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[mrsgoggins]

Some very useful information has appeared in this thread but if I can make a small and perhaps obvious point about "slowing" the flow of flue gas through a boiler.
The gas velocity at any point is determined by the cross sectional area and the volume of flue gas. To slow the flue gas requires an increase in area or a reduction in the volume of the gas - neither of which are practical solutions, assuming the burner is operating cleanly without excess air.

[logoman]

The Saito in comparison is a 90 deg. V4 arrangement with single acting cylinders and having its cranks set at 180 deg. to each other.
Each crank has 2 cylinders (pair bank) but they are 90 deg apart from each other.

This has the effect of producing the worst-case (starting) situation where only 1 of the 4 cylinders is actually producing any useful Torque which at 30psi would only be approx 0.582 lb ins.
This would rise to 1.164 lb ins. after a further 90 deg rotation of the crank when the second cylinder of the pair bank (pair attached to each crank) reached TDC.
Some of the torque produced by the single cylinder would be used up in overcoming the drag of the remaining 3 cylinders until the second cylinder of the pair was in torque production, but there would still remain the drag of the remaining 2 cylinders.

AlexC.

thank you for posting this, I found it very interesting.
It also amazed me that this engine should self start, and be so easily reversed, on the smallest of pressures (see video below) I have 2 V4PRs and both operate this way.

http://www.youtube.com/watch?v=WWiYaQ_SnoQ

[flashtwo]

Hi,

I've been experimenting with a fan assisted flash boiler and have had a very good increase in performance.

See the "Flash steam plant control" thread for details.

Ian

[kiwimodeller]

I have done some more experimenting but was not able to borrow the laser thermometer yet so my findings are a bit subjective. One thing I did find by accident while taking the steam plant in and out to work on it was that I had an alignment problem which I accidently discovered by forgetting to tighten the plant down when reinstalling it and that immediately helped the engine to run freer. When I built this boat I was not aware of the advantage of double universals so only used a single one (there probably would not be room for a double one anyway) but I installed engine mounts and the prop shaft tube at the same time with a solid spacer replacing the U Joint. I do not understand what has altered but shimming the mounts has helped. I also tried the Primus type burner. It made more heat but did not seem to transfer any more heat to the water. The ceramic burner works well with wire mesh stuffed in the flue but the Primus type will not as it blows back so overall I think the ceramic burner is probably more user friendly. Boosting the pressure valve setting from 40 to 50psi helped the starting but the pressure still dropped away to where the engine would not restart, particularly in reverse.  Also decided that a new gas cannister helps as the gas pressure stays high for longer. So far there has been some improvements but still more to do including a heat transfer system (brass or copper strip?) to the gas cannister and perhaps an attempt at steam drying by running the steam pipe through the funnel as condensation does seem to be a factor in the starting problem. As a side question can anybody explain why this engine has a third exhaust pipe from the crankcase? There is a pipe from each of the piston valves which contribute most of the exhaust steam but it has a third pipe from the centre of the crankcase which the instructions tell you to feed in to a manifold with the others. Surely this will put back pressure in the case? Any ideas why it has this system? Cheers, Ian.

[logoman]

The crank case port is to vent steam that bypasses the pistons. The pistons are connected directly to the conrods, ie, no gland as you'd find in a typical layout. If there were no vent the crank case would fill with condensed water.

[kiwimodeller]

Thanks, I had figured that it was a vent although not having dismantled the engine I was not sure of the setup inside the crankcase. My only query was that the pressure in the two exhaust pipes might be higher than the pressure in the vent pipe meaning steam would feed back in to the crankcase. I tried running the vent pipe over the side separately and not much came out of it in the way of steam or water so at least I know not much is bypassing the pistons. I will hook it back up the way the factory reccomends as it has not caused any problem when run previously. Cheers, Ian.

[kiwimodeller]

Some more progress - I have been having some email conversations with Jerry from Clevedon Steam about his gauze (as against ceramic) burners amongst other things. He was very helpful and made several suggestions, some  of which I had already tried and some I had not. Among the most interesting was his suggestion for testing boiler output which was very simple to try -
"Fire the boiler and turn on the steam, disconnected from the engine. Ideally the boiler should make as much steam as is escaping."
I tried this several times and discovered that the standard burner setup, when tuned correctly, kept the pressure up highest for the longest time. The mesh in the funnel to slow down gas flow seemed to hurt things slightly and the Primus type burner did not hold the pressure up for long at all which really surprised me as I had always thought these put out more heat than a ceramic burner. Back to the lake on Sun for another test. Jerry also made an interesting comment when I asked about jet sizes -
"A No. 8 jet is the old No. 10 which I supply, along with a 5. No, No. 8 is the correct size and definitely not smaller". It seems that at some time there has been a change to the jet numbering system or to the flow rates" My burner currently has a 10 fitted but when I tried an 8 I could not notice any difference. Does anybody know anything about these changes, when they happened, what the differences are etc? I notice Maccsteam now only advertise two sizes on their website these days and do not state what number they are. Thanks, Ian. p s I will report on Clevedons gauze burner when it arrives. Cheers,