Not exactly. The radiator is surly a big restriction to flow. In a case where the water pump can force a bit too much water through the radiator per second, then the problem arises. The pump establishes a differential pressure in the system so that flow will occur. So, the pressure side of the pump produces higher pressure, and the suction side produces a lower pressure. So long as the low pressure side combined with a high enough pressure stays below the boiling point of water (or coolant) there is no problem. In high school we pulled a vacuum on a jug half full of water. Plugged up the inlet of the jug. Now put your hand on the side of the jug......the water boils where ever you touch the jug.  But how is this possible says the teacher??? Water boils at 100C or 212F.......The answer is that both pressure and temperature determine the boiling point of water.

So, that 100C or 212F is only good at sea level............or 14.7 PSI  And nowhere else.......So how much heat must I add, or how much pressure must I remove to get boiling on the inlet side of my pump? 

Why, not much at all.

If you are already at 190 degrees some people think 200 degrees is not outlandish.....Just put your hand on the jug......and Presto....boiling.  It is difficult to come up with a new way to destroy a rotary engine.  There are some who seem to be working on just that. Years ago we raced a RX-2 with a junk engine in it. The driver was doing well following a Corvette. A misplace end wrench fell out of the Corvette and went through out radiator.

The coolant blew out in a lap. The driver (ODed on brain chemicals) did not notice the pegged temp gage and later the no temp on the same gage. Finished the race (about 20 miles at full throttle). Came into the pits and turned off the engine...........no good. Engine is white hot. Running on glow plugs (what was left of the spark plug tips) I had him hold the brakes and declutch in 4th gear. Engine stopped....and screeched and whistled

and moaned for about 15 minutes............ The pulleys the crank and plug wires were OK....nothing else.

So, a legally dead rotary may be better than a badly hurt Lycoming. when the power goes away, airspeed, hit nearest. leave on full throttle, announce your intentions, fly the plane. You got the engine from a junk yard.

You are renting the plane from an insurance company.Only you cannot be replaced with a phone call.......................

So. water make up bottle as in RX-2 RX-3 RX-4. Stant (lever) pressure cap 22 to 26 pounds. 10% glycol

in distilled water. 1/2 teaspoon of Dawn dishwashing detergent. Change coolant often and insides will be clean and less difficult to cool. Oil coolers should be way too big with too much air supply.

The engines are about 28% efficient.  So the rest of all of those BTUs must be removed by your cooling systems. (and the exhaust system).

There may be no truth at all in the above and below information.  My guess is as good as yours.

LEH

In a message dated 6/11/2020 7:30:03 AM Eastern Standard Time, flyrotary@lancaironline.net writes:

Thanks for that. Great information!

So it seems that the radiator flow restriction itself is not adequate, in some circumstances, to avoid cavitation.

I remember with my Midwest they dictated a coolant reservoir just prior and superior to the pump. Was that their way to prevent cavitation?

Now comes, at least to me, the age old question as to the advisably of using an electric coolant pump. If used, and/or  successful, do these need a restricter or is one built into the unit or they, as was expressed by the late Paul, totally worthless?

Rich

Sent from my iPhone

On Jun 11, 2020, at 1:30 AM, lehanover lehanover@aol.com <flyrotary@lancaironline.net> wrote:

Cavitation is caused by a spot of low pressure. So a tiny imperfection in the face of the impeller would be the start of each event. It could be a sand blow hole. It could be an imperfect bit of machining......Note that impellers are sand cast crap. Not machined on every surface at all. So many variations in shape and surface finish......or" as cast"  as you may have seen on many drawings.  This is because almost any shape at all would work well as an impeller in a pressurized system. It looks like hell because it doesn't matter what it looks like. Works just fine in a car...........Pumps for more critical installations have impellers that are 100% machined and polished. Even a stamped steel impeller is a big step up in performance and reliability due to a more uniform shape. More modern pumps have smaller yet better performing impellers due to the interest in fuel mileage. More fluid flow for lower power input.

I ran my engines with a 5/8" hole on the outlet to the radiator. At first I made a restricter mounted where the 

the normal thermostat would have been. Years later I built it into the Norice or, the aluminum water outlet

to the radiator. I never had a cooling problem in 30 years of racing. But I also know that more than 1/3 of the total cooling load is in the oil. I cooled the oil and the water stayed below 180 degrees. I used three 44 row Setrab oil coolers. Your results may vary...............LEH

In a message dated 6/10/2020 12:01:53 PM Eastern Standard Time, flyrotary@lancaironline.net writes:

OK, but then why just one blade?

Finn

On 6/10/2020 11:34 AM, lehanover lehanover@aol.com wrote:

All of the rotary stuff left here with the last race car,  so there is nothing to look at. So...this will be a guess.

12-A before 74.

A look at the front iron could tell the tale. Mazda kept removing bolts from anything they could, so, more bolt holes generally  means older piece.

Cavitation damage can be caused by letting the pump output outrun the suction side supply. So just limiting the output a bit with a restricter eliminates this kind of damage.  If you have seen a water jet cut through a 1/2" steel plate you might think this could happen on one long test flight...................

LEH     

In a message dated 6/9/2020 1:30:41 PM Eastern Standard Time, flyrotary@lancaironline.net writes:

Ryan, is it possible your water pump is off an old 12A?

Lynn Hanover is on this list and would be able to answer anything about 12A's ... maybe reach out to him directly in the subject line??

Jeff

-----Original Message-----

From: Jeff Whaley

Sent: June-09-20 8:02 AM

To: Rotary motors in aircraft

Subject: RE: [FlyRotary] Water Pump

Hello Ryan, this is a photo of my water pump from a 1988 13B ...  Jeff

All,

 

Can anyone point me towards the correct water pump? The one in the top of the photo is the correct one. The one on the bottom is obviously incorrect. It's the second one we've ordered.

The first one that I ordered looked identical to my original one.  However, when it arrived it was similar, but about 1/3 smaller than mine. When I ordered this second one we all (Carquest employees) poured over the pictures to make sure it was correct. When it arrived it had one less bolt hole than the one in their pictures.

I have a Powersport 13B. Any ideas what pump they ran and where a guy can order one

Thanks,

Ryan

--

Homepage:  http://www.flyrotary.com/

Archive and UnSub:  http://mail.lancaironline.net:81/lists/flyrotary/List.html