The Green Papers - being the random jottings of Doncaster Green

[Caley Jim]

I fully agree with @Izzy.  There's absolutely no need to use the biggest motor you can fit, in fact I would say the opposite.  Fit a small motor so as to leave plenty room for stay-alive capacitors.   The majority of 2mm Locos will run out of adhesion long before the motor runs out of power.

 

Jim

[Doncaster Green]

1 hour ago, Izzy said:

 

...They seem to cope with whatever is thrown at them, which using DCC just builds on, and the deciding factor on haulage is purely down to weight/mass. Use one of these along with a ratio of 30/40-1 and fill the body with lead and you should have no problems. *

 

Bob

 

* and it goes without saying a Zimo 

 

13 minutes ago, Caley Jim said:

I fully agree with @Izzy.  There's absolutely no need to use the biggest motor you can fit, in fact I would say the opposite.  Fit a small motor so as to leave plenty room for stay-alive capacitors.   The majority of 2mm Locos will run out of adhesion long before the motor runs out of power.

 

Jim

 

Hi Bob/Jim

 

Am I, perhaps, guilty of going back to my 4mm roots - cram in the biggest Mashima + gearbox or Portescap that would fit in the body?  The J94 has one of the Association 7x16's in it with a two stage drive and seems to be very good at polishing rails if progress is impeded, something I'd put down to lack of mass to stall the motor!  The J39 will be using the Association conversion chassis, again with the two stage drive, using 30:1 worm/worm wheel and 14/22 tooth to follow.  My maths are not up to it these days but I would guess that the final ratio is around 40ish :1.  Looking critically at the J39 body I can see where it may be possible to pack in some weight in the loco.  The tender (the donor loco is originally a tender drive) has a large Mazak (?) casting glued in to provide mass.  Not really needed if the drive is in the loco and removing all or part of it will provide a cavern in which to mount capacitors and a chip.

 

John

 

 

 

 

 

 

 

 

 

[Izzy]

35 minutes ago, Caley Jim said:

I fully agree with @Izzy.  There's absolutely no need to use the biggest motor you can fit, in fact I would say the opposite.  Fit a small motor so as to leave plenty room for stay-alive capacitors.   The majority of 2mm Locos will run out of adhesion long before the motor runs out of power.

 

Jim

 

Since one of the 16v tantalums in the 2MT went bang non of my plastic tender locos now have stay-alive (except the re-built Royal Scot where there was the room to use 25v tantalums so way above the track power level) on the grounds I didn't want to end up with a melt damaged body.  TBH with six wheel per side collection they shouldn't really need them. Non of my bogie diesels has them either. But I have tried one in the J15 just to see if there is any noticeable difference/advantage since the tender wheels are perhaps a bit iffy. 

 

Bob

[Caley Jim]

11 minutes ago, Doncaster Green said:

The J94 has one of the Association 7x16's in it with a two stage drive and seems to be very good at polishing rails if progress is impeded, something I'd put down to lack of mass to stall the motor! 

What do you mean by 'if progress is impeded'?  Impeded by what?  A finger - yes the wheels will spin, but what is it's haulage capacity in terms of wagons?  Why would you want to stall the motor?  That's just going to draw current.  I have a white metal bodied 0-6-0T which will haul 35+ wagons, three times what my layout is designed to handle and yes, put a finger in front of it and the wheels slip.  Remember too, that if you have a whacking big heavy motor in the tender which is driving the loco, then that motor becomes 'train weight', so the loco needs more weight to have sufficient adhesion.  Weight in the loco for adhesion is what is important, not the size of the motor.  No point in having a motor which can provide more power than the loco is able to deliver at the wheel-rail interface.

 

Jim

[Doncaster Green]

3 hours ago, Caley Jim said:

What do you mean by 'if progress is impeded'?  Impeded by what?  A finger - yes the wheels will spin, but what is it's haulage capacity in terms of wagons?  Why would you want to stall the motor?  That's just going to draw current.  I have a white metal bodied 0-6-0T which will haul 35+ wagons, three times what my layout is designed to handle and yes, put a finger in front of it and the wheels slip.  Remember too, that if you have a whacking big heavy motor in the tender which is driving the loco, then that motor becomes 'train weight', so the loco needs more weight to have sufficient adhesion.  Weight in the loco for adhesion is what is important, not the size of the motor.  No point in having a motor which can provide more power than the loco is able to deliver at the wheel-rail interface.

 

Jim

Haulage capacity is something that, until recently, I have been unable to test - my test track was only about 2ft long.  Since acquiring the layout I have tried it with 3 kit built coaches (albeit only 5 bogies - two coaches are a twin) and it seemed to handle those OK.  I must get around to fitting couplings to more of the stock! 
 

