# PMR Mill Engine 3A



## DOC123 (Nov 22, 2010)

Dear All
I am only a beginner at making engines. I have successfully made a sterling engine and a wobbler noted here
http://www.homemodelenginemachinist.com/index.php?topic=11053.msg120953#msg120953
For my 3rd attempt I am making a PME 3A mill engine from a casting kit that I bought at the same time as the wobbler.
I haven't tried to take pics as I'm going before but will give it a try.

The kit comes nicely packaged with all the needed parts including screws etc. It is in imperial measurements that I find confusing but I can easily convert them. All of my taps etc are metric so I will just adapt most of them. The exception is that most of the screws in the kit are 5-40 so I bought a tap to match.

I started by mounting the base casting on my little mill and evened the base. I then turned it over and milled the crosshead to height and drilled the 4 holes.


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## DOC123 (Nov 22, 2010)

Next step was to mount the base on a right angle bracket and face and drill the end where the cylinder will sit. (no pic) 

I then attacked the cylinder. First I made it a vertical as I could in my milling vice and faced one end. Using that end as a reference I mounted it in a 4 jaw and faced the other end on the lathe. I then drilled it and bored to 12mm. I only have 12 and 13mm reamers so that determined the size possibilities. I then stuffed up reaming it with the 12mm reamer so had to enlarge the hole to 13mm.
I then returned the part to the mill and drilled the valve hole and reamed it to 6mm.
Next step was making the holes for the steam ports. These were just done on the mill.





The angled holes were first milled with a 3mm end mill and then drilled through to the matching hole.


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## DOC123 (Nov 22, 2010)

Next step was making the inboard head.
This is a little casting that isn't easy to grip on my little lathe.
I gripped it by the protruding end in the 3 jaw with a washer between the jaws and the part. This made it possible to true up the outside without hitting the chuck. I then and faced it and made the step to neatly fit the cylinder. I then drilled a 1/8" hole in it.






It was then turned around and pushed up against partly closed jaws and held in place with a live centre in the tailstock. I found that I couldn't use the dead centre as it is shorter and it fowls the toolpost.
This allowed me to machine the outside to fit in the hole in the base casting and to reduce the thickness of the head.






I then had to move the tailstock away to drill the part out. I carefully put it inside the jaws and drilled and tapped it to 6mm. This worked well but made little marks on the outside of the part. I may try again with a piece of bar stock.


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## NickG (Nov 22, 2010)

Nice work Terry,

I came across a supplier for PM Research engines the other day and they seem well priced. DId you go for the iron and bronze version of the 3A - I quite like the look of the larger engine which is about $108. The only annoying thing is the large postage cost I'd have to pay and import duty to get it into the UK - it still works out cheaper than stuff on offer over here though.

Do the kits come with instructions? The quality of the castings looks pretty good?

Nick


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## b.lindsey (Nov 22, 2010)

Looks like you are off to a great start Doc. PMR does a nice job with their casting kits and are great folks to deal with too. Keep us posted on the progress.

Bill


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## DOC123 (Nov 22, 2010)

NickG  said:
			
		

> Nice work Terry,
> 
> I came across a supplier for PM Research engines the other day and they seem well priced. DId you go for the iron and bronze version of the 3A - I quite like the look of the larger engine which is about $108. The only annoying thing is the large postage cost I'd have to pay and import duty to get it into the UK - it still works out cheaper than stuff on offer over here though.
> 
> ...


Dear Nick
This kit is the aluminium one that I bought as a first attempt at machining.
I have since bought 2 cast iron and bronze engines from here
http://www.modelmachinist.com/index.php?osCsid=4810bdc00ba248836ad70f78b2412d3c
as the Aus dollar is high at present. Even with substantial postage costs it is still cheaper than buying similar items locally. I will finish this before tackliing the new ones.

The castings seem to be pretty good with no obvious holes and not much flash.
Only limited instructions come with them but very detailed drawings are provided and I am working from them.


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## NickG (Nov 22, 2010)

Thanks for the info Terry, can't wait to see it progress.

