Notes on the Wetz Boiler Control

An innocent person asked me to make a small monotube boiler for his Locomobile type vehicle that used John Wetz’s analogue monotube boiler control. This boiler was designed to fit within the existing space and thus the gas flow is a little different. We put the Beckett burner with a 2 ½ gph kerosene burner at the bottom so that it would fit in the car better and put the Wetz controller ring at the top for easy adjustments while learning.

We got some smoking and soot build up and think that it is because of too much restriction to air flow. Also the squirrel cage fan on the Beckett does not put out enough pressure. Also the combustion chamber is on the small side for good and complete combustion. We are fixing that.

		Because the Wetz controller is at the top the combustion gases go up through the center and back down through the coils and out the sides for exhaust. It is important for the two cross tubes that do the expanding and contracting to control the microswitches to be in as much of the fire as possible. The reason is because if there is a water pump failure, then both tubes heat up fast and, working together, they turn off the burner from over-temperature.

Our first run showed almost no expansion and contraction and thus almost no movement of the control arm. Analysis showed that we had not designed the superheater coil properly and it was all jammed up against the sides as well as there was no easy movement.

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Therefore we cut away the entire outside ring of tubing and then made sure that the control output steam tube was relatively free to move, having only to work against the spring of an open coiled tube. It is much easier to understand this when seeing it in person. We will explain more and in much more detail when we get it to work.
		Combustion Chamber