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Interesting! I’ll have to read more about that TLTD coating. Thanks! Tracy Sent from Mail for Windows 10 Exactly. Getting heat away on the outside is the idea. The CBC2 is used in the combustion chamber as a thermal barrier coating to reduce heat going into the heads. The TLTD is used on the fins/outside of the heads as a thermal dispersant. I don’t know how it works but it does. It improves the transition of the heat in the heads to the cooling air. It must improve heat conductivity. There is descriptions of the application of both products on the website. Cheers. Nige. From: Rotary motors in aircraft [mailto:flyrotary@lancaironline.net]
Sent: Wednesday, January 25, 2017 1:34 AM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: exhaust wraps and blankets Hi Nigel, Just curious. What was the idea in coating the outside of the heads? The coatings are typically to block heat flow and I’d think we’d like the heat to flow out of the heads on an AeroVee. Tracy Sent from Mail for Windows 10 Yep. I recently did coatings to an Aerovee type engine. Both Combustion chambes and outside of the heads. I used CBC2 and TLTD from http://www.techlinecoatings.com/hi-performance/shop-only.html\ I am in OZ but fortunately it was available locally. The process was straight forward and I did the curing in the BBQ oven outside. I also went ouch when I got a quote to have it done and it was far cheaper to by the stuff and do it myself ( I have a small grit blaster so did that myself as well but that was included in the quote). I have enough of the stuff left over to do about another 10 sets of heads. Cheers. Nige. Ouch. Anyone have any experience with any of the DIY coatings? For that money, you consider building your own curing oven....
Charlie
On 1/23/2017 3:01 PM, Ernest Christley wrote: Got a quote from Jet-Hot. A fairly simple Y shaped muffler system for Corvair would be around $300. I am interested in ceramic coatings also. A question arises in the areas of slip joints or ball joints. Also with pushers (perish the thought) what will the effect of a hotter exhaust blowing on the propeller in a more concentrated fashion vs a cooler blast modified by the radiation of the exhaust system being cooled by moving air leaving the cowling? Lynn, Et All, I want to mention the alternative to heat wraps, ceramic coatings. I have used Jet-Hot on headers for insulation and performance. Early Jet-Hot didn't have a super high temp coating that would stand up to rotary exhaust temperatures. They have had an 1800°F+ material for some time now. They needed to have a coating that would stand up to turbo header temperatures. They have a service where they apply to the inside and outside of the pipes. There is a very minor smoothing effect that even help HP. The insinuative effect is as good or better than most heat wraps, and the pipes look great too. I have used them for pipes on racing motorcycles that have tight fairings. I measured a 30° difference inside my fairing with no other changes using color change tape, but I think is was even better than that in terms of radiated heat. I had a battery located in the fairing mounted low in front of the headers. This no longer was showing bubbling and melting effects, and survived a 4 hour endurance race as a total loss system. I don't work for those guys, and wasn't sponsored by them either. I highly recommend them. On Fri, Jan 20, 2017 at 10:07 AM, Lehanover <flyrotary@lancaironline.net> wrote: The good news is: Heat wrap tape works great. Amazing drop in temps around the engine. The bad news is: Carbon steel headers, even in .140" wall turn to dust in one racing season. Literally you can crush the header pipes with one hand. The outside radius of bent tubes is thinner and will fail sooner.That bright orange header you see in tapes of dyno runs is exactly what your heat taped header looks like. How strong is bright orange steel? Even stainless? Steel under stress fails sooner. Each down pipe should be free to twist and squirm a bit as it heats and cools. Only stainless down tubes and only thick wall stainless at that. If you wrap the whole thing the exiting exhaust gasses will be close the EGT readings on the gage. Will your car muffler hold up to 1600 degrees. If some heat tape falls off along those pipes will the bright orange pipe damage anything important? Then a collector to take the two or three tubes (all exactly the same length) in and then the beginning of the exhaust system. Collector attaches with stiff springs the down pipes. A strap fail safe in case a spring fails. Two strands of safety wire through the spring loosely in case the spring fails (they like to sing along with the engine) you know and a piece of spring will find a place to get stuck that will be the least helpful. The collector is supported loosely by a bracket that moves with the engine. Then a slip joint or flex joint of some kind to account for the engine moving about with power changes. Then the exhaust system, mufflers and so-on may be mounted to the chassis. Non rigid mountings to keep the noise down would be good. The whole system may may be covered with .015" stainless shielding spaced one inch at least off of the tubes. Air blowing between the shielding and the header/exhaust tubing does a good job of reducing temperatures under hood/cowl, and keeps the shielding from radiating higher temps. My problem with the wrap is that it makes inspection somewhere between difficult and impossible. I opted for wrapping the muffler in a .025 stainless shroud that went all the way to the air exit, and ducting airflow through it. Sort of a muffler over the muffler. It'd be heavy, but the shroud could have been lined on the inside with blanket material for more heat isolation. So I'm interested to hear about thoughts on exhaust wraps? I know that some people like them and others don't. Also some header manufactures don't like them. But the fact is that we have one heck of a lot of radiant heat under the cowl. Heat shields help some but I really just want to try to keep most of the heat going down the exhaust pipe. I know ceramic coating on the inside of the pipe is the best solution, but once a pipe is no longer new it becomes more difficult to apply and hope for it to stay. On my first ever engine build I had my rotors ceramic coated as that was supposed to reduce oil heating, but after I had a little detonation incident I found during the rebuild that much of the ceramic had come off due to the shock of detonation. In my mind, I don't feel that ceramic coating the outside of the pipe is any better than wrapping them as the heat is still absorbed by the metal but unable to radiate out. But the biggest argument against ceramic coating is that once it's done, you can't modify your pipe (welding etc.) without having it redone again. A good example of this just happened as I'd already had my exhaust completed some months ago, not expecting that it would change again... But then somebody on this list started saying how great his PLX wideband sensor was, blah, blah, blah, and suddenly I'm out a couple of hundred bucks and having to redo my exhaust because it's recommended that the sensor be located at an 15 degree angle, no less than 36" downstream from a turbo, while my old narrow band sensor was only 14" downstream. So rather than leaving the old sensor in place I decided to cut it off along with another (long ago) incorrectly placed EGT port and weld a patch over it, then install a new O2 bung downstream. Pretty simple to unwrap, weld and re-wrap. So as far as wraps go... lets hear it. Good, bad or ugly. Next is blankets. I have the original mazda metal turbo shroud in place but then I bought a large turbo blanket to fit over that. The exhaust manifold that the turbo bolts to also has a stck Mazda metal sheild but I made one to fit over that as I feel these 2 items probably account for the largest source of under-cowl heat and since the oli cooler is directly below that, I want to eliminate that source of radiant heat transfer. I made this cover using 2 different styles of welding blanket sewed together like a quilt. The ball joint in my exhaust pipe, I decided to also cover with a blanket like this rather than wrapping it, so I made it into a sleeve that slides over the joint. Finally we get down to the muffler which is located inside a housing (more on that in a another post), due to it's location inside a housing I decided to put a quilted blanket sleeve over that one too. Pics of all this and more at this link.
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