Author Topic: PM Research Engine Number 1  (Read 6555 times)

Offline propforward

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Re: PMR #1 - Props first casting project
« Reply #30 on: September 30, 2018, 11:10:44 PM »
Well, I spent the week mulling this over, poring over the plans, and decided that I didn't have my machining sequence optimized. What I failed to do, was interpret the relationship between the position of the steam chest floor and lip in relation to the cast boss on the inboard end of the steam chest. If I want the gland centered in that boss (and I really do), then it is best to machine the steam chest to that feature. That means boring the cylinder, then drilling at least a center hole position in the boss, and referencing from that.



Well before tearing down, I measured the height of the boss, then measured the lip and floor of the steam chest, and found that if I want to center the gland in the boss, I still have 0.024" of steam chest to machine away. That gives me enough material to go back to the lathe, machine the bore and outboard face, and then come back and true everything up and keep going, so no harm done.

I decided that since it was all set up, and that I am pretty sure I can get the faces of the cylinder true to the lathe chuck, I might as well drill the bolt holes. So I did, using the cover as a template.



So on to boring.

Except - that's a pretty new operation to me, and I haven't had a lot of success with it. Time to change that.

I spent a good bit of time on saturday reading up on making boring bars and bits. I discovered in the old, mostly crappy lathe tool kit that came with the lathe, that I had a 3/8" boring bar, with a 1/8" square HSS tool blank in it. Perfect!

I made several cutting tools, and had several attempts at boring out a piece of aluminum rod that I had left over from a project. It already had a 20 mm hole in it, so this gave me a good practice piece.

After several dismal attempts I shut up shop and spent a few hours doing more research. Armed with some internet pictures and some advice from books etc, I returned to the shop this morning, and had another attempt at grinding a tool. This is really tricky on a small tool blank, and doing it freehand, on my bench grinder which has very curved edges on the wheels, but I made this thing.



It doesn't look very impressive, but the clearances and rakes are more or less kind of sort of where they need to be.

A few test cuts in aluminum showed that if I make 2 cuts for each diameter position, I can get a good finish. My reading suggested this was necessary, to account for boring bar flex. The first cut tends to be a bit rough, but the second one cleans up well.

I still didn't want to rush on to my cast iron cylinder just yet, so I gave it a go in a piece of stainless pipe I had laying around.



The finish actually felt very good to me, so since I had everything set up I took a deep breath and decided to have a try at cleaning the bore.

Here is my set up





As you can see, I cut off the excess piece of tool blank from the far side, and I have to have a goodly amount of overhang of the tool bar. The bore has plenty of material to take out, so I felt OK making a start with a light cut to see how things went. If it went poorly I could abort and still save the part. I set up the cylinder in the chuck by using parallels behind it on the machined face, and pushing it against them using a dead center in the tail stock. This had the part running very true in terms of the machined cylinder faces relative to the chuck.

After a couple of passes, I judged that everything was proceeding satisfactorily enough, that it was time to make a bid for the 1.000" bore.

To help, I noted the crossfeed dial position each time, and measured the bore using a bore gauge and micrometer, noting the nominal cut taken and any error. I wanted to get a feel for variation in diameter so that I could account for that as I got close to size.



It worked out well. Certainly I sneaked up on the bore size, but I got it, and I think the finish is acceptable. (Hard to tell from the blurry picture).



The icing on the cake was testing the bore with this aluminum plug. The plug measures 0.999" on my micrometer, and it slid evenly through the whole cylinder, with no detectable play, and no binding as I pushed it through. So I'll call the bore good. I may hone it at some point, but I'll be honest, I feel like my machine set up efforts, and taking the time to test new techniques are really paying off.



Since it was all set up so nicely, I decided to face the cylinder to length on the outboard end. I did this by measuring from a scribed center on one of the side port bosses. The inboard end will be machined to length from this new turned face.



Finished outboard end. The machined away boss that end is not used on this engine.



Colour me happy.

While in the shed, I have also made a start on cleaning up the base. Just by using emery paper on my surface plate. I need to take a little bit more off, just enough to make the underside flat with some clean metal all around.



While digging around I found a nice piece of 3/8" thick aluminum, left over from some work project or another. I'll flatten the top of it, and use it as a jig plate to hold the base casting.



I also found this lovely piece of cold rolled steel, a chunk of which is going to be used to make some new boring bar holders, based on the documents kindly sent to me by Baner.



So, some success. I feel good about all this. Next step is to machine the inboard face and gland to length, then I'll get back to the steam chest and finish that.

