Paddington Platework

[davidk]

Oct 29, 2020 13:22:45 GMT jordanleeds said:

Without wishing to hyjack the thread too much is there an alternative source of Paddington cylinder castings given that I think Reeves are no longer doing them and if they are charge a Kings ransom

You could try 17D; not for castings, but for machined items from cast iron bar stock, if that's an acceptable way forward.  They do ready-machined cylinders for 7 1/4" gauge BR Standards.  I discussed Paddington cylinders with them some time ago and they could probably help.

Usual disclaimer

David

[Gary L]

Oct 29, 2020 14:28:09 GMT davidk said:

Oct 29, 2020 13:22:45 GMT jordanleeds said:

Without wishing to hyjack the thread too much is there an alternative source of Paddington cylinder castings given that I think Reeves are no longer doing them and if they are charge a Kings ransom

You could try 17D; not for castings, but for machined items from cast iron bar stock, if that's an acceptable way forward.  They do ready-machined cylinders for 7 1/4" gauge BR Standards.  I discussed Paddington cylinders with them some time ago and they could probably help.

Usual disclaimer

David

As far as I am aware there are no castings available any more. My understanding is that this is not so much a disinclination to supply castings, but due to difficulties in getting these particular castings in consistent quality. This is not an issue with machining from solid, but it needs a big machine to do it. The castings were notoriously expensive anyway, so getting them machined from solid elsewhere might prove the best way in any case.

However this is going off-topic, so might I suggest starting a fresh thread? You are more likely to get a broader set of replies that way.

HTH

Gary

[Gary L]

Oct 29, 2020 5:38:01 GMT steamer5 said:

Hi Gary,
The hydraulic bit is a wire crimper...16 ton....so a bit over the top for 3/64” rivets! They come in different sizes I think at the time there was 4, 8, & 16 ton ones.
The C shaped bits are to my design & the fitting on the end of the hydraulic unit that they attach too. I had them watercut.
I think it was a story on the Model Engineer site by a gent that was doing a rebuild of a motor bike & needed to close 3/16” steel rivets that was the start of the project. The gent that I got some of the plans for the Garratt from had spec’d 3/16” rivets for the stretchers, I’ve since found that they should only be 5/32”, with only a few 3/16 ones for the spring hangers.
I have had a play with it on the 3/16” ones & the power available opened the C frames! So will have to figure out how to sort that & still be able to get it were it’s needed.

Cheers Kerrin

Gulp! 16 tons eh! Might be overkill for 3/64"

Impressive apparatus though, well done Kerrin!

Gary

[Gary L]

Oct 29, 2020 8:14:06 GMT Roger said:

Hi Gary,
The biggest issue with using plate like I did for a rivet press is the tendency for it to twist as you apply the load. The spreading force trying to open out the 'G' shape isn't a problem. I had to add chunky side pieces to mine, and even then it would have been better if it was stiffer.
I'd make it out of 12mm plate or thicker, you could get it laser cut. The anvil ends can be chamfered at a shallow angle over say 50mm length to make them small enough to reach into the awkward places. I opted for 3mm diameter anvils and the end is only 5mm thick, so it's quite slender at the business end. You'll have to look at what are the most difficult areas to reach when deciding that.

Adrian, Roger

I will go down the toolmaking route if I have to, but only if I can't find a suitable machine on the market. I don't plan to build another loco, so I don't mind shelling out for a tool which I can then sell on after the cab is finished. No doubt there will be compromises with an off-the-peg tool, and certainly places where I have to resort to hand setting, but from a quick survey of the cab plates, I reckon that a 4" reach will get to 90-95% of the rivets, and I can't see any potentially awkward locations that can't be overcome with a bit of pre-planning. One of the benefits of 7¼" gauge perhaps, where there are not so many small crevices to get into!

4" rivet squeezers are available (though not cheaply) but if I can recoup a decent proportion of the outlay later, I reckon it will be a good investment in time saved.

Many thanks for the discussion, which has helped me decide what features/size to look for

Gary

[Gary L]

The second corner piece is now done, without any need for patching this time. They were trimmed to size after marking out carefully with a surface gauge and surface plate (actually a granite floor tile. These are polished to a good standard of flatness, they are robust and above all cheap!) All that remained was to drill the rivet holes all round 3 of the 4 sides. These need to mirror the accurate holes on each adjoining plate which were made by the laser cutter, which is easier said than done.

It isn't practical to do this first on plates like these corners that need to be heavily worked. For these, it is better to make the bends and mark out from them IYSWIM, rather than trying to get the bend in a predetermined exact place on a pre-cut plate. I have broken this rule on the bunker, and will do it again on the roof, but these only have curves in one dimension, not two. Anyway, it means that it would have been impossible to pre-mark the rivet holes; they can only be done on the finished plate. Workholding difficulties mean that I couldn't work direct from the adjoining plates, only from the butt straps that have been drilled through from the adjoining plates, introducing an extra level of degraded accuracy. Even separated from their neighbours, these corners were difficult to hold for drilling.

