Lynn, I don’t
know what we would do without you.
I have several questions.
Where can I get a good accumulator tank?
I was thinking of making one out of a used
fire extinguisher and was also looking at one from Moroso that looks like
a flat canteen. The one from Moroso has an inlet on the bottom and one on
the top side as well as one for the pop off of the radiator cap. Due to
space constraints, I will probably try and make one. I need something about 3”
diameter and maybe 12” or so long. Will I need the inlet on
the top side? If so, where does it plumb to?
I suppose I will still need an overflow
tank from the pop off of the radiator cap?
After talking with Tracy yesterday, I tried to see if the engine
would stabilize temp somewhere below 230* at 2600 rpm. No joy! I
suspect that I will need to increase air flow to get this to happen. I
will try an leaf blower on the cowl today.
My pressure stabilized at 22 lbs (cap in
constant blow off relief) but the temp would not hold. If I had this same
condition with the system you described, what would prevent the air from
blowing off and then water from the accumulator?
It seems to me that no matter what system
you have, the pressure has to stabilize below the pressure rating of the
radiator cap, else you will be losing first air, then water????
Bill B
From: Rotary motors in aircraft
[mailto:flyrotary@lancaironline.net] On
Behalf Of Lehanover@aol.com
Sent: Wednesday, October 03, 2007
10:28 AM
To: Rotary
motors in aircraft
Subject: [FlyRotary] Re: Coolant
Water Pressure
In a message dated 10/3/2007 9:08:53 A.M.
Eastern Daylight Time, bbradburry@bellsouth.net writes:
I think that I would see air under the radiator cap if I had a
compression gas leak? I never see any air.
To check a piston engine for head gasket leaks, you would put the
cylinder at TDC and pressurize the cylinder to about 150 lbs with compressed
air and check the radiator for air bubbles…How do you check a rotary?
I will check the pressure sender against a mechanical gage.
There is obviously a heating problem, but I think the pressure is
higher than it should be until just ready to boil. I shut the engine off
at 210*, and at 22+ lbs, the boiling point should be well above 250*??
Thanks for the suggestions of where to look, guys…
Bill B
It is extremely difficult to remove all
of the air from a rotary engines cooling system. It is also extremely
important. If air is under the pressure cap in a static situation, it will
remix with other coolant when the engine is at speed. The coolant moves very
quickly through the system. The coolant volume appears to increase slightly
because much of the air is reintroduced into the water. This coolant then
becomes a poor conductor of heat. You need the anti foaming agent in
Antifreeze. Just a bit, perhaps 10%. The system with the relief cap right on
the radiator or filler point, starts to offload coolant as soon as the engine
is started. It is in hydraulic lock, and has a small volume. The actual boiling
point calculated for this coolant makes no difference at all. The cap opens a
bit when the trip pressure is attained, the pressure drops to 22 PSI or
whatever for your cap, and a bit more heating trips the cap again. It is
exactly the same as most cars.
So, at first in each heat cycle, there
may be no correlation between coolant temperature, and the actual amount of
coolant dumped by the cap. This is only true closer to a constant operating
temperature. And then pressure may be alarmingly unstable with power changes.
The accumulator system makes pressure rock solid.
Make the pressure cap into a filler cap,
sealing only the top lip of the radiator or filling port. Connect only a
bleed hose and run it to the bottom of a recovery bottle, and put the
pressure relief cap on that bottle. Keep the bottle about 1/3 full. Note after
several heat cycles, the amount of water you need to add to keep that bottle
1/3 full is reduced each time. Once all of the air is out of the cooling
system, no more coolant need be added to the bottle.
Heating and cooling of the system, makes
sweeping changes in coolant volume. The air cushion in the bottle acts as an
accumulator (used in thousands of aircraft) to maintain a constant pressure and
coolant supply.
Race cars use a Rolairtrol or spin bottle
in the hose from the top of the engine to the radiator. Water enters the bottle
at about half height on a tangent and adds a spinning motion. Water leaves
through a center hole at the bottom.
Trapped air pops to the top of the bottle
and that is plumbed to the bottom of the accumulator as above.
You used to get the plans for this thing
when you buy a Cosworth race engine. Does Cosworth know something you
don't?
Anyway, after about three heat cycles
(operating temperature and back to room temperature) the coolant system will be
solid coolant with all of the air removed. It will not be hydraulically locked
against the cap.
It will have the relief cap pressure, and
will hold that for as long as the engine is hot.
I have a Shrader valve installed in my
accumulator tank, and before I start the engine I charge that bottle with
compressed air until the cap relieves at 22 PSI. Now I know it has pressure,
and I know it has 22 PSI.
This was the stock system on all Mazda
cars in the 70s. I didn't invent it.
It is unlikely that you have leaking
compression seals, unless there is coolant blowing out of your makeup tank, or
coolant is running out of your exhaust system after shutdown.
My recovery bottle is mounted where the
passenger foot well would have been. Even with the bottom of the engine. So
long as the hose ID is less than 1/4" and the hose enters the bottle on
the bottom of the coolant supply, it matters not at all where that bottle is
located. There is a money back guarantee with this system.