Nick


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## DOC123 (Nov 28, 2010)

A little bit more progress.
The next step was to drill the holes in the cylinder to mount the inboard head. I first marked out the holes on the inboard head and drilled them to size. I could then put the head in place on the cylinder and centre dot the position of the holes. I then drilled the holes in the cylinder and tapped them.





The next step was to make the outboard head. It is only thin so I decided to only clean up the inside and leave the outside as the raw casting.
It was held in the 3 jaw and faced to size to make it just fit in the cylinder.






I then had to drill the 4 mounting holes. I decided to do them all at once with the cap on the cylinder. I was able to hold it on the mill table with 2 clamps and still get enough clearance to drill the holes.






The end cap holes needed to be enlarged to allow the screws to fit so I mounted it on a bit of scrap ali and enlarged the holes. Perfect accuracy isn't needed and it worked well by just eyeballing the drill above each existing hole.


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## DOC123 (Nov 28, 2010)

The next bit I made was the piston rod but I didn't take any pics of it. I decided to make it out of 3mm silver steel rod rather than the brass supplied as I only have metric dies to make the threads. It is a simple rod with threads on each end. I also made the little nuts out of brass hex.

I then tackled the piston. It is made from brass. I first drilled the 2.5mm hole in the middle and bored it out to take the 2.5mm hex nut that I had made for the piston rod. I made the bored end a bit too big. The result was that I couldn't make a deep enough groove in the cylinder to take the first teflon ring. The second groove was made deep enough.
To compensate I carefully thinned the teflon ring with a craft knife so it fits the shallower groove.
The outside was turned to fit the 13mm cylinder and then parted off.






This is it for now. Hopefully I will get more time tonight to do more. I just have to remember to take more pics as I'm going. ;D


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## DOC123 (Nov 30, 2010)

I was able to do a little more to the engine last night.
I have been working my way down from the cylinder making the parts as I go. The next part is the cross head. As I mentioned in another thread I have misplaced or never received the bit of brass for this part. I decided to make it out of cast iron as I don't have any brass thick enough. This will be my first attempt at machining cast iron.
The cast iron I have is a 30mm rod so I cut a small disk off it with a hacksaw. I was amazed at how soft it is compared to steel that I have cut in the past.

I put the disc in the lathe and faced one end to create a flat surface. This was then clamped to the mill table. I them reduced its thickness down using an 8mm end mill leaving the bit under the clamp unmachined.






When it was the correct thickness I just cut the thick bit off with a hacksaw.
I then put it in the vice on the mill and cleaned up the sawn edge. I then rotated it 90deg and milled another face. This gave me 2 edges to measure from and I marked it out.
I then made it the correct width to fit the slide where it sits on the engine base.
It was then turned 90deg again ready to mill a slit in it.






Using the same 8mm endmill I created the outside grooves.
The centre slot is suppose to be 1/8" but I decided to just use a 3mm 2 flute endmill and not try to expand the hole to 3.18mm.
The part is 19mm wide. I wanted to have the slot as close to central as possible so I measured from the edge of the piece using an edge finder and advanced the carriage 9.5mm. This seemed reasonably accurate so I made the slot with the end mill. It measures within 0.01mm of centre.






I am yet to drill the holes needed but the mostly finished part is pictured here where it will slide on the engine base.


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## DOC123 (Dec 7, 2010)

A bit more on this engine.
My first stuff up.
Having made the cross head from cast iron I broke it. As pictured above it still needed to be drilled. I marked it out and centre punched it. I have one of those auto punches that you just press on the item and a spring releases it. Well I used it on the side of the crosshead and one of the arms broke off. This meant going back to the start and remaking it. This time I drilled it before I milled out the centre. The only good news is that practice makes perfect and the new one is a better fit than the first one.






The next step was to make the little retainers that hold the crosshead in position. They are small castings seen here held upside down in the mill vice. They have a casting pip on them and the bottom needs to be milled flat.






I just milled to base level.


