Oil pressure gauges

[Howard Wright]

Hi All

I believe mechanical oil gauges work by pressuring a coiled tube which straightens as the pressure increases and moves the needle.

My question is can excessive pressure damage the gauge?  The reason for the question is that early gauges read to just 10 lb/sq in, later ones to 20.  With a re-bored oil pump, on start up you can probably expect more than 20 lb/sq in.  Clearly when warm the pressure will be in the range of both gauges.

I have a 10 lb / sq in gauge and re-bored pump should I get a larger gauge?

Cheers

Howard

[Renaud]

Hi Howard,
You are of course right about the coiled tube. A french patent by Mr Bourdon (tube de Bourdon). I would indeed change the gauge myself for such an increase in pressure but it would be probably only a precaution?
Cheers,
Renaud

[Chris KC]

Howard, the pressure you get at start up will depend on several factors including the grade of oil you are using and the setting of your pressure relief valve. Just as an indication though I'm running a pressurised engine with an over-bored A7 pump and that generates about 50 psi when cold. I can only guess what those gauges will take, especially at 80 or 90 years of age. Just keep in mind that the wider the range on the gauge, the harder it becomes to monitor oil pressure while running as the resolution becomes too small to read.

Perhaps others can confirm, doesn't the standard A7 PRV open at about 20 psi?

[Tony Betts]

100% with KC,

I run an original pressure fed ulster engine, with a STANDARD oil pump. And I get 45 to 50 lbs on start up. 25 lbs on tick over.

A standard engine will go off the gauge with 20lbs gauge on start up.

So the standard austin oil gauges should hold up.

I dont know why, but austin started with a 20lbs david Harcourt gauge, the dropped to a 10lb. And when the three bearing engine came in, they went back to a 20lbs gauge.

Tony.

[Howard Wright]

Thanks All

I had thought the 20 lb gauge on my 1930 RK was a later fitment but according to Tony it might be original.

Cheers

Howard

[Mike Costigan]

Yes, Howard, late RKs had the 20psi oil gauge instead of the oil button.

[Ruairidh Dunford]

Howard,

what is the chassis number of your RK please (roughly)?

[AustinWood]

I have fitted a Morris Cowley gauge below the dash. It reads to 10psi but when cold the needle goes right round to the stop.
The writing at the bottom says it can withstand 200 pound over pressure.


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[Chris Garner]

In a former life I dealt with bourdon tube and pressure gauge manufacturers both here in the UK and in Switzerland.
It is highly unlikely that a 10 psi gauge would be damaged by the sort of pressures that a Seven engine, in all variations, could generate.

[Howard Wright]

Hi Ruairidh 

1072**

Cheers

Howard