Throttle inspiration?

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Builder01
Posts: 726
Joined: Mon May 18, 2015 5:26 am
Location: Erie, PA

Re: Throttle inspiration?

Post by Builder01 »

Thanks for the photo!

Brass should not be used for boiler fittings. If you have lots of bronze, use that! Stainless, in this case, would actually be better, as the threaded end would wear a bit better than bronze and the other end would make a perfectly fine throttle valve. At this smallish diameter, it would be much tougher than bronze, or, even brass. (Don't use brass.)

I am dubious of the design that the flat part of the valve is the part that actually throttles the steam. Screw down throttles usually have a tapered pieced that fits against a straight hole. Which actually, give you a "needle valve" sort of throttling effect. The flat valve against the flat seat give you little control of the throttle as the flat valve is drawn away from the seat.

If the valve is guided by the thread and the packing, what is the function of the tapered end? Do you have a drawing of the original part?

How is the handle attached to the throttle valve rod, there is no "squared" end?

David
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DianneB
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Joined: Tue Aug 21, 2012 3:05 pm
Location: Manitoba, Canada

Re: Throttle inspiration?

Post by DianneB »

Builder01 wrote: Mon May 28, 2018 9:24 pmBrass should not be used for boiler fittings. If you have lots of bronze, use that!
]

Oops! I remembered wrong. Bronze I have.
I am dubious of the design that the flat part of the valve is the part that actually throttles the steam.
It certainly does. I was rather surprised myself! Apparently that was the Little Engines design in 1960. The tapered end on the stem is much smaller than the steam passage and it is the flat rim that seals against the face of the base.
Do you have a drawing of the original part?
No.
How is the handle attached to the throttle valve rod, there is no "squared" end?
No, there is no square end. There is a small block with a setscrew that slips onto the stem and the handle screws into that.

It wasn't my design - it was the original design of the Little Engines 4-4-0 American. It might not follow "modern design practices but the fact that has been running for nearly 60 years says something.
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Builder01
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Joined: Mon May 18, 2015 5:26 am
Location: Erie, PA

Re: Throttle inspiration?

Post by Builder01 »

It wasn't my design - it was the original design of the Little Engines 4-4-0 American. It might not follow "modern design practices but the fact that has been running for nearly 60 years says something.
I understand it is not your design, without the drawing, there is no way to know if it was made correctly. If the small tapered end does not actually touch anything, I wonder what the purpose of it is?

Many things can work for many years and not be right, or, optimal. Locomotives will run even when the valves are poorly timed, but, it's not right. How many of the 60 sixty years has the throttle valve been leaking? Something is clearly not right. Considering the design, or, at least the way it was made, it is no wonder it leaks a bit. I hope you are able to get it corrected. I'm sure you will sort it out.

David
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