PM Research #4 - Quarter Horse Vertical Steam Engine

[propforward]

So I used my aluminum alignment post again, this time turning the larger OD end to a very close fit for the cylinder bore, then drilled a clearance hole and parted it off to make a simple location post.



The idea is to stand the cylinder up on parallels, locate the ID of the cylinder, then touch off on either side of the casting at the X location of the valve bore, then balance the side to side measurement to get the cast valve location straight in the X direction relative to the cylinder bore, so that the whole arrangement doesn't look too out of whack when assembled.



I love this tool for finding centers. It's just a lot of fun for some reason.



Anyway, the plan worked a treat. Squaring up the part with the bore located on the plug was easy, and I rechecked center of the cylinder bore after squaring the part up. All was well.

Then I just lightly touched the surface of the casting with a 5/8" end mill. The final valve bore is to be 5/8". This was just a final visual indication that the machined bore will completely clean up the cast bore, and look central. I think it is positioned nicely.





So then, on to machining.

How to make a 5/8" close tolerance hole? I have seen some people stuff an undersize drill down the cast hole and then ream it, but that doesn't seem like it will guarantee a straight hole. No, I think the right approach is to bore the hole out. I do have a 5/8" reamer already, so I may well elect to bore close to size then ream to final, or I may choose to bore the thing to final dim. I don't have a powered down feed which is not necessarily an issue, just means the rate of feed is not constant.

So, went to set up then remembered that while I have a perfectly serviceable boring head, I do not actually have a boring bar to fit it.     

So I have to procure one or make one. I may well make one to take one of my inserts. Don't know yet.

In any case I decided to make something else today while I ruminate on that.

So, on to the inboard head. This is supplied as a cast iron part. There is not a whole lot of machining stock on it, so I needed to be a little careful with it. I decided to hold it by the boss initially to make cleaning the OD simple.



Then turned it around to make the boss features and locating step for that side. The boss just about cleans up.


I bored out the ID to tapping dimension, mainly because the drawing shows a flat bottomed hole for the threaded part. I am sure that doesn't matter at all, but I was in the mood to do it this way, and it went very smoothly.


Then I turned it around to set up for the other locating step.

I actually set it up in the 4 jaw at this point. The reason was that when I set it up in the 3 jaw, I could not get the face running true AND the bore on center. It was 5 thou off, which would mean that the cylinder would not be concentric to the bore in the frame, by an unacceptable amount. I think it's the geometric relationships that are easy to get caught out on, and I strongly suspect that is what caused binding on my previous engines.

Anyway, getting that sorted in the 4 jaw was simple, by checking the face of the part for run out, and also the bore (by use of a tight fitting gauge pin).



A simple enough job to turn the step, resulting in a very pleasing fit to the cylinder.

Then to the mill for drilling - this time knowing up front that the bolt holes are not equally spaced.







I made a part correctly and first time! No rework!   

Very satisfying.

So that's today's shednanigans.

[propforward]

Incidentally, the irony of not boring the cylinder on the mill, only to choose that approach for the valve is not lost on me. A few set ups could have been saved.


Hey, if I was good at this I’d be making a living from it.

[RReid]

You're doing some real nice work, Stuart, whether you like to admit it or not!

I actually set it up in the 4 jaw at this point. The reason was that when I set it up in the 3 jaw, I could not get the face running true AND the bore on center.

I don't even own a 3-jaw, although I do recognize their convenience. I much prefer the 4-jaw, or collets where appropriate.

[propforward]

Thanks Ron I appreciate your kind words. I must admit that today, after installing the 4 jaw I did admit to myself that I would be better off just leaving it in place and using it as standard. With a bit of practice and two chuck keys, it does not take long to get a part centered.

[gary.a.ayres]

Nice work Stuart.

There's something so exciting about the machining of a cylinder!

[larry_g]

So then, on to machining.

How to make a 5/8" close tolerance hole? I have seen some people stuff an undersize drill down the cast hole and then ream it, but that doesn't seem like it will guarantee a straight hole. No, I think the right approach is to bore the hole out. I do have a 5/8" reamer already, so I may well elect to bore close to size then ream to final, or I may choose to bore the thing to final dim. I don't have a powered down feed which is not necessarily an issue, just means the rate of feed is not constant.

So, went to set up then remembered that while I have a perfectly serviceable boring head, I do not actually have a boring bar to fit it.     

So I have to procure one or make one. I may well make one to take one of my inserts. Don't know yet.

In any case I decided to make something else today while I ruminate on that.



So that's today's shednanigans.

I chose to ream the 5/8" bore for the valve.  It was a couple thou over when finished.  My problem was that the material for the valve was a thou or two under 5/8".  I did make the valve from the supplied material and in the end it worked but gave a constant leak out the exhaust.  I made a new valve from some 304 stainless and 'fit' it to the bore with a tight slip fit.  The leak went away and all is good.

lg
no neat sig line

[propforward]

Funny that Larry - I was making a revised sketch of the valve today, incorporating your threaded attachment method for easier adjustment - and as I looked at the PMR drawing I had to laugh. If I issued a drawing for a part with an OD of .624” +0 / -.001, and issued 5/8 round bar to make it, the machinist would happily come snd kick my posterior seating cushion. I’ll be starting with 3/4” to give myself a chance.

[crueby]

Funny that Larry - I was making a revised sketch of the valve today, incorporating your threaded attachment method for easier adjustment - and as I looked at the PMR drawing I had to laugh. If I issued a drawing for a part with an OD of .624” +0 / -.001, and issued 5/8 round bar to make it, the machinist would happily come snd kick my posterior seating cushion. I’ll be starting with 3/4” to give myself a chance.

