Twin mill engine progress

[AStroudParticipant @astroud]

This started with the fabricated flywheel, a first for me and which I asked the forum for advice.

The model is obviously inspired by the Twin Victoria which I liked the look of but I like to do my own designs and kits don’t really do it for me though I certainly admire seeing other peoples’ examples. It is all fabricated and remaining are the eccentrics and straps and a fair amount of fitting to achieve alignments and running clearances.

[JasonBModerator @jasonb]

That is coming together nicely, the squarer cylinders give it the look of a corless. Look forward to seeing it running.

[DiogenesParticipant @diogenes]

Yes, nice to see a bit of freelancing, do you make detailed plans before you start, or make a start with a general picture in mind and develop it as you go along?

I like the ‘industrial’ heft of it.

[AStroudParticipant @astroud]

Thanks for the comments.

I make a GA to get overall sizes and allow me to order the material in one go and I will make some detailed drawings. Other smaller parts are made to fit other parts so if something doesn’t go to plan then the next part can be made to suit. In the workshop I will also sometimes notice that a part does not look right, often too chunky so I will change it,  the dimensions being worked out on scrap paper. Making a twin though made the process a bit more disciplined so the 2 engines will end up looking the same.

[AStroudParticipant @astroud]

I am calling my twin mill engine finished after a few days chasing alignment issues, air leaks and mechanical noises. Hissing is still evident, hoping that is via the sliders and will reduce as they bed in. The noises are probably amplified by the base which being hollow probably acts as a sounding board. Generally pleased with the appearance and how it runs.

Here is a run, a bit short due to my small compressor size.

https://youtu.be/6pQd_rFI65U

 

[Andrew CrowParticipant @andrewcrow91475]

And very nice it is to!

Andy

[roy entwistleParticipant @royentwistle24699]

Very nice. Andy. Just a small point, Mill engines generallyturn over the opposite way

Roy

[JasonBModerator @jasonb]

That has turned out well, who neds a set of Stuart castings! Will you paint it or leave it in the flesh?

[AStroudParticipant @astroud]

Thanks, no plans to paint it, never enjoyed painting and I think I would forever be fretting about chipping the paint.

Just a small point, Mill engines generallyturn over the opposite way.

Roy

Are you sure Roy? When I put up my Corliss running in the opposite direction I was told that was wrong, the connecting rod should always be pulling the crankshaft down onto the main bearings/foundations.

[JasonBModerator @jasonb]

It is not the crankshaft where it matters but the cross head guides. It should push the cross head down on the outstroke and pull it down on the instroke

If you look at your engine as the piston moves further into the cylinder with the pully or flywheel under load if you were to have no guide bars then the cross head would tend to lift as the piston rod and conrod want to straighten. But if you rotate it the other way it will get pushed down.

Same as the piston moves towards the crank, if there were no guide bars the piston rod and conrod would tend to kink and the force go down if running the opposite way.

[roy entwistleParticipant @royentwistle24699]

Andy.  Bolton steam museum have over 20 mill engines they all run the same way. The opposite to yours. Ive lived in Lancashire for over 90 years and Ive seen a lot of mill engines.

Roy

[Ramon WilsonParticipant @ramonwilson3]

Just seen this for the first time – first off congratulations on a fine scratch build and nice result. Personally I would paint it but understand your reluctance to do so. It runs well and smoothly too but it is, as others have said, running the wrong way I’m afraid – the top of the flywheel should move away from the cylinder on a mill engine. That said, it’s ‘your’ engine, so as long as you are happy with it run it how you wish. Nice to see some actual model engineering being done👍
Tug

 

[DiogenesParticipant @diogenes]

Nice to see it ‘done’, looks good..

[PlasmaParticipant @plasma]

Bloody beautiful,  absolutely beautifully made sir.

A credit to you in every way. I wouldn’t paint it either, I bet the guys who built the big mill engines didn’t crack out the brushes and turps after putting the monsters together. They would have handed over to a painting department and they are welcome to the job lol. I hate painting, it can be the ruin of a project.

I was awarded a bronze award at a national exhibition for a group of tools I made, I polished them to a mirror finish like the display tools made in the good old days. I was told if I had left them dull I would have been given silver! Amazing that less work would have been rewarded, but the purist judge was adamant that the surface finish was wrong.  POPPYCOCK, beauty is in the eye of the beholder, and I think your engine is beautiful,  no matter which way it turns.

Mick.

[WearyParticipant @weary]

Missed this thread until now.  What an excellent and inspiring piece of work.  Now this engine posed in an uncluttered background would make a great Model Engineer magazine cover-picture.  See other thread on the subject.

Phil

[AStroudParticipant @astroud]

Thanks for the comments and more than happy to be corrected on the rotation, I will be in the workshop later to change it.

This was the drawing that caused me to initially set it as I did and query Roy’s advice:

I remember querying it on the MEM forum when I built my Corliss and was told it was due to the need to have forces pushing/pulling down on the crankshaft. Maybe trunk crossheads are treated differently.

[Ramon WilsonParticipant @ramonwilson3]

I don’t think there is any difference between trunk and slide bar crossheads as far as the rotation goes. My understanding has always been that it is to keep the crosshead in contact with the lower face of the guide rather than anything to do with the bearings. Personally, I would think that the drawing you show is wrong but I am happy to be corrected.
Having studied it a fair bit in the past I’ve always had my engines running ‘over’ and away from the cylinder but, as said, it’s what you are content with that matters most. I recall when I made my first engine – a Twin Victoria also – knowing nothing at all about stationary engines generally I made the cranks 180 degrees opposing. Taking it to the Forncett Steam Museum to display I was quickly informed of my error. An immediate rebuild of the crank to 90 degrees was undertaken😊😊

I just found this on you tube which may be of interest https://www.youtube.com/watch?v=ZkwxCCerGuU
Tug

[Martin ConnellyParticipant @martinconnelly55370]

My thought on the rotation issue is – where is lubrication going to go? The upper face of the lower slide bar or the lower face of the upper slide bar. I think you need to set it so that the main force on the slide bar is down to where there is most likely to be residual lubricant, any lubricant on the top slide bar could be patchy if it is not run and lubricated continuously.

Martin C

[Mark EasingwoodParticipant @markeasingwood33578]

Very Nice.

[duncan webster 1Participant @duncanwebster1]

Lots of mill engines have only vestigial top slides, but the bottom slide is in a well so that it is awash in oil.

[Nigel Graham 2Participant @nigelgraham2]

A lovely engine!

Yes, the rotation on very large engines was influenced by the machine’s internal forces, but might any “standard” direction of rotation been also influenced by normal practice in laying out line-drive fitted factories? Or vice-versa?

Some plant-engines were fitted with adjustable or reversible eccentrics, too, so the direction could easily be set for the customer’s requirements without needing stock opposite-handed parts. I don’t know if this extended to the very large mill-engines though.

.

Regarding painting, they probably were painted but it would not have been in the manufacturers’ interests to have their products sent out with sloppy paintwork. I doubt the parts were always all filled, rubbed down and sprayed but would likely still have been cleaned and brush-painted to a decent standard.

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