Any Question Answered

[oily]

I have two scratchbuilt 2mm locomotives. An M7 and a T9 that both run reasonably well and reliably on a very small DC layout.

I have spent hours and days reading up on DCC and Stay Alive capacitors, thinking maybe I should upgrade and get modern, but the more I read the more confused I get. SAC I gather might stop the very occasional hesitation?  But some say DCC does that also. Or should I go for both?

But then my problems get worse as advice gets more confusing as to what capacitors to use, what size they should be, whether one should add diodes and surge protection, to say nothing of which DCC decoder is compatible with them. And that's before you even start on the soldering them together and finding ones small enough as a lot of the advice online refers to 00 gauge.

In case it affects the advice I'm given, both locos have coreless motors and years ago I was given a Digitrax DCS51 controller although it looks horribly complicated so I've never tried it. 

Can anyone just give me a suitable 2mm scale shopping list of what to buy, or indeed whether it's all worth the effort.

Thanks

Oli

[Nig H]

39 minutes ago, oily said:

I have two scratchbuilt 2mm locomotives. An M7 and a T9 that both run reasonably well and reliably on a very small DC layout.

I have spent hours and days reading up on DCC and Stay Alive capacitors, thinking maybe I should upgrade and get modern, but the more I read the more confused I get. SAC I gather might stop the very occasional hesitation?  But some say DCC does that also. Or should I go for both?

But then my problems get worse as advice gets more confusing as to what capacitors to use, what size they should be, whether one should add diodes and surge protection, to say nothing of which DCC decoder is compatible with them. And that's before you even start on the soldering them together and finding ones small enough as a lot of the advice online refers to 00 gauge.

In case it affects the advice I'm given, both locos have coreless motors and years ago I was given a Digitrax DCS51 controller although it looks horribly complicated so I've never tried it. 

Can anyone just give me a suitable 2mm scale shopping list of what to buy, or indeed whether it's all worth the effort.

Thanks

Oli

Here is a link which might be helpful. If you saw Nick's Coal Tank   run across tissue paper drapped over some track, you'd be convinced. 

https://www.rmweb.co.uk/community/index.php?/topic/107235-2mm-coal-tank-test-build/&do=findComment&comment=2792939

 

Nig H

 

[Nigelcliffe]

3 hours ago, oily said:

I have two scratchbuilt 2mm locomotives. An M7 and a T9 that both run reasonably well and reliably on a very small DC layout.

I have spent hours and days reading up on DCC and Stay Alive capacitors, thinking maybe I should upgrade and get modern, but the more I read the more confused I get. SAC I gather might stop the very occasional hesitation?  But some say DCC does that also. Or should I go for both?

But then my problems get worse as advice gets more confusing as to what capacitors to use, what size they should be, whether one should add diodes and surge protection, to say nothing of which DCC decoder is compatible with them. And that's before you even start on the soldering them together and finding ones small enough as a lot of the advice online refers to 00 gauge.

In case it affects the advice I'm given, both locos have coreless motors and years ago I was given a Digitrax DCS51 controller although it looks horribly complicated so I've never tried it. 

Can anyone just give me a suitable 2mm scale shopping list of what to buy, or indeed whether it's all worth the effort.

Thanks

Oli

 

Yes, the effort is worth it; the transformation with a stay-alive is to a loco where you have total confidence it won't stall.

 

The thread Nigel Hunt referenced in the previous message is near the current "state of art".  Its worth reading on beyond Nick's posting. 

 

The other things I'd add are:

decoder choice - I'd go with a small Zimo as first choice (not least because they are £20), and only go to CT if space became a serious issue.   (Coreless motors are not an issue - pretty much any DCC decoder is fine with them, but decoders like Zimo and CT have specific advice and extra settings to make control even better).

 

DIY charging circuit - yes, it works fine.  But, if you have the space (and its not tiny) the Zimo SACC16 module is better than the DIY circuit, not least because it has better 16v component management.  

