Author Topic: A Beginner's First Engine (Single-acting Oscillator)  (Read 6793 times)

Offline Kim

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #180 on: March 19, 2019, 05:38:52 PM »
Congratulations Gary!  It's great to see your little oscillator running so well!
Kim

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #181 on: March 19, 2019, 09:05:32 PM »
Thank you guys. I am reassured. Much appreciated!

@ Jason - I'll run it for a couple of weeks then take a look as you suggest.

 :ThumbsUp:

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #182 on: March 19, 2019, 09:17:03 PM »
Any thoughts yet on your next build?

I knew you would ask me that!   :Lol:

1. Finish the walnut base for this engine.
2. Finish DRO install on my mill by making protective covers for the scales.
3. Sort out the utterly chaotic mess that has consumed my workshop during the build. Small engine, big mess.
4. Test the Indian pressurizing kerosene stove as the heat source for this engine.
4. Optimise the boiler both functionally and visually.

and then...

5. I'm not done with single-acting oscillators yet. In due course I will move on to double-acting ones and fixed cylinder engines with valves. And of course there's the PMR #6 kit but that's further down the line again. However, for my next project I plan to build two single-acting oscillators at the same time.  Twice the size of this one (24 mm bore); one single cylinder and one twin. The main working components will be the same so I'll be able to get three times the benefit out of each setup. And again, the look and aesthetics will be a bit 'different'...


Offline MJM460

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #184 on: March 20, 2019, 12:54:39 AM »
Hi Gary, great to see it running on steam with your boiler.  Certainly appropriate to be basking in the glory of that first run.

I believe it will already be worthwhile taking off the nut and spring to remove the cylinder and closely inspect the port face, I think you will already be able to see if the wear pattern is even around the ports or not.  I have found that each of my oscillating engines benefited from some extra work on the port faces of both the cylinder and the standard.  I hesitate to call it lapping, I used 800 grade wet and dry, possibly even 1000.  Some will probably say not fine enough, but I found it wears in quite quickly from there.  I also tried Brasso on the face, assembled the spring to hold the faces together while I turned the engine by hand.  An electric drill might have been better for this.  Not sure whether brasso is course or fine compared with the wet and dry.  I only had a machined wooden block with a hole for the pin to back the abrasive, and punched a hole on the paper so it would lie flat.  With that stand, you might have to square off the end of a dowell in the lathe and drill it for a wood locating pin, and again punch a hole in the paper.  Obviously both surfaces have to be flat to seal.

As far as I remember you donít have a superheater so the boiler only produces saturated steam.  Then that long copper tube makes quite a nice condenser, so the engine is probably seeing very wet steam.  That may be increasing the dramatic effect of the leakage.  Perhaps it would be worth setting the engine on a block and trying a quite short pipe, insulated by wrapping with strips of rag.  Might help a little, though port face sealing is the key.  Then a little exhaust separator to reduce the water condensing everywhere.

Looking forward to seeing the next build.  I also tried a double acting one before I started on the slide valve ones.

MJM460

The more I learn, the more I find that I still have to learn!

Offline crueby

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Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #186 on: March 20, 2019, 06:59:35 AM »
Hi Gary, great to see it running on steam with your boiler.  Certainly appropriate to be basking in the glory of that first run.

I believe it will already be worthwhile taking off the nut and spring to remove the cylinder and closely inspect the port face, I think you will already be able to see if the wear pattern is even around the ports or not.  I have found that each of my oscillating engines benefited from some extra work on the port faces of both the cylinder and the standard.  I hesitate to call it lapping, I used 800 grade wet and dry, possibly even 1000.  Some will probably say not fine enough, but I found it wears in quite quickly from there.  I also tried Brasso on the face, assembled the spring to hold the faces together while I turned the engine by hand.  An electric drill might have been better for this.  Not sure whether brasso is course or fine compared with the wet and dry.  I only had a machined wooden block with a hole for the pin to back the abrasive, and punched a hole on the paper so it would lie flat.  With that stand, you might have to square off the end of a dowell in the lathe and drill it for a wood locating pin, and again punch a hole in the paper.  Obviously both surfaces have to be flat to seal.

As far as I remember you donít have a superheater so the boiler only produces saturated steam.  Then that long copper tube makes quite a nice condenser, so the engine is probably seeing very wet steam.  That may be increasing the dramatic effect of the leakage.  Perhaps it would be worth setting the engine on a block and trying a quite short pipe, insulated by wrapping with strips of rag.  Might help a little, though port face sealing is the key.  Then a little exhaust separator to reduce the water condensing everywhere.

Looking forward to seeing the next build.  I also tried a double acting one before I started on the slide valve ones.

MJM460

Thanks MJM. I'm working for the next two days but will look at the port faces at the weekend. I have a tube of 'Autosol'. Don't know if you have that brand in Australia or not, but I'd say it's a bit coarser than brasso and comes in the form of a cream, so it may do the trick. I think that maybe running the faces together with a drill and abrasive between them could be better than trying to isolate high spots to work on (which is a bit like shortening the legs of a table).

Regarding the piping - the long pipe was only provisional to try it out, but yes, I hadn't considered it's acting as a condenser. Also, I discovered last night that I hadn't soldered one of the nipples on to it properly so it was leaking!  You can probably see it in the video, at the engine end of the tube. So I might as well shorten the tube when I redo it. As for a condenser, that's something I'd like to do in due course (in the pipeline, so to speak   :) )

@ Chris - thanks!

