outdoor electric trains NOT battery rf controlled

[boppa]

have an interesting problem

have a online friend who is interested in running basically a `normal' dc train on an outdoors track

he hasn't found anyone who has had much success longterm without going to battery power/rf controlled loco's

he wants to stay with straight dc rail powered (ie store bought) esp as he is thinking a ho scale one that is both in and outdoors (ie a garden loop off from inside to outside)

it occured to me that the biggest problem is bad pickup (a quick google seems to support this) ie dirt and corrosion on the rails

so I took a leaf out of the dcc handbook and thought- what if I upped the voltage to the rails?

what I am thinking ATM is a track line voltage of about 60-90v (this is both safe enough that putting a finger on the track wont `bite' and high enough that light surface dirt/corrosion will not be a problem- I think....)

with a PWM controller that gives an `effective 0-12vdc' supply to the motor

question- if I design such a beast for him- does anyone `here' ie local to me in nth qld, australia- have an outdoor track already set up that could be used as a test bench- and any observations from anyone who has run an outdoor dc supplied setup would also be very appreciated as well from anywhere

[nachoman]

I am a little confused - you are talking HO outdoors? The "G" scale people do it all the time. The heft of the G scale trains apparently resolves many of the electrical issues. For HO, there may be more than just electrical issues. First, it does not take much to derail an HO train. A simple twig that fell across the rails could be a disaster. Second, the plastic ties or rolling stock bodies may not be suitable for outside. I had a small display layout that sat in the summer sunlight for only about an hour. All the turnout ties warped enough that all the turnouts needed replacing, and a locomotive boiler cracked and distorted because of the sun.

[boppa]

correct ho outdoors
it was popular years ago but the electrical problems were the killer (afaik there were little problem with tracks warping etc)

the person I was chatting to had one ages ago but wanted to make it reliable electrically and like the idiot i am, said I would see if I could think up a way of doing it

best part is that if my initial ideas are usable- then on his dc layout although `outside' would have its own `block/controller' no mods would be needed to the loco itself... just isolation blocks between `inside' and `outside' loops

(possibly even dcc locos could be used on the dc emulation mode- IF its not too high a voltage for dcc to handle- havent been able to find that info out yet...)

[nachoman]

When I was a teenager, I had an idea to put NiCad rechargeable batteries in locomotive tenders or dummy diesel units to serve as a backup to propel a train across a dirty section of track. The train would operate as any other train, it's just that the batteries would charge when electrical contact was good, and only provide assistance when the track was dirty. I never tried building anything because I decided it was better to try and keep the tracks clean .

[boppa]

basically what he wants to do is run `massive long trains' like the n scale guys do- but he wants to stay in ho- so garden running is his only option

he has had previous experience in it (back in the 70's mind you- pizzacutter locos etc etc) but wants better reliability (no having to go outside and do the `hand from god' pushstarts on dodgy track)

he said that his previous effort was quite usable with a quick track scrub with a scouring pad in an old track cleaning car but was prone to stalling in places- hence my thoughts about a higher track voltage using pwm to give speed control

[Sumpter250]

HO locomotives, and their circuitry, are designed to operate at no more than 18 volts DC. I'm thinking any significantly higher voltage will result in higher current, and PPHHHITTTTTTTT!.........you let "the smoke out", the loco goes up in flames.

HO outdoor, will require first, a very stable roadbed to lay track on. The subroadbed will have to be weatherproof (homasote is totally out, as is cork). And, finally the track will have to be cleaned, well,( and dried to prevent shorting ) before operation, and "the hand of God push starts", will, pretty much, always be part of the operations.
The larger the outdoor part, the greater the maintenance that will be required. Is it possible ?, absolutely! The drawback will be the required maintenance, and the acceptance of occasional problems. (and that's without any knowledge of the kind of weather your friend normally has.( HO cars don't handle wind all that well )
As for track and structures, a thorough research of G scale products "materials" would be in order. Some plastics do not do well in an "exposed" environment.
I'm not saying "don't do it", but if he does, I wish him luck.