 

Capacitors - in tiny spaces:  Tantalums in either 220uF or 330uF - aim for about 1000uF if you can fit them (but anything will help).  In small quantities, the DCC supplier YouChoos has Tantalums at decent prices.

 

 

 

Control system.  The Zephyr (DCS51) is fine.  The Digitrax manual is a bit heavy on techno-confusion, but everything does work.   Get someone who has one to talk it through with you.   Given you have a workable system there is no point buying any replacement until you are clearer what would be "good" or "bad" about a replacement.

 

 

[oily]

Thank you both Nigels.

 

I've downloaded your messages and the contents of URLs and will study and try and absorb as much as possible.

 

Will probably need to get back though as I already feel a bit overwhelmed.

 

Yes, the Coal tank is incredibly impressive, I would love to be able to copy that, but a wish list dream at the moment. although I'm sure it's not that difficult once the first one is set up. Well, I hope so.

 

Oli

[oily]

Have a friend struggling with GWR pony truck. Does anyone have good ideas for building a successful 2 wheeled bogie?  I couldn't think of anything helpful as it seems very difficult to keep the wheels insulated with so little 'bulk' to it all.

Somebody must have made a successful 2 wheeled truck that works and is strong and looks the part?

Oli

 

[Nick Mitchell]

If I were going to scratch-build one, I would make it just like the ones in Nigel Hunt's kits.

They comprise 2 square-ish side-pieces with bearings. Thin double-sided PCB in an inverted L shape over the tops of the bearings, and a folded centre-spacer incorporating the pivot arm.

 

Here are a couple of "under construction" pictures of one such "Hunt pony" on one of his Ivatt chassis kits I built some time ago.

They are certainly successful. As to whether they look the part, you'll have to decide for yourself. (I like them!)

 

You can see I added springing in the form of an un-coiled Farish coupling spring which passes through an eyelet on top of the pony. Since I took the photo, this has been replaced with 2 springs - there was a tendency for the pony to try and rotate around the spring and consequently ride up on the inside of curves. You can also see how I have added some wires from inside the bogie side frames (at the bottom, where the PCB isn't) to the main frames for pickup. Lastly, there is a thin piece of lead stuck to the underside of the centre spacer. (The wire protruding at the front is an Electra coupling, which dips under the buffer beam.)

 

Assembly is straightforward using the Association frame assembly jig. You could make the side frames over-large, and then file them back to the outline of the center spacer to make life even easier.

 

Nigel's replacement chassis fret for the Dapol Ivatt is only £12. Your friend might consider it worth the money just for the 2 lots of pony truck parts that come with it. (Or even better, they could be tempted to build the lovely outside valve gear and give their loco an upgrade... you try oiling the inside motion of a GWR loco!)

 

The only different style of pony truck (as opposed to radial trucks) I have experience of is on Bob Jones' 9F kit. That is a slightly more complex design, which I wouldn't want to emulate without recourse to etching. I didn't spring that one (on Bob's advice) and it works fine. I also omitted pickup wires, but on a 9F there are so many other wheels it wasn't worth bothering about.

 

 

 

[oily]

Thanks, Nick, that all helpful. I have copied it out and printed it to show how it can be done.

Nothing quite like a good photograph to go with te words.

Oli

[queensquare]

Ive just picked up a Bill Bedford etch for a  M&GNR 27' passenger brake van. There was a daily parcels train from Bath to Leicester and, as well as Midland LWSR and S&D stock Id like to include the odd 'foreigner'. A nice, teak,  M&GNR van heading home via Leicester is not too far out of the realms of possibility!! 

 

Anyway, I have very little in my library on the M&GNR. Ive done an internet search but could only find a similar six wheel vehicle - the one I have is a four wheeler. Could anyone help me out with a picture or other potentially useful info such as livery etc. Evidence that these vans are unlikely to have made it as far west as Bath will be respectfully ignored!! 

