Hawker Hurricane Oil Temperature Gauge

thank you Stan, i’ll give him a call now.

May I suggest that the instrument be sent to the opposition? Bruce Irvine at Airtron Instruments. Email [email]bruceirvine@tiscali.co.uk[/email]. He did the oil temp and pressure guages for the Fox Moth for me. It is an involved process and needs the correct equipment to be successful.

Coolant gauge

Good morning everyone,
I work as QA Manager for Marilake Aero systems in Ferndown, Dorset, we repair avionics equipment and instruments for many types of aircraft.

Recently we received a Mk VIIIH oil temperature gauge (stores ref 6A/494) removed from the last flying Battle of Britain aircraft (R4118), we would sincerely like to return the unit serviceable so that the aircraft can remain airworthy, but the capillary tube between the gauge and the temp bulb is leaking and we dont have any repair documentation that shows us how to dismantle the temp bulb.
does anyone have anything we can use to help us service the unit and keep this classic aircraft flying please (we only have the test section from Air Pub 1275)?

AP1275 1939 lists 6a/494 as coolant gauge, Mk VIIIH, ethyl ether filled.

RAAF Schedule of aircraft instruments 1946 lists Mk VIIIH with 10 ft capillary also used on Spitfire, 15ft capillary on Battle and 30 ft capillary on Mosquito so NOS spares might be around. Just roll up the excess capillary.

Oil temp gauge is fitted with mercury injected at high pressure. I am not an instrument tech, but I figure that most folk have avoided rebuilding these gauges because NOS was around, and the method of manufacture is fussy to recreate.

‘Instruments’ Category X Licence by RW Sloley, Pitman 1935 gives some clues for coolant gauge :
capillary tube has 1mm bore, ethyl ether boiling point is 34.6 degrees C, so I guess that ethyl ether was cooled to < 34 degrees when bulb was filled.

‘Aircraft Instruments’ by J Riley, Engineering Dept Smith & Sons, NAG Press (did my wife have a printing press?) 1939 gives some more :
the capillary is soldered to the gauge and the bulb, flared sleeves being fitted to prevent damage to the tube.

So the bulb cannot be dismantled without melting the solder at the top, which would no doubt volatize the ethyl ether. I wonder how they filled the bulb with ethyl ether then soldered the capillary in to begin with ?

Maybe it’s like the mystery of fried ice cream, which a chef showed me the secret of making after I had washed ten thousand dishes in my kitchen hand days….

Perhaps the bulb was filled with <34 degrees liquid ether in a coolroom then placed in a holder with the bulb base immersed in ice/dry ice. Then the top of the bulb could be soldered with a hope of preventing volatized ether escaping into your face or depressurizing a pressure based system.

I would be interested to talk to somebody who could successfully resolder new capillary to old gauges & recharge with ether or mercury under pressure all the old gauges that have work or age hardened capillaries or tin snips applied to the capillary to assist in removal.