Author Topic: A digital governor for model engines  (Read 17946 times)

Offline steam guy willy

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Re: A digital governor for model engines
« Reply #135 on: May 26, 2020, 10:24:42 PM »
Hi Jason ,  I only have this photo unfortunately and it has been made with castings. This is the uncropped photo however...To give a better idea of size ?

Willy









Offline gary.a.ayres

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Re: A digital governor for model engines
« Reply #136 on: June 01, 2020, 10:27:49 PM »

My posts will be a bit further apart now as the governor seems to be complete and working.  I will do some of the little tidy up jobs I have mentioned, as fill in jobs over the coming winter evenings.  But they won’t be very exciting to describe.  If something fundamental changes, I will certainly describe it, otherwise just a final report when they are done. 

Now that the best weather of our year is over, we will be allowed overnight trips from next week, so have some catching up to do.

MJM460

Congratulations, MJM, on your success with the governor! It didn't take you long.

A video of it in operation would be good when the time is right for you...

But meanwhile, please enjoy your overnight trips and catching up.

 :cheers:

gary

Offline MJM460

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Re: A digital governor for model engines
« Reply #137 on: June 02, 2020, 12:15:13 PM »
Thank Gary.  When I first decided to try the project, I hoped that it would not take long.  But I did wonder if it could really be done by such a simple system.  So I started, but delayed actually posting until I really had the end in sight. 

It was just as well, as some of the delays along the way would have led people to lose interest before the project ended. It was about 15 months in all if I remember correctly.

Sure enough as you will have seen, there were problems with the one chip solution, but the very helpful Picaxe support forum guided me through to a successful conclusion.  The next generation will have the two chips on the same board to eliminate some of those ugly flying leads.

It is very pleasing to see it work, but a video will be a whole new challenge.  I should be able to do the video, but I guess I will have to try.  The video software I previously used stopped working, as they did not update to windows 10, and my attempt at buying new only proved the inadequacies of my computer.  So I will have to try the Apple version.  There seems to be two options on the iPad, but will have to check how I go on an Apple computer, as that might be easier.  Any suggestions as to what is easiest for editing a few clips together?

Then I will at last have to learn how to post it.  I will try, but don’t hold your breath.

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 digital governor for model engines
« Reply #138 on: June 04, 2020, 12:51:32 AM »
Ah - ok.

No doubt it makes for a much more interesting thread than the likes of mine, which details every misconception and rookie error. Well, most of them, anyway...  ;)

I would imagine your Apple computer would be the way to go for video editing, a laptop or a desktop system probably being easier than an iPad. I'm not a good source on such matters, though - I use Linux (Ubuntu) and the free video editor 'Pitivi' on my laptop.

As for posting videos - well I'm not sure but I suspect some form of external hosting is required' just as it is for photos. Hopefully someone will correct me if I'm wrong. I just put mine on youtube and then embed them using the youtube button in this editor. Of course, if you don't have a youtube channel you may not want one... and you can switch your video settings to private in youtube but then I *guess* they would then become invisible in the forum here too. Sorry - not making assumptions about what you would want to do - just exploring the matter within my own rather narrow limits.

Meanwhile, no held breath here (i.e. no pressure from me) for a video. Enjoy your catching up!

gary




Offline crueby

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Re: A digital governor for model engines
« Reply #139 on: June 04, 2020, 01:58:05 AM »
On youtube there is a setting between private and public, something like unlisted, that lets only those with the link see it. So, it would show uere on the forum but not to anyone just browsing.

Offline gary.a.ayres

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Re: A digital governor for model engines
« Reply #140 on: June 04, 2020, 09:25:11 AM »
Ah ok - useful to know. Thanks Chris.

Offline MJM460

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Re: A digital governor for model engines
« Reply #141 on: June 04, 2020, 01:26:10 PM »
Thanks, Gary and Chris.  I have had a look at the clips and iMovie aps on my I pad and it seems clear that iMovie is the one to actually edit clips together.  The Clips Ap might be useful to tidy up a single clip before incorporating it, but iMovie seems to have editing facilities of its own, and also quite good help information.

So first I will have a go at making a short movie, then see if I can post it.

Good to know about those privacy settings thanks, Chris.

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 digital governor for model engines
« Reply #142 on: June 04, 2020, 09:26:30 PM »
Yes - the setting flagged up by Chris sounds like a real boon generally as it will allow for posting unedited bits and pieces on the forum to illustrate points/work in progress without these having to be displayed to the world on youtube.

Now that I know about this I can see that quite a few forum members probably do it this way.

Enjoy your movie-making - in your own good time!

 :ThumbsUp:

Offline MJM460

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Re: A digital governor for model engines
« Reply #143 on: July 10, 2020, 10:20:40 AM »
Hi Gary, enough procrastination, I have assembled a video and now time to bite the bullet and post.

Not that I haven’t been busy.  We had quite a lot to do when the lockdown was partly lifted, and just as well we got on with it, as now we are back under lockdown. 

I was also able to get a small oscilloscope working to look at some wave forms.  Not a fully professional item, but a small pic chip based unit that uses the computer for much of the functionality.  It is teaching me heaps.  I need to do some more analysis to try and extract some meaning from it all.  But I certainly have plenty of data.  Thanks to an understanding wife, tolerating my running the compressor in the house so I could drive the engine when it was tethered to the computer.

So here is my attempt at presenting the project with a video.  Not ready for the showcase yet, but gives an overview of what a proof of concept looks like.

