7mm The Derby Line - Rolling Stock

[dibateg]

Correct Brian, there is no height adjustment, but you know, I'm not to worried about that. I scribed a line to indicate the axle centers and then fitted the bearings to suit. As for the glass plate test, I cant be sure every piece of track they run on will be that perfect, so the springs should take up the slack and ensure all the wheels stay in touch with the rails... Contraversial I know, but the real thing doesn't sit on 10 bump stops, lets see what happens, I,ll keep you posted!
Regards
Tony

 

[Steph Dale]

You can also fit more than one spring in each guide if you need to; in theory there's room for at least three across the width of the hornblock. It's just that the ability to fit them depends upon the hornguide ( and the builder's patience! ). This would even out the load between those hornblocks on their bump stops and those on their springs. Just a thought...

Steph

 

[alcazar]

I suppose that the bump stops could be filed off, the top of the hornguides drilled and tapped, and a small screw fitted? If anyone wanted to go that far.

I can't imagine doing 30..........

 

[Steph Dale]

I've looked at that Jeff and for this particular example think it wasn't that straightforward. Can't remember why though...
It is a good trick to use when/if converting hornguides to use as sprung axleboxes as I've done a number of times with Finney ones.
Steph

 

[mickoo]

Playing devils advocate, surely it doesn't matter where you put the horn block vertically?, so long as they are all reasonably in the same plane, say, give or take 1mm then it'll have little effect on the axles. By their design these have a spring which pushes down, it will keep pushing that axle down until it meets the rail head and there it will stay.

Given that the spring pressure is pretty nominal over our expected working range 0.5 to 1mm? (pressure changes when fully extended or fully compressed) then the same weight will or should be carried by all axles, give or take.

Having one horn block 1mm higher is no different than all of them being level and the loco sat on a piece of track that is 1mm lower under one axle. It's all very well setting locos up on glass, but how many layouts have track work that is glass flat?

Expanding further, take one spring which is say 5mm long, it's likely that the working range will be mid compression, 2.5mm, now consider a working range of 1mm, the pressure change from 2.0mm to 3.0mm is going to be rather small would you not think, in fact so small it's really not worth worrying about.

I agree the first and last should be set as best one can, but the intermediates may benefit from being a nadge higher, with CSB you unload the intermediates to stop any rocking back and forth so why not set these intermediate horn blocks a touch higher.

 

[Steph Dale]

Mick,
That's almost true for locos that are carrying their weight on springs, not the case with conventional loco springs where they settle on a stop. In this latter type the vast majority of the weight is carried by only a few (typically three) horn blocks.
One other thing to consider in your example is if the horn guides on one side, or one end of the loco are tending to be higher or lower than others; then the loco won't sit evenly, even on perfect track.
I therefore suggest that the reason some like the use of an adjustment screw is naff-all to do with ride or traction (or even pick-ups), but more to do with being able to get a loco looking level when placed on the track.
Steph

 

[mickoo]

Steph, fully concur, adjustable horn blocks are I suspect as you note, simply used to set the loco stance so that it is level. Pick up, ride or traction are better served by the spring which pushes the wheel into dips.

Your right, I did kind of mix the two styles of springing up there a little, that being single action where the spring only pushes downward and upward is controlled by a stop, as opposed to double action where the axle box is free floating, like in a CSB set up.

I did also say that the first and last axle need to be set as best one can, these will determine the loco level, front to rear or side to side, however intermediates need to be the same height or slightly higher.

I have a 9F to do myself, I'm now in two camps whether to do rigid or some form of suspension, I like CSB, but it'll be visible under that boiler, actually it won't be as visible as you'd imagine, the BR classes had very large and long flat frame spacers, which almost totally (visually) cover the axle boxes and horn guides.

I suppose, at the end of the day, it's what ever your comfortable with, I see positives and negatives for each of the three principle systems.

 

[Steph Dale]

I suppose, at the end of the day, it's what ever your comfortable with, I see positives and negatives for each of the three principle systems.

