Gentlemen,

I have a few basic questions, primarily relating to Canadian National locomotives like 7470 at Conway Scenic, 89 in Strasbourg or 6325 at OCRR but likely pertain to many 'roads.

1. Why do Vanderbuilt tenders have 2 or 3 hatches for the water tank? Is the tank divided into 3 sections? If so, why?

2. All 3 of the above engines have a small valve on top of the piston valve cylinder. What is this valve used for? In pictures, it only seems to be open when the engine is at rest.

3. 7470 has, I believe, 2 valves on top of the boiler that don't seem to be connected to anything. I noticed one on a picture posted about a month ago on the interchange of a CNW 4-6-0. It is often, but not always, found near the safety valves. What is this used for?

4. I've noticed older tenders have a T shaped handle on each side in the cab which I believe, shuts off the water to the hoses connected to the engine. However, the T rests in a groove that has "steps" so it can be partially open. Why would you need it to be more than simply open or closed?

5. Some older locomotives with Stephenson valve gear were built with "inboard" piston valves whereby the cylinders are on a 45 degree angle (the CNW 4-6-0 mentioned above is like this). What is the reasoning behind it?

6. Finally, 6325 has a square "dome" directly in front of the cab on top of the boiler. What does it contain?

Thanks for any information you can provide.

> 1. Why do Vanderbuilt tenders have 2 or 3
> hatches for the water tank? Is the tank
> divided into 3 sections?
Three hatches makes it easier to line up with the tank spout when filling. Tank is not divided, but does have baffle plates.
> 2. All 3 of the above engines have a small
> valve on top of the piston valve cylinder.
> What is this valve used for? In pictures, it
> only seems to be open when the engine is at
> rest.
I believe you are looking at a "snifter valve" for "drifting" (coasting, it relieves backpressure)

> 3. 7470 has, I believe, 2 valves on top of
> the boiler that don't seem to be connected
> to anything. I noticed one on a picture
> posted about a month ago on the interchange
> of a CNW 4-6-0. It is often, but not always,
> found near the safety valves. What is this
> used for?
Often used when first filling boiler and warming it up to release any trapped air.
> 4. I've noticed older tenders have a T
> shaped handle on each side in the cab which
> I believe, shuts off the water to the hoses
> connected to the engine. However, the T
> rests in a groove that has "steps"
> so it can be partially open. Why would you
> need it to be more than simply open or
> closed?
Hmm, I never thought about that one, maybe different injectors work better with less flow??

S'
David D.

djdewey@cncnet.com

> 5. Some older locomotives with Stephenson
> valve gear were built with
> "inboard" piston valves whereby
> the cylinders are on a 45 degree angle (the
> CNW 4-6-0 mentioned above is like this).
> What is the reasoning behind it?

This is simply to bring the valve chests in closer to the frame as to make connection to the valve gear easier and to avoid moving parts from hanging off the side of the engine too far. Having steam chests 'inboard' was probably a maintenance headache although it did eliminate the need for an outside connection to the valve gear. You'll notice on engines with stephenson valve gear and slide valves, the angle between the piston rod and the valve rod is about the same as with piston valves, though its not as noticable because of the shape of the cylinders.

> 6. Finally, 6325 has a square
> "dome" directly in front of the
> cab on top of the boiler. What does it
> contain?

Probably the turret. Most of the main shutoff valves for things like injectors, blowers, air compressors, generators, are kept out of the cab. If you were to look up in the cab, you would probably notice a row of valves for these appliances with their handles leading into the box infront of the cab.

-Jay-


jmonty@vt.edu