7mm Finney Battle of Britain

[Steph Dale]

Did 10201-3 have BFB wheels then, if so, wasn't aware of that.

I'm sure your already aware, but the smaller Slaters Bulleid wheels come with 5/32" axles.

MD

They certainly did!

The smaller wheels also come with 3/16" axles (verbatim from Slater's lists):
7838 3'1" Boxpok Bogie Wheel (SR Pacifics)
7844 3'7" Boxpok Tender Wheel (SR Bullied Pacific)
vs. 5/32" axles:
7838MF 3'1" Boxpok Bogie Wheel (SR Pacifics)
7844MF 3'7" Bullied Trailing Wheel (SR Pacifics)

Steph

 

[mickoo]

They certainly did!

The smaller wheels also come with 3/16" axles (verbatim from Slater's lists):
7838 3'1" Boxpok Bogie Wheel (SR Pacifics)
7844 3'7" Boxpok Tender Wheel (SR Bullied Pacific)
vs. 5/32" axles:
7838MF 3'1" Boxpok Bogie Wheel (SR Pacifics)
7844MF 3'7" Bullied Trailing Wheel (SR Pacifics)

Steph

Ahh, good show, didn't look at the 3/16" axles as I had 5/32" bearings in the kit and used those as that's basically what the BLP and 4500 tender are designed around.

MD

 

[mickoo]

Picking the pace up a bit now, Bogie, Delta truck and tender wheel overlays completed.



These along with the drivers are now all fretted up with the insulated tender chassis for a test etch and off to PPD tomorrow.



As far as etches go it's not very well laid out to conserve space and there is a fair bit of spare space around, however that's not a problem on several counts, it's a test etch so is sacrificial, all I'm concerned about is if the wheel overlays fit the wheels and the chassis horn cheeks fold up with an accurate gap for the Slaters insulated axle boxes.

If that all works or needs minor tweaks then the sheet will be split up into a production sheet which will maximize the spacings and cram as much in.

In addition, the smallest sheet PPD handle is 12" x 6" and this just fills it, so making in neater and more compact saves you nothing.

MD

 

[Eastsidepilot]

Mick,
You've studied this more than I have with regards Boxpok wheels, on the AGH jobs I noticed that the bogie has a different pattern to the delta truck wheel is this correct ?

Col.

 

[mickoo]

Col,

That's a very good point, they're not as far as I know but now you've got me thinking, the MN are different as the delta truck is larger than the bogie wheel diameter, so the openings will be different. The Slaters wheels do not differentiate between the two and from what I can find so far....quick check of photos they certainly look the same from what is visible, which is the best part of sod all other than the rim area.

The rear looks the same as the bogie wheels but I've not yet found a clear shot of the face and being as Bulleid was trained in the Gresley way I'd like to think that a common wheel like that front and rear would be the same casting.

I'll dig some more, there's still some time before it goes to PPD (couple of days) to cross check.

MD

 

[Steph Dale]

As far as I can tell there is only one pattern of BFB 3'1" wheel and one 3'7".
Unfortunately, neither look like the Harris wheels - the blind holes in the wheel face go through the front section in the wheel so shouldn't be 'blind'. Here's an example:



BTW Mick, shouldn't all the wheels have a lip round the edge, or is that catered for in the Slater's original?

Steph

 

[mickoo]

Checking around there looks like there are several types of tender wheel, some with no bead, some with a small bead around the rim and some with a bead almost twice as large, trying to work out which rim fits which batch on preserved engines is a nightmare, either way I haven't got a bead on mine so will add a small one, it's easy to file off if you so wish. It may be the tender wheels were swapped around and come from the three different water capacity types.

I looked at Mark woods site as he's pretty good with his wheels and they don't look quite right either and quotes the delta truck at 3'-7" as measured and fitted to Sir Winston Churchill, that'd of been a tight squeeze.

MD

 

[Steph Dale]

Having the bead is a good wheeze, if it's not wanted could you not just turn the overlay over, or am I being too simplistic?

Steph

 

[mickoo]

No you're not, simple is as simple does

It shall be so number 1.

It was your picture above that I also found that threw into question the bead on the tender wheels, the photos I had of 34081 at NVR show a much smaller almost invisible bead and that was what I was working on. There are also others that appear to have no bead at all and no, the Slaters tender or engine carrying wheels do not have a bead.

MD

 

[SimonT]

Those centres were cast? Eight cores a piece, assuming the rear of the 'spokes' didn't have the overhang on the outer surface, in which case it is 16 cores. Wow!

