Bow Works: Locomotives for the North London Railway

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zebedeesknees
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Re: Bow Works: Locomotives for the North London Railway

Postby zebedeesknees » Tue Feb 01, 2022 11:07 am

Jol Wilkinson wrote:Gareth,

the Sharman wheels LNWR H spoke wheels are noticeably flatter - the wheel centre is actually recessed - compared to the AGW version. That is a standard spoked wheel with the brass overlay as you describe.

Unfortunately the Sharman version is no longer available in P4 although the PPP website still shows OO/EM versions available to order.

LRM CT 34RP2.jpg


Therin lies a slightly different problem for outside cylinder locos, Sharman wheels are 2.1mm wide at the tyre, 2.40mm wide at the boss, and 2.45mm wide at the pin root. Filing the boss flush shouldn't be a big problem...

Ted

Philip Hall
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Re: Bow Works: Locomotives for the North London Railway

Postby Philip Hall » Tue Feb 01, 2022 1:13 pm

Jol Wilkinson wrote:Unfortunately the Sharman version is no longer available in P4 although the PPP website still shows OO/EM versions available to order.


Here's a plug for the Society form tool - the Sharman EM wheel can (if you've got a lathe, sorry if you haven't) be easily skimmed down to a P4 profile. Even if you haven't got a form tool, taking about 7 thou off the back of the flange, even with a file, will render the flange a thickness easily able to pass through a P4 flangeway.

Philip

garethashenden
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Re: Bow Works: Locomotives for the North London Railway

Postby garethashenden » Tue Feb 01, 2022 1:31 pm

Philip Hall wrote:
Jol Wilkinson wrote:Unfortunately the Sharman version is no longer available in P4 although the PPP website still shows OO/EM versions available to order.


Here's a plug for the Society form tool - the Sharman EM wheel can (if you've got a lathe, sorry if you haven't) be easily skimmed down to a P4 profile. Even if you haven't got a form tool, taking about 7 thou off the back of the flange, even with a file, will render the flange a thickness easily able to pass through a P4 flangeway.

Philip


Or I could reuse the Gibson tire with a 3D printer center. Then the spoke profile, throw, and wheel face could all be corrected.

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Re: Bow Works: Locomotives for the North London Railway

Postby garethashenden » Sun Feb 06, 2022 8:17 pm

A bit of progress to report. I have made a motion bracket, its not pretty but its the right size, so I can get a little more of this figured out, and then make another one. The bracket should have a good amount of material outside of the frames, but there's no space for that, it hits the wheels. The motion bracket is conveniently located at the same place as one of the CSB fulcrums, because of course it is.

Image

I turned up a couple of cylinder ends and was quite pleased with them before I noticed that one of the sections I had made round needs to be elliptical. Oops. But they can be used for setting up the cylinders.

Speaking of the cylinders, neither option is the right size. The OO cylinders measure 37mm across. The P4 cylinders as 33mm across. The correct dimension is 34mm. Now it seems that the obvious thing to do would be to pack out the cylinders half a millimeter either side. But that's far too logical. I mocked that up at0.4mm and there isn't quite clearance between the piston and the front crankpin nut. I doubled the shim to 0.8mm and there is clearance, but I think going to the full 1mm would be the best option. That would put the cylinders at 35mm overall.

Image
Image
Image

I have also noticed there is a cover or shield over the leading wheels in the NLR period. I don't see this showing up in any LMS or BR pictures, so they probably removed it. Not on the GA either that I can tell, but its present on a all the NLR engines I've seen pictures of.
Image

I think the best thing to do long-term is to spend the time to learn a vector graphics program and then design my own kit. I want several of these and I keep finding more things wrong with whats currently available.

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Winander
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Re: Bow Works: Locomotives for the North London Railway

Postby Winander » Sun Feb 06, 2022 8:26 pm

garethashenden wrote:The motion bracket is conveniently located at the same place as one of the CSB fulcrums, because of course it is.

Drill the motion bracket and use it as the fulcrum. Inkscape is a good vector graphics programme, it's free and there's a lot of help on the internet to support it.
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davebradwell
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Re: Bow Works: Locomotives for the North London Railway

Postby davebradwell » Sun Feb 06, 2022 10:15 pm

I would urge you to think in terms of cylinder centres (wasn't the prototype 6ft 8in?) as that is the key dimension as far as the clearances are concerned. If the cylinder is the right dimensions then the dimension overall will follow - unless you have to move the centres out. Must say the photo suggests prototype has longer or slimmer cylinders but that may be just an illusion with the shiny paint. You should be able to work out crosshead clearances on a crude sketch before you make anything. Motion brkt will be made to match cylinders when you've confirmed what this is to be.

To get some clearance it's usual to recess front crankpin retainer into outer layer of coupling rod. In fact you could make a complete new crankpin bush with thin flange on outside, tapped M1, that just screws onto the M1 screw like a long nut. A couple of tiny sawcuts in the flange would enable it to be tightened.

