Author Topic: Four Valve Non-Releasing Steam Engine  (Read 89282 times)

Offline Maryak

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Re: Four Valve Non-Releasing Steam Engine
« Reply #240 on: January 14, 2013, 08:01:56 AM »

How about turning the problem round and using a milling machine like a drill press to act as a shaping ram and the X/Y mill table to move the work.

Jo

Good idea Jo, you only need to use the quill for the sharp corners required and not doable with an endmill.

Best Regards
Bob
Если вы у Тетушки были яйца, она была бы Дядюшкой

Offline Captain Jerry

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Re: Four Valve Non-Releasing Steam Engine
« Reply #241 on: January 17, 2013, 02:51:03 PM »
Thanks for the suggestions.  I'm going to have to work out something but using the mill quill may not be good for me since I have no way to lock the rotation.  I think I'm going to stick with a file for now.  I believe that I have succeeded in assembling a working release, shown here:



All of the pieces go together and function.  I don't think that it would function flawlessly at 60RPM but that is a matter of refinement of the latch edges.  I may have been incorrect to say that the hook would be the most difficult part.  The cam is also a challenge.  Full size parts would have an adjustable cam lobe position but the only way to make any adjustment on this one is with a file and there is no un-file.

The spring is also a challenge (I hate springs).  For this I am using music wire that is .020" and that may be too much.  The force is a bit heavy and I will try to make adjustments today.  For the governor to be able to control this valve, the spring tension must be light so that no rotation is transferred to the cam arm.  Keeping the spring in position is another challenge.  If you look closely, you may be able to see the small groove that is filed in the top of the hook where the wire sits.  The other end of the wire, where it is attached to the double arm must be held firmly and there is no room for a clamp.  I solved this by making a 90? bend in the wire an putting it in a hole in the double arm.  I don't have any way to drill a .020" hole for this so I drilled .078", inserted the wire, and followed with a brass wire .063" as a locking wedge which was then filed flush.  It holds well, does not interfere with the hook, and can be driven out if needed.

Pivot points are also critical. particularly on the hook.  On this one, the hook pivots on a brass bushing that is held onto the double arm with an #0-80 bolt.  The bushing is slightly longer than the thickness of the hook, so the bolt holds it fixed and the hook rotates on the brass bushing. 



This picture shows the assembly along side of the engine and to my eye looks oversize.  On my engine, the valves open on the inside and the release and dash-pots are located between the valve and the wrist plate so the bulk may not be as obvious.  I am going to continue to refine this but it may have to wait for a larger engine.





Jerry
« Last Edit: January 24, 2013, 01:27:17 AM by Captain Jerry »
NOTARY SOJAK

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Offline Captain Jerry

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Re: Four Valve Non-Releasing Steam Engine
« Reply #242 on: January 23, 2013, 05:02:16 AM »
I haven't updated this for a while because I have been hoping to find a way to implement a governor controlled valve release.  That search continues. But in the meantime there are other things to do.  It must be remembered that Corliss engines were designed to run at between 60 RPM and 160 RPM under load. Corliss engines were meant too run at high steam pressure with the throttle wide open and the speed (and power output) governed by short burst or high pressure steam with precisely timed valve opening and closing.   The precision is the key.  The precision is possible because the valves at each of end of the double acting cylinder can be adjusted independently and the timing adjusted to perfection.

That is not really possible with a slide valve engine.  The timing of a slide valve engine is fixed by the fixed dimension of the valve.  The cylinder halves can be balanced but each side cannot be optimized without remaking the valve.  To run well at low speed, each cylinder half must carry its half of the cycle and deliver the crank to the opposite half with enough momentum to reach the point where the load can be picked up and carried by the other half.  That is hard to do on a small model because it usually means dissassembly of the valve chest.

On a Corliss engine, the overall performance is affected by the design of the linkage from the eccentric to each valve edge.  It includes the eccentric throw and advance angle and the geometry of the wrist plate but each individual valve can be fine tuned by adjusting the length of the rod between the wrist plate and the valve lever arm.  That can be done without disassembly if the rod is made with right and left hand threaded ends as a turnbuckle.  I don't know if left hand taps and dies are available in #2-56 or 1.5mm thread size.

If the rod length is fixed, the adjustment could be made by rotating the valve lever arm on the valve spindle.  This is never done in full scale practice where the lever arm is always keyed to the spindle.  It is difficult to imagine that a reliable clamping method could be devised at small scale.  I devised a way to firmly fix the lever arm to the spindle (loctite) and still allow adjustment by rotating the valve edge on the spindle within the bore.  This method has no basis in full scale practice but I think it is far more reliable that moving the lever arm on the spindle.

Details of this valve design are shown earlier in this thread but the adjustment is easy.  The back side valve bonnets are removed, revealing the adjustment mechanism.  I don't completely remove the bonnet.  I remove all but one bottom screw and rotate the bonnet so that it reveals the adjustment but prevents the valve from sliding out of the valve bore.  In fact, the engine can be run under power with the valve covers open with only minor, if any, air loss.  Try THAT! with a slide valve.  I have no experience with steam.