I don’t know what the prototypical capacity would be, although I’ve rarely seen pictures of J94s with more than about a dozen 4 wheelers in tow except in preservation where their Austerity cousins seem to be regularly tasked with 5 or 6 BR Mk 1 s.

 

John

[Adam]

5 hours ago, Doncaster Green said:

Haulage capacity is something that, until recently, I have been unable to test - my test track was only about 2ft long.  Since acquiring the layout I have tried it with 3 kit built coaches (albeit only 5 bogies - two coaches are a twin) and it seemed to handle those OK.  I must get around to fitting couplings to more of the stock! 
 

I don’t know what the prototypical capacity would be, although I’ve rarely seen pictures of J94s with more than about a dozen 4 wheelers in tow except in preservation where their Austerity cousins seem to be regularly tasked with 5 or 6 BR Mk 1 s.

 

John

 
BR rated them 4F, believe it or not. Load limits are obviously a bit variable, but I’ve seen 18 loaded minerals quoted for one NCB system (not flat, not the best track). The limit on the real thing is as much what you can stop rather than start, but I’m quite happy with the 30  wagons (each) my 4mm pair can shift, not that I have the space to let them do it. 
 

Adam

Edited February 11 by Adam

[65179]

As Jim has suggested, you don't want to stall the motor. In fact, in the bigger scales where it's more readily possible, then that's the test for adding weight - if it no longer polishs the rails,  but stops and stalls then you've added too much.

 

Well-balanced weight on the loco is the priority.

 

Simon

[Caley Jim]

17 hours ago, Doncaster Green said:

I don’t know what the prototypical capacity would be, although I’ve rarely seen pictures of J94s with more than about a dozen 4 wheelers in tow except in preservation where their Austerity cousins seem to be regularly tasked with 5 or 6 BR Mk 1 s.

I see no point in getting obsessed over trying to emulate the haulage capacity of the prototype.  Unless you have a big layout like Fencehouses or CF on which you can run prototype trains, what's the point?  For me all I want is for a loco to have sufficient adhesion to haul the train I envisage for it.   Weight is always going to be the limiting factor, never motor size.  I recently replaced a Branchlines Minimotor (iron cored) in a little Drummond 0-4-4T with a Tramfabreik 0615 (coreless).  It will still comfortably handle a train of 5 4-wheelers, which all I ask of it.  (And the wheels still turn if you put an obstruction in front of it!)

 

Jim

[yaxxbarl]

John,

 

Firstly on the Cab roof, I'd look at doing a new one from a piece of Nickel Silver, it worked well on the last Farish Body conversion I did. The nickel silver was from some scrap etch I had and I needed to have a double thickness of it. The roof vent hatch was made up from some other bits of scrap.

 

Haulage wise my chassis, under a Farish body, seemed to manage 15+ wagons round my test circuit without issue, it'll be interesting to see how my 3d print replacement body for the chassis measures up, I am effectively cladding the saddle tank with lead sheet, together with weight in the smokebox and bunker so it should be OK.

 

My EFE conversion hasn't been haulage tested yet but tests with an unconverted one on my test circuit had it hauling 6 Mk1s, which I think is a bit more that I've experienced on the real thing with one on the East Lancs. It seemed to perform well, even when tasked with restarting after 'herding' some escaped cattle along the line to a suitable gate where a farmer was waiting.

 

Cheers,

 

John

[Doncaster Green]

I have had a little bit of a play today and decided that the capacity of the J94 is more than sufficient for what I will be asking it to do.  I weighted the three coaches to the equivalent of five and it romped away with it, no sign of hesitation or strain.  This is probably equal to at least 12 assorted wagons which is more than I am likely to task it with.  I've also decided that, while a chip can be found a home, to fit a stayalive would require a new way of securing the rear of the chassis (the bunker is full of a metal plate with a 12 BA nut soldered to it) and I've only just managed to make that short free!  I have always intended to do two, to represent the last two in service on the C&HPR, and, to that end, have another body to modify. When, or if, the conversion chassis etch returns to stock I will revise the rear mounting so that a stayalive can be included.  Which reminds me; I must get that order for oval headed buffers into NBrass before it is too late!

 

John, the problem with the cab roof is my error.  The material I used to glaze the front spectacle is slightly thicker than the body casting and thus the roof needs a little bit of trimming on the underside so that it sits down properly.  Added to which, the glazing is standing a little proud at the top and needs filing back.  Not a big job, but one of those 'roundtoits'.  Hopefully in the next week or so and then I can get the transfers on and finish the painting.

 

The other momentous decision made today is the motive power for the J39.  I will be fitting an Association 7x16mm, partly because I've already got one and partly because there will be enough wiggle room in the tender to not only fit the chip but also provide for a straight and level drive shaft to the loco.

 

John