Dock Green

[N15class]

Thanks Peter. The problem I have is finding any new ones to take! I tend to avoid shots from the back forwards as there is no backscene at the front (well obviously).

Maybe need a small board with sky or a building painted on it just to block the back to front shots.

[Strathwood]

I remember the coal man delivering sacks of coal to be put in the concrete bunker at the back of the house. We then had oil-fired central heating installed in 1966, but it was back to coal-fired central heating when we moved house in 1971. The boiler was heated with hard anthracite. Some of it and its ash survives from 1978 in a couple of containers that I liberated for modelling purposes and can be seen on Cwm Bach.

Is that like Coals to Newcastle?

 

Kevin

[Strathwood]

Chaz

 

A brief warming with the soldering iron will weaken the superglue - though the gases given off by cooked superglue are probably lethal, so don't overdo it! In any case it would temporarily and locally weaken the plastic to which the superglue is attached, which hopefully will enable you get it off without breaking the buffer beam. You might want to cut the additional wires and leave their tails in the floor anyway, so you'd only have to deal with the spigot cast onto the fitting.

 

HTH

Simon

 

(And horse doings, about the size of a small apple, though I suppose it depends on the size of the horse...)

Thats it I am not eating anymore apples......

 

Kevin

[chaz]

More progress with vans...

The Slater's BR standard van now has its brake hoses to the left of the coupling slot.

 

 

These are the details cleaned up ready to fasten to a JLTRT SR van.

 

 

Applying the details to the van body with superglue means that the body can be painted.

 

 

The buffers must be added after the underframe is finished and glued in place. The buffers project behind the buffer beam and would make it hard (impossible?) to fit the underframe.

 

Checking a photo of S48916 Geoff Kent's "The 4mm Wagon - Part Two" shows it to have been an even planked van which like many SR fitted vans had round bar tie-bars between its axleguards. To make it easier to solder some brass wire to the bottom straps I cut a slot in the latter.

 

 

Chaz

Edited February 12, 2016 by chaz

[chaz]

Dock Green's next show will be Corsham in Wiltshire on Sat 9th & Sunday 10th April.

 

http://www.trainwest.org.uk/

 

only one other O gauge layout (and an On30) but a good spread of themes and scales.

 

See you there?

 

Chaz

[chaz]

I would be grateful for any suggestions...

 

My Connoisseur N7 is prone to derailing its pony wheels when running in reverse on pointwork on which nothing else derails. I have tried weighting the pony truck, which was not effective. At present it has a couple of stiff nickel-silver wire springs pressing down, one on each side soldered to a plate held firmly in place by the pivot screw but these have not cured the problem.

 

 

 

Since these photos were taken the wires have been shortened and their shape adjusted.

 

edit - just realised this is not the N7 - but the springs are similar to this but without the studs in the top surface of the pony.

 

I like this loco a lot but I can't run it if it persistently derails...........HELP!

 

Chaz

Edited February 17, 2016 by chaz

[Simond]

Chaz,

 

My immediate reaction is that the pony truck is prevented from tilting from side to side (in "roll") if there is any cross-wind in the track.

 

I suspect your journal for the pivot screw us "too good" and is providing an unwanted constraint.

 

This may be made worse by your springing, so you might want to leave that off, if practicable, for the test.

 

Can you cut a couple of slivers of thin wall brass tube and place one above and one below the pivot, loose on the screw shank, and ensure the screw is not done up tight? If my hunch is correct, this will help, may even fix it. Otherwise you might need to "cone" the hole in the journal to allow a rocking motion of truck relative to frames.

 

You may also want to check how much the rear driving axle of the loco can be lifted before the screw causes the pony truck flanges to be lifted above rail height.

 

One, or the other, of these suggestions may prove to be the issue. Fingers crossed!

 

Best

Simon

[chaz]

Chaz,

 

My immediate reaction is that the pony truck is prevented from tilting from side to side (in "roll") if there is any cross-wind in the track.

 

I suspect your journal for the pivot screw us "too good" and is providing an unwanted constraint.

 

This may be made worse by your springing, so you might want to leave that off, if practicable, for the test.

 

Can you cut a couple of slivers of thin wall brass tube and place one above and one below the pivot, loose on the screw shank, and ensure the screw is not done up tight? If my hunch is correct, this will help, may even fix it. Otherwise you might need to "cone" the hole in the journal to allow a rocking motion of truck relative to frames.

 

You may also want to check how much the rear driving axle of the loco can be lifted before the screw causes the pony truck flanges to be lifted above rail height.

 

One, or the other, of these suggestions may prove to be the issue. Fingers crossed!

 

Best

Simon

 

Thanks Simon for the helpful suggestions. I will investigate further. It hadn't ocurred to me but it may well be the case that the pony is unable to rock (tilt). I will check. Of course these "dynamic" problems are often tricky to track down....

