Steam passages between cylinder and steamchest.

[rrmrd66]

Afternoon everybody.

I need some advice, please.

This is in relation to my 5" gauge Hunslet build but equally applies to almost and cylinder construction, I imagine.

I have milled out the two 1"x 3/16"x 9/16" depth steam ports in the steam chest face of the PBz cylinder casting.

It is a balanced port design so no central exhaust port.

I now need to join the bottom of the ports through the cylinder wall to the end cover flange face.

These holes are at about 40° to the axis of the cylinder and have to be lined up by eye. They are about 1.25"- 1.5 " length and apparently  I should be able to fit two in between the tapped holes for the end cover screws.

Don Young suggests drilling 2x3/16" holes right though to the base of the steam chest ports and then widening it out to an oval with an end/slot mill.

I am struggling how to machine the holes into slots as even long series slot drills are nowhere near long enough.

What does everybody else do?

Suggestions please.

Cheers

Malcolm

 

[weary]

Hi Malcolm,

I used a couple of different shaped 'Carbide Burr' tools in a 'dremel clone' fitted with flexible drive for ease of control in similar work widening adjacent drilled holes into slots. The most useful shape was a 3mm diameter cylinder with a rounded end ('bull nose'), but similar plain cylinder and pointed cutters ('tree' shape) and a small round ball cutter were also useful. The overall length of these tools (from Arc Euro Trade) varies from 1 5/8" (cylinder style) to 1 1/2" (ball style) so should be just adequate for your job held in the chuck at their absolute limit and with gentle use to finish the full depth. I had to do that to cut my steam passages and it went OK.

In my experience you will definitely need goggles that fit tight to your face if you choose to do this as it generates extremely fine dust which goes absolutely everywhere.

Relevant Arc Euro catalogue page as example of the carbide burrs I am referring to. Usual disclaimers, other suppliers available, etc., etc., etc., ad nauseam.

Regards
Phil

[rrmrd66]

Hi Phil

Thanks for the tip.

I have a Dremel with a box of burrs etc for Senior Management's miniatures house electrics.

I will give it a try.

Cheers

Malcolm

[Deleted]

Hi Malcolm

As with Phil I have also used a dremel with flexi for such jobs..

Pete

[steam4ian]

The cylinder port situation always causes me some mirth particularly when I see the rant of some advocating highly designed exhaust and drafting systems based on free breathing.
All their work is undone by the constricted valve chest the cylinder passages on most miniature locos. Great effort was expended in full size to get as large a passage as possible and a similar smooth passages from the steam chest to the blast pipe.

Two 3/16" holes do not cut the mustard.
Unfortunately that is what we are left with for most designs and few could afford the complex casting or fabrication needed to get the wrap around steam passages of modern prototype designs.
An intermediate improvement would be to build up the slide valve face as a layer on top of a flat on the cylinder casting. A broad slot across the cylinder top could connect to the port faces bolted on later. Connection passages drilled down to the cylinder ends for almost the full width of the cylinder would connect the milled port with the cylinder. This has the advantage that if the port face wears it can be replaced.
End of Rant.

[albert]

Hello,
I Have left these as holes-no problem. (at least a dozen cylinders)
Albert