Annie,

The problem with my suggestion was that I looked at both stoves and heaters.

On the heaters I have seen, in particular the Taylor pot burner, there is a potentially dangerous regulator problem (run-away). A calibrated dose-pump, adjustable for setting of the heaters output, would solve that.

Alcohol stoves of the hot blue-flame type only need a low pressure from the overhead tank (much, much lower than in a Primus-style kerosene stove), but this low pressure must be constant. This constant pressure can more easily be achieved by a manual or electric pump. The setting of the burner’s output would still be done with a valve close to the burner, as described by David.

I admit; Jim Creighton’s link to stoves had me purchase a little stand-alone alcohol burner (it will arrive in some weeks). My thought is to try it and then modify it to feed it from an external tank. If the output of the burner is good, and it doesn’t crumble after a few months of use, then that could be an alternative to the Maxie.

Cheers, Arne

PS: Don’t talk yourself down, Annie. When I read your books and when I see the fine work you are doing on building SibLim, I bow to the dust. There is no way I could equal your standard, whether it be writing or boatbuilding. It is just that we focus on different things, and in the end, we tend to get quite good on what we have focused on for a while. Talent is 90% interest. These days, I am struggling with fitting a WC in a cramped compartment of my little Ingeborg. I wish I had your brains, right now!

David, I never looked inside the pumps we used in the lab, but the outer control was just a potentiometer, I'm not sure if there was other circuitry involved to control pump speed, but for our purposes I think a stable DC source and a potentiometer would be both simple and effective.

Arne, peristaltic pumps can have spring loaded rollers.  This in effect can take care of the pump should a safety valve be used.  With spring driven rollers, the rollers fail to totally compress the tube as the pressure rises and the pump effectively stops pumping at a relatively low pressure.  I have no idea how difficult it would be to find such a pump. The inexpensive pumps we are looking at on Ebay may be built to low enough tolerances that they squeeze the tubing lightly enough that they effectively stop pumping well before the burst of the tubing.  Also, fitting the pump with smaller diameter tubing could effectively do the same thing and yet still allow sufficient flow and pressure for a stove.  For a few dollars it would be an easy experiment to do.  Alternatively, you could also stop the pump the same way that some propane stoves have a gas solenoid that will shut off should the flame go out.

The burner could either be controlled by a mechanical valve or by the potentiometer on a pump.  For a cooking stove I suspect a mechanical valve would be best, for a heater maybe the potentiometer would work.

Other than using peristaltic pumps briefly in the lab I have no real experience with this, so take my comments accordingly.  You would also have to find tubing that is compatible with your fuel source and I suspect ethanol and diesel/kerosene would indeed need different hose types.

For my diesel stove the manual suggests using a diaphragm pump in this kind of a situation.  Here is a link to the Walbro pump that came with my boat but was not installed.  They can be set to appropriate pressures and will likely make any surveyor or insurance provider much happier.  The diaphragm is rated for E85, so maybe it would be OK with straight ethanol.

A bypass loop

I remember, on one of our radars used on Stavanger airport (where I used to work), the transformer oil in the high-voltage section of the transmitter was circulated via a cooler. The pump had no regulator. To limit the oilflow, a by-pass loop with an adjustable valve in it had been fitted. This easily let us reduce the pump’s net output.

I think this technique could be the way to regulate the net output of this peristaltic pump, as well, without putting strain on it. The alternative is to just have this bypass loop set at a constant rate and then use a valve close to the burner do the regulator work, as described by David. Probably better, that.

This setup could even have worked on the temperamental Taylor diesel heater (76D?) I had in Malena. That heater had an automatic shut-off in case the flame went out. The pump would keep on working, but thanks to the pressure-limiting bypass, no damage would be done.

Arne

PS: With that bypass loop fitted, one would need a pump valve to keep the fuel from draining back to the tank when shutting the pump off.

I think a peristaltic pump like David found is a good way to go.  I've used them in the lab a little bit and they can be made to deliver fluids at a reliable rate.  However, I never took one of those apart to see what they were using to drive the motor.  

The nice part of the peristaltic pump is that it is leak proof and maintenance free.  It just uses cams that squeeze the hose shut and push the fluid along.  Here is a link to another version on e-bay that shows this more clearly.  On some versions you can change the size of the tubing you are using to change the rate they pump at.

My first thought was to use an inexpensive DC-DC buck converter to drive the motor.  This would compensate for changes in the DC voltage of the boat and keep the motor speed constant.  However, I think there might be  a simpler route.

Here is a link to a unit that might be plug and play.   If I've read the fine print on the AC-wall wort correctly, this is actually a 12V unit.  If I were attempting the conversion I think I would start with something like this.  It would be worth checking its flow with the ships engine running and with the engine off.  If the extra voltage from the alternator made it change rate, then it might be necessary to add an inexpensive DC-DC converter.

Having said all that, we've had good luck with the regulator that came with our Dickinson Pacific stove and it doesn't require any electricity.

I wonder how that pump is regulated; just by adjusting the DC between 0 and 12V? Or should it be regulated with a pulse-length regulator?

The pump's capacity appears to be on the high side for this job. Only about 2% of its capacity is needed for working in a stove, it seems. I am unsure how it will react to a needle valve on the output to limit the flow.