A P4 Hornby Ruston 48DS

[PenrithBeacon]

The wheels will get 'cross cornered' on the track and the vehicle won't move.

Why is this so clear to me and not to others?

[davknigh]

"The wheels will get 'cross cornered' on the track and the vehicle won't move."

 

Not my experience. I have a P4 Judith Edge Ruston 48DS. The BtoB is 17.7mm on 18.83 track. It does not 'crab' or waddle, it is a most reliable runner and will pull up to 12 wagons on straight track despite weighing in at only 65g. FWIW it is compensated and has stylus type pickups that bear down on the wheel treads so you could, at a stretch, say it was partly sprung.  Curves and point work do not present any problems with running. It is one of my most reliable engines.

Cheers,

 

David

[Michael Edge]

Thanks for the photo, it looks excellent.

[decauville1126]

With reference to the divergence of the topic theme, and my apologies, the purpose of coning on the wheel treads is to keep the wheelset parallel to the longitudinal axis on straight track and and as near as possible the same on curves. I sometimes test full-size wheelsets by free rolling, and whilst single sets can skew and derail on a curve as soon as flange contact is made, once put together as pair the tendency decreases.

 

Enjoying this thread and awaiting a successful conclusion. And I sometimes drive a loco which has a smaller wheelbase than it's gauge which does tend to hunt  but has knackered tyres anyway.

[PenrithBeacon]

10 hours ago, davknigh said:

...

Not my experience. I have a P4 Judith Edge Ruston 48DS. The BtoB is 17.7mm on 18.83 track. It does not 'crab' or waddle

...

That's interesting!

From this book 

the wheelbase of the  48DS is greater than the track gauge

I have one of these in store perhaps I need to measure it up

Edit: I just noticed that David's post is really referring to 'BtoB' which I think is 'back to back' not 'wheelbase'

Edited November 5, 2021 by PenrithBeacon
Edit added

[Michael Edge]

RH 48DS at Chapelcross power station were built to 5ft 4in gauge, I'm sure they ran in Ireland on 5ft 3In and were offered for Iberian 5ft 6in gauge but I don't have a any photos confirming this.

This all sounds very theoretical to me, practical experience suggests that it isn't a problem, at least for low speed, and the "crabbing" simply doesn't occur.

[Ruston]

14 hours ago, PenrithBeacon said:

The wheels will get 'cross cornered' on the track and the vehicle won't move.

Why is this so clear to me and not to others?

OK, I see what you're getting at now. As others have said, I don't think it will happen. It would be more likely to happen with OO than in P4 for the same wheelbase/gauge ratio on OO as you have tighter tolerances and it isn't going to slop from side to side as it may with OO.

 

How's this for a prototype where the wheelbase is far less than the gauge?

[Ruston]

2 hours ago, Michael Edge said:

RH 48DS at Chapelcross power station were built to 5ft 4in gauge, I'm sure they ran in Ireland on 5ft 3In and were offered for Iberian 5ft 6in gauge but I don't have a any photos confirming this.

This all sounds very theoretical to me, practical experience suggests that it isn't a problem, at least for low speed, and the "crabbing" simply doesn't occur.

I have a photo of a 48DS that was built to 5ft. 6in. gauge for Pakistan.

Photo of one of the Chapelcross 48DS here -

 

Edited November 5, 2021 by Ruston

[5050]

This morning I fitted the drive gear to the trailing compensated axle.  Again I had to ream it out a fair bit to be able to fit it onto the axle, the operation being done on the lathe using the tail stock to press it on against the chuck which had a 2mm 'hole' in the jaws to take the axle.

 

Here it is alongside the body.  It really is small compared to other locos in my industrial 'fleet'.

 

 

And here placed in the footplate showing how 'tight' it all is.

 

 

Since doing this I will be having to take another couple of steps back.  I've found that the geared 'beam' migrates along the axle when the chassis is run (by hand) as if it were traversing a bend.  (Note - my industrial layouts tend to have 'bends' not 'curves').  This pushes the axle gear out of mesh with the last of the gear train.  I will have to remove one wheel to be able to withdraw the axle and fit some 2mm ID brass tube spacers between the drive gear and the chassis side opposite and the beam and the chassis side next to it.  I just hope the wheel doesn't become to loose after removing and refitting although I do have some spares if absolutely necessary.  There's always Loctite too!

[5050]

Are you all sitting comfortably?  If so, let us begin the next gripping instalment.  Following my last post I investigated further and realised that the geared beam was not migrating along the length of the axle (it couldn't due to the firmly fixed drive gear) but was moving the other direction up to the inside of the footplate casting.  I attached an 80thou x 80 thou plastic spacer to the side of the beam which prevented this happening.  However (as usual with this build) this spacer was hindering the free movement of the gear beam and therefore preventing the rear compensated axle from rocking correctly.  Removal of the 80 x 80 cured this and I replaced it with some thinner plastic placed higher up the beam side.  This seems to work better thankfully.

 

The packing can be seen in these 2 photos.

 

 

You will see that the motor has been fitted.  One of HL's new ones but I did experience a problem when trying to fit the retaining screws.  I could get one in but the second just wouldn't go in. I discovered that the holes in the etch were not far enough apart and I had to enlarge them 'outwards' until both screws would fit.

 

Once the motor was fitted I could try the chassis with the bonnet and cab in position.  I had hoped that I would not find any problem with this but, as usual, the motor would not quite fit into the opening in the cab front.  Some amount of filing was necessary both to the sides (up to the bonnet location slots ar least) and also across the top.

