanical apptitude, weight aside, couldn't you gear-up the final drive to get the RPM up on the chain? Less RPM more torque :.....................  I've always thought the rotary engine design would make a great saw,few moving parts and endless RPMs ...............Have any thoughts?

[tyb525]

This reminds me of when motocross bikes (dirtbikes) were 2-stroke only. Then Yamaha came out with a 4-stroke, and everyone thought it would be a joke. Lo and behold, after a few years 4-stroke dirtbikes are at least as popular, if not more popular, than 2 strokes. I don't think I've seen a rotary one yet though. There are still debates about which is better.

I think it could be done, just might take some time. As far as which would be better, time will tell I suppose.

[Ianab]

It's been done with the Wankel engine.



http://www.youtube.com/watch?v=teEREL4BMGo

Dolmar KMS-4 from the 70s

So yes it can be done.

Ian

[fishpharmer]

Stihl is making 4 stroke weedeaters now.  I can see it coming.

Look at outboard motors.

I wonder if a Wankel engine would meet emission standards without losing too much efficiency?  I can imagine a rotary engined saw would be smooth running.

[ladylake]

 Most likely will end up with direct injection 2 stroke saws, they have outboards and snowmobiles running clean like that.   Steve

[Ironmower]

Ianab, can you tell me more; was this a prototype? how is it too operate compared to a "standard" saw of the same era? what size is it?................. and where can I find one to buy? Maybe yours ;D........ Whats your professional opinion on that saw?.....Thanks for the vid. & your time ;)

[Ed]

The Dolmar rotaries were a production saw. IIRC, they were recalled due to a nasty habit of catching on fire.
When one comes up for sale it usually commands a premium price because rarity and chainsaw collectors wanting one.

Ed

[Reddog]

Also if I remember right they where quite heavy for the power output at that time.

[Ed]

Specs: http://www.acresinternet.com/cscc.nsf/ed1d619968136da688256af40002b8f7/bc2f06b3baf2203388256af90060c147?OpenDocument

The specs are interesting to say the least......

58cc
8hp
19.6 lbs

Ed

[Modat22]

Wankle engines do fairly well in cars the biggest problem they have is with the rotor sealing surfaces inside the engine (kinda like piston rings). These areas wear down in proportion to the number of revolutions and load over time.

The smaller the engine the faster it must rotate to generate the needed torque. Faster rotation, smaller sealing surface plus high load equals an engine in need of a rebuild very soon. I suspect the problems with the market saw where related to this problem.

Then again this in an opinion and I could be completly wrong.

[Ianab]

The rotor tip seals were probably a weak point with the saws. They were in the Mazda rotary cars of the same vintage. But Mazda seem to have solved that with high tech ceramic material for the seals and are still making Rotary engines.

Catching fire at random might have caused a marketing problem as well, but that shoud be fixable.

I dont know of any current Wankel engine power tools, but you can buy a model airplane engine.
http://www.osengines.com/engines/osmg1401.html

Ian

[Ironmower]

Thank ya'll, wonder why they didn't use direct injection for the new dirt bikes? The sound of my old '87 Can-am 406 air cooled Rotax was music too my ears smiley_hillbilly_tub_base. My "little" brothers both race motorcross, one rides a '09 KFX 450 the other a '09 YZF 450........ Nice bikes, but they're a whole nother animal. The 4-stroke 450's is what took over the 250cc 2-stroke classes >:(........They'll be sadly missed :'(

[Ironmower]

Found this in my Farm show mag. the MYT engine;www.angellabsllc.com      Could you imagine a power head like that ???