Calling RAF technicians

[Airspeed]

I'm fairly sure that we have members with this knowledge, so here goes;
In my collection is a Sperry MkI Artificial Horizon 6A/599.
I have removed front and back covers, revealing the mechanism, which suffers from a seized gyro.
I cannot see how to remove the mechanism from the casting, as the front view is blocked by the curved sheet metal backing plate for the horizon bar, and rear view blocked by the mechanism itself.
That metal plate seems to be held by two straight slotted metal screws/bolts.
The screws appear to need a right angle screwdriver.
I'm loath to proceed in case I'm on the wrong track, and find myself unable to replace those screws if they do come free.
I have read my AP1275A Instrument Manual 1937-39, which in short, tells you to send the unit back should it require more than basic cleaning.
The manual also says that the unit should have been locked upon removal from the aircraft.
It wasn't, and the little "S" shaped pointer is detached from the back of that curved plate.
Anyone experienced removing the mechanism, could you help, please?

[petermcleland]

I think I would just give it a squirt of WD40 and leave it to drain

[Motormouse]

Ok, 6A/599 is the RAF parts catalogue section/reference number for the gyro IIRC section 6 covered
Instruments (and probably still does!) What would also be helpful now is if you can provide a makers part or model number, as the 6A/599 designation could cover several variants of the same basic instrument.

Ttfn

Pete

[Airspeed]

Ok, 6A/599 is the RAF parts catalogue section/reference number for the gyro IIRC section 6 covered
Instruments (and probably still does!) What would also be helpful now is if you can provide a makers part or model number, as the 6A/599 designation could cover several variants of the same basic instrument.

Ttfn

Pete

Hi Pete,
The face plate directly behind the glass is embossed with the Sperry logo (SPERRY inside an oval with a pair of wings), above which is MK, over I.
Stamped into it is Ser. No L 72090
The back casting is stamped G 6A/599 on the left of the air outlet. On the right is stamped 9224/40

I can't find any other markings except for some rather scrawled numbers scratched into the dull orange coating inside the main casting.

Thanks for your reply, much appreciated!

[Motormouse]

Take a look at this: http://www.google.co.uk/url?sa=t&rct=j& ... 5102,d.ZGU

Think it should help you out.
(Pdf file)


Ttfn

Pete

[Airspeed]

Pete!
Precisely what I needed, my friend!
It even mentions:
"loosen with special off-set screw-driver, T-22261, and continue operation with geared, off-set screw-driver, T-22260"

Naturally, I had neither tool, and used an angle grinder to cut down a hex drive slotted screwdriver bit to fit. Held in needle nosed pliers, I cracked them loose. Phew!
Having cleared the rear air-breathing bearing, I was soon able to get the gyro humming nicely using a balloon neck, and a balloon pump. (The compressor would not be popular indoors tonight)
It wouldn't pass testing for aeronautical use, but whenever possible, I like to see the collection working at least in demo mode.
Now that it's dismantled, I'll add photos to the AFV gallery before re-assembly.
I'll also be able to re-attach that pointer. Woohoo!
Many thanks to you.

btw, Peter, the Manual also says "do not use a squirt of WD40, RP7, or CRC 56, because they haven't been invented at time of writing"....I found that quite interesting.

[Motormouse]

Glad to help.

Ttfn
Pete

Ps Does manual mention Stoddard Solvent,? ( invented in 1928 btw.)

[Airspeed]

They do list a lot of consumables, Pete, but I didn't come across Stoddard Solvent.
PS, Out in the Museum, I'll hook up the vacuum side of my air compressor and give it a real wind-up.

[Airspeed]

OK,
Anyone wanting to see the insides of a real one:
http://airspeedsflyingvisit.webplus.net/museum4.html