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## DOC123 (Dec 7, 2010)

The next step is to make the little spacers to fit under the crosshead retainers.
These are made from brass rod. It is just drilled out to 1/8" on the lathe and turned down to a reasonable size. I then parted them off to length. This left a little metal that needed to be faced off. I did this carefully on the lathe so as not to reduce the length of the piece as I had parted them off to the same length.






Here are the completed spacers and the crosshead retainers ready to be drilled.


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## NickG (Dec 7, 2010)

Nice work Terry :bow:, sorry to see the cracked cross head but all sorted now. Does look a nice kit, I could be tempted by one of these PM research kits.

Nick


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## Kmot (Dec 7, 2010)

This is an awesome thread! I have looked at those PMR casting kits and wondered about them. This is the first time I have seen detailed machining photos of one of these kits. I am learning a lot from your photos! Thm:


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## Deanofid (Dec 7, 2010)

You're going right at it Terry, and looks like you're doing well. 
This kit is the first casting kit I ever built, a long time ago. The kit was under $25 at the time, so
it's been a while. Mine still runs like a champ after many, many hours on it. A nice little engine.
PMR puts out a good product. I'm working on their #7 now, and they're all good quality castings.

Good luck, and keep up the good work!


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## NickG (Dec 8, 2010)

Dean, I like the look of the No 7 and No 1 - are you doing a build log? They do seem better value than Stuart's and the like, even with the import duty and large shipping costs to UK.

Nick


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## Deanofid (Dec 8, 2010)

Nick, I'll do a build log but won't start it until I get more done, (and I have to ask the owner. I'm building
it for someone else.)
I have a good deal of the work on the base done, which is cast iron. One of the best quality iron castings
I've ever worked on. 

Dean


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## DOC123 (Dec 11, 2010)

Thanks for the encouragement guys.
Taking photos as I go is certainly making me think more about how I machine the bits of this engine.
Next step was to make the connecting rod. This is a thin casting that needed to have both ends milled to clean up the casting and give a smooth surface as simple bearings.

I did this on the mill and then drilled the holes in it. The plans ask for a 43 hole in the thin end but after I had done this I found that the pin supplied doesn't fit through the hole. With persuation  it will probably expand the hole enough to be a very tight press fit but I would never get it out again. This may be OK when I assemble the engine. The other option is to enlarge the hole and use loctite to keep the pin in place.






I have just been making the bits in order from the piston out so the next part was the crank bearing. It is made from CRS and is a simple bit of machining on the lathe. The kit has a 5/8 round bit of CRS to use for the bearing and for the eccentric hub. I decided not to use this but used a smaller piece of steel that I had rather than machine lots of metal off.


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## DOC123 (Dec 11, 2010)

Next came the crank.
It is a casting with a big casting lug on it. I just held it in the 3 jaw and faced it flat. 






I then drilled out the centre. This became my second stuff up for this engine. I picked up the wrong drill and made the hole too big for the crankshaft. It is 1/4" CRS and the hole was 6.5mm  -about 0.2mm to big.






To solve this I drilled it out further to about 8mm using a little home made small boring bar made from an old drill. It is too long to be very stiff but as long as I only take 0.025mm cuts it cleans up the hole very nicely. I only have metric 6mm and 7mm reamers so this had to do.






I then made a brass insert from a bit of brass I had already. I bored its hole to a close fit for the crankshaft and made the outside of it a tight press fit with the crank. The finished item is here with the crankshaft.






Now I just need to get more time to work on this model.


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## NickG (Dec 11, 2010)

You're getting on well with this Terry, great work.

Dean that's good to know and I'll watch out for it in case you do a log.

Nick


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## rleete (Dec 11, 2010)

Nice save on the bushing/spacer. You can tell people that it's there for a bit of color contrast, and it's in the plans!


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## zeeprogrammer (Dec 11, 2010)

Better than a save. I like the look. I'll have to remember that.


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## Deanofid (Dec 11, 2010)

Good save, Terry. We all make a boo-boo now and then. It looks good!


