Author Topic: Adams "O2" Calbourne in 5" gauge  (Read 4152 times)

Offline springcrocus

  • Full Member
  • ****
  • Posts: 117
    • Steve's Britannia
Re: Adams "O2" Calbourne in 5" gauge
« Reply #30 on: April 14, 2023, 03:07:27 PM »
Thanks to everyone for their various comments.  :cheers:

Mainspring brackets

Don Young never drew any part of the authentic main wheel springs for this loco, relying on a single coil spring below each axlebox. However, one model engineer, Nigel Bennett, drew out the various components to make the traditional leafspring components for his very nice model of "Ashey" and kindly sent me a set of his drawings so that I could make the same for "Calbourne". I don't think Nigel is a member here but he contributes on both the MECH and ME forums (fora).

I started with the spring brackets, cutting eight pieces from some 25 x 10 black bar and milling all round to get blocks at the maximum dimensions. Then one side for reduced to 17mm for about 20mm length. These drawings are in metric so I decided to work in metric, complete with metric cutters, without converting anything to imperial, just to remind myself that I could!



One change I made is the frame bolting arrangement, opting for three M3 screws instead of five M2.5 screws. The three holes were drilled through 2.5mm diameter, then tapped M3 freehand in the bench vice. The DRO was zeroed on the fixed vice jaw and the middle hole.



Next, the root of the inside shape was cut, plunge-cutting with a 6mm diameter end mill.



Three more operations were done with the same setup to produce end-points for shaping the sides of the vertical component, working plus or minus either side of the centre-line.



The same cutter was then used to reduce the leg to 12.5mm. These are the eight brackets, starting to take shape.



To do the rest of the machining, I made a fixture with three bolt holes from a piece of 1" x 3/16" flat bar. I drilled the holes 3mm diameter for a good fit on M3 cap screws and fixed each bracket from below. After milling some soft jaws to take the fixture, I had to clock the tilt-and-turn vice in the "tilt" plane to compensate for jaw-lift.



Then the vice was set round to 23 degrees to form the foot of each bracket. The DRO was zeroed on the inside of the ankle and the 6mm cutter was worked round in conventional mode to form the shape.



Once all eight were done, they were remounted and the cutout for the spring support pin plunge-milled with an M5 cutter. That completed all the work in the T&T vice so that was taken off the mill table and replaced with my main vice. The fixture was clamped in the vice, set at 67 degrees, and the holes for the spring pins drilled 3mm diameter. These were then widened and elongated with a 3.5mm dia slot drill.



I modified the fixture plate for the last couple of operations; counterboring the screw holes, shortening the front end and cutting off the corners. This was to allow a 12mm endmill to cut the big radius on the back of the spring brackets. The fixture was clamped to the rotary table after carefully working out where to position it. The spring brackets were then screwed in turn to the underside of the fixture. The extra fences are to prevent the fixture rotating about the single clamping screw.



For the final operation, they were mounted to the fixture one more time and the section where they bolt to the frames milled away.



That completes all the machining on these and, once they've had a bit of a clean-up and an hour in the phosphoric acid, they will be ready to fit to the loco.


Regards, Steve
Member of a local model engineers society
www.stevesbritannia.co.uk

Offline crueby

  • Full Member
  • *****
  • Posts: 18554
  • Rochester NY
Re: Adams "O2" Calbourne in 5" gauge
« Reply #31 on: April 14, 2023, 03:49:29 PM »
Nice job on some complex shapes.   :popcorn: :popcorn:

Offline Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7860
  • Portland, Oregon, USA
Re: Adams "O2" Calbourne in 5" gauge
« Reply #32 on: April 14, 2023, 05:42:51 PM »
Thanks for the great walkthrough of your operations.  Good use of that jig, too!  :ThumbsUp: :popcorn:

Looking forward to seeing these springs come together.
Kim

Offline Prowler901

  • Full Member
  • ****
  • Posts: 71
Re: Adams "O2" Calbourne in 5" gauge
« Reply #33 on: April 21, 2023, 09:51:06 PM »
Those are some complex operations.  Nice job!

