The Bolton No 5 Vertical Open Column Steam Engine

[gary.a.ayres]

Great progress!

[MJM460]

Thanks Admiral, Bear, John and Gary, it great to have you all looking in, and your comments are much appreciated.

It’s almost a full month, but at last some progress on the eccentric strap.  I know what Stewart means about proceeding with sloth like speed, especially when beautiful weather outside beckons to other activities.  Here it is Autumn (Fall), and the nicest time of the year around here.  And to top it off, we have an Easter holiday time during which almost everyone who has the opportunity goes camping.  Or in our case, a little sailing.  But at last, the minute daily progress has added up to something to post.

You might remember that the casting kit included a casting for the eccentric strap.  Another difficult beast to hold, not to mention that I made things hard for myself by making the eccentric first.  The first thing was to carefully measure out how the part could be extracted from the casting, and plan how to achieve it.  My making a practice piece from aluminium showed that I needed the little tab for the wrist pin flush with one side.  And of course, the final part is only 5 mm thick. 

One side of the casting was nicely machined flat when I received it.  The machining marks confirmed that it had been done on the lathe in a 4-jaw chuck, with the centre about the centre of the hole for the eccentric.  I think with my 8 inch chuck, the chamfer on the jaws would make for a very precarious grip before I could finish to 5 mm thick.  Instead, I supported it on parallels in the vice using the machined face for reference and used my 32 mm face cutter to face the second side, parallel to the first.

With two parallel faces I was able to mark a reference face for the tab, and locate the bolt centrelines for the big end bolts.  I set the casting up vertical in the vice, located the two bolt centres, drilled through 2.5 mm for tapping M2.5, and finally opened up to 2.5 diameter to the required split line.  Couldn’t tap the threads at this stage, as the tap is too short, so next step was to split the big end with my trusty cordless hacksaw and natural material guide. I thought about machining the cut faces flat, but could not see how to line up the awkward shaped parts, so I followed the directions and achieved a good surface with a file, and finally flattened each side with emery paper and a flat plate.  Then, I was able to set up the top section and tap the threads for the bolts.

Back on the parallels, I machined one side down to the face of the tab, then turned it over and took a light skim.  I located the centre line on the split line and drilled out in steps to 12.5 mm diameter, then set up the boring head to finish to the required 14.01 diameter for the eccentric.  When I took the final cut, I had a fright as it seemed like I had overrun.  However, nothing to do but proceed and skim to 5 mm thick to fit between the eccentric flanges.  I checked at each adjustment of the quill that a feeler gauge would fit between the cutter and the vice jaws.  I made it, with a 0.35 mm feeler gauge still fitting under the cutter!  Finally I was able to bolt the strap around the eccentric, and despite my fears, it fitted quite well.  A bit tight, but a little fettling and fiddling, definitely a keeper.

Next step is to make that tab fit the clevis on the end of the valve rod.  I may need to make a new valve rod, a little longer, still too close to call.

MJM460

[Bear]

Very nice.

[Kim]

Nice sequence of operations, MJM!
I especially like your cordless hacksaw!  Powered by chocolate chip cookies?

Kim

[MJM460]

Thanks again Bear for looking in.

Definitely powered by choc chip cookies Kim.  Ice cream and coffee also work well.

I often look at the electric hacksaws when I see others using them, but honestly, so far, a new blade of the best quality I can find, and a solid frame has done everything I need quite well.  And it doesn’t take much space in the shop.  Perhaps if I ever decide to make a tracked vehicle and need mass produced track plates......

Not much progress to report today.  I decided to clamp the strap to the tooling plate on the rotary table to finish machining that tab.  And of course, there didn’t seem to be any holes in the right place to hold the part.  Seems to happen often, but it never seems to be the right day to disturb something I have already set up to enable drilling the required extra hole.  So today’s shop time was spent drilling and tapping M6 holes in a 14 mm steel plate.  Will do a few more tomorrow, then I will be able to hold the part securely to face the tab, drill the wrist pin hole,  and think about profiling the part between the strap and the tab.

Thanks everyone for looking in,

MJM460

[MJM460]

It has taken the last two weeks of my shop time to complete the eccentric strap.  Of course having to drill extra holes in the tooling plate, and two sisters in law having 79th and 80th birthdays (involving a four day break, over 300 km away) did not help.  I don’t know if my M6 tap is getting blunt, or if hand tapping holes in 12 mm steel plate is just hard work.  Two holes would have been enough to clamp down the casting, but I get caught so often with needing an extra holes, but wasting time on a workaround rather than re centre the rotary table after moving things to drill and tap the holes, so after the required two, I kept going, and did a dozen in total.