Offline MJM460

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #187 on: March 20, 2019, 10:12:03 AM »
Hi Gary, the main problem with any cream, brasso or other with the engine assembled is that it might get in around the piston, I try to use the brasso (or any other brand) with the parts separate so I can clean them well before reassembling.  Now I think a bit more about it, that is why I turned the cylinder by hand rather than with the piston in place using the drill.  But it was slow, however the drill was a thought bubble that should have been pricked with a pin.  It might be easier if you can remove those screws holding the brass port face in place so the standard can be moved around on abrasive paper on a flat surface.  Because my stand was made of brass, it had a flat surface, which made it easier to ensure the abrasive was flat.

I should have been clearer about the condenser.  It takes a lot of area to completely condense the steam used by the engine, but that long tube will ensure that the engine sees very wet steam.  A shorter one will help, especially with a bit of insulation.

 After the engine, I find a simple separator collects the small amount of water that has condensed, while the remaining exhaust seems to spread out in the atmosphere as higher humidity, and does not create as much mess.  Just a simple tank with a tangential inlet and the outlet on the centre line so any water droplets tend to get separated by the tangential velocity and the change of direction to the final outlet.  It works better than intuition would tend to suggest.  And relatively simple to make as it does not see any pressure.  I have attached a picture of two that I have made.  The vertical one is more effective, the horizontal one needs a bit larger diameter for the horizontal section.

Once you have the engine running with the boiler, it is quite satisfying to complete these small steam plants.  Now I need to follow the lead from others and include a feed pump and feed water tank.

MJM460

The more I learn, the more I find that I still have to learn!

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #188 on: March 20, 2019, 10:10:31 PM »
Thanks MJM460.

What you say about Brasso etc and the risks to the piston and bore makes a lot of sense, so I'll avoid that.

I could remove the screws but one of them is JB Welded in due to a booboo I made so I'd have to take the head off and redrill, so I'll look at the port faces and lap any obvious high spots then let it wear for a while and see how it goes before I look at other options.

On condensers and steam separators, yes, it will be fun to explore these avenues in due course. Relatively low stress compared to engines, I suspect.

 :ThumbsUp:

gary

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #189 on: March 22, 2019, 03:27:20 PM »
Disaster! Catastrophe!! Apocalypse!!! Cataclysm!!!!

Well, I exaggerate. Pest, nuisance...

No. Actually, opportunity for learning and an improved engine.   :-)

I was running it today, and the JB Weld repair failed. The cylinder came off the pivot, leaving a jet of steam shooting out of the port into thin air. I know JB Weld is good stuff; I just think that in this instance it didn't have much of a platform to adhere to:



My solution will be to lightly skim the port face of the cylinder with an endmill, then solder on a piece of flat brass bar to create a block on the back of the cylinder into which a new port and pivot hole can be drilled. A new pivot will be made. The crank pin is plenty long enough to accommodate this. Indeed, it seems to me that the thin cylinder wall left after the flat is milled is the weakest point in Steve's design (which otherwise I like) as it leaves little room for the threaded end of the pivot. In fact I had already planned to solder on a block as above when I build my next (x2 scale) version of this engine, so this will be good practice.

It will also give me a second chance to add Tug's suggested composite pivot and Peter's suggested recess.

I take it soft solder will be ok for this job?

Offline Ramon

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #190 on: March 22, 2019, 04:04:29 PM »
Commiserations Gary - sorry to hear that the JB wasn't enough to hold but as it appears that it was just a small fillet around the pin it's not surprising given the movement involved.

Your thoughts on soldering a plate to increase the thickness are on the right track - I had thought you were going to do that originally for as you say once the cylinder is milled to give a flat it leaves very little left in which to drill and tap a hole of decent depth to hold the pin.

FWIW - some time back I rebuilt a Blackgates Vee twin Oscillator and had to make new cylinders. I did not post on here but on a model boat forum. (That was where the image of the pin previously posted here emanated from) Given what's occurred it may be worth your time to take a quick run through before setting out again ? Anyway it's here if you think so https://www.modelboatmayhem.co.uk/forum/index.php/topic,53472.0.html

Soft solder will be OK to hold a plate on but if you do be aware that you will not be able to silver solder it after unless all traces of solder have been removed (usually re-machining is required - see the thread mentioned)

A slight set back but one which I'm sure you will soon overcome - good luck :ThumbsUp:

Regards - Tug
"I ain't here for the long time but I am here for a good time"
(a very apt phrase - thanks to a well meaning MEM friend)

Offline gary.a.ayres

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #191 on: March 22, 2019, 04:12:28 PM »
Thank you Tug.

Yes, in the design there is no plate but I think one will effectively be an upgrade to take forward into future projects.

I'm aware of the incompatibility between soft and silver solders but I don't think I'll need to use silver solder on the cylinder anyway so it should be ok.

I will read your v-twin thread with interest at some point over the weekend.

All the Best, and have a great weekend.

gary

Offline Gas_mantle

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #192 on: March 22, 2019, 05:04:41 PM »
Sorry to hear it failed on you but I guess it is proving to be a good model to learn on  :(

It's a pain to have to modify it but it sounds like what you are wanting to do will improve things. Once it is up and running again I'd experiment with different springs, I'm not saying the one in your photo is necessarily too strong but it looks a bit rough and ready and I think the look of the engine could benefit from something a little more delicate.

Offline crueby

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #193 on: March 22, 2019, 05:10:14 PM »
Bummer on the broken joint, but your solution sounds like a good plan. If you drilled/threaded the new block for the pivot before soldering on, you could through-thread it?

Offline b.lindsey

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Re: A Beginner's First Engine (Single-acting Oscillator)
« Reply #194 on: March 22, 2019, 11:21:52 PM »
Hang in there Gary. You will overcome this I am sure.

Bill