 

 

The motor projects into the cab somewhat but a bit of black paint and a portly driver and mate should disguise this.  A length of black wire insulation will disguise the motor shaft.

 

The next stage was the provision of pickups.  My first idea was to attach very thin copperclad to the sides of the chassis and have wires pointing downwards and rubbing on the rear of the rims.  Once I was able to really think about this (and after I had araldited the copperclad in place!) I decided that the wires would be to short to offer any 'spring' so aborted the scheme.  So it was back to more conventional 'bottom mounted' rim scrapers instrad.  My normal method of mounting these is on a copperclad plate (also acting as an axle keeper plate) screwed to a 1/16" spacer fitted more or less centrally across the bottom of the side frames.  Due to the very close clearances and lack of space to fit the Quadriver and motor into the chassis I had initially considered this would not work but, in a moment of inspiration (!) I realised that if I made the fixing 'spacer' only half width and soldered it to the side of the chassis away from the gear beam I could do it.  There is very little force on the pickups so it is more than adequately strong.  Pickup 'plate' is a thinnish copperclad with 0.3mm nickel silver wires.  I had to burnish off the black coating on the tyres as it worked as a perfect insulator and no current was initally able to pass!

 

 

The wires were fitted after the photos were taken.  The plate serves as a keeper plate for both axles.  The compensated axle has clearance for movement and the main driven gear box axle has a small piece of scrap NS soldered on to minimise movement.

 

Motor leads have since been attached and the unit tested under power.  After an initial period of seeming unwillingness to move, with a bit of fettling it has now managed to perambulate along my test track, occasionally stalling (why??!) but after some more fettling I am now more confident that it will work OK.  However, until I get a chance to try it over points and bends I'm not going commit myself to saying it has passed with flying colours.

 

Now for the paint.  Corporate Blue or Red Oxide?

Edited November 12, 2021 by 5050

[PenrithBeacon]

On 05/11/2021 at 17:43, 5050 said:

This morning I fitted the drive gear to the trailing compensated axle.  Again I had to ream it out a fair bit to be able to fit it onto the axle, the operation being done on the lathe using the tail stock to press it on against the chuck which had a 2mm 'hole' in the jaws to take the axle.

 

Here it is alongside the body.  It really is small compared to other locos in my industrial 'fleet'.

 

 

And here placed in the footplate showing how 'tight' it all is.

 

 

Since doing this I will be having to take another couple of steps back.  I've found that the geared 'beam' migrates along the axle when the chassis is run (by hand) as if it were traversing a bend.  (Note - my industrial layouts tend to have 'bends' not 'curves').  This pushes the axle gear out of mesh with the last of the gear train.  I will have to remove one wheel to be able to withdraw the axle and fit some 2mm ID brass tube spacers between the drive gear and the chassis side opposite and the beam and the chassis side next to it.  I just hope the wheel doesn't become to loose after removing and refitting although I do have some spares if absolutely necessary.  There's always Loctite too!

I assembled one of these at the start of the lockdown and became very unsure of just how compensation was intended to work. I put it to one side but I've never got back to it and I'm still unsure. 

As I see it having a central beam and the arm with the idler gears in it on one axle means that there are two compensation beams on the axle.

Perhaps I'm missing something. 

[5050]

14 minutes ago, PenrithBeacon said:

I assembled one of these at the start of the lockdown and became very unsure of just how compensation was intended to work. I put it to one side but I've never got back to it and I'm still unsure. 

As I see it having a central beam and the arm with the idler gears in it on one axle means that there are two compensation beams on the axle.

Perhaps I'm missing something. 

With the beam being to one side and pivoting  (in my case anyway) loosely on the main body of the gearbox) it does allow some degree of rocking over the central pivot.  As Mike Edge said earlier, a lot of movement isn't necessary.  If you need a lot - check your track!  How it will all work in actual service is as yet unknown as I don't have my layout serviceable to test it.  It's stashed away in the attic until/when/if shows start again.

[PenrithBeacon]

Nowt wrong with the track, you built it!

Actually it didn't get that far, I made up the gearbox,  became unsure and put it to one side.

Thanks for the advice. 

[Ruston]

4 hours ago, 5050 said:

Now for the paint.  Corporate Blue or Red Oxide?

 

Green

[5050]

On 12/11/2021 at 19:55, Ruston said:

Green

That's a steam loco colour!!

 

As it's a wee delicate thing I could always paint it Pink..................

[5050]

On 12/11/2021 at 16:59, PenrithBeacon said:

Nowt wrong with the track, you built it!

But it was a L O N G time ago, anything could have happened in the meantime

 

Good to know it's still in use.

[5050]

Yes, I'm still here and adding to the thread.  Problem is I've been having some medical treatment that has meant that for roughly 2 weeks out of 3 I've been very wary of picking up a scalpel or soldering iron in case I did sometime nasty to myself!  Hopefully this is now in the past and I can get on with some more important aspects of my life such as finishing this little blighter!

 

Here is a photo of the keeper/pickup plate with wires attached and the brakes fitted.

 

 

And here one of the creature on its legs wheels  with brakes attached.

 

 

I soldered the etched brakes in 'the flat' as it was much easier to do this and then bend them down to fit.   Trouble is they probably will now get in the way of the sandpipes.  I think brakes are slightly moer important than sanding gear though.

 

Putting the body on and running it on the test plank shows that it will be reasonably good runner - but it does seem a bit noisy compared with some of the High Level gearboxes i've used.  I suppose I could always say it is fitted with a sound chip................................

[Ruston]

Good to see that you have put brakes on after all. You know that I wouldn't have let it lie if you hadn't.