Topgun2mo

My Feedback: (45)

I finished all of my pneumatics plumbing last night. The retracts, doors and speed brake are on one system. I pumped up the system to 90 psi at 9:00pm last night and at 6:00am this morning it was at 50psi. Is that an acceptable leak rate?

Thanks

seanreit

My Feedback: (60)

Hell yes, I can go from a hundred to 80 in 30 minutes and live with it. All I want out of my air system is a good 20 minutes of plenty of pressure.

Mike, the main thing I test for is GEAR UP LEAKS. My gear are down maybe 30 % of my flight activity. Taxiing, etc. Most people forget to test their gear in the up position which is the most likely place you're gonna have an air problem and not be able to get your gear down.

When I mentioned this to Kenny, a big light bulb went off

I'd investigate with windex in obvious places, but I don't go completely anal on my air systems as long as they get reliable.

Last year I had two gear up landings at Lubbock on my roo. What I found there was that the gear door sequencer had changed the drive range of one of my gear servos. Man was I PO'd. Air system was perfect, valve didn't get moved to gear down position. Scraaaaaaaappppppppppeeeeeeee[:@]

Topgun2mo

My Feedback: (45)

Wait to you see this air trigger set up....no sequencer!

Woketman

My Feedback: (6)

Test schmest! Time to fly it (or at least test run the Peggy).

You done playin' with those sissy-boy countertops?

Jet Doctor

Topgun2 - Leakage rate is fine. You may want to consider putting your airbrake/brakes on a seprate bottle though. Reason - you want retracts to work when landing is obvious. Unless you are using air up, spring down retracts, I would not put the airbrake on the same cylinder as the retracts. Rather put wheel brakes and airbrakes together.

My 2 cents worthless

Zane

Topgun2mo

My Feedback: (45)

One more trip to Lowe's and a little more to do!

Of course you are doing a little more than just countertops! Let's see how many Kincats you could have had.........

sirrom

My Feedback: (4)

TopGun,
This is just my opinion but find and fix the leak. It could be the start of something that could get worse as time goes on and could cause a failure somewhere in your system. I build my systems so that they are capable of holding their pressure for 24 hrs withing 2-3 psi of what I started with. If you can do that you know you have a rock solid system that you don't have to worry about at all.

seanreit

My Feedback: (60)

That's funny, In my experiance the air systems I've built that had zero leaks were the ones I was most nervous about. Kind of like some full scale aircraft, if you don't see oil leaks everywhere, you get very concerned!!

Topgun2mo

My Feedback: (45)

I have 2 tanks T'd together which will supply the springair retracts, and the airbrake. The airbrake must be on this system as it needs the higher pressure and volume to funtion. I have a separate tank for the wheel brakes as this will be a lower pressure....50-60 lbs.

patf

My Feedback: (4)

Mike

I agree with sirrom, and the others too.. there is a problem which you will want to chase down. I would not let that level of issue stop me from flying, but it would be pretty high on my list of priorities. my gawd awful ugly tg f-15 holds 100 psi for months at a time... at least it did till i ripped the nose off in a catch fence. my guess it was so ugly the air did not want to escape to see it. I would try to get to a 24 period of holding pressure.

Topgun2mo

My Feedback: (45)

Pat I would venture to say that your TG F-15 only has retracts. With that said, do you think you would still have the same leakage rate if you added quick disconnects for the airbrake, door cylinders, airbrake cylinder, and about a dozen T's?

seanreit

My Feedback: (60)

Pat's anal enough that I suspect he would have no leaks no matter what.

I've seen Pat spend 6 hours at the field sitting with his legs crossed fiddling with a needle valve on that F-15 to get the perfect low end idle that bursts to full power with no lag.

I've never met anyone else with that kind of patience in tuning.

I like Wocket's comments, COME ON DUDE, LET'S LIGHT THAT TORCH!!

