Adams "O2" - Calbourne

[springcrocus]

Introduction

Calbourne is the sole surviving member of the William Adams "O2" design of tank engine and is the flagship locomotive of the Isle of Wight Steam Railway.


Photo courtesy of Isle of Wight Steam Railway

Using the Don Young "Fishbourne" drawings as the main source of reference, I will attempt to build a 1/12 scale model based on how Calbourne appears at the present time. Living on the Isle of Wight, I have reasonably easy access to the locomotive for photos and measurements.

This model will use laser-cut mainframes, bogie frames and equaliser beams and also cast wheels but the rest will be machined or fabricated from scratch using basic materials.

I'm not sure how much interest this will generate but I was planning to record it as a start-to-finish build, warts and all, with an estimated build-time of three to five years. I'm a reasonably-competent machinist and this record will concentrate on the machining techniques that I use to construct the model. Therefore, there will be little of interest for the experienced modeller, it's really aimed at beginners who may lack the confidence to try to make parts for themselves. I shall start with the frames, build the boiler (hopefully with Wilf's help) and sub-contract the painting out to someone else. I don't have the skills to make an exhibition-quality loco but I will try to get as close as I can.

I'm aware that Julian started to build one but stopped after discovering discrepancies in the scale. Dan (steamingmess) here on the island was also involved in the construction of one but that appears to be in abeyance at the present. I also notice that Nigel Bennet's signature shows he is building one, too. Input from any of these gentlemen would be welcome, particularly Dan since he fires the real thing and probably drives it too!

 The term "diary" appears to be fairly loosely-interpreted these days so I have refrained from using it in the title.

Regards, Steve

Moderators - if you ever create a special section solely for build threads, please move this thread to that section.

[Deleted]

That's a lovely looking locomotive Steve, I for one will follow your build with great interest.

Looking forward to the start..

Regards

Pete

[flyingfox]

Greetings Steve, I was a "School Journey" visitor to the IOW in the early '50s and remember these locomotives well, we used the a lot in our 2 weekly stays, and I did have a few photos of them, now sadly lost.
last year I was lucky enough to buy a set of casting for this loco in 71/4 gauge, with some basic drawings, and it is now on my bucket list of projects, after the doubled up Martin Evans Jubilee which I have just started.
Better still, I have a cousin living in Seaview, so somewhere to stay when I come over in October.
Am I likely to see Calbourne during my visit?
Regards
Brian B

[springcrocus]

Aug 27, 2021 5:35:36 GMT flyingfox said:

...
Better still, I have a cousin living in Seaview, so somewhere to stay when I come over in October.
Am I likely to see Calbourne during my visit?
Regards
Brian B

Brian, with regard to the full-size loco the chances are very high as the IWSR expect to keep her steaming to the end of the season. With regard to the model, you would be more than welcome to visit my workshop during your stay but there might not be much to see this year. I have only just received the frames (many thanks, Ed) and I will be working on my Allchin at the same time, whilst trying to complete a transport cradle for the Britannia.

Regards, Steve

[kipford]

Steve
Looking forward to this one.
Dave

[don9f]

Hi Steve, I’m very interested too....

Regards Don

[92220]

Hi Steve.

It might be worth contacting the preservation society secretary. Most preservation societies have at least a few, original works drawings on file, which might be helpful. It is going to be a very interesting build thread!!


Bob.

[flyingfox]

Thanks for that Steve, I will be in touch.
Regards
Brian B

[andrewtoplis]

Hi Springcrocus

I'm an IWSR engineman, if you need any photos of the underneathy bits or nooks and crannies let me know, I'll be there in mid September and can take some in the evenings.

It's a lovely engine and the malachite green really sets it off nicely!

Andy

[barlowworks]

A lovely engine and I’m sure it will be a fascinating build, can’t wait.

Mike

[jon38r80]

I have some very good memories of standing on the road above the rail tunnel at Ryde waiting for those steam trains to go through and get a blast of the smoke and steam as they exited.
It will be interesting to see a model of those trains.
The smell of steam trains will always be associated with holidays for me, either on the Isle of Wight or going down to Westgate on Sea on the train.

[jma1009]

Hi Steve,

A most interesting project!

I won't repeat my stuff over the scale Don Young used.

The pencilled drawings are difficult to read, and the valve gear can be improved by a minor alteration.

