The Bolton No 5 Vertical Open Column Steam Engine

[Bear]

Very nicely done!

[MJM460]

Thank you Derek, it’s good to have you looking in.  At my pace though, I don’t think I had better count on taking it up as a second career, model size or otherwise.  At least lockdown gives me an opportunity to make a little progress most days.

Thanks again Bear, comments are always welcome.

Today I made that second eccentric.  I am keeping the original from the casting as it will be interesting to see how the engine operation compares with how it performs with the extra valve throw.  It should tell me whether the effort of making the second was worthwhile.

I started in the three jaw.  I thought that would save one operation but of course I had to centre again in the four jaw anyway before I could shift it over by the eccentric throw.  Live and learn.  Fortunately it is not a big deal to change over the chucks.

I used a parting tool as a profile tool for the groove for the eccentric strap.  I also started the hub for the set screw at the same diameter, and a groove for eventual parting.

In the four jaw, I centered the embryo eccentric, using the dial gage, and a spirit level on the side of the jaws to ensure that the jaws were level for each adjustment.  Now I look at the photo, I am wondering why I did not run the gauge on the machined surface.  But the picture shows the result of moving the eccentric across the required 2.5 mm.  Fortunately, the three jaw is very close to true, so apart from a bit of roughness on the surface of that bar, it is probably close enough.  Then I bored and reamed for the shaft by what is becoming the standard method.  It is giving good consistent results. 

Leaving the hub for the set screw the full eccentric diameter means a very deep hole for the set screw.  So I machined a little off the hub.  Because it started eccentric, it was an interrupted cut.  If I had continued until it was round, there would not have been enough depth for the set screw, so I left it a sort of elliptical shape.  It was interesting seeing the shape appear as the interrupted cut proceeded.

After parting off, I was able to hold the eccentric in a collet by the flange OD, so I could drill and tap for the set screw.

Quite happy with the finished result.

I am running out of excuses, I am going to have to tackle the con rod.  It’s a tricky little beast.  I need a good nights sleep before tackling that one.

Thanks to everyone looking in.

MJM460

The last photo should have been the first!

[gary.a.ayres]

Very neat work on the eccentric.

It's coming along...

[MJM460]

Thanks Gary, it was relatively easy to make the second eccentric, so worth while to try for better valve events.  Still to be proven whether I succeeded.  That will come later.
Now for the conrod.  Lots of fondling required for this one.  I came up with three ways of making it from barstock that would each be easier to handle than the casting.  At least if I muck it up, I have a plan B or two.

I laid the raw casting on a flat surface and packed it with feeler gauges to make the centre line of the rod as near horizontal as I could, and scribed a line as reference.  I used two rulers against the sides of the  big end to amplify the any departure from parallel, and work out how much to pack the little end so I could hold it in the vice while I machined the sides of the big end.

Then I could turn the casting to make the pin axes vertical, and hold it in the vice to machine the top and bottom.  Then by clamping it down on a wooden packer, I could drill and ream the two pin holes.  I think that as usual the pictures tell the story better than words.

I need to split the description here so I keep within the limit for photos.

I will be back soon,

MJM460

[MJM460]

Next I wanted to machine the flat faces of the little end to dimension.    I spent most of the afternoon making up a somewhat Heath Robinson jig.  You can see it evolved and even changed as it progressed.  The little clamp bolted on the end made an easily adjusted balance weight.  Tested on parallels it balanced quite nicely in the position shown in the photo.   

It worked very well, and the little end faces were soon machined to dimension.  The crosshead pin, made earlier, fits quite nicely.  It might have been easier to just use a simple mandrel and loctite as was suggested before I started.  It would have entailed a night for the loctite to set for each side of the little end, but I was concerned about pressing the pin out without doing any damage.  Probably would have taken as much time to make a little pin press of some sort as it did to make the jig I chose to do instead.

