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Or, you can install an accumulator such as used in hydraulic systems. The early Mazdas did this. A make up bottle on the firewall had the pressure cap installed on it that had usually been installed on the fill port on the radiator. Just a cap on the radiator to seal it but no pressure control system. The make up bottle (accumulator)
is filled to 3/4 of its volume with coolant. As the engine heats up, bubbles in the coolant find the top of the radiator and then up the hose to the bottom of the accumulator where they pop up through the coolant to the top space into the air. When the volume (pressure) of the coolant is reduced as in a lower throttle setting or closed throttle, only coolant can return to the system. After several heating cycles most of the air entrained in the coolant will have been removed and you must add more coolant to the bottle. Mazda invented this, not me. Works great. The bottle need not be mounted higher than the water pump at all. The racer had the bottle on the passenger floor. Worked great.
The extra coolant in the bottle could mean a bit more time under power in the event of a leak. There are a number of shapes available in circle track catalogs. You can also rig a pressure gage on the bottle and a Schrader valve to pre pressurize the system before start up. The pressure cap will bleed off only air as the temps come up to normal and then stop bleeding at its rated pressure. In olden times the center iron had a port to remove air from the system as it was being filled. The rotary has a problem with holding much air in nooks and crannies in the coolant channels in the engine. Only a few blasts to operating speed will produce a high enough flow rate to move this air along so it can be removed. Some assembly may be required. The batteries are not included. LEH
In a message dated 8/20/2020 5:44:27 PM Eastern Standard Time, flyrotary@lancaironline.net writes:
Charlie,
Yeah, dead right, Putting the water pump right at the bottom of the engine for that reason.
Neil.
From: Rotary motors in aircraft <flyrotary@lancaironline.net>
Sent: Thursday, August 20, 2020 11:27 PM
To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: [FlyRotary] Re: Water direction
If you're using an electric pump, the one change that should be simple to do and would improve the system design is to move the pump location physically lower. I'm working from a very old memory here, but IIRC, the one real downside to the rotary's pump location is that it's at the top of the engine. That means that if for some reason you start losing coolant, the pump quickly loses its ability to move water. Again, if memory is correct, with the pump at the 'bottom' of the system, you can keep coolant flowing for a bit longer. It won't cure anything, but if you have a pressure leak it might keep coolant moving long enough to find a landing site.
I suppose it could have a slight benefit in the sense that it'll always have at least a little bit of pressure on the inlet, which could slightly reduce the risk of cavitation.
If my memory is defective, hopefully someone else will correct me.
The water flow direction is important, the standard takes heat from the hot side and tries to keep the coild side near the same temperature to avoid the engine "becoming a banana". The impeller type pumps used in engines are primarily 'pushers'
Hi Neil.
Two thoughts I imagine that might create issues:
1. Energy transfer down due to delta T being lower, increasing the danger of nucleate boiling near the plugs
2. Creating a higher differential between the hot and cold sides of the engine producing increased expansion differences across the engine.
Question: Do impeller pumps that we use suck and push equally well? My guess is that they don’t.
If this doesn’t matter would it help with the physical layout to suck the water through rather than push it through?
Cheers
Steve Izett
> On 20 Aug 2020, at 3:30 pm, 12348ung@gmail.com <flyrotary@lancaironline.net> wrote:
>
> Gents,
> Looking today how to hook up my electric water pump. The simplest is to send the water reverse to a standard pump. I do understand the hot side and the colder side but with the water being changes every 1 - 2 seconds, does this really matter?
> Thoughts?
> Neil.
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