> Gordon
>
> Yep, Parker is another good company. That should work.
>
> Doug
>
> What do you guys have against this idea? What is wrong
> with it?
>
> Paul Lamar
Hi Paul,
there is nothing wrong with it per se : but using your reasoning...
What do you have against the Parker valve? What feature is missing that
we need? What is wrong with it?
For: It is well made, it has the known flow characteristics ,easy
to mount, easy to operate, vernier adjustment, and readily
available.
Using the Parker valve makes the Slide throttle a lot simpler, in that
the leaning feature is remote from the moving slide.
And if you must mess with the needle on your lathe/ mill, then you can
simply dismantle the valve for easy access.
Against: Its mode of operation is not like that on a "Cessna spam can"
???
Dave McC
Where do I begin?
The long needle valve is also remote from the moving slide.
However you want to keep it as close as possible so
vapor is not made in the fuel line from the valve
to the slide throttle by engine heat.
Anything that you have to twist remotely means
you need a torsionally stiff shaft. That rules out the stock
off the shelf leaning cable with vernier as it's shaft is only about
.1 inches in diameter. It must be that small so the valve
can be out of axial and lateral alignment with the twisting
knob three feet away on the instrument panel. If there is any
wind up in the shaft it makes fine adjustment difficult. It also
must accommodate movement by the engine in it rubber mounts. Sure
a 1/2 inch aluminum tube could be used if you mounted it on the
firewall. Now you have at least two couplings to deal with
and a new knob. Mounting the whole valve on the instrument
panel means you have a longer fuel line to the slide throttle
with more opportunity for fuel vapor accumulation.
The second major problem is it takes too much time to open
fully or close fully. That is a major feature on the long needle
valve. You need to open the valve completely to prime
the engine for starting and close it quickly for shutting off
the engine.
Third, the long needle valves position is obvious from
a glance at the knob sticking out of the instrument panel.
No need to read a small rotating scale.
Forth, pilots don't need to be retrained. Anybody flying a
Cessna "spam can" (I represent that crack :)) will know exactly
how and why it is used.
Paul Lamar ...No rotor no motor.
Paul,
I'll start with the disadvantages of your needle valve:
1. Its action is in the wrong direction, so if you want to pull out
for leaning you have to mount a lever that will reverse the needle
travel. You were just railing against levers as prone to slop...
2. Those O-rings will leak if you try to run any more than a few
pounds of pressure, so the valve is not usable on the constant flow
injection system. It would probably work ok with the slide throttle
carb.
Now the stuff you mentioned against the Parker valve:
1. Yes, it is a different "interface" than the standard pull out for
leaning mixture control. Okay, but what is the alternative? EFI with
no mixture control at all? Or a little knob to control an
after market EFI system? Compared to this, I'll take the manual twist
knob.
2. There can be no windup and hence no slop with an aluminum tube
extension like Dave suggested. All you add is an aluminum tube. You
use the same knob that comes with the valve.
Regards,
Gordon.
I am only concerned with the low pressure 2 psi fuel system.
You high pressure mechanical system guys are on your own :).
Too expensive for me. Requires a high pressure pump.
Colin Smith came up with a simple variation that changes the direction.
I like his idea better than mine as it has the potential for
a more positive shut off feature. I am working on a 3D.
Paul Lamar ...No rotor no motor.
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