Another Stuart Major Beam Engine ( some comments and photos)

[Don1966]

Dave thanks for showing a well demonstrated use of the finger plate. Don't you just love how well it works? I keep mine on the Pillar drill.DON

[Chipswitheverything]

Hi Don, every model engineer should treat themselves to a finger plate, even if they only fancy an intriguing paperweight!   I only made this a few years ago, but I was thoroughly pleased with it, it is certainly very useful and has got a chunky sort of appeal.  This one is a bit bigger than the size given by Geo. H Thomas. ( Sorry, this should really be in the tool section....)
  For many years I was fortunate and privileged to often visit George Thomas in his fine workshop here in the south of England.  On his surface table were always the finger plate, the miniature scribing block and the rule holder to his own design. I've made up the latter two items as well...  Dave

[10KPete]

Gentlemen:

How big is that plate? I know how big I would make one but I'm curious how big that one is. 

Pete

[Chipswitheverything]

Hi Pete, just nipped out to the workshop to measure the thing!, it's 3 1/2" square by 5/8" thick...    I think the original design was for 3" by 1/2" thick.  Just depends what stock you have and the sort of components you work on.  I'd say the bigger size is a good one.   Dave

[10KPete]

Thanks Dave!  I was thinking 3 1/2 to 4 but that was before I started giving serious thought to these small engine models. Said models seem to be the way I'm going as I get older. Used to be that I wanted to build a H&M about 2 1/2" bore but the one on
the drawing board is 1 1/4" bore. And even that is looking large now! 

Pete

[Don1966]

Pete the original design from Hemingway is 2.5" by .75" thick. Love the photos Dave. This is the one I built quiet a few years ago.



Don

[10KPete]

Thanks for the pics, Don. What is the big screw knob on the back side used for? Do you attach the plate to the pillar tool sometimes?

Pete

[Don1966]

Yes I do Pete with the big screw knob you see. That's where it stays....

Don

[10KPete]

Thanks Don.

Pete

[Chipswitheverything]

Been a bit too busy being distracted by getting the bits of my Stuart Steam Hammer almost done! ( and the usual "life gets in the way" stuff...)    But here are a few, not too great, pictures of the beam engine parallel motion.
 
  The second photo of the assembly gives an idea of the close clearance that exists between the headed pins that support the radius rods and the extreme width of the moving links themselves - the clearance is about that shown in the upper gap, ie. not a lot!

  I've seen a few engines, and certainly others in photos , that have run into alignment problems here, and the builder has had to thin down the heads of the pins or adopt some subterfuge.  Stuart Turner did not give a GA of the plan view of the motion work, or even a scrap view, but a good drawing ( though the side view GA is no more than a guide to where to put the bits! ) would be a helpful alert to the builder.  I suppose that someone a bit more switched on than me might have made their own, or added up all the dimensions...!  But you do tend to assume that there will be a bit of room...

 Nevertheless, because the componentry that mounts from the spring beam - the motion work, and the tapered strut that links spring beam and cylinder boss - are separated by some considerable distances from the base mounted components ( both in vertical distance and along the length of the engine ), there is a good deal of error that can creep in by extrapolation of quite small discrepancies.  I had the same sort of trouble as Andy (Chipmaster) experienced when trying the correspondence of the end strut hole on the spring beam, with the hole in the lug on the top of the cylinder. ( I'll say a bit more about this later on, I think that both of us met the same  difficulty with the slightly "off" cylinder casting ).

 As for the motion links, I did use a bit of a naughty technique to get the cotter slots looking crisp.  I didn't much fancy my chances with drilling and needle filing. The slots were put in with a slitting saw, while the links were still largely solid blanks. Then loose gap pieces were pushed in, width of cotter and gib, which spaced off the material for the end closure of the links.  The links were drilled through, about 7/64" if I remember from over 25 years ago!, and the pins riveted and flushed. They can't be seen, and for an engine that will only ever do some gentle demo running, there's plenty of strength there.
 As I wondered if the bearing centres would be quite consistent between all four links, with the component stack, I drilled slightly undersize and opened out to finished dia. with the links assembled  ( think that I jigged them up on the mill table and used my little Geo. H. Thomas design boring head...)

Cheers, Dave

[zeeprogrammer]

Nice to see an update.
Those pictures are intriguing. Need more. 

[10KPete]

Nice work. I've always liked the way those original designs took care of adjustments.

Pete

[Chipswitheverything]

Hi guys, thanks for the comments.
 The components that make up the big and little ends of the con rod are quite similar to the elements of the parallel motion links, and were done using the same kind of sawing and pinning technique.  In the cast iron rod casting itself, I put three small pins in the big end, and two in each side of the small end.  I've made the straps the same width as the rod ends. But what I thought was a mistake on the Stuart drawings, with the strap width narrower than the cast rod ends, does actually seem to be intended, (I've seen a superb example of the Major beam done that way ). I don't think that it matters which route is followed as long as the dimensions are checked out for either scheme.
 Gauge plate form tools were made up to do the decorative rings while the rod was between ctrs. in the lathe.  The taper in the centre area was worked in by small adjustments of the top-slide to create a shallow curve.   ( Sorry no photos, it was all a long time ago! ).    Yours, Dave

[Chipswitheverything]

One photo didn't load for some reason....

[Jo]

Nice Dave 

  Now I'm getting the desire for a set of Stuart Major Beam Castings. Not that I would have anywhere to put the finished model  .

Jo