Whatever happened to British Oak?

[John57sharp]

Thanks Mark, very helpful.

 

John

[2mmMark]

Having now reconfirmed the attendance of British Oak at the 2mm Expo for 2022, it's time to get back to work.  One of the loco conversions featured in the Beginners Guide was a Farish J94, which was one of the later Poole-designed models assembled in China. The work was deliberately kept as simple as possible, limited to having the existing wheel flanges turned to finescale standards and the back-to-back dimensions reset.

Below are the wheels after the attention of the Association's wheel-turning service.

Truth be told, it's never been a particularly good runner. It worked well enough but lacked that little bit of accurate slow running that's necessary on a layout like British Oak.  Later on, a set of proper 2mm scale wheels were fitted. These came from the late Neil Ballantine, who produced a range of drivers to suit Poole-designed Farish steam locos.  These photos show the resulting chassis, which needed a new keeper plate providing springy wire pickups to touch the flanges rather than wipe the backs of the wheels.

 

 

This improved things a little due to the lighter pressure of the pickups but the limiting factor was still the Farish motor.  The availability of very nice 12v rated coreless motors from Tramfabriek has opened up the possibility of a relatively simple remotoring.  This time I chose the 8mm diameter 16mm long motor, which looked like it would fit.

The chassis was stripped, cleaned and the gloopy paint removed.  Removing the existing motor left a gap in the chassis block so a small piece of brass was milled to shape as a filler and strengthener.
A new keeper plate was milled up from 1.5mm PCB and shaped to suggest the right frame profile.  Incidentally, new keeper plates are a good mod for non-converted N gauge locos as the factory supplied ones come down almost to rail level.  A shallower plate allows a bit more daylight in this area.

The axle slots were very slightly enlarged until the wheels spun freely. This only took a few strokes of a fine round needle file.

 

 

The long screw is there to support the front of the chassis under the body, where previously the plastic moulding supporting the armature did the job. A trial fit of the motor showed that everything fitted in the right place.

The lower profile of the chassis will allow a significant amount of lead to be added to the body.  People might be wondering about the coupling rods. The wheels and rods came from an earlier J94 I have which gained a more detailed body. This was converted before etched rods were available so the existing rods were thinned down a bit and attached to the crankpins with "top-hat" washers made using 2mm wagon top-hat bearings. Not quite as neat as crankpin washers but as the wheels are nicely quartered with the washers firmly soldered into place, I'm not going to disturb them.  Without the pickups fitted, the chassis now runs very freely indeed and will roll down a slight slope unaided.  A good starting point for what comes next.

The next job will be to mount the motor properly on the chassis.  As I've mentioned before, I'm not a fan of glueing motors in place. My preference is for a mechanical bracket or mount screwed into place. Being a cylindrical motor, the obvious approach is an appropriately sized tube.

Mark

 

Edited May 10, 2022 by 2mmMark

[Royal42]

Thanks Mark,

being a newbie to the Association, I am finding this very informative.

cheers,
Mike

[2mmMark]

As I mentioned our wheel turning service earlier, I've just seen this email come in from the Association:

"Unfortunately, due to health issues, we've had to suspend the wheel turning service (where N gauge wheels are re-profiled to 2mm standards).   All existing orders have been completed.  Please do not send any new work, anything received will be returned. 
As and when the service can be restarted, notices will appear on the 2mm website, and in the 2mm Newsletter. "

Mark

[Sithlord75]

12 hours ago, 2mmMark said:

Having now reconfirmed the attendance of British Oak at the 2mm Expo for 2022, it's time to get back to work. 

 

That's good to hear - hopefully everything goes according to plan (the chief thing being I get to come over and see it!)

[-missy-]

If its any use Mark, I have some J94 wheels designed to fit 2mmSA rims modelled and printed. I could make another set if you like?

 

 

Julia

[2mmMark]

3 hours ago, -missy- said:

If its any use Mark, I have some J94 wheels designed to fit 2mmSA rims modelled and printed. I could make another set if you like?

 

 

Julia

Thank you, that's very kind.  I can see where this might be heading...  The derailing of another quickie project.

er, I'll PM you my address.

