Britannia 70047 "Derek Stokes"

[JonL]

Mar 28, 2019 21:57:34 GMT Jim said:

Like your new avatar Nobby...far less alarming for old blokes like me.

Just lulling you into a false sense of security...

[simplyloco]

Mar 28, 2019 22:03:53 GMT JonL said:

Mar 28, 2019 21:57:34 GMT Jim said:

Like your new avatar Nobby...far less alarming for old blokes like me.

Just lulling you into a false sense of security...

Anything you can do...
Avatar changed again, just for fun!
John

[JonL]

Left hand guide bar bracket. Not attached to the guide bars yet as I wanted to see how they line up and spot them in place. Takes a long time on the vertical slide but I wasn't working to a timescale today. It all turns nicely with no tight spots, and the piston works well on air. This was the side with the sleeve if you cast your mind back.

[arch1947]

Nice work!

[JonL]

Nothing worth putting a photo up over this time as its all been done before, but I managed to get an hour to make a crosshead pin and nut. The nut has a chamfer on the base to prevent it scoring the gunmetal crosshead when tightened, and the pin has a lip it tightens down on to to prevent the crosshead getting crushed.

[JonL]

Mounted the guidebars on the LHS this evening. I'm not completely happy with the alignment. It's a bit off, and its causing some undue friction. More fettling needed.

[JonL]

Blast pipe flanges loosely fitted tonight, got to work out exactly how I will be making that next.


Also did another job I'd been putting off; drilling the holes for the drain cocks and cross drilling through to the cylinder bores. Went OK in the end, I just took my time with the setup and hoped for the best. I can't tap the holes yet as the tap set is in the post.

[JonL]

I feel some context is in order here... the next set of photos are the antithesis of what Roger, SimplyLoco and others achieve...

I've been trying to work out how to cut the correct radius for the smokebox saddle to allow the smokebox to sit neatly. It's been annoying me, as I couldn't see a way of mounting it on the vertical slide. I'd already figured I needed a fly cutter, but decided to use my Boring bar as a nicely rigid way of achieving the same goal.

Now remember I only have a Myford ML7... and the short cross slide version at that. I ended up having to use both my vertical slides mounted together to give me enough clearance. I used packing where I gripped the casting to reduce the chance of breakage or slipping. I can hear people fainting as we speak...



With very small cuts it was rigid enough for this part that luckily didn't require much in the way of precision, but the results were much better than I anticipated. I thought I would have to do a lot of the finishing by hand but that isn't the case.

I have to ask: how would the more experienced among you have done this? Although it worked it felt like a horrible bodge. I couldn't think of an alternative. There isn't anything really to grip on the saddle; I couldn't clamp through the centre as I needed to machine the whole saddle surface. Had I been able to clear the lathe saddle with the tool I could have just used one vertical slide.

[JonL]

Also I forgot to mention, I tapped the threads for the cylinder drain cocks and the thread on one of the holes just crumbled away, I thought I'd stripped the thread but it was more like pulling the tap out of a sandcastle.

I've been really unhappy with these cylinder castings. If I can ever afford to I will be replacing them. Everything I've attempted on them seems to have been a disaster.

[ettingtonliam]

I think I'd have tried mounting an angle plate on the cross slide, and bolting the saddle to that. I'm quite ruthless about drilling holes in workpieces to fasten them, if all else fails, then plugging the holes up afterwards, if its necessary. On a gunmetal casting I'm doing at the moment, I've soft soldered a lug on the outside to improve the fastening, then I'll melt it off afterwards.

Any way 'horrible bodge' or not, it worked and thats the important thing and you are entitled to be pleased about it.

[JonL]

Liam, that makes sense. It never occurred to me to drill mounting holes but it makes perfect sense, thank you.

With regards to that casting hole crumbling, I may see if I can solder a small bush into it, failing that some chemical metal. Again, I'm not proud of this sort of engineering. I feel like I'm constantly fighting against the tide with it at the moment.

Tomorrow is another day.

[Deleted]

Nice one Nobby....if it works that's good enough...looking good..

Pete

[Roger]

That's an ingenious solution, and one that does allow for the height to be adjusted. Ok, it's not the stiffest arrangement, but I wouldn't call it a 'bodge'. Adding holes in parts is a good idea if you can't attach it another way. I'd probably have used a big lump of Steel and bolted that where your vertical slide goes, then attached the saddle to the side of that. In the end, you only have to do it once, so whatever works is absolutely fine.

[JonL]

Thanks chaps. I think you are right, I was too keen to hold on to the idea of using the vertical slide and not thinking outside the box. We live and learn.

[JonL]

Spent most of the evening tidying the workshop, but mocked up the smokebox door crossbar tonight. Going to crack on with the smokebox.

[JonL]

I've been feeling a bit of a ten-thumbed oaf lately when it comes to my work on this locomotive, so an afternoon like this was just what I needed. The black paint isn't final, it was just to help me visualise the finished shape. The gloss of the paint hides the curved edge to the smokebox door which mirrors the prototype pretty well. I'm overjoyed with the result. I only remembered to take photos of the door work, but the smokebox ring was done at the same time.

[timb]

That looks excellent Nobby, how did you do the curve?

Tim

[JonL]

Thanks Tim, the curve was broadly present on the casting; I roughed it to shape by using the lathe feeds as usual and then got the final shape by profiling whilst spinning in the lathe using a sharp file. I'm not sure if thats an approved technique but it seems to have worked.

[JonL]

Smokebox dart. I machined a mushroom on the lathe and then used the vertical slide to shave the sides off of it.



Next I have to file the flats on it, cut the thread and work out how to broach the square hole for the handle.

[Cro]

One thing I would advise - don't rivet in the front ring to the smokebox, leave it as is so you can remove the whole thing in one. Grandad did this and it makes access in a small smokebox so much easier for maintenance and cleaning!

Adam