Don't want to pay high prices for a Nitrogen
fill from the FBO on the field? Tired of lugging your buddy's system to your
hangar when you need to service struts or accumulators?
Well, you're not alone!
Beech Lister Eric T. built an awesome N2
system and has contributed his design solution to demonstrate how easy it would be to put
a nitrogen filling station together. Eric reports a total cost of about $140 for
See a great N2 strut filling hack that enables balanced height filling of your main struts HERE.
Here's his design:
TurboTorch 245-03P - this one goes 0 - 500psi. Found it on
e-Bay NIB from an industrial supply house (Johnstone Supply). This was the hard
part to find at a good price. $74.14
Turbo Torch is also available at Amazon for about $64 on 7/10/2020.
McMaster Carr - 3000psi SS braided - 12 ft. Part 4468K591
Schrader Gooseneck Coupler:
Schrader brand from Aircraft Tool Supply. P/N SK2043C. The
basic Schrader Gooseneck coupler is about $15 or slightly less from eBay
Do yourself a favor and buy a spare replacement seal or two
for this puppy to have on hand when the original gets tired. The last thing you
need happening is to have a leaking fitting when you are in a pinch to get your
strut N2 topped off.
The only trick when putting this all together was having to
remove the "out" fitting on the regulator since it was a male threaded flare
fitting, and the Hose needed a female 1/4" NPT.
I also ordered a fancier Schrader coupler from
ATS that had
an internal "pin" that screwed in and out to open the valve stem on a Schrader
fitting. That was $28 (P/N 556) a while back and here is the item now priced at
I hooked this all to an 80 cu ft. Nitrogen tank. Found good
prices on tanks at
www.weldfabulous.com. Probably should have gotten a 40 cu. ft. tank
instead for better hangar portability, but this will be just fine and cut my
trips to the gas shop in half.
Only two things that are not optimal are:
1) size of tank as I mentioned above
2) it might be nice to have a rubber coated hose to prevent
scrapes & scratches while working this thing around landing gear. I think a sit
down with a nice roll of electrical tape can cheaply take care of that.
Here is a pirep from Bonanza owner Mark Y., of CA:
I followed Mr. Caban's posting to the letter and ended up with
a very nice set-up. I think that the total bill was around $250 with the
biggest expense being the purchase of a 60 cu. ft. tank so as to avoid
tank rental charges. The nitrogen itself was only $26.
Additionally, I purchased the T-handled Schrader connector for
connection to the valve stem. It cost about $40 from SkyGeek and is quite
handy since you can depress (open) or release the valve stem core for better
control of the filling of the strut. The goose neck connectors that I saw did
not have this feature--they simply rely on the pressure from the tank to depress
and release the valve stem core.
I found that the mains for the 1968 Model 36 took about
275-295 psi to inflate to the proper height and the nose strut required about
150 psi to inflate. Check your maintenance manual for the correct heights
of the strut extensions.
I do recommend getting the rubber covered hose line. I
purchased a 12 foot stainless steel braided one and it works just fine but to
have a rubber covered line is very little additional expense---maybe $5.00.
I use it for all my tires and struts. It is a very cost
effective investment since I no longer have to talk to a shop when I need to
fill a strut or tire. It was particularly effective in that I had to use
it 4 or 5 times to fill the right main. It turned out that the valve stem
body had a small burr on the internal threads and it would eat into the tiny
gasket on the valve stem core. This burr would produce a very slow and
frustrating leak. My shop bill alone would have been a lot more than
$250 to trouble shoot that problem.
One other item: You will need to find the hose to
regulator adaptor to connect the two together. Industrial supply houses
will stock the item. I just took the hose and the regulator to a outlet
and they pulled out exactly what I needed. Watch the ratings for your
fittings--mine is rated at 10,000 psi. Some hardware store fittings may
only go to 250 psi and you really need to match or exceed the tank
pressures that the system will develop. Connector cost was about $12.
You will also develop a whole new set of friends with the tank
addition. Not to worry. The nitrogen in the tank lasts a very long
time before the pressures begin to drop.
Below is an N2 rig created by A&P/IA, Gary P. which utilizes
exterior coated HVAC hose and flared fittings with o-ring seals. He also notes
that the hose has a burst pressure of 4000psi and a working pressure of 800psi.
The last time I did my B55 main struts I used 600psi to get my proper height
with full fuel, so within the 800psi working pressure limit. You decide if that
could be a working hose solution for your operation.
A strut repair narrative is HERE.