Was it my imagination or did the 2mm shop have the correct Austerity wheels in a split frame format?  I can only see normal 8.5mm drivers in there now.
 

[Yorkshire Square]

1 hour ago, 2mmMark said:

Thank you, that's very kind.  I can see where this might be heading...  The derailing of another quickie project.

er, I'll PM you my address.

Was it my imagination or did the 2mm shop have the correct Austerity wheels in a split frame format?  I can only see normal 8.5mm drivers in there now.
 

 

The standard 8.5mm wheels are based on the Austerity (spoke count, profile etc). It was decided not list them as such, so as not to dissuade members using them for other projects!

[2mmMark]

Motor mount completed with the aid of that lovely hot silvery-looking glue.

 

 

 

 

The mount is made from a slice of K&S brass tube which I had that was a little smaller than the 8mm diameter of the motor. A horse-shoe shaped strip of brass was soldered to the tube as a fixing strap. Conveniently, the diameter of the tube matched the curved recess in the chassis block casting. The strap was secured using a 12BA screw and nut across the frame.  The tube & strap were slit lengthways and the motor just pushed in quite easily but with enough grip to hold it in place. The 0.27mm wall thickness of the tube was just right to keep worm and gear meshed nicely.

I'm very impressed with these Tramfabriek motors, spinning the worm by hand, there's no appreciable cogging or resistance from the armature. When power is applied, the motor runs quietly and smoothly.

 

The keeper plate was gapped ready for the pickup wires to be soldered on.  All it needs is just the copper surface being scraped away, which I did with a hook-shaped "skrawker".  The two large screw heads are countersunk and make no contact with the copper. The two round head screws carry the power from the plate to the motor.  On these chassis, the block is live to one side of the motor.  I'll need to find a tidy way to secure the insulated feed wire to avoid it rubbing on the worm.

 

It's going to be interesting to see how the chassis performs with the new motor.  The gear reduction is unchanged at 24:1. 

 

Mark

Edited April 1, 2022 by 2mmMark

[Nigelcliffe]

Very neat Mark.  

For the motor wire near the worm, my suggestion is a bit of L-section brass soldered to the motor mount cradle, projecting forwards past the worm.  Then tack the wire into the L-section with a small blob of glue.   

 

- Nigel

[richbrummitt]

2 hours ago, Nigelcliffe said:

Very neat Mark.  

For the motor wire near the worm, my suggestion is a bit of L-section brass soldered to the motor mount cradle, projecting forwards past the worm.  Then tack the wire into the L-section with a small blob of glue.   

 

- Nigel

Agreed Nigel and a great suggestion. 
 

Taking this idea a step further; if the angle were replaced with tube that the motor wire passes through then the motor and it’s wires have no permanent attachment so easily replaced. 

[2mmMark]

11 hours ago, richbrummitt said:

Agreed Nigel and a great suggestion. 
 

Taking this idea a step further; if the angle were replaced with tube that the motor wire passes through then the motor and it’s wires have no permanent attachment so easily replaced. 

 

I think that's the route I'll take.  It's a little tight on the sides but there's plenty of room to take the tube over the top of the motor.

[2mmMark]

With the current fine weather and in anticipation of nice summer, I felt I should treat the crew of my J94 to the cabriolet version. To achieve this, a chunk of the rear cab was milled away. It's a little bit of a faff to get it set up in my Proxxon MF70 mill but it's worth it as it's a lot easier to get a neat result than by hand filing. Mazak's not a nice metal to work so it saved clogging up a file or two.

 

As we all know, British summers can be unpredictable so a detachable hard top and a draft screen were provided.

Back on planet sensible, I hadn't really intended to do much to the body however I was faced with how to best block up the large inverted arches that passed for rear cab windows.  I know there's an etching available from RT models but I wanted to use what was immediately to hand.  A piece of 10 thou (0.25mm) thick brass was bent to shape and filed to match the aperture.  The horizontial section has been filed back to represent the bunker beading.  A full load of coal will hide the subterfuge.

 

 

The cab window grilles are done using 4mm class 37 & 40 horn grilles. These are just about the right size.

