Once and again. Controlling a monotube. Pump-regulator.

Hi, steam fans!

Want to propose some method of controlling monotube boiler. This metrod follows from R. J. Smith control system.
One mechanic, fan of steam, once made a water pump for his model monotube steam generator which pumping action is produced not by the force of an eccentric directly as it ordinary doing but with the force of calibrated spring. Returning of the plunger is made by the action of eccentric. Force of the spring calibrated correspondingly actual pressure in the boiler. He set a needle valve after the pump to adjust water flow properly. When I saw the picture of the pump I thought – oh, la la, it is a halve of a monotube control system! Three devises of R. Smith control in the one pump. Spring automatically would throw exact amount of water accordingly with a pressure in the steam generator. Needle valve after the pump is doing function of a needle valve of Smith’s water flow regulator. No return of water through bypass, no useless pump work done. Add here a steam automatic and thermostat to trim the fuel flow and here it is - control system for monotube boiler. Here on the picture shown the idea and design of the pump can be altered. The spring could be set under eccentric and so on... What would you say, gentlemen?
Serge

Serge,


Wow....that’s pretty ingenious! The pump has a variable stroke that is determined by pressure....very cool. I would make the spring tension adjustable from outside the pump somehow, like with a sealed, threaded collar that pushes down on the spring. That way the set pressure can be tuned even further...along with the needle valve. It’s simple enough that I might change my pump design to this type, especially sense I plan on running it off an eccentric as well.

Jamison

Thank You for input, Jamison

It would be interesting to see how it will work on Your mini-bike. In the model it worked fine. It is possible to go even further and try to achieve control of the engine by changing the pressure by adjusting "pumping spring" by another eccentrick or lever along the ride. It would encrease efficiency of the system by lowering need of throttling. Though the need of throttle is remain for prompt response, and then changing of the pressure in the boiler comes to play...

Serge

Could the adjustment be made by raising or lowering the pivot of the rocker arm?

Mike



Edited 1 time(s). Last edit at 03/23/2018 04:49AM by Mike Clark.

Нi, Mike

Why not? I think it is possible. If You mean my drawing, it is not the best arrangement for tuning the spring. It is only idea, real pump was made another way, without roker arm. For this set, I think better to put spring under the eccentric and adjust it from the beneath point by screw or eccentric or whatever...

Serge

Hey Serge,

Pump plunger delivery stroke by spring, with link/eccentric intake stroke and spring controlling delivery pressure/stroke/volume, is an old and intriguing idea. Homans' book and others give details. Cam-driven IC-engine diaphragm [/mechanical] fuel pumps use same principle very successfully, though at about 7 psig rather than the 140+ psig in steam car fuel systems.

Peter

Peter Brow Wrote:
-------------------------------------------------------

> ........ though at about 7 psig rather than
> the 140+ psig in steam car fuel systems.
>
> Peter


Hi Peter,

Such pump already tested at 70 psi, though at model scale and no longer than may be one hour. Dont see the difficulty to make the spring three - five times stronger. Anyway numerical value of force on the eccentric will be the same but less pumping work done due to reduction exessive pumping and no bypassing. And such pump will never blow off...

Serge

Hi Serge,
A lot of comments about this great concept. I like it too!

So Jamison's idea to add a needle adjustment valve is also very good!

Just a thought...make it closed loop. In other words, tie the boiler pressure to the spring using a piston or other device. I've attached the Richard Smith Flow Control device concept/sketch. Maybe that will bring out some ideas...combine the two.

Kind regards,
Rick

Hi Rick,

Thank You for posting. It was this Your picture and toggle-bypass valve on the system diagram on that site about R.J.Smith bicycle that made me to think that spring pump can serve instead of both. When I saw that scetch of the pump I immediately remember Your sketch and something sparked in my head. Though on the diagram toggle bypass shown wrong place - before Richard Smith Flow Control device. It should (and in reality it is!) be placed after Smith's water flow regulator.

Serge

Hi Serge,
My apologies...your right! After some thought simulation, this spring pump would replace the flow control valve. Application is on a mono-tube steam generator.

My thoughts were crossed as if the pump would be applied to a pressure vessel type boiler, i.e. an Ofeldt. I do have intention to create what is called a Check Valve Ofeldt (CVO) boiler. The spring pump would be definitely applicable in this design. In essence, the CVO would be a multi-pass steam generator as apposed to a mono-tube (I think I attaché a sketch in a previous post).

Again, a wonderful idea!

Cheers,
Rick

Hi guys,

Attached find a feed pump for an Edward Newcomb patent issued in 1902. This was pretty advanced stuff as it had a complete flowmotor system years before White. Actually, General Electric tried to cheat Newcomb out of the design and Rollin White seems to have swooped in and take the basic concepts after he was pretty much beaten up in court trying to defend his invention.

