Building a Caledonian Pug in S Scale

JimG

Western Thunderer
I'm curious though - did the Caledonean use non-standard nuts?
From what I've found out about Whitworth nuts, they were based on standard hexagon bar sizes.
The original A/F size for 1"W was 1.67" - 26 thou or 0.66mm in 1/64 scale.
Under the British standard, the A/F size for 1"W was reduced to 1.48" - 23 thou or 0.59mm in 1/64 scale. (every thread under the BS used the A/F size from the next smaller thread in the old standard).

Andy,

I have to confess that I measured the AF of the nuts from the drawing so got a bit of an error. :) I did think about looking up the Whitworth standard, but didn't, so didn't get the correct AF measurement. When did the British Standard change? I have a memory that it was around war time (First or Second?) to save on materials. The loco was designed and built in 1911/12 so probably the original AF would be correct for a new loco. I'm not sure if the nuts would have changed over the years - the locos were quite long lived and lasted nearly to the end of steam in Scotland. I'll change the drawing to get them correct. :)

Regarding the central ridging - I guess you could just put it back in the lathe and polish them out.

I've now altered the GCode to half the vertical increment to see if that improved matters. But you can't see any of this detail by the naked eye, or even with Optivisors. An eyepiece begins to hint that detail is there, but I only see it if I take a very high resolution picture and blow up the cover details to about 10x. :) Maybe a bit over the top, but it is easier for me to make than drilling holes and inserting bits of wire, or whatever. :)

Jim.
 

AndyB

Western Thunderer
When did the British Standard change? I have a memory that it was around war time (First or Second?) to save on materials.

Jim,

The 'Foreward' from BS916: 1953 states:

B.S.916 was first issued in 1940, as a war emergency standard at the request of the Ministry of Supply, to supersede B.S. 28, ' Black bolts and nuts '.The specification was reviewed in 1946 and confirmed for re-issue as the reguiar British Standard for black hexagon and square bolts and nuts.

I'm assuming that the tolerances in BS916 were carried over from BS28 (which I don't have) - so the A/F tolerance for a 1" W thread would have been 1.67"/1.64", and the nut height was 1.06"/1.00".

When you make the matching wrench, it will need a scale jaw size of 1.69"/1.68", and to keep the ultimate rivet counter quiet, you'll also need to put a 30 degree chamfer around the top edges of the nuts!!:D ....... runs and hides behind wall with Heather .....

Andy
 

3 LINK

Western Thunderer


you'll also need to put a 30 degree chamfer around the top edges of the nuts!!:D ....... runs and hides behind wall with Heather .....

Andy

I have always wondered as to why there is that chamfer on the top edge, maybe it is to go easy on the knuckles when the spanner slips :rolleyes:.

Martyn.
 

AJC

Western Thunderer
Chapeau. I thought the wheels were rather good and then I saw the cylinder covers... I've just scraped my jaw off the desk; that does rather knock some of the various things I've seen attempted with rapid prototyping into the long, long grass. It makes my plastic bashing in 4mm look rather more impressionistic that perhaps it is. Thank you for sharing the process and the tribulations. The rest of the loco should be very impressive indeed.

Adam
 

Steph Dale

Western Thunderer
I hate to be the one to draw out the obvious double entendre, but I really do admire your nuts, Jim.

Martyn,
Actually the chamfer is there to stop dirt/grit jamming the nut when it's turned - if you look at the top of the nut you'll see the resulting load-bearing surface is a circle, rather than a hexagon.

Andy,
Thanks for the pointers on the BSW thread/nut sizes, I can see a need to re-asses a couple of the drawings/calculations and part lists to get the correct larger nuts on my older models. Thankfully I haven't reached a point of no return just yet.

Steph
 

AndyB

Western Thunderer
I have a scruffy Excel sheet of Whitworth sizes from 3/16" to 2" (and some larger). If anyone would like a copy please pm me with your email address.
I don't want to hi-jack Jim's excellent thread, but whilst we're discussing nuts - here is a less hi-tech way of producing them in a larger scale (Gauge 3, but also possible for G1 [1/32 or 10mm!!]).
These are scale 5/8" Whitworth, etched in 6 thou and folded. 0.9mm A/F.
As applied to improve a well-known Derbyshire manufacturers first G3 kit. The door plate was pantograph cut for me from my pattern.
The nut fret includes 5/8" to 1" in 1/8" increments.

Andy
 

Attachments

  • door runner 2.JPG
    door runner 2.JPG
    67.5 KB · Views: 37
  • Nut fret2.JPG
    Nut fret2.JPG
    99.1 KB · Views: 36

JimG

Western Thunderer
Mark II - and not a very good picture. Bright, freshly milled brass and an Anglepoise lamp don't go well together - I need a more diffused light source. :)

PugCylinderCover09.jpg

The nuts are now the correct size and I've halved the vertical increment on the code cutting the central domed section and that has smoothed things out quite well. I'll wait until tomorrow when maybe I can take a better picture outside in daylight. I might also give it a whiff of grey primer to make it a bit easier to get a good picture.

