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> From: Dale Rogers <rogersda@cox.net>
> Date: 2004/08/04 Wed PM 02:04:37 GMT
> To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> Subject: [FlyRotary] Re: May not work above 8000 MSL was [FlyRotary]
>
> Ed,
>
> Might this be one of the advantages of having a separate
> reservoir (with 2-cyle oil)? Except when pulling negative
> G's, a reservoir mounted well above the pump would give it
> a little head pressure that would be independant of the
> atmospheric pressure.
>
> Just a thought,
> Dale R.
> COZY MkIV #1254
>
> > From: "Ed Anderson" <eanderson@carolina.rr.com>
> > Date: 2004/08/04 Wed AM 07:16:02 EDT
> > To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
> > Subject: [FlyRotary] Re: May not work above 8000 MSL was [FlyRotary]
> > Re: Oil injection, and more
> >
> > You may be correct, Al. Without testing it would be hard to say.
> >
> > No question my theory could be wrong - but as you say something must have made Atkins come to the conclusion that the metering pump does not work above 8000. If his claim is valid - then there must be some cause related to altitude. The only part of the fuel metering system that would be affected by altitude that I can see is the oil feed from the shaft boss to the pump.
> >
> > We know that as pressure changes across an aperture will cause the flow rate to change - whether (as you point out) the difference due to altitude is significant enough to account for any lessening of oil flow is the question. Whether or not a few pi would ensure adequately flow sufficient CCs of oil will depend on the size of the orifice through which the oil flows. I agree if the aperture is sufficiently large then a few PSI change in pressure will make little (if any) difference in flow. However, if the orifice is small and the flow barely adequate to meet the needs say at 14.7 psi then 11 psi could lessen the flow. Not claiming that flow would cease, but it may well be diminished.
> >
> > My 0.02
> >
> > Ed
> >
> >
> > Ed Anderson
> > RV-6A N494BW Rotary Powered
> > Matthews, NC
> > ----- Original Message -----
> > From: Al Gietzen
> > To: Rotary motors in aircraft
> > Sent: Wednesday, August 04, 2004 1:07 AM
> > Subject: [FlyRotary] Re: May not work above 8000 MSL was [FlyRotary] Re: Oil injection, and more
> >
> >
> > Subject: [FlyRotary] May not work above 8000 MSL was [FlyRotary] Re: Oil injection, and more
> >
> >
> >
> > Dave may be correct, Perry.
> >
> >
> >
> > Here is what I think could occur. First, The oil meter pump itself is a positive displacement pump.
> >
> >
> >
> > Therefore, from the standpoint of the pump it will always disperse any oil fed to it into the injectors and combustion chamber under some amount of pressure. However, the shaft opening that drives the pump also provides for the oil flow from inside the Engine Front mount into the metering pump. There is a hole in the boss of the metering pump shaft (on the inside of the front housing) that is open to the atmosphere.
> >
> >
> >
> > At sea level of course this hole in the boss results in 14.7 psi of pressure on the oil in the meter shaft. So as the positive displacement pump opens a chamber - the oil flows into the chamber with the help of this 14.7 (or what ever the differential between the pressure in the pump chamber and the atmosphere- it will something less than 14.7 but probably greater than 12?) and gets "squirted" toward the injectors underpressure.
> >
> >
> >
> > Ed;
> >
> >
> >
> > I hear what you're sayin', but I really don't think so. How much pressure does it take to make hot oil flow through a short length of tube (or a port in the pump) at a VERY low flow rate? Very little. We're talking a few cc/min; and I'd guess even a couple of psi, would do the job nicely. And at 8000 ft we still have; what, about 11 psi.
> >
> >
> >
> > As we go to higher altitudes it is probably more likely that we'd get vapor lock upstream from the fuel pump before we stop getting oil from the metering pump.
> >
> >
> >
> > This is just off the top of my head, so, you know, maybe there is something I overlooked. The question is: what phenomenon was Atkins observing? He obviously had some reason for his statement.
> >
> >
> >
> > Al
What about the vacuum of the rotors drawing the oil into the chambers? That happens at any altitude.
Marc Wiese
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