Myers Model engine works Murdoch single cylinder

[crueby]

Excellent progress!  And that sub looks great, have not gotten to Chicago yet, other than in the airport. On my list. The ships at Fall River in Massachussetts are well worth the trip too. And the Liberty Ship down in Baltimore that you can take a day cruise on (next on is this fall I think).

[55fairlane]

Finally I got around to doing more work on the one bearing stand/pillar ( I dislike lawn care, and my neighbors live to worship their lawn, mow, trim, spray for weeds, give the neighborhood busy body the finger & clean up dog poop)

So the top side needed 2 applications of epoxy and the bottom side cleaned up 100% ....that's when I noticed it was after 730pm and I haven't showered or eat since 630 this morning, so I knocked off for the evening

[55fairlane]

Progress has come to complete halt (engine room full stop.....engine room reports full stop)......I went to put this in the casting, and wanted to know how deap to make the self for the bearing (that supports one end of the cylinder) my little in my head voice (no not the one the psychiatrist warned me about) said, add the numbers up and check them to the center line of the out board bearing/cylinder support. Cylinder support 1.09 inches, stack up of bearing and pedestal mount 1.04 inches....oh crap we have a problem. Need to investigate this ......



As I was pondering that issue I noticed the cylinder support calls to be bored to 1.128 and the journal on the cylinder in 1.100 ...WTF?


And it gets better the cylinder OAL is 3.06 ..... the pivot point is in the middle of the cylinder....the drawing says it is at 1.03 ......they only missed my ½ inch!!


On the crank pin the drawing calls for a press fit, but there are threads drawn.....


The intake/ exhaust manifold.....no bottom surface to center line height, kinda important......


These things just jerk me....yes I understand mistakes are made, these drawings have been around literally as long as I have been alive, you would think some of e would have corrected the damn things by now.....I as a professional machinist (tool maker) am having a hard time figuring out these drawings, I feel for you hobby guys who may be trying to figure out, what went wrong with your build

[CI]

I think these drawings may give folks a better appreciation for one making their own drawings/engine from scratch.
3D modeling helps root out some of the problems.
I noticed on these drawings that one person did the design, and another made the drawings, and I have found that to be problematic when I use to do that (on work projects), since the 2nd person always introduces some level of error into the drawings.

Most engineers I know do their own drawings/CAD work these days, because that is much quicker than trying to discover random errors that have been introduced by someone else.

The short threaded part just locks the pin in place.
You can still press fit it, but perhaps use more of an interference fit instead of a hard press fit, so that there is less chance of deforming the crank arm when it is pressed.

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[55fairlane]

Unfortunately I am CAD CAM challenged......I am spoiled I have a design engineer at the shop who turns my napkin sketches into 3D files.....

These drawings have been offered to the public for more them 50 years & no one (until now) has found & fixed these issues.....I find this hard to believe........

The crank pin is an easy redo.....I'm for certain I'll use a section of ¼ drill rod held in place with 648 loc tite......

I might just toss the drawings on my engineer desk and have him redraw them.....

[CI]

I started studying one of my dad's engines after his death, with the intent of making drawings for it, and perhaps building a copy of it.
Unfortunately dad did not document any of his methods/techniques, etc.
He initially made geometric sketches on paper with pencil and ink, to get the mechanics to function.

I decided to take one of dad's engines apart, and measure each piece.
Then I drew each part in CAD.
In my ignorance, I just measured things with micrometers and such, and used dimensions such as 1.25532".

I created some nice drawings, and then as I started to attempt to build an engine, I discovered that the drawings were total garbage.
There were no standard hole sized, no drill size or clearance hole sizes, no bolt hole circles maintained, no alignment of holes between mating parts, etc.
It was a Chernobyl of a drawing set.
I did learn how NOT to draw a model engine though, so it was not a total loss.

There is a method to designing and drawing model engines, or rather there should be a very methodical method used.
I like to start on the inside and work outwards.
I learned the term "datum point", and how critical it is to establish one or more of these in the beginning.

