Note

A mild steel exhaust will be heavier than a similiar stainless steel system because the automotive pipes have a heavier (0.050") wall thickness. In contrast , stainless steel pipes have a thinner (0.035") wall thickness.

Consider using the exhaust to offset some of the torque-pitch coupling and/or to assist with yaw.

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Defuse the exhaust when it exits the exhaust system so that the heat will not damage the propeller ??

If the exhaust system is short and compact, consider bracing it totally from the engine.

Consider exiting the exhaust above the engine cooling outlet. This should have the advantage of tending to slightly compensate for the difference between the upper and lower drag. Another advantage should be a reduction in the noise being transmitted to the ground. A disadvantage might be that of precipitation entering the exhaust system.

Another wild idea: What about exiting the exhaust through the upper pulley.

Another idea: Run a Swiss muffler from the exhaust pipes, up in front of the cylinders and out the lower part of the start of the booms, This will reduce the noise being transmitted to the ground, put the exhaust gas in an area of low pressure and allow the hot gas to defuse a bit before it contacts the prop.

Consider exiting the exhaust along with the engine cooling air in the low-pressure area (during cruise) behind the rotor hubs and final gearbox.

> Has anybody used ceramic cloth on his exhaust > and did it drop the temps under the cowling ??

I've successfully used insulation wraps on my stainless X-over for over a year now. Aircraft is a Lancair 235 and cowling is really (I mean realllly) tight in there. My engine is a Lyc O-235-C. Insulating the exhausts has several advantages beyond the "not burning the paint of the cowling" aspects. Firstly, it will increase power by improving the scavenging effects of a x-over. This is related to the fact that the pressure drop is done at a constant temperature (remember pv= nrT ?) Back-pressure reduction is the desired effect of a good, tuned crossover exhaust system. Improving this has a direct relationship to the engine's power output. Secondly, cooling an air-cooled engine is proportionate to the deferential pressure between the two chambers, the upper cowl cavity and the lower cowl. Adding a heat source on the bottom chamber (via hot exhaust pipes) effectively lowers the pressure differential and as a consequence the efficiency of the whole cooling system. This way, cooling drag can be reduced significantly by improved flow and reduced cool air requirements (e.g. smaller intakes and outtakes). As an addition, radiating heat coming from the exhausts is heating-up the intake pipes, causing another power degradation mechanism. Insulating the exhausts also results in cooler intake gases (therefore higher volume at a given mp). An alternative would be to also insulate the intake ports. There are better methods than the wrappers, though. Ceramic coatings (external) are better with respect to corrosion resistance, inspection for cracks as well as for radiant heat reflection properties. I am still experimenting with these and I found that there are more than marginal impacts found by insulating the exhaust pipes in my own project. Yes, the cowling is cooler and yes, the engine produces more power. With such a small powerplant like mine (relatively speaking), every bit counts... Might not work equally well for all, though Hope this helps Francois Marquis Lancair C-GLUE ---------- In article <3823e08f.2478380@news.m.iinet.net.au>, wotan@opera.iinet.net.au (Uwe Seeler) wrote:

See 'Tony Bingelis on Engines', Exhaust Systems, section 9.

See 'Firewall Forward', Exhausts & Mufflers, section 5.

For products including )-320 pusher systems, see; Spruce catalog page 235