mduslick

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Hi all!

I'm doing research for my next project, and I came across a thread this morning where someone said you can't use a perry pump with an air bleed carb. I'm planning on using my pump (VP-30) with an OS .46 AX, but I have not seen anywhere in the owners manual for whether or not the carb is an air bleed type. My first question is, can the pump be used with this engine? Also, I have noticed in threads that most of the applications for this pump have been with larger engines... is the OS .46 too small to have enough crankcase pressure to operate the pump?

Lastly, because I plan the locate the fuel tank at the CG, I do not have enough room for one 8oz tank because of the way the wing is incorporated into the fuse (the fuse is split down the middle by the center spar of the wing), and I'm affraid if I cut the center spar out, it will weaken the structural integrity of the wing. Instead, I plan to use two 4oz Hayes tanks side-by-side, where the clunked line of tank #2 feeds the vent of tank #1, and the clunked line of tank #1 feeds the perry pump. If I understand the fuel draw concept correctly, is it true that as fuel is drawn from tank #1 by the pump, the vacuum created in tank #1 simultaneously draws fuel from tank #2, so theoritically the two tanks drain by approximately the same amount until they are both empty?

I hope everyone had a fantastic holiday season, and I look forward to hearing from you. Thanks.

TexasAirBoss

My Feedback: (22)

I have used Perry Pumps a few times and with great success. They are great little machines. The "bleed air" idle ajustment refers to carbs with a hole in the front of the carb which allows a small amount of air to be sucked in when the barrel is closed. There is a small screw that goes in the side of the carb and is used to partially close this hole to make fine adjustments. Engines like the OS Max LA series have bleed air idle ajustments, but the higher line ball bearing engines have a better system that has an upper and lower needle adjustment. I'm not familiar with the AX series, but I believe its the higher series and should work fine with a Perry pump.
As far as the two tank system goes, although your theory sounds good, its always best to make things as simple as possible. I would consider a single tank just in front of the spar.

Charlie P.

Your set-up may not work. The fuel will "seek it's own level" and, if you raise or lower the nose if stacked or pull "g"s side-to-side if side-by-side the fuel will self-transfer between tanks. You'll have to add an anti-siphon/one-way valve between them. But that will make filling very difficult.

Put a pump between the tanks to keep #1 topped?

dbacque

My Feedback: (3)

Actually one tank feeding another works fine, I've used it before. But they will not drain equally.

In your description tank 2 will drain completely and tank 1 will still be full (remember, it sucked all the fuel out of tank 2). Then tank 1 will drain.

The only caveat is the additional "suck" required but the pump should take care of that. I used a Perry oscillating pump and had no problems.

Dave

joesabido

What if you run your pickup lines individually right up next to the pump and use a T fitting to join the fuel lines to a single line and into the pump? That way the pump would be sucking from both tanks at once and minimal (if any) tank-to-tank fuel transfer would occur.

Also, the VP-30 could pump way too much for an engine that size even at its lowest setting, so you might need to create a bypass, returning the excess pressure to the fuel tanks through the fill lines, do it if you can't really get you engine to idle properly and/or your low speed needle becomes too sensitive because of excesive fuel flow into the carb.

GarySS

My Feedback: (13)

Hello All, I've got a question for P-20 pump owners. This is the one used with 4 strokes.

Can this pump be mounted near the engine and not directly on the engine?

Reason I ask ---I broke in my Saito 82 with the pump just mounted to its back plate. I thought I had it screws in tight, but I was experiencing a lot of leakage from the engine. When I removed the pump the leakage generally stopped or at least 95% of it. I saw once a P20 mounted to the motor mount and not the engine. Would that work??? Thanks for any info!

joesabido

Gary,

You could put it on the engine mount, but on the same axis as the arc created from engine vibration (i.e. perpendicular to the crankshaft), the pressure will be reduced also. If you put the pump on the firewall it won't work. The pump needs to be shaken longitudinally for it to do it's job.


Fuel leaks are not common when using this pump, it's not heavy enough to put a lot of stress on your engine, maybe you have a blown gasket or seal?

mduslick

My Feedback: (1)

Thanks guys. I think I found a way to fit the 8 0z tank in, so I can just use one single tank. My concern now is the pump... as far as it possibly delivering too much fuel to the engine. I have attached a "very" basic diagram showing where components are to be located in relation to each other. The engine is mounted on a pod at the rear of the plan, and the pump will have to draw fuel approx 22-1/2" to the rear of the plane, about 8" up the middle of the fin, then about 5" or 6" forward toward the engine. Will the pump still be delivering too much fuel for the OS .46 AX in this configuration?

The Ghost

I don't know about the perry pump, but the Robart one that I have will draw fuel up from a height of 29 1/2"(I tried it just to see how good it is) The drawing that you done the pump should have no problems.

Cheers

joesabido

mduslick,

VP-30's push better than they suck, so my advise is to put it near the tank. If having excesive pressure (difficult to idle) then use a bypass to return the excess fuel to the tank.

mduslick

My Feedback: (1)

So the tubing that connects the crankcase tap to the bottom of the pump doesn't have to be 4" or less? The pump can be located anywhere?

mduslick

My Feedback: (1)

*

joesabido

Well, you could try

Perry says to keep it short "for maximum pumping action", but that on a VP-30 usually equals "too much pressure".

If you're gonna go long on that tubbing, make sure it's STIFF tubbing.

mduslick

My Feedback: (1)

hmm... why stiff tubing?

joesabido

Becaaaaause, soft or very flexible tubbing will "inflate" on pressure.

Do this test:

Grab a 10" piece of standar fuel line and plug one end, blow on the other end and you'll feel you can actually push plenty of air and when you let go you'll feel the tubbing blow the air back out, like a balloon.

That will pretty much make you loose pressure on the pump.

mduslick

My Feedback: (1)

oops, that was a stupid question, wasn't it? [&:]

joesabido

My gringo friend, the only stupid question there is, is the one you never ask

Besides, that's what this place is for!

mduslick

My Feedback: (1)

Thanks. :-) I'll let you know the results of my tests, then post pics as I begin the build process. I'm really excited about getting strated with this winter project... if you can call it that as warm as it has been lately. Gotta love it!!!

joesabido

Cool dude! Let us know how it all comes along. Our "winter" here is a joke too, we're around 95ΒΊ F with 90%+ humidity. And the wind here doesn't blow, it sucks!

mduslick

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LOL!!!! At least that gives us more time to fly.

joesabido

I would rather fly in the cold, really [&o] Heat and UV levels here are just unbearable [:@]

mduslick

My Feedback: (1)

Then pack your gear, head this way, and join us on the field. We'd be glad to have you as an honored guest at our club (Charlotte Aeromodelers)! I would imagine the weather would be a tad bit more comfortable.

So what do you have in your hanger my friend?

joesabido

Hey thanks for the invitation! It would be kindda hard (a lot actually) for me to go all the way up there with my plane and gear though. International customs would look funny at me trying to get into the US with this thing:



[&:][&:][&:]

I'd actually move to the US for 2 main reasons:
1.- Wouldn't have to wait for a month to get a $40 servo
2.- Wouldn't have to pay MORE for shipping and import taxes than for the $40 servo
3.- Better weather (ok 3 reasons )
4.- Lots of airfields (ok, make that 4!)

Oh, and the name is Joseph [8D]