I am quite pleased with the result so will now install it in an enclosure in a bit more permanent manner.  Fortunately I was able to pick up a few necessary parts in the last few hours before lockdown started.For mental health purposes of course!  With six weeks in front of us now, those of us with hobbies are indeed fortunate.

So keep your distance, and now wear a mask when you cannot stay away from others, and enjoy this little video.

[youtube1] <a href="https://www.youtube.com/watch?v=qniJPISyDF4" target="_blank">http://www.youtube.com/watch?v=qniJPISyDF4</a>[/youtube1]


Thanks for looking in

MJM460
The more I learn, the more I find that I still have to learn!

Offline deltatango

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Re: A digital governor for model engines
« Reply #144 on: July 11, 2020, 01:38:12 PM »
Hi MJM,
Have you tried loading the engine to see how well the governor responds?
David
Don't die wondering!

Offline derekwarner

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Re: A digital governor for model engines
« Reply #145 on: July 11, 2020, 02:50:49 PM »
Goodness MJM......

That's pretty impressive  :Director:  :cheers:........maybe takes the visual mistique of a steam governor away, but sure will be accurate ...

Will be interested in understanding a little more about the butterfly valve used  :headscratch: in the air path.....would it react in the same manner with steam?

Derek
« Last Edit: July 11, 2020, 03:01:50 PM by derekwarner »
Derek L Warner - Honorary Secretary [Retired]
Illawarra Live Steamers Co-op - Australia
www.ils.org.au

Offline steam guy willy

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Re: A digital governor for model engines
« Reply #146 on: July 12, 2020, 12:40:48 AM »
Hi MJM , thats looking really good and quite impressive ... will you be adding more feedback info to refill the boiler and stoker controls and perhaps a dynamo to power the Cct's  and such like  ??

willy

Offline MJM460

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Re: A digital governor for model engines
« Reply #147 on: July 12, 2020, 12:00:29 PM »
Hi Delta Tango, I only have a crude variable load, rubbing a finger on the rim of the flywheel, but the governor responds quite well, if a bit slowly.  It would not quickly ramp up to full power as would be required for Brian’s edger when the board hits the blade.  But then it’s probably not a powerful enough engine for that load.

Part of the slow response is due to the small burner on my boiler, and my small compressor when on air.   And some is due to tuning.  I am currently rebuilding the governor on a single board in a separate enclosure, and I will include a second potentiometer so the proportional band can be adjusted more easily.  One of the limitations of the chip is that the cycle program is quite dependent on the engine speed, so the tuning is very different at low speed from optimum at high speed. 

Then I had better work on a more appropriate load.

Hi Derek, thank you for the compliment.  Without doubt, for mystique, a steam engine needs a scale governor.  We have some members on the forum with the skill to make the real thing fully operating, but I am not one of them. 

Part of the reason for building this governor was the knowledge that only recently (in historical terms) the fly ball governors are being replaced by digital devices, and I noticed that the microprocessors that I have a play with occasionally seemed to have all the functions necessary to make one, though it turned out to be a bit more complex than a single chip.

For a project needing a better governor than can easily be achieved with true scale, I can see extending a control valve operating rod down through the base board to conceal a helper servo below, but that won’t appeal to everyone.  In the mean time it will maintain a constant engine speed for my engine testing experiments, and it has been quite instructive to develop and build.

As with any butterfly valve, it does not have a very linear characteristic, and the first bit of opening has the biggest effect, while the last bit, when the disk is close to parallel to the pipe flow, has very little.  Some of that can be compensated for by the geometry of the link to the servo.   It it works just as well when I fire up the boiler and run on steam.  No reason to expect it to be any different between steam and air, at least not enough different to be able to tell without quite precise measurements.

Butterfly valves at this small scale are not easy to get to shut off tight, so I made a separate stop valve, but when the piping was complete so I could run, simply operating the butterfly valve by hand, it actually shuts off well enough to stop the engine, and controls from stop to maximum with about 60 degrees of rotation of the shaft.  This makes it very suitable for servo operation. 

I use about 90 degrees of servo operation and the lever lengths to operate the valve through 60 degrees.

Hi Willy, I am glad you like it.  You are quite right to bring up the point of boiler controls.  The throttle valve controls engine speed, but to control the steam plant, if the engine load is reduced, it needs less steam, so the energy input must be reduced.  And less water will be required, so the boiler feed flow will also have to be adjusted.

However, these things do not have to be linked to the governor, and separate controllers are quite satisfactory.  A boiler water level controller will detect the level rising and react accordingly.  Similarly the boiler pressure will rise, and the pressure controller can control this by reducing the fuel flow.  The instruments are quite independent, but they are linked by the behaviour of the steam plant.  The thermal mass in the boiler and the volume in the steam space slow down all the processes so there is plenty of time for separate controls to operate.   Mind you, if the plant reacted much more quickly than the typical fired steam plant, cascading the controls might help, or even be necessary to speed up the response.

Thanks to all for looking in,

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 digital governor for model engines
« Reply #148 on: July 12, 2020, 10:48:21 PM »
Great video, MJM - it really illustrates how the setup works for the electronically challlenged such as myself.

The system is so precise and responsive. Very tight.

I really like the look of your steam plant too - the boiler and the engine both have that great look that arises from their functionality.

Congratulations on a great project.

 :cheers:

gary

Offline Zephyrin

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Re: A digital governor for model engines
« Reply #149 on: July 13, 2020, 08:19:25 AM »
Very nice video MJM, full success with the governor congratulations ! butterfly valve are not the easiest type to make.
your steam plan looks great too.

 

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