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Modulating steam automatic

Posted by Kelly 
Modulating steam automatic
August 05, 2015 06:48AM
Hi Mike,

You wrote "The steam automatic, unlike Stanley's version is either on or off rather than modulating as the Stanley's does in practice. That is a significant improvement which makes the burner fire or not fire instead of half firing."

I'm curious about what you've found here. In my driving, it has seemed like the modulation behavior is in a fairly transitional range, and it doesn't take too many feet of movement for the pressure to drop low enough that the automatic is open all the way. In fact I've kind of liked the "soft" opening of that valve, as it seems to reduce the likelihood of a blast of fuel that doesn't light.

This may all be because I haven't driven cars in the state that you brought your Model H to... Just trying to understand better from your experience.


Edited 1 time(s). Last edit at 08/06/2015 11:21AM by Kelly.
Re: Modulating throttle
August 05, 2015 12:09PM
That is a good point you brought up, the fire coming on softly in place of some blast at full pressure.
The White system does the same thing. The action of the flowmotor produces a soft start for the fire. Starting at zero and gently coming up to operating pressure.
Dobles with the original carburetor burner come on softly, the ones converted to pressure atomizing quite often either give a puff and don't light, resulting in a delayed backfire, or come on at full intensity.
Re: Modulating throttle
August 05, 2015 02:18PM
Ken, Jim,

The Stanley modulating happens when the boiler pressure is very close to the operating pressure say - within 10psi when the steam automatic valve is just starting to open. When pulling away from standstill or going up hill or fast on the level this is not much of a problem as the steam demand is enough to quickly drop the pressure and get the fire going but if the car is just pootling along, in traffic, then the automatic just lets a dribble through which may not light or will only partly burn. The same can happen in the converse where the fuel is just about to be shut off. I adopted the trick of turning the burner off in those conditions and manually starting it again when the pressure had dropped enough (by 25-50psi) that the steam automatic would be fully open when a relight was needed.

I’ve said this before but it bears repeating - there are a couple of tricks to stop the burner from lighting with a bang. One is to use a slightly larger ball and seat in the steam automatic so the response of the automatic to steam pressure is over a smaller pressure range and so modulates less often. The other is to use a skinny pipe to connect the automatic to the burner so that there is no great slug of liquid fuel to rush into the vaporiser the instant the steam automatic opens - I ran with a ¼ inch od pipe with 4 copper wires inside just to keep this volume of fuel down. I ran experimentally with a 1/8 pipe with bore of 0.080” and the burner ran quite normally - in practice I used the stuffed ¼ pipe as it was physically stronger. The burner of the Model H was very docile when lighting - never going pop!

The Model T special with a normal Stanley vaporiser pressurized by pumped fuel with a modern pressure switch works really well and is definately either on or off - I guess, but don't know, that it has a smallish pipe to the vaporiser. I t seems very docile and of course has the advantage the the fire is always going at full power at any time when needed.


Edited 1 time(s). Last edit at 08/05/2015 03:22PM by Mike Clark.
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