Jim.
 

JimG

Western Thunderer
Things have moved on a bit in the last week. The next job was to consider how I was going to build the main body of the cylinder. At first I had thought of making it out of a bit of solid brass or nickel silver, but I then thought that that might give me a lot of problems if I wanted to add detail to the cylinder. I then started thinking about splitting the cylinder bodies into kits of bits, with a base that would attach to the frames, and a front face and a rear face which would be soldered to the base. The cylinder covers would be soldered to the front faces and a thin sheet wrapper would be soldered round the edges of the faces.

I had one or two false starts - one being the front face complete with the fixing flange and webs.

498Wheel59.jpg

However, I would liked to have got the nuts and studding showing as well - i.e. if I could get the nuts on the front covers, why couldn't I get the nuts on the body flanges. :)

So I designed the cylinder base to incorporate the nuts/bolts and the casting webs with slots for the front and back faces.

498Wheel57.jpg

The nuts are to 1 1/4 Whitworth size - as prototype. :) The three holes are for fixing the cylinders to the frames. The centre ones will be tapped 12BA for hex head bolts through from the inside of the frames and the outer holes will hold pegs which will locate in mating holes in the frames to keep them aligned correctly.

498Wheel56.jpg

All the parts so far, with the two bases, the two front faces and two new cylinder covers.

498Wheel58.jpg

..and the lot cobbled up on a small piece of wood to give a rough idea of the assembly.

All didn't go well in the process. Wednesday was a bad day for my pocket......

498Wheel60.jpg

....three broken 1mm cutters and two broken 0.5mm cutters. :( I hadn't broken a cutter for a very long time so it came as a bit of a shock. Two were down to me in not allowing for the cutters digging through waste material too deeply, but the other three just went "ping" when cutting at feeds and speeds which I had been using successfully for quite some time. I could only put it down to the brass being a bit tougher to cut - it was the first time use of a 2.5mm sheet I got many years ago and I now can't remember what grade it was supposed to be. So speeds and feeds were made a bit more conservative and things have gone well since then. Carbides cutter are extremely good and hold their sharpness for much longer than HSS ones, but they are so brittle that one false move and they've gone. :)

Jim.
 

ScottW

Western Thunderer
I am gobsmacked, that is absolutely superb. The level of detail is fantastic, I would be impressed if you were building this in 7mm but to think this is S-Scale blows me away even more. :bowdown::bowdown::bowdown:

Scott
 

JimG

Western Thunderer
I am gobsmacked, that is absolutely superb. The level of detail is fantastic, I would be impressed if you were building this in 7mm but to think this is S-Scale blows me away even more. :bowdown::bowdown::bowdown:

I think I might be making a rod for my own back. :):):)

Jim.
 

JimG

Western Thunderer
More work has been done over the weekend - the rear face of the cylinder.

The rear face of the cylinder had quite large recesses where the interior of the cylinder matched the conical shape of the Drummond style pistons, and the exterior followed suit - presumably to avoid a large mass of metal which might have given problems when casting.

498Cylinder04.jpg

The rear faces were cut out by my (now) normal way of cutting them in a sheet to make holding a lot easier. You can see an earlier attempt centre left which I stopped when I thought that the cut depth was a bit deep and I didn't want to break the cutter. :) The finished parts - centre right - are held in place by two 0.2mm deep tabs each, similar to the way etched parts are held. It looks as though there is solid metal all the way round the curved parts, but it is mostly paper thin.

I decided to make glands as in the prototype so a couple of blanks were turned up and I used the collet chuck from the Cowells held in the millign table vice to hold the parts.

498Cylinder01.jpg

One part is held in the collet with the protective Plastikard waher, and the second blank is perched beside it.

498Cylinder02.jpg

Milling in process - cutting round the exterior of the gland.

498Cylinder03.jpg

And the finished piece - 7/8" Whitworth for nut fans. :)

498Cylinder05.jpg

The two rear faces removed from the brass sheet along with the glands.

498Cylinder06.jpg

And the gland assembled in the rear face with a pin stuck through to simulate the piston rod. Seeing this at about 10x size shows a a wee bit of cleaning up is still needed. :)

I'll now take a break on the pug and scattergun my way back to the 7mm shed I built last year. It was originally intended that the shed be removable, but the open sided structure wasn't really strong enough and it was difficult to locate the two cranes as well. So it's going to be nailed down and it's got to be ready for an exhibition in October/November time, so I'd better get it done soon. :)

Jim.
 

JimG

Western Thunderer
Back to work on the pug and the next job is the coupling rods which will need to be around once I start making the chassis. This was going to be another experimental job since I wanted to make them of steel and I hadn't cut steel before, and I wanted to try and avoid cutter breakage again. I had to spend two or three days using CAD to draw up the coupling rods. I didn't have any dimensions or drawings so I used a good broadside picture imported into Draftsight to work out the side elevations and had to do a bit of deducing to work out the thicknesses of the bosses.