I never find that traditional scribe-and-centre-pop methods work well for me, I would much rather use the DRO on the mill. The straight flat edge at the front was easy enough, but the rivets on the curved face had to be set up one by one, which was long-winded and tedious...



... First set the workpiece so that the drill will enter it perpendicular, then use the X & Y handwheels to position the datum hole in the butt-strap precisely under the drill bit, as above. This can be quite accurate; look for the deflection of the drill as it enters the hole, which tells you it is not quite right. (The drill has to be turning, to eliminate any slight bend in it). Zero the DRO, then advance the Y handwheel to exactly the offset required- in this case 0.1875". Then...



... Use the spotter to start the new hole, then replace it with the drill. The drill is only 1.3mm, and without the pre-spotted hole it wanders all over the place. I said this was tedious!
Note the use of the cap screw and nut as a cheap and cheerful machine jack to prevent the workpiece from bending even under the modest pressure from this small drill. (I have a set of proper machine jacks, but whenever I've needed them, they have always been too tall )

Then, eventually, the finished item...



This is the second corner. If you look closely you can just see the silver-soldered seam in the apex of the 'corner.'
If this method is used for something where the brass will be polished, not painted, it is possible to get silver solder in a matching 'brass' colour, though I haven't tried it (yet). I will need to get some eventually for spinning the safety valve bonnet in two parts per C R Amsbury.

[Roger]

That's another cracking job, I'd be very happy with that indeed.

[Gary L]

Oct 31, 2020 9:03:34 GMT Roger said:

That's another cracking job, I'd be very happy with that indeed.

Coming from you, that must be the equivalent of a (Paul) Hollywood Handshake (No, I don't, but I know someone who does!)

I admit I was pleasantly surprised that they came out right the first time, without having to do it all again. But it is all down to techniques learned from your thread Roger, I wouldn't have a clue about formers and backing plates otherwise. Plus the enormous help with research. Without your photos and other info I would be limited to the Adams drawings, and they are not as informative as they might be, not to mention downright wrong quite often.

Gary

[Gary L]

The bunker rear is more-or less ready for riveting now, just awaiting delivery of a shiny new rivet squeezer; there are a few more things to add (steps, handrails and fire-iron hooks) but none of those can be done till all the rivets are set. Here’s a reminder from the 1501PTA website 1501pta.jimdofree.com what the real bunker looked like in 1949:

(You can see a much bigger version of this picture by clicking through to the website) 

My steps are laser-cut brass, just waiting to be folded, with little spigots on the back to go into into 4 location holes each. If I was clever I would have drawn the little spigots more than 1/16” long, so I could rivet or twist them from behind for a bit more security, but I didn’t, so they are location only. Plan A (more of an assumption than a plan, TBH, was that I would silver-solder them in place, but on reflection, if I could get sufficient local heat on each one, I’m will end up with distortion; not to mention b—ing up that lead filling I did on the score marks. Clearly I didn’t think this through! Will ordinary soft solder be adequate to hold them on?

The handrails I plan to secure with nuts, but the fire-iron hooks are another issue. I think they will have to be steel for extra strength, 3/16” x 1/16” in the Adams drawing. In full-size they are welded on, and Roger welded his too, but that option isn’t open with brass plates. I can only think of silver-soldering a pair of little studs on the back of each one (very fiddly) and nutting them on from behind too, but I’m open to suggestions. They are very vulnerable, so perhaps this is the way, to allow for easy repair/replacement?

[dscott]

Yes bits sticking out of a sheet that needs painting at some stage needs careful thought.
Yes nuts on the inside sounds a great idea, even if you have to re make the irons and make some spares while up and making.

Lovely to see what you look like, I have just noticed.

David and Lily.

[ettingtonliam]

Soft solder should be fine.

[Gary L]

Nov 2, 2020 2:54:32 GMT dscott said:

Yes bits sticking out of a sheet that needs painting at some stage needs careful thought.
Yes nuts on the inside sounds a great idea, even if you have to re make the irons and make some spares while up and making.

Lovely to see what you look like, I have just noticed.

David and Lily.

Ha ha, thanks Dave & Lily, no-one’s ever said that before!

It is certainly true that painting is a lot easier if the details can be bolted on when the main painting is finished. I’ll have to put on my elfin fingers for the job, and also track down that evil gnome that steals 12BA nuts whenever they drop on the floor...

Gary

[Gary L]

Nov 2, 2020 7:51:29 GMT ettingtonliam said:

Soft solder should be fine.

Glad you said that, ‘cos I don’t think I have any alternative! Once again, they are welded in full size. I know it is quite normal in smaller scales to attach details with soft solder, but in 7¼” everything is bigger and heavier and more sticky-outy (technical term) so I had a momentary wobble about it.