DaveB

Daddyman
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Re: Bow Works: Locomotives for the North London Railway

Postby Daddyman » Mon Feb 07, 2022 8:49 am

It may be an illusion of the photo, but the cylinder (and the drill going through it) doesn't seem to be parallel to the frames?

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Re: Bow Works: Locomotives for the North London Railway

Postby davebradwell » Mon Feb 07, 2022 10:37 am

To recess the front of the boss you could make a little pin-drill (they seem to be called "couterbores") to machine a recess. Model engineering sites should have details. Go slowly when using it, though, or you'll tie your coupling rod in knots.

DaveB

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Noel
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Re: Bow Works: Locomotives for the North London Railway

Postby Noel » Mon Feb 07, 2022 11:04 am

The prototype photo showing the guard above the front wheel got my attention [no, I don't know why it's there] and made me look at the wheel. The number plate is a rebuild plate, dated 190?, so about contemporary with your period. It is not fitted with LNWR type wheels, which is what your model seems to have. A quick look round the internet did not produce a photo of one fitted with LNWR type wheels. What am I missing?
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Noel

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zebedeesknees
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Re: Bow Works: Locomotives for the North London Railway

Postby zebedeesknees » Mon Feb 07, 2022 11:44 am

Noel wrote:The prototype photo showing the guard above the front wheel got my attention [no, I don't know why it's there] and made me look at the wheel.

The guard would be to keep debris from the slide bar, but it probably didn't last. The feature doesn't appear on any of the early photographs in my possession.

The number plate is a rebuild plate, dated 190?, so about contemporary with your period. It is not fitted with LNWR type wheels, which is what your model seems to have. A quick look round the internet did not produce a photo of one fitted with LNWR type wheels. What am I missing?


The second No.78 (the first was renumbered 121) pictured in 1901, built 1892 has the Webb 'H' section wheels; the book says that some of the class were so fitted. No. 63, built 1887 and rebuilt 1901 has the more usual type of spoked wheels, 'more common on the class'.

Some later photos show locos with both types at the same time, so they would appear to have been interchangeable, and interchanged at Bow!

Ted.

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Re: Bow Works: Locomotives for the North London Railway

Postby hughesp87 » Mon Feb 07, 2022 2:53 pm

As Ted points out, at least one of the survivors, and in fact the one that's preserved (58850) had a mix of LNWR H spoke and ordinary drivers right up to its withdrawal.

58850 right side.jpg


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barrowroad
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Re: Bow Works: Locomotives for the North London Railway

Postby barrowroad » Mon Feb 07, 2022 8:36 pm

My North London tank 58850 is a Blacksmiths kit which I built rather a long time ago has the correct H spoke wheels - a mix of Sharman and Gibson if I remember rightly, plus extra pipework. Pictured at Sheep Pasture shed - although the prototype never worked that section of the Cromford & High Peak.

6811401688_0de4b0ab2e_b.jpg

Daddyman
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Re: Bow Works: Locomotives for the North London Railway

Postby Daddyman » Sun May 01, 2022 6:56 am

There are lots of photos of these tanks in the "recently added" galleries on the Rail-Online website. You have to keep scrolling as they come in batches - a couple, then another handful, then another few much later. Many are in good light and are low-level shots:
https://www.rail-online.co.uk/p265322570

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Horsetan
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Re: Bow Works: Locomotives for the North London Railway

Postby Horsetan » Tue May 17, 2022 9:20 pm

Philip Hall wrote:
Jol Wilkinson wrote:Unfortunately the Sharman version is no longer available in P4 although the PPP website still shows OO/EM versions available to order.


Here's a plug for the Society form tool - the Sharman EM wheel can (if you've got a lathe, sorry if you haven't) be easily skimmed down to a P4 profile. Even if you haven't got a form tool, taking about 7 thou off the back of the flange, even with a file, will render the flange a thickness easily able to pass through a P4 flangeway.


Interesting.
That would be an ecumenical matter.

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Hardwicke
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Re: Bow Works: Locomotives for the North London Railway

Postby Hardwicke » Tue May 24, 2022 9:51 am

barrowroad wrote:My North London tank 58850 is a Blacksmiths kit which I built rather a long time ago has the correct H spoke wheels - a mix of Sharman and Gibson if I remember rightly, plus extra pipework. Pictured at Sheep Pasture shed - although the prototype never worked that section of the Cromford & High Peak.

6811401688_0de4b0ab2e_b.jpg

I strongly suspect they were seen at Sheep Pasture on the way to or from Rowsley or Derby Works. To take them via Buxton, whilst not out of the question seems a bit awkward.
Builder of Forge Mill Sidings, Kirkcliffe Coking Plant, Swanage and Heaby. Still trying to "Keep the Balance".


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