Completing a 3 1/2" Jubilee

[smallbrother]

Nov 14, 2021 16:15:08 GMT GWR 101 said:

Decided that it might be preferable to make the eccentric straps before the eccentrics. So the next job is to machine the two castings that came as part of the set purchased off the web. Obviously I need to undertake some "fettling" before starting on any serious machining.




Regards Paul

Look forward to seeing how you do this.

Pete.

[GWR 101]

Hi Pete, hope you are well. I will do my best to take a few photo's. However my approach will not be the only way, it is just the one that utilises the machines I have access to. Regards Paul

[GWR 101]

I didn't manage any workshop time yesterday, teacher training day at youngest's school so was tasked with  entertaining grandson. We played pool at the local bowling alley, would have preferred snooker but he's not quite tall enough yet.

I managed to get a pass to the workshop today, and made some good progress.  Completed first three operations and preparing to drill and tap the holes for the 2 BA. bolts prior to splitting.

Facing both sides in the lathe, holding in small four jaw chuck.


 


Milling flat areas.




Ready to mark out for drilling, prior to splitting.



Hopefully tomorrow I will complete these and then start on the eccentrics. Regards Paul

[smallbrother]

The grandchildren I get asked to look after are 4 and 6. Can't wait for them to get big enough to play pool or something. I'm hopeless at entertaining small ones. Not being able to get on my hands and knees doesn't help!

Look forward to see how you split them and deal with the inside radius.

Hard to beat a bit of free knowledge!

Pete.

[coniston]

Great progress but if I may make a suggestion? It might be better to make the eccentrics before boring the straps. Reason being that assuming the eccentrics will have lands both sides of the running surface it is not easy to make the running surface diameter very accurately to size particularly if using a parting blade. Usual method would be after making the eccentrics to measure them accurately, turn a plug gauge then bore the straps to fit the plug gauge. That way if eccentrics turn out slightly different in size it' not difficult to make the plug gauges to suit. Of course if the eccentrics are made with only one land the use the eccentric to size the bore, you could then add a second land using a piece of sheet material screwed on. Other than using a parting type tool to machine the eccentrics you'd have to use both a LH and RH knife tool with similar problems of accuracy.

As I say just my thoughts on how I would tackle the job.

Chris

[GWR 101]

Pete, he's nearly 11 so as it was only his school that was off every where was reasonably empty. I also have a problem working at ground level but as stated he's past that now. Regards Paul

[GWR 101]

Chris, many thanks for your suggestion which is much appreciated. As the castings for this are supplied with an oval bore, I will split them after drilling the 4 BA fixing holes. This means that there will be sufficient material to machine the two joining faces. I will then fit them together and subsequently bore them to an accurate size. This is the method I used on Juliet and proved successful. I will probably make a bore gauge before the eccentrics (belt and bracers) approach. The eccentrics are from bar stock, so if I do encounter a problem then there is no shortage of material. As I stated earlier the are numerous ways of approaching this, so I do not advocate anyone using this method as the only way. Regards Paul

[ettingtonliam]

If you use a slitting saw in the mill to split the straps, there probably won't be any need for further machining of the joint surfaces. I agree with the method you are using, its the way I do them myself. Bore the straps next being an old fashioned type, I knock a piece of scrap wood into the hole, till its flush, mark out the centre, use the dividers to mark the bore, then centre punch round the circle. Set to run true in the 4 jaw and bore.
Then I use the strap, in 2 parts again, as a gauge when machining the eccentric itself. When the 2 parts fit the groove, and meet in the middle, thats it!

The really tricky eccentric/strap design was that beloved of Stuart Turner, with the groove in the strap.

[GWR 101]

Hi Liam, many thanks unfortunately I don't own a slitting saw fine enough for this job so I will depend upon a fine hacksaw blade, but I do acknowledge that the method you propose is probably the correct production engineering method. I am helped in my method (saw and mill) by the fact that the cast bore is oval by about 0.125" so even after sawing there is material to machine off. I will try and get some workshop time today and move the build forward, being an old guy myself I also utilize the piece of wood in the bore method. The general sequence I have adopted possibly derives from my early days of machining bearing brasses in two halves, these of course were soldered together for the final boring. Regards Paul

[GWR 101]

A bit more progress, drilled, tapped, split and milled the abutting faces. The keen eyed will notice I have deviated from the drawing as I have tapped one half instead of using two nuts, also because of metal restraints I have dropped a size to 5 BA. Hopefully tomorrow I will mark out and machine the bores, then the slots and drill the rivet holes, then a final tidy up. Regards Paul.

[smallbrother]

Splendid progress Paul and great clarity in the photos and description.

Pete.

[GWR 101]

After machining the bolting faces the rough bore was plugged, marked out and centre drilled. set up in the lathe four jaw and bored to size,


  






After this "boring" job i decided to leave the eccentrics straps at this stage and move on to the eccentrics. There is a slot to be machined for the arm to be riveted in but as this is the same size as the slot in the coupling rods I will undertake these at the same time when the cutter is set up in the lathe.






I will machine these over the weekend, two are required but I will only use one for the pump so the second one will be fitted just in case it is needed in the future. Also not sure about the balance but with the second at 180 deg. I am sure it will help compensate. Regards Paul

[smallbrother]

Paul, how do you decide where the centre point will be?

[GWR 101]

Pete, in one axis it has to be on the split line in order for it be able to be fitted on to the eccentric. The other axis at right angles to this, I simply worked from the outside of the casting to ensure that when the bore is machined there is equal and sufficient material all round. This was also mentioned earlier with the aid of a piece of wood pressed into the cast bore and a pair of dividers to scribe a circle to check this out. I took this a stage further and centre drilled so that I could use a centre bar in the lathe to clock it up. Apologies in advance but I must stress that it has to be on the split line as any deviation in this axis would render fitting correctly to the eccentric impossible.

I hope this helps I have found over time that although this may appear a complex part if the operations are sequenced correctly then it can be performed fairly easily, you may have noticed earlier in one of the photo's a process sequence sheet. Some may consider this over kill but when undertaking multi operations the sequence can be vital and forward planning helps to simplify this. Sorry I have rambled on far too much, keep making swarf (from the right  places). Regards Paul

[GWR 101]

Straight forward bit of turning, I have made the strap thickness slightly larger than the drawing which means I could get the micrometre anvils into the groove and measure the diameter accurately. Just need to make another one, drill and ream the hole and tidy up.  Trial assembly of Pony and Bogie trucks next prior to painting. Regards Paul.

[GWR 101]

Not a lot to show for 1 1/2 hours work !. Still it's another job ticked off, it's the pivot pin for the pony truck swivel. Regards Paul

[GWR 101]

A question if I may, prompted by Pete's reference to buffers. The construction drawing for this loco shows that they are oval, the heads are shown riveted to the cylindrical part. Is the riveting standard in full size or just a convenience for us to manufacture them. Regards Paul

[mbrown]

The LMS rivetted oval faces onto circular buffer heads. Not sure if that applied in every case but I haven't noted any exceptions.

The instances I can think of are: All the Pacifics, the 2-6-4T tanks and the little 0-6-0T dock tanks ("Twin Sisters").

Malcolm

[GWR 101]

Malcolm many thanks, I wasn't sure if it was a full size approach. I was toying with the idea of making them in one piece however if riveting is standard then I will probably go down that route. I have the castings for making them with riveted fronts so it would be more straight forward. Regards Paul

[GWR 101]

I decided that I needed a sanity check to make sure that the various chassis parts would fit together. I also needed to check where I should drill the holes for the Pony truck centring spring gear, as far as I can see they are not shown on the frame drawing.




Regards Paul