Yeah, the 5/8" roundbar usually has a much larger out-of-roundness than that!      

[propforward]

Update....................

Boring bars were obtained. They were not expensive, and make use of inserts I already have. I've had trouble grinding HSS to the right profile for boring. Getting better at normal turning tools, but decided I wanted to press on.

Earlier in the week I tested the offset boring head by making a 5/8" hole through a block of aluminum. That went well, so onto the real thing.





Anyway - all worked out rather well. In fact, so well that this will definitely be the technique I try for the cylinders on my next engine (A Twin Victoria I purchased from Ron Ginger). There is no measurable taper in the valve bore, and it's right on dimension. I'm very happy with it.

After that, a simple enough job to locate each bore and then drill and tap the bolt patterns.



Then on to adding the steam inlet - a 1/8 NPT into the side boss. I packed up the casting, then touched off on a few places on the face of the boss to see how flat it was - had it within about .01" which is plenty good for a cast feature I think.



Then just cleaned it up with an end mill, visually centered the mill over the boss by using a gauge pin, and drilled and tapped the hole.



There are two more bosses on the casting for drain cocks if needed. I do hope to run this on steam some day, but I don't know what drain cocks I will use, so those bosses will stay unmachined for now, to be figured out at a later date if needed.

In the mean time, on to the outer cylinder head. This is a relatively thin casting, with a raised decorative feature on the outside. A difficult piece to hold. I decided to have a try at pressure turning, which I had seen Joe Pie demonstrate on Youtube.

<a href="https://www.youtube.com/watch?v=0DrI5B4hui0" target="_blank">http://www.youtube.com/watch?v=0DrI5B4hui0</a>

Joe is turning a large diameter thin piece in that video, but the technique is very applicable here.

For this I need two bushes - one to hold in the chuck, the other to push against the part with a live center in the tailstock.

So I bored a taper in a piece of spare aluminum:



My picture doesn't show it, but I turned an aluminum bush to a close fit on the decorative feature on the outside of the casting to hold it concentric. Then I pushed the tailstock up against the part with the other bush, and turned the OD. This worked a treat.



I also cleaned up part of the face, just enough to be able to clock it once I transfer it to the 4 jaw, which I can do now that the OD is clean.



It's now very easy to clock OD and face and get the part running true, to machine the face and step complete.



I've actually given up on my 3 jaw chuck now. It is a very inaccurate chuck, and I can get things set up much easier in the 4 jaw now.

Couple of pics of turning the locating step:





Test fit:



After that, simply a matter of spot facing the outside, and drilling the clearance hole pattern. No pics of the process - pretty rudimentary.

Finished part:



And then here are a few pics of some test fitting of parts so far:







I'm pleased with how this is coming together. Things are fitting very nicely - I have high hopes for this engine. Now to get to some of the nitty gritty - up next, piston and valve, and finishing the bearing blocks. Now that I have tested boring holes on the mill, that will be an ideal method for boring the crankshaft bearings out. More to come!

[crueby]

That big beastie is looking great!   

[MJM460]

Hi Stewart, your patient approach is paying off and it is all coming together very nicely.

As Chris says, it’s a big beast.  But really looking good.

MJM460

[propforward]

Thank you guys.

I have to say, I am enjoying this hobby more and more. Now that I have got to understand my machines better and get them set up better, not to mention the processes themselves, the effect is cascading and I'm just having a blast with it. I can't wait to get back in the shoppe and work on the next parts.

[propforward]

A teensy bit of progress today.

What I have here is part of the long term plan. That there is a piece of 20" long, 8" sch 40 316L stainless pipe. And I think that will make a very nice boiler. Bit of a way off but it was available and the price was right. Like.............free type price is right.


On actual engine stuff, I snooped around and found a piece of old steel to make the piston out of. It seems that PM Research forgot to include a chunk of steel for that. I'd call them about it but I bought the kit in 2015, so a bit late to be getting into that. It is also possible I nabbed it for something in the dim and distant past.

Anyway, don't know exactly what steel it is, but very likely 1018 from the way it machines. It's going OK. I'm at 1.55" on the OD now, so next shop session I'll get it to size and put the rest of the features in. Not an especially difficult part, but very enjoyable.


That's it for now. Not much progress - but some progress, and a pleasant few mins in the shoppe.

[mikehinz]

Stuart, very nice work!  You've got more nerve than me regarding a possible boiler build.  Those things scare me, even though in theory, I could make one. 

One gentle suggestion.  If it were me, and if you're going to one day run this engine on live steam, I'd think about getting a bit of cast iron bar to make the piston from.  A cast iron piston in a cast iron bore is well proven to run quite well for a long time.  I'm sure the 1018 will also work, but it might not last or long or may suffer from a bit of stick/slip unless you open up the piston bore clearance a bit.

Anyway, please feel entirely free to ignore my suggestion!  I'm sure whatever you do will be great.

Mike

[propforward]

That's good info Mike. I'll file that away - I'll go with this for now, but plan on making a cast iron piston for the long term. It will very much depend on the success of this engine when it runs on air.

As for the boiler, there is a long road ahead of me on that. Fortunately I have been designing pressure vessels for work using the ASME BPV code, and I have access to the code calculation software so I'll make use of that. Followed up with a full finite element analysis, which is something else I have been getting into the last couple of years. Finally, and perhaps most importantly, I have access to ASME section IX welders and CWI's, who will help me set up and inspect the welds. I intend to way overbuild the boiler, and will certainly strenuously hydro test it. I'm not taking any chances on it! Should be quite a project though.

Thanks for looking in Mike, I really appreciate and value your input.