auto dain cock design

[terry1956]

hi, chaps. I have seen an auto drain cock which looks easy to make and I would like to use. but would like your input to make sure I have the design right. the drain cock is made up of a 2/8th inch section of round brass. this round is drilled through with a 1/16th drill. then a 3/16 inch drill for 11/16th. tapped 3/16x32 for 1/8th. 5/16th from the open end a 3/16th x1/2 inch treaded 3/16thx40 brass rod is let in, this is drilled 2/16 through. a cap is made to fit the open end and a 3/16 ball is placed inside. a locking nut is made to suit the tread. and that's it.
may questions are. should the ball be seated at all. is a spring needed to reposition the ball. I have seen these drain cocks working but was unable to ask all the questions I wanted.
michael

[Deleted]

Hello Michael.

There should not be a spring and I'd form a seat for the ball in the usual way. The accepted wisdom seems to be that upon opening the regulator (and the ball away from its seat), the mixture of water and steam creates turbulence in the chamber, keeping the ball off the seat. Once the water has gone, the ball is held on the seat by the steam pressure. (If you think about it they will work as snifting valves too). I see John (Baggo) used these on his excellent Helen Longish.

Regards,

James.

[doubletop]

In my brief experience of auto drain cocks I'd say don't bother. You'll knock the crap out of your motion as the remaining water is expelled through the ports while you pull sway whith the auto cocks closed.

Fit manual cocks and you are in control of when they close.


How do I know? A virtual rebuild of a knackered Simplex

Pete

[terry1956]

thanks to you both. my local club as a polly with auto drain cocks and its been running fine for years, I just like the idea of them. michael

[Tony K]

Michael, there has been lots of discussion on this site before.

Try here and here and here

Looks to be well covered. There may be other threads. Enjoy!

PS - no offence meant but there is a typo in the subject title - it would normally be unimportant except when someone searches on auto drain cock they may not find the wisdom here, so it might be wise to correct it?

[Shawki Shlemon]

From the above thread you can see how they are made , they are suitable for slide valve engines but piston type valve engines I would not use them . If for any reason they got stuck shut , the slide valves will pop open and relief the cylinders but on piston type valves that will not happen . I have used them on more than one engine and seems they work satisfactory , not as good as manual or steam operated but sometimes the lack of space calls for compromise . The ball is in your court mate .

[terry1956]

Thanks chaps, I made the valves yesterday.just waiting for the balls to show up to complete. One of my reasons for not wishing to have manual is I keep damaging the linkage when moving the loco in and out of the car.thanks again.michael