Laurie Hunt in the IWMES no doubt still has the original drawings his Dad, Dennis Hunt, obtained from Eastleigh in the 1960s which did not make their way to the NRM. No doubt Laurie still has his Dad's 3.5"g example of W31 "Chale".

You might have difficulties getting the wheel castings.

Good luck!

Cheers,
Julian

[springcrocus]

Drawings

The journey begins and, before I start any machining, I've spent a good while checking over the drawings. Interestingly, there are only eight of them but they are enormous; nearly a yard high and each a serious contender for the length of the Bayeux tapestry. The first thing I did was cut them down to a more manageable size, generally getting four or six sections per sheet. One useful thing is that each drawing has an index of parts with the materials required listed on it. This was cut out separately and acts as a folder for the other sections.



It became obvious that much back-and-forth cross-referencing will be required because many items have no dimensions - "spot through from frames" being one of the favourites. I have never been a fan of "spotting through", preferring to mark out and make items accurately in the first place, so I shall be transferring dimensions to other drawings beforehand where possible.

This is my first experience with laser-cut parts and I didn't know what to expect regarding quality or price. The frames have arrived and I'm very impressed with them.



Accuracy is spot-on and the cut edges are very crisp and clean but not razor-sharp. I was also pleasantly suprised with the cost. They are advertised as "spotted" and I was a little concerned that there would be largish dimples where each hole should be but it's just a small cross at each point similar in depth to an etching. I won't be using these, all holes will be positioned using the DRO on the mill, but they would be a godsend for someone without one.



Back with the drawings and I can say that I've already found numerous instances where they differ from the actual so I'm probably going to be back and forth to Havenstreet quite a bit in the coming months. I will also be able to view a 5" gauge "W14 Fishbourne" that has recently been loaned to the railway, a model that was reputedly constructed in the 1950's by an unknown builder. I thought that Don Young prepared his drawings in the 1960's so maybe the displayed locomotive is a freelance version. According to the IWSR magazine "Island Rail" issue 91 the current owner bought it about forty year ago.

Anyway, time to start munching some metal.

Regards, Steve

[steamer5]

Hi Steve,
I've just had my frames laser cut & like you very impressed. I had all the rivet holes done as well. I had the holes done 3 mm for 1/8" rivets as I wasnt sure how they would come out. Doing this turned out fortuitous, the 3 mm holes pass a 2.9 mm drill but not a 3mm, i THINK thats due to the very small "tag" thats left were the laser starts / ends its cut, not a problems as a quick pass under the drill press will fix it, the other was the 1/8' rivets i have are actually 3.08 mm not 3.175...not really an issue but nice that the holes can be taken out to 3.1 to see how the rivets pass, if they turn out tight then 1/8" here we come!

I'll be following along too! The gent whos workshop I started this game in built an Adams, (It was his last build) sorry I cant remember which & it now resides at his sons place in another city so I cant get any info.

Cheers Kerrin

[steamingmess]

Hi steve.

Glad to see this has started.

As I said before, if you need anything (measurements/photos) do let me know and I shall see what I can do.

Dan

[springcrocus]

Thanks, Dan. With you and Andy helping with photos and measurements, I've no excuse for getting it wrong then, have I?

Buffer beams

Usually, one machines the frames first but I have started with the buffer beams. Whilst passing the local blacksmith's the other day, I stopped by and purchased a couple of feet of 40 x 40 x 6mm black angle for the princely sum of £ 2.00 and he even cut two pieces just overlong for me as well as handing me the offcut. So the first job was to get them faced accurately to length in the mill. I used a 16mm end mill for this and an angle plate to act as a backstop.

They were mounted back-to-back in the mill, raised on parallels, and skimmed with a homemade flycutter. However, the overhang from the vice caused the material to "sing" so I added a pair of "G" clamps to the ends to dampen the oscillations.



The machined faces were then brought together and the other two outer faces done he same way.

The second pair were left clamped together, upended in the vice and the bottom edges milled to size with a 16mm boring bar mounted in the collet. Once again, the faces were reversed and the other edges milled to finished depth.



Because the height differs from the depth, I marked the cutaway on the outer faces to prevent errors, then mounted the front beam face up in the vice, setting the top edge as Y0 and the centre of the beam as X0 on the DRO. I also modified all the dimensions on the drawing to reflect distances from my data points. Not all holes are shown on the drawing, however, and a hunt through found more details on a completely different drawing.