I drew some of my dad's other engines in 2D CAD, and it was very difficult to get every dimension in every view exact, and difficult to propagate changes made to one part all the way through all the other related parts.
It was so frustrating that it drove me to learn 3D modeling.
I would never go back to using 2D CAD for anything other than sketching, and final drawings; for model engine work.

Some folks make the leap completely into 3D modeling, and work entirely within one program, but I find that difficult to do, so I straddel two programs.
I don't really consider it two programs (although it is two).
It is more like the sketch part of the 3D program, and the extrusion (3D) part of the program that I toggle between; all very transparent.
Autocad has a much better sketch program than any of the 3D modeling programs I have seen, although I am sure some would disgree with that (that is my opinion, and I stick with it).

Good luck.
If you get bold, dive into 3D modeling.
Many have made the leap, and the benefits to model engine design are enormous.
3D modeling has gone a long way to eliminate the problem-ridden model engine drawings of the past, since it uses a parametric approach, where things are theoretically connected and associated automatically (assuming someone flies the program correctly).
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[Jasonb]

I might just toss the drawings on my engineer desk and have him redraw them.....

You had better toss the castings onto his desk as well. When I redraw something that I have the castings for I will make sure I can get the part out of the drawings. Your engineer will have to flip a coin to decide which one of those dimensions where two are shown to use, he could easily choose one that won't work with the castings. Or in the case of the standards it would have been an option to adjust the O/A height so filler was not needed.

It also depends how you work, I would aim to make the bore a nominal size eg 1.125" and make the piston to fit which would be slightly smaller than 1.125" done by feel not built to numbers.

Also some of those clearances look quite large, the crank bearing is shown as 0.503" and the shaft as 0.500" Yes a steam engine is fairly forgivng but that seems excessive and likely to knock. Again I would use ground stock for the shaft and bore the bearings to fit again going by feel. Less than 6mm I tend to ream which would be H7 for bearing type surfaces. An H7 fit on a 1/2" shaft would be 0.5008" so a lot less than what is on those drawings.

For that size and style of crankpin I would go with a push fit and use a locknut on the thread to hold it all together. The crankshaft to crank arm joint would be a light press fit with Loctite.

I also wonder if these were originally cast in iron, that may explain the standards being undersize?

[55fairlane]

I might just toss the drawings on my engineer desk and have him redraw them.....

You had better toss the castings onto his desk as well. When I redraw something that I have the castings for I will make sure I can get the part out of the drawings. Your engineer will have to flip a coin to decide which one of those dimensions where two are shown to use, he could easily choose one that won't work with the castings. Or in the case of the standards it would have been an option to adjust the O/A height so filler was not needed.

It also depends how you work, I would aim to make the bore a nominal size eg 1.125" and make the piston to fit which would be slightly smaller than 1.125" done by feel not built to numbers.

Also some of those clearances look quite large, the crank bearing is shown as 0.503" and the shaft as 0.500" Yes a steam engine is fairly forgivng but that seems excessive and likely to knock. Again I would use ground stock for the shaft and bore the bearings to fit again going by feel. Less than 6mm I tend to ream which would be H7 for bearing type surfaces. An H7 fit on a 1/2" shaft would be 0.5008" so a lot less than what is on those drawings.

For that size and style of crankpin I would go with a push fit and use a locknut on the thread to hold it all together. The crankshaft to crank arm joint would be a light press fit with Loctite.

I also wonder if these were originally cast in iron, that may explain the standards being undersize?

I had already decided that most of the bearing clearances are way to big . And yes I'm using either drill rod or TG&P for all shafting & similar like crank pins & piston rod.
The crank pin i have my own idea of how to do it, I was simply adding that detail to the dumpster fire these drawings are.
The assembly drawing shows features & details not called out on the drawings.  I'm wondering if these drawings were made under the influence?  From now on the drawings will be referred to AS THE SUGGESTION

Quite a bit of the suggestion is up to interpretation,  luckily a gent in club has built this same engine, recently so tomorrow night I will pick his brain

[propforward]

My mobile phone is banned from this forum so I haven't checked in for a while. Of course I've seen your progress via text so I haven't missed out. Top work sir, always a pleasure to see how a professional approaches an engine kit.

Have to admit, I am tempted by the larger Myers engines. Then again I was also tempted by the Reeves beam engine and haven't done anything on that in a year.

