Any Question Answered

[65179]

22 minutes ago, justin1985 said:

 

 

Any thoughts on which would be a better trade off in an assembled (shunting) loco? Fast motor with more weight and StayAlive? Or slow motor?

 

J

 

It's no contest Justin. Go with the coreless. Mass is important with small locos for pick up and in my limited experience coreless motors are easier to get a decently running chassis with anyway.

 

Simon

[Nigelcliffe]

7 hours ago, justin1985 said:

I'm building a second attempt at a chassis for a Bob Jones J72. ........

 

Anyway, I think I'm making pretty good progress with the replacement. But I need to decide whether to fit the hacked about franken-Mashima motor from the original kit, or substitute a modern small coreless?

 

Any thoughts on which would be a better trade off in an assembled (shunting) loco? Fast motor with more weight and StayAlive? Or slow motor?

 

 

With a DCC decoder (which stay-alive implies), you should be able to control the speed of the motor with various settings (see 2mm website for advice for Zimo and CT, some other makers will be similar).  So, the "fast/slow" motor debates of old are not really relevant.   The torque from the motor is may be relevant, and I'd expect the small coreless to be lower.   But, in a J72, chances are that wheel grip (tractive effort limit) will occur before the motor stalls due to lack of torque.  

[queensquare]

What Simon and Nigel have said, coreless every time. I have now gone through all my early locos and replaced any iron core motors with coreless. Im sure Nigel can explain the technicalities but I find they respond much better to the small DCC chips we use.

 

Jerry

[Izzy]

Like others, no contest, coreless. With DCC + SA in my experience performance won’t be an issue, and especially if you use a Zimo (or CT if you have one). 
 

However, one word of warning if I may. I have used several eBay 12v 7x16 coreless which I obtained quite a while back, before shop 3 sold them, and the performance varies and is noticeable even under DCC, some being better than others. A decent (higher) gear ratio will help offset this, which I presume the chassis will allow/is designed for, D/R 50-1 etc.

 

Bob

[Argos]

Hi Justin. One of the advantages of DCC is you can set and adjust the inputs to the motor at any speed step. 

A fast spinning motor can thus be tamed. 

That said I try and start from the slowest spinning motor I can find, with the (probably mistaken) belief this would provide more torque at any specific speed. 

Edited August 25, 2021 by Argos

[Argos]

Just realised you question had already been answered on the next page! Sorry for the repeats! 

[justin1985]

Many thanks for all of the replies! 

 

That seems pretty clear then - coreless it is! 

 

The coreless I've got here is one of a batch of four bought from eBay a good few years ago, and seems the best of the bunch. I get the impression the fear of running worms directly from the shaft of a coreless motor has subsided now? Bob's chassis is designed for that kind of arrangement rather than providing any other kind of mountings for a worm shaft. I guess if the coreless does die, they're at least dead cheap to replace now! 

 

Yes definitely planning to chip the loco. At least once it's detailed, painted, fettled and happy enough with running on DC. I've got a few small decoders waiting in a drawer, including one CT chip that's been waiting a good few years (DCX76z - don't know if this one of the ones easy to fit with StayAlive?); ZIMO 616 and 617s, and an ESU Lokpilot Nano. 

 

I guess the trick will be to make the speed curve REALLY shallow, to counteract the motor's apparently steep intrinsic speed curve?

 

Thanks again!

 

Justin

[Caley Jim]

With DCc you'll be able to control the coreless motor down to a crawl. You might have to play Around with some of the cv's but a SPROG and JMRI make that relatively straight forward. The smaller motor will, as you say, make acommodating the chip easier and give room for perhaps more capacitors. 

 

Jim 

[Jan W]

It is not possible to compare slow running of these motors with the test you did.

As you already said the iron cored motor will have to overcome the cogging where the coreless motor hardly has any resistance when running unloaded.

So it seems to perform less well on slow speeds but you'll be surprised how well it will perform in normal use.

 

Jan

[Nigelcliffe]

9 hours ago, justin1985 said:

 

I guess the trick will be to make the speed curve REALLY shallow, to counteract the motor's apparently steep intrinsic speed curve?

 

 

No, but if you read the stuff on the 2mm website it will explain how to do it. 

 

 

- Nigel

[2mm Andy]

44 minutes ago, Nigelcliffe said:

 

No, but if you read the stuff on the 2mm website it will explain how to do it. 

 

 

- Nigel

 

These articles presumably?

 

http://2mm.org.uk/articles/CT-decoders.htm

 

http://2mm.org.uk/articles/Zimo-decoders.htm

 

Andy

[justin1985]

Many thanks for pointing me to these @Nigelcliffe and @2mm Andy.

 

I'll definitely fit the coreless, and thinking of mounting it on a spacer / bracket milled from solid brass for weight. Suspect I could fit a decoder one side, and some capacitors on the other. Will mock up in plasticard to try out the combinations, and decide whether to use the CT or Zimo.

