Auto drain cocks

[LnBmad]

With the fox being a fair few years old, she likes to spit out a lot of oil and water when she first starts. Am I correct in thinking that by fitting a set of auto drain cocks the oil and water will be drained and therefore not be spat out of the chimney? I know how they work on a larger scale but haven't got my head around how they work in 16mm

[Keith S]

I'm intrigued by them myself, but haven't looked into it because Roundhouse engines have rather low-slung cylinders, without much room under them, and also because I would be nervous drilling and tapping holes in my locomotive's cylinders. Apparently they work quite well, although I can't figure out how the "auto" part works.

[LnBmad]

I know what you mean about roundhouse cylinders being low slung. But when your loco is in the rails you have a bit more space...

Think the auto is likely a spring to hold it closed until there is pressure enough to open it. But I'm guessing at that.

[Keith S]

I suppose you're right about the spring, it's just that I have trouble understanding why the pressure in the cylinders is high enough to overcome the spring when there is water in them, but not when there is only steam. I mean all the pressure originates in the boiler, and you can't compress water, only steam, so how is the pressure on the spring made higher by the water being present? You must be correct, it's just that I can't picture it. I should have paid more attention in school maybe.

[DLRdan]

The auto part is very simple. There is no spring just a ball, loose in the housing. The when the cylinders have no pressure in them the ball falls off its seat alowing the water or steam out the drain. When the pressure is increased the ball is blown back onto its seat, stopping the steam coming out. They work in large scale as it takes a lot of steam to blow the ball back onto its seat but in smaller scales the ball is much lighter so is easily blown back into the seat.

[LnBmad]

The auto part is very simple. There is no spring just a ball, loose in the housing. The when the cylinders have no pressure in them the ball falls off its seat alowing the water or steam out the drain. When the pressure is increased the ball is blown back onto  its seat, stopping the steam coming out. They work in large scale as it takes a lot of steam to blow the ball back onto its seat but in smaller scales the ball is much lighter so is easily blown back into the seat.

Now that's exactly the sort of answer I was after! So if I fitted a set of these to the fox I should get all the water and crap out through the draincocks and get some clean pulling away?

[Keith S]

I've seen them in Youtube videos, they seem to work. Very interesting explanation. Simpler than I would have thought.

[DLRdan]

From the ones ive seen fitted with the drains they dont work very well, they seem to shut almost instantly and then the water still gets thrown out the chimney. After a quick search i came acros this video. As can be seen, only a couple of drops come from the drain cocks, the rest is being forced out the cylinder ends and dwon the chimney.



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[LnBmad]

Any chance I can get a link to the vid please as my iPad doesn't want to show it me on the forum lol. Might be a case of fitting a summer lands chuffer then so I all comes out the bottom of the loco rather than out the top... Was only considering them as she throws a lot of condensate out of the cylinders every time she starts.

[DLRdan]

Here you go


http://www.youtube.com/watch?v=r_u-Sy8rn8Q

[LnBmad]

In fairness the cylinders in that vid are leaking steam after having been rebuilt, and there was no sign of any water and oil coming from the chimney... Think for £30 it might be worth a go...

[rebelego]

There is no spring just a ball, ...

Thanks for sharing the info.

[rebelego]

Is DJB the only provider of such draincocks, or are there others?