The jig is all set up with pins I can swap out, so I can now swap the pins and machine the big end to width.  However, first a little more study is required.  The drawing width is actually less than the diameter of the tapered rod of the part, so that would result in flattened sides of the rod.  But certainly possible.  Another alternative is to leave the big end a little wider.  That would entail a longer crank pin.  I have to remake that anyway.  It was the first component I made and I made it too short.  At least, making it gave me confidence that I could manage those shoulders and small diameters.  But more importantly, the longer crank pin will not clear in the slot in the baseplate.  I have to think about whether there is enough metal to enlarge the slot. 

Still a little way to go on this small component, but so far it’s looking good.  And at least a plan B is available if all else fails.

Thanks for looking in.

MJM460

[Bear]

Coming along very nicely. This thread makes for a great learning experience for me. I pick-up at least one new idea in each of your posts, MJM.

[MJM460]

Thanks Bear, glad to know that I am helping you along. 

After long study of the base plate and how things are fitting, I concluded that I can machine the big end down to 7.5. In the direction of the crank pin without unduly flattening the sides of the rod.  There seems to be plenty of scope to machine the slot in the baseplate wider to accomodate the necessary longer crank pin without compromising anything, so that is the plan.

With some careful marking the centre line and measuring with the calipers, I worked out how much to take from each side to maintain the same centre line as the little end.

I swapped out the pins in my holding jig so I could install the conrod with the big end on centre for turning.  It only required about 1.5 mm off each side. So even with very light cuts, it was soon done.  The advantage of my jig is that it takes only a few minutes to loosen the set screws, rotate the part to expose the other side, tighten the screws and back to machining.  It seems to have worked well, so perhaps making the jig was worthwhile after all.

The conrod still needs the slot machined for the crosshead, and I think I will round off the bottom of the big end.  It achieves very little, and is only extra mass contributing to lack of balance.  Small  I know, but wrong direction.  But I want to get the base and crank pin all fitting first.

Next step was to make the new crank pin.  Simple turning from 8 mm rod held in a collet.  I was very cautious approaching the required diameter, and achieved a good fit.  Very handy to have the conrod available as a gauge.

Next step was to prepare the end for the M4 thread.  Main issue was to leave the pin length to the shoulder the right length, but sure enough, I managed to leave it a bit short by going over length for the M4 threaded part.  That meant trimming again the under side of the head to restore the required length, but as it was all still in the collet, no big deal.  The other critical bit is the groove against the shoulder end of the thread, that last couple of threads that a die does not cut.

I calculate the diameter at the root of the groove as 3.1 mm for 100% thread depth.  (I have previously found the hard way that turning the groove to the tapping drill diameter does not allow components to screw up to the shoulder).  This allowed the nut to seat firmly against the shoulder.  I tested both a standard nut and my test plate.  Finally, I screwed the test plate on with the con rod big end in place, and checked that it could turn freely without being gripped between the plate and the shoulder.  Should definitely work when screwed into the crank disk.

Forgot to take photos of that, so apologies for including the one for the first pin so you can see what I am talking about.  The pin is still part of the original bar, in the collet, ready to be transferred to a hex collet block for machining the flats on the head of the pin tomorrow.

Then I can set up the base again and machine the slot (for the crank) to width.

Thanks for looking in,

MJM460

[MJM460]

I’ve been AWOL for a couple of days, I hope my excuse is acceptable.  On Sunday morning, my wife was in the garden, got her foot tangled under a brick and the drip watering piping, and measured her length on the concrete.  To her credit, she was able to get up by herself without increasing the damage and come inside for help.  Put her teeth through her lip, which is now spectacularly black with the bruise, but relatively superficial.  (She decided that black is not her colour for lipstick.)  But more significantly, she broke her wrist.  The one that had a plate inserted after breaking it while overseas a few years back.  We spent the rest of the day in emergency, getting X-rays and scans and having it reset.  So much for a little shop time.  Yesterday was pretty full with getting used to learning to do things one handed with plenty of help from yours truly.  All very exhausting.  And a few more specialist appointments to go to check that it is appropriately set.  And probably six weeks or so to heal, then all the physio.

However today, we had a couple of hours between lunch and another appointment, so I got back to that crank pin. 

I transferred the collet to the hex block and put it in the mill vice.  It was still on the full rod length, so I rigged a support at the end of the mill table so the overhang would not make it to hard to press the block down in the vice.