Topgun2mo

My Feedback: (45)

Well Bud it's getting closer to torch lighting time!@!!!!!! I just have to drag Wocket over to my house so he can teach me how to make my Multiplex move some servos.

Pneumatics-Done

Servo's- Partially Installed

Turbine- will do a basic install and remove for bench runs.

Dang trouble is I can be pretty anal myself.

patf

My Feedback: (4)

brakes and retracts on the -15

i think it will be time well spent the first time you blow all the doors off landing with "hanging" gear. bring it and wocketman to greater southwest!

sean if i could sit crosslegged that long i think it would be permanent

Woketman

My Feedback: (6)

We'll get those servos moving this weekend, promise.

S_Ellzey

Hi Mike,

You might try pumping the system up and cycling everything several time, then pump it up again and try it gear up. If it still leaks try with the speed brake open (assuming it is not spring closed). If it still leaks try clamping the supply line to the valves, including the brakes. If you have some time you should be able to isolate which part of the system the leak is in.

I have seen several new retract valves that leak at about the rate you are seeing right out of the bag.

You can also spray window cleaner on parts to see if they blow bubbles, and if you feel sporty you can pump the system up to higher pressure (120-130) and see if any lines blow off, or the leak makes enough noise that you can hear it, and find it.

Good luck,

Steven

dbarrym

My Feedback: (47)

I have had a couple of slow leak situations like this (including one right now) where injecting a small amount of BVM Thin Lube into the air supply line at the valve (downstream of the air tank!), then cycling the system through 3-4 full tanks of air to distribute the lube, has helped reduce or solve the problem, especially if the air cylinders/O-rings were new or had been dry for more than a few weeks.

Barry

EDIT - I meant to say "BVM thin lube" not Parker Super O-lube....my bad.

Topgun2mo

My Feedback: (45)

Thanks Steven. Do you ever prelube any of your pneumatic items prior to install? I had asked BVM and they recommended against it saying only use the o-ring lube on problem areas.

All of these parts have been sitting in a box for about 18 months. I'm sure some are dry. I also want to try and lube the quick disconnects first to see if those being dry is the problem.

DavidR

My Feedback: (1)

I would go with what sirrom says as well. My Phantom has been flying for three years now. It has three seperate air systems and zero leaks in all of them. I can go for periods between jet meets as much as a month and it is still holding air. I check it at both gear up and gear down positions. Nothing is worse, especially on a scale airplane than having the gear unlock then spill the air, then you have a dangling mess. And..... a lot of repair time on your hands.

seanreit

My Feedback: (60)

I've always wanted to ask this question:

Beyond the more flamables on board issue, is there any reason why the air system on board could not be filled in the cylinder with liquid propane/butane?

I would think you could get a lot more cycles of the system with that on board than with compressed air. I've never seen anyone talk about this before and have always wondered if it would work (conceptually).

The right people are in this thread to ask, so there it is.

patf

My Feedback: (4)

sean

you would be better off with nitrogen. it is more temperature stable, hence why many pro-series racing cars use it in the tires etc.

be easy to find the leak if you did use propane tho! and real exciting for the first startup after the fuse fills up with the gas

S_Ellzey

Years ago we used freon. You get more cycles per fill provided you get some liquid in the tank. The down side, other than that end of the earth as we now know it due to destroying atmosphere, was that it washed the lube off the O-rings so you had to continually add oil to the system. I would guess that propane/butane might have a simular problem.

Topgun2mo

My Feedback: (45)

Well I used the windex and found that the Robart retract valve was leaking a bit, a bit from the speed brake air valve and from some of the metal T fittings I used.

seanreit

My Feedback: (60)

I've had more success with plastic t's than metal ones. I personally think it's a myth that the metal are better, but glad you got your leaks resolved!

Topgun2mo

My Feedback: (45)

Sean,

I thought these metal ones were all machined but the part leaking on all of them is between the pressed in or screwed in piece. I think it is gonna be plastic Ts now. BTW does anyone know the difference between BVMs large and small Ts????