MCCULLOCH The official McCulloch thread

[Al Smith]

I was never real certain what that "reed" muffler was supposed to do other than rust shut .

 

[Stump Shot]

I was never real certain what that "reed" muffler was supposed to do other than rust shut .

I believe it was supposed to give more power across the entire band by having a variable exhaust outlet.

 

[Bigmac]

My understanding it was all for sound

 

[Al Smith]

It way have because that series was not the most quiet ever built .Never the less the way I see it with a narrow mind is you have two speeds on a chainsaw most of the time .Idle and wide open .
With a kart engine on a road course or a moto-cross scoot you have varied RPMs depending .My neighbor had I think a 28 HP high end 125 cc scoot with a pipe that had a "power valve " depending on the R's .I tinkered with it and got it to work actually knowing very little about it .That little rascal would wheel stand with just a blip of the throttle with that valve working .With out it lagged a wee bit coming up .

 

[Stump Shot]

My understanding it was all for soundView attachment 201242

I think that pre dates the reed valve exhaust of the Pro Mac's.
I do recall all the older folk that had 10-10's for firewood all saying about the same thing, "that dam thing was loud, took it to the dealer for a new muffler and it came back louder than before".

It way have because that series was not the most quiet ever built .Never the less the way I see it with a narrow mind is you have two speeds on a chainsaw most of the time .Idle and wide open .
With a kart engine on a road course or a moto-cross scoot you have varied RPMs depending .My neighbor had I think a 28 HP high end 125 cc scoot with a pipe that had a "power valve " depending on the R's .I tinkered with it and got it to work actually knowing very little about it .That little rascal would wheel stand with just a blip of the throttle with that valve working .With out it lagged a wee bit coming up .

Two Speeds... here's where it gets kinds murky, think more in the line of two throttle positions, the rpm varying greatly though in each different individual cut.
As a much later example of the idea of this is the much more sophisticated R.A.V.E. valve by ROTAX that boosted power tremendously in their 2 stroke engines.

At any rate, the one I had was broken and it cost me $50 to see for myself what goes on with it. The mail man should be bringing the kit for the carb today and while it's a good soaker of rain day, at least fire it up out in the wood shed and at least make some noise and get it in tune.

 

[Bigmac]

I think that pre dates the reed valve exhaust of the Pro Mac's.
I do recall all the older folk that had 10-10's for firewood all saying about the same thing, "that dam thing was loud, took it to the dealer for a new muffler and it came back louder than before".



Two Speeds... here's where it gets kinds murky, think more in the line of two throttle positions, the rpm varying greatly though in each different individual cut.
As a much later example of the idea of this is the much more sophisticated R.A.V.E. valve by ROTAX that boosted power tremendously in their 2 stroke engines.

At any rate, the one I had was broken and it cost me $50 to see for myself what goes on with it. The mail man should be bringing the kit for the carb today and while it's a good soaker of rain day, at least fire it up out in the wood shed and at least make some noise and get it in tune.

It will be a cool test, let us know the verdict, I agree with the throttle response, and a power valve is a whole other topic.

 

[Dream]

I'm interested as well. Havent even checked the good one or the parts saw I picked up this spring to see if they jad a different muffler. My 1010S just has a right angle coming from the exhaust port that dumps out the side. All of my Macs are loud, and thats the way I like it.

 

[Al Smith]

The muffler with the curvature in the bottom would seem to me to be the best .Fact I have one from an early 10-10 righty on a 6-10 (70 cc ) .No baffle plate, louvered cover ,loud enough to make dogs howl and raise the dead .Fast for what it is .

 

[Dream]

Ok, so I got curious.
The 700 carcass I have has the (broken) reed muffler, as does my running 700. The runner seems to have a screen behind the reed. My 1010S doesnt have the reed muffler.

 

[Dream]

Oops. Sorry for the repeat image.

 

[heimannm]

I put a NOS reed muffler on an SP70 I rebuilt, may have been a NOS piston and cylinder as well but I don't recall at this moment. The saw was so quiet I thought something was wrong with it and believed it did not perform well....until I ran it side by side with a few other 70 cc McCulloch saw and found none could keep up with it in the cut.

The reed mufflers do have a very characteristic pop to them when the saw is running.

Mark

 

[fossil]

Here's the patent application for the MAC reed muffler and what it's supposed to do. I'll leave it to you guys to figure whether it worked or not. I can't hear much if any difference in the noise myself.