Edited February 17, 2016 by chaz

[chaz]

Woops, sorry Simon, my earlier posting was not very accurate. Here is a photo of the pony of the N7...



As you can see the pivot screw has a spring on it that keeps that end of the pony in place but allows it to rock far more than can possibly be needed - the screw itself passing through a thin brass plate. The brass screw just to the right of the axle fixes a plate to which the wire springs are soldered. the latter can be seen either side of the body fixing screw. I made this easily detachable (thank goodness) in case the springs needed adjusting/changing etc

"You may also want to check how much the rear driving axle of the loco can be lifted before the screw causes the pony truck flanges to be lifted above rail height."   About 10mm!   Even Peco points aren't that bad.

Any further thoughts now that you have seen the real arrangement? Might a vertical compression spring acting on the pony above the centre of the axle be better do you think?

Chaz

[Simond]

Chaz

 

It looks to me like the pony truck is folded from sheet brass. It has a width of maybe 10mm, more or less half the width of the frame spacer. And the spring on the screw is trying to keep the top surface of the pony truck parallel to the frame spacer, so I guess the pony truck doesn't want to roll from side to side (roll like an aeroplane, not a wheel...).

 

Have you got a loose short bit of Peco track? Push one of the rails in, so the ends are not even, place the loco on the track and move it towards the end. If all is well, as the pony truck axle crosses the end of the shorter rail, it should droop and roll. If it doesn't, I think you've found your problem.

 

I'll be home tonight, can do a photo to explain if it's not clear.

 

Best

Simon

[daifly]

Chaz. A further thought. The witness mark of the bogie spring ends at the chassis fixing screw. Presumably at this place, the bogie can move further in its arc but the spring wire is now opposing it just on one side. Does this impose a longitudinal rolling force to the bogie lifting one wheel slightly - enough to cause a derailment?

Dave

[chaz]

Chaz. A further thought. The witness mark of the bogie spring ends at the chassis fixing screw. Presumably at this place, the bogie can move further in its arc but the spring wire is now opposing it just on one side. Does this impose a longitudinal rolling force to the bogie lifting one wheel slightly - enough to cause a derailment?

Dave

 

Possibly, however I suspect that the amount of swing implied by the witness mark does not happen in traffic - I think it would require an excessively tight curve to provoke that degree of swing. Difficult to check for though - dental mirror required?

[chaz]

Chaz

 

It looks to me like the pony truck is folded from sheet brass. It has a width of maybe 10mm, more or less half the width of the frame spacer. And the spring on the screw is trying to keep the top surface of the pony truck parallel to the frame spacer, so I guess the pony truck doesn't want to roll from side to side (roll like an aeroplane, not a wheel...).

 

Have you got a loose short bit of Peco track? Push one of the rails in, so the ends are not even, place the loco on the track and move it towards the end. If all is well, as the pony truck axle crosses the end of the shorter rail, it should droop and roll. If it doesn't, I think you've found your problem.

 

I'll be home tonight, can do a photo to explain if it's not clear.

 

Best

Simon

 

Yes Simon I have some short lengths of Peco. I will have a go and report later. Another test would be to put a small lump of something on one of the rails - this should also cause the pony to rock.

[daifly]

Possibly, however I suspect that the amount of swing implied by the witness mark does not happen in traffic - I think it would require an excessively tight curve to provoke that degree of swing. 

Fair point!

[Siberian Snooper]

A couple of questions, does it always derail at the same spot? and is the back to back correct? a slight over size may lead too the flange climbing the rail.

[Giles]

If your springs are doing their job, It's possible that they're inhibiting the sideways movement of the pony truck under pressure, leading to wheels climbing instead of following a curve. (Assuming you've got the free and easy rocking as already discussed, and that you can pick one wheel up by itself...).

Temporarily removing the springing would show that, and a cure for it may be to fold the springs back under themselves, so they acted much closer to the pivot, rather than so far out-board as at present. Or introducing a low friction sliding plate instead of wipers if they are 'grabbing'

[chaz]

If your springs are doing their job, It's possible that they're inhibiting the sideways movement of the pony truck under pressure, leading to wheels climbing instead of following a curve. (Assuming you've got the free and easy rocking as already discussed, and that you can pick one wheel up by itself...).

Temporarily removing the springing would show that, and a cure for it may be to fold the springs back under themselves, so they acted much closer to the pivot, rather than so far out-board as at present. Or introducing a low friction sliding plate instead of wipers if they are 'grabbing'

 

"If your springs are doing their job, It's possible that they're inhibiting the sideways movement of the pony truck..."

