PM Research Engine Number 1

[Jo]

 

[propforward]

 

Anyway, lathe is fixt. Found a sheared pin in one of the drive shafts. 

Easy enough to fix, so that's something. And I have very quickly turned a piece of aluminium to replace the inboard head (not going to use the replacement casting just yet........). Will finish this after a bit of lunch.

[propforward]

OK, well, got it up on the mill and put the bolt circle in.



First time I have aligned using the conical center finder, and it really works well, just using your fingers to feel the alignment. A quick check with a micrometer in two directions verifies location. You all know this of course.





The bolt hole pattern aligns very well indeed with the one I put in the outboard cylinder head, which pleased me to no end. Good test of repeatability of the rotary table and mill set up.

Then machined the snout to size. Parting off was a gentle and slowly slowly approach.



Then cleaned up and brought to size with a knife tool.



Turned the part around, and brought the part to final thickness.





Pretty happy with the final finish on that.

One last step to do, which is machine a step on that face. Hopefully get to that tomorrow.

Much better progress today. I’m sorry my posts aren’t a bit more interesting, but I'm working at the very basic end of the spectrum of model engineering, in terms of knowledge, experience and skill, but I'm having a good time, and even having some success - if not very consistent success, so I think that counts for something. Still going to make this engine run. Although that day seems a long way off yet. 

[Johnmcc69]

No need to apologize for your posts Stuart, you're doing a fine job here. I admire your "stick-to-it-ness", & you're not afraid to just jump in & take things apart to fix it or improve things. Great job on the lathe repair, good thing you caught it before part of the broken pin got mashed in a gear..

 Keep at it!

 John

[propforward]

Thanks John, I appreciate the encouragement. There are so many really nice engines on here sometimes I wonder about even posting, but I'm always on the lookout for feedback for alternative approaches or better set ups.

Anyway, a bit more today. I made a simple collet to hold the snout of the spacer.





I could only take light cuts, but this worked, and the part was finished.



I have been wondering about getting hold of a 3" chuck, which I could then hold in this chuck (a 6"), just to make it easier to hold smaller parts. I don't know if that's a good idea or not.

Anyhow, then I went back to my cylinder. I made a mandrel to hold it, and set up on rotary table in the mill. Here I'm squaring the steam chest, to get the bolt pattern properly aligned.



I did have to mill chunks out of my "nut" to allow clearance for my center drill, but I knew I was going to have to do that, in order to maintain some overlap and clamp the cylinder well.



I tapped the holes by hand, but using the mill to keep the tap square. I can disengage all the gears so that I can turn the chuck easily by hand.



Family shot, such as it is. 3 parts and a red headed step child.  The bronze part that was ruined will go on the shelf marked "sacrifices to the god of machining".



And the cylinder head even fits.



I actually managed to get the holes for the outboard end lined up correctly. I thought I would have to skew them because of the poorly positioned steam ports this end.



It even fits the other end (although it doesn't go there). Just checking hole positions.



Well, that was good. Just got to tap the gland mounting holes and steam chest cover holes and the cylinder is complete. Now to decide which part to make next.

It seems like I only went to the shed 5 minutes ago, but 2 days seem to have slipped past. 

It does take me a long time to make parts, but there’s a lot of other things going on as well.

[MJM460]

Hi Stuart,

Please keep posting, we are not all experts, and all trying to learn as we go.  And there is much to learn from your struggles and persistence.  You seem to be ending up with nice looking parts.

The experts cannot tell us what we are doing wrong, or perhaps better expressed as better ways of doing it, if we don’t let them see what we are doing.  And it helps confidence if we find we are doing things well.

Regarding the chuck, as I understand it, it is quite difficult to remove a piece from a three jaw and put it back the other way around, or even the same way, for further operations.  My three jaw is a 6 inch one and it holds round sections and hex bar down a little below 6 mm.  So I machine one end, and if I have to turn the part around, I aim to have one of the machined surfaces an even dimension to fit one of my collets.  That gives much better centering, adequate for most purposes, though I am told still not perfect.  And a good set of collets is very good for holding and making small round parts, though I believe  other shapes can be obtained.

That said, I can see the power of using a smaller chuck as you suggest especially if it is suited to mounting on a rotary table. 

I will be interested to hear what you and others think about collets as perhaps an earlier purchase than a smaller three jaw chuck.