One thing that is very apparent, is that I really need to make the grinding table for my bench grinder. I have Howard Halls book - Tool and Cutter Sharpening (Workshop practice series 38) which has a nice design in it. That will really help for getting cutting bits made properly, once and for all.
« Last Edit: September 30, 2018, 11:19:52 PM by propforward »
Stuart

Offline Gas_mantle

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Re: PMR #1 - Props first casting project
« Reply #31 on: September 30, 2018, 11:24:40 PM »
Looks great to me Stuart.

I'm following along with interest and looking forward to seeing it running  :)

Offline crueby

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Re: PMR #1 - Props first casting project
« Reply #32 on: September 30, 2018, 11:29:12 PM »
Excellent result!


 :popcorn:

Offline mikehinz

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Re: PMR #1 - Props first casting project
« Reply #33 on: September 30, 2018, 11:37:13 PM »
I'm going to closely follow this thread as this is an engine I'd like to do in the near future as my first engine from castings.

Good work so far!

Mike
MIke
Wichita, KS, USA

Online b.lindsey

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Re: PMR #1 - Props first casting project
« Reply #34 on: October 01, 2018, 12:51:37 AM »
Glad to hear it turned out well. It looks great in the pictures too.

Bill

Offline Kim

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Re: PMR #1 - Props first casting project
« Reply #35 on: October 01, 2018, 05:23:38 AM »
I'd say your boring of the cylinder turned out very nicely!

I made Harold Hall's grinding rest a while back.  Here's my build thread if you're interested: http://www.modelenginemaker.com/index.php/topic,4045.0.html

I do like it.  It was a nice project and I use it all the time when sharpening tools (as one would suspect :)).  My only complaint is that it's a bit of a pain to setup, but it works nicely never the less.

One thing I would suggest is to make the Drill sharpening jig for 135o as opposed to 118o.  Most of the drills I want to sharpen are 135o.  I messed up a few initially as I was sharpening them all with the same jig, then I realized what I was doing :(.

I still haven't gone back to make a 135o jig yet, but I plan to!

It's a great project to do, and very useful too. I would definitely recommend it!
Kim

Offline propforward

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Re: PMR #1 - Props first casting project
« Reply #36 on: October 01, 2018, 02:43:58 PM »
Thanks all, I do appreciate you following along, and your positive comments.

Kim - that build log on the grinding table is excellent! Thanks for that, I shall read the whole thread as background material.
Stuart

Offline gary.a.ayres

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Re: PMR #1 - Props first casting project
« Reply #37 on: October 02, 2018, 10:36:39 PM »
Progressing nicely Stuart.

Your patient approach is paying off.

gary

Offline propforward

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Re: PM Research Engine Number 1
« Reply #38 on: December 27, 2019, 10:51:06 PM »
It's been too long since I worked on this engine. I stopped because I became unsure of my sequences and thought I might be painting myself into a corner. Plus I wanted to work on the piston, which is a steel item and I was having difficulty with that.

Anyway, I am leaving the piston aside for now, although good progress has been made with steel finishes.

Today I reviewed the cylinder, and elected to continue. I had not yet machined the cylinder to length, so that was today's job.

First thing I did was just to check parallelism of the faces and the bore, to reassure myself they had been made correctly - which they had. I was happy about that.

Then I mounted the cylinder in the 3 jaw, with my Edge Technology chuck spider to hold it square, and machined the opposite face.



The gland boss in this picture has to remain proud of the cylinder face by 1/8", so I'm turning from the inside out. I had originally thought about milling this face, but this seemed a better technique in the end. It worked out fine - I got the length within 0.001" of print according to my micrometer, so I'll take that.



I decided to start work on the various bosses and slots. The gland boss still had about .013" to come off to get to the right length, and although I could have done that while turning the face, I finished it in the mill.



For Christmas, I got one of these handy dandy gadgets. I must say, it makes centering a bore or a rod on the mill an absolute breeze.



I then proceeded to center drill and drill the features on the gland boss.



Unfortunately the gland boss ended up slightly off center relative to the holes and the face of the steam chest. When I machined the steam chest I did not quite judge the height of the face right. I don't think this will matter in the end, just doesn't look quite perfect. The drawings were a little unclear in that regard. Part of the learning experience. They should really give a dimension from the center of the bore to the face of the steam chest.

I also cleaned up the faces of the port bosses, but decided bot to drill the holes just yet.



What I want to do next is mill the 3 slots in the base of the steam chest, so I started getting that set up.



This is as far as I got today. I need to level the steam chest, then I can find the center of the chest from the cylinder faces. I think I will actually clamp the cylinder in a V block or something though, so that I can find the center of the bore as well. I should have machined the slots when I had the cylinder set up for the steam chest perhaps, but I should be able to get where I need to.

Anyway, good to be working on the engine again, hopefully more progress tomorrow.

« Last Edit: December 28, 2019, 12:03:22 AM by propforward »
Stuart

Offline propforward

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Re: PMR #1 - Props first casting project
« Reply #39 on: December 28, 2019, 12:59:51 AM »
Looking great Stuart. I centered my ports to the bore by doing it and then turning it ninety degrees from the way you are holding yours, inserted a plug and centered from that.

Whiskey

Perfect - glad I read back through the thread. This will work, and Ive already got a very close fitting rod to use. Cheers!
Stuart

Offline gary.a.ayres

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Re: PM Research Engine Number 1
« Reply #40 on: December 28, 2019, 10:13:46 AM »
For Christmas, I got one of these handy dandy gadgets. I must say, it makes centering a bore or a rod on the mill an absolute breeze.



You too, eh?

I fancied one of these too but decided not to push it too far. Next year...

Nice progress on the engine.

gary

 :ThumbsUp:

Offline propforward

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Re: PM Research Engine Number 1
« Reply #41 on: December 28, 2019, 12:31:25 PM »

You too, eh?

Oh yes! Appropriate unsubtle hints were left.  ;D

Stuart

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Re: PM Research Engine Number 1
« Reply #42 on: December 28, 2019, 01:12:38 PM »
You will very much enjoy the coax indicator Stuart. Santa did well  :)

Bill

Offline propforward

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Re: PM Research Engine Number 1
« Reply #43 on: December 29, 2019, 01:00:35 AM »
Santa is a good egg, and listens well.  ;D

Anyway, pressing on today. I set up with a very close fitting rod to let me locate the center of the bore.



Using the two clamps allowed me to adjust the level of the top machined surface of the steam chest (and therefore the base of the steam chest).

I aligned the V blocks supporting the rod to the Kurt vise using other V blocks - which worked really well. I did double check that the faces of the cylinder were parallel to the X axis of the table.



Clearance was a problem with this set up. It worked out fine for the larger slot, although I had to extend the milling cutter a way.



Got the slot done. I also noticed that I could clean up the one side of the chest a bit more, and put radii in the two corners. I may well do that at some point. Should have done a better job up front.



Of course - having finished it, I realised that the supplied drawings specify the slot with from the outside quadrants of the radius at the ends of the slot - whereas at work we always dimension slots from the center of the end circles - which is because that is most useful to the mill operator. So unfortunately this slot is too wide. However, I think it will still work. I'll make sure the valve suits the slot. And in future, I'll be more careful to check all dimensions on supplied prints as to how they are defined.

I'm also disappointed about the ridges in the slot, which are a result of milling the slot in stages. I wonder what I could have done to avoid these ridges? I locked down the cross slides when milling this, but maybe there is a backlash adjustment I need to make? Need to give that some thought.

So on to the smaller slots. And here I got in to some difficulty. I simply could not get close enough with my quick change collet holder, so had to resort to using the standard Jacobs chuck for milling the two small slots. I may have to obtain some standard R8 collets - or a better approach might be to make / modify some clamp bars to a lower profile for small work.

I did have to move clamps around throughout the process, but I managed to get the job done.







Finished:



Not the prettiest. Improvement needed of course. However, depth of the short slots was only 0.005" over nominal - so getting the hang of dealing with quill backlash, which is encouraging, and everything seems to be in the right place.

Close up of the ridges



I don't think these will affect the operation of the engine, but obviously I'd like to improve on that.

To finish up for the day, I put the side holes in.





I now face the challenge of making four porting drillings, at 20, to port the two small slots to the bore. I started looking at the use of an angle plate I have, but did not get very far. I think I want to use the tight fitting rod to find the bore center to locate the ports. Anyway - more thought needed, and hope to put some time in on this tomorrow after getting my chores done.



I've got this, but I'm not seeing a way of using it and keeping access to the bore, which I need in order to position the ports. I think.




Thanks for looking. As usual - mixed feelings. Some things went OK, other things didn't turn out as well as I hoped, but I think I'm still looking at a functional cylinder to get to a working engine at this point. However, I'm desperately trying to make really nice looking parts, not just functional ones. I'll get there.



« Last Edit: December 29, 2019, 01:18:19 AM by propforward »
Stuart

Online Johnmcc69

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Re: PM Research Engine Number 1
« Reply #44 on: December 29, 2019, 10:22:03 AM »
The parts are looking pretty nice Stuart!

 An enjoyable build to follow, keep up the good work!

 John