Chainsaw heat shield

[cuttinupferalivin]

The number one enemy of any combustion engine is heat. Too much heat leads to countless problems, power loss number one and engine failure at the other end of the spectrum.
I deal mainly with Husqvarna saws and I noticed a major issue with those saws, something that to my surprise has never been mentioned in the countless threads I’ve read here and on other sites.
The problem is simple… the heat shield is directly mounted sungai at the hottest part of the cylinder. The shields are out there to deter muffler heat from the cylinder but in theory what they are doing is trapping heat against the cylinder, not allowing the cylinder fins to do their job of transferring heat, and pushing all that heat to the other important part of the saw, the carburetor.
The solution to the problem is so simple that I’m surprised that with all the degree wheel knowledge that it hasn’t been mentioned…
Either take the shield off the saw or better yet, make a spacer to go between the muffler cylinder and then place the shield against the muffler when reinstalling. This way you have a space between the shield or muffler for the cylinder fins to work allowing air to get between the two. No air cohagen, I can’t breathe…no aaar

 

[Wow]

I've made heat shields on generators. Many generators mount the muffler Next to the power head. A thin piece of metal BETWEEN the muffler and the power head with an inch of air space fixes the problem. Notice how often people are asking for replacement generators saying the motor runs good. Heat from the muffler causes insulation to melt. The generator then burns out. Warranty states. YOU must have overloaded it. No coverage. THEY KNOW THIS when they sell them. Thieves and liars. But no one can prove different. I went to college for electrical engineering. Im SURE that's not an honest mistake. China made. They LOL when they SELL. Glad YOU caught it BUT DON'T EXPECT anyone that could fix it to care. Oh but your fuel mix was wrong. No warranty. LOL. I know these dirty perros.

 

[cuttinupferalivin]

I've made heat shields on generators. Many generators mount the muffler Next to the power head. A thin piece of metal BETWEEN the muffler and the power head with an inch of air space fixes the problem. Notice how often people are asking for replacement generators saying the motor runs good. Heat from the muffler causes insulation to melt. The generator then burns out. Warranty states. YOU must have overloaded it. No coverage. THEY KNOW THIS when they sell them. Thieves and liars. But no one can prove different. I went to college for electrical engineering. Im SURE that's not an honest mistake. China made. They LOL when they SELL. Glad YOU caught it BUT DON'T EXPECT anyone that could fix it to care. Oh but your fuel mix was wrong. No warranty. LOL. I know these dirty perros.

Common sense goes a long ways…unfortunately it is lacking in todays world it looks to me like…
Look at any cylinder I n the exhaust side fins and most are browned from heat as opposed to the rest of it.
The muffler / shield might as well be one unit. They are both made of thin tin. The cylinder however is designed to dissipate heat. And the shield is directly against the hottest part. The spaces between the fins are designed so air can flow between them but as it is that air is trapped and guess what? Air heats quicker than any other thing !

 

[SweetMK]

Also, material selection is significant when discussing heat shielding.
Stainless steel is almost a perfect heat shield.
I rebuilt a Gravely tractor, and changed the muffler.

The new muffler was right over a tire,, and the muffler radiated heat right at the tire,
so much so that I was convinced it would damage the tire.

I cut a piece of thin stainless steel left over from some discarded appliance and formed a shield that could be bolted to the muffler.

After the cover was added, you can not hardly feel any heat at the tire now,,

I did also place two strips of stainless between the muffler, and the shield, to act as spacers.
Direct contact really increases heat conduction.

 

[cuttinupferalivin]

Also, material selection is significant when discussing heat shielding.
Stainless steel is almost a perfect heat shield.
I rebuilt a Gravely tractor, and changed the muffler.

The new muffler was right over a tire,, and the muffler radiated heat right at the tire,
so much so that I was convinced it would damage the tire.

I cut a piece of thin stainless steel left over from some discarded appliance and formed a shield that could be bolted to the muffler.

After the cover was added, you can not hardly feel any heat at the tire now,,

I did also place two strips of stainless between the muffler, and the shield, to act as spacers.
Direct contact really increases heat conduction.