[boppa]

HO locomotives, and their circuitry, are designed to operate at no more than 18 volts DC. I'm thinking any significantly higher voltage will result in higher current, and PPHHHITTTTTTTT!.........you let "the smoke out", the loco goes up in flames.

HO outdoor, will require first, a very stable roadbed to lay track on. The subroadbed will have to be weatherproof (homasote is totally out, as is cork). And, finally the track will have to be cleaned, well,( and dried to prevent shorting ) before operation, and "the hand of God push starts", will, pretty much, always be part of the operations.
The larger the outdoor part, the greater the maintenance that will be required. Is it possible ?, absolutely! The drawback will be the required maintenance, and the acceptance of occasional problems. (and that's without any knowledge of the kind of weather your friend normally has.( HO cars don't handle wind all that well )
As for track and structures, a thorough research of G scale products "materials" would be in order. Some plastics do not do well in an "exposed" environment.
I'm not saying "don't do it", but if he does, I wish him luck.

thats the beauty of using a pwm control system..

it never `sees' a voltage above 12v

but the actual peak voltage can be in the hundreds of volts quite safely

(the trick here is that PWM bit (pulse width modulation)

its fancy blackbox bits that allow much higher supply voltages to be used without higher currents being drawn..

so no smoke escapes!!!

this is a good thing!!

(higher peak voltages also help overcome high resistance track connections as well)

its widely used by almost everyone here (well all the dcc crew anyway)- its how dcc turns the constant 12-20v track voltage into the `slow/med/fast' motor voltages that the loco motor uses...

[boppa]

what pwm is is using a time `slice' of the voltage available

its how light dimmers, variable speed electric drills and even dcc speed control works

most things have inertia- electric light bulbs actually turn on and off 50 (or 60) times a second depending on if you are here or in the usa (commonly put on electrical equipement as 50 or 60 Hz)

do they look like they are turning on 50/60 times a second- no- they `look' like they are always on- thermal inertia in the filiment..

as an example light dimmers say..
turn it to 1/2 and the bulb gets half as bright
but modern dimmers (triacs) dont actually cut the voltage to half
what they do is apply the full voltage- but only for half as long on each cycle
it still gets the full voltage though

(its how dcc does speed control- it turns the track voltage on and off really quickly to the loco motor- if its always on in (as an example) 1 sec- then its full speed
if its on for 1/2 a second out of every second- thats 1/2 speed
etc etc
now do that tens/hundredsthousands of times a second and even though the motor is being turned on and off- its mechanical inertia makes it run- at full, half, quarter speed....

what I am thinking of doing is making the track voltage much higher
but using switching (magic black box bit) that only lets an `average' of 12v to the track- so the loco runs as it would on pure dc
( so instead of 0 to 100% time turned on, it would be 0 to say 5% time turned on- but that 5% of the time would be 12v...)
but the peak voltage would be 60-90- whatever volts- which would basically `punch through' dirt/corrosion etc

its a well tried and true technique- as far as I know tho it hasn't been used for model r.r before (at least not in the way I am thinking of using it)

[jim currie]

had a friend several years ago (he died in 95) that had a large HO outside layout but his was the Great Nothrern electrical division (live overhead) and as i rember he had very few issues with it.
jim

[Bob C]

OK, guys - set me straight on this -IIRC, pwm has been around in MRing since the days of the Commodore 64 and Bruce Chubb's original CMRI. Seems to me that "Transistor Throttles" for DC had a feature called "Pulse-Power", or some such, that used PWM to permit/promote slow speed operation with the old-tech motors by "showing" them a constant 12-14 volts max voltage variable duration pulse DC. While the result was fine slow speed performance, it made the motors noisy and caused excess heating. The controller circuits were then modified to "superimpose" the pulses on a variable DC base voltage, dialing the pulse out as the base voltage (speed control voltage) increased. This mitigated the problems, and the feature was (I think) fairly common in fancier throttles. Around that time also, think I remember a "Crud-Cutter" circuit with very high frequency AC added to the DC - CRS what voltage - to overcome rail oxidation/dirt...but it could not be used with GE's ASTRAC or(then new) DCC. Not saying it won't work, but there may be trouble fitting stuff that will handle these voltage/power levels into HO equipment, as well as the insulation issues for the powered units and operational short circuits (outdoors is an 'unclean" environment), which can quickly create small blobs of plastic and solder. Wish I had all my "used to have" issues of MR, RMC and others to nail this stuff down - but I don't , and won't bore you all with "Why?" ...and yeah, I'm THAT old ! :o Bob C.

