Pioneer rotory saw?

[JohnL]

Copied form another forum

As a retired power boat racer, I keep up with the vintage web sites of racing in the 60's, 70's and 80's. There is one contributor, Rotary John, that was an engineer with OMC whose speciality was in the rotary engine field. This is only a small segment of a much larger story that I found very interesting

"Pioneer Chain Saw was another OMC company. Vibration was
becoming a major issue with chainsaws. Long-term exposure to
chainsaw vibration caused Reynolds disease in the hands of
the user. Some manufactures chose to use vibration isolation
to help reduce the problem, but this added considerable cost
to the unit. Pioneer wanted to use a rotary as it was
dynamically balanced with only torsional inputs. As a side
note, nobody figure out at the time that the vibration input
from the chain cutting wood was equal in vibration to the
piston engine. I was assigned the project to design and
develop a 5 hp air-cooled engine for a chainsaw. Pioneer
engineering would incorporate the engine into a new saw
design. Knowing 1 hp per ci was feasible, I decided on 5 ci
for the displacement and copied the snowmobile cooling
arrangement. This meant a very high performance fan to be
able to cool the engine properly. Normally chainsaws had the
starter on the left side, but because of the airflow
restriction caused by the starter, I told Pioneer, the
starter could not be in front of the fan. The starter on the
left was to allow closer clearance from the ground to the
bar and chain. Pioneer didn’t want to give up this
feature, so they designed a swing arm starter like some of
the outboards used. To use this type starter and get back to
the crank resulted in a 2 to 1 reduction in cranking speed.
I know now this is not something you want to do with a
rotary. Many design innovations were used on this engine.
The stationary gear, rotor, buttons and apex seals were made
with the powered metal process (sintered metal). The
trochoid was chrome plated. The side housings were
hi-silicon aluminum requiring no addition wear surfacing.
Prototypes were made and assembled. Dyno testing confirmed
5hp at 7000 RPM, but cooling was an issue. No failures
resulted from the high temps, but performance tapered off as
the temps rose. It was felt that chainsaw typically didn’t
run at WOT for extended periods and thus this may be
acceptable. The day came to install the engine into the new
saw. After a couple of tweaks, it was ready to try cutting
wood. After pulling on the starter for God knows how long,
it became apparent the swing arm reduction starter was not
going to crank the engine fast enough to start. We did what
all good engineers would do. Cut a hole in the starter
housing and get out the electric drill with a socket. The
engine started, but threw the socket beyond retrieval. The
saw performed well and cut wood like a banshee. That’s
when I learned what sawdust coupled with tree sap did to
cooling fins. It didn’t take very long before temperatures
started rising beyond acceptable levels. We also learned
very quickly what saw chain induced vibration meant. At this
point in the development, it was apparent vibration
isolators would be required to tame the saw chain vibration
and thus the advantage of the rotary was diminished because
of the cost of the two together. The project was stopped."

 

[stinkbait]

That's very interesting.

 

[Rookie1]

Very cool article. Thanks for sharing.

 

[shortlid]

Rotory have good rpm range but not much touque. Would have had to be used a WOT from the the time it toched wood till it was clear, I would think.

 

[demographic]

Rotory have good rpm range but not much touque. Would have had to be used a WOT from the the time it toched wood till it was clear, I would think.

The Norton that raced at the Isle of Man didn't do to bad with its rotary mill

 

[Banacanin]

Torpedo Saw

Copied form another forum

This is not exactly gas rotory engine related, but I was wondering if anyone ever experimented with pneumatic engines? A few years back, before my job went to Mexico and I had to go back to school, I used to earn an honest living making air brakes for frieght trains. I say honest because now I work for Lawyers.

Anywhoo working in the rail industry I was absolutely amazed how much power can be harnessed from compressed gas. Over a hundred years ago Mr. Westinghouse's engineers devised a system where a sudden drop of 3psi will set into motion a process that will stop a train that is a mile long! The system depends on very large volumes of gas under low pressure. It was the perfect system for stopping a large vehicle safely and it is still employed, albeit in a very refined form, today. I know that in this day and age there is research being done on making compressed air automobiles and heavy equipment using very small volumes of various gases (some inert, others not so much) under very high pressure(3-7 kpsi).

With this in mind, is anyone aware of any Pneumatic Chainsaw projects?

 

[reel_story]

DOLMAR's Rotary Engine Saw (KMS 4)

DOLMAR made a rotoray engine saw in colaboration with Fichtel and Sachs.

http://www.dolmar.com/company/history/80_years_dolmar.html

 

[HimWill]

Do any of you Pioneer guys have any more info about this prototype saw?I wonder where it ended up.

 

[Bill G]

DOLMAR made a rotoray engine saw in colaboration with Fichtel and Sachs.

http://www.dolmar.com/company/history/80_years_dolmar.html

Yes they did.

Bill

 

[HimWill]

This is not exactly gas rotory engine related, but I was wondering if anyone ever experimented with pneumatic engines? A few years back, before my job went to Mexico and I had to go back to school, I used to earn an honest living making air brakes for frieght trains. I say honest because now I work for Lawyers.

Anywhoo working in the rail industry I was absolutely amazed how much power can be harnessed from compressed gas. Over a hundred years ago Mr. Westinghouse's engineers devised a system where a sudden drop of 3psi will set into motion a process that will stop a train that is a mile long! The system depends on very large volumes of gas under low pressure. It was the perfect system for stopping a large vehicle safely and it is still employed, albeit in a very refined form, today. I know that in this day and age there is research being done on making compressed air automobiles and heavy equipment using very small volumes of various gases (some inert, others not so much) under very high pressure(3-7 kpsi).

