Steam Dome Throttle

[NP317]

I bet the throttle rod runs forward internally from the backhead, and actuates the throttle via a 90 degree rocker and vertical rod.
Just guessin'.
~RN

[FLSTEAM]

Good guess. Just thinkin...……..JB

[FLSTEAM]

Here is a view of the backhead. Should reveal the secret lever to the dome.

JB

[daves1459]

Thank you to all of you for your ideas and insights. I believe my steam dome and throttle rod is a bit different that most as the turret pipe enters the rear of the dome and the throttle rod goes down through the center of the turret pipe as shown in the attached photo. The dry pipe enters the dome on the boiler center line towards the front of the dome inside diameter into a horizontal plate with threaded holes. I think I can fit a ball valve eccentric to the center line mounted on a short manifold that adapts to the horizontal plate with the lever on the center line so to be a straight connection to the throttle rod.

In the event I can't fit a ball valve I may be forced back to a flat sliding plate type of throttle. In that regard I have heard of live steamers using a Teflon block trapped in a recess of the sliding plate as a valve. Anyone have experience with that type of set up?

Dave

[765nkp]

I have a 1" Atlantic with a Teflon sliding disc. The engine is somewhere around 45 yrs old. No problems yet.

Tim

[John_S]

Check out how I handled the ball valve and linkage here:
http://www.chaski.org/homemachinist/vie ... 35#p338835

I've built two this way and they work great. Used an off the shelf 3/8 ball valve from Ace Hardware and all stainless materials for the rod and lever.

[Fender]

Check out how I handled the ball valve and linkage here:
http://www.chaski.org/homemachinist/vie ... 35#p338835

I've built two this way and they work great. Used an off the shelf 3/8 ball valve from Ace Hardware and all stainless materials for the rod and lever.

A very timely post! I intend to fully plagiarize this design for the throttle on a boiler I am currently building.

[daves1459]

Check out how I handled the ball valve and linkage here:
http://www.chaski.org/homemachinist/vie ... 35#p338835

I've built two this way and they work great. Used an off the shelf 3/8 ball valve from Ace Hardware and all stainless materials for the rod and lever.

Hmmm, that has possibilities. I'll look into similar ball valve installation into my steam dome.

Regarding the ball valve itself: How do you find the operating characteristics? Can you get a smooth launch without a jump forward or instant speed or easy wheel slip? How about low speed regulation? Can you accelerate gradually and easily modulate low speed?

Dave

[Greg_Lewis]

Regarding the ball valve itself: How do you find the operating characteristics? Can you get a smooth launch without a jump forward or instant speed or easy wheel slip? How about low speed regulation? Can you accelerate gradually and easily modulate low speed?

Dave

The late Cal Tinkham had one in his engine and it was OK. In a perfect world it would have been nice to have something with a more gradual opening, but it was OK and anything else would be more work. I think part of the equation is the leverage factor on the linkage. If you work it out so the throttle lever has to move quite a bit to get a small movement on the ball in the valve, you'd be fine.

[cbrew]

Check out how I handled the ball valve and linkage here:
http://www.chaski.org/homemachinist/vie ... 35#p338835

I've built two this way and they work great. Used an off the shelf 3/8 ball valve from Ace Hardware and all stainless materials for the rod and lever.

Hmmm, that has possibilities. I'll look into similar ball valve installation into my steam dome.

Regarding the ball valve itself: How do you find the operating characteristics? Can you get a smooth launch without a jump forward or instant speed or easy wheel slip? How about low speed regulation? Can you accelerate gradually and easily modulate low speed?

Dave

the best way to manage slow speed and heavy starts is leverage in the linkage. i set mine up with "full" throttle is only opening the valve a quarter turn. still more then enough steam and great control

[Soot n' Cinders]

the best way to manage slow speed and heavy starts is leverage in the linkage. i set mine up with "full" throttle is only opening the valve a quarter turn. still more then enough steam and great control

This is an interesting approach. Most ball valves really don’t offer much increase in flow after about half way open but this takes care of that. If there’s not enough flow from that, could always increase the size of the valve until you get the behavior you want from it.

[jkimberln]

If you want a rotating throttle valve rod instead of a pull type rod, then use a right angle ball valve. 4847K12 from McMaster is the one I used. It operates like any other ball valve, of course, but one port goes up into the dome, the other forward through the front tube sheet. A little modification of the handle area to attach a stainless actuating rod will be needed to go back through the backhead sealing gland.