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Perry Pumps and regulators

Old 01-22-2010, 09:14 AM
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Default RE: Perry Pumps and regulators

Did I state otherwise?
No, but I could see where others would infer that you had to use the Perry Pump carb with the VP 20.
Old 01-22-2010, 10:02 AM
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Default RE: Perry Pumps and regulators

Gents,

I cannot find any outlet pressure of the VP20 (preferred for four stroke) , but they seems to be compatible with the VP30 (two stroke),

In the specs of the VP30 I read: It delivers an ideal .25 PSI to any model carburetor from a .15 to a 3.0 cu.in. engine.
The pressure remains constant throughout the entire speed range, making the carburetor adjustment easy and simple.


This means, it is like the fuel level is 9 inch! (24 cm!) above the outlet of the pump, independent of power level. The characteristic of the carburetor has to handle this!
Cees
Old 01-22-2010, 10:16 AM
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Default RE: Perry Pumps and regulators

The VP 20 pressure is varible, but I believe they claim the factory setting is about .25 PSI. They can be adjusted much higher. If you are using high nitro fuel the head will be less than 9" of fuel at .25 PSI. Nitro is denser than water. 9" is about the same as muffler pressure.
Old 01-22-2010, 10:36 AM
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Default RE: Perry Pumps and regulators

ORIGINAL: Sport_Pilot

The VP 20 pressure is varible, but I believe they claim the factory setting is about .25 PSI. They can be adjusted much higher. If you are using high nitro fuel the head will be less than 9'' of fuel at .25 PSI. Nitro is denser than water. 9'' is about the same as muffler pressure.
Sport Pilot,

What you write with nitro.
The head will be somewhere between 7.5 and 9 inches (20 and 24 cm) with 50 - 0 % nitro in factory setting ideal .25 PSI but is independent of the power level, even when the engine is in idle.
Exhaust pressure depends on the power level and is never that high in midrange and for sure not in idle, that's the difference for the standard carburetor I think.

Cees
Old 01-24-2010, 11:42 PM
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Default RE: Perry Pumps and regulators

What you write with nitro.
The head will be somewhere between 7.5 and 9 inches (20 and 24 cm) with 50 - 0 % nitro in factory setting ideal .25 PSI but is independent of the power level, even when the engine is in idle.
Exhaust pressure depends on the power level and is never that high in midrange and for sure not in idle, that's the difference for the standard carburetor I think.
The pressure may drop off on the pump a bit. The regulator is not very precise. But not as much as muffler pressure, the carb suction picks up at idle to make up for the lack of muffler pressure. That is why check valves on the muffler pressure result in the engine quitting after it runs at idle for a minute or two. It is also why the low speed needle is especially sensitive and if not precise you may have to use the bypass plumbing.
Old 01-25-2010, 10:59 AM
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Default RE: Perry Pumps and regulators

Sport Pilot,

The Cline and Iron Bay regulators we call “proportional controllers†and because of that, depending of the gain, inlet pressure and flow there is a (calculated, predictable) fluctuation in the measured outlet pressure (error).
Normally there are no problems with this principle of fuel pressure control also not in idle.

Cees
Old 01-25-2010, 11:09 AM
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Default RE: Perry Pumps and regulators

The Cline and Iron Bay regulators are non adjustable demand regulators, they deliver pressure at or just below atmospheric pressure, so there is no issue of the idle circuit being too sensitive. The Perry Pump has an adjustable pressure regulator. It is also proportional but probably has a wider throttling range (predictable error).
Old 01-25-2010, 01:01 PM
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Default RE: Perry Pumps and regulators


ORIGINAL: Sport_Pilot

The Cline and Iron Bay regulators are non adjustable demand regulators, they deliver pressure at or just below atmospheric pressure, so there is no issue of the idle circuit being too sensitive. The Perry Pump has an adjustable pressure regulator. It is also porportional but probably has a wider throttling range (predictable error).
Sport Pilot

I understand that you are not familiar with process control systems.

Cees
Old 01-25-2010, 02:08 PM
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Default RE: Perry Pumps and regulators

I understand that you are not familiar with process control systems.
Or you don't understand proportional control systems. A regulator and controller are not the same by the way. A regulator does not take an outside input for one.
Old 01-25-2010, 05:27 PM
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Default RE: Perry Pumps and regulators

ORIGINAL: Sport_Pilot

I understand that you are not familiar with process control systems.
Or you don't understand proportional control systems. A regulator and controller are not the same by the way. A regulator does not take an outside input for one.
Sport Pilot,

In control systems, or a part of it, the most important fact is range ability. Range ability, the limits of operating within the accuracy we want.
The range ability of all the parts of the system does gives the useable range of the system. (Your throttle range?)
For example the low idle flow through the control valve of the regulator for a four stroke engine.
If this flow is not within the wanted accuracy controllable, we have to design a better control valve in the controller or even a new controller.

