PM Research #4 - Quarter Horse Vertical Steam Engine

[Grateful Ted]

Looking through the photos of this build, in page #60, shows you holding the inner head.
That gives some perspective to this engine. It really is big, at least compared to the ones I’ve been building.
I’ve always wanted to build the horizontal version of this engine, the PMR 4.
Hope I have time, I’ve got a couple engines ahead of it, & I’m 74, if you catch my drift.
Thanks for taking us along for the ride.

[propforward]

Thanks Ted. Don't worry - you're a spring chicken yet. I know this because of your avatar. You'll get to your big horizontal engine!

It is a big lump of an engine. Not the most elegant of engines, but impressive anyway. I'm actually very happy with how things are going. Lessons learned in earlier builds are helping a lot, and the build is more enjoyable for it.

Some of my pictures are not showing at the moment in earlier posts - I am in the process of moving pictures to a different hosting service. I'll do some of the earlier ones now, and by the end of the weekend they should all be done.

[MJM460]

Hi Stewart, I’m looking forward to your boiler build.  I do hope that you will include a little outline of the design work up front, and particularly the FEA.  I’m certainly envious of you having access to FEA. Unfortunately it came along a bit late for me, all my pressure vessels were designed using a slide rule. none of us had access to computers in those days!  And they are still standing and operating.

MJM460

[propforward]

The FEA is useful mainly for the more off the wall designs that come along these days. It is still better in general to do the calculations "by hand", but the FEA provides a useful extra insight for complex geometry areas of some vessels we build. Where I work we never use FEA as the sole design source, but use it more as supplementary evidence and support. It is certainly a useful tool. I don't really need it for the boiler, because that is very conventional design and construction which the BPV codes cover easily - but I'm still new to FEA and it will be a really useful exercise to model it. Besides I'm doing the design in CAD anyway.

The design will likely be complete a long time before the boiler gets started, but I'll gladly share the process. I don't know if I will publish drawings because of liability concerns. Maybe I can put enough disclaimers on to alleviate that, but there will be screenshots and so on, and for experienced engineers with interest in the calculations I can share those privately if there's interest.

[MJM460]

Hi Stewart, I could not agree more.  These forums are not the place for tutorials on pressure vessel design.

Some screen shots of FE output would be interesting though.  These techniques allow us to see how well (or not) the traditional safety factors allow for the stress concentrations introduced by some of the standard vessel details.

What ever you decide, I will be following with interest.

MJM460

[mikehinz]

Stuart, if you do end up building a boiler, I'll also be watching closely.  I have had fantasies of building one myself, but am quite cautious when it comes to a potentially 'explosive' situation!  Plus i'd need to make sure my welding/brazing/soldering skills are fully up to the task.  They used to be, but it's been quite some time since I've done any serious work in that area and there's a lot I'm sure I'm quite rusty on.

In any case, impressive work!  I'm looking forward to your further posts!

Mike

[propforward]

Thank you Gents! I will be glad to share the boiler project - I'm looking forward to it myself.

In the meantime, a little more work on the engine.

First off, I picked up where I left off on the piston. A relatively simple piece - an accurate OD, with counterbores each side and grooves for teflon piston rings. Critical geometry is to get an accurate through hole to locate on the piston rod, which needs to run concentric to the OD. Also important is that the inner face of the counterbores are perpendicular to the OD. Especially the one which seats against the shoulder on the piston rod.

In the event it mostly went smoothly, but I did have trouble with the grooves at first. I ran into some bad chatter which actually dislodged the piston slightly. Very vexing. I got the piston trued up again, but caused a bit of stress.

Some pictures of the process:



Sometimes it is a good idea to map out where you are going with the cutting tool, so that you can take into account tool width ahead of time and not get flustered. I sketch it all on my board which is above the lathe before I start.



Getting groovy.



After doing as much as I could in this set up I parted off the piston with about .020" of stock left on the backside. Important - I started the part off with my thin groove tool to make a face to clock against, before doing a more coarse part off.

I also made up some copper jaw covers to prevent marring the part.



Roughly centered the part using a close fitting gauge pin



Then carefully dialed it in by clocking the face then the OD.

Just a matter of clean up and making the second side counterbore.




