Improving loco running

[Bigmet]

Having seen that Bachmann now have a construction scheme that makes the yet more difficult 0-4-4T pull well with no need for traction tyres, I would put money on a competent OO 14xx emerging in the foreseeable future. (I was a little surprised that Rapido didn't include it in their Thunderfield Titblot plans, especially as Jason Shron is plainly keen on UK road vehicle modelling.)

[MarkOg]

Whilst awaiting delivery of the earlier LMS 0-4-0 I have been trying a few things on the later Chinese one to see if I can improve the occasional stalling.

Shimmed the motor slightly with a few small squares of paper underneath it and bent the retaining clip a little to reduce the downward force - no appreciable difference.
Sanded off the grooves for the worm and the pinion - possibly improved - difficult to say.
Oiled all moving parts - seems a wee bit better. Incidentally what lubricant do we recommend here?
Checked B/B wheels spacing -14.6mm? Should it be any different for such a small loco?
I added a 10mm hex nut as extra weight previously. Seems to work well. Would adding further weight help?
All wheel wipers touch and are under tension against the wheel backs.

I know I may well be trying to make a silk purse, but anything simple I can do is surely worth trying. It still trundles around on speed setting 1 pretty slowly, but it does stall now and then from standstill.

Any further ideas welcome.

Thanks

[Mountain]

I find that if one can adjust the Pickups so that all Pickups touch "Just enough" and are not too strong touching the wheels, this massively improves slow speed running, but ensure the Pickups do touch the wheels if the wheels should slide sideways slightly on their axles.
Interesting you mention the cog. Ensure it is central in the chassis as sometimes motor can have shifted so it touches a chassis side. New chassis have this sticky stuff on the underside of their motors to stop them moving.

Pickups correctly adjusted make the most difference to slow running abilities on these little locos.

[MarkOg]

It is a fine line adjusting the pickups/wipers so the pressure on the back of the wheel is minimised whilst maintaining all 4 contact points during running. I don't think there is undue pressure there in any event. if I back it off/bend them back then I risk it stalling due to poor pick up contact.

Pinion is indeed centralized.

[Mountain]

Yes. Is a fine line to get them just right. Plenty of patience will reap rewards!

[Bigmet]

It is a fine line adjusting the pickups/wipers so the pressure on the back of the wheel is minimised whilst maintaining all 4 contact points during running...

There's something you need to know.

Earlier designs where the worm drives directly on the axle gear typically came with fairly beefy wipers. With very little slack in the drive line excessive pressure from the wipers doesn't help with smooth starting.

With currently manufactured multistage gear train equipped models there's no need to worry about the wiper pick up pressure on the driven wheels. This is because most have relatively delicate pick up wipers so cannot exert much pressure, and the slack in the drive line makes starting mechanically easier because there isn't much load on the worm gear as the motor starts turning.

[MarkOg]

Bigmet

Understood. I cannot think the wipers on the later Chinese 0-4-0 exert any undue pressure on the wheelbacks. They are very thin and only 2mm or so wide. Interesting what you say about the drive slack. I have some and that seems to help. Watching the worm - with the body off of course - what seems to happen when it stalls is the worm is trying to turn (very slowly) and occasionally stops - so I don't think it is a contact issue, more of a "sticktion" issue somewhere. I'll keep at it, but I think it is pretty much as good as it is going to get. I still don't like the force the numb retaining spring or whatever it is that presses down on the motor. It seems far too much, and there is no vertical play at all which I don't think helps.

[Bigmet]

Worm gears are horribly inefficient mechanically, can absorb 50% of the motor's power in a small scale model. (It's a shame that it is easily the cheapest way to compactly turn a drive through a right angle.) A little slack in the drive line means the motor can start only having to overcome the worm's drag, and not move the whole loco immediately. DCC is a useful fix: because it applies full power in high frequency pulses so the motor has plenty of torque when on power, but the loco still starts smoothly and slowly because most of the time the power is off, thus the current on average is very small.

[Bufferstop]

I've played about with samples of the N20 Gearmotor, which can be found on Ebay in many different gear ratios and 6v or 12v versions. It's about the size of the old X03. I tried one driving through a cog and crownwheel from one of the bundles of nylon gears offered for experimenting. It was promising, but my lash up was just too crude to use, one day (:roll:) I'll try again paying a little more attention to accuracy in construction. The high reductions offered in the gearboxes offer the possibility of using 1:1 or a step up for the final drive, which makes it easier to fit to small diameter driving wheels.

