bertiedog

I am interested in the Wireless World and will arrange a copy, without seeing it I would assume PWM in base, as no other way gives such control. Feedback can help slow speed, but most aim at constant speed for gradients, Codar used to make one, and I have the circuit stored, but it is not wonderful on crawl. It was an early user of momentum effects. It would be fine for larger layouts. All feedback controllers are lost with multiple motors, banking, US units in tandem or more, the intermittent contact that must occur despite all efforts to keep everything spotless and all wheel contact, will lead to lurches as the tiniest feedback signal is used to correct what has not happened. Now I hear the man at the back saying he uses feedback with multiple motors, and in real life the makers of the units add hysteresis to the circuit, sudden changes do not cause sudden jumps, but some locos may still be sensitive and react, and the choice of the lag is critical, too much damping, and you might as well have no feedback. Personally I do not like feedback where there is a large amount of different locos to run, as they all behave differently, only slight, but it is there......and my feeling is that you are the driver, and should be in control on gradients anyway!!....... To get the best of both ways, do not modify one type or the other, just have both and switch in as needed, A regulator based 0 to 12vdc, with pure DC(handles anything in sound order)., a PWM for shunting, and maybe a feedback type for mainline loop running on a big layout.................or buy DCC...........trouble is the word BUY...............DCC is very pricey indeed, as all three circuits coud be built for about the cost of a single Lenz decoder. Also as before, join MERG it is the source of a lot of help, and masses of experience, although prepare to have your arm twisted towards the dark side, DCC.........there are those in there who still resist it though.

Unfortunately as far as increasing the frequency of the PWM type, you can't do much, as above the lower frequencies of about 100 hz it becomes very audible, and would then need to jump to 20 khz to work without the sound generated. PWM would work at 20khz, but only to adjust the range of speed around a value, control from zero to max impossible because of hysteresis in the magnetic field in the motor. It works with specialist coreless motors quite well for laboratory uses etc, and control equipment, but not models. Stephen.

I have breadboarded the design this afternoon, and it all works fine, although the diagram shows the transistor as normal, it is a Darlington pair type, and any rated above the specified would do, it is the gain they are after here. Also I used the higher rated regulator, why down rate for a few pence. No fuse is needed, it's self regulated, but I would add LEDs to show AC power in and DC out. It works with 5 pole motors very well, it does make a three pole a touch noisy, but very controllable. For coreless near useless, it could be tamed, but why bother there are better plain DC controllers for these. I will transfer to a PC pad board and re-test, perfect for the new Shortline I am building.

Have you the circuit to post here, bearing in mind the authors copyright, or it could be posted to Photobucket etc., and referenced. Stephen.

A Full PWM type circuit, (Constant voltage), very interesting, I use Mr Penfolds version, (in Bambini books on the 555) with 555's generating the pulses, resulting in exactly the same square wave forms. This type works very well indeed for control. especially shunting, but as the other postings on the US design for variable voltage with pulse say, it can over heat the motors, but only under load on long runs on the main lines, light load, and short runs no issue. Crawl control cannot be bettered with PWM, no way any other circuit can be superior, but only at these low speeds. Such PWM controllers can make some motors hum and noisy, again it varies, well set up motors do not mind, but add loose bearings, and dry gears, and you have noise, add tight gears, resilient mounts, and grease lube, no issue. My own mods to the 555 driven type of PWM are to raise the frequency and use capacitors to smooth the output, which are switchable to suit different motors, this also reduces potential motor heating as the RMS value of the output is lowered. Motor heating is not serious on PWM as such, it is after all nothing to do with applied voltage, it is the average current drawn under load, less efficiency, that is the heat source, not the higher voltage pulses, as nothing is applied at all in the gaps!! But yes, under load the magnetic field behaves dynamically, and despite all theory, the motors heats up more on square wave pulses, than plain DC. The motor operates on the average of the pulses, but the mean value is not linear as the load increases and more inefficiency occurs...result heat. The back EMF is also high with pulses, and contribute to the heating, as with coreless motors, which should not be used on PWM, they can burn out in extreme load conditions,. Coreless are often driven by PWM signals in electronic equipment, but are in constant known load limits, and are quite safe then. Therefore PWM CV type controller...perfect for micro layouts and switching layouts...not for large club layouts with legions of locos of different types. Stephen.

