PM Research #4 - Quarter Horse Vertical Steam Engine

[propforward]

Well, on we go then.

There aren't too many build logs of this engine on the net. Stan Shire did a very nice one on this forum, which you can rest assured I will refer to often because it is excellent.

I have a couple of goals beyond making a working engine on this one - well not beyond it, integral to it.

1. Do not scrap a part (not actually that important, but something to strive for).
2. Make parts individually "by the numbers" rather than transfer punching features. Now - I don't consider transfer punching and drilling "wrong", this is simply a measure for me personally of how well I am understanding the parts, the drawings and the machining process. It should be possible to make parts that fit together by making them individually if the tolerances and methods are understood. One exception - I will likely drill and ream the crank bearings mounted on the base plate.

In my opinion the PMR #4 is not an especially elegant engine, but it is a replica of an actual work horse engine - a full size replica, rated at 1/4 horse power. So the larger physical size made it very intriguing to me when I bought the casting set in 2015, and now it is time to move forward with it.

I suspect that being a bit larger it will be less tolerant of alignment errors and such, but in any case I am determined to put everything I have learned so far into practice (rather than learn the same mistakes again  ).

Here is a look at the supplied parts.



It's quite a lump. Here is the cylinder casting, and I am no waif I can assure you weighing in at (too much) and standing (about this high).







Flywheel is a decent chunk too.



Anyway, the engine itself is actually a fairly straightforward design - but holding the various parts will present some challenges I'm sure. I've had the drawings on the wall of my office at work since the start of the year, so I can peruse them constantly and think through the build a bit, and that has helped me formulate a general approach.

I'm starting with the base. This is because it is a reasonably simple part, but also because the base will go on to become a fixture for machining the bearings in due course.

I started by putting it on a surface plate, and checking flatness and parallelism. It rocked a bit on the surface plate, feeler gauges suggested about 10 thou rock underneath. The top surface was flat within .05", which I think is reasonably good for a raw casting.



Where I didn't do so well on my last engine was not understanding the starting castings well enough. I'm determined to measure and understand the castings better this time so that I can balance the machining and not run out of machining stock, as well as keeping machining balanced on each surface.

I mounted the base on the mill and shimmed it to get it reasonably level.



Then dusted off the top. I didn't completely clean it up, just about 30 thou to get it to sit flat.



Here is the drawing, on my trusty rolly cart. Nice to have it presented so that you can see it clearly without tools piled on top of it.



Anyway, after dusting off the top surface I flipped it over and skimmed the underside.





Had to reset the clamps after milling part of the base.



I checked the top surface for flatness after this step - and it is flat to .0015". I am pretty happy with that to be honest.

Then back on the mill to finish clean up of the top surface.

This time when setting up, I squared the part up using my newly repaired interapid DTI. This is because I'm going to drill and tap the holes in the base as well as do clean up.



I touched off on the front edge first, and got that square (completely square according to my DRO). I do not run the DTI over as cast surfaces - I touch on one spot, set zero, back off and move down, then touch off again. I chose the front edge arbitrarily. Basically, you have to trust SOMETHING on a casting, so I chose the front edge. After squaring the front edge up, I touched off on two positions on the other 3 edges to check them. The right edge was withing .001", the left within .0006" and the back edge within .005". Not far enough out to warrant any balancing acts - this is plenty good.

So I finished tightening the clamps, and skimmed the top surface clean.



And that's where I am.

Next step will be to drill and top the holes in the top surface, then I'll re clamp and drill the holes in the bosses currently being used to clamp the part.

Off and running! 

[crueby]

Great start on a big engine. Got a big bowl of popcorn to match!


 

[MJM460]

Hi Stewart,

Great start on the new engine.  Must be very satisfying to have such a project to prove out your new DRO installations, not to mention the other lathe improvements.

MJM460

[Sleddog]

I’ll be 3-4 rows back, sitting comfortable & watching 🍿

[tevans9129@charter.net]

This is fascinating, and educational, for a newby, thanks for posting and I am looking forward to the next installment.

[Dan Rowe]

This will be fun to watch.  I hope your air compressor is up for the challenge.

Cheers Dan

[propforward]

Thanks everyone for looking in and following along. I appreciate the interest very much, and any and all critique / suggestions along the way gratefully received.

MJM - absolutely, it is very pleasing to see tweaks and mods to the machine tools bearing fruit. I just swept the surfaces of this part and they are flat to within half a thou, and no sign of saw toothing from the face milling process - so that means my mill is trammed reasonably well and pleases me very much.

The next stage was pretty simple, just drilling and tapping holes. Not very much to say about it, the main point I guess is that to keep everything as visually symmetrical as possible I established the center lines in X and Y axis by using an indicator mounted in the spindle. A technique I got from Joe Pie on youtube, and who's channel I thoroughly recommend. Not that this is a unique to him approach, just one I wasn't practiced in using, and I must say I do like this for finding center on awkward parts where an edge finder doesn't work out so well.

Simply rotate sweep and find the high spot of your indicator on one side, set zero, move to the opposite edge, find the high spot, move the table to get zero on the indicator, then move to half the value of the measured dimension and there is zero. Not a very good explanation - best to just watch the man himself if you aren't familiar with this technique:

<a href="https://www.youtube.com/watch?v=RygvDDyA2X4" target="_blank">http://www.youtube.com/watch?v=RygvDDyA2X4</a>

Anyway, couple of pics


Having done that, it's a matter of center drilling locations, drilling the pilot holes and then tapping. I have taken to using a spring loaded tap plunger because it does make getting straight threads much easier.



I also set about the part with my files and cleaned it up. Should have done that first - note to self for the next parts.


I reckon I could have made this part in at least 2 less set ups, but I'm less concerned about that efficiency right now, and mostly focused on part accuracy.

