New paddler engines

[kiwimodeller]

Hi all, thought I would post some pictures of my latest idea for a paddler powerplant. The engines are two P & M Research (America) single cylinder double acting oscillators of 1/2" bore and 3/4" stroke. While not the highest quality they are quite well made and very reasonably priced. My idea was to take two of them and couple them at 90 degrees so I get a self starting twin with the drive to the paddlewheel shaft taken by chain and sprocket from between the engines. The reversing valve is from Dream Steam in the UK who do model rail bits and arrived here in NZ in less than a week which I thought was good service. It took a little bit of tweaking to get it to work at more pressure than it was designed for and I soldered the pipes in to the valve body rather than use the O rings supplied. The pictures show the engines mounted vertically on my "one plate fits every motor" base plate so I can try the set up in my Waimarie side wheeler but the idea is to later put them in the back of a sternwheeler, one engine on each side lying horizontally with chain drive to a cross shaft and then rods and eccentrics to the wheel. The front eccentrics could be hidden behind dummy engines on the deck so the drive setup looks reasonably original. I have had one engine running for some time but just assembled the other. It leaked rather badly from the valve face at first but after adjusting things as per instructions and running it for an hour on air it seems better. I will test it on steam after work tomorrow and hopefully sail it on Sunday although the drought has meant that our lake is very low which makes launching an 80" paddler a bit difficult. Anybody want to come and visit and bring over some melted snow? Cheers, Ian.

[miniengine]

PM Research has a double kit that is 2 Number 3 engines side by side.  Just info.

[kiwimodeller]

Thanks for that, I just happened to have these as I brought them in to the country for someone else who then reneged on the deal. I had them going on steam tonight but there are still some problems to sort out. At the moment they do not want to run on any less than about 60lbs pressure but if I use that much then they leak a lot of steam out of the valve face. Just need a bit of sorting I hope. Cheers, Ian.

[kvom]

Being new they likely need running in.  I was wondering what your coupling is and how accurately it's lined up.  Any chance there's some binding/friction due to the coupling?  If you run them uncoupled a difference in steam pressure needed would point that way.

[kiwimodeller]

They are solid coupled with a piece of rod I bored 1/4" right through in the lathe. It made a bit of a difference as to how easily they turned over when I eased to mounting holes a little. I had thought they might be binding and will try them uncoupled. One engine has had about 5 hours running on air and the other about 1 & 1/2 hours but this was their first run on steam and it is obvious that the valve faces are not fully lapped yet but I think the main problem is that the system for holding the cylinders to the port face is not designed to withstand 60psi. They do not use a spring as most oscillators do, just a Belville wavy washer to maintain tension. The other problem might be gearing. I have them connected with chain and sprocket at a ratio of 3.375 to 1 which is the same as I use with the big slide valve engine that is usually in the boat and I think the load is too much for oscillators. I will make sure they are turning as freely as I can get them to, might even put in a flexible coupling, and I will lower the gearing ratio and see how that goes. Thanks for the suggestions. Cheers, Ian.

[kvom]

Bellville washers are quite adjustable to get the tension you need.  You can add additional washers and/or reverse them to adjust to suit.

An oscillator like that shouldn't need 60PSI, so I wonder if the bore and/or piston are not well mated, in addition to possible friction in the valve faces.  How easily do they turn by hand?

It mighty also be useful to remove the end cover and verify that the piston travel is correct within the cylinder.

[kiwimodeller]

I assembled the engines from kits and set the piston heights as per the instructions with a dial gauge and also checked the bottom position so I know they are correct. I realise they should not need so much pressure so I will be trying them individually when I get a moment but I still suspect that the load is too high and so I will lower the gear ratio. Cheers, Ian.