Lynn,

        This is a four Rotor made from two 13B engines by "Granny's Speed Shop" http://www.grannysspeedshop.com/  in

Concrete, WA..............Interesting but to me the most interesting thing is the modified cooling system.........Their website

has a lot of info on how the two engines were coupled together but they have yet to provide what internal modifications were

made to direct coolent flow in the proper directions after it is connected to the center housing.........This system would seem

to address the fact that the rear rotor runs somewhat hotter than the front rotor in the stock cooling system.........

 

       I am interested in your opinion as to if the benefit would be worth the trouble to implement such a cooling system ?.....

I have heard that the rear rotor tends to fail more often than the front perhaps because it runs hotter..........Has anyone to

your knowledge ever documented how much hotter the rear rotor runs as opposed to the front rotor ?.............

 

Kelly Troyer

 

The cooling system change would require that the web between water in and water out of the front iron be removed, to allow water to flow around the front iron and be removed from the center iron on the exhaust side. You would have to do that for the rear engine where the adaptor plate blocks the water pump land area.

 

Why he did it in the front engine escapes me. Typical failures in high output NA engines is rotor bearing failures in the front rotor due to lower oil pressure than the rear rotor bearing. The front main and rotor bearing is fed from the dowel gallery  that ends with a number of drilled 90 degree turns. The rear main and rotor bearings get the straight shot from the filter adaptor land. So an additional oil line is installed to take oil from a plate mounted below the filter adaptor to the lateral drilling into the main bearing gallery in the front iron. This is usually a dash 10 line, and the run through the dowel gallery is left intact to more than double the cross section of the supply.

 

  In boosted engines it is the rear rotor bearing failing from detonation from higher heat in the rear rotor housing coolant and rear iron. In high boost street racers and dyno racers, you see the top dowels shearing off and or, the dowel gallery hole breaking open and splitting the rear iron all the way down to the stationary gear. This is from the whole engine twisting in opposition to the torque being generated. The engine is twisting in the opposite direction to the crank rotation. To cure this, you add dowels along the plugs and around the exhaust area, or to every case bolt hole. Or a combination of dowels and oversized case bolts in reamed holes. Also mounting the engine by its bell housing face rather than the front cover as in the 12A or the center irons.  

 

Detonation is charge temperature dependant, so coolant and oil temperatures must be under control.

 

Cosworth puts the water into Ford style 4 cylinder blocks through the core support plugs and takes it out through the head. Smokey Yanick  Did the same thing in Chevy V-8s. Water into the core support plugs and out through the heads that were lined with water glass so they could no be overcooled. Smokey liked high cylinder head temps. He also found a way to prevent detonation at very high charge temperatures. Nobody has uncovered his secrete yet. But these systems are used to control the round shape of the cylinders with the coolest water going there first, then cooling the heads last. See Smokey's hot vapor cycle engines. GM could have had his secrete for 30 years now, but thought they could figure it out, so refused to buy from him the greatest improvement in the IC engine since it was invented. 

 

NA rotaries used in aircraft are unlikely to fail for any reason based on design. The dismal cooling systems installed and the thinking that 200 water and more than 220 oil temperatures are OK is just not the case.

The number on the temp gage, is a vague average of the engines temperature. But most of that came from the aluminum around the leading plug and the lower area around the exhaust cycle. Some of the cooling water picks up nearly zero temperature, and some of it picks up too much and boils for a short time.

 

So the gage is showing you a mixture of water or coolant that has been way too hot, and some that was heated very little by the engine. So, the gage did not show you the highest coolant temps, and some of the coolant was heated by adjacent coolant and did nothing to (directly) cool the engine. I would not slow the water pump speed. The extra velocity helps make turbulence and scrubs the heated metals better than slow moving coolant. Note the diagonal dents in the flat tubes of a radiator. Also to create turbulence and scrub the chilled boundary layer off of  the tube surface and allow hotter coolant to contact it. A dash of dish soap or Redline WaterWetter keeps the oil scum and rust from insulating the engines metals from coolant.

 

If I were building a drag racing engine I would build part of his system but put the cold water into the rotor housing between the spark plugs where the highest heat is found. Or just below the leading plug.

 

But none of this is required for aircraft use.

 

Lynn E. Hanover