Gary

[barlowworks]

Always better to make a sound mechanical joint before soldering if possible. Solder on its own isn't that strong for sticky out bits. Also be aware that you can step solder with solders ranging from about 140 degrees up to about 240 degrees, that way you can solder up to something already soldered without it all melting into a kit of parts. The bunker is looking brilliant by the way.

Mike

[Gary L]

Nov 2, 2020 15:39:35 GMT barlowworks said:

Always better to make a sound mechanical joint before soldering if possible. Solder on its own isn't that strong for sticky out bits. Also be aware that you can step solder with solders ranging from about 140 degrees up to about 240 degrees, that way you can solder up to something already soldered without it all melting into a kit of parts. The bunker is looking brilliant by the way.

Mike

Thanks Mike

Yes, I know about temperature ranges for soft solder, but apart from Comsol it isn't something I've had to use much on this project so far. Or dared to use, because I'm nervous about its strength. That's not quite true; I've used it on a number of occasions to hold awkward-shaped components (like brake shoes) onto steel sections for machining purposes. I suppose the strength didn't cause a problem there, but there was plenty of contact area, which will be a bit lacking on the bunker steps.

The worst case is they get knocked off, in which case I could alter the drawings to lengthen the spigots and get some more laser-cut; it's just annoying that I didn't think of it earlier! Actually that's not the worst case; the worst case is they get knocked off after painting,.. hmmm...

Gary

[Gary L]

I've been through-drilling lots of 1/16" rivet holes for the angle which secures the cab sides to the footplate. This allows a dry-run assembly, which looks like this:



Obviously the angle will be cut away to clear the cab doorway, but not yet. The front spectacle plate is not in the picture, but it has been separately trimmed to make sure it clears the firebox cladding all round and will make a snug fit where it joins the cab sides. The black pen lines mark the holes that have yet to be drilled through.

The cab sides are higher than they need to be, to facilitate bending the tight curve where the cab sides join the roof. The bend required is 0.454" inside radius which is an awkward size; too big for the folder on the Formit, and too small for the rollers. (I expect there is a calculated reason for that rather odd dimension, but I can't remember what it is!)

I've read of a method that uses a round steel bar of the required radius inside a steel angle iron. This might have some potential, since the length of the bend is not so great as to provoke serious flexing in the bar or the angle.

Also, I think I might need to anneal the plate at that location to make it workable. By chance, the shape of the plate is such that annealing it there probably won't distort it irrevocably. 

I'll need to sleep on it!

[dscott]

A wonderful tip on drilling small holes into locomotive frames and plate-work from Keith Wilson where I spent my miss spent youth most weekends in School holidays!!!
Is to have a range of 18 inches long by 1/4 or 3/16 diameter rods with a drilled hole and a drill bit soldered in.
These work incredibly well and when polished you can hold the rotating end to steady.
Also useful for harder to reach holes at the bottom of bunkers when spotting through.

I have a long handled tap holder which has the same effect. It is also useful for boiler bits and bottoms of bunkers!!!

David and Lily.

[dscott]

Bending. For a quick V tool you can clamp a pair of 1 to 1 1/2 inch diameter round bars together and bring your smaller rod down into the middle. The small rod is best fixed onto a plate to preventing bending. A V can be milled into the plates end, and the rod double sided taped in place. The radius of the round bars giving you a lovely mark free finish as they rotate round, polish them prior to use. A thin plate can also be used to prevent marking on the outside.

Then you need a machine that only gets used every 6 months to do the 2 squeezes!!!

David and Lily.

Lily is still not sold upon the idea that the Flypress would be a useful addition to the Kitchen for can crushing!!!
SHAME.
Cherry Tree preventing any further expansions of the Workshop.

[chester]

David the fly press could also be used as a juice squeezer in the kitchen

[ettingtonliam]

Can also act as a finger squeezer, as I found out when I used one 'professionally' 50 years ago. Our power presses were nicely guarded, but the fly press (a big one standing over 6 feet high) wasn't!

[Gary L]

Nov 3, 2020 2:29:04 GMT dscott said:

Bending. For a quick V tool you can clamp a pair of 1 to 1 1/2 inch diameter round bars together and bring your smaller rod down into the middle. The small rod is best fixed onto a plate to preventing bending. A V can be milled into the plates end, and the rod double sided taped in place. The radius of the round bars giving you a lovely mark free finish as they rotate round, polish them prior to use. A thin plate can also be used to prevent marking on the outside.

Then you need a machine that only gets used every 6 months to do the 2 squeezes!!!

David and Lily.

Lily is still not sold upon the idea that the Flypress would be a useful addition to the Kitchen for can crushing!!!
SHAME.
Cherry Tree preventing any further expansions of the Workshop.

Great idea David, thanks for that!!

Gary