Anyhoo, speaking of next parts, the column is up next.





First thing will be to spend some time with the files on it, and in the meantime I'm mulling over the approach for it. Stan Shire faced the bottom of the feet in a lathe, using a mandrel to keep everything square to the cast bore. I'm more inclined to either face mill or side mill the feet flat, but also using a mandrel to maintain squareness to the bore. I think side milling may be difficult because of the size of the feet, so I may have to make up a jig to clamp the feet and stop them vibrating / deflecting when face milled.

More to come!

[propforward]

This will be fun to watch.  I hope your air compressor is up for the challenge.

Cheers Dan

Just the excuse I need for a new compressor. 

[Baltic]

I will be watching this build with interest, will be some interesting challenges, what a beast, how much does the kit weigh. I looked at this engine a while ago, would have to re-mortgage the house to pay for shipping to Aus, 
Gary

[mikehinz]

I'll also be following along!   One of these days I'd like to attempt a larger engine also!

Good work so far and good luck as you progress!

Mike

[john mills]

looks like a nice sized engine
why would you set to the cast bore  its just a cored hole  to be machined it should be set to the out side of the casting that is unmachined
that need to look right the bore is machined so will be concentric if it is a bit off as cast it does not matter if there is enough metal to clean up to size and will be correct with the unmachined part .the machining will make it true to the out side the machining may be uneven to start
with but that does not matter it will come true as you machine it cores often won't be perfect in the centre and can often be off by what looks
like a big amount  it is ok as long as there is enough metal to kleen up to size and true to the unmachined parts. which you should have set it up to.
   John

[propforward]

Thanks everyone for your support - really good to have you all following along.

Baltic - not sure on the weight of the engine - it's plenty massive though. 19 inches tall, 1-1/2" bore with a 2-1/2" stroke.

Mike - thanks so much for following it means a lot.

John Mills - you have a solid point, and I've been thinking about that. One reason I was going to set up off the cast bore is that I have seen two builds done that way very successfully. However, it pays not to take anything for granted. Your comments about centering everything to run true and look right based on the externals are spot on.

Here's what I am now thinking - make a tight fitting mandrel for the bore and set up off that initially. Then indicate the outside of the casting to make sure that is also true, and adjust as needed. Some initial measurements show that the as cast bore is quite close to concentric with the outside, within about .030". It could also be that the mandrel actually gets in the way of keeping the part true. I'll try a few things with the set up and see what makes the most sense. This is not a part to rush the set up on, it's worth taking the time to get it rock solid.

Looks like I have enough travel to stand the column upright for machining.



So I started making some restraints for it. I don't want those legs shaking around as I try and clean up the feet.





I have to try a couple of approaches to clamping it, but I think I'll just clamp each leg to its own support bracket. I could equally make a spacer block to go between the legs but I don't think that's needed. On the other hand, might be even more rigid.

A company I was working for 14 years ago throw out those steel bars and blocks, as well as some other similar sized pieces, so I nabbed them with their permission. Glad I did! Glad I learned some rudimentary welding as well, it's super handy for making fixtures.

I personally think I'm getting better at it.



Spent a little quality time with the column and my dremel getting it fettled, but I feel good about this plan, I think I'll be able to get the part set up during the week and maybe have a first pass at machining the feet next weekend. 
 

[samc88]

Great work Stuart, looks a good sized engine. Do you follow Blondihacks on youtube? She has got a build series on one of these currently on the go

[propforward]

Hey Sam thanks for checking in. Cool that she’s building one as well.

[propforward]

Progress is slow as usual, but I did get some time today. I took the day off because a friend of mine is coming to visit from the UK, so I had a few hours before needing to go and collect him from the airport, so had some fun getting ready for the next step.

After measuring the body casting carefully I established that of course there are no really straight features on the outside to easily align from, but it appears that the as cast bore is quite straight in the casting, if not round. So I decided to go with the mandrel approach to holding it after all.

Here is a piece of 2" round bar I had on hand, just long enough to do what I want to do.



I turned down most of the diameter to get a really close fit in the bore.



After making that working diameter, I mounted the 4 jaw chuck, turned the bar round and held it on the machined diameter, and clocked it in to be very true, then faced the opposite end square.





I finished the boss OD as well, just in case I need to indicate it later.





So the idea is to clamp the part to the table, with the fixture mandrel forcing the part upright. I did clamp the fixture to the table and ran my indicator up and down the shaft using my DTI in the machine spindle, and the part is very straight, plenty accurate enough for this job.



So then I got to work mounting the part. This took some time.



I first clamped the top of the mandrel fixture to hold it in place and upright, then lightly clamped the casting on the head end. First I squared it up by touching off on the far side of the casting on each of the two feet.

After that I clocked the sides of each foot, inside and outside to see how true they were. I also measured the width of the feet to understand any asymmetry. Using a combination of my height gauge and the mill DRO, I touched off on the tops of the feet at all extremties, and also on the underside of the head end of the casting to see whether there was any significant tilt, and essentially I have every surface dialled in to within 0.010" - so it is pretty well as straight as it can be.

Couple of pics of touching off on the lower end using both the spindle DTI and height gauge.




As a result of all these measurements I am very satisfied that I can now mill the feet flat, and drill the bolting holes and that this will keep the part visually straight when assembled, as well as maintaining machining stock on the head end. I have also established that to maintain the reference dimensions on the drawing, I will not be able to fully clean up the feet. That is OK - the area of non clean up will be quite small and won't be visible when assembled - but the key is that I understand what the casting is, and so I won't compromise the finished part by accidentally machining the feet back too far.

So - that's it for now. I have to finish clamping the part up and then I can start cutting it, but for now I am wrapping up, and heading to the airport. Have a good weekend all! Looking forward to putting all this prep work into practice.