Read the 4th paragraph which I've set in bold type for the summary

Description
May 9, 1967 J. R. BAILEY MUFFLER WITH REED VALVE Filed March 17, 1966 '3c l' Q l",

INVENTOR WHA NN I Mc MAN/GAL United States Patent Office 3,318,412 Patented May 9, 1967 3,318,412 MUFFLER WITH REED VALVE Jay R. Bailey, Woodland Hills, Calif., assignor to McCulloch Corporation, Los Angeles, Calif., a corporation of Wisconsin Filed Mar. 17, 19,66, Ser. No. 535,185 Claims. (Cl. 181-65) This invention relates to mufflers, and more particularly, to mufllers for internal combustion engines.

The example shown and described is a muffler for use on a small internal combustion engine. However, the principles involved are applicable for any size engine and for any size muffler.

The traditional approach of using an acoustic filter to attenuate two cycle gasoline engine exhaust noise in small engines has not been successful. For a small engine, as may -be used for a chain saw, the ymuffler must be restricted in size and this results i'n the filter cut-'off frequency not being low enough. The sound level' of a two cycle engine is high over a broad band o f frequencies, and thus, even the noise in the low frequency bands must be attenuated. In addition, the sound waves emitted from a two cycle gasoline engine are trains of discrete sharpfronted pressure pulses of shock-wave severity. Hence, the laws used for ordinary acoustical phenomena do not fully apply.

It has been found, according to the invention, that by introducing a reed into the exhaust stream the sharp fronted pressure pulses are smoothed out, that is, blunted and the noise energy is spread over a longer period. The net effect of this is to attenuate the sharp high noise peaks. Further, the high intermittentlv pulses of very short duration are reacted by the inertia and the spring force of the thin reed, cantilevered on the muffler to act as a valve on the exhaust discharge opening. The reed in turn returns the energy V to the exhaust stream. The metal reed must be designed to be thick enough to avoid resonance which could cause loads high enough to destroy the reed and thin enough to avoid back pressure which could create a horsepower loss.

The reed dimensions are such that its resonant frequency is above the highest exhaust pulse frequency of the engine and its stiffness is aslow as possible in order to avoid excessive `back pressure. The deflection of the reed must be limited by a reed stop. The shape of the reed stop and its distance from the exhaust opening, over which it extends, is determined by the exhaust exit requirements and the allowable stress levels for the reed. The configuration of the reed stop matches the fully deflected shape of the reed. Since the exhaust kacts as an equally distributed load on the reed, the configuration of the reed stop is determined by the deflection curve of a beam loaded by its own weight. The exhaust discharge opening at the reed and the engine exhaust outlet or muffler inlet are designed to be of substantially the same area.

It is an object of the present invention to provide an improved muffler for noise attenuation.`

The complete application is here,

https://patents.google.com/patent/US3318412

 

[Al Smith]

Not to get on a high horse ,just info .Noise attenuation can be attained several ways .One has been mentioned and that being bouncing sound waves into each other which has a tendency to cancel each other .

 

[Dream]

So it was designed solely to reduce noise. Not sure on any claims of added power. Most people open the new restricted mufflers to increase performance, but that's not to say the Macs style of porting wouldnt benefit from some back pressure.
In my limited line of thinking, the reed would not fully close at mid to full throttle ranges. I could be wrong. Best way to tell would be a with and without comparison on the same saw.
I noticed on ebay that there are two styles of muffler offered. The ones with the reed, and one with a screen in its place. I'm assuming the screen was a replacement that Mac offered after the reeds started having trouble with breakage. My 700 runner has the screen. The parts saw has the broken reed.
I'm curious, but not enough to drop 50 bucks on a NOS reed muffler. I'm thinking I'll take the broken one to a customer of ours. They have a Rockwell hardness tester. If I can figure out what its made from, I can make one to test with.

 

[Stump Shot]

Well, after just getting the saw running good, I think that patent should be revoked. Lol

 

[Dream]

So your results were less than exiting?

 

[Al Smith]

Most horizontal cylinder Macs will really wind up with an open exhaust but you might have to open up the low speed until it blows black smoke and nearly loads up at idle .Problem is if you use them like that damned things will blow your ear drums out .That 6-10 I mentioned is just a big kids toy,I don't use it .It was just an experiment I did to see what I could do with a 10 series and it proved to be okay .It was a take it to a GTG and have them shaking their heads --and they did .--you have to have a little fun now and again .

 

[FergusonTO35]

My understanding it was all for soundView attachment 201242

What's the deal with those clutch side starters that Mac used for several years? Looks like it would be a good way to get your recoil filled with chips.

 

[Bigmac]

What's the deal with those clutch side starters that Mac used for several years? Looks like it would be a good way to get your recoil filled with chips.

Ya I don’t like the design, the 797 is the same way, the, the recoil is sealed so that doesn’t happen, still don’t like it!

 

[heimannm]

The screens were made available and/or added at the factory for the purpose of arresting sparks and were required for saws being used in federally owned lands, perhaps other areas as well. There were several Mac Service Bulletins on the subject.

Mark