 

 

 

As always, close-ups are rather cruel. Looking at photos of these locos in industrial service (In "British Austerity Saddle Tanks" by Gordon Edgar, available in print or as an ebook), the cab rears did get pretty beaten up. In one photo, it looks like the glass got broken and was replaced by clear plastic bag taped across the opening.

 

Mark

 

Edited April 1, 2022 by 2mmMark

[Curlew]

[2mmMark]

5 hours ago, Curlew said:

That's the one.  A lot of useful bits there.  

 

[Sithlord75]

9 hours ago, Curlew said:

How does one obtain such a thing?

[Curlew]

1 hour ago, Sithlord75 said:

How does one obtain such a thing?

https://www.rtmodels.co.uk/rt_models_008.htm

[Valentin]

On 20/04/2021 at 15:00, 2mmMark said:

[...]

Later on, a set of proper 2mm scale wheels were fitted. These came from the late Neil Ballantine, who produced a range of drivers to suit Poole-designed Farish steam locos.  These photos show the resulting chassis, which needed a new keeper plate providing springy wire pickups to touch the flanges rather than wipe the backs of the wheels.

 

This improved things a little due to the lighter pressure of the pickups but the limiting factor was still the Farish motor.  The availability of very nice 12v rated coreless motors from Tramfabriek has opened up the possibility of a relatively simple remotoring.  This time I chose the 8mm diameter 16mm long motor, which looked like it would fit.

The chassis was stripped, cleaned and the gloopy paint removed.  Removing the existing motor left a gap in the chassis block so a small piece of brass was milled to shape as a filler and strengthener.
A new keeper plate was milled up from 1.5mm PCB and shaped to suggest the right frame profile.  Incidentally, new keeper plates are a good mod for non-converted N gauge locos as the factory supplied ones come down almost to rail level.  A shallower plate allows a bit more daylight in this area.

[...]

 

Mark

 

 

I have the same chassis, with the same Neil Ballantine wheels. A while ago, I managed to melt the driving gear. Could anyone confirm this is a 25 teeth gear and if I can replace it with the "GF2502 - 25 Tooth Gears for Diesel Bogies"? If so, I would replace the motor, too.

 

 

[03060]

On 22/04/2021 at 13:15, 2mmMark said:

I'm very impressed with these Tramfabriek motors, spinning the worm by hand, there's no appreciable cogging or resistance from the armature. When power is applied, the motor runs quietly and smoothly.

It's going to be interesting to see how the chassis performs with the new motor.

 

Hello Mark,

 

In your opinion was it mainly the original Farish motor that was mainly responsible for the 'disappointing performance' of your original J94 ? 

 

I ask as one came up for sale recently with a 5 pole motor, which I bought plus an RT Models detailing etch (suitably impressed by your improvements) but when tested it seemed to need a heck of a lot more juice than any of my modern N gauge locos just to get it moving. It gradually increased in speed as I let it run around my little test track as it warmed up. As you described ...a bit disappointing !

 

Regards,

Ian.

[2mmMark]

1 hour ago, 03060 said:

 

Hello Mark,

 

In your opinion was it mainly the original Farish motor that was mainly responsible for the 'disappointing performance' of your original J94 ? 

 

I ask as one came up for sale recently with a 5 pole motor, which I bought plus an RT Models detailing etch (suitably impressed by your improvements) but when tested it seemed to need a heck of a lot more juice than any of my modern N gauge locos just to get it moving. It gradually increased in speed as I let it run around my little test track as it warmed up. As you described ...a bit disappointing !

 

Regards,

Ian.

Ian,

simple answer, yes.  The Tramfabriek motor spins very freely compared to the Farish motor. The improved mechanical efficiency alone improves things. 

The basic "Poole" Farish motor design dates back to at least the early 1980s or maybe even before that. The only change was from 3 pole to 5 pole armatures.  They respond well to early feedback controllers (ECM, AMR etc.) but this can will overheat them with bad results for the white plastic bearings.  I can personally vouch for that!   Farish did not recommend using this type of controller but it was just about the only way to achieve steady slow running.  

