Author Topic: Stuart Major Beam Engine (Read 88800 times)

gary.a.ayres · « **Reply #315 on:** August 31, 2020, 12:00:01 AM »

Great progress.

The engine already looks stunning.

Chipmaster · « **Reply #316 on:** September 27, 2020, 09:53:47 PM »

Valve Motion Links.

Valve Motion Links by Andy, on Flickr

I used two 5.1/2” lengths of ½” diameter mild steel which would allow for stubs on each end that would be centred and could also be held in a chuck for the finishing operations. The stubs were 1/4” long, turned down to 7/32” diameter and centre drilled. The ends were also drilled 1.8mm – the 8BA tapping size.

Valve Motion Links by Andy, on Flickr

Each piece was mounted in a square collet block for a pair of flats to be milled on each end. The set up was sufficiently rigid to mill opposite ends in one sitting with the stubs acting as a guide to the milling depth.
The centres for the bushes were carefully marked out drilled and reamed to 5/16” then brass keepers were lightly pressed in to preserve the shape when the job would be supported by a live centre.

Valve Motion Links by Andy, on Flickr

Valve Motion Links by Andy, on Flickr

The eyes were rough turned using a 6mm button tool prior to using a ball turning tool to produce the radiused eyes. I forgot to take pictures of the ball turning tool session.
The button tool was used to machine the diameter down to about ¼” before machining the fish bellied shape, working on one end then turning the job round for the opposite end. The button tool produce a good finish throughout the job.

Valve Motion Links by Andy, on Flickr

Valve Motion Links by Andy, on Flickr

With one end held in a chuck and the other supported by a live centre, the fish bellied shape was machined by altering the angle of the topslide. I set it to 2.5˚ for the first section nearest the eye then 1.5˚for the next section starting about an inch from the eye leaving a parallel section about an inch long in the centre where I settled for a diameter of 0.22” - very close to the 7/32” specified.

Valve Motion Links by Andy, on Flickr

The job was then polished with aluminium oxide cloth while it was spinning in the lathe.

Valve Motion Links by Andy, on Flickr

To finish off the 1.8mm holes were tapped 8BA then stubs were sawn off and the ends rounded off by filing. The 8BA hexagon head screws retain the split bearings, to be made next week.

Valve Motion Links by Andy, on Flickr

Valve motion links without bearings hanging on the crosshead.

Valve Motion Links by Andy, on Flickr

Andy

gary.a.ayres · « **Reply #317 on:** September 28, 2020, 12:14:00 AM »

Not a small job, a Stuart Major. But great progress...!

Chipmaster · « **Reply #318 on:** September 28, 2020, 07:56:44 AM »

Yes indeed Gary and at each stage the next part always feels challenging.

Andy

ettingtonliam · « **Reply #319 on:** September 30, 2020, 03:54:18 PM »

i've just done a set of 4 fishbellied links for my 7 1/4" gauge Locomotion. I did much the same process, turn spigot at ends, drill through for bushes and machine the flats, but I turned the rod section down to maximum diameter, and a short section at the ends to the minimum diameter. Then with lathe on top speed I did the fishbelly shape with a series of files of increasing fineness, finishing off with emery tape. Crude compared to yours, but its worked.

Chipmaster · « **Reply #320 on:** October 10, 2020, 09:15:46 PM »

Hello Richard, as long as we're happy with the result, that's the main thing. I also had to use a file to get the fish bellied shape.

I think you were building a Alyn Foundry Robinson Hot Air Engine, how are you getting on with it?

Andy

Chipmaster · « **Reply #321 on:** October 10, 2020, 10:38:05 PM »

Last week I made the four pairs of bronze split bushes (28) that fit in the eyes of the valve links made the previous week together with the two pins (29) that attach to the valve levers.

