Rob Roy 3.5” Drain cocks

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Paul3484
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Rob Roy 3.5” Drain cocks

Post by Paul3484 » Wed May 22, 2019 8:22 pm

Hi

I have just picked up a Rob Roy and am interested in fitting the Auto drain cocks was this an easy job to do?
Any advice would be great

Regards
Paul

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tom_tom_go
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Re: Rob Roy 3.5” Drain cocks

Post by tom_tom_go » Wed May 22, 2019 8:38 pm

Hi Paul,

Are you planning to make these yourself or fit commercial ones as it might be easier to buy off the shelf?

Paul3484
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Re: Rob Roy 3.5” Drain cocks

Post by Paul3484 » Wed May 22, 2019 8:51 pm

I will get off the shelf, but not sure now reading the auto are the way to go my be the normal Manuel operation ones bit more involved in fitting.

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Re: Rob Roy 3.5” Drain cocks

Post by tom_tom_go » Wed May 22, 2019 9:30 pm


Paul3484
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Re: Rob Roy 3.5” Drain cocks

Post by Paul3484 » Wed May 22, 2019 9:44 pm

Thanks

That’s where I saw the bit about drain cocks, then looking into them found this on a site that sells them.

AUTOMATIC DRAIN COCK
Note: This Drain Cock is of the pressure release type. It is set to open if the cylinder should prime during operation. The pressure release is set at approximately 90psi - ie above the normal operating pressure. In effect it is for the emergency release of water should it prime the cylinder.
This means that it will not allow condensate to escape during steaming up. If excessive condensate should fill the cylinder during steaming up (sufficient to lock the motion) it will be necessary to remove the drain cock, release the excess condensated water and replace the drain cock before moving off for the first time.
The release pressure can be reduced by grinding the spring shorter.
An alternative type of automatic drain cock does not have a pressure spring but instead just has a loose ball. Condensate will dribble through this type of drain cock during steaming up.
The ball then relies on cylinder pressure trying to escape through the drain cock whilst the engine is work- ing to keep it firmly sealed against the exit seat of the drain cock.
This type of drain cock will not release water in emergency should the cylinder prime during operation.

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