Todd

Offline springcrocus

  • Full Member
  • ****
  • Posts: 117
    • Steve's Britannia
Re: Adams "O2" Calbourne in 5" gauge
« Reply #34 on: May 04, 2023, 06:50:24 PM »
Chris, Kim, Todd, many thanks.

Chimney

There is a casting available for this loco but I decided to make mine from various offcuts of brass and bronze. The first of these was the base section which came from a large bronze gear wheel. After facing off, the billet was bored through at 1.1/8" diameter and then opened out to 1.1/4" diameter by 3/4" deep to take the peticoat pipe. The first picture shows it resting on the soft jaws that I machined to hold the work for the second operation.



The o/d was turned to the maximum size of the chimney saddle, then the 13/16" radius flare was formed using a technique  from the very earliest days of turning. A round-nosed brazed carbide-tip turning tool was chosen and a 3/16" diameter hole drilled and reamed through the shank 13/16" from the tip. The toolpost was removed from the lathe and a worktable bolted to the compound slide in it's place, which had a 3/16" diameter silver-steel pivot-pin fitted at the top left corner. The turning tool was fitted onto the pin and a length of steel box-section slid over the back end of the tool. The picture isn't very good but shows most of the relevant detail.



This next picture shows the radius about half-formed and a better view of the tool with it's extension handle. There was no real measurements here, just easing the cut along or down twenty thou at a time and keeping pressure on the handle so that it didn't dig in to the work.



Loads more cuts were made until I reached a point 1/16" thick at the base and 1.13/32" diameter at the chimney neck. Then a spigot was turned to locate the chimney onto. Bear in mind that this radius is only relevant to the widest part of the saddle and further work will be required once the underside of the saddle is machined to fit the smokebox.



Next, the chimney neck was made from a length of 1.1/2" diameter brass bar, drilling and boring through to finish at 1.1/8" diameter. A spigot to match the saddle was machined on the end and the outside cleaned up with emery cloth.



The two parts were silver-soldered together next, a ring of 0.5mm diameter solder resting on the slight lip between the two components. Although this should have been relatively easy to solder, the great mass of the saddle made it much more difficult than expected, with a lot of heat directed into the hole at the top and rather less to the chimney neck to get both parts up to temperature.



The next stage was to bore the 2.5o taper in the bore and the 1.25o taper to the outside, both jobs done with the compound slide set to the relevant angle and with the assembly mounted on the same soft jaws. Finally, a turned section was formed at the top to take the chimney cap. Sorry, no picture of that.

I didn't have a piece of brass big enough to make the cap as a single piece, so used two pieces instead. This is the first piece silver-soldered to the top of the chimney.



The second piece was made and this was soldered on as well, but using a lower melting-point solder. Then the assembly was remounted onto the soft jaws, the o/d of the cap skimmed to size and the upper radius turned with a form tool.



The same form tool was used to create the underside form but, because it was a larger radius, I nibbled away at it freehand (winding both the carriage handle and the cross-slide handle at the same time) using a radius gauge as a reference.



This is the chimney with all the turning finished although I will use a bit of filler to disguise the lower join. It just leaves the machining of the saddle to complete.



Regards, Steve
Member of a local model engineers society
www.stevesbritannia.co.uk

Online uuu

  • Full Member
  • ****
  • Posts: 100
Re: Adams "O2" Calbourne in 5" gauge
« Reply #35 on: May 04, 2023, 07:20:33 PM »
I do like those soft jaws.  They look a lot more secure than the spigot I used for my chimney.

And I have the advantage over other readers, having seen yours yesterday.  It's rather special.

Wilf

Offline Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7860
  • Portland, Oregon, USA
Re: Adams "O2" Calbourne in 5" gauge
« Reply #36 on: May 04, 2023, 07:24:58 PM »
That's a beautiful chimney, Steve! Well done!  :popcorn: :popcorn:

I do like how you pieced it together from several parts.

