New R/C marine steam engine from PM - RC Groups
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Mar 13, 2007, 01:06 AM
floating and flying
misfitsailor's Avatar
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New R/C marine steam engine from PM

At a model engineering expo a year and a half ago, I talked to the P.M. Research folks. They said that they were about to release a new marine steam engine. I told them to contact me as soon as they did. I bugged them every few months, and was surprised when a few weeks back I got a phone call asking me if I was still interested in getting the new engine. It was finally ready! And boy was it worth the wait.

This engine is only available pre-machined, but not assembled. It is called the #8 Twin Oscillating Marine Engine, and is made of bronze, brass, stainless steel, and aluminum. The cylinders seem to have a hard annodized finish and are sheathed in brass covers. This engine is self-starting and reversing. Nice features include 2 teflon piston rings per piston, o-rings and gland nuts to seal the piston rods, all bearings are separate parts.

If assembling one of these I have the following suggestions for success. After pressing in the shaft bearings, fit the crankshaft and perfect the fit by "motoring" the shaft on a drill. (on my engine the bearings needed reaming + motoring). After assembling the cylinders (minus the heads) install one on the engine and make all needed adjustments until you can turn the engine smoothly, the take it off and put the other cylinder on by itself and do the same. By doing these steps, you get rid of any binding and tightness as you go and will have a free spinning engine from the start.

I ran this engine first on air, and then on steam. It ran great from the very first application of pressure. It is a very quiet fellow, and has lots of power. Vibration isn't that bad even at high rpm. The control valve requires very little force to operate. I think this will be a good reliable engine for our boats. One thing in it's favor is the simplicity, very few moving parts. Another plus is the price: a mere $159.00 US.
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Mar 13, 2007, 01:10 AM
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willhaney's Avatar
Wow, that is a work of art.
Mar 13, 2007, 01:17 AM
Grumpa Tom
Kmot's Avatar
It's beautiful, mfs! What are the outside dimensions? And how about some video of it running?
Mar 13, 2007, 07:46 AM
Lipoly Killer
Frank Hurd's Avatar


Talk about an answer to my prayers!
Mar 13, 2007, 08:11 AM
"day ain't over yet-"
der kapitan's Avatar
Originally Posted by Frank Hurd
Talk about an answer to my prayers!
Yeah, Frank, and the price won't kill you---.
Mar 13, 2007, 10:09 AM
Damp and Dizzy member
Brooks's Avatar
I see you have a Graham TVR1a in the background. How does it compare to the PM engine, and, since I have the Graham (newly made), what are your suggestions (building, operation, etc) for Graham's engine? Boiler ideas too would be welcome, thanks.
Mar 13, 2007, 11:35 AM
Registered User
P_J_Glor's Avatar
Does it have reverse? What boiler does it use, and how would you order it?

[Enquiring minds want to know...]

Pete G.
Mar 13, 2007, 12:31 PM
Registered User
steveciambrone's Avatar
It is great to see it has made it to market, I to saw it over a year ago at the Visalia engineering show. It is based on the single cyclinder engine they have, which also runs well. Can't beat the price.

Mar 13, 2007, 01:24 PM
Mmm, tugs...
patmat2350's Avatar

They have boilers too.
They say throttle/reverse is accomplished with a single control valve (one servo).

Pat M
Mar 13, 2007, 06:41 PM
Registered User
steveciambrone's Avatar
I have built the vertical boiler, and it works well, converted mine to meths, it would probably do well on sterno. Do not use the fuel pellets they sell, low heat and they clog up the flue's. It does need a few parts machined. The way it is designed it only needs lead free solder and not silver solder, but it would be better if it was built with silver solder.

Mar 13, 2007, 09:25 PM
floating and flying
misfitsailor's Avatar
OK, here are the dims: Overall width= 4 1/2", length= 2 7/8", and 2 7/8" tall.

And yes, one servo moves a single control arm that gives variable forward, reverse, and at the middle stops the engine.

To order the #8 you have to call P. M. directly at 1-800-724-3801, as this engine is not on the website yet.