 

[Dog Star]

Those centres were cast? Eight cores a piece, assuming the rear of the 'spokes' didn't have the overhang on the outer surface, in which case it is 16 cores. Wow!

Those wheels look like gravity castings so one bottom mould, one top mould, sixteen core pins and an axle core - unless the core pins were integral with the bottom / top moulds. I would like to know where the feeder was on such a casting...

On the other hand, the guys who designed the patterns seventy years ago were working in a different world of technology, finance and expertise.

 

[mickoo]

No don't think they're cast, they were fabricated. Certainly the drivers are as they have large undercuts behind the front face openings so the front face is not cast so stands to reason the main and rear are not as well.

If you look on the NRM site they show small previews of the wheels, think Eastleigh 30620 is one of them and it shows a cross section that might show more detail.

Certainly close ups of the drivers show traces of welding around the front face openings to the flanges below and Bulleid was a big user of welding on his engines.

The tender and bogie wheels may have been cast though, I'll need to check my references when I get home.

MD

 

[Locomodels]

This is what I found in Wiki.

The Bulleid Firth Brown, or BFB, is sometimes but inaccurately referred to as a Boxpok (colloquially, “ Boxpox”) in reference to the Boxpok wheel used by a number of US railway companies. The BFB is visually similar to the Boxpok, but is of a different design; the Boxpok is composed of sections fixed together to make a hollow shape, while the BFB is cast in a single piece, like a spoked wheel, the shape giving the rigidity needed.[citation needed]

The wheel is named for Firth Brown as well as Bulleid to give equal credit for the design: while the idea was Bulleid's, the development work, and how to cast them, was done by the company. Therefore both shared the patent. In fact one source[which?] gives BFB as meaning Beaumont Firth Brown, referring to the engineer at the firm who oversaw the development.

 

[Steph Dale]

Mick,

They are cast, that's the 'Firth Brown' bit in 'Bulleid-Firth Brown'.

There are some exceptions; the Q1 used a fabricated version, the heavily dished centres being the give-away. I've never found the answer, but suspect they were produced in one of the Southern's boiler shops where large flanging presses would have been common.

IIRC there was a one-off set of Light Pacific wheels that were fabricated, but I don't think they were particularly successful and I'd be very surprised if they were still around.

Incidentally, Firth Brown are still in existence although now known as Sheffield Forgemasters.

In terms of casting technology I think Graham is probably closest, although the drivers would need a few cores as they're a more complex shape. On the basis of an educated guess I suspect the feed is through the centre of the wheel (where erosion of the mould can be managed with an insert) and there's probably a ring of risers coming up through the waste area on the edge of the wheel.

Steph

 

[mickoo]

Yes I'd read that but being Wiki took it with a large pinch of salt

I only questioned the drivers as close up views seem to suggest weld lines and the large undercuts behind the face at the rim would be a nightmare to cast, but then I'm not a cast master and they obviously know their job better than I

MD

 

[SimonT]

I now think that there are undercuts on the back, so 16 sand cores per wheel. Presumably the hole is to register the core into the outer mould.

 

[adrian]

Noting Paul's comment that the BFB wheel is a different design to Boxpok, however for interest The T1 Trust have been casting new Boxpok wheel.

So although the Wikipedia article says that the Boxpok wheel is "composed of sections" it does appear in the T1 video that it is cast in a single piece like the BFP wheel - unless I'm missing something.

In response to @Dog Star query on the feeder on the T1 casting they seem to have 2 feeds in diagonally opposite corners of the casting box.

A gallery of images for the pattern here driver wheel pattern.

 

[Eastsidepilot]

The reason I asked about the wheels was that the AGH set I processed had a different pattern for the trailing wheel, although the same dia. as the bogie it has a more elongated hole between the spoke? whilst the bogie has a round hole.
I should have mentioned that these are for a West Country.

Col.

 

[mickoo]

Col, as far as I can tell the 3'-1" wheels for the West Country bogie and delta truck are the same and the 3'-7" tender wheel is the same as the Merchant Navy delta truck, though I cannot prove it photographically yet nor check a real engine. The delta truck on both the BLP and MD virtually covers the wheel face, so the only sure way to check is get down on the floor and peer between the two.

So if your delta wheels have elongated holes and they're wrong, you're never going to see it to know once the model is complete.

MD

 

[Dog Star]

Mick,

Some of the Finney range have multiple sets of frame stretchers, for example:- the A4, such that those who wish to build for S7 standards can set the frame plates at a separation which is closer to a scale distance. I have looked through the BLP A3 instructions and I think that there is just the one set - presumably for 32mm modellers - please advise if this view is correct.

thank you, Graham