 

I'm also planning to re-make the loco boiler (originally ended up with holes for handrails etc much too big, and poorly lined up) by turning + milling from solid brass. So there shouldn't be any shortage of weight!

[65179]

Justin,

 

I'd encourage you to think about why you are doing something and what you are trying to achieve. It's not really an issue for the J72 given I assume there's plenty of scope for weight in the side tanks. However, whilst I appreciate that people like to use the kit they have (I don't have a milling machine, but if I did it would be fun to see what it could do), I do think it's easy to make things unnecessarily complicated. A brass tube boiler with lead in will have more mass than a milled brass one, gives you more control over the centre of gravity, and is cheaper to chuck away if you mess things up.

 

Simon

[Nig H]

26 minutes ago, 65179 said:

Justin,

 

I'd encourage you to think about why you are doing something and what you are trying to achieve. It's not really an issue for the J72 given I assume there's plenty of scope for weight in the side tanks. However, whilst I appreciate that people like to use the kit they have (I don't have a milling machine, but if I did it would be fun to see what it could do), I do think it's easy to make things unnecessarily complicated. A brass tube boiler with lead in will have more mass than a milled brass one, gives you more control over the centre of gravity, and is cheaper to chuck away if you mess things up.

 

Simon

I agree with Simon about using brass tube. It's much easier to solder handrail knobs into holes in brass tube than a solid brass boiler as the latter acts as a big heat-sink. 

 

Nig H

[justin1985]

12 minutes ago, Nig H said:

I agree with Simon about using brass tube. It's much easier to solder handrail knobs into holes in brass tube than a solid brass boiler as the latter acts as a big heat-sink. 

 

Nig H

 

Very good point - taken. Thanks chaps.

 

I think I'd got the idea from Bill Blackburn's approach in some part finished J15s I acquired with Long Melford (which haven't progressed any further ...). I definitely see the disadvantages though.

 

On the original J72 boiler (which does definitely need to be replaced - holes really are all over the place) I used quite coarse lead shot, and covered the open end with I think Evostick. It rattles like a maraca! I'm pretty sure I'd heard the horror stories about PVA and lead. Any other suggestions for fixing lead inside the tube? Would flooding lead shot with cheap cyano be sensible?

[Caley Jim]

I use small pieces of lead flashing glued on place with cyano. Never had any problems. 

 

Jim 

[bécasse]

51 minutes ago, justin1985 said:

 

Any other suggestions for fixing lead inside the tube? 

 

I use artist's gloss acrylic varnish, varnishing the lead balls and then letting the varnish half-dry before pushing the balls into place. The varnish is readily available almost anywhere that sells artists' materials and comes in reasonably priced small bottles which seem to last, in both senses of the word, almost indefinitely. I apply it with a small brush which is then washed out using washing up liquid and warm water.

[queensquare]

55 minutes ago, justin1985 said:

 

Any other suggestions for fixing lead inside the tube? Would flooding lead shot with cheap cyano be sensible?

 

Agree with the others about using tube for boilers.

 

I have some copper tungsten slugs I use if they fit but they are a pig to cut and machine so usually use lead sheet. For the boiler I roll it into a sausage with the aid of big pliers and a hammer - very satisfying! Trim to be a snug fit with a large illegitimate file - don't use descent files.

To fix lead the easiest way is to solder it - 145 solder works fine, fills any gaps and the brass/nickel silver doesn't need tinning. I don't bother to turn down the soldering iron for the 145 as the lead is in big lumps. 

 

Jerry

[65179]

1 hour ago, justin1985 said:

 

Very good point - taken. Thanks chaps.

 

I think I'd got the idea from Bill Blackburn's approach in some part finished J15s I acquired with Long Melford (which haven't progressed any further ...). I definitely see the disadvantages though.

 

On the original J72 boiler (which does definitely need to be replaced - holes really are all over the place) I used quite coarse lead shot, and covered the open end with I think Evostick. It rattles like a maraca! I'm pretty sure I'd heard the horror stories about PVA and lead. Any other suggestions for fixing lead inside the tube? Would flooding lead shot with cheap cyano be sensible?

 

I'm not suggesting going with the milled approach is wrong,  just that it's only one option and not necessarily the simplest. I wish I had half the skill Bill possessed! It has definitely advantages particularly if you have Tim's skills and want to do a Belpaire boiler. The value for a round topped boiler is more dependent on the available tube versus the required diameter and whether incorporating a step in the boiler avoids adding variation laminations at the smokebox end. 

 

I've used various approaches for adding lead:

- rolling up thin sheets of lead left over from dental use (I think)

- strips of lead sheet, laminated (Jubilee) or rolled and beaten (J39) depending on what it's for.