[boppa]

I know the controlers you are describing (I actually had a vic20 controlling my layout back in the early 80's- it was the predesessor to the c64- 3 1/2 whole k of ram!!)

most of the overheating and noisyness was due to the low switching frequencies then in use(often mains frequency lock ie 50 or 60 hz), these days they tend to run into the 10's of khz

`pulse power' controllers were even worse- they when on `pulse power' were basically going from fullwave rectification to 1/2 wave rectification for the dc - which meant the pulses were now 1/2 mains frequency (i.e 25 or 30 hz)

what I am thinking of doing is basically the same as the `motor driving circuit' rom a dcc controller, so the pwm concept is well proven (how many dcc locos are out there now???) ;-)
the difference is the peak voltage would be much higher- but for microseconds only, and the average voltage seen by the motor remains at the usual 0-12v as seen by a normal dc motor by limiting to duty cycle from 0% to say 10% being the 0-12v range.
for safetys sake(in case the switching circuit failed for some reason and applied a 100% duty cycle to the rails), a simple zener based crowbar circuit would save the loco engine, lights etc from letting the magic smoke out...

(edit to add- note that pulse power mode on those throttles is not pwm- totally different animal altogether)

[Sumpter250]

OK, PWM didn't register the first time I read it.( insert forehead slap smilie ) I read PWM controller, as a "brand name".
Pulse Width Modulation! Or, as it is sometimes called, Duty Cycle control, the length of the on time of the pulse determines the overall current. That would, at the frequencies you mention, provide safe higher voltage operation. The resistance of dust, dirt, or corrosion would be less of a factor. What drives the motor is average power (V-avg X I-avg).

[andersley]

Fascinating stuff (if way over my head!)

Just to say that many years ago I had a quite entensive O scale layout around the garden, using pure no-frills DC, and it ran fine after a quick clean and check for twigs, beetles, etc. on the tracks. But my brass handbuilt O scale locos had quite a bit of mass to help with current collection, so not sure of just how successful HO would be - multiple loco lash-ups would help of course. But windy days would preclude running, I think. hock:

The higher voltage certainly does seem to be the way to go - I hope you go ahead with trials.

[Russ Bellinis]

I know nothing about PWM, but I think the biggest challenge would be trying to operate relatively small and there fore light weight ho scale equipment with rp 25 wheel flanges. In the absence of wind, I think you would still need code 100 track and "pizza cutter" wheels to keep the trains from derailing.

[boppa]

update
made a pwm dc controller that uses 90v peak voltage with a 0-12v `driving range'

had a length of flextrack exposed (heavily) to weather (salt spray for several hours on the beach then a week outside without being cleaned in any way)

the pwm controller could drive a cheap hornby 040 loco back and forth over most of the track with only the `occasional' finger from god required

my ancient old (1980's) controller with pulse power (1/2 wave rectification) could make some progress only at full power and pulsepower on and required frequent pushing

pulse power off was no movement apart from the ocassional `burp' as it was pushed along

dcc wasn't tried as I have no dcc controller or dcc locos


still waiting for answers to emails sent to various ddc makers as to peak voltages their decoders will stand (I doubt any dcc controller could handle these peak voltages without mods tho)

I can't see any reason that garden running couldn't be feasible, trackwork would have to be up to par (but then I cant see why you couldnt use oversized track for reliablity)- 100kmh winds might be a problem but then why would you run outside in such conditions??)


it certainly opens back up both dc, and long haul ho loco strings