The circuit is fairly straightforward, although for non electronics builders a bit short of some basics like the power connections to it! ..you have to assume a lot, .......also the UK 50 hz mains frequency difference from 60hz in the States may explain the slower responses to the commands, meaning lower some of the trimming values ,as you found, to compensate. All parts are available easily and not costly, although the reversing relay adds a bit. Substitute transistors,(properly chosen), would work, nothing is too critical. It would be a very good general purpose circuit, and removes most risk from pulses noise and potential heating effects. Stephen.

There are lots of suitable designs on the net, but as you say how do you know what they really do? I know, as an electrical engineer, but even then the circuits may not work as expected, so it needs recommendation, and the best course is to join the MERG group, who are a club, shop, group of enthusiasts etc, and have the experience to say what works and what does not. Your requirement is for control of older "type" motors, none the worst for that, straight DC, with feedback may be the best, with variable pulse available in a switchable form. It would be the same for an all Mashima fleet, they just have lower draw on current. Feedback works where a fleet are basically the same motors, otherwise it has got to be in some way adjustable. Double motored locos cause problems with feedback and don't work with the set-up. The best control for low speeds are variable mark space CV (constant voltage) controllers, but if the motors are 3 pole and 5 pole on the same layout there may be differences, and such controllers are able to make the motors hum due to the pulses. The next best are feedback controllers, which can be CV mark space types or pure DC, or a mixture, a circuit that senses the load and back EMF, trying to maintain a constant current drain, again when pulses are used the motor may hum at low speeds. But after all the extras are removed a pure DC supply is able to run any type of motor without hum, and straight forward variable voltage regulator chips, which have built in overload protection are the best all rounder. Commercial designs try to deal with as many variables as possible, so building your own can fine tune to what you have much better. It is also very inexpensive,... £10 would build a comprehensive spec., controller, with the exception of the transformer for power, the most expensive item. hope this helps, Stephen.

Superb for track, but don't forget that RTR points are difficult to alter, a friend had started re-spacing Peco and then realised he would have to alter the points or build more scale ones like C&L etc.

Not Madness , but an oddity, a strange mating of a Mallet, shown as 082,.......and a BR standard six wheel tender, the seller is absolutely up front about it, but........!! ..I do like the "fits quite well" http://cgi.ebay.co.u...e=STRK:MEWAX:IT Stephen.

" 'ou mean it don't go a'rond"?.......look at the track , the fall away is built in....they taper evenly......

Come on,the weathering alone must be worth the £3.99...the Lima a low value as usual....

The other postings cover this , but may I add that many models are wrong on this point, it is rarely portrayed correctly on models, it is a complex area as not only "mass" is balanced, but also potential power thrust is taken into account, which was a matter dealt with by the CME's experience, often not scientific design. I'd be far more concerned the designer of the loco left moulding lines on the cranks, quite unnecessary, especially on a high priced model loco. Stephen.

More notes for poster and other users.....use advice as relevant.... I am afraid the results you got were typical, as Relco did not supply the clearest of instructions, and modified the unit to two ways of operating, one being in series with the whole lot, which gave the interference, and powering with a separate feed with suppressing capacitors and RF chokes, which was the later way now adopted by other makers. The capacitors and the correct fitting, preferably with RF chokes as well are vital, and all locos have to have fully working suppressors and RF chokes as well. Most users are not electrical Engineers, and Tri-ang and other makers barely helped in the old days with decent suppressors. Steel track never worked well with Relco, the chance of a bad contact was more, and the unit fires up all the time. The voltage being felt is in the hands of the Gods, some people are very sensitive to any voltage. The shocks were an indicator the track and loco pick-ups were bad, and the unit was working overtime!! As can only be repeated, first clean everything, and then the Relco keeps it going,(as does DCC on it's own in similar way) People forget the wheel pick-ups being out of contact also made the unit fire up, any loss of contact did, so and an old Tri-ang loco with steel wheels on steel track with slack pick-ups was a very poor recipe for success, the Relco unit must have been running all the time. Quite how an "out of action, but power connected on" track would trip the Relco into continous operation is very difficult to understand, it's impossible in theory, as the Relco shuts off when there is no load, but attempts to apply a high voltage, but it has nowhere to go, unless the track was in some way so corroded that partial current could flow and kept tripping the unit. The proper capacitors and choke in the power feed cures this sort of situation occurring. This condition will not occur on any normal modern track like Peco. Oddly fine scale track with pc sleepers can have trouble, the gaps can conduct if dirt builds up. Make absolutely sure the capacitors are fitted and RF chokes as well. Stephen