Bushes and pins by Andy, on Flickr

S Major 1275A by Andy, on Flickr

I didn't take any pictures of the process because it was exactly the same as for the bushes in the Parallel motion and making the two pins wasn't interesting.
However, when I attempted to fit the bushes on the valve crosshead (that had taken ages to make) I discovered that I hadn't machined the crosshead journals down to the correct diameter of 13/64", mine were 0.22" about 17 thou oversize

Not being prepared to make another valve crosshead meant that I had to open up the split bushes which took quite some time to get them to fit. I can always make two new pairs of bushes to fit the oversize journals if my 'modified' bushes aren't up to the job, they're just a bit thinner than specified.

I won't pin the valve levers to their shaft until I have checked the operation of the entire valve gear from eccentric to slide valve.

S Major 1280 by Andy, on Flickr

S Major 1281 by Andy, on Flickr

The next item to make is the Valve Hand Lever, which looks interesting, have other beam engine builders made their valve hand levers in one piece or attached the elliptical handle over a screw thread?

Valve Hand Lever by Andy, on Flickr

As I don't have a 5/64" broach for the keyway in the hub and that size is probably unobtainable, I have decided to bore the boss of the lever to 7mm which is only 0.0056" under the 9/32" in the drawing and use a 2mm broach bought from ARC Eurotrade. The shaft the handle fits on will be machined down from 9/32" to 7mm.

This will be a hi-viz part that I have to get right!!

Andy

gary.a.ayres · « **Reply #322 on:** October 11, 2020, 11:09:02 AM »

The odd glitch now and again is inevitable in a project of this magnitude, but wow!

It's looking fantastic...

Chipmaster · « **Reply #323 on:** October 11, 2020, 02:02:04 PM »

Cheers Gary, reckon I misread the drawing then machined the journals down to 7/32” instead of 13/64. Fortunately I was able to work around that mistake.
Andy

Chipswitheverything · « **Reply #324 on:** October 11, 2020, 02:36:27 PM »

Hi Andy, pleased to see the engine coming on well once more. Those split bushes are a bit of a game, to be sure, quite a lot of work that no one is aware of when the thing is assembled.. I made the valve hand lever in one bit, though I don't suppose that two parts would present any problem if preferred. As you propose, I left the pinning of the levers on the shaft until I could see what was going on with the system as a whole, and the valve hand lever and the little levers could be lined up and adjusted side to side to fit happily with what you have actually made. Dave

ettingtonliam · « **Reply #325 on:** October 12, 2020, 07:53:14 PM »

Quote from: Chipmaster on October 10, 2020, 09:15:46 PM

Hello Richard, as long as we're happy with the result, that's the main thing. I also had to use a file to get the fish bellied shape.

I think you were building a Alyn Foundry Robinson Hot Air Engine, how are you getting on with it?

Andy

Hi Andy
Yes, I'm doing the Alyn Foundry Hot Air Engine. Knowing that I was going to have to part with my large lathe, I did a lot of work in a short time to get the major castings machined. Since then, its slowed down a lot. I've polished and drilled/reamed the links, and am about to have another go at the regenerator. I keep getting the bits out and looking at it. Really, there no reason why I can't just get on and finish it.

Chipmaster · « **Reply #326 on:** December 01, 2020, 09:13:51 PM »

It's nearly two months since I made any Stuart Major parts, I was distracted making the Retlas Manchester Dynamo, now I'm waiting for dynamo materials so I'll resume work on the ST Major.
.
The next part to be made is the Valve Hand Lever, I'll try to adhere to the drawings as far as the shape goes but the most important dimension is the 15/16" between centres of the 4BA clearance hole and the centre of the hub which will influence the amount of valve travel.

I haven't made a lever like this before and was uncertain how to go about it. To make the lever in one piece it seemed the elliptically shaped end of the lever should come first and I started with a form tool followed by a radius turning tool.

Radius turning tool

Parting tool

Form tool again.

Polished while still in the lathe.

Then milled flats on each side to a thickness of 5/16"

That was it for today.

Andy