 

Jerry

[chrisveitch]

I have a jar of Eilieen's 188C solder paint which is starting to dry out a bit. Does anyone know what the flux is to top it up - ordinary phosphoric acid?

[Caley Jim]

Just add some water.  That's what has evaporated off.  I have a jar of Carr's and I just keep adding some water to it when it gets a bit thick.

 

Jim

[chrisveitch]

23 minutes ago, Caley Jim said:

Just add some water.  That's what has evaporated off.  I have a jar of Carr's and I just keep adding some water to it when it gets a bit thick.

 

Jim

Great! Thanks Jim.

[justin1985]

Does this wheel need replacing? 

 

I think this is the second of a batch of 9mm loco driver wheels I've had that's been a bit dodgy.

 

I was just getting ready to solder in the crankpin to this wheel, and noticed that the hole is not aligned with the spoke, and also when the crankpin is pushed flush against the wheel, it isn't perpendicular to the axle.

 

 

I understand the most critical dimension is the distance from the centre to the crankpin hole, rather than its radial alignment. i.e. it might be visually out of quarter but still mechanically quartered etc. But with the hole also seeming to be at a bit of an angle, I'm not feeling confident.

 

Should I just replace this one rather than mess about trying to get it quartered?

 

J

[Nick Mitchell]

I think out-of-line crank-pin holes has been an occasional issue down the years. The driving wheels on my 9F are not perfect, and they were bought over a decade ago.

As long as all the wheels are the same, once the rods are on, it will probably be quite difficult to notice.

You can still quarter the wheels by eye using the spokes, as an exact 45 degrees is not necessary.

When I buy wheels to feed my gloat box, I keep them as "sets" for specific locos. My hope is that those bought together will be from the same batch and therefore have the same angular alignment. I have no idea how the hole drilling operation is set up, so my practice could of course be completely invalid.

 

As for the hole being at an angle, I would just tweak the crankpin with pliers.

People may run screaming at the suggestion, but crankpins on most of the chassis I have built have been tweaked at some point. (I have accidentally knocked a few...)

I use Simpson springs, which means the axles (and therfore crankpins) can twist slightly anyway.

Over the thickness of the coupling rods, a very slightly wonky crankpin won't make any difference once you have opened out the holes in the rods to a running fit.

 

I think it is possible build a good running chassis with those wheels - it is up to you whether they are cosmetically acceptable.

If the shop does get lots of returns and decides to sell them off cheap as seconds, I would be happy to acquire some...

 

[justin1985]

Thanks Nick - that's given me the confidence to give it a try! 

 

There was a thought of "if it's out in those two dimensions, which other ways might it be out" - but I guess it's very likely to still be in tolerance. I've set the chassis up with Simpson springs on the rear axle only - so I'll make sure this wheel goes on that one.

 

J

[Caley Jim]

I have an 0-4-4T with a chassis around 40 years old where the coupling rods are sloppy on the crankpins and two of the latter are actually loose on the wheels. (They are countersunk on the back, so can't come out.)  It still runs perfectly! 

 

Jim 

[CF MRC]

I had some wheels like that for Valour that were a bit too far off for my taste and so they were replaced.  Operationally it wouldn’t make a difference.   Even the ‘acceptable’ wheels were a bit off, and the Association crank base is a bit fat anyway, so I trimmed that area back with an exceedingly small bur and a high speed hand piece (the one that whistles).  Some engines had the crank pin in line with the spoke, some didn’t: clearly your one couldn’t make its mind up. 

 

Could breath on these for you if you wish Justin, once your happy they are working OK. 

 

Tim

[nick_bastable]

In  an attempt to get motivated I was running my Farish 3f conversion (  it still works )  this is fitted with a Bachmann 36-556RA  chip and runs fine but would like to minimize stalls so the question is has anyone worked out how/where  to add stay alive wires ?

