The Steamboating Forum

I use a whistle valve on mine, mounted on the receiver with a pipe to HP steam chest, just hit the lever and off it goes. BUT this only works when the engine is up to temp, if too cool hydrolocking is a possiblity! No it doesn't matter about backpressure on HP, you don't run it simpled just bump it over. rp

Hi,

ST 6A's can be notoriously difficult to start/reverse, especially if they have been well 'used'!

Their problems are numerous, mostly connected to the issue of being far too short legged and trying to fit full size reversing valve gear onto an engine deigned for fast running in generating roles.

Things to look out for:

- Check for excessive play in the valve gear linkage- if the play is too much the valve gear can be going up and down by 1/16" and the valves themselves aren't moving on the seats.

- Check the timing is correct- neither cylinder should 'lead' the other one, think of them as two separate engines linked on a common crankshaft- both should receive steam relative to it's respective crank position, NOT the other cylinder's position.

- If you haven't got drawings I can email you a picture of the valve and port dimensions- ST castings sometimes got the ports cast badly and it maybe there is an issue with valve sizing.


On a practical running note, whenever I've had the dubious pleasure of running 'one of those' 6A's it's advisable to practice manoeuvring without shutting steam off to the engine. Not talking about full throttle ahead/astern here, but certainly leaving the throttle open when going from ahead to astern can certainly help 95% of the time. Also, thorough warming through with the drains open before manoeuvring means you can set off with the drains only just open which can help the performance of the LP cylinder which can often see little effective pressure upon starting up and moving the valve gear with the HP cylinder on dead centre leaves you a sitting duck (a starting valve (see simpling above) would also help in this regard and allow hot high pressure steam to work on the LP cylinder).

Out of interest, what boiler working pressure are you working at?

Greg

Thanks Greg
I have the compatible Semple boiler with the engine. You have made some good observations on this engine. I guess you have used it also. I went out today to check the new eccentric pump. It did not work with enough pressure to put water in the boiler. Here again, i blame the maker for poor machine work, too loose tolerances. I will have to bush the cylinder or sleeve the piston to make it work.

Make sure there is no air in the system. Open the valve to bypass pumped water back to the hot well or wherever for enough time to blow any air out of the pipe between pump and boiler. Then your pump should be fine.

I have a hand squeeze bulb pump from an outboard motor gas can plumbed into the suction line to my feed water pump.

This does two things for me. First I can use it to flush any air out of the feed water pump. Second, if the filter on the input line to the feed water pump (which is before the bulb pump) starts to get plugged up, the bulb starts to collapse from the suction. It's a great diagnostic.

This is one of those stupid little items that no one told me about and has helped me get to the point where everything just runs now.