The 3/16" dia hole for the front drawhook was drilled first, followed by the holes for the buffers. However, I'm not happy with Don Young's method of fixing the buffer stocks and have made some changes.The drawing shows a separate boss screwed into the beam and the stock fitted to the boss but this means getting the rotational alignment just right. I will cover the detail a little later but, for now, I have reamed a 10mm dia hole at the central position, drilled two clearance holes and tapped two others for fixing the stocks.



The rest of the holes in both beams were finished off, including the slot in the rear beam, and attention turned to the shaping at the lower corners of each beam. My largest end mill is a 20mm diameter and this was used to rough out the shape.



To get the radius correct really requires a 1" dia cutter and, as luck would have it, one of the 20mm dia boring bars I have cuts a circle a touch under the inch. I calculated the "X" and "Y" co-ordinates, positioned the tool and plunged downwards to finish the internal shape.



There is still quite a bit to do on these but I will make the fixing angles next.

Regards, Steve

[springcrocus]

I wrote in my opening post that I plan to model "Calbourne" as she is at the present time and this became evident when I modified the very first component of the build. The buffer stocks are a little different now to how they were when DY drew up these plans and yesterday I dropped into Havenstreet to get a couple of close-ups of Calbourne's buffer beams (I also called in on Tuesday afternoon but Dan had wandered off to Smallbrook, taking Calbourne with him). Have a look at these two pictures of the front and rear beams.



The rear beam shows the stocks held with four bolts and two studs with nuts but with the 12 o'clock and 6 0'clock positions devoid of fixings. The front beam shows the stock fixed with the 3 o'clock and 9 o'clock position clear. Also, the front stock is held by four rivets and two studs and nuts.

Now look at this photo. The two stocks are held in place differently to each other.



The offside stock is held by the original four rivets and two studs with nuts but the nearside stock has had the rivets replaced by bolts. This is the kind of detail I'm going to try and get right on the model but, of course, unless one picks a moment in time and takes all one's pictures within a short time-span, then the goal is a moving target because of ongoing maintenance and repairs. In this instance, I'm going to invoke "modellers licence" and make both with bolts and studs.

Another item not covered on the drawings is the rivet detail on the rear beam.



It's likely that these rivets have been used for making repairs at some point in it's life and I shall incorporate these on the model also. A close-up of the nearside shows the rivets much more sunken into the beam than on the offside (nearest the camera) but I will model them symetrically.

The rear drawhook plate is also shown differently on the drawings (different fixing points) but I have made mine as shown in the photo.

Regards, Steve

[jma1009]

Hi Steve,

The buffers and stocks on 'Calbourne' are "self contained", and later on Don Young's 'Doncaster' he provided/designed/drew self contained assemblies rather than the LBSC type. Pete reminded me of this and I incorporated them in 'Stepney'.

You might like to consider same as an improvement on Don's drawings for 'Fishbourne'. There is a plate behind the buffer stock, and when the rear bunkers were extended the rear buffer stocks had a thick additional spacer added to the rear buffer beam.

Cheers,
Julian

[springcrocus]

Buffer support angles

The buffer support angles have been made from the same material as the buffer beams, cleaning up all the outer faces in a similar manner to the beams themselves. First, though, I had to skim the inside of the buffer beams to get flat faces and one of my seldom-used cutting tools was used to perform the task. This can cut quite close into a corner.



I wanted the four support angles to all be the same size and they were clamped together, on edge, in the vice. I didn't lock this up too tight because I didn't want to deform the angle and force them out of true. I already had a 16mm end mill in the collet so this was used to clean them up.



I also wanted them exactly 1.250" in height and a quick and easy method was used to set the height of the final pass; touch on the Hoffman roller, zero the "Z" axis DRO, remove roller.



I wasn't confident about setting up accurately in three planes simultaneously so I calculated the position of the holes for fixing to the front beam then added ten thou to my numbers, hoping to leave five thou per side to skim off the side faces. However, I managed to get my knickers in a twist with the first pair and, after dry-assembling, ended up with rather more to come off than I bargained for.



That should be reading about 4.135". I marked the two side faces 53 with a felt tip, readjusted my numbers and drilled the other pair. These came out as expected at 4.137" so those faces were marked with a 6. The angles were then returned to the vice and the faces skimmed by the marked amount. On reassembly, these now sit in the correct position.