 

thanks

 

Nick

[Valentin]

Is it smart to use 9 mm locomotive driving wheels with a 25 teeth M0.3 driving gear for which the OD is 8.55 mm? Or should I go for the 22 teeth (OD = 7.20 mm)?

[Caley Jim]

With the 25t you're only going to have 0.25mm clearance over a closure rail on a turnout. A bit risky if the closure rail happens to be a fraction high. Much safer with the 22T and the loss in gear reduction is not significant IMHO. 

 

Jim 

[Nigelcliffe]

 

On ‎16‎/‎07‎/‎2019 at 19:23, nick_bastable said:

In  an attempt to get motivated I was running my Farish 3f conversion (  it still works )  this is fitted with a Bachmann 36-556RA  chip and runs fine but would like to minimize stalls so the question is has anyone worked out how/where  to add stay alive wires ?

 

 

Don't know, but I'd suggest very careful prodding with a meter.  With the six-pin harness uppermost, the four items to the bottom right look promising places to start.  If you can trace one end of pairs of diodes to each of the track pickups, you've found the decoder bridge rectifier.  That will have positive (blue) and ground outputs from the rectifier, which is what you want.  The blue might also be on the solder pad next to the six-pin harness (because I suspect a wired version would have its blue wire coming out there).    Or google the Soundtraxx motor decoder equivalent model and see if anyone has done it. 

 

Personally I'd replace the decoder with a Zimo, because its good decoder with a clear idea what to do.  If there is space, I'd use the Zimo SACC16 PCB

rather than a DIY resistor/diode/Zener-protection setup. 

 

 

On ‎16‎/‎07‎/‎2019 at 07:48, justin1985 said:

Thanks Nick - that's given me the confidence to give it a try! 

 

There was a thought of "if it's out in those two dimensions, which other ways might it be out" - but I guess it's very likely to still be in tolerance. I've set the chassis up with Simpson springs on the rear axle only - so I'll make sure this wheel goes on that one.

 

 

If the wheel is wonky (ie. crank not in correct position w.r.t. axle) then it will run badly regardless of any springing.   

 

 

 

- Nigel

 

 

[justin1985]

Well, I don't think the suspect wheel turned out to be a problem, but this chassis really isn't rolling, and I can't work out why!

 

I carefully marked the suspect wheel, and now it's in the chassis (on rear axle) it quartered with no problems on the jig. Running with rods reversed and fitted on the central (geared) axle and the rear axle, it rolls absolutely flawlessly. However, with the rods reversed the other way and running on the central and front axles (i.e. the shorter wheelbase on the 57xx) - or indeed with them fitted to all wheels - I simply can't get it to do more than a 1/3rd revolution. 

 

All of the wheelsets are visually in quarter, and all slide effortlessly back into the quartering jig. With the rods fitted to one side, the ones on the other side drop on virtually effortlessly - which I understand to be another test of quartering? So I'm struggling to think that quartering is the issue.

 

 

None of the muffs are pinching. I'm not sure that any of the crankpins are still 100% perpendicular to the wheels, but any that were a bit out have been tweaked back into something very close to perpendicular.  The crankpins were, I think, an old bag rather than new shop stock - they measure out at about 0.51 or 0.52mm. The connecting rods were opened out with a 0.6mm drill. I couldn't see any evidence of the frames not being parallel. 

 

 

The wheelsets aren't quite pressed into gauge yet - temporarily at "Irish Broad Gauge" as Tim was calling it, to give a better chance of adjustment or being able to get the wheels back out without more damage, if needs be. Basically I left the aluminium hair clip between the inside face of the wheels and the frames when pressing them in using the jig. The central geared axle is perhaps a tad tighter (done first, before I realised the clips would make a nice temporary spacer).

 

Can I at least take the fact that the central and rear axles run well with the rods  reversed and on to rule out the problem being with those, and therefore the problem must relate to the front axle?

 

I'm reluctant to start opening out or drifting the connecting rods holes any further, without being sure that that's the issue. Is there anything else I should check?