Will enjoy following the build and seeing what else you uncover from the, er, plans.

[CI]

We could fix the drawings, but it appears they are copyrighted, and so they can't be distributed.

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[Jasonb]

You could always fix them and then allow Myers to use the new version. I have done that in the past giving my set of revise drawings to the casting supplier for them to do what they like with them. Or permission to make the revised drawings available on the net could be sourt from Myers, they may be happy with that as it could encourage sales but there is the chance of scratch builders just using the drawings. Everyone seems happy to complain about old poor drawings but few do anything about it.

As I said earler it would really need the person doing the revisions to have access to the castings, for example a slight reduction in height of the  standards could be made and associated parts altered to allow them to be cut from the undersize castings.

Some experience of engine building would almost certtainly be essential so that sizes/fits and suitable materials could be included by knowing what works and what does not. Ideally the person drawing would build the engine as a true test making any revisions to their drawings as they go along and not detailing things that can't be machined as we see on other redrawn versions of many old designs.

Then it is a question of how far do you go with revised drawings. I'd redraw the flywheel to something more in keeping. The use of the same casting from the Cretors engine with it's curly spokes just looks out of place to me and for the engines size a lot of the detail throughout is a bit "soft" or lacking.

[CI]

I could work through the drawings and rework/redraw/correct them fairly quickly, but they are not my drawings.
Do I understand correctly that someone bought the Myers designs/patterns ? or is Myers still involved ?

I think the logical approach would be to correct the drawings to match the original design intent.
Then the person who is selling the casting kits could correct the patterns in areas that are not correct.
It may mean that some castings would have to be discarded, but to approach it otherwise seems like opening a pandora's box.
The castings need to be made correctly; there is no excuse to do otherwise in my opinion.
If the castings are not right, then you are back to a lot of barstock building.

You an wrap tape and such around surfaces that need to be a bit larger.
There are some pretty simple methods to correct pattern dimensions.

I would draw the engine just as it was originally designed, and if someone wants to customize the design, then let them go purchase another flywheel, or whatever.
There are too many personal preferences to start trying to change the original design drawing, in my opinion, although I agree with the sentiment.

If the owner of the drawings (Myers or whoever) gives me the ok, I will redraw the drawings, with no guarantees; users assume all risks.
I know I could get it straightened out though.
I would do it for the benefit of the hobby.


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[Jasonb]

original design intent

This is an interesting one.

To me it looks like all the castings are aluminium (correct me if I am wrong)

For a display model that may only get a bit of running you can get away with steel shafts running in aluminium, or a dissimilar metal against aluminium. But for an engine that someone may want to have running all day at a show it would be better to have more suitable running pairs.

Now if back in the 70s the original intent was to cast in iron and bronze then the original intent is OK but the undersize casting and running pairs suggest a change to aluminium so you have shafts in aluminium bearing pedestals and ali to ali on the port face which is not good. That is a practical issue that affects running. Ali is OK for things like the bed plate and standards but not so good for the bearing pedestals unless you bore them out and sit bronze bearings. Or things like the cylinder end covers and crank arm which are usually left unpainted and ali will not look ideal

Altering patterns particularly if theu are on a match board with other parts could be quite costly, adjusting teh drawings to better suit the current castings would not involve the supplier in additional costs. As we have said before there is not a lot of money to be made suppling casting sets so any additinal expense is unlikely to go down well.

I'll leave out my other feelings about the overall design and detailing. Unless Fairlane wants to hear them and possibly take some onboard.

[CI]

Sounds like a bit of a mess, if all of that is true.
Not worth trying to fix the drawings if that is the case, in my opinion.
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[propforward]

A note about the drawings, these are hand done to the standard of the late 60's/early 70's . No tolerances given. No "finished surfaces called out. No reference dimensions. Study these carefully, even i a master machinist find these hard to follow at times.

Pretty typical model engine plans - haven’t yet seen a set of plans that could really be referred to as drawings.

Happily you have the smarts to figure it out though.
Hey my phone is letting me on the site again!

EDIT: Blast no it isn't.

Looking forward to the next installment. It's a beastie! Love it.