I put a little groove on the face of this counterbore, to reference during assembly so I know which counterbore was made in the first setup vs the second set up.

After all was said and done, the piston came out very nicely. It is a perfect sliding fit in the cylinder bore, with about a .001 clearance. The groove diameters are within .0005" of nominal, widths within .002". Everything else is within .002" so a successful part.

So then I went on to the spool valve. I redesigned this per Larry's suggestion, increasing the length slightly and adding a threaded hole to connect to the valve rod, for easier adjustment.

Started with 1" material (didn't have any 3/4" after all). I think this is 303 stainless. I took it down close to final size .05" at a time, leaving about a .018" final cut, which got the OD to .001" under the valve bore as required.

 



I learned a lot about grooving (and parting) during this process. Also, I pushed the unsupported length of the part far too much really. As a result I got some vibration and the finish of the smaller diameter wasn't great. But you live and learn, overall everything went well.

I didn't take many pictures during the process, but it was a case of plunging the grooving tool to remove the bulk of the material along the valve length, followed by a light skim to final diameter with the grooving tool, followed by drilling the blind hole, then turning the part around, aligning again with a test indicator and drilling and tapping the valve rod hole on the far side.




The parts as they stand:





I still need to drill a cross hole on the spool valve, but I'm out of time for today. Time to clean up and deal with some everyday matters. Such is life.

Thanks for watching. This was a very fun workshop session.

[Baltic]

Looking Good Stuart,

Good to see you knocking of the "rats and mice" pieces, + 1 for the Boiler Build, I have a decent lump of copper pipe, 6in diameter, I  also, want to make a boiler some day.

[Michael S.]

Hello Stuart,

I see you've made good progress. Now there is not much missing of parts for the first run of the machine. I find it very interesting and informative to watch you at work. When I see your way and the building of the machine on youtube by the girl who also builds this steam engine, it's nice to see how many ways there are.
I look forward to more pictures.

Greetings Michael

[propforward]

Baltic - thank you. Yes, important to get these hidden pieces done. For two components that are actually pretty straightforward I derived a MASSIVE amount of enjoyment from them. I put that down to applying some thinking learned in my last engine build, where parts were not as well made geometrically. So I may have talked these two parts up a bit given their relative simplicity.

Michael - thank you also - one of the many pleasures of this hobby is looking at the many alternative ways of making the same parts. I haven't checked on Blondihacks channel for some time. I think she has been a bit space constrained on her particular machine tools, but I did see her figuring out how to get the frame casting machined on her lathe. Like many home machinists she comes up with ingenious solutions to use the tools she has available. I'm lucky in that I acquired slightly larger machines with a little more working space, but it's always good to see another approach.

[Michael S.]

Stuart, well, if I didn't have a few sets of steam engine castings lying around, I'd love to build this machine too.
At first I thought the PM Research #4 was a typical American steam engine with its high stand and long connecting rods, but I also found illustrations of German upright single-cylinder engines in a book. Built in the neighboring town of Halle around 1902. It looks somewhat similar to the #4.
I'll take a look at PM's catalogue.

Greetings Michael

[propforward]

Hey Michael thanks for posting that picture. The resemblance is uncanny - I have to believe that the original engine the PMR #4 is modelled on drew inspiration from that engine - there are a lot of similarities.

[Grateful Ted]

I think these engines were state of the art for factory’s & mills around the turn of the last century.
I wonder how big the flywheel is on the German engine.
I have a PMR #5 I started couple years ago, think I’ll dig it out & start on it again.
BTW, the hen in my avatar, like me, is no spring chicken either.
Her name is Daffodil, she’s going on 11.

[propforward]

I have a PMR #5 I started couple years ago, think I’ll dig it out & start on it again.

That's a great engine. I have one of those sets. I think it would be great if you would continue with that and post about it, we'd all enjoy seeing it.

[Grateful Ted]

Prop, this is my progress so far.
I made a major blunder when drilling for the crankshaft, notice the scratch built crank bearing caps.
After a couple more mistakes, (all fixable) I decided to try out a few design changes, & use 4-40 socket screws.
This is gonna be a bitsa i guess, i just hope it runs well.
I hope the photo shows up.
Now back to four build ;-)
Cheers, GT