PM Research #4 - Quarter Horse Vertical Steam Engine

[Kim]

Nice jig! Looks like you've got things held very square, Stuart!

Are you planning to support the long legs more before you actually mill them to length?  Just seems like you might bend or break one of the legs without more support for them.  I seem to remember someone did that? (Tennessee Whiskey, if I remember right?)  But maybe if you're just really gentle and take very small cuts?

Kim

[propforward]

Hi Kim - that is exactly the plan. I have two very stout steel supports, one for each leg. On milling day I’ll re clock everything then bolt those in place. Even then I’ll go easy but they should damp out any vibration and keep the legs secure.

[propforward]

Hello again.

Had a great weekend - lots of reminiscing with a long time friend from back across the Atlantic. Wine was consumed, tall tales were told. Good times.

But after a fond farewell, I got a couple more hours in the shed, so managed to actually cut some metal.

I squared up the casting just a little bit more, and really got it in a very good position.

Notes sheet as I clocked the various sides and surfaces of the feet, and some reference measurements.



The conundrum is that there is not enough material on the bottom of the feet to completely clean them up and maintain the 0.44 reference dimension. However, there is .100 of stock on the cylinder end of the casting, and I'm only .03" deficient on the feet, so I can easily maintain the 11.810" dimension and fully clean the cylinder end and the feet. BUT - what does that mean for the whole engine? The bottom of the guide on this casting will now be .03" lower than nominal. As far as I can tell, that won't interfere with the connecting rod. So the .44" ref dimension will end up at .41". On balance I don't think that matters.



So on we go, I skimmed off .02" at a time using a 1" insert end mill. No problem at all.

Intermediate check of foot face to table. At this point I was right on nominal height to maintain the .44" dimension. You can see how much there is to still clean up.




This is where it is now.


I'm going to ruminate on that a bit. I think I may well leave it here - there is more than enough seating surface and I don't want to eat into my machining allowance too much for the opposite end.

Anyway, there it is for now. Next step, establish the center and drill the bolt holes. Not today though.

EDIT: On reflection, I've decided to fully clean up the feet, but not drill the mounting holes yet - so squaring the casting up for that operation was for naught, but no matter. Getting it true vertically was important. My reasoning is that the mounting holes need to be centered relative to the finished bore. It will be easier to indicate the finished bore than locate from the mounting holes, so I'll go with that sequence. After cleaning up the feet, next operation will be to mount on the face plate on the lathe and machine the cylinder end face and diameter, and then the guide bore. It's a plan.

[propforward]

A little bit here, a little bit there. I finished cleaning up the feet. The set up worked well, I'm very happy. The feet are flat and co planar within .001" which is plenty good. For anyone who wants to try this approach it works very well indeed, but don't even think about trying to mill those feet without some hefty supports. So the turning option per Stan Shire might be a bit easier in a lot of ways, but I was nervous about that. All in all, glad I went this route.


Absolutely no sign of any rocking when on the surface plate, or when tested on the base. 




Now giving the faceplate a light skim to get it flat for the next gripping installment.

[crueby]

Well done! Long legs like that are tricky things, great setup


 

[Kim]

Yes!  Very tricky! You had a very solid setup there, well done!   

Kim

[Michael S.]

Hello Stuart,
I might like that steam engine too. You are very good at machining the castings.
It's not as easy as the A-stand on a Stuart 10V. But as they say:
Many roads lead to Rome.

Greetings Michael

[propforward]

Thanks all, thanks for looking in and commenting, much appreciated.

I had some fun this weekend - made a little more progress.

I finished skimming the faceplate:



Then I got the frame casting mounted and trued in. I just used my fixture from the milling to get the as cast bore mostly true, then spun the faceplate by hand and watched the external features to make sure everything would look true.




I needed five pairs of hands to get it all set up, but got it there.



Then I drilled a center in the end of the fixture, to allow the use of a live center for extra support.


Then turned the head end OD to size:


After that I faced the part to length. I added a cross hole to the aluminum fixture so that I could clamp it to the part, again allowing the use of the live center for support.



