Steam Cylinder Questions.

[Arnak]

Hi Folks,

I am fabricating the stem cylinders for my 3.5" Virginia out of Cast Iron however I noticed on the plans that the cylinders are shown with a 3/32" curved waist between the two ends.

Is this just decorative or to save material when casting? ???

I ask as most of the pictures I have seen of the finished Virginia appear to show solid cylinders without a waist, although could that be a metal cover to make them look better?

The second question is which do I choose for the steam chest, Cast Iron or Steel? :-\

Thanks for any advice.

Arnak

 

[Groomengineering]

Hi Arnak.

Most cylinders of this type were waisted then wrapped in insulating material and covered with metal lagging. On the full sized engines it helped keep the cylinder hot so the steam wouldn't condense. Not really necessary on a model, but most cast the cylinders that way and lag them for appearance sake.

Either cast or steel would work for the chest.

Cheers

Jeff

 

[Arnak]

Hi Jeff,

Great! Thanks for the reply.

It will be easier not to mill a waist in the cylinder then cover it with sheet. ;D

I can just cover with sheet anyway for appearance sake, then polish it...

Arnak

 

[steamer]

Yes you can avoid the waist....but it will like the insulation.

Dave

 

[Arnak]

Hi Dave,

OK, a waist it is then. :

What material do you suggest for the insulation?

Thanks,

Martin

 

[steamer]

Unless your going to run superheat, I think you will do fine with fiberglass....which is ....glass

What pressure are you running with it?

If you feel more comfortable with the high temperature insulation from various suppliers, thats fine...but at 300F...it's not that hot.

In the firebox is another story....

Air is fine too by the way..ie NOTHING.....as it won't conduct heat worth a damn, and within a small annulus, won't convect much either

Dave

 

[Arnak]

Hi Dave,

The answers are, I am not that far forward yet but I will assume that I will include a superheater.

So I would be best to go with a high temperature insulation or as you suggest just air. ;D

Thanks again for the advice.

Martin

 

[kvom]

It ia very doubtful that insulation on the cylinder will have any appreciable effect, and I have not seen any 7.5" gauge locos with insulated cylinders. In fact, boiler insulation is pretty rare. I know some people have lagged their boilers with lead to improve tractive weight.

I made my steam chests of CI to match the cylinders on my build, but steel would be fine too.

 

[steamer]

The LARGEST loss in small steam engines is condensation loss through cylinder liners.....either insulatinjg the cylinder and cylinder covers or running superheat is the only way to improve on that.

Dave

 

[Arnak]

Hi Guys,

Thanks for the advice. ;D

I think that given what you have both said that it would be a good idea to lag the cylinders and use a superheater.

Avoiding loosing steam is vital in this build as there is a problem with the small boiler model in that it is prone to run out of steam early, I believe that is why that LBSC designed the large boiler version.

That version is better in that regard but it does loose the period Western profile.

In addition lagging the boiler with lead would be useful on this model as I have heard that the Virginia is prone to slippage and some owners have added more weight under the firebox to improve traction.

Martin

 

[Jasonb]

Lead lagging is not going to do any favours to your heat loss. Get soem Kaowool and baking foil under the boiler cladding.

If you need to add balast then bolt on a big lump low down.

Insulating the cylinders will also mean you don't need the cyl drains open as long to expell condensate and waste steam at the same time.



J

 

[Arnak]

Hi Jason,

Thanks for the advice, I'll take that and follow it. ;D

It will be a long time before I need to worry regarding the tractive effort but I am getting there very slowly. :

Martin