 

J

[Caley Jim]

Are you sure that the rods are dead straight and haven't got accidentally bent? That's one of the reasons, apart from my compensated system, that I use jointed rods. Another thing is that I've found that if you turn it back and forth between the right spots they sometimes work their way out. 

 

Jim 

Edited July 19, 2019 by Caley Jim
Typo.

[Chris Higgs]

11 hours ago, justin1985 said:

Well, I don't think the suspect wheel turned out to be a problem, but this chassis really isn't rolling, and I can't work out why!

 

I carefully marked the suspect wheel, and now it's in the chassis (on rear axle) it quartered with no problems on the jig. Running with rods reversed and fitted on the central (geared) axle and the rear axle, it rolls absolutely flawlessly. However, with the rods reversed the other way and running on the central and front axles (i.e. the shorter wheelbase on the 57xx) - or indeed with them fitted to all wheels - I simply can't get it to do more than a 1/3rd revolution. 

 

All of the wheelsets are visually in quarter, and all slide effortlessly back into the quartering jig. With the rods fitted to one side, the ones on the other side drop on virtually effortlessly - which I understand to be another test of quartering? So I'm struggling to think that quartering is the issue.

 

 

None of the muffs are pinching. I'm not sure that any of the crankpins are still 100% perpendicular to the wheels, but any that were a bit out have been tweaked back into something very close to perpendicular.  The crankpins were, I think, an old bag rather than new shop stock - they measure out at about 0.51 or 0.52mm. The connecting rods were opened out with a 0.6mm drill. I couldn't see any evidence of the frames not being parallel. 

 

 

The wheelsets aren't quite pressed into gauge yet - temporarily at "Irish Broad Gauge" as Tim was calling it, to give a better chance of adjustment or being able to get the wheels back out without more damage, if needs be. Basically I left the aluminium hair clip between the inside face of the wheels and the frames when pressing them in using the jig. The central geared axle is perhaps a tad tighter (done first, before I realised the clips would make a nice temporary spacer).

 

Can I at least take the fact that the central and rear axles run well with the rods  reversed and on to rule out the problem being with those, and therefore the problem must relate to the front axle?

 

I'm reluctant to start opening out or drifting the connecting rods holes any further, without being sure that that's the issue. Is there anything else I should check?

 

J

 

How does it roll if you put a rod on only one side? If it is a crankpin throw wrong, then this should bind up on one side or the other.

 

If the rods run OK on each side with the other one off, but bind when both are on, then it pretty much has to be quartering.

 

Chris

[Crosland]

12 hours ago, justin1985 said:

I carefully marked the suspect wheel, and now it's in the chassis (on rear axle) it quartered with no problems on the jig. Running with rods reversed and fitted on the central (geared) axle and the rear axle, it rolls absolutely flawlessly. However, with the rods reversed the other way and running on the central and front axles (i.e. the shorter wheelbase on the 57xx) - or indeed with them fitted to all wheels - I simply can't get it to do more than a 1/3rd revolution. 

 

This might be a silly question, but if it runs flawlessly, why did you try reversing everything?

 

Is this the normal technique?

 

In the few chassis I have made I get it running then make sure I always re-assemble the same way if it has to come apart.

[Donw]

By reversing the rods the centre of the rods are now on either the back or front wheels leaving the ends of the rod sticking out and the wheels at the other end uncoupled. You can do this to try to ascertain which half is binding either between front and centre or rear and centre.

 

The pinch point is usually when the cranks are at 3 0 clock or 9 0 clock. I would try taking the rods off one side  move the wheels so that the side with no rod is at 3 or 9 the crankpins should now be in line with each other and the axles centres. A thin straight edge across them should show up if one is not in line which suggests a quatering error. If they are all dead in line  the problem may be an incorrect crank throw on one wheel or mismatch between the rods and the wheel base and holding the rod to the crankpins while they are inline should show this up.

 

Don