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| Why are throttles in boilers? https://rypn.org/forums/viewtopic.php?f=1&t=48723 |
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| Author: | softwerkslex [ Sun May 04, 2025 8:57 am ] |
| Post subject: | Why are throttles in boilers? |
This question comes up, because so many of the modern park engines (and Cagney engines) are specifically built with throttles outside the boiler in the cab. Why did the majority of steam locomotives have their throttles in an otherwise difficult to maintain location, inside the boiler? |
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| Author: | John T [ Mon May 05, 2025 1:49 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
Having the throttle inside the boiler is more thermal efficient than outside. |
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| Author: | Patrick Fahey [ Mon May 05, 2025 1:59 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
Hi Steve You sort of answered your question with your last sentence, the throttle is easier to access being in the smokebox. and service.. The dome throttle presented its own problem just being in the steam dome.. In order to perform any maintenance on the throttle,, the engine had to be cooled down,,, for maintenance, and before either adjusting the throttle, or making repairs.. So it just made more sense to put the throttle, in a different location such as the smoke box,,, for easier access, and maintenance. Pat. |
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| Author: | BM765 [ Mon May 05, 2025 4:55 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
Biggest reason is to avoid water in the cylinders to the greatest extent possible. On a saturated engine this is accomplished by placing the throttle directly in the dome which is the source of the hottest and driest steam available. That steam is then routed through the heat of the boiler on the most direct route possible to the cylinders minimizing the opportunity to condense back to water. Park engines like you describe often have a manifold in the cab with a throttle valve directly connected. It's simpler mechanics, but now you are tapping wet steam. With good insulation, low operating pressures and engines built more for show than utility, this can work, but would be a poor setup when the goal is maximum performance. |
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| Author: | Tails [ Fri May 09, 2025 12:21 am ] |
| Post subject: | Re: Why are throttles in boilers? |
It should be noted that even on front end throttles, the engine still has to be cooled down and without steam to work on them. |
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| Author: | Dave [ Fri May 09, 2025 6:08 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
Yes to the thermal benefit on saturated steam. The biggest PITA I've encountered working on a dome throttle was reaching everything necessary to work on it since the dome lid was at the top and some of those rusty nuts are very far down in the dome....... European industrial locomotives I've seen had a dome bucket instead of lid which bolted on a flange closer to the top of the barrel, which would solve a lot of problems with that (not to mention wrenches found at the next retubing at the bottom of the barrel.) |
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| Author: | met1533 [ Sat May 10, 2025 6:46 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
I’m of the opinion that dome throttles are a punishment dating to the fall of man. |
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| Author: | Dick_Morris [ Sat May 10, 2025 7:15 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
I'd add a couple of other possible reasons for a cab throttle. Ease of construction in the steam connections and linkage and the ability to use an off-the-shelf valve both of which would reduce costs. |
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| Author: | QJdriver [ Mon May 12, 2025 2:12 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
Dave wrote: (not to mention wrenches found at the next retubing at the bottom of the barrel.) I thought everybody wired the wrenches to one of the dome studs... |
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| Author: | mldeets [ Mon May 12, 2025 7:38 pm ] |
| Post subject: | Re: Why are throttles in boilers? |
QJdriver wrote: Dave wrote: (not to mention wrenches found at the next retubing at the bottom of the barrel.) I thought everybody wired the wrenches to one of the dome studs... Not those who haven't dropped one yet................mld |
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