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 Post subject: Muffler Shield
PostPosted: June 20, 2018, 3:14 pm 
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Joined: April 22, 2010, 4:43 pm
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Location: Livermore, Calif.
Anybody have a good source for a perforated muffler shield? I've tried a number of places. Some have shields for side mount exhaust pipes but are usually too long.

Thanks in advance,
Roy

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 Post subject: Re: Muffler Shield
PostPosted: June 20, 2018, 5:31 pm 
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Joined: September 16, 2009, 9:36 am
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McMaster has perf sheets but you would have to form it.


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 Post subject: Re: Muffler Shield
PostPosted: June 20, 2018, 5:40 pm 
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Thanks berg-
I thought about that. I noticed that Online Metals also has perforated S.S. sheet. I used to have access to a small roller that would allow me to roll the sheet. I guess I could try to form it around a pipe similar to what I did for the hood curves.

Does anyone have an idea what the typical thickness would be for the S.S. sheet used on some of these shields?

I'll keep looking for ideas.

Roy

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 Post subject: Re: Muffler Shield
PostPosted: June 20, 2018, 6:13 pm 
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Around .050 should work well with enough support and take small stone damage.

Why do you want holes in your heat shield? Just curious.

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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 7:20 am 
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Roy
Look for vertical exhaust shields. They are long enough, and typically have a couple solid band sections so you can cut it down and get two or three shields cut from one. You can easily sell the other sections here. DaveW


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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 7:27 am 
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Also, if your only looking for a guard, consider flattened expanded metal in 304 or 316 and .050 or thicker. Very affordable in 2x2 sheets that can be split and rolled to cover 4 feet.

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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 11:09 am 
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Joined: March 30, 2011, 7:18 am
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Location: central Arkansas
Short pieces of perforated shield are available for motorcycles, big pieces from truck accessory shops. Search "perforated muffler shield" for some hits.

Note the shields don't *have* to be perforated, leftover sheet metal from the body would work okay.


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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 12:04 pm 
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Now, I don't know the answer to this for sure, but I'm wondering if the perforated shields retain less heat under operating conditions. Sooner of later, someone will come in contact with it (maybe you). Is a perforated shield less likely to burn you when you do touch up against it?

Based on intuition, I suspect it may be so.

Cheers,

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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 1:01 pm 
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Well, this is just off the top of my (bald) head. It seems to me that the perforated metal would dissipate the heat more quickly with airflow over, under and through rather than just over, and under with the solid sheet. If nothing else, the perforated stuff would leave a more interesting burn pattern in case of direct contact with the skin! :shock:

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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 1:33 pm 
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ngpmike wrote:
If nothing else, the perforated stuff would leave a more interesting burn pattern in case of direct contact with the skin! :shock:
DING-DING-DING!!! We have a winner!!! :rofl:

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 Post subject: Re: Muffler Shield
PostPosted: June 21, 2018, 2:36 pm 
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I wonder if the goal is to insulate from the exhaust heat, provide a touchable surface over the exhaust, or both?

The high pressure area at the front of the fender tends to force air into the pax compartment plus the heat rising at low speed. Insulating from the heat works better with solid versus perf. Solid has more metal to act as a heat sink and blocks what would come through the holes.

Perf should run a little cooler but how solid/perf mounts can make all the difference. A touchable surface would need to mount to the body rather than the exhaust. A silica blanket or wrap on the exhaust with an air gap to an expanded metal guard would work well. A 20x6x1 “rib” running board just over the muffler could look good and work well with no blanket, add minimal drag, still provide good access, less likely to eventually crack, and be touchable. If it hugged the contour of the fender it could also block a lot of heat rise up the fender when driving.

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 Post subject: Re: Muffler Shield
PostPosted: June 22, 2018, 7:06 am 
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My expanded SS heat shield is mounted on the muffler with hose clamps and offset brackets. The only hot surface is the rivets that attach the brackets that the hose clamps slip thru. You can actually rest your hand on the shield while going down the road, as long as you do not end up putting your paw on a rivet. DaveW


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 Post subject: Re: Muffler Shield
PostPosted: June 22, 2018, 8:24 am 
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ngpmike wrote:
If nothing else, the perforated stuff would leave a more interesting burn pattern in case of direct contact with the skin!


I know from experience that the perforated covers on Thrush Outsider sidepipes get plenty hot enough to leave interesting burn patterns, right through your pant leg.

Once they're running that hot, would more hotterer really be a big deal?


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 Post subject: Re: Muffler Shield
PostPosted: June 22, 2018, 9:01 am 
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To shield the cockpit area would require a solid shield, an air gap and maybe some additional weatherproof insulation. I added 1" polystyrene to the inner side of the body, between the frame pieces which helped a lot (except for the heat rising from the muffler and then into the cockpit over the side. Remember that people, possibly yourself, will be < 1 foot away from that hot radiator whether shielded or not!

To protect innocent people from touching a very hot exhaust system after a spirited run would (if using metal) would require perforated shield. My reasoning is thus: the muffler will be hot with or without the shield. Immediately after a run, the exhaust system will radiate that heat and convection will cause that heat to travel upward. If the upper surface is solid, the heat will be trapped and the solid shield will pick up that heat. However, if the shield is perforated, the convection will cause the heat to rise, bringing cooler ambient air op from the bottom, cooling off both the exhaust system and the shield quicker. A side benefit is that less material = less thermal mass = less personal injury (to a point). FYI. aluminum is a horrible material for this application. it has a high thermal mass AND high thermal conductivity. This causes quicker injury to things like human body parts.

And don't forget that the exhaust header and pipe gets hotter than the muffler.

Personally, I am a fan of perforated material, strong enough so that it cannot be easily deformed by accidental contact woth shins or bare feet.

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 Post subject: Re: Muffler Shield
PostPosted: June 24, 2018, 12:06 am 
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Location: Novato, CA
I used 16 gauge perf'd SS from Online Metals, one foot by two foot sheet rolled around a pipe. It's worked perfectly for 50K miles. A couple years ago, an exhaust hanger broke and the pipe started to tear. The exhaust was dragging on the ground. I drove the last 20 miles home holding the exhaust pipe up by the shield with my gloved hand. Barely got warm.
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