Beer and Buckjumpers

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Flymo748
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Beer and Buckjumpers - lessons in CSBs

Postby Flymo748 » Mon Nov 12, 2012 9:43 pm

Lessons in the use of Continuous Springy Beams #17

When you load your tram locomotive up with lead sheet, so that it now rides too low...

Although it's easy with CSB's to pull one out and replace it with a stiffer one, it helps if you make a note of what gauge wire you originally put in it!

I *think* that it was 11 gauge, and I'm going to try it again with 13 gauge :-)

Flymo
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Chris Mitton
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Re: Beer and Buckjumpers - lessons in CSBs

Postby Chris Mitton » Mon Nov 12, 2012 10:07 pm

Flymo748 wrote:Lessons in the use of Continuous Springy Beams #17
Although it's easy with CSB's to pull one out and replace it with a stiffer one, it helps if you make a note of what gauge wire you originally put in it!
Flymo


.....and it helps the ride quality if you replace the other one while you're at it! http://www.scalefour.org/forum/posting.php?mode=quote&f=9&t=425&p=19840#

Seriously, useful tip for IT buffs - if like me you use Alan Turner's Excel spreadsheet to do the sums, when you've got a set of measurements you're happy with, copy the whole sheet to another tab and rename it to "exGER E4 2-4-0" or whatever, then you've a record of planned dimensions and weights for your entire stock, to refer to when you've built it and are tweaking your chassis.

Hope this is helpful,
Regards
Chris

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Re: Beer and Buckjumpers

Postby Chris Mitton » Mon Nov 12, 2012 10:12 pm

OK, so I haven't got the hang of these smilies yet....
Chris

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Flymo748
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Re: Beer and Buckjumpers - lessons in CSBs

Postby Flymo748 » Mon Nov 12, 2012 10:22 pm

Chris Mitton wrote:
Flymo748 wrote:Lessons in the use of Continuous Springy Beams #17
Although it's easy with CSB's to pull one out and replace it with a stiffer one, it helps if you make a note of what gauge wire you originally put in it!
Flymo


.....and it helps the ride quality if you replace the other one while you're at it!


Both now done, and it's made a change to the ride height. Not enough, and I'll pack the body up slightly with a couple of spacing washers. That's both to bring the buffer height up to normal, but more importantly to make sure that the skirts don't catch when going over turnouts.

The whole ensemble weighs 120 grams now (or four ounces in old money) so I've decided to stop packing in lead, even though there is room for plenty more, and see how it rides.

Flymo
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Will L
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Re: Beer and Buckjumpers

Postby Will L » Mon Nov 12, 2012 11:18 pm

Alternative you can feed the known weight and fulcrum points back into any of the spreadsheets and see what wire size give you the nearest to 0.5mm deflection.

Will

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Beer and Buckjumpers - Fully chipped...

Postby Flymo748 » Wed Nov 14, 2012 7:05 am

And after deciding that it was simply not possible for the "interchangeable" DCC chip set-up to fit inside my tram engine, this is how it ended up:

Chips v2 002.jpg


The chip is simply sitting on top of the motor, held in place with a small layer of blu-tack. Who said that solutions needed to be over-engineered?

I've set up a "programming track" and successfully driven the locomotive back and forth. I haven't attempted to read or to program any of the CV values yet, as I want to get it running on a slightly longer piece of track to see what the ZTC unit does with the default values on the chip.

However I am mildly pleased that it all worked first time. Thanks to everyone for the advice on chips and DCC in general.

Cheers
Flymo
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Paul Townsend
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Re: Beer and Buckjumpers - Fully chipped...

Postby Paul Townsend » Wed Nov 14, 2012 5:15 pm

Flymo748 wrote:And after deciding that it was simply not possible for the "interchangeable" DCC chip set-up to fit inside my tram engine, this is how it ended up:

Chips v2 002.jpg


The chip is simply sitting on top of the motor, held in place with a small layer of blu-tack. Who said that solutions needed to be over-engineered?

Flymo


Or Under-engineered :)

You should be Ok in a tram which presumably doesn't work hard.
However if the same solution was applied in say a hard working tiny shunter, motor temperature could overheat your decoder and destroy it. In such a loco you would need better thermal separation of motor and decoder. Even a layer of thin Ds PCB would help with DS sticky tape or bath caulk both sides. Also some extra heat-sinking metal attached to the motor shell can help.

I had bad experience of this some years ago and measured the motor case temperature at near 150degrees C. after 30 mins shunting. With the extra temp. rise in the decoder itself, that would have fried it.

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Tim V
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Re: Beer and Buckjumpers

Postby Tim V » Wed Nov 14, 2012 5:27 pm

150 degrees? Are you kidding?

I think that loco needs a serious looking at. Probably high resistance from gears/pickups/axles. Or poor motor.

The motors in my locos do not get warmer than can be held by hand.
Tim V
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Mark Tatlow
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Re: Beer and Buckjumpers

Postby Mark Tatlow » Thu Nov 15, 2012 12:58 pm

Tim V wrote:150 degrees? Are you kidding?


And surely it was at the point of unsoldering itself.

I am reminded of the teasing I had last night when I explained that when a wheel caused a short circuit on the layout, it led to the plastic of the Gibson wheel melting and consequently starting to smell. A little alarmed, I tried to find where from the loco the smell was coming from by holding it to my nose.

I had a burn on the tip of my nose as a consequence to prove that I found what the problem was...........
Mark Tatlow

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Re: Beer and Buckjumpers

Postby Philip Hall » Thu Nov 15, 2012 3:02 pm

If a short can cause a wheel to get that hot and melt the centre, it makes me very glad I've not gone DCC!

Philip

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Re: Beer and Buckjumpers

Postby martin goodall » Thu Nov 15, 2012 4:01 pm

Philip Hall wrote:If a short can cause a wheel to get that hot and melt the centre, it makes me very glad I've not gone DCC!

Philip


This is one more reason why I would never adopt DCC. (There are plenty of other reasons!)

But radio-contolled on-board batteries are an entirely different proposition, and could well be The Future. Small enough batteries are now becoming available (by courtesy of the manufacturers of mobile phones) and it is just a queston of waiting to see if the control systems that are being developed will prove to be reliable and user-friendly. I think the jury may still be out on that one for a while yet.

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Re: Beer and Buckjumpers

Postby nigelcliffe » Thu Nov 15, 2012 4:18 pm

Philip Hall wrote:If a short can cause a