Stuart Major Beam Engine

[Chipmaster]

Yes Dave there is room for improvement with my needle filing skills in particular I need to avoid a tendency to have a rocking action. I think I have produced concave surfaces at the top and bottom of the slot. Need to buy some more needle files with various profiles and safe edges. As you say there is plenty of meat left in the piston rod around the slot.
Andy

[Roger B]

Excellent progress    Trefolex is good but in my communal cellar it is 'Verboten'. I have to use odourless cutting compounds.

[Chipmaster]

Morning Roger, when I look at the plans and parts list for the Major beam engine the end seems a very long way away.
Not being allowed odours in your communal cellar must be awkward at times. How does hot cutting oil from lathe work go down?
Andy

[Roger B]

I use Weicon Bio-Cut which avoids most of the problems:

https://www.weicon.de/media/pdf/56/1f/05/TDS_11750400_EN_Bio-Cut.pdf

It's not cheap but works well, otherwise I have to be careful to keep all the swarf in my area and not leave dirty door handles etc.

[Chipmaster]

Gosh Roger I wouldn't last long in that environment!

Andy

[Chipmaster]

My next task was to make the two radius rods that are part of the Watt Parallel Motion Part 76 on the extract from the plan,
Parallel and Radius Rods by Andy, on Flickr

Using 5/8" diameter EN1A steel bar I machined two bars to the exact overall length of the motion rod plus a stub at each that was centre drilled and turned down to 7/32", the eventual thickness of the rods.
Machining parallel motion radius rods x 2 by Andy, on Flickr

Machining parallel motion radius rods x 2 by Andy, on Flickr

Flats were then milled on the ends of the bars, sufficient for the formation of the eyes or ball ends. The 7/32" diameter stub on the end of the embyonic rod served as a guide for milling to the required thickness.

Machining parallel motion radius rods x 2 by Andy, on Flickr

Machining parallel motion radius rods x 2 by Andy, on Fllickr

Back in the lathe the embryonic rod was carefully set up in a quick change boring bar holder to ensure the bores were parallel and the correct distance between centres.

Machining parallel motion radius rods x 2 by Andy, on Flickr

Machining parallel motion radius rods x 2 by Andy, on Flickr

The rods were then roughed to the profile of the ends of the rods. The eye was supported by a close fitting plug with 5/8" diameter flanges to act as guides.

Machining parallel motion radius rods x 2 by Andy, on Flickr

Machining parallel motion radius rods x 2 by Andy, on Flickr

A Radtord type ball turning tool was used  to machine the radiused eye ends of the rod. The outward end was supported by a live centre and a close fitting steel plug was fitted in the bore of the eye to prevent distortion.

Machining parallel motion radius rods x 2 by Andy, on Flickr

Machining parallel motion radius rods x 2 by Andy, on Flickr

One end finished and the stub removed note the close fitting steel plug fitted in the bore of the other end to prevent distortion when turning between centres.

Machining parallel motion radius rods x 2 by Andy, on Flickr
Machining parallel motion radius rods x 2 by Andy, on Flickr
Machining parallel motion radius rods x 2 by Andy, on Flickr

The finished end was protected by thin brass strips and held in an independent four jaw chuck. The other end supported by a live centre. The rod was reduced to the require diameter by taking only small cuts to minimalise the risk of bending the rod. The angle of the top slide was altered at interals along the rod to achieve the fish bellied form....almost!

Machining parallel motion radius rods x 2 by Andy, on Flickr

Finished, the form is not perfect but they should be functional, I hope. However, I have to make several other parts before I find out.

Parallel motion radius rods by Andy, on Flickr

Parallel motion radius rods by Andy, on Flickr

Andy

[gary.a.ayres]

Good looking parts.

 

[Chipmaster]

Thanks for complementing my parts Gary.

Andy

[Chipmaster]

Making further parts of the parallel motion has been interrupted by spending time running my engines to ensure they are ready for three local events over the next six weeks.

This post concerns the radius rod bushes part 77 and the radius rod pivot pins part 78.

