Hi,
Well, as you can see from the "Steam Jet Engine" thread, "Vital Byte" has been on the back burner for a few months, but it is now being put through its paces in the test tank to flush out the expected software bugs.
V.B. now has a new controller (the AE-35 unit), a professional 5inch prop (Propshop) and a 200 sq.inch monotube coil.
Having sorted out a few software bugs, I had trouble with some erratic behaviour akin to that caused by steam induced static electricity that I had in the very early days. Well, all effort was made to earth everything down, but the problems persisted. I finally traced it down to the servos that, when making large movements, were causing the supply volts to drop on the controller. The offending servos were moved to an existing servo power board that is supplied directly from the battery, thus stopping the interference on the AE-35.
Having finally got the controller sorted out, I then concentrated on the overall performance of the boiler and engine. I had noticed a lot of soot on the boiler coil indicative of poor combustion, also, when running with the gas valve open above 50%, there was the sound of an unstable burner.
With the experience gained on steam nozzles with the steam jet engine, I've just made and tested ( the sort of thing one does on the hottest day of the year) a Induced Draught nozzle that tees-off some steam from the coil just before the boiler exit. The steam is directed up the stack and greatly improves the draught resulting in a great increase in boiler pressure and engine RPM. The engine speed has now increased from about 480RPM to higher than 700RPM (ahead and astern!), I say higher because the RPM code is currently limited to 700, but will be changed in the near future.
The substantial increase in RPM has been achieved inspite of using some steam for the Induced Draught nozzle and the beauty of the system is the higher the steam pressure the more draught is created.
As you can imagine 700RPM with a 5inch prop there is a lot of water sloshing around.
I suppose this method of induced draught can also be applied to those Mayhemers with conventional boilers.
Ian.