The first photo shows the plate, with the casting placed to put the hole for the wrist pin over the centre when it is all mounted on the rotary table.  You can see that the existing holes are either too close or too far away.

With the extra holes drilled, I clamped the casting with the tab in position on a piece of scrap aluminium for drilling the wrist pin hole.  Then I off set the table to get the required 5 mm diameter and profiled the tab.  As others have mentioned, the rotary table is a great device.  Then I moved the casting and clamped it with the tab for the wrist pin over hanging the end so I could measure the thickness with a micrometer as I machined it to thickness to fit the clevis on the valve rod, and forgot to take a photo.

The outline of the casting needed some tidying up, so the next step was to centre the hole for the eccentric over the centre of the table.  I worked out that 5 degrees would make a suitable taper on the strap between the two ends.  First time I have done this sort of operation, but it’s all learning.  I worked out how much to offset the axis each side, and set the travel stops on the mill x-axis and had a go.  Cameras are cruel devices.  You can see all the mistakes I made in a later photo,  perhaps I need a better light, or just to look more carefully before I move anything.  I thought I had cleaned off all the swarf before clamping down after shifting back to the centre, but you can even see that I did not succeed there.  However, without the eagle eye of the camera, it does not look so bad, and it cleaned up nicely with smooth file.

I did not want to just machine off the step in the casting, and decided to add a little feature as a means of trying out a ball end cutter I purchased a while back.  As the hole for the eccentric was now centred on the table, I rotated the table rather than machine straight across for the end of the step, though it is barely visible, then machined a groove down the centre to make two ribs.  Not great art, but I am quite pleased.

With the strap machining complete, I was able to do a trial assembly.  It really starting to look like an engine.  Looks like I got the position of the tab in the right place relative to the thickness of the strap end, so the top and bottom ends of the engine do at last properly match up.  Forgot to put on the valve cover, but that item was completed earlier.  To early to get excited, as there are a few little details to tidy up and complete, and it’s a bit stiff to turn over, so some tracking that down too, then we will see.  Definitely on the home straight.

Thanks everyone for looking in.

MJM460

[Bear]

Looking great. It is always nice to be on the home stretch. As an aside, your photos were helpful for me as I am struggling with a connecting rod on mine. The set-up you show should work nicely for mine as well.

[RReid]

Your treatment of that "step" in the casting came out really well, adds a nice bit of visual interest.

I've been working on the eccentric strap for my project, and it also seems to be taking an inordinate amount of time.
Wife: "What did you work on today?"  Me: "Eccentric strap.:  Wife: "That's what you were doing yesterday, is it done now?"  Me: "No."

[MJM460]

Thanks Bear, and good to know that you are still hanging in there on your engine.  Glad you found my pictures helpful.  That strap is tricky to hold securely while still allowing access for the machining operation.

When I first tried using the rotary table, I found it difficult to see how to clamp the parts I was making, and what order to align which with what.  I found that tooling plate plus a few carefully made pins made setting up and clamping small parts on centre to acceptable accuracy much easier.  But I am sure there are others on the forum with additional and better methods to facilitate alignment.

Hi Ron,  thank you for the comment on my attempt to add my own stamp to the eccentric rod.  But I know what you mean about the part taking a long time.  Each operation takes seconds, but the setting up, and thinking before the cut takes all the time.  And so many operations.  But it is nice to reach this stage.

Not much progress today, first COVID shot this morning, no reaction so far, Mother’s Day dinner with our two sons and their family’s this evening.  Maybe tomorrow.

MJM460

[Craig DeShong]

MJM

Yea, those in-law birthdays really cut into the shop time. 

Really looking like an engine now.  A few more parts and you’ll be read for for some parts to go up-and-down while others go round-and-round.

[MJM460]

Hi Craig, thanks for looking in.  Not quite there yet, but only a few little items to finish to allow the engine to turn over properly.

 The remaining items can be identified now all the components have progressed far enough to allow a trial assembly to check for any tightness or interferences.

I have already noted that it was a bit stiff to turn, and a little exploration by disconnecting parts, loosening bolts managed to identify the main culprits.

The eccentric strap was not turning freely on the eccentric.  A little blue ink from a marker pin showed it was likely the sharp corners on the strap rubbing on the small radius on the inside of the flanges of the eccentric.  A little work with a counter sink, hand held, soon cleared the corners, and freed up the strap.  Indeed it is now clear that I had indeed bored a touch large on diameter as I originally feared, but I feel not enough to stop the engine running.

The main bearings were also binding a bit.  No problem when the bolts were slackened a fraction.   Carefully retightening then a final run through with the reamer with the bearings in place freed them up nicely.