The original boxes for the Acro Teeaness Bogies. Any body get a catalogue surviving? Stephen.

Inserted Edit I think you may be mixing up terms for a "short" , with a "break", which is what sets off Relco. I do see that you see the decoder and motor load as a "short", and this goes as the break occurs, I agree, quite right, the lack of flow is the set off point. Covered before in the replies, if many contacts are made the unit will not work, but then the loco is running fine,so it is not needed at that point. Most of the time it does nothing, it only fires when needed, when run right, all is all right!! It does not clean 2 inch strip of dirt, it does not clean at all, it gets the current flowing only in the micro second the current vanishes, breaks the gap, and then microseconds later the normal operation returns. It's normal operation is too "not be operating", just like a fire brigade, always there, but you hope never called upon, so to speak. In practice it does fire up all the time, randomly and it does indicate this with the cleaner wheels evidence, although again it does not clean them off as such, it keeps clean wheels cleaner. Stephen.

Yes Acro, and the makes were all the same, or connected. I'll go and get the boxes and the camera, fortunately they came boxed in original tissue etc. They were sometimes looked on as simple construction, but the joy was the one piece construction, true and accurate. The failing was the brass spring sometimes not matching the outer frames, axles did not always line up, I guess from the range the factory picked out the wrong base to assemble sometimes, as I can't believe they went to all the trouble of a casting without matching the spring bearing plate. The heavy Exley's and Hamblings coaches run very well on these, but they need the extras added like tie bars, cross brake bars, and brake shoes. Sayer Chaplin die cast coach shoes, later done by Hamblings appear designed to fit (or the other way round).

Some older UK made Model railway items, some sets of LMS and GWR bogies from Arco, made in the 1950's and early 1960's. (From Ebay). One piece die cast bogies, no brake shoes or tie rods, they had to be added by user, but fully sprung, with internal bearings. They are superb runners, the wheels have a fine profile, and run absolutely true, and the other pair fitted to an Exley body run though the test track to perfection. They need a strip, added brake shoes, Sayer Chaplin cast coach brake shoes, and tie bars fitted, and a proper re-spray with an undercoat, which they do not have at the moment. Surprisingly free running, no pin points here, plain internal bearings, but they are very smooth. Destined for some Exley GWR and LMS coaches under restoration at the moment. Stephen.

A quickly grabbed shot at speed of the secret Eurostar testing the new French Duvet to keep it warm in France before the tunnel......

Yes, I have the plan already, it is of an early open top type, not quite the type actually mentioned by Neil Munro, who placed Skipper Para Handy in a wheel house in several incidents in the stories, but as the Vital Spark would have been old in 1920 it could have been a conversion from an early open tiller type, always in those cases one of the Crinan canal lock restriction type. many thanks, Stephen

Many thanks for the kind offer, I have to admit that I do know a bit about Puffers, having built several now, and having a scratch built R/c one that was an entry for the Model Engineering Exhibition and the Sandown, and Brighton model shows. I'll PM the email to you as any extra shots are worthwhile, although I have never modelled one of the War Dept VIC types. Photos of the early "real" puffers are quite rare, I have the books etc, and some privately sourced stuff, and a DVD copy of "The Maggie"!! I have also sat through modellers talking about "The Vital Spark" and how accurate a model is, biting my tongue, before reminding them gently that it is all fictional from the pen of Neil Munro, writing as Hugh Foulis!. The current "Vital Spark" is a Vic dressed up as an earlier type. With Puffers it's all the extra bits and pieces that make the model, this new one is not quite right on a lot of points, but with additions and cover ups more than passes muster. I am trying to source a good material for the tarpaulins! They are needed as the wooden covers are a bit simplified, with no way to secure or remove the planks, and no taper blocks for holding the tarp covers in place. The old model used old Victorian red and green dyed satin cotton handkerchiefs, with a doped finish! Stephen.

