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[tonyH]

Happy New Year All,
 
I'm trying to sort out the engines for a current project. I need 2 simple twin oscillators, preferably 'V' format to keep the height down. I've read a lot about Stuart and their 'V' twin castings seem to be the right size and price for a pal, who is an experienced steam engine machinist, along with the threads from 'Patternmaker' and others on this and other forums, to produce a decent setup.
 
So, on the assumption that they're available, does anyone have experience whether they're steam hungry and what sort of pressure seems to suit them?
 
Each one will be fed from it's own boiler and will drive a 2-2.5 inch prop. The hull is a coarse battleship shape and gross displacement will be about 14 kg - 30 lbs.
 
Thanks again.
 
TonyH
 
 

[southsteyne2]

Have a close look at pm research v twin oscillator it is a very good unit and not just for the price and you may only need one for a good scale speed

[kiwimodeller]

I too have had good service out of the P M Research V twin and a machined kit will cost less than the unmachined Stuart castings plus you will be able to have one up and running in a couple of hours. The Graham TVR1A would do the job too and although it is taller than the V twins there is not a lot in it. Personally, unless you are building a huge boat, I would use one steam engine and one good big boiler to drive both props. These engines will easily turn two 2.5" props. If you are going to use one engine per prop and cannot go bigger than 2.5" diameter then go for the Prop Shop steam props which have a lot of pitch. You need to load the engines down so they dont rev, otherwise if the engines rev too high you will consume too much steam. Give us some more info about the hull (length, beam, weight etc) and keep on asking questions. Cheers, Ian.

[tonyH]

Thanks for that but I'm trying to see what the options are for twin steam rather than the single engine/twin prop option I've used before.
Generally, the type of boat I've been building (Pre-dreadnought period) has been a pig to steer. It doesn't seem to matter whether it's a gunboat, a destroyer or a cruiser unless you cheat with an out-of-scale rudder add-on.
The current project is for the battleship Jaureguiberry which, at 1.1m and 30lbs is manageable for twin engines and would/could be a suitable workhorse. The twin props work out at just under 60mm and the engine speed/steam use could easily be kept down by gearing the drive up rather than the more common down.
The installation would call for the engines to be fitted on the angle. I.e. with one cylinder almost horizontal and the other almost vertical but this should not create a problem.
 
So...............what does the PMR engine work like in comparison to the ST? I've assumed a working pressure of 30-40psi but is this right for the PMR? Since I've got two funnels to fill, would twin boilers with a balancing pressure tube be the way to go?
 
Access would not be a problem, since the hull will, effectively, split at the waterline.
 
Cheers
 
Tony

[southsteyne2]

Hi Tony would need to know some more info on the beam and draught to determine the space needed and as for the pm twin it will work fine up to 35 psi one of my friends has one and loves it ,also you will save heaps to spend on other items
cheers
John

[kiwimodeller]

I can see what you are trying to achieve and it is certainly atainable but I think I would consider using one large boiler (if you have the room) rather than have the compication of two smaller boilers, two burners to adjust etc. It would be worth while getting hold of the K N Harris book and doing the calculations to work out how much steam each type of set up. Keep us updated. Cheers, Ian.

[tonyH]

Trouble is Ian that I'm taken with this photo, so it's a gut feeling rather than logic