You and me both. Horses for courses I reckon...
Steph

 

[dibateg]

Everything I've built so far has had adjustable hornblocks. I used a 4mm scale ply sleeper to set all the hornblocks to the same distance below the long horizontal spacer. If necessary I can pop out the springs and trim the bump stops.. The weight of the boiler fully compresses the springs to the stops...
Tony

 

[mickoo]

Everything I've built so far has had adjustable hornblocks. I used a 4mm scale ply sleeper to set all the hornblocks to the same distance below the long horizontal spacer. If necessary I can pop out the springs and trim the bump stops.. The weight of the boiler fully compresses the springs to the stops...
Tony

And I'm sure I've seen your locos running and they work exceptionally well.

If the weight fully compresses the springs and your track is flat, your almost running a rigid system then.

 

[OzzyO]

I've got a big 9 to do in the cupboard, and I've been thinking about the suspension on it.
1st, all sprung with the front and rear axles riding on the stops, with the next two allowed about 10thou upward movement then allowing the centre axle 20 thou upward movement.
2nd, only springing the three centre axles in the same way as above, so that the loco rides on the two outer axles with the springs doing the work on all of the middle axles.
3rd, the same as 2 but fitting the front axle with a rocking shaft.
4th, CSBs all axles sprung. But will I have room for all of the bits with the narrow frames and use the DJH gearbox?

All in all a lot of fun these 10 coupled locos,

OzzyO.

 

[dibateg]

Yes - it's one step on from being rigid Mick, many of my other loco's have a similar set up, fixed axle for the motor, with the other axles set to the ride height with adjustable hornblocks. Axles are free to drop into depressions in the rail. In the case of my 9Fs the chassis will sit on most of the bump stops with axles dropping into depressions in the rail, and I guess we are talking from microns to millimetres here, depending on the track....
Thanks for your thoughts Paul!

Regards
Tony

 

[OzzyO]

Hello Tony,

as you mentioned a lot/some of your locos have a fixed driven axle, if you use the intended DJH motor and gearbox this could cause a few problems as it drives on the centre axle (this would not be a good axle to have fixed as you will know, see saw and all of that).
As most of my build tend to have some form of springing I'm thinking about using a stronger spring on the centre axle.

Or are you thinking about driving one of the rear two axles?

OzzyO.

 

[dibateg]

I'm using an MSC/Chaplin motor/gearbox on the 4th axle.

Currently, I'm trying to work out how to fit pick ups, originally I was going to make my own, but there is not enough room. So I am using Slaters plungers and relocating them from the DJH position at the top of the wheel to just behind the brake hangers, so as to cope with the vertical movement in the wheel.

Regards
Tony

 

[Tim Humphreys ex Mudhen]

Tony, have you considered fitting the pick-ups to the tender rather than the loco? I have done this to two of my locos together with converting to split axles; the results have been excellent.
Tim

 

[dibateg]

Thanks Tim - yes, I've already fitted pick ups to the tenders. As my locos will be DCC I put pick ups on as many wheels as possible. There is not a great deal of options but I have managed to get Slaters plungers on 4 of the loco axles, I'll see if I can get a pic.

 

[dibateg]

So here we are, it's all a little untidy as I am experimenting. The plungers are just placed in to demonstrate positions. The flanges will be trimmed to clear the hangers on the Ragstone brake gear. The Ragstone brakes are finer than the DJH ones. The pick ups are pretty well invisible once the wheels are on.
Regards
Tony

 

[alcazar]

Tony, can I just ask for a quick explanation of:

As my locos will be DCC I put pick ups on as many wheels as possible.

Why is it more important than if you were using DC?
The only thing I can think of is for continuity of sound etc?

 

[mickoo]

Tony, can I just ask for a quick explanation of:


Why is it more important than if you were using DC?
The only thing I can think of is for continuity of sound etc?

I think some DCC systems also stop the loco, a sort of fail safe mode if the power is lost, upon return of power the throttle setting will have defaulted to zero.

I'm with Tim and am going over to tender only pick up, maybe a leading bogie wheel or something and then using a stay alive capacitor to bridge those odd gaps in conductivity and retain power to the chip. Obviously tank engines will require a different approach

 

[OzzyO]

If a 0-4-0T will work using DCC why should a 2-10-0 need more pick-ups? All you have to do is make sure that all the pick-up wheels are in contact.
The plus side of DCC is that the track is always at one power supply Approx 18v AC then the chip works the rest out.

OzzyO.