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Triple tinkering : three times the fun?

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Chipswitheverything:
At odd times since late autumn I have been making a start on a certain amount of machining of the castings and some other bits , of a Stuart Turner triple expansion engine.
This is using an unopened set of Henley on Thames castings that I bought s/h back in 1986.  Elsewhere in my past posts I've illustrated the set, in connection with a discussion on the forum about the poor quality of the present offering from Stuart, when a member bought and returned an unsatisfactory and now very expensive set of castings and bits.

With other projects to see to, I'd kept the set that I bought in the unopened condition, wondered if I might have sold it. But after finishing the Quorn grinder and the big beam engine, and then just doing a few very minor tool projects while nothing much was going on, I decided that the triple might stimulate my interest again.  Which it has.

Jo has written up a magnificent build log account , the Triple Orphans, about her experiences with almost all aspects of making the ST Triple - very useful to have been able to refer to what Jo has said and illustrated, and I have and will be using many tips from that write-up.

My model engineering activity is very much on an as and when basis, the workshop was too chilly for some winter months, and I just have a session in there when time and inclination permits.  So I'm not logging this build, may just add a few things as they eventually happen.

Photos indicate progress to date, I'll put a few up of some set-ups on components with a few remarks.  ( If anyone wonders why there seems to be drops of water on the engine, it began to suddenly rain just while I was taking a photo outside ...!) Dave

Sanjay F:
Watching, watching, watching!!  :popcorn: :ThumbsUp:

I have an old set of Triple castings stashed away for a retirement project when I should hopefully have the time to devote to a fantastic project and engine!

Good luck with your build!  ;D

CI:
 :ThumbsUp:

Chipswitheverything:
Thanks guys ...     Having made the split bearings for the crankshaft, and found that a length of 3/8" silver steel would turn around with reasonable freedom in them when they were installed in the bedplate, thoughts turned to the triple throw crankshaft.
At the Guildford show I had seen the broken bits of the crankshafts that Jo had valiantly tried to make from the inadequate blanks supplied by Stuart Turner, as shown on her forum build log also. I had just such a blank, the three blocks pinned and brazed to a rod, and probably would have tried to use it for the between centres turning, but for the warning.
The heroic method of traditionally turning the crankshaft from a mighty steel bar, ending up with about 90% of it in swarf was not appealing much to me. Even with various kinds of ingenuity to try to support and stiffen the increasingly fragile and long 'shaft, I thought that the chance of a late stage bang-up and disaster was quite high, apart from it being laborious and offering a good chance of me making some kind of stupid mistake along the way.

So, I have gone along with the Loctite and pinning fabrication as illustrated by Jo.   This seems to have worked out well, and I feel happy that it is amply strong for a little engine that is only likely to do the very occasional demo run.
As it was easy enough to do, I pinned through at both ends of the webs, with 1/16" silver steel pins, though the screw thread retaining the crank weights does also lock one end.

When I came to trim the sawn away ends of the shaft between the webs, I decided that it might be best to do the milling with the bar of the shaft supported in Vee blocks, rather than hold the webs in the vice and hope that the bonding and pinning took the milling strain.  I think it would have done, I took the trimming gently, but didn't want to take any chance ...

When it came to the Loctite-ing of the webs, already equipped with their crankpins, to the shaft, I devised a simple jig arrangement using the table of the TS Junior mill.   There isn't too much time to fiddle about when using the Loctite retainer, and I had a vision of bits of packing and angle gauges tumbling at a critical moment when I anointed the components and moved them back to precise position.
The photo shows what I did.  Held a piece of bar in the collet on the vertical head, the bar was cut away like a D-Bit, with a flat at about half thickness. And the width just fitted between the half- inch of the web and crank-pin dimension.
With the c'shaft in vee blocks secured to the milling table, I could move the web very precisely to spacing position, and at the same time, lean the 'pin back against the flat to maintain the angle.  This worked out well, because the webs could be moved aside to apply the L/tite, twirled a bit, and then immediately popped back into certain position with nothing else moving.

Trimmed up, the crankshaft turns sweetly in the bedplate bearings, I didn't specifically check for any distortion but as it seems fine there probably is not much.
The defunct ST crankshaft blank, seen perched on the mill table, did come in handy for a while, as a visual check on getting the crank angles disposed correctly.   Dave

Chipswitheverything:
The balance weight castings , six of them, are quite neat small castings, and on the face of it don't look as if there is too much to do to have them ready.  But they need to be machined all over, and preferably brought to a nice finish to match the steel crank webs.
I started by bringing the castings to width in the four jaw chuck, cleaning up both sides  : then making the 1/2" wide slot , to fit the webs, that becomes the datum for the rest of the shaping up.  The slot fitted on a short length of steel bar with a hole drilled to match the position of the crankshaft centre.

As per the photos, the castings could then be in turn drilled axially on the mill.  I've used 8BA cap screws to secure the weights, with the small thread tapped full thread in the cranks for best strength.  Didn't go in for the Stuart method of peening over the 7 BA studs, have heard of the castings splitting during that operation.
The holes to clear the screw head will be plugged and faired off later. When I attached the weights, I roughed up the mating surfaces a little with a scriber, cleaned them and used a smear of Araldite to reinforce the joint.

As seen, the radius , and also the flat tapered sides were done on the little Geo. H. Thomas design rotary table , which I made many years ago, and which has been useful many times. The two stops can be set to stop dig ins at the end of the cut, and for small radii in particular, pulling the table round using bars is a lot more convenient than winding a handle many times on a bigger conventional rotary table. Dave

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