 Radius rod pivot pin and bush by Andy, on Flickr

I opted to use bronze for the four bushes. Milled the bar down to half it's thickness then silver soldered the two halves back together ready for machining in the lathe. Enough for four bushes and hopefully a spare.

Split bushes for radius arms by Andy, on Flickr

External diameter machined down to 13/32" and internal diameter bored and reamed to 9/32" diameter.

Split bushes for radius arms by Andy, on Flickr

Then parted off each bush using a very thin parting off tool.
Split bushes for radius arms by Andy, on Flickr

Bronze bush about to be heated so the two halves fall apart when the silver solder melts.

Split bushes for radius arms by Andy, on Flickr

After heating to melt the silver solder they fell apart becoming a pair of bronze split bushes. The rough surfaces of the silver solder will need to be filed flat so that the two halves form a circular bearing. I also filed small marks in the edges so that the halves could be matched and identified.

Split bushes for radius arms by Andy, on Flickr
Split bushes for radius arms by Andy, on Flickr


Bushes fitted into a radius arm, they are a close fit.
IMG_0131 (2) by Andy, on Flickr

Machining a radius arm pivot out of mild steel.
Machining a radius arm pivot. by Andy, on Flickr

Radius arms and their pivots.


 [url=https://www.flickr.com/photos/116764188@N08/]Andy, on Flickr

Assembled

Radius arms fitted to the pivots by Andy, on Flickr

Mounted on the entablature

Radius arms fitted to the pivot then attached to the entablature. by Andy, on Flickr

Radius arms fitted to the entablature. by Andy, on Flickr

Now I'll have to make the pivots again because the threaded section was barely long enough, I hadn't realised how thick the entablature is.

I'm considering the bronze bushes may need to be retained in the radius arms by loctite or tiny grub screws if alignment is not perfect. I have noticed set pins or screws through the eyes of the radius rods in pictures of the parallel motion on some Stuart Major engines. Can other ST Major constructors or owners advise?

Andy

[Alyn Foundry]

Hi Andy.

Perhaps a daft question but why " split " bushes? There doesn't appear to be any adjustment in the links you recently made.

Cheers Graham.

[Chipswitheverything]

Hi Andy, good progress on the pesky little split bushes.  Graham, they need to be split because of the assembly method required by the Major design, so that the bushes are placed on the bearing surface and the hole in the oval rod ends slid over the bigger diameter of the bearing end.  Andy, I used 10 BA bolts at each end of the rod to lightly nip the bushes into place, might be some help to put a dimple into the split half that the bolt lodges against, and maybe a splodge of threadloc on the tiny screw on final assembly ( as the bolt or screw can't be tightened much without pinching the bearing ).  It's not the greatest engineering arrangement, but it does allow dismantling.   Dave

[Chipmaster]

Hello Graham, agreed there is no adjustment and split bushes do seem a complication that could be avoided if the pivots were made in such a way that the flange on the end could be removed and a solid bush fitted and retained. As per the plan the two halves were fitted to the solid pivot then the radius rod pressed over the split bush. Perhaps I should add some more pictures to illustrate how they are assembled.

I had thought that there was an easier way to achieve the end result with the pivots and bearings. However, I usually enjoy the challenge making these fiddly bits. There have been several stages in this build when I’ve thought the design is plain awkward for my ability and equipment but I reckon and hope these parts and embellishments will enhance the final appearance of the model if I get it right.

Andy

[Chipmaster]

Hi Dave,
you beat me to it.

Thanks for the succinct response and explanation of how you retained the pesky little bushes.

Andy

[Jasonb]

You could do solid bushes if the pin just had the flange on the head end and a longer thread that could go through a separate flange and spacer. The other option which I'm sure you don't want to do now is have marine type ends on the rods.

Taking the 10ba screw option further a small square headed setscrew and locknut may look the part.

Good progress anyway, I better get on with those drawings!

[Alyn Foundry]

Thanks Guys.

Going back a couple of photos I can now see that it was a daft question, a second cup of coffee might have helped before posting!

Cheers Graham.