The next item was that the sides of the eccentric strap interfered with the baseplate.  The drawing gives the width of the strap as 25 mm, but I felt there was not enough clearance around the bolt heads, and managed to get 26 mm out of the casting.  But of course the shin bone is connected to the knee bone, and so I had to chew another 1 mm out of each side of the cavity in the base plate, to allow for the extra width.

Then I needed to return to the top and bottom heads.  The spigots on each head which enter the end of the cylinder, were both actually blocking the steam inlet ports.  A job I knew needed doing, but had put off while working on other components.  It turned out to be the most interesting.  With the parts all assembled, but the top head removed, it was surprisingly difficult to push the piston down to turn the engine.  Removing the conrod showed that it was not the shaft issues causing the problem.  I thought the piston fit was better than that, but it’s a while back now, and I was starting to wonder.  I could push the piston down but with difficulty and a distinct squeak as it went down.  When I lifted the bottom head, the piston was quite free and dropped on its own weight.  And a 16 mm diameter piston does not have much weight.

Sure enough, the spigot on the bottom head was completely blocking the steam port.  Clearly the piston fit was quite good, very good seal with minimum friction.  Should be good for running on air, but I wonder if expansion will be a problem for running on steam.  But that will have to be an issue for later.

I set up each of the heads in turn, and milled a little pocket to clear the steam ports at each end.  I used a feeler gauge to check that there was clearance under the cutter so I did not scratch the gasket sealing face.  Sure enough, when the cylinder was reassembled, it all moved freely.  I must admit that I did not expect my piston fit to be quite so good.  I hope I can repeat the feat next time.

Finally, the steam inlet port in the steam chest.  I had left that in with the idea that I could do it when I had a better idea of the boiler layout.  The boiler has not progressed, so I made it the same side as one of my other engines, set the steam chest up in the vice with plastic pads each side to prevent damage, and drilled and tapped M6.  While it was set up, I made a small 8 mm dia. counter bore with a milling cutter to give a flat surface for the inlet fitting.

With all that now done, I have spent this afternoon making some brown paper gaskets, and assembling the engine. 

I set the valve with the piston at top dead centre by adjusting the valve to be just starting to uncover the port when the crank rotates in the required direction, the edge of the port was just the merest line appearing at the edge of the valve.  Then locked up the eccentric.  Turning the crank to put the piston at the bottom showed the bottom end was also satisfactory.  I must have got the valve length about right.

One more job to do, I should have provided two set screws in the flywheel.  I have learned the hard way on previous engines, that one is not enough.  Obviously a key would be better, but I don’t have a broach.  And I am not sure how practical it is on a 1/4 inch shaft.  That will be tomorrow, if my other commitments allow.

Definitely getting close now.  I had better see if I can remember how to sign into u-tube in preparation for the video!

Thanks to all for looking in.

MJM460

[MJM460]

I drilled and tapped the flywheel for that extra set screw this afternoon, so here it is, all assembled and adjusted ready for a first test run on air.

And at last a little video to show it does run.  Hooray!  The compressor is on the minimum blowoff pressure setting, around 10 psi or 70 kPa, and the pressure on the tyre inflation gauge being used to connect to the engine reading about 5 psi.  How accurate it is at that pressure is anyone’s guess.

<a href="https://www.youtube.com/watch?v=A1A-hB8e1qE" target="_blank">http://www.youtube.com/watch?v=A1A-hB8e1qE</a>

Now for some finishing touches. 

I need studs for the steam chest.  A bit of a challenge as I don’t have a collet that will hold 2.5 mm diameter. 

I am happy enough with capscrews for most other locations, but need to replace some with the correct length.  Needs a trip to the bolt shop.

I have also used commercial nuts in six places.  They don’t look right and I will make some replacements more like the ones I made for the crosshead pin and valve pin although surely I can think up something more elegant for those nuts on top of the columns.

Finally the cylinder cladding.  Job has shown the way with machining the outside of the cylinder flanges, but I am still thinking about where to put the fixing screws.  Not much vacant space on an engine this size.

Thanks for looking in,

MJM460

[crueby]

Looking great, sounds like just a few finishing touches to go. 

[MJM460]

Thanks Chris.  Thanks for looking in.

I have the video made, in iMovie, and have totally forgotten how to upload it to YouTube!

I know that I have done it before, and can see all my previous videos, but can’t find an upload button.

IMovie allows export to just about everything else.  Can someone please give me a few reminders of the procedure?

But it’s definitely a runner!

MJM460.

[crueby]

I dont know imovie, but for mine I go into youtube, upload button at the top, and select the file from there.