Put

 

[cuttinupferalivin]

Puts a new meaning to the word tractor. Pretty impressive.
I hadn’t thought of stainless. I don’t have a metallurgy degree or anything but have studied various types and grades of metal and twenty yrs experience in metal fabrication and welding.
Anyway stainless is denser than most any metal and harder than any grade steel so it makes sense that it would not only absorb heat but it would also block it off if used properly.
Copper is suppose to be the best conductor of heat but the way I see it using it as a shield defeats the purpose altogether as it radiates all the heat very quickly back onto whatever it’s supposed to be protecting. I don’t know, that’s just my two cents worth

 

[cuttinupferalivin]

I’m thinking it’s a combination of air and material, the more air, ie:space the better and the denser thicker the material just as well

 

[SweetMK]

Puts a new meaning to the word tractor. Pretty impressive.
I hadn’t thought of stainless. I don’t have a metallurgy degree or anything but have studied various types and grades of metal and twenty yrs experience in metal fabrication and welding.

I did get the metallurgy degree from the "cow college" 40 miles down I81 from us,, although it was a long time ago,,
I hope stainless hasn't changed since then (LOL!!)
The two things that makes stainless a great insulator is
1) it is a poor conductor.
2) the surface has very low emissivity

All poor conductors are great insulators. A poor electrical conductor is a poor heat conductor.
As you mentioned copper conducts heat quickly, it also conducts electricity quickly.

A ceramic does not conduct electricity, and it almost does not conduct heat, ,BUT,,,
it is difficult to shape a brick into a muffler heat shield.

Also, a VERY shiny surface is VERY poor at radiating heat.
you can actually polish a surface, and it will radiate less heat.
So, the best heat shield is the most shiny surface material.

You can also ruin that aspect of stainless as a heat shield by simply letting it get dirty.
If the stainless heat shield gets oil on it, then the oil burns,, the shield is then less effective.

That is one of the reasons that wood stoves are painted black.
A flat black surface radiates heat the best.

If you want to decrease the heat output of a woodstove,, paint it shiny white,,
That is why many people put a new coat of "Stove Black" on their woodstove every year,,
That new coat of black gives you basically some "free heat" ,, until it turns gray,, again.

Some stoves are coated with shiny porcelain ,,
I think they do that to force the inside temp of the stove to stay higher,, to change the burn characteristics of the stove.
But, that is another topic,,,,,,,,,,,,,,,

 

[cuttinupferalivin]

Ty for the knowledge. I guess I’ll try to find a small pice of stainless.
A 4 ¥ 8 sheet of 16 g metal was 387.00 couple wks ago when I was at the metal place in Lynchburg…. I’d be willing to bet it’s more than that now…
Do you have a store nearby?

 

[cuttinupferalivin]

No surprise how those farmer tec saw kits a lot of people build on this site has sluminum heat shields in the kits….shows how much they know. They seem to be slacking here in these latter days. Wonder what up w that ….

 

[SweetMK]

Ty for the knowledge. I guess I’ll try to find a small pice of stainless.
A 4 ¥ 8 sheet of 16 g metal was 387.00 couple wks ago when I was at the metal place in Lynchburg…. I’d be willing to bet it’s more than that now…
Do you have a store nearby?

I cut mine from some old appliance, so free,,
A muffler shield sized piece could come from eBay for about $10 shipped.
There is a junk yard near the Salem Dog Park that would sell you a piece for a few $,,
From the dog park, continue down the road until you cross RR tracks,, you will be at the scrap yard.

 

[SweetMK]

Oh, yea, here is how that tractor arrived at my place,, after I picked it up at a scrap yard in Culpeper,,

The machine had 61 hours on it, then parked,, to rust away.
It ran like new, after I cleaned it up,, and put a new carb on it.
Chainsaws are not the only neglected machines!! LOL!!

 

[ElevatorGuy]

Culpepper va?

 

[SweetMK]

Culpepper va?

Yes

 

[ElevatorGuy]

Yes

One of our guys lives down there. I’m across the Potomac in southern MD.

 

[Wow]

No surprise how those farmer tec saw kits a lot of people build on this site has sluminum heat shields in the kits….shows how much they know. They seem to be slacking here in these latter days. Wonder what up w that ….