[Bigmet]

Much like the 'Escap' mechanism in the old 'Portescap' coreless motor plus crown and spur gear drive combination, much favoured for P4 back in the day.

Must admit I am tempted to have a go with current resources sometime, once I have largely 'cleared the decks' of all the work in progress.

[MarkOg]

The LMS 0-4-0 arrived today in almost new condition. The only difference I can see are the pick-ups. These are a one piece copper strip which is bent to wipe the 2 wheels each side with an elongated central piece which comes into contact with the motor terminals. For decoder purposes these have now been trimmed, and to test it, the decoder (TCS) from the newer Chinese 0-4-0 was soldered into place. It runs very well! Probably better than the Chinese one, so I am pleased. I intend to weather it a little and add a few details - handrail etc - so hopefully for about 30 quid I should have a nice little shunter.

The Chinese one will be fitted with a Lenz 1025 bought second hand for £10. I have no intention of spending too much money on either. I may swap the decoders if there is a marked difference in slow running, but I have a feeling both will be limited by the loco's inherently unrefined driveline.

Any recommendations please for a lubricant/thin grease perhaps for the worm/gear? Presumably thin oil of some sort for the other moving parts?

[Bigmet]

... a Lenz 1025 ...

That's a very previous generation decoder, I believe the design dates from the start of DCC. Never used one...

... Any recommendations please for a lubricant/thin grease perhaps for the worm/gear? Presumably thin oil of some sort for the other moving parts?

I have been using the Woodland scenics 'Hob-e-Lube' black grease on gear trains, driven axle bearings and slide bars for over 20 years. It stays put and lasts for years, and - killer advantage - where it is on view such as slide bars and crossheads it looks like authentic railway filth. Labelle have an equivalent. A tiny dab of light oil on the crankpins every few months, and you are done.

Don't lubricate the motor bearings until they emit the noise that says 'I'm dry' and then a tiny dab of light oil.

The rule with oil on loco mechanisms, if you can see it after application, that's too much, dab off immediately with a fluff free rag.

[MarkOg]

Thanks for that - with regard to the Lenz, I knew it was elderly, but it was cheap. It is German and I only want a basic decoder so hopefully half decent performance. I believe it also has BEMF, which will help.

[Bigmet]

Here's a little something I posted elsewhere a dozen vears ago:
Although mostly a Lenz user (and I support the assessment that for a balance of price and performance these decoders are the pick of the field) I have had great satisfaction from the Bachmann 36-553 and 554 decoders (8 and 21 pin versions of the same badged ESU decoder). For the money these have a really good silent drive, and if they match the motor characteristic well, then they can produce an on track performance indistinguishable in operation from Lenz or Zimo. The major downsides are the lack of adjustment to the speed curve, and limited adjustment range in CV 3 and 4. For my taste they work more than adequately with the intrinsically smooth running centre motor drives found in twin bogie locomotives, and it is worthwhile chopping out the capacitors to get the last ounce of refinement.

Worth looking out for if they can be got cheap.

At the time of the above quote they could be got for between £8 - £10, when the Lenz standard v1 8 pin was £20 and the Silver 21 pin was £30, and Zimo was £34 and up. Since I mostly wanted them for 21pin centre motor diesels, I bought the 36-554 in handfuls at the time, and those that went into my own locos are still doing the job; never had one fail.

Note this from the quote: if they match the motor characteristic well
That was subsequently fixed well after this was posted. The first examples I bought had a very brief note and short CV list. Then later a fuller CV list was supplied, and by adjusting CV's 54 and 55 the BEMF feedback constants could be adjusted for an optimal match wth the motor - as supplied they came set up for a large motor with heavy flywheels and were distinctly 'granular' with a small motor with no flywheel.

The big limitation was the lack of high enough values for inertia simulation on steam locos. All the diesels have CV's 3 and 4 set at the maximum which is 63. Just enough for plenty of power and fully braked diesel ops, far too small for a steamer grafting up to speed on a heavy load, or stopping an unbraked freight.

[Dad-1]

I think I've read most of the posts.
Nobody has mentioned the emergency fix of rubbing a 3B pencil
over the wheel back pick-up line. Mind you the wheel backs need to be
dry & clear of any other lubricant.

Used it quite a few times on my Hornby generic 0-4-0's.

Geoff T.