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## DOC123 (Dec 15, 2010)

I've done a bit more on this model.
The crank was essentially finished but I needed to face the oposite side of it. I couldn't find a simple way of holding it on the lathe so I just held it flat on the mill and evened the top with an end mill. I then held it sideways and drilled and tapped a 3mm hole for grub screw.







Next was the eccentric insert. It is made of CRS and is probably the most complex bit of machining in this model. I held it on the lathe and made it a close fit to the brass eccentric ring that goes around it. The brass ring came supplied. It only needed to have its edges chamfered.


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## DOC123 (Dec 15, 2010)

It then needed to have an eccentric hole drilled in it and machined off centre to give room for the grub screw. This was achieved by holding it in the 4 jaw chuck. This was a problem because of the design of my old style 4 jaw. I couldn't get a jaw close enough to the centre of the chuck to hold itt off centre enough. I overcame this by taking a washer off the nut on the back of the jaw. This gave me about 2mm more travel towards the centre- just enough.






It was then drilled and reamed to size.


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## DOC123 (Dec 15, 2010)

Once the hole was bored to a close fit on the crankshaft I parted it off- by far my least liked process on the lathe.

I then held it in the mill and cleaned up the parted off face. I didn't want to hold it in a chuck on the lathe as I didn't want to damage the outside surface.






The finished pieces with the eccentric rod partly made.






This is all these parts assembled and roughly in place on the model.






There isn't that much more to go- the flywheel and the valve. Hopefully a few more nights and I will have it finished.


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## NickG (Dec 15, 2010)

Coming along nicely, nearing the finish line then! are you going to paint it?

Nick


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## b.lindsey (Dec 15, 2010)

Nice job on that eccentric Doc. The finish line is in sight 

Bill


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## Deanofid (Dec 15, 2010)

You're getting the best of it, Terry. 
Next time you need to turn something like that eccentric, and are worried about the chuck jaws
making a mark, cut a small strip from an aluminum can and wrap it around the piece before you
chuck it up.


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## DOC123 (Dec 16, 2010)

NickG  said:
			
		

> Coming along nicely, nearing the finish line then! are you going to paint it?
> 
> Nick


Thanks guys.
I do plan on painting some of it- at least the base.



			
				Deanofid  said:
			
		

> You're getting the best of it, Terry.
> Next time you need to turn something like that eccentric, and are worried about the chuck jaws
> making a mark, cut a small strip from an aluminum can and wrap it around the piece before you
> chuck it up.


I thought of this but I would still be grabbing it by a very narrow ring of steel. I thought it would be difficult to keep it square in the jaws as I tightened them with the ali around the part.
The mill worked OK.


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## DOC123 (Dec 18, 2010)

Not much more to go.
The next part I made was the connector for the valve.
It is a simple bit of machining in brass apart from the part being pretty tiny. It has a small hole drilled in it to connect it to the valve.






The valve is made from brass and was turned on the lathe. The photo shows it before being parted off. It was then turned around in the chuck and drilled partly through.






It then has a little hole drilled in it to connect the gap in the valve with the hole I had drilled along it's length. I like this design as it allows the exhaust steam to exit out the end of the valve.


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## DOC123 (Dec 18, 2010)

The final part to make was the flywheel. It is a substantial casting made from aluminium. 
I just held it in the chuch and machined the outside and faced 1 side.






It was then drilled out and bored to size to fit the crankshaft.
I then turned it around and faced the other side.






The final step was to drill a hole for a 3mm grub screw but holding it at an angle in the mill vice.






Now to wash it all up to remove any oil and paint it. This might take a bit more time compared to the machining ;D
Hopefully I will post an image of the finished engine soon.


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## b.lindsey (Dec 18, 2010)

It's still coming along great Doc and aside from the cleaning,painting, and polishing its almost a runner. I have no doubt that it will run beautifully, and looking forward to seeing that!!

Bill


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## Deanofid (Dec 18, 2010)

Yes, I'm kind of getting excited to see it run, too. You've done a nice job, Terry. Hope the painting goes well!