Actually I prefer Thin aluminum..Spaced with at least 1 inch of air space..THEN I have a Fan blowing across BOTH sides of the metal..The idea is.. THE thin metal DOES NOT hold heat like a heavy metal does.. Example... The cast iron frying pan..I want the thin metal to absorb heat and dissipate it quickly..This has proven to work well for me..IF a very difficult situation I like to space the metal in TWO sheets with at least half an inch between the two and air flow..I use fans on my generators..What I found testing with an infra red thermometer is the Heat shield already factory installed on the 5500K Watt was thick and in the first few minutes worked well UNTIL the muffler managed to heat it very hot. THEN it was as IF the muffler had been moved closer to the generator..My cure was a THIN sheet of metal attached but spaced away from the heavy metal..Then the fan cools it well.. Look how thin the fins are on a radiator..Thin looses heat quickly. It's easy to heat two pieces of metal and give this a test..The Heavy Iron skillet cooks eggs after it's hot and removed off the stove. Use a Thin frying pan.. Heat BOTH to the same temp..Remove off heat and toss an egg into each one..IF both are setting on the same type of medium the heavy Skillet will fry more eggs the thin one will cool faster..Before and After photos. Sorry but I could not get only two photos..I deleted the doubles and all of it went away.. This is my third try..WHen I got the Generator it had ONLY 1 heat shield.. OUTSIDE.. ThE generator got hot fast..THIS cured it.. I use this all the time. Blessings.

 

[scottr]

The number one enemy of any combustion engine is heat. Too much heat leads to countless problems, power loss number one and engine failure at the other end of the spectrum.
I deal mainly with Husqvarna saws and I noticed a major issue with those saws, something that to my surprise has never been mentioned in the countless threads I’ve read here and on other sites.
The problem is simple… the heat shield is directly mounted sungai at the hottest part of the cylinder. The shields are out there to deter muffler heat from the cylinder but in theory what they are doing is trapping heat against the cylinder, not allowing the cylinder fins to do their job of transferring heat, and pushing all that heat to the other important part of the saw, the carburetor.
The solution to the problem is so simple that I’m surprised that with all the degree wheel knowledge that it hasn’t been mentioned…
Either take the shield off the saw or better yet, make a spacer to go between the muffler cylinder and then place the shield against the muffler when reinstalling. This way you have a space between the shield or muffler for the cylinder fins to work allowing air to get between the two. No air cohagen, I can’t breathe…no aaar

What model Husqvarna saw are you talking about ?

 

[sand sock]

My Stihl 361 has a heat shield, between the muffler and cylinder. It's hard to believe that Husqvarna sdont

 

[cuttinupferalivin]

My Stihl 361 has a heat shield, between the muffler and cylinder. It's hard to believe that Husqvarna sdont

The thing is there needs to be some space between the shield and cylinder. As it stands the shield might as well be a part of the cylinder or… even worse in my opinion as the fins on the exhaust side of cylinder are trapped thus producing more heat than if no shield were there . I used a 272xp as an example. I used a older model muffler from a 61 as the design of that particular muffler is, slightly concaved which pushes the back of the muffler housing away from the mounting flange, which is in its original place, placing about a 1/4” of usable space between the main body of muffler and cylinder. This would’ve been sufficient in itself for the intended purpose and I have no clue why Husqvarna went to the flush mounted mufflers on their “ updated “ 272 models…. Anyway, I took it a step further to decrease the temp where cyl scoring occurs most often and made a 3/8” spacer from a piece of sheet steel, and placed the shield against the muffler in front of spacer. So the spacer mounts directly to cylinder giving an adequate amount of space, in this case with gasket, shield, and 3/8 spacer combined, 1/2” , for the fins to both dissipate heat and for air to cool it all.
The muffler should be hot as gases flow faster through hot pipes…
Taking my fellow neighbors advice in the post above, I plan next to put a flat black coating on the entire cylinder and top cover as well.
I can see a very noticeable gain on the 61 I recently assembled using a 52mm cyl, older muffler and shield mods…
The mufflers on these things btw is where the real gains are achieved… playing with muffler volume(size) baffles, (to create the effect a expansion chamber of sorts, and port size… larger is not better on these things… On the spacer I simply put a slight but noticeable concave( wider at port entrance, smaller at exit at muffler, which sped up the velocity. I used a internal baffle and two piece muffler from a 61 and worked a hole in baffle as it was solid with a dozen small screened holes in it. In effect it made the perfect part to create a two part expansion chamber as the small holes release any excess back pressure and the larger hole in it made a simple expansion chamber
Not to brag but it sounds pretty Damon impressive and it will cut with perhaps out cutting my modded 52mm 372.
Cheap effective reliable power makers…

 

[cuttinupferalivin]

You might should also remember when messing with these things that the manufacturers of high volume items stock thousands upon thousands of replacement parts for these things which are priced at 50 percent or more than what they would’ve cost on a complete saw …and…. They didn’t have to pay for the saws to be assembled….so who cares if the shield is just there to make the cylinder hotter?