Topic: Cylinders - drilling the steam passages

[Arminius]

Nice work, Dennis!  Now then, that wasn't so bad, was it?

Next operation would be to make those holes into slots.:-)).

You could do this the hard way by chipping and filing...  Or, fill the just-drilled holes with a soft-soldered brass plug and drill 2 holes between the existing ones, using your now proven method.  A little filing and walla, perfect steam passages!

Why bother you say on such a small model?  Because the exhaust steam has to flow through the ports at low pressure, that's why.  And this is best done, for good performance, through large steam passages.

BTW, what is the bore and stroke of this cylinder assembly?

Arminius

[Ferd]

Nice craftsmanship, looks really clean. I also like your approach to painting parts as they are completed. That has always been my preference and I have also seen many complete the model and disassemble once done to paint. To me getting all traces of oil off at that point seems far more of a daunting task.
cheers Ferd

[bambuko]

Thanks locomate
Your cylinder passages look perfect indeed.
It's good to see other people's work, specially as nice as yours 
Even more pleasing is seeing 2.5" National Association member posting here (but that's another story ...)
Look forward to seeing more progress pictures.

Chris

[locomate]

OK guys, I am posting some pics of one of the cylinders I have been working on, and the chassis progress to date. I am pleased to say that the proposed method of lining up the cylinders for drilling the steam passages worked fine! and yes, I am a member of the National 2.5 inch gauge association, and have also been talking to several other members who have been equally helpful.

I just hope the pictures upload okay.

[Ferd]

I second that request. Would love to see pics. Add as many as you like.
cheers Ferd

[bambuko]

...which is for a 2.5 " gauge Dyak - LBSC design...

Hi locomate,
How about posting some of photos of your loco/work in progress? 
I am great fun of LBSC's designs.
Are you a member of 2 1/2" Gauge Association?
Happy New Year!
Chris

[locomate]

Thanks so much, guys for all your very helpful comments.

I will try and post a few pictures when I get a chance, which hopefully will show the set-up on the mill, and hopefully the end result. As it happens I am a bit stuck at the moment, because my wife will be in New York over the weekend and she's got our camera! Anyway I won't have time to do much model engineering until some time next week, as I have a busy program ahead of me. Tomorrow (Friday) I plan to be at the Model Engineering Exhibition at Sandown Park most of the day, and Saturday I will be working on the Bluebell Railway down in Sussex, and Sunday I will be helping to run trains (7.25 " gauge) at my local ME club at one of our Santa days.

One thing by the way, I have read that it might be a good idea to put a small flat on the cutting edge of the drill to stop it snatching when it starts to penetrate the steam port.

Cheers, and thanks once again. Dennis.

[Arminius]

Just one adder to my post above:

The cylinder cover flange must, of course, be large enough in diameter to adequately cover the steam passages also.

Arminius

[Arminius]

Bruce,

Sometimes you can't see the forest for the trees. :-))

A very good suggestion, indeed.

Arminius

[Bruce_Mowbray]

Dennis,

If possible, make the angle less severe. You could actually start the drill away from the bore and mill a slot into the bore once the holes are drilled. This will also reduce the chance of a knife edge piece of cast iron breaking off and fouling the cylinder bore. If you were to mill the steam passages from the slide valve seat deep enough, without breaking into the bore, you may be able to drill nearly vertically from the end of the casting. 

[Arminius]

Dennis,

I think I understand the drawing you are describing in words.

Eyeballing the situation I would proceed as I described in my previous post to the point where I located the edge of the cylinder bore.  Then move the spindle away from the edge of the bore by a judicious amount, say .065" which would leave .015" between the very edge of the bore and the edge of the drilled steam passage. 

If pressed for space you could decrease this offset from the edge of the steam passage to the edge of the cylinder bore to as little as you wish, say .005".  Then drill the steam passage as described previously, and open up the connection to the cylinder bore for as deep as required using a small endmill say 3/32" in diameter.

Hope this helps.

Arminius

[locomate]

Arminius,

Many thanks for your very detailed comments. There is just one thing that still bothers me a bit, and that is that if I start the hole exactly at the edge of the bore (having milled a flat spot as you suggest), the drill will cut into the bore too far because of the relatively shallow angle, which in my case is only 12 degrees. On my cylinder (which is for a 2.5 " gauge Dyak - LBSC design), the bore diameter is 0.8" and the distance between the port face and the (nearest) edge of the bore is 0.25 ".The overall length of the cylinder is 1.625 ", which means that, according to my drawing the drill will cut away some 0.18 inches of the bore at each end. The drill size specifed for the steam passages is numer 40 which is just under 0.1" diameter.

For these reasons I had planned to start the drill as close as possible to the bore without actually penetrating it, and then milling a flat to link the passageway to the bore. Sorry if this sounds a bit complicated, I really should send you my drawing. I think you will generally get what I am trying to describe, though.

OR, am I being unduly concerned?

[Arminius]

Dennis,

If you do not have CAD available to draw the set-up, I agree that making an accurate drawing at 5x or even 10x full size, and measuring the required angles for set-up on the vertical milling machine, is a good way to proceed.

I designed and built a duplex steam pump, which was described in MODEL ENGINEER in 1995 I think, that required the drilling of numerous passages at various angles, and I proceeded as I described.

The steam cylinder block was clamped to an angle plate such that the required drilled passage was vertical and parallel to the milling spindle axis. Using the "sticky pin" (wiggler?) edge locator I centered the spindle over the edge of the cylinder bore.  Then produced a flat spot with a centre-cutting endmill (also known as slot drill with 2 cutting edges) followed by an appropriate centre drill.  Only then did I use the actual drill for the steam passage.  Doing it this way precludes the drill point from wandering away from the wanted location.

Also gauge how far you have drilled so that the hole does not terminate where it is not wanted.  I placed a toothpick into the intersecting passage to let me know, by its wiggling, that the drill point had arrived.

The pump is fitted and plumbed onto my Hudson 2888 locomotive described elsewhere in this forum.

Good luck, Dennis, and let us know on how you make out.

Arminius

[locomate]

Hi Bruce

Thanks very much for your reply. I've done exactly what you suggested and made a X5 scale cross sectional drawing of the cylinder, taking measurements from the job. I hope I've got it right, but at least I now know fairly accurately the angle at which I need to set it up for drilling. I did try and send the drawing to you but something went wrong although the file is only 2349KB. (somewhat less than the 15000 KB allowed)

Best wishes and thanks again.

Dennis

[Bruce_Mowbray]

You could draw make a 5x scale drawing and measure the angle with a protractor. Transfer the angle to you drilling/milling head and make an accurate layout of the entry point for you holes.


Bruce Mowbray
Springville, PA