There may be better ways to do this but here is my methodology using a calibrated and certified 75 year old eyeball to measure the crank angle. I set the crank at TDC and then with the throttle valve open and the regulator set to 100 PSI and then, holding the flywheel, slowly rotated the crank past TDC untill I could feel the valve open and attempt to drive the crank.  I adjusted the valve to achieve opening with the smallest angular advance past TDC.  I then rotated the crank 180? to BDC and using the same method, adjusted the steam valve for the rod end of the cylinder.   

Setting the exhaust valves was not as clear cut.  I was not as concerned with closing the valve early to provide compression cushioning but I wanted to be sure that it was fully closed when the steam valve opened.  I could clearly hear the high pressure air blowing through the cylinder by listening to the exhaust pipe.  I thought about sticking the exhaust pipe in a glass of water and watching for bubbles but i didn't.

By tweaking these adjustments, I was able to achieve reliable operation at 60 RPM or less under no load.  During all of these test, the local air regulator was wide open and the gauge was reading between 125-150 PSI and the air flow controlled by the globe valve at the top of the cylinder.  The globe valve was modified to give finer control with a tapered seat and stem, not as severe as a needle valve, but still slower opening and secure closing.

Here is the result:



Before I can give control over to the governor, some modifications need to be made.  The crankshaft pulley needs to be larger to increase governor speed and all of the control linkage needs to be tightened up.  There is a lot of lost motion due to sloppy fits.  There is plenty more to do.  Oilers, guard rails, piping.  And, oh yeah, release gear.

Well, its  got dash pots.  I guess you can call it a Corliss!




Jerry

Wow!  That was a long post.  If you read the whole thing, you deserve some entertainment!  Sorry,  my tutu has a beer stain on it.
« Last Edit: January 24, 2013, 01:30:55 AM by Captain Jerry »
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Online steamer

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Re: Four Valve Non-Releasing Steam Engine
« Reply #243 on: January 23, 2013, 05:07:19 AM »
Oh Jerry!

That's georgous!   I can't watch the video's at the moment because I need to update my quick time....but wow they look nice!

You have come a very long way in a very short time Captn!   Well done sir!

 :praise2: :praise2:

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Jo

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Re: Four Valve Non-Releasing Steam Engine
« Reply #244 on: January 23, 2013, 06:26:08 AM »
You and me both Dave,  I also cannot run the vid :killcomputer:. I am looking forward to seeing this running Jerry.

Jo
Enjoyment is more important than achievement.

Offline Captain Jerry

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Re: Four Valve Non-Releasing Steam Engine
« Reply #245 on: January 24, 2013, 01:39:26 AM »
In my previous post I included two videos from my Photobucket album but for some reason these require the user to have Quicktime player.  I don't know why.  I posted the videos on Youtube and here are the links if you want to try them.  If anyone can tell me why the Photobucket one want Quicktime, I will try to fix it.

http://www.youtube.com/watch?v=tONFyxwD3Fw&feature=player_detailpage

http://www.youtube.com/watch?v=EOqLJDC9Nvk&feature=player_detailpage

Thanks for watching

Jerry
« Last Edit: January 24, 2013, 01:48:49 AM by Captain Jerry »
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Offline Don1966

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Re: Four Valve Non-Releasing Steam Engine
« Reply #246 on: January 24, 2013, 02:27:24 AM »
Jerry that is one awesome looking engine. Real quiet runner and beautifully finished. You really can't relate to how small it is till you put your hand in the video. Jerry I like........ :praise2: :praise2:

Don
« Last Edit: January 24, 2013, 03:09:40 AM by Don1966 »

Offline NickG

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Four Valve Non-Releasing Steam Engine
« Reply #247 on: January 24, 2013, 10:46:49 AM »
Yep, brilliant Jerry, love the paint work. YouTube is so much better for videos anyway, the first vid would still be buffering on photo bucket !

Online steamer

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Re: Four Valve Non-Releasing Steam Engine
« Reply #248 on: January 24, 2013, 11:02:13 AM »
I saw it that time Jerry!   Brilliant!

Well done buddy!

Dave
"Mister M'Andrew, don't you think steam spoils romance at sea?"
Damned ijjit!

Offline Captain Jerry

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Re: Four Valve Non-Releasing Steam Engine
« Reply #249 on: January 24, 2013, 01:59:22 PM »
Jerry that is one awesome looking engine. Real quiet runner and beautifully finished. You really can't relate to how small it is till you put your hand in the video. Jerry I like........ :praise2: :praise2:

Don

Well, that's one conclusion, but maybe you underestimate just how big I am :LittleDevil: .
NOTARY SOJAK

There are things that you can do and some things you can't do. Don't worry about it. try it anyway.

Offline Tennessee Whiskey

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Re: Four Valve Non-Releasing Steam Engine
« Reply #250 on: January 24, 2013, 07:43:13 PM »
Sweeter than Omalene :cartwheel:

Eric

 

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