If a proportional control loop isn’t accurate enough there are other possibilities.
A more complicated controller (P&ID), two controllers, master slave controller, pump controller combination (Walbro?) etc

Of course you also can start with a pump, pump controller combination, pump and a more complicated controller (P&ID), pump and two controllers etc.
When you only use a pump, the fuel air ratio (dosing?) does has its limitation of accuracy in low and midrange, but also the limitation of max RPM. So I prefer a controller.

For the designer there is one important limit!
An engine might never quit!! Also not after 2 minutes idle as you write in post 30, that’s a bad (de)sign for an engineer, so back to the drawing board when there isn’t a fault in the system.

Cees
Old 01-25-2010, 11:59 PM
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Default RE: Perry Pumps and regulators

Here we go again......
Old 01-26-2010, 01:39 AM
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Default RE: Perry Pumps and regulators

The range ability of all the parts of the system does gives the useable range of the system. (Your throttle range?)
The term is rangability. That is a ratio of maximum controlled flow over the minimum. It can be use to compute throttling range. Throttling range is the difference of the control point at wide open to closed valve. In this case the control point is a pressure and if the setpoint is .25 PSI and the regulator valve is wide open at .3 PSI and closed (or at its minimum) at .2 PSI then the throttling range is .1 PSI . Both are unknown. But I believe that both the rangablilty and throttling range of a Cline or Iron Bay is smaller than a Perry Pump and of course at a lower pressure.

Also not after 2 minutes idle as you write in post 30, that’s a bad (de)sign for an engineer, so back to the drawing board when there isn’t a fault in the system.
That is what happens when someone puts a check valve in the muffler pressure line to the tank. The tank keeps its pressure up till the engine uses some fuel. It may take longer than two minutes. Those who swear by this probably never left the engine running at idle long enough to find out, so it may work well for them. If it takes ten minutes then it would be long enough for almost everybody and may be a good system for many.
Old 01-26-2010, 03:43 AM
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Default RE: Perry Pumps and regulators


ORIGINAL: Sport_Pilot

Did I state otherwise?
No, but I could see where others would infer that you had to use the Perry Pump carb with the VP 20.


Well, thanks for straightening that out for all. That isn't what I intended to say.


Ed Cregger
Old 01-26-2010, 05:07 AM
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Default RE: Perry Pumps and regulators

Sport Pilot,

Rangability wasn’t accepted by the spelling checker, all other arguing is by using different terms for all we know I see.

Pump
The throttle range of you, we call the range of flow, demand by the glow engine within your pump has to work properly and for that the pump has its limitation in high RPM value’s. (for ducted fan for example). The pump has an adjustable outlet pressure and a limited flow range.
Disadvantage is the difference in outlet pressure, your 0,1 psi. We call that the error (unwanted!), depending of load. When you cannot accept this error you have to choice another pomp (VP20, VP30) or brand.

Controller
The pressure controller does not have a throttle range, because there simple is nothing to throttle only reduce.
The controller has a fixed pressure setpoint , pre adjust by the designer and builder and you normally cannot change that.
We engineers can difine and change this setpoint by changing internal parts.
You can measure a delta outlet pressure between minimum and maximum flow demand by the engine (load?). This we call a “errorâ€, the error of the proportional pressure control loop. This error (in Dutch “proportionele foutâ€) is mainly depending of the gain of the controller.
The error, usable flow range, minimum needed inlet pressure etc of the controllersystem is depending of the quality and design of the controller and other parts of the system.

Cees
Old 01-26-2010, 07:30 AM
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Default RE: Perry Pumps and regulators

The pressure controller does not have a throttle range, because there simple is nothing to throttle only reduce.
The term throttling range is not limited to pressure or flow. For example if a proportional HVAC system is controlling temperature and the valve controlling chilled water to an air conditioning coil is wide open at 75 degrees and closed at 72 degrees then the throttling range is 3 degrees. In this case the error is not necessarily unwanted. A PID control system might keep the temp at 72 degrees all summer but it will use more energy because it will take more power to keep the building at 72 during peak summer conditions when the proportional only system would be at 75 degrees. At 75 degrees all summer then some people might be uncomfortable when outside temperatures are below that.
Old 01-26-2010, 07:54 AM
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Default RE: Perry Pumps and regulators

Sport Pilot, gents

When modeling I am only interested in the subject of the thread (and not my job) and for that Hanna and I did open a Perry pump that normally is mounted in the back plate of a glow engine. (Webra Speed 10 CCM)
The pressure controllers dont's have any secret for us. (Cline, Iron Bay, Walker)

See the picture.

Next step is making a nice cross sectional drawing to see if and how we can use this pump to combine with an external pressure controller. Maybe we can eliminate the pressure reducer if there is any in it.
If someone is interested I show that drawing in the near future, otherwise research will continue backstage.

Cees
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Old 01-26-2010, 11:23 AM
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Default RE: Perry Pumps and regulators

Yes TF, please show us that drawing when it is ready.

I find this thread very interesting.[sm=thumbs_up.gif]
Old 01-26-2010, 11:31 AM
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Default RE: Perry Pumps and regulators


ORIGINAL: LNEWQBAN

Yes TF, please show us that drawing when it is ready.