My Graham TVR1A still doesn't have enough running time on it to make a good comparison. It has many o-rings to wear-in and still needs much higher pressure than it should once it has been broken in. It is also very complex with many truly tiny parts. 3 times so far running sessions have been interupted by some microscopic screw coming loose somewhere. It is my favorite steam engine, but it has a slow road getting it sorted out.

I also have the PM Vertical boiler and I am almost finished, but am a little nervous about the riveting. I made the tools, but the one test rivet I set in scrap didn't look up to par. This boiler would need a subtantial vessel, as it is heavy and tall. I test floated it in a few hulls and had stability problems. Narrow beam and shallow displacement will not do.

steveciambrone, you were at Visalia too? What a small state. I was bummed they didn't have it again this year. The BAEM club is having a show June or July, I forget which, somewhere in the Bay Area. This is my first year as a member, I'll have to check the newsletter for details.
Mar 13, 2007, 09:50 PM
Registered User
steveciambrone's Avatar
Yes, I was at the Visalia show all three years, 2005 running boats, 2006 running G Scale Live steam and one small steamer boat. Nice show but lack of attendance killed it.

I am interested in your results of the graham engine, My feelings are mixed, I have seen G scale Shay's powered by grahams and they run fine. But I have had an experiance with one of the single engines and the same twin as yours and the results were not that good. The twin was built by graham and it had real problems getting it to work, the owner finaly gave up and put an electric motor in its place.
On the other hand I built the PMR oscilator single as my first machining project and in short order I had it running. So I was not surprised that you had pleasant results with the V twin. Should be pretty strong engine with two 1/2" bore cylinders.

Mar 13, 2007, 10:01 PM
Registered User
steveciambrone's Avatar
For the boiler

I did not use the rivet tool in the instructions, at work the had an puenmatic riveter and I used that, about a 15 minute job.

It will take a large boat for that boiler since it sits so high 40-50 inches.

Mar 13, 2007, 10:04 PM
floating and flying
misfitsailor's Avatar
Brooks, When I built the TVR1A I faced the needed surfaces on a thick piece of glass. I think I recall using 600, and 1000 grit wet-or-dry sandpaper. The water holds the paper to the glass like glue. At the same time I wet-sanded smooth any part that I was going to polish. Great care must be taken to not over do it. Slow and gentle. Also be very careful if polishing these parts on a wheel. They can get away in a hurry. I used a 3" cloth wheel on a mini grinder, using white(?) compound. Did you order the fancy fastener kit? I think it is worth it to have all those scale looking bolt heads. The only thing about the upgraded hardware is trying to identify where the bolts and screws go, because not every fitting is replaced with one from the fancy screws kit. Take great caution when fitting the manifolds. Some parts you may want to do a dry fit first before using the gaskets. The valve shafts are super skinny, and only brass. Pretend you are a watch maker, you may find joy using a magnifying lamp to work on this little gem. The engine will be really stiff when first assembled, be sure to oil well and be careful not to allow the engine to race too fast when you put the air to it the first time. Did you buy the marine flywheel for it? Without some kind of flywheel it would be difficult to assemble, and would not run as smooth. When timing and adjusting the engine, be sensitive to parts binding. In all double-acting steam engines, part of the goal is to have the free space in the cylinder equal at TDC as it is at BDC. In other words to have the piston sweep perfectly centered in the cylinder. Anyway, the instruction book is very good. It is a great kit, I am sure you will enjoy the journey.
Last edited by misfitsailor; Mar 13, 2007 at 10:35 PM.
Mar 13, 2007, 10:18 PM
floating and flying
misfitsailor's Avatar
Steve, I also have the 2A single from PM. The new twin is nice because of the new cylinder design with a gland to seal the piston rod. My 2A leaks like crazy in that area. Yes, the Graham engine is at odds with Murphy's Law. It is truly cool, but not robust like the new PM or even the Wilesco v-twin. I used to look down on Wilesco stuff, but after buying the v-twin setup (discount seller in Germany) I had to change my mind, as it runs great and on very little pressure.

What kind of rivet air tool was used on the boiler? You cheated! lol

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