X-Mozilla-Keys:                                                                                 
Archie wrote:

Yes but Archie racing engines have a life expectancy of three hours
and the heads are not six inches thick where the bolts go through.
Well maybe hemi heads are. Hemi's have a life expectancy of
five seconds. Heck they don't even use coolant.

Paul, I must disagree with your assessment of LIFE EXPECTANCY.
Occasionally a 5-6000 hp engine may melt a piston, blow a rod, or
fail somehow, but in 16 years of personal fuel racing, and building
engines for over 30, this is far less frequent than you may believe.
If we do some interpolation, and reduce the power to, say 2000 hp,
the odds are even better. These engines do not automatically self
destruct in five seconds.

I stand corrected Archie. I always thought those nitro burning drag 
engines were a "Barely controlled explosion in a barely reusable 
container". :-) 

The same applies to Nascar types, (yes, they are checked after
every race, this is only good PM). Again, they do not automatically
go to that great salvage yard in the sky after a few hours,

Even when overheated, cylinder head warpage is not near as bad
as in a conventional automobile.

The fact that the rotary housings are sandwiched between iron castings
should offer a degree of stability. Not having overheated one. and then
check it out, I have no baseline for reference. How critical is this?
Allowing the housings to expand may not be the solution, perhaps
arresting movement with a larger through bolt is.
?? Archie

What happens Archie is the aluminum gets so hot its compressive
yield stress is reduced and it takes a permanent set when it expands 
that, of course, is smaller than when it was brand new. This gap between
rotor housing and end or center housing allows the water O-rings
to leak coolant into the combustion chamber or hot gases into 
the water jacket. Kind of like a head gasket failure.

A larger through bolt would make it worse. There is another factor
and that is the rate of temp change. With a sudden loss of coolant
the aluminum can expand faster than the bolt. This can also be caused
by failure to warm the engine up before full power is applied.

The belleville spring idea is like a circuit breaker that automatically
resets. The spring rate is low enough not to yield the hot aluminum 
when it expands but not too low to allow the housings to separate and 
leak combustion gases under max combustion pressures.

The ultimate solution is to re-design the engine with housing 
flanges and shorter bolts similar to the way a jet engine is made.
That of course is out of the question for our cost structure.

Paul Lamar
 
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