Kim

Offline Admiral_dk

  • Full Member
  • *****
  • Posts: 3752
  • Søften - Denmark
Re: Adams "O2" Calbourne in 5" gauge
« Reply #37 on: May 04, 2023, 10:26:57 PM »
Beautiful curved Chimney  :praise2:

Nice buildup + good to save / reuse stuff  :ThumbsUp:

Per

Offline Zephyrin

  • Full Member
  • ****
  • Posts: 766
  • near Paris, France
Re: Adams "O2" Calbourne in 5" gauge
« Reply #38 on: May 05, 2023, 09:39:26 AM »
turning such large curves on brass or bronze is a great pleasure !
at this point, the metal being already annealed after brazing, it seems that you will make the base part of the chimney by forming it into a saddle on a mandrel as I don't see any metal left for machining ?

Offline springcrocus

  • Full Member
  • ****
  • Posts: 117
    • Steve's Britannia
Re: Adams "O2" Calbourne in 5" gauge
« Reply #39 on: May 05, 2023, 09:45:12 PM »
Wilf, Kim, Per - kind words, thank you.

 Zephyrin, the base will be machined to fit the saddle and you'd think that this would remove too much material. You are, of course, correct (because of the compound curves involved) and the front-to-back dimension will come out undersize. However, I have a trick up my sleeve....  ;)

 Regards, steve


Member of a local model engineers society
www.stevesbritannia.co.uk

Offline springcrocus

  • Full Member
  • ****
  • Posts: 117
    • Steve's Britannia
Re: Adams "O2" Calbourne in 5" gauge
« Reply #40 on: May 16, 2023, 01:20:10 PM »
Chimney continued

To machine the underside of the saddle, I modified one of my flycutters to take a tool that I can adjust to 5.1/4" diameter. I have milled a shallow 5/16"-wide slot, with one edge on the centreline, and made a couple of clamps and an adjuster to hold a piece of 5/16" square tool steel. The tool has to be ground as left-hand-cutting, of course.



This was an opportunity to try out my new cross-slide and I created the setup while the slide was still on the bench, using packing to set the centre-height.



Then I swapped the cross-slides over - a matter of two minutes work - and set the flycutter to 2.5/8" radius. Although it doesn't show, I'm holding the flycutter in a collet block and this block in the chuck otherwise I wouldn't be able to get the length of cut required.



As noted in the last post, the compound curves on the upper surface cannot be machined conventionally and this arrangement leaves the front-to-back dimension too short, as can be seen.



So the answer is to fix another piece to the bottom and build it up. First I cut a square from 20swg brass sheet, bored a 1.1/4" hole in it, put a bend in it and then clamped it to the bottom using the petticoat fitting to get it tight.



Then it was rounded off freehand until it sat nicely on the smokebox. It's not a perfect circle because it would foul the rivets.



Once happy with that, I drilled a couple of holes in the baseplate for 8BA fixing screws, spotted them through to the chimney, then set up the angle table to drill and tap the matching holes.



A pair of countersunk brass screws were used to fix the two together, the Hoffman roller being used to keep things in line whilst tightening.



Finally, a load of high-temperature gunk was smeared all round the base and left for two days to cure. Then it was shaped with emery cloth and some light filing to create the finished curves. It is actually a lot smoother than it looks because of how the light reflects but this chimney is going to be painted, anyway, so the primer will hide any tiny blemishes prior to painting. The filler is supposed to withstand over 500o centigrade, so should be suitable for this.



Regards, Steve
« Last Edit: June 07, 2023, 10:02:39 PM by springcrocus »
Member of a local model engineers society
www.stevesbritannia.co.uk

Offline Kim

  • Global Moderator
  • Full Member
  • *****
  • Posts: 7860
  • Portland, Oregon, USA
Re: Adams "O2" Calbourne in 5" gauge
« Reply #41 on: May 16, 2023, 05:16:03 PM »
Very nice fabrication work on the chimney, Steve!  It looks great! :ThumbsUp: :popcorn:

That JB weld is great stuff, isn't it? :)

Kim

Offline RReid

  • Full Member
  • ****
  • Posts: 1668
  • Northern California
Re: Adams "O2" Calbourne in 5" gauge
« Reply #42 on: May 16, 2023, 08:18:22 PM »
What a cunning solution to the problem! Gunks do have their place. :ThumbsUp: :ThumbsUp:
Regards,
Ron

 

SimplePortal 2.3.5 © 2008-2012, SimplePortal