I find this thread very interesting.[sm=thumbs_up.gif]

Here you are LNEWQBAN,

When you have any question about how this pump work, give me a sign an I will show you.

Cees
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Old 01-26-2010, 12:52 PM
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Default RE: Perry Pumps and regulators

Thanks TF, that was quick!

I believe that the bottom portion is a pulse pump, actioned by the muffler pressure.

The top portion is the regulator, which work principle I don't understand.

I believe it is there to keep a constant pressure in the line feeding the carb (around 0.25 inch water gauge), regardless of tank location and plane attitude.
Old 01-26-2010, 02:24 PM
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Default RE: Perry Pumps and regulators


LNEWQBAN,

This is a back plate mounted pump.
Bottom part, what you say, pump, is bolted in the backside of the crank case, the double arrows is the pulsating crank case pressure.

From the pump outlet the fuel is pressed through the valve of the pressure regulator, in the chamber with membrane and above that membrane the adjustable spring.
The valve of the regulator is closed when the outlet pressure of the pressure reducer does get the wanted pressure level.

Adjusted spring force / membrane surface = pressure < pounds/square inch>

The demand of the engine will open the valve a little and the position later is controlled by the membrane during operating, so supply of fuel to the engine is under constant pressure of the regulator.

I do not know the wanted pressure of this pump for normal operation but we did see the pressure of the VP 30 was a ideal 0,25 PSI, and that's about 6,56 inch water gauge. (167 mmwk)
After the proper pressure is adjusted, depended of the type and adjustment of the carb, the outlet pressure can be lower but we do not know.

Cees
Old 01-26-2010, 02:40 PM
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Default RE: Perry Pumps and regulators

Thanks TF!

Then:

1) Is there atmospheric pressure above the diaphragm?

2) Is the fuel constantly returned from the carb needle inlet back to the tank, so the carb takes whatever amount of fuel the Venturi sucks? If so, how to keep the 0.25 psi within that line?

3) Is the diaphragm material cloth impregnated in silicone for glow fuel?

4) Is the fuel tank pressurized from the muffler?
Old 01-26-2010, 03:03 PM
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Default RE: Perry Pumps and regulators

ORIGINAL: LNEWQBAN

Thanks TF!

Then:

1) Is there atmospheric pressure above the diaphragm?

2) Is the fuel constantly returned from the carb needle inlet back to the tank, so the carb takes whatever amount of fuel the Venturi sucks? If so, how to keep the 0.25 psi within that line?

3) Is the diaphragm material cloth impregnated in silicone for glow fuel?

4) Is the fuel tank pressurized from the muffler?

LNEWQBAN (Hope Lazer does NOT find it a problem we use his thread!)

1) Above the diaphragm is atmospheric pressure.
2) Most important question!

In the past I did use this pump with one line to the carb and I think most pilots do.
The 0,25 psi is controlled by the regulator and nearly constant (and depends a little of fuel demand of the engine)
I think this 0,25 PSI can give some troubles when the pump is used in combination with a standard carburetor so we read about lowering the pressure. (I did modify the "low" needle many years back)
When make a return line I think there are more possibilities but never did try myself. I do show a scheme in post 13 I would try, maybe other pilot do have experience with that.

3) This pump is used for glow fuel in the past, as many, the diaphragm material is not cloth impregnated. (Maybe nitrile rubber, but I do not know)
4) It's better to have a lower inlet pressure for the pump than the adjusted pressure of the regulator so muffler pressure can give problems.
I first would try without and use a (little) airinlet for the tank positioned on a lower level than tank bottom so you can turn the plane upside down for servicing. The connection of the airinlet line of course mounted in top of the tank.
When you use a return line (or more) the tankpressure must be atmospheric!!!

Cees
Old 01-26-2010, 03:33 PM
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Default RE: Perry Pumps and regulators

Once again, thank you very much, Taurus Flyer.

Best regards!
Old 01-26-2010, 03:38 PM
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Default RE: Perry Pumps and regulators

ORIGINAL: LNEWQBAN

Once again, thank you very much, Taurus Flyer.

Best regards!

LNEWQBAN

One point I think about, see your question 2)
2) Is the fuel constantly returned from the carb needle inlet back to the tank, so the carb takes whatever amount of fuel the Venturi sucks? If so, how to keep the 0.25 psi within that line?

When it is possible to create a (nearly constant) atmospheric fuelpressure near the carb by using a return line I think the 0,25 PSI isn't so important anymore, that's why I would try two returnlines to the fueltank, see post 13.
So maybe you can easy and automatic create one undisturbed air connection between carb and tank, the second line is used by the fuel to find a way back to the tank. Interesting to try out!!!!


Success,
Cees


Old 01-26-2010, 04:29 PM
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Default RE: Perry Pumps and regulators

Many time I have tried to explain this. That there is a pump (the blue and green) stage and a regulator (the purple) stage. I too have seen one apart. A picture (or drawing) is worth a thousand words.

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