I opted to try using 1/16" steel strip which I had lying about in the workshop - in fact lying about for well over forty years, got many years ago in a Ken Whiston bargain pack. :) A problem that can happen when milling strip is that the resulting piece can warp because of stresses being released by the cutting process, so I was going to be on the look-out for that.

The chassis will be fully CSB sprung so the rods will have to be jointed and I chose to reproduce the actual jointing, the only difference being to make the joint a half joint rather than a forked joint which was what the prototype probably had.

498CouplingRods-01.jpg

The rear pair of roads were cut with not much problem, with a 2mm cutter doing the surfacing and a 1mm cutter doing the profiling. I also used the 1mm cutter to bore guide bearing holes which will be opened out for bushing later on.

498CouplingRods-02.jpg

This was the setup and just starting to cut the front pair of rods. Lining up steel strip can be a bit of a fiddle since it is very rarely flat, hence the bits of paper to get it as close to flat as I could. I got it within .05mm along the length between the holding screws. The wood is used to give a sacrificial base to save the cutter when it breaks through.

Note the new, smaller ER11 collet head which makes things a bit easier when working around the clamping of small parts. Setting that up was a job in itself requiring drilling and tapping a rather hard Jacobs taper arbour which took almost a day with plenty of cursing. :)

498CouplingRods-03.jpg

The 1mm cutter cutting the profile of the second front rod. In between this shot and the shot above, I had gone through two 1mm cutters. The first one had done a fair bit of work - a lot of the previous cylinder work and both rear coupling rods, so it was probably getting blunt and carbide tends to break rather than bend when the stresses increase. The second cutter was brand new and lasted for about a couple of minutes, deciding to go ping at the first interrupted cut it came to. So I dropped the cutter feed and the third cutter worked fine.

498CouplingRods-04.jpg

When all the rods were cut, I flipped the strip over and started the machining of the half joint recess on the rear rods - the recesses on the front rods had already been cut when machining the front of the rods. The cutter lasted about a minute after this picture was taken. :) The tabs you can see which were holding the parts in place turned out not to be strong enough to hold things securely when this cutting was being done and the part moved and broke the cutter. Fortunately it had almost finished the cut so I was able to finish of the recess by hand with a needle file.

I cut the second recess with a different setup and a larger cutter and that worked well and will be the way I do this operation in the future.

498CouplingRods-05.jpg

The two sets of rods apart...

498CouplingRods-06.jpg

...and the rods (sort of) in position. I've still got a bit of finishing work to do and I need to get some emery paper to do it. The leading and trailing bosses on the bosses were flush with the rods on the prototype.

I know that milled coupling rods have been around for quite a while so I'm not exactly breaking new ground, but I suspect they haven't been around in the smaller scales since keeping small cutter breakage down means that cutter feeds have to be quite slow and cutting a set of rods would take a long time, so probably wouldn't be a commercial prospect. It would cut a lot easier using nickel silver but I'm not sure how nickel silver would look.

I'm now off to get some more cutters online. :)

Jim.
 

Steve Cook

Flying Squad
Thats another great piece of work and photo sequence Jim, I remain absolutely fascinated by what you do with machine tools :)

Sorry to hear you've gone through another set of cutters, they do seem to be a little on the consumable side at the diameters you are using, I guess thats just the risk you take. Can't see any other way of generating the results you do though :thumbs:

Steve
 

JimG

Western Thunderer
Sorry to hear you've gone through another set of cutters, they do seem to be a little on the consumable side at the diameters you are using, I guess thats just the risk you take. Can't see any other way of generating the results you do though :thumbs:

Steve,

I remember you asking me about getting cutters some months ago and I told you to get HSS ones - now you see why. :) But the carbide cutters are so much sharper than HSS and keep their sharpness for longer - that's if you don't break them first. :) I really should be running them with a spindle speed about five times the top speed of my machine, so cutting harder metals like steel is very much a venture into what I can get away with. :)

The next job is to drill the bosses to fit the corks - Richard (Dikitriki) - says I should. I think he intends that all the locos on Heyside should be so fitted. :)

Jim.
 

Dog Star

Western Thunderer
The next job is to drill the bosses to fit the corks - Richard (Dikitriki) - says I should.
Just so.

If that fine Mr.DJP can provide us with 7mm wagon kits that have representations of split pins on brake shafts then surely corks for oil fillers is a definite necessity? BTW - do Caley corks have split cane for breathers?
 

JimG

Western Thunderer
BTW - do Caley corks have split cane for breathers?

My research hasn't got that far yet. :)

On the matter of corks, I was reading "Tales of the Glasgow and South Western" a short while ago and David Smith tells of a driver who, if taking over a locomotive from another crew, would go round the locomotive and change all the corks for his own, and keep the other corks in a tin to go back in the holes when he left the loco. :)
Jim.​
 
Top