Motor technology, size and cost have all moved on massively so what you're seeing is a vivid illustration of the developments.  The Tramfabriek website dedicates a whole section to coreless motor upgrades.   Here's an example of a Poole designed Farish class 37 being converted
https://www.tramfabriek.nl/gf-class37.html

 

Mark

[2mmMark]

11 hours ago, Valentin said:

 

I have the same chassis, with the same Neil Ballantine wheels. A while ago, I managed to melt the driving gear. Could anyone confirm this is a 25 teeth gear and if I can replace it with the "GF2502 - 25 Tooth Gears for Diesel Bogies"? If so, I would replace the motor, too.

 

 

The gear looks very similar Valentin.  Got to be worth a try for £1.79.  I believe Farish gears of this period are 72DP

 

[03060]

Thanks for the reply Mark, I sold all of my old Poole era Farish stock many years ago but having seen your J94 conversion thought that I would have this one, I probably won't need it to be quite as controllable as you require but I was a little disappointed in it's current state so will consider replacing the motor at the very least. 

 

Great link to the Tramfaberik site.  Thanks.

 

Regards,

Ian.

[Nigelcliffe]

Not disputing the advances in motors, but the old Farish 5-pole is capable of slow running with the right control equipment.   But, they seem very sensitive to mechanical issues, as well as the type of control used.   

Example I had on my bench, some years ago:   replaced the plastic bearing bushes (2nd/hand loco, had previous owner abuse, perhaps an ECM controller?), and re-assembled carefully.  Noted that current draw on motor changed with tightness and order of tightening of chassis screws - clearly something in those screws cause a slight distortion to the chassis when tightening.   Brush older replaced with insulated type, and loco fitted with a DCC decoder (CT sound model).   Result was a black 5 which could run at slower than 1inch per minute, and you could watch the armature rotating in the chassis smoothly.  And totally controllable from that silly bottom speed all they way up the range, which meant the loco would start and stop like it weighed a hundred tons.  No sign of motor heating with that setup.    
Loco went back to its owner who ran it for at least five years before selling his large N-gauge layout.  

 

- Nigel

[2mmMark]

1 hour ago, Nigelcliffe said:

Not disputing the advances in motors, but the old Farish 5-pole is capable of slow running with the right control equipment.   But, they seem very sensitive to mechanical issues, as well as the type of control used.   

Example I had on my bench, some years ago:   replaced the plastic bearing bushes (2nd/hand loco, had previous owner abuse, perhaps an ECM controller?), and re-assembled carefully.  Noted that current draw on motor changed with tightness and order of tightening of chassis screws - clearly something in those screws cause a slight distortion to the chassis when tightening.   Brush older replaced with insulated type, and loco fitted with a DCC decoder (CT sound model).   Result was a black 5 which could run at slower than 1inch per minute, and you could watch the armature rotating in the chassis smoothly.  And totally controllable from that silly bottom speed all they way up the range, which meant the loco would start and stop like it weighed a hundred tons.  No sign of motor heating with that setup.    
Loco went back to its owner who ran it for at least five years before selling his large N-gauge layout.  

 

- Nigel

The Farish mechs that we're discussing are like the classic British bikes of which I'm so fond.  Ostensibly very simple and basic but requiring skilled assembly ("blueprinting") to make them work well.  I suspect they were designed to make production and assembly affordable in a UK operation.  Peter Graham-Farish was quite proud that everything they produced was designed and made in the UK.  On the plus side of this, the mechanisms are relatively easily servicable and repairable.

The Mazak chassis blocks are fine, the variation comes in the plastic armature holder. I've seen the same as Nigel, simply altering the tightness of the fixing screws can make a difference.

Other benefits of changing the motor for an enclosed type: more space for lead weight and also a decoder, a cleaner running mechanism with none of that black carbon muck from the brushes.

The truly sensible option would be to ditch the chassis entirely and build a new one using the Association's chassis kit and components...

Mark



 

[Valentin]

On 16/05/2021 at 21:10, Valentin said:

 

[...]

 

Could anyone confirm this is a 25 teeth gear and if I can replace it with the "GF2502 - 25 Tooth Gears for Diesel Bogies"? I

 

[...]

 

After ordering and receiving this gear, I can confirm that it is a direct replacement for the gear used in the 0-6-0ST / J94 Farish chassis.