 

That's a valid point, however should that be the case the solution is not to move the spring contact point closer to the pivot - the nearer the spring acting point is to the pivot the less they would press down. If they were level with the pivot they would have no effect at all - think about it! Unfortunately removing the springs does not solve the problem - the loco was built without springs and derailed in reverse. I have progressively increased the spring pressure, to no avail. A low friction sliding plate might answer but the unpainted nickel silver footplate underside is close to that already, don't you think?

 

Chaz

[Simond]

Yes, it's perfectly reasonable to have springing acting down on the truck (though of course this will reduce the tractive weight on the drivers) and you can have centering springing, but I think this should act as low as possible, preferably, but impossibly, at rail level.

 

Dave's suggestion of the springs trying to roll the truck outwards on a curve is very pertinent. The higher the spring acts, the bigger the couple between the flange pushing one way and the spring pushing the other. But of course, if my hunch is right, then it won't roll anyway as the pivot prevents it.

 

Either way, I reckon we're in the right area, particularly if the truck can droop some 10mm.

 

What is the cheesehead screw in the middle of the pony truck for?

 

Best

Simon

[chaz]

Yes, it's perfectly reasonable to have springing acting down on the truck (though of course this will reduce the tractive weight on the drivers) and you can have centering springing, but I think this should act as low as possible, preferably, but impossibly, at rail level.

 

Dave's suggestion of the springs trying to roll the truck outwards on a curve is very pertinent. The higher the spring acts, the bigger the couple between the flange pushing one way and the spring pushing the other. But of course, if my hunch is right, then it won't roll anyway as the pivot prevents it.

 

Either way, I reckon we're in the right area, particularly if the truck can droop some 10mm.

 

What is the cheesehead screw in the middle of the pony truck for?

 

Best

Simon

 

"What is the cheesehead screw in the middle of the pony truck for?"

 

It fixes the brass plate to which the wire springs are soldered.

 

Here are a couple of photos of the tests to check how much rocking is available for the pony.

 

 

 

It would seem that the vertical movement possible is nearly 3mm either side of level - more than adequate!

 

Checking the B to B of the pony wheels with a digital vernier shows it to be 29.2mm - is this within tolerance?

 

Chaz

Edited February 18, 2016 by chaz

[3 link]

Could you fill the pony truck with some lead rather than rely on the springing?

[raymw]

I think i would try one lighter springy wire to centre of axle. You want just enough pressure to keep the wheels on the track, but not so much friction that keeps them aligned with the chassis. If it is only on one point, then obviously observe where the wheels are climbing over the rails.If the curve is too sharp, then smaller wheels, on the sort of pivot shown, will be not be parallel with the rails, but will be at an angle, so maybe the b2b needs adjusting. It'll run OK in the othe direction, it's easier to pull a wheel-barrow compared to pushing.

[chaz]

Could you fill the pony truck with some lead rather than rely on the springing?

 

This was the first thing I tried before I went to springs. it was not a success.

[Simond]

well, my hunch is clearly wrong.  So I think you need to verify Dave's suggestion - does removing the springing fix it?  I think you said that it fell off before you fitted springs, so perhaps not. 

 

Is the side swing of the truck adequate?  let's go for the low hanging fruit!

 

best

Simon

[chaz]

I think i would try one lighter springy wire to centre of axle. You want just enough pressure to keep the wheels on the track, but not so much friction that keeps them aligned with the chassis. If it is only on one point, then obviously observe where the wheels are climbing over the rails.If the curve is too sharp, then smaller wheels, on the sort of pivot shown, will be not be parallel with the rails, but will be at an angle, so maybe the b2b needs adjusting. It'll run OK in the othe direction, it's easier to pull a wheel-barrow compared to pushing.

 

Thanks for that. the derailment ocurs on a Peco "Y" which is a gentler curve than the LH/RH points, on which it never derails. This point has been the subject of much attention. The Tortoise motor's stirrup was adjusted to ensure the blades were properly seated against the stock rails. This eliminated derailments from a number of wagons that had started to argue with the point but the N7 stubbornly remains a problem.

 

I'm not at all sure how to adjust the back to back. It would be good (I think) to get that 29.2mm down to 29.0 - but how does one do that with Slater's wheels mounted on their square ended axles? Is it "safe" to rub down the backs of the wheels a little? Putting them flat on a sheet of fine emery or wet and dry and working them in a circular motion should keep it all square - shouldn't it? Losing 0.1mm from the back of each wheel doesn't sound too difficult - not compared with reducing the effective length of the axles, with their machined square ends - which is definitely scary... 

Chaz

[Siberian Snooper]

I have just had a look on the gauge 0 guild site for the b 2 b gauge and they quote 29mm for fine scale wheels and 28 mm for coarse scale wheels, so I would try reducing the b 2 b slightly.