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Solid fueled monotube controls.

Posted by Jim Holmgren 
Solid fueled monotube controls.
May 25, 2019 02:13PM

I wounder if these controls for a solid fueled monotube boiler would work satisfying?

I use a hinged plate that change the flow of the hot gases to the from the water tube to the atmosphere and that's controlled by the heat of the end of the water tube.

For controling the pressure I use the water pump, so if it's at the setpoint the water pump will not deliver water and if it's under it will pump water til the pressure are at the setpoint again...

Is this a good or bad way to controll the boiler?

I attach a picture of it, sorry for my bad paint skills...

Re: Solid fueled monotube controls.
May 28, 2019 03:08PM
Roger White uses something similar to control his steam powered, wood fueled Land Rover. It works well.

Re: Solid fueled monotube controls.
May 30, 2019 08:02PM
Hi Jim,
Would the feed pump be controlled by the engine? If so, you can control speed of the engine with this marvelous flap design. Yes, I think it is an excellent design provided its a tuned mono-tube. Think of the speed record model hydrofoil boats.

However, if using a motor controlled feed pump based on pressure, you'll need some flow control valve like the Richard Smith design.

Good luck...I think its great.

Re: Solid fueled monotube controls.
June 02, 2019 04:48PM
Thanks for the advice!

My plan was to run the feed-water pump from the engine and use a clutch and let the engine idle when it's not under load.
For controlling the water flow I will use a bypass valve or simply lift the check valve in the pump.

I'm working on the engine at moment, but my machining skills and workshop is not the best...
Re: Solid fueled monotube controls.
June 10, 2019 05:15AM
Hi Jim,
I got to thinking about feed water control. I don't recommend a clutch. However, I like that you will pump right on the engine. I would say just think by-pass and perhaps with a needle valve. This way you can adjust the flow to tune the generator tube. Also this way, you can control the speed of the engine with the fire. I think that's an ideal method for your situation.

Your damper concept should work well to control engine speed.

I attached the Richard Smith design if it helps...it explains the workings fairly well.

Kind regards,

Re: Solid fueled monotube controls.
June 10, 2019 08:15AM
The Richard Smith design is really the "compensator" designed by Warren Doble but built out of hardware fittings instead of castings.

Basically, it uses the principles behind the Newcomb (copied by White) flowmotor.

The compensator is used with feed pumps directly driven by the steam car's engine...you won't see it on pumps driven by auxiliary engines or electric motors.

It has one purpose, to limit the amount of water coming out of a pump. Direct drive steamers have a problem in that the feed pump that is perfectly adequate for cruising will often be unable to deliver sufficient water at low speed and long cutoff --- such as climbing a mountain, driving in a parade or navigating stop & go traffic. (We've all seen pictures of Stanleys parked on the sides of mountains with a rear wheel jacked up so that the engine can pump more water to the boiler) The obvious solution is to add a pump with two or three times the capacity so as to meet these difficult situations...the problem is that now you have way too much water at cruise speed.

The compensator reacts to water flow rate. At lower rates of flow it permits the full volume of water to pass. As you reach a setpoint, determined by spring pressure, it starts to dump part of the flow back to the day tank. As the flow increases, more is dumped back. People will tell you that it yields a constant flow but that's a bit of an overstatement --- the unit is spring controlled and you need more flow to increase the recirculation rate. That's a quibble but even Doble overstated the case, though I'm sure he was using shorthand rather than talking in absolute terms. (If it had been Abner, on the other hand....)

Note that the compensator is simply a peak flow limiter. It does not limit below a certain flow rate and does not regulate flow based on conditions such as temperature or pressure. In other words, it has defined limits to its range of applications.

It could be used as a flow regulator for boiler control by adjusting the spring tension, but this presupposes:

1. The pump is delivering more water than is currently needed
2. You have some way of measuring boiler conditions, applying these conditions to adjusting the needle valve and then have a secondary means of finer control (This basically brings us back to the flow motor patents. Honestly, I think the Newcomb are far superior to White for experimenters because they are build with provisions for bench adjustment … Owner inability to service the White flowmotor once the company quit supporting them is part of the reasons Whites are so scares relative to Stanleys, though produced in much greater volume).

Edited 2 time(s). Last edit at 06/10/2019 10:51AM by frustrated.

Re: Solid fueled monotube controls.
June 10, 2019 08:38AM
Attached find the patent for a solid fueled, monotube boiler designed by Abner Doble for the Sentinel Waggon Works in England. One worthwhile feature was the use of induced draft … the burner fan took a suction on the boiler housing rather than blowing air in. This was done on ships and stationary power plants so that you could open the door to add more fuel without having the flame blown into your face.

If anyone here can read French, it would be nice to know why the coils in the upper assembly are spaced so far away from the burner. My guess is that the bed of coals was giving off producer gas which was being combusted in the upper volume, but that's just a guess.


open | download - FR-05177.PDF (333.3 KB)
Re: Solid fueled monotube controls.
June 10, 2019 02:31PM
Ken - I had a read of it and as far as I can see the patent doesn't say anything about that.
Re: Solid fueled monotube controls.
June 10, 2019 02:45PM
Hi Mike,

The coils in the upper section certainly look like a Doble fire box...he usually had a large, empty volume surrounded by a single layer of tubes. If it isn't burning gasses up top, then I guess the flame itself is poking through the central helical coil. Eh, maybe I'm wrong again, but Abner usually tried a lot of variations on the same theme and took fresh starts only infrequently. It's easy to understand why he would do that, starting over would take a lot longer and no income would be arriving during that interval.
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All files from this thread

File Name File Size   Posted by Date  
MONOTUBE.PNG 57.8 KB open | download Jim Holmgren 05/25/2019 Read message
IMG_5046.PNG 118.1 KB open | download Brian McMorran 05/28/2019 Read message
Flow Control Valve.jpeg 387.5 KB open | download Rick.H 06/10/2019 Read message
1.png 38 KB open | download frustrated 06/10/2019 Read message
FR-05177.PDF 333.3 KB open | download frustrated 06/10/2019 Read message
FR-05177.png 119.3 KB open | download frustrated 06/10/2019 Read message