Britannia 70047 "Derek Stokes"

[ettingtonliam]

I think you've done well. I never had any joy using sand as a filler, I had better results using Woods Metal (I think) a low temperature alloy made for this sort of thing, but it does make the pipe stiffer and harder to bend. I think I've seen small size pipe bending springs, but can't remeber which supplier it was now. Polly Models? I don't enjoy pipe manipulation like this. Plumbers bend copper pipe without annealing, but there is a tendency for the finished article to have a series of ripples on the inside face of the bend.

[stevep]

Nobby,

I think the main point about commercial bending machines is that the formers are machined to fit the tube. Normally, the inside of the bend has a former, of the correct radius, and with a groove that fits the pipe. The outside former is normally straight, again with a groove to fit the tube, and the bearing in the bending arm bears on the former, not on the pipe.

I also agree with ettingonliam, that Wood's metal is very good. It melts below 100 degrees C, so after bending, you just stick the pipe in a saucepan of boiling water (don't tell the wife) and it all melts and runs out.

[JonL]

Ok thank you, I'll try woods metal in the future. LBSC recommended filling the pipe with lead... I didn't want to do that...

Thank you Liam, that makes me feel better. I'm also quite determined to up my game on this generally. I want to have something that I don't want to hide from other engineers...

[ettingtonliam]

Lead is also a method which I have used, but it has to be hotter than woods metal, and I'm never certain I've got it all out before I silver solder, so no, it isn't something I'd recommend.

[JonL]

I don't know if this is any use to anyone, but this link is to the 1960 report into an accident on the 21nd January 1960. Britannia 70052 Firth of Tay was hauling an express passenger train that was derailed at Settle, Yorkshire due to a defect on the locomotive. Five people were killed and nine were injured.

Obviously the report is quite sobering and came about for terrible reasons, but it does contain drawings of the britannia motion work right at the end which I think builders might find useful. 


This is a link to view it in your browser, but it might be easier to download it in its entirety.

[JonL]

I've been at all stop for a few days; had a rally on Saturday in which we won our class and came 8th overall, astonishing for a 1600cc car against turbocharged 4wd monsters. I can't claim any credit, I mainly just sit there, but a good result all the same. Sadly a couple of the landings didn't do me any favours and I ended up in hospital due to some internal injuries, I was only discharged yesterday and still have to go back for tests. My workshop only has space to stand and currently all I want to do is lay down and sleep, so please stand by.

[Deleted]

Hi Nobby

Well done on the win but also sorry to hear of your hospital visit. Hope all is well very soon...

Cheers

Pete

[JonL]

Thanks Pete. I think it may herald my retirement from Rallying anyway!

[timb]

Hey Nobby, we are missing you! Hope you are back upright soon, take your time pal and get well before you get up!

Tim

[barlowworks]

Hi Nobby, your body has a way of warning you when it's had enough and eventually you have to take note. At our club I do small paving jobs and my body now complains for a couple of days afterwards even though I have only laid half a dozen flags. To think, when I did this for a living 45 years ago I used to lay 50 a day and think nothing about it.
Take time to get well and listen to your body.

Mike

[JonL]

Today was the first time I've been able to go back into the workshop, and it took quite a bit of motivation as I feel very tired all the time. However I managed to get the first third of my blast nozzle done. LBSC says you should thread the copper blast pipe and screw the nozzle directly to it but frankly that idea worried me so I modified the design to incorporate a bush soldered onto the pipe with a thread there. This seems to have done the trick, now I just need to make the blast nozzle to screw onto it. My silver soldering has come on leaps and bounds; I hated the idea of soldering small components before but now I really enjoy it. It was good to get out to the workshop, hopefully I'll get some momentum up now I'm back into it.

[richard2018]

Welcome back Nobby! I had missed your postings (though I'm only a bystander in this thread). I hope you are soon feeling back to normal and look forward to your future progress on your loco. Best wishes, Richard.

[JonL]

Thanks Richard, I'm touched that anyone reads my Newbie blunderings. I hope it entertains if nothing else. Thanks for your kind wishes.

[JonL]

A mixed post tonight. A case of "it was all going well until...". This is my interpretation of the blower. My intention was to make it out of hex to enable it to be removed more easily if required. Here I've already cut the thread that mates with the blast pipe, and I'm making the high pressure steam gallery that feeds the nozzles.









After this test fit I drilled the nozzle holes, only to find (As the experienced engineers here will have guessed) that the steam gallery is in fact full of silver solder. Tap it out, clean it up, try again (being much more frugal with the solder), same story. I've faffed with it all evening and think its headed for the bin with another attempt tomorrow, with some amendments to the design. Might use a technique to join them that doesn't involve soldering. 

[Roger]

I don't see anything fundamentally wrong with what you're doing, except with adding the Silver Solder. Why not cut a small piece of fine Silver Solder wire and rest it on the joint? If you cover the whole thing with flux and move the Silver Solder back into place if it moves, you'll know that you can't add too much. Don't be tempted to add any more if it's not enough, just clean it all up and repeat with more Solder where you need it. If the fit is close, you hardly need any Silver Solder to fill complete the joint.

If you do it that way, you'll find it melts at a much lower temperature and you will hardly get it Red hot before the job is done. You can use a piece of Stainless Steel wire sharpened to a point to encourage the Solder to bridge the gap in the joint if it doesn't want to play. If it still won't bridge, you can just clean it up and try again.

If you don't have any, Macclesfieled Models sell fine Silver Solder wire on eBay quite cheaply. That's what I use on most of the work I do.

[JonL]

Good advice Roger, I'll have another go soon. I may need to remake some of the parts, I may have overheated the brass.

[JonL]

I followed the advice received here and also on instagram and also revised the design a little into two more equally sized components. This time I made it an interference fit, pressed together with a gap for the solder to fillet, and made the chamber inside oversized to cope with any silver solder which might make its way inside. Far happier today, was beginning to think I'd lost what tiny ability I had. Tested on the airline and it works like a charm. Properly cheered me up.

[JonL]

Forgot to mention Roger, I followed your advice of letting it cool and just adding extra where required and it really did work nicely.

[Roger]

That's a very neatly made part, very well done indeed. The difference between struggling and making look easy can be suprisingly small. Subtle changes in design, fit and technique make all the difference.

[JonL]

Thank you Roger, that means a lot.