With this in mind, is anyone aware of any Pneumatic Chainsaw projects?

I believe Stihl had (maybe they still do) some industrial saws that were pneumatic.They definitely made some heavy duty electric saws.

 

[eyolf]

Do any of you Pioneer guys have any more info about this prototype saw?I wonder where it ended up.

Never heard of this saw, but I knew a former engineer for AMC once upon a time. Seem like in the late 1960's AMC wanted to have an engine to compete with Pontiac's OHC six, designed and sand-cast a few aluminum heads in a standard pushrod formation, but with bigger valves canted like Chev's semi-hemi big block. They got some more HP, but more was wanted, so they stole Ford's chain-driven 427 "cammer" idea and applied THAT to the old 258.

Lots of HP, but they couldn't hold 'em together. The project was abandoned, and the parts were sold as scrap. The engineer I knew still wept over that one in 1980.

 

[Brmorgan]

Dolmar KMS-4

Here's a vid of the Dolmar KMS-4, the saw they designed with the Wankel rotary engine:

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Gotta love that rattle in the idle, definitely one of the most unique ones I've heard. Not a speed demon, but I think it performs pretty solid in the video.

I never heard about Pioneer developing a rotary though. That was an interesting read, thanks.

 

[belgian]

This is not exactly gas rotory engine related, but I was wondering if anyone ever experimented with pneumatic engines? A few years back, before my job went to Mexico and I had to go back to school, I used to earn an honest living making air brakes for frieght trains. I say honest because now I work for Lawyers.

Anywhoo working in the rail industry I was absolutely amazed how much power can be harnessed from compressed gas. Over a hundred years ago Mr. Westinghouse's engineers devised a system where a sudden drop of 3psi will set into motion a process that will stop a train that is a mile long! The system depends on very large volumes of gas under low pressure. It was the perfect system for stopping a large vehicle safely and it is still employed, albeit in a very refined form, today. I know that in this day and age there is research being done on making compressed air automobiles and heavy equipment using very small volumes of various gases (some inert, others not so much) under very high pressure(3-7 kpsi).

With this in mind, is anyone aware of any Pneumatic Chainsaw projects?

Pneumatic chainsaws were developed a long time ago and still are used in area's where there's risk of explosion, such as in mining operations. Pneumatic ones also can be operated under water, that's why they were used also by the engineering corps during the war.

Reed-Prentice, Danarm, Dolmar, etc. have made such models. The problem is always that you need a large air compressor and hoses...not really practical in the field. I have a few in my collection.

 

[Brmorgan]

I believe there were a few hydraulic-driven saws designed for the same purposes, no? Much more efficient than air at any rate.

 

[deezlfan]

Rotory have good rpm range but not much touque. Would have had to be used a WOT from the the time it toched wood till it was clear, I would think.

Since a rotory engine makes 3 power strokes per revolution and a 2 stroke only makes one, I can't understand why it would not make more torque. Please elaborate.

 

[Wildman1024]

Since a rotory engine makes 3 power strokes per revolution and a 2 stroke only makes one, I can't understand why it would not make more torque. Please elaborate.

If the saw is anything like my RX-7's I have had then you would need a good counterweight on the eccentric shaft to make torque. I wouldn't wanna carry around or use a 30lb 60cc saw.

My increasing the counterweight you would increase your torque but it would rev slower and by reducing your counterweight you lost some torque but would rev a lot quicker. Rotary's really don't make alot of good torque since the rotational mass is very light and doesn't have the "Stop and Go" like a piston engine has...Just my .02

 

[Banacanin]

Pneumatic chainsaws were developed a long time ago and still are used in area's where there's risk of explosion, such as in mining operations. Pneumatic ones also can be operated under water, that's why they were used also by the engineering corps during the war.

Reed-Prentice, Danarm, Dolmar, etc. have made such models. The problem is always that you need a large air compressor and hoses...not really practical in the field. I have a few in my collection.

Thanks Belgian, thats kind of amazing that a saw can be operated under water. I imagine that could be pretty handy for rescue workers as well.


I imagine the inside of one of those looks a lot like the inside of an impact gun. As you pointed out you need a compressor and hoses to run one of those, I wonder if anyone is working on high pressure, low volume systems?

 

[eyolf]

Another problem with the rotary (Wankel) engine is the fact that high compression ratios aren't possible. High compression ratios wring more energy out of the fuel burned and convert it into force that can be used more effectively.

 

[Wildman1024]

Another problem with the rotary (Wankel) engine is the fact that high compression ratios aren't possible. High compression ratios wring more energy out of the fuel burned and convert it into force that can be used more effectively.

Yea its tough to make a "triangle" with high compression...But you can basically "Force Feed" them whatever you want either threw a turbo or Super Charger! That would make for an interesting chain saw though! Can anyone say one of a kind HOTSAW

 

[demographic]

I know I'm taking this a bit out of context but I'm interested in bikes and feel that its worth showing what a good rotary engine can do.
This is taken from another web page...

NRV588 Fact Pack

588cc twin-rotor Wankel type engine.
Fuel injected, direct spray into both bellmouths.
Fully variable intake tract to peak maximum torque between 8000rpm and 11,000rpm.
Electric water pump.
Ducted fan air cooling for rotors.
'Fly-by-wire' throttle
Power: 170bhp @ 11,500rpm
Chassis: Twin spar aluminium, by Spondon
Suspension: Ohlins USD forks, rear Ohlins long-stroke single-sided direct connection unit
Brakes: AP Racing systems with radially mounted front calipers
Wheels/tyres: Dymag 16.5-inch, Dunlop
Dry weight: 130kg