It would cost more than the whole Clyde Puffer!!..... I might be tempted to make one, but it's to the same standard as the rest of the Puffer and will get a tarpaulin fitted to partially cover the plywood sheet look. The Puffer bow shape annoys me a bit, they got the shape of the hull correct except for the bow which should be vertical on typical puffer hulls. Stephen.

Relco operation depends not on an ultra high voltage, in fact about 40 VAC is the lowest that track cleaning circuits will work with, but Relco does generate higher spikes. My own designed circuits are limited to about 100 VAC, I do not know the upper limit for a Relco, offhand, but I seem to remember testing on a scope with spikes of about 200 VAC peak at very, very low ampage. The air is ionised in the gap, just like in a spark plug in a car, and voltage applied causes a small current to flow, which being AC breaks the insulation properties of the air further and reconnects the current flow. The unit does nothing if the contact is OK, and stops as soon as contact is restored, in milli or micro seconds. The new US HF "cleaning" units work with voltage limitation, and fast clamping of the signal, and do not interfere with the Digital signal to the chip, and should not cause any breakdown in the chip or the board. Note very carefully the bad use of the word cleaning, as I mentioned before the last thing these units do is clean the track!!! They just maintain a circuit, that's all, they do not remove, destroy, vaporise, or teleport the dirt away!!!! The track and wheels must be clean to start with, and the Relco and equivalents maintain contact if the dirt gets in the way, that's all. Stephen.

Shot of the more re-built 1:43rd O scale Clyde Puffer Vital Spark, with extra detailing and rigging, reduced vents, and re-built bridge, with wheel and interior, now painted in more correct colours. Pulleys etc have been added, as well as davit and winch for the anchor lifting. The head looks better now, less like an Aussie dunny! Lettering still to be sourced and final details like the funnel braces to go back on. I am not using it on the Hastings layout, but will be using it on a small O gauge layout later this year. Stephen

Shows layout for main drive, wire in the track groove, with cord to pulleys, one powered by geared motor, scale and size arrangement to suit your layout. With the gearhead motors the drive for rotation is very straightforward, simply replace the main bearing with the motor, and the jib drive is as simple as a pulley drum on the motor shaft in the cabin, mounted again direct on the geared motor shaft, nothing complex at all. Pick motor gearboxes with at least 200:1 or more, even over 1000:1 if available. Some surplus DC motors may be found at shows with these gearboxes fitted. Any DCC decoder could handle the control, or use mechanical switching. Stephen.

I did one of these many years ago, in the 1970's for a display at the London MRC Easter Exhibition. The drive for the whole thing moving involved using a straight quayside track, with one side of the track, (they were double rail like a tram track), having a hidden piano wire laying in the track groove, with the wire end bent up to engage the whole crane. The wire was led along the track groove to one end and was connected via cord to a pulley, (several turns to get grip), and a hanging weight, with the pulley controlled by a slow motion DC gear-head motor. The other end was taken to another pulley at the other end, with a weight to tension the return motion. (The weights were 1 lb bag of sand!). It moved very slowly, at about a foot a minute at minimum. The rotation was done by another gear-head motor, and a further one added for the jib. the control was by 2 rail pick-up from the track, with a RC tone decoder, so the best modern equivalent would be DCC , with two decoders, and a DC drive to the main movement (or another DCC decoder). The track can be basically two rail, you will need metal wheels etc and pickups. The whole crane will need a lot of ballast weight, and a bit of strengthening all round. The weight return system was chosen to eliminate needing tension springs, which a continuous loop of cord drive would need. I found the cord slipped to much with spring and induced drag, which the weights eliminated. Supplier of the motors, (with the highest ratios gearboxes) try: Precision drives , no connection except customer. Gears can be scrap, or inexpensive plastic gears for modellers, several sources. Stephen.