Filling high pressure Suspension units

[Graeme Bird]

My C42 requires hundreds of PSI in the main wheel suspension units, how do I inflate them? someone said with a nitrogen cylinder but I don't know where I would get one.

[Steve Brown]

If you want to be self sufficient and have some cash......

http://www.aircraftspruce.com/catalog/t ... utpump.php

Air fill rather than nitrogen but you can't have everything!

[Graeme Bird]

Thanks for the advice, I have seen someone else on the web saying they wasted money on the strut pump - its expensive and didnt work well.
I can get a 9lts 80cm nitrogen bottle for £40 deposit, £18 cost, plus £25 round trip delivery from Adamsgas.co.uk
So I would need a regulator etc.
What about these battery operated compressors, they are supposed to go upto to 250psi, shouldnt they do it?
Sounds like 4 x4s have similar struts

[Bill McCarthy]

BirdyBoy,
Forget the battery powered compressor, they are absolutely useless. Either go to a facility that has a nitrogen bottle/reducer unit to charge the struts which will be minimal cost or splash out and get the gear.
Ed Shipley flew into Wick last year with a Mustang along with the guy who restored it and asked for nitrogen to top up the tailwheel suspension strut. The only gear available was for pumping up tyres and they expected it to stand up to the 500psi required for the job. When the hoses kept blowing off, the restorer announced "this is shit equipment". I said, which end, ours or yours, which caused a serious sense of humour failure.

[Steve Brown]

Good advice Bill

Don't believe all you read on the web.There are often conflicting views.

ie

http://forums.piperowner.org/read/4/23939/23968/quote=1

I have personally used a strut pump very successfully on our Comanche - very controllable and we got just the right ride height. I prefer to be in control and the pump gave me that.

Regards
Steve

[Bill McCarthy]

BirdyBoy,
Should you go for the portable cylinder and reducer unit, you can always go to a facility that has the larger cylinders on a trolley and probably get a free top-up rather than send it back to an agent. Incidentally there are two qualities of nitrogen. The type used to inflate aircraft tyres may have a minute quantity of moisture in it. The other is called white spot nitrogen and has a guaranteed minimum amount of moisture present, and is "too good" for your purpose. The advantage in using the cylinder/reducer unit is that you can start at zero pressure on the outlet side of the variable reducer and screw in on it until you achieve the ideal pressure in the struts to suit your particular loading set up. Note this pressure and use it to reset them when necessary. Even if you are away from your home strip you can rest assured that you can recharge them with similar equipment to your pressure (without electrics).

[Graeme Bird]

Well all that good advice - but conflicting.
I have been looking for a gas regulator - 2000 psi in 0-300 psi out (30 bar) nitrogen, couldn't find anything less than £180. I thought I would try my electric one as someone said that they had used one ok. It was supposed to go to 200 psi but I lost some air connecting it, it read 260 (in the red), the 10A fuse blew and the strut sank right down on disconnecting it. So I now have a sad lopsided plane!
Any suggestions on a source of regulator and connecting cable/valve - lit looks like a car valve.

Thanks for all your responses though.
Graeme

[G.Dawes]

What kind of valve do you have, if it is the one with the locking nut, release the nut a bit then blow in, lock the nut and disconnect. The shrader valve does like very high pressure.

[Graeme Bird]

hi, the valve on the plane is a schrader, on my compressor its the car type push over and clamp - not right at all.

Graeme

[Bill McCarthy]

BirdyBoy,
You could use another inert gas - argon. If you go to a welding outfit, they might lend you the bottle and regulator in return for a flight. We used to have these regulators lying about all over the place and nearly all of them would give an output much greater than you mention. If you track any regulator down, make sure that the thread matches that of the cylinder ie. - a left hand thread and it should say "For Nitrogen use only".
Argon, by the way is used for TIG welding, purging stainless steel components.

[Dave Hall]

I thought my argoshield MIG welding regulator is the usual right-hand thread, as too was the CO2 bottle I used before.

I think the only left-hand threads I've found are fuel gases such as hydrogen, acetylene and maybe propane - and the camping stove hose has a left-hand thread ISTR.

Anyway, forewarned is forearmed - just check the threads first!

[Bill McCarthy]

I believe all inert gas bottles used in industry use left hand threads as a safety issue - to prevent them inadvertently being connected to an oxygen system which has right hand threads.

[Graeme Bird]

hi, thanks for your posts. No, its a clamp on one from a UK company PCL, I noticed though that it has an adjustable center pin and maybe I just need to get this right so that the rubber o ring has made contact with the rim of the schrader valve.
I have borrowed a bottle (near empty though) with a 0-400psi valve from Aiden at London Gliding Club.
One thing puzzles me I had oily foam come out of the strut valve as it went down - is that some kind of sealer/lubricant?
I'll try and get a replacement bottle from BOC.

Graeme Bird

[Geoff. Collins]

Oily foam means there is a slight leak from the hydraulic side into the nitrogen pressure side. Assuming this is a normal oleo?
A rapid de-pressurize will cause it to blow foam. It will probably blow back up ok though. There is a "walk round" pack on e-bay, in the aviation section. All the required fittings and a portable nitrogen bottle in it. Also, one or two gauges you may be interested in.