That all went really well - so I just kept going. I had obtained a 3/4" X 10" long boring bar, so I got that all set up and worked on the thru bore. This is just setting up the boring bar and making sure I allowed enough length to get through:



Then I set up the steady rest to give the casting extra support. I had to shorten the 3 fingers in order to fit the part in.



Then I bored it out - .03" at a time to take out most of the material, pausing every few cuts to measure the ID.











And there we have it!



So far so good. The bore came out a little oversize which is annoying - that was due to my not allowing enough for the final spring cut. That bar flexed more than I realized. Lesson learned. This is OK since I will match the slider to the actual bore, but it's vexing because I am trying to hit tolerances, which I am doing very nicely in general, but this was a new situation. Should have tested the spring cut while machining out the stock. But I know better for the cylinder.

Anyway, there we are, progress and a very enjoyable shop session. Next up will be to add the bolt patterns to this part. 

[mikehinz]

Stuart, I like your process!  I think it worked out well for you.  Those parts are tricky and IMO you came up with a great process to get them done.

Again, great work!

Mike

[propforward]

Thanks Mike! I feel good about how this is progressing. Thanks for your kind words - it means a great deal.

[Kim]

Very nice setups, Stuart!   I really like how you did this, and how careful you were at each step to get a good solid way to hold that spindly casting!

I understand the chagrin at missing the tolerance you were aiming for, even if, in the end, you can make up for it.  It's still frustrating.

But the part looks beautiful!  And nobody will know.  You'll even forget once you see it all running!

Kim

[Michael S.]

Hello Stuart,

I thought long and hard about how I would have done it. But your way is perfect.
I also know from myself that one gets annoyed about a mistake for a while, but that passes 😁

Michael

[propforward]

Thanks guys!

I am doing a much better job of thinking through the set up process, and also understanding the starting component / casting than I did when I started in this hobby, so consequently the set ups are working out a lot better. I'm also having so much more fun with it. It was really enjoyable working on this over the weekend. I have high hopes for the finished engine!

Although I'm still miffed on the oversize bore, I am very pleased with how the bore is perpendicular and uniform to the end face, and how the end face is parallel to the feet. This will all work very nicely with the other engine components and is how I aim to get to a smooth running engine. That's the goal anyway.

As always, thanks for posting, all comments and advice appreciated!

[propforward]

Some more shednanigans today - and got the frame finished.

Bolted the frame to the table, and then swept the OD and the ID to find the center. The ID and OD appear concentric within a few tenths as best as I can figure it with this method. I could not readily measure runout of either one, maybe a half a division on my indicator, so 0.0002 approximately. I'll take that I think, given that the mill spindle is likely not better than that anyway.




There was some balancing to be done between the bore and the outside features, squaring the part up, and then I took some reference measurements from the DRO on the feet, so that I can set it up the same way when turning it over to do the feet. Of course, what I should have done when I cleaned up the feet was dusted off the outside features to make a flat reference plane for such set ups. Didn't think of that until I was done drilling the holes on the head end, but what I have done will work.

I thought I'd make use of the DRO to program the bolt pattern.



Very nice graphics on this model for doing such features.


So that was all very well, but when I looked more closely at the drawing I realised that the bolt pattern is not actually equi spaced. Glad I checked before drilling. So I abandoned the bolt circle program and just went from the linear dimensions on the drawing.

I didn't quite have enough clearance to make use of my drill chuck so all holes were drilled using R-8 collets.



Then turned the part over, balanced it to match my earlier measurements, and then found center. This time I could use my center finder which I find is a bit quicker than sweeping with a test indicator - although I'm sure that's a matter of practice. However - this tool is just a lot of fun.



Anyway - then it was a case of drilling out the feet to match the drawing - 4 1/4-20 clearance holes. Simple enough. The PMR drawings give pretty generous clearance holes for everything, which I expect is to aid fit up later, but I have opted to use more standard clearance holes and keep things a little better aligned (as long as my machining is accurate enough). We'll find out in due course about fit I guess.

At this first stage fit is just fine - the screws went in with no binding at all.


I intend to make studs for this engine, I think they will add a lot to the appearance of the final build, but I'm using the supplied fasteners for now for fit tests.

Now to decide what to make next. I feel like turning some things, so maybe some of the glands. Don't know - need to peruse the drawings.

[samc88]

Looking great Stuart