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## NickG (Dec 20, 2010)

Nice work Terry, can't wait to see the finished assembly.

Nick


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## DOC123 (Dec 26, 2010)

I had a little break form this engine as Christmas intervened. I have put it together and painted it. The paint job needs work as I have chipped it in places when I assembled it. I also need to make a wooden base.
It runs nicly on compressed air. I will make a video soon.
It has been a fun learning experience taking the photos as I go and I may do it again with my next build.
The colour is actually a burgundy colour more like the first photo. The second photo has a colour cast from me underexposing it trying to get more depth of field.










Thanks all for the kind words with my postings.


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## b.lindsey (Dec 26, 2010)

It looks GREAT Terry! A nice wooden base will set it off nicely too. By all means please post a video when you can. Its been a fun thread to watch :bow:

Bill


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## arnoldb (Dec 26, 2010)

Terry, your build came out great! - Very well done indeed - Congratulations! :bow:
Looking forward to the video as well ;D

Kind regards, Arnold


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## Deanofid (Dec 26, 2010)

Super job, Terry! I like that dark paint job, too. Mighty fine.
A video would be great.

Dean


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## Maryak (Dec 26, 2010)

Deanofid  said:
			
		

> Super job, Terry! I like that dark paint job, too. Mighty fine.
> A video would be great.
> 
> Dean



Me too :bow:

Best Regards
Bob


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## DOC123 (Dec 26, 2010)

I'm happy with the engine. Thm:
I connected it to a little compressor last night and tried to video it but the compressor makes too much noise. I then tried jury rigging it to a little boiler. There were a few leaks with the piping due to my crappy soldering but it ran well.
[ame]http://www.youtube.com/watch?v=nGqzMWjFm38[/ame]


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## Kmot (Dec 27, 2010)

It's awesome!! Sounds fantastic when running!! Thm:


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## zeeprogrammer (Dec 27, 2010)

Nice engine and nice job.
How do you control the speed?


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## DOC123 (Dec 27, 2010)

zeeprogrammer  said:
			
		

> Nice engine and nice job.
> How do you control the speed?


Thanks. Simple answer is that you don't.
It was directly connected to the little boiler and I was heating it with a propane torch as a fast way to test it. Removing the flame when I stopped videoing made the engine stop.
If is a simple engine with no governor so speed depends on the amount of steam I deliver. I suppose a little valve could be put in the line but I don't own such a thing yet. ;D


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## ozzie46 (Dec 27, 2010)

Excellent job Terry. Running on steam. Impressive!

 Ron


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## NickG (Dec 29, 2010)

Nice work Terry,

It looks spot on and great to see it running on steam too, so many aren't, including mine :bow: You must be proud of that - any ideas on your next one yet then?!

I hate to go all health and safety here but think it's got to be mentioned. I know it's only for test purposes and you know what you are doing, but not everybody that sees this will know what they are doing. That boiler should have a safety valve, because you don't have an in-line valve it shouldn't be an issue, unless the engine was stopped and made the pressure back up.

It's been posted many times but not everybody realises how dangerous these little model boilers can be - this video illustrates it nicely. This one had a safety valve but these idiots were messing around trying to get more pressure. The expansive forces when pressurised steam hits the atmosphere is quite amazing. These guys can consider themselves very lucky!

[ame=http://www.youtube.com/watch?v=0R348vGkjyw]http://www.youtube.com/watch?v=0R348vGkjyw[/ame]

Nick


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## Deanofid (Dec 29, 2010)

Runs great, Terry. You've done a really nice job there!
Thanks for the vid.


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## steamer (Dec 29, 2010)

Nicely Done Terry!

Dave


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## DOC123 (Dec 29, 2010)

NickG  said:
			
		

> Nice work Terry,
> 
> It looks spot on and great to see it running on steam too, so many aren't, including mine :bow: You must be proud of that - any ideas on your next one yet then?!
> 
> ...


The boiler does have a safety valve. Pressurised with air it goes off at about 10psi. It is in front of the steam outlet pipe in the video.
cheers

Terry


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