Cylinder Gaskets

[Steambuff]

Hi all,
Has anyone got any thoughts on what gasket material to use if any, between loco cylinders and the frames.

Thanks Les (Steambuff)

[waggy]

Hi Les,
Never used a gasket in this position. My old mate Fred Barnes advised me not to as he had expeienced loose cylinders as the gasket material became work hardened/compressed. Never had a leak on my engines! Just ensure you add the material thickness to your cylinder block to keep things in line.

Waggy.

[Steambuff]

Hi Waggy,
My train of thought was that a gasket would prevent heat loss from the cylinder through the frames. unless of course the heat loss would be minimal.

Les

[SteveW]

Les,

Surely, if heat loss is your focus why not stand the cyinders off with a washer cylinder side on each bolt and go for an air gap.

This way it will be metal to metal all the way but with minimal actual contact.

[Steambuff]

Hi SteveW
That is a good point, I am probably not as qualified as a lot of the other members in this forum, but it just does not appear to make sense to me, mounting a heat source to another metalic object without some sort of insulating material in between. Obviusly I am probably looking at it from the wrong perspective. It would be interesting to know if the full size cylinders were bolted directly to the frames
Les(Steambuff)

[jackrae]

Look at it this way
The reaction forces from the piston on the cylinder head/end are putting the cylinder mounting studs into shear. Therefore you want as much friction as possible between cylinder and frame to distribute this shear force over the maximum area possible. The use of washers will provide an airgap but will also increase the shear forces on the studs (since the walls are no longer contributing) and also introducing some bending moment due to the small stand-off distance caused by the washer thickness.
Accept the slight heat conduction losses and take comfort that your cylinders wont be going walk-about.
jack

[chris vine]

Hi,

The heat losses from the cylinders to the chassis will be minimal compared to other losses in the cylinders.

Most of the energy in the steam is wasted in cylinders, if you get 10% cylinder efficiency you will be doing well I think. The trouble is that the fresh hot steam is in contact with cylinder walls and ports which have just been cooled by the old exhaust steam. In this way there is a skin of metal in the cylinders and ports which is always being heated and cooled, transferring heat from the live steam (which you pay for) to the exhaust steam (which no one pays you for). In addition any condensation which occurs in the cylinder drastically reduces the power produced and hence the efficiency because the steam loses pressure very rapidly. This is largely why superheating is so successful.

If you think about the general heat losses from the locomotive, you can tell where they are by the temperature of the various bits and how big they are. The chassis only gets a bit warm from the cylinders but the boiler is usually far to hot to touch and is large. Of course the worst heat loss is the chimney with 98% of your heat going up in smoke and steam. (IMLEC winners are often around 2% efficient!)

Hope that puts it in perspective!!!
Cheers
Chris.

[Steambuff]

Hi All,
Thanks for your contribution, I have taken on board your observations and comments, and will be mounting my cylinders directly to the frames.

Les(Steambuff)

[spurley]

Hi there

You asked about full sized practice, my experience of full sized locomotives is that cylinder blocks were bolted directly to the frames with no attempt at insulation. I think this is mainly to do with using the shear effect mentiond earlier, the larger the contact face the greater the friction will be and the risk of cylinders shifting in service is minimised. In general the blocks were attached using 'fitted bolts', these were precision sized bolts specifically made for each attachment point and the holes were reamed through to suit.

Cheers

Brian

[Steambuff]

Thanks for your reply Brian...I have decided that my cylinders will be bolted directly to the frames.


Les (Steambuff)

[waggy]

Les,
If you are concerned about leakage, a smear of Golden Hermatite or one of the Loctite jointing compounds wouldn't go amiss. Mine are dry, face to face, no problems. Some designs call for the smaller BA sizes to hold/ locate cylinders, I go for 2BA and use Allen cap screws, good steel and you can tighten them up!

Regards,

Dave.

[spurley]

As some of you may know, I am building a 3 1/2" Tich which is now running on air and the boiler build awaits! My cylinders are assembled without gaskets or sealant at present. I am glad to report there is no sign of leakage form the covers and only a tiny amount of air is getting past one or two of the steam chest bolts. I will be making and fitting gaskets for final assembly as I'm not sure what the effects of hot steam and expansion will be. I will possibly try the Gold Hermatite solution suggested by Waggy.

Still that problem is a way off yet!

Cheers

Brian

[jackrae]

we may be getting a little off the track here

Cylinders are bolted direct to the frames and the frame itself is not usually used as a pressure passage for steam on its way to the business end of things. Am I not correct in thinking that the steam lines pass through the frames via "big" holes and are coupled direct into the cylinders and/or steam chest.

In other words, apart from the original concern about transmission of conducted heat between cylinder and frame, there is no need to consider "steam tightness|" between cylinder and frame.

Jack

[spurley]

Jack

You are quite correct, steam is passed into the steam chests, in full sized practice, via the main steam pipes which either enter through the smoke box 'floor' and onto cast in flanges or through outside steampipes to dedicated flanges cast onto the block. In general outside steam pipes were related to piston valve outside cylinders. In model practice the steam pipes seem to be routed through the smokebox and back into the steam chest again, normally from within the frames.

I think Steambuff's original question was related to whether the cylinders should be insulated from the frames by gasket material and not as a seal for the steam path. The general concensus has been that the heat loss or any problems from conduction into the frames can be ignored and that the full sized practice of metal to metal contact is preferable.

Cheers

Brian