MJM460

[propforward]

I think you're spot on on all that. On reflection, I don't think clamping a smaller chuck in the bigger chuck really gains much. I do have a collet chuck for my lathe, but last time I used it I was extremely disappointed to see a visible amount of runout. I have since then trued it up - it has 4 adjustment screws to allow you to tweak run out against the back plate once installed, and I got the runout down to 0.0005" (approx) - as nearas I could measure it. Under 0.001" anyway, which I understand is normal for this kind of chuck. I trued it up once before though, and it went out of adjustment, so I will be interested to see if it stays true when I put it back on. Could it be that my threaded lathe spindle has some inherent inaccuracy that means I have to re true the collet chuck every time I install it?

I must investigate this and figure it out, because I really like the small form factor and superior chucking of the collets over a 3 jaw. This again is part of learning about set ups and machine capabilities. I often hear or read that a certain approach is preferred, but there is rarely discussion behind it about why, or about some finer details involved. So I just try things and see what happens, and adjust after that.

[propforward]

MJM, I did some investigation of my collet chuck tonight - this time when I mounted it on the spindle of the lathe it seems to have stayed true, which pleases me greatly. I took the opportunity to do some test machining just to test some set ups and surface finishes. Those I have detailed in my workshop log, just because I like to jump around all over the place on the internet.

As the engine goes, I didn't do too much, but did mull over the drawings, and did a test set up of the valve.



This seems solid, so I think this will be the next part made. Maybe get some time on it tomorrow evening.

And then I went rummaging around through the bits of material I have picked up from various shop throwouts over the years, and found this piece of 2" dia steel.



I don't know what alloy yellow is, but will see if I can figure it out. Do all metal stockists use the same identification colours, or is it stockist specific? Chances are this came from McMaster Carr, so I may be able to identify it. Failing that I'l just take a cut on it and see what happens. This is destined to become the crankshaft turning fixture.

[propforward]

Well, I looked at a few metal suppliers and they seem to use the same codes, which makes this a piece of 1045.

[propforward]

Tonight:

Sawing a 2" dia lump of what might possibly be 1045 steel, for use later on in the week.



Test cuts on a different piece of steel to achieve a reasonable finish on low carbon steel. This is 1018 steel as far as I can tell, because I've checked my records and I have never purchased 12L14 in 1/2" diameter, only 1018.





So I'm pleased with this little victory. Declaring this approach successful. Now to stop messing about with tests and make some actual parts.

And lastly.........



Milling a flat on the steam valve. Finish looks horrible here, but it didn't feel as bad as this looks. Maybe I should up the speed some next time. Never mind.

This going down to the shed of a winters evening for an hour or two here and there is brilliant. I haven't been able to do it in ages, good to sneak some mid week time in now and again, even if it's just getting things prepped for longer sessions.

 

[Kim]

Stuart,
That is a way better finish on 1018 than I ever seem to get!  Did you do any cleaning up with files or sandpaper there? Or was that the cut itself? I'd say that's quite good if so.
Kim

[propforward]

Thanks Kim, this was as cut - no post machine finishing.

It was SLOOOOOOOOOOOOW though. 50 rpm, lowest feed rate I have (have to look up the number), full flood coolant, and a brand new cutting tool, nice and sharp with a small nose radius, HSS tool. It's a purchased AR Warner cutting tool, rather than one of my hand made hacks, so the geometry was correct, and surface finish of the cutting edge was excellent, which I understand all add up on this kind of material. Depth of cut was something like 0.005" to 0.01".

[Flyboy Jim]

It's surprising what tricks the light plays on multiple cuts with an end mill on a surface like your Steam Valve. Like you say, looks horrible, but feels perfectly flat. I typically use a fly cutter on a surface like this to avoid this optical phenomena.

Jim

[propforward]

Absolutely agree Jim. Have not used my flycutter yet, so that will be one of the next things to test. I'm thinking of using it to flatten an aluminum plate for fixturing the chassis casting, so that will be a good intro to using it.

[propforward]

Milled out the pocket anyway. Got the size of the cutout within 0.005" on all sides, within 0.002" on depth and centered on the part within .002" each direction. Always good to see how close you hit the mark.







Thinking I'll polish up the main face on a surface plate before it goes in to service.

Then had a try at some flycutting. I have a piece of aluminum plate that I want to use for holding the chassis casting. I started sanding it flat a while ago, but it quickly became apparent that it was going to need a fair bit of material removal. So, I ground a tool according to the geometry I found on Toms Techniques website, and had a  try.







I don't know much about interpreting the cross hatch pattern, but I think this is not too bad. The casting no longer rocks on the plate, although I still have a bit more clean up to do on the underside of the casting to get it set down all around, but progress made anyway. Only problem being the cross feed motor died shortly after I started, which is a bit vexing, so I had to hand feed everything. Probably just a contact brush issue I think.