A couple of thou over but I'm happy with that. The angles for the front beam are a little thinner than designed but they are still plenty strong enough and won't affect anything else.

I need to rivet these together before I continue with the side holes and the machining to the top of the beams but I am going to phosphate these parts, as well as the rivets, first and am waiting for a gallon of phosphoric acid to turn up from the supplier. I shall get on with something else in the meantime.

Regards, Steve

[springcrocus]

Bogie stretcher

The bogie stretcher is an assembly of parts that also supports the pivot block. I started with a ragtag collection of offcuts to fabricate this item.



I tackled the side support plates first and decided straight away to make a few changes, re-dimensioning the drawing to give distances from a centre-top datum point and adding extra holes to allow the assembly to be screwed together with 8BA countersunk screws. The plates were milled all round as a pair then drilled separately in the mill. It's much easier to work to a set of plus and minus dimensions from a central point. On the drawing, the top of the drawing is actually the bottom of the stretcher.



The various cross pieces were then machined top and bottom as a group to ensure they were all the same width (with respect to the stretcher) before milling each to their respective lengths.



With the top and bottom plates cleaned up all round, attention was then directed to the cutout for the pivot block. The centre of each plate was set on the DRO and four 4mm holes drilled in the corners, leaving about ten thou each side and end for finishing. Using plus and minus 0.406, 0.906 as my co-ordinates, a 4mm dia carbide end mill was used to remove the centres, plunging in 25 thou per pass and winding round each side in turn.



With the centres of both plates milled away, They were mounted on edge in the vice and the 8BA holes drilled and tapped to match the side plates, 1/8" down from the top and 1/8" up from the bottom Then the four components were assembled to make the basic stretcher.



The module was mounted side-on in the vice and the lower cutaways milled with a 1/4" end mill, touching on the end to set the "X" datum, then taking four lots of sixty-thou cuts to finish at 0.625" from touch-on. On the left-hand side, I tried climb-milling but it kept grabbing the work so I worked outwards from 0.625" instead. The radius of the corners is not given on the drawing but a 1/4" end mill sat nicely on the drawn form.



Next up was the large radius cutouts in the top plate and, after much head-scratching, decided to add an extra hole in my home-mad flycutter and use this to get the size. The shank of the boring bar is 8mm and the cutting diameter worked out at 0.376" so a hole was drilled and reamed 8mm diameter at (1.750 - 0.188 =) 1.562" from the centre. Then it was held vertically in the vice and an M6 tapped hole put in for a clamping screw.



With the tool loaded up and set on the centreline of the work, multiple passes were taken on the "X" axis using 25 thou depth-of-cut each time, finishing when the tool was just starting to kiss the side panels. This was set as the zero datum and a final plunge-cut at X-5 thou taken to clean the face. At this diameter using high speed steel, one would expect to use a cutter speed of about 150 RPM to avoid an excessive surface speed burning the tool but carbide is quite happy at about three time that and 420-450 RPM was used. Much easier to control at that speed.



With the ends shaped as drawn, the final job was to machine the top and bottom recesses for the top flange of the pivot block, it's retaining plate at the bottom and the final size of the width of the block itself. It is important that the two recesses are exactly in line and the module was marked accordingly. The lower plate was machined first, using the centre of the module as the X0, Y0 co-ordinate, then the inner section milled at plus and minus 0.416" for the sides and 0.917" for the ends. This was for a 4mm solid-carbide end mill.



To mill the recess, the tool was zeroed on the top of the work, then three roughing passes and a finish cut were taken, winding round on plus or minus 0.616" and 0.917" for the final cut.

The module was then flipped over side-to-side only to ensure alignment, zeroed on the centre of the "X" axis as before but keeping the existing "Y" datum. The process was then repeated for the top face using exactly the same set of numbers. Using a centre datum pretty much eliminates the chance of errors.



The section drawing at the top shows internal sides to the pivot block channel but these are not really needed and I have decided to dispense with them. This whole module is encased within the bogie frames and nothing can be seen once it becomes a complete assembly. With the outer radii linished on, this is how the finished stretcher looks. If I decide to silver-solder the module together, the countersunk screws will keep everything in the correct place.



Quite an interesting little job in it's own right, I've thoroughly enjoyed making this.

Regards, Steve