- melted in a small lead ladle and poured into a well-secured mould (normally sacrificial brass tube of the same or just slightly smaller diameter than the boiler (everything I've done recently - outside and with face and airway protection).

 

I use epoxy to hold things in place where friction isn't enough. Painting or covering the lead has been recommended by some to mitigate any lead oxide creation issues, but the lead shot and PVA problem is more a question of large surface area for reaction and plenty of acid in the mix.

 

I've not used lead shot due to the low density it provides (Did David Eveleigh do an article on that in the 2mm Magazine?)

 

Simon

[Gareth Collier]

Something I've tried recently and seems to work is tungsten putty from the world of fishing. A lot easier than hammering lead to shape and as you can squeeze it in you don't end up with any voids maximising weight. It's also slightly tacky so stays in place. Downside is it is relatively expensive compared to a bit of lead sheet.

[justin1985]

Thanks again all. Very helpful. I think on the first attempt the lead was especially inefficient in filling the space - if I recall correctly I'd asked my dad if he had any lead around that I could use, and he just cut open a shotgun cartridge and gave me the literal shot! 

 

27 minutes ago, Gareth Collier said:

Something I've tried recently and seems to work is tungsten putty from the world of fishing. A lot easier than hammering lead to shape and as you can squeeze it in you don't end up with any voids maximising weight. It's also slightly tacky so stays in place. Downside is it is relatively expensive compared to a bit of lead sheet.

 

That sounds like a very convenient idea. I had just noticed that looking for lead in small and thin enough packs to work with, most was coming up from eBay's fishing section ... The tungsten putty looks like about £5 per 20g pack - expensive per gram, but hardly the end of the world when we're talking about the amount of space inside a 2mm loco

[Klaus ojo]

2 hours ago, justin1985 said:

The tungsten putty

You are aware that the putty is not heavier than lead shim? If you want to avoid lead it is helpful and you can squeeze it into the corners. I did not know that it is so difficult to get lead shim.  I´d have some- unfortunately on the continent. Are you possibly VAG member to contact me if you need some?

 

5 hours ago, 65179 said:

with face and airway protection

As you´ve gone outside for your work: You certainly know that the most important measure when working with lead is cleanliness of the workplace and hands- especially after your work. You will unlikely produce much airborne dust when cutting or filing lead shim or soldering but the mask will remind you not to touch your face with dirty fingers. Don´t wash your working clothes together with your children´s pyjamas. Sorry, I had to write that (occupational disease) 

Edited August 26, 2021 by Klaus ojo

[justin1985]

44 minutes ago, Klaus ojo said:

You are aware that the putty is not heavier than lead shim? If you want to avoid lead it is helpful and you can squeeze it into the corners. I did not know that it is so difficult to get lead shim.  I´d have some- unfortunately on the continent. Are you possibly VAG member to contact me if you need some?

 

Thanks Klaus. I did figure that whatever material is used to make it into a putty will inevitably make it less heavy than lead formed into a solid - but the trade off sounds like being easier to push into the shape required. I've ordered both the putty and some thin lead shim from eBay, and will experiment.

 

My first attempt at the J72 was long enough ago (10+ years, probably) that eBay and Amazon weren't yet such great sources of the random things you wouldn't otherwise know where to find! Never having fished, I never would have thought of fishing gear shops as a source of lead or tungsten ... but it turns out most of the eBay listings of suitable sizes/quantities of both are in that category. 

[nick_bastable]

3 hours ago, justin1985 said:

 

Thanks Klaus. I did figure that whatever material is used to make it into a putty will inevitably make it less heavy than lead formed into a solid - but the trade off sounds like being easier to push into the shape required. I've ordered both the putty and some thin lead shim from eBay, and will experiment.

 

My first attempt at the J72 was long enough ago (10+ years, probably) that eBay and Amazon weren't yet such great sources of the random things you wouldn't otherwise know where to find! Never having fished, I never would have thought of fishing gear shops as a source of lead or tungsten ... but it turns out most of the eBay listings of suitable sizes/quantities of both are in that category. 

I have found this stuff https://www.troutcatchers.co.uk/tungsten-sheet-c2x17213338

useful at adding some extra weight

 

Nick B 

[Ian Smith]

28 minutes ago, nick_bastable said:

I have found this stuff https://www.troutcatchers.co.uk/tungsten-sheet-c2x17213338

useful at adding some extra weight

 

Nick B 

Don’t bother with this. I ordered a couple of packs a couple of years ago from troutcatchers only to find that the tungsten is “suspended” or woven into a fine mesh. It’s probably great for weighing down a fishing line whilst not poisoning anything but is quite useless for weighting model railway locos or stock.  
 

I have some small scales and when I cut a similar amount of this sheet to compare with a similarly sized piece of lead was really disappointed to find that the lead was significantly heavier.

 

Ian

 

edit to add photo of what I bought :

Edited August 26, 2021 by Ian Smith