A Couple of Wobbler's

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nemoc

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Hi all, It's been a while since I posted in the Finished Projects section. I have been building but had a couple of failures. I haven't given up on them but decided to put them aside for a little while. What I have here are 2 wobbler's. Both are double acting. The larger one is self starting with a speed control. While I was waiting for the polyurethane to cure on the base I built the little one.



[ame="http://www.youtube.com/watch?v=17PvlH7cD_8&feature=plcp"]http://www.youtube.com/watch?v=17PvlH7cD_8&feature=plcp[/ame]

Craig
 

Inky Engines

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Craig

Sorry to hear about the failures, but you must be pleased with the way the wobblers turned out. There is something particularly satisfying about an engine that starts without the customary nudge! The photograph really shows them off to good advantage. I don't recall seeing this design before, is it your own?

Kind regards

Geoff at Inky Engines
 

nemoc

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Hi Geoff, Yes I'm happy with the way they turned out. They are my own design, and that lets me work with what I have on hand. When I build from plans it seems I always need to get something to get it done. Besides I like having a one of a kind engine.

Craig
 

Davyboy

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Craig. very nice design and really great looking engines. The pipes and plumbing on the bigger one look good too. I like your idea of having one of a kind.

Davyboy
 

rhitee93

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Those are pretty classy looking engines. They have a nice style to them :)
 

skyline1

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Lovely jobs, the larger one reminds me a little of the sort of engines fitted to early paddle tugs. They were often inclined twin oscillators (Wobblers) in full size.

I imagine the piston rod gland on the crankshaft end of the cylinders is a bit tricky because of the side thrust.
 

nemoc

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Thanks for the compliments, Skyline the glands weren't too bad, the tricky part was getting the crank in the right position. There was no room for set screws on the flywheel so the crank had to be pressed in. Getting it just right was difficult. We will see how the glands hold up when I get some more run time on it.

Craig
 

Annie

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What a beautifully finished pair of engines. The larger twin cylinder engine is particularly fine looking.
 

misfitsailor

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Amazing craftsmanship. Having the large engine set at an angle is purely inspired.
 

skyline1

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Hi Craig

How did you do the steam ports.

On a single acting one you can cheat a bit by setting the crank to the right position then drill right through the cylinder, port block and all, then plug the hole in the outside of the cylinder.

But on a double acting one you can't do this because the piston rod is in the way and it gets even more tricky with a twin as the port block is double sided. It would need spot on measuring to get them in exactly the right place.

Regards Mark
 

ChooChooMike

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Sweet ! I like the angled look of the larger double-wobbler. Makes it stand out from the horizontal/vertical-oriented ones !!
 

nemoc

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Hi all, Thanks for the kind words. Mark, I lay out the the ports on the block before machining, other than cutting to size. You mark the crank center and the throw. Then the cylinder pivot point. Scribe a circle from the pivot the distance to where the port will be and draw a line from the pivot point to the Crank throw in 2 places, Where the x meets the circle marks the position of the ports. The sketch may help.



Craig
 

skyline1

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Hi Craig

I see now thanks for explaining this. It calls for some very accurate marking out and drilling which makes the engine even more impressive

Having marked out the port positions you then, I presume drill right through the port block to feed both cylinders leaving you with effectively 8 ports 2 inlet and 2 exhaust for each cylinder

Although the cranks are at 90 Deg they both share the same crank and pivot pin centres so the port positions will be the same

Then drill in from the end of the port block to join the two sets of ports up and form a kind of manifold exhaust at top and inlet at the bottom or vice-versa to make the engine run the other way.

Am I right so far ?

Please excuse all the questions but I have a beautiful 1:48 Scale steam paddle tug built by my father and this engine would be a lovely replacement for her original single cylinder single acting one. there is nothing wrong with it it's a lovely little engine and very powerful (in fact the model could tow a small rubber dingy with someone in it.) but one like this would be closer to full size practice and of course self starting and reversable making R.C. a possibility.

Do you have any plans for this engine (The larger twin) or has it sort of evolved as you went along as many of these projects do.

Regards Mark
 

nemoc

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Hi mark, Now you got it. I don't have any plans for it. I worked from a sketch and figured things out on the fly. But now that you know how it is done you can design one yourself.

Craig
 
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jdella

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Hey, I was wondering if you can post some images of the individual componets of the dual cylinder engine. Some what of a breakdown of the parts and how they connect.
 

Charles Lamont

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A couple of details from the porting diagram which may not be apparent to a beginner.

The arc that the cylinder swings through gives you the size of the ports. At dead centre it should just close to both steam and exhaust. Any bigger and you blow through direct from steam to exhaust, any smaller and you have undesirable dead spots. So the port diameters should be half the arc length.

The closer the cylinder pivot is to the crankshaft, the greater the angle of oscillation, and the bigger the ports can be. Equally, the further out the ports are radially from the pivot, the larger they can be. These considerations may make a difference if you want power out of the engine, like for driving a boat.

In full size, porting is more important, and the ports were usually truncated sectors or 'tapered rectangles' to maximise their area.
 

nemoc

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Hi everyone, Iv'e been away for a while. I went to the Bahamas on vacation and a hurricane showed up. Then it followed me home to NY. Lost power for a week & internet for 10 days. Lucky I have a generator that ran most of the house. Any way jdella I will try to get some pics for you. There are some things that are hard to take apart. The cylinders are held to each other by a spring that goes through the block and would probably get mangled if I take it apart. Also the flywheel is pressed onto the crank, so that is staying put too. I will get some pics up soon.

Craig
 

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