Newcomb had signed up one manufacturer to use his design before GE filed a bogus suit against him.

Horseless Age reported that the boiler was fast steaming and very stable....which was amazing at the time but kind of expected given its flow motor.

As you can see from the picture, he had a piston on one end of the cylinder driven by a crank or eccentric and, on the other end, a spring loaded piston. As the cylinder pressure approaches boiler pressure, the spring loaded piston moves back and forth, limiting pump output until it finally ceases altogether.

The patent(s) are too big to upload and Google Patent is no longer worth crap ... it was once good but you can no longer get it to find the correct patent even with the inventors name, full title and patent date.

You can go to pat2pdf.org and download the patents by entering the numbers 0704907 and 0704908.

Note that the spring loaded piston is much larger in diameter than the pumping piston. This is done so that the relief stroke is far smaller than the pumping stroke. By doing so, the spring motion is quite tiny and the regulation pressure is relatively unaffected by spring compression.

Ken



Edited 2 time(s). Last edit at 03/28/2018 01:34PM by frustrated.

Hi, Ken

Yes, this is a similar way to control water flow and I considered it either, but in the case of a spring pump I proposed, power expenses seem to be less.

Serge

Let me catch up to this subject a bit

How is controlling pressure from the pump, controlling the water level in the monotube coil? Seems there would be two ways to have low pressure in the coil, flooded and empty (or unfired). I get that it pumps somewhere along the way to running dry, but what about when it is flooded?

Variable lift off one 2D cam lobe, she'd be a clacker.

-Ron

Ron,

My understanding is that it doesn’t control water level per se....but controls the flow rate of feed water, based on the boiler pressure. If the tubing is depleted of water, than the pump will work at full capacity due to no or low pressure. As the tubing fills with water....assuming the fire is going....the pressure rises and the back pressure starts slowing down the flow, until the calibrated force of the spring is completely overcome, then it ceases to pump and the plunger is no longer able to downstroke. Let’s say the monotube is completely flooded with water....and / or its unfired ....then the pump alone will cause the pressure to rise and essentially turn itself off....once the spring pressure is overcome.

The way the pump works mechanically is the eccentric / cam just returns the pump on the up stroke. The spring does all the actual pumping on the down stroke. The more pressure it has to pump against the more the spring compresses, and that is what varies the lift....and the flow....not the cam or rocker arm. The eccentric / cam / rocker arm is always moving the same...even if the pressure is at the set level, the spring is compressed and the plunger is not moving because of it.

From my understanding....it’s not an exact way to control feed water rate, but if properly calibrated, should work fairly well to keep it under control. It should be used in conjunction with a temperature and / or pressure control of the fire, and I would assume some level of cockpit tweaking of a bypass valve or flow valve would be needed as it is running.

Jamison

Hi, Ron

Thank You for the question. Control system is supposingly works the following way.-- (We're all know that monotube is tricky thing.) When You put into the working monotube coil little more water than needs current moment, pressure goes up, though the steam get lower temperature. In the case of the spring pump it is impossible because raise of pressure does not permit more water flow into the coil automatically. And reversely if You have more steam demand, pressure goes down and this pump automatically put there more water. Then termostat seeing lowering temperature adds the fuel. It seems enough to have only two devices - this pump and termostat but termostat is a slow animal so it is supposingly better have in addition pressurestat which responce is quicker. And thermostat only keeps the temperature of steam. Then about overflooding. The pump has needle valve on it's delivery side and it should does not permit too much water flow to overcome burner max firing rate. I dont see why it wouldn't work.

Serge

Serge,

Lol...Looks like we posted at the same time, saying essentially the same thing ....although I think your explanation gets more to the point than mine does.

Jamison

Jamison,

Your explanation is absolutely correct. I think Ron appreciated it.

Serge

Jamison and Serge,

Thank you for the replies.

I was thinking about this configuration under all circumstances and as I wrote above, I see how the pump with built in pressure regulator would have low water taken care of. In the case of a flooded coil with or without fire, and generator under demand with throttle open, this would create low pressure in the coil and usurp water for steam going to the engine. What is the control in that situation?

-Ron

Ron

It is a question I"ve thought alot before and think this situation You described can arise only in the case of refusal of steam automatic or artificial shut the fuel off and if it is so You should close throttle valve too. If all working properly, in the case of low pressure steam automatic should open full fire and max delivery of the pump tuned the way it can not flood the coil as all water turns into steam.

Serge

All files from this thread

File Name	File Size		Posted by	Date
Spring pump.png	327.5 KB	open | download	russt	03/22/2018	Read message
Image (11).jpg	387.5 KB	open | download	Rick.H	03/27/2018	Read message
Feed Pump Newcomb patent 704907.png	458.1 KB	open | download	frustrated	03/28/2018	Read message