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Green Twin Oscillator - 2019 Update

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PatJ13/02/2019 19:27:32
41 forum posts
28 photos

I finally got the green twin oscillator running the other day.

Still a bit more work to do with painting and fasteners, but it is running.

Not a great video, but I will take a better one when the painting is done.

And I built a new furnace for iron work, and it is shown here.

It works extremely well at melting iron.


How goes it on this side of the pond ?



Edited By PatJ on 13/02/2019 19:28:08

Edited By PatJ on 13/02/2019 19:29:00

Edited By JasonB on 13/02/2019 19:44:55

JasonB13/02/2019 19:45:30
17856 forum posts
1954 photos
1 articles

Looks good Pat, it's been a long time in the making but worth the effort.

PatJ13/02/2019 21:01:29
41 forum posts
28 photos

Thanks Jason.

It is far from "JasonB-grade" quality, but I am pleased with it, since it is basically my second engine, with my first engine being a simple small wobbler.

It all started as just a whim to see if I could do some serious modeling in 3D, and the next thing I knew, it mushroomed into a foundry hobby, etc.

I must say it is great fun to get an engine to run, especially after many years of on and off work (six years maybe).

The flywheel was cast in gray iron, and the remaining parts were cast in 356 aluminum.


Edited By PatJ on 13/02/2019 21:02:37

Edited By PatJ on 13/02/2019 21:03:42

Edited By PatJ on 13/02/2019 21:03:59

geoff walker 114/02/2019 09:19:03
398 forum posts
154 photos

Hi Pat,

This side of the pond is good, a little cold but gradually getting warmer, assume you live stateside.

Nice model well done, runs well.

I am currently making a twin cylinder d/a oscillator with a similar configuration to yours using a central cast iron flywheel and cylinders cast in iron from home made patterns. Unfortunately I don't have foundry like yours!!!!

Could I ask is there any particular reason that you have the port blocks on the outside of the cylinders and the pivot blocks on the inside? My plan is to do it the other way round.

Also what size is your engine, i.e. stroke length, bore size etc.

cheers Geoff

PatJ15/02/2019 18:37:39
41 forum posts
28 photos

Hey Geoff-

My engine has a 1.25" bore with a 2" stroke, and a 6" diameter flywheel.

It is a 60% scale model of an engine that I saw in three photographs on the Prestons Steam Services site.

The Preston's site incorrectly lists some of the full sized engine dimensions.

The full sized flywheel is actually 10" dia, and the full sized bore is 2", with a 3.5" stroke.

I do plan on publishing full drawings for this engine this year.

Engine Builder15/02/2019 21:19:15
224 forum posts

Good work Pat.

I am interested to know what the original engine would have used for as I can't see a way power would have been taken from the flywheel. Any ideas?

PatJ15/02/2019 22:44:31
41 forum posts
28 photos

I have to assume that the power takeoff was via a flat belt that rode on the flywheel rim, and I suspect that because the original engine (and my model) have a hole in the front of the frame that would allow a belt to exit the base.

The engine could have been used in a number of applications to power machine tools, sewing machines, or small equipment, and would have been especially useful for equipment that needed a self-starting and quick reversing.

Engine Builder16/02/2019 09:48:37
224 forum posts

I see. The hole in the front was not visible in the video.

geoff walker 116/02/2019 14:21:53
398 forum posts
154 photos

Hi Pat,

Thank you for your P.M., I'll get back to you on that.

Really glad you posted the video. I was have having a real problem arranging the pipe work for my engine.

Referring back to my earlier post you have given me the answer.

By switching the port and pivot blocks around, which I can do, I will have ample space to arrange the pipe work and be able to use compression fittings.

With the port blocks inside of the cylinders space was very tight.

Thanks again Geoff

JasonB16/02/2019 14:34:03
17856 forum posts
1954 photos
1 articles

Geoff you should be able to bring any pipework out the side of the valve blocks. The two long horizontal holes shown here are usually plugged after drilling and teh air/steam comes in from the flat face. but if you just thread the ends of the two horizontal holes you can connect there

osc valve.jpg

geoff walker 118/02/2019 11:44:01
398 forum posts
154 photos

Hi Jason,

Thanks for your reply. I thought about the pipes coming sideways but would prefer to have them exiting from the underside of the valve block then down through holes in the base into a hollow plinth where there will now be ample space for the pipework, to link the blocks. All the pipework will be concealed apart from a short inlet and exhaust pipe.

I am making the blocks muncaster style with two semi circular grooves as shown in the picture.


I really must open a build log on this engine, will do when I get back from holiday.

Thanks again Geoff

PatJ18/02/2019 16:25:32
41 forum posts
28 photos

Please do Geoff, I would love to see your build log on your engine.

Pat J

PatJ10/03/2019 17:16:37
41 forum posts
28 photos

I found a few photos in an album here.






Lee Jones 612/03/2019 19:09:16
134 forum posts
82 photos

Thanks for posting Pat. Your work looks outstanding.

PatJ12/03/2019 21:42:26
41 forum posts
28 photos

Thanks Lee, I appreciate that thought.

PatJ29/04/2019 23:27:26
41 forum posts
28 photos

I took the green twin oscillator to the NAMES show Saturday (2019 show), and it was a truly humbling experience to say the least.

The guys who display at the national shows are rather good at what they do, and so my engine looked rather paltry compared to the many museum-grade engines at the show.

But for those who took the time to read the description of how the engine came about, they were impressed with the process.

And I am pleased to say that I am ahead of many/most as far as making my own iron castings, and I can definitely compete on the national scene with that, if not meet or exceed pretty much anything available commercially.


Edited By PatJ on 29/04/2019 23:29:44

Edited By PatJ on 29/04/2019 23:30:10

PatJ29/04/2019 23:47:49
41 forum posts
28 photos

A rather lowly little display (downright laughable in some ways)  if there ever was one.

My intention was to get the engine painted before I showed it, but that did not happen.

I was on the fence about displaying it, but two guy attending the show encouraged me to set it out, and so I did.

The bright side is that this little engine has put me in a position from a knowledge and casting standpoint of making some hopefully really nice engines.

And this was my first complete engine build, so I feel like I can only go upwards from here.


The jumbo Cretors flywheel casting drew as much or more attention as the green twin oscillator.

Most that looked at the green twin (without reading the text) said to me "Casting kit ?".

I said "No, home cast".

It was painfully obvious that many could not begin to comprehend what "home cast" meant.

Very few seem to cast their own engine parts, especially in iron.


Edited By PatJ on 29/04/2019 23:49:52

Edited By PatJ on 29/04/2019 23:53:26

Edited By PatJ on 29/04/2019 23:54:07

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