The rod diameter meant I had to take 0.47 mm of each side to fit a 7 mm spanner.  While the collet was still in the lathe I carefully started the parting off and left a groove 7 mm diameter as a guide.  (It turned out 7.05 so I just needed to touch the bottom of the groove.  Worked well.)  The hex block makes it very easy to index 180 degrees to do the opposite side, and it was nice to see the spanner fit snuggly.  Then rotate the block 60 degrees for the next two flats.  With the spanner fitting that pair, the third pair was quickly completed. 

To me, the hardest part of the process is consistently setting the zero each time I shifted the block.  At each move I completely lifted the block and brushed away any chips, then pressed the block down firmly while I tightened the vice.  I have found marking the part with a blue marker, using the cigarette paper to touch the tool to the part (after which the tool still seems high), and then going down about 0.02-0.03 at a time until I remove the ink.  Then I reset the zero on the quill DRO and make light cuts to the required dimension, checking with the spanner as the second side approaches the dimension.  Glad I have that DRO at least.

The collet was then returned to the lathe for parting off.  The rod easily passes through the headstock, and I use a similar support on the cabinet at the headstock end to support the overhang and stop it whipping around.

I was delighted to find that the conrod rotated nicely around the pin when it was tightened into the crank disk in place of the one I made way back, but was too short.

Surprisingly, it was within a few file strokes of actually entering the slot in the base plate, but I feel that a little clearance is really necessary.  I can widen the slot by 2.5 mm, and still have a bar 7 mm wide at the end of the base.  This will give a little more practical tolerance on the column locations to line up the cylinder group.

To finish the conrod, I still need to machine the slot for the crosshead tongue in the little end, and I think that big end really needs to be rounded off to reduce its mass.  That will be less to balance, and as the big end is not split and so does not have the bolts to hold it together, I think the smaller form will look better.

So when I get the next shop time, I will work on that slot in the base plate and finish the conrod.  Might not be tomorrow though.

Thanks for looking in,

MJM460

[Jo]

Please send your wife our best wishes for a speedy recovery 

The engine is coming together nicely, especially as it is your first adventure into castings

Jo

P.S. I find it fun to do the flywheel so that I can do a bit of round and round testing as soon as the crankshaft is in place 

[Bear]

Yes, best wishes to your wife.

[Kim]

Yikes! Sounds like you two had quite the time!  Hope she heals quickly, that doesn't sound like ANY fun!

And I'm enjoying following along on your build progress too!
Kim

[MJM460]

Thanks Jo, good wishes duly passed on and always appreciated.  On the model, thank you for the nice comment.  I have learned a lot about what to look for from your many comments about casting fondling.

Thanks Bear, for your Kind wishes.

Thanks Kim.  It certainly wasn’t a fun day. And it wasn’t even my wrist.  I am enjoying the build, but today is not one for concentration on precision work.

We got in to start the wrist specialist today.  He looked at the scans and said, “Wow, you’ve blown it apart AGAIN!

Last time she was on a ski slope, but that is another story.

He scheduled surgery for this evening.  It is better to get it put together and a plate put in sooner rather than later.  I wonder if the last one was kept in her file for possible reuse, they are expensive little things.  Spent the afternoon having lunch before she had to fast, getting a COVID test, came out clear, and packing a few things she will need to stay overnight.

 Should get a report in an hour or so, and she will be home tomorrow.

Thanks everyone for your good wishes.

MJM460

[propforward]

All the best for a speedy recovery! Definitely best to get in and taken care of asap.

[MJM460]

All home with bones reset, screwed together with a little plate and a new cast.  She says it definitely feels much better, so on the mend now.

But does not look like much shop time for a few days yet.  One arm in a sling definitely requires extra assistance. 

Also, lockdown has eased a little and we have some family visit and retail catch up to do.

Thanks for all the good wishes.

MJM460

[gary.a.ayres]

Hi MJM -

so sorry to hear about your wife's accident. Doesn't sound like it was a great deal of fun for her, and must have been a shock for you too.

However, I'm sure you will do a great job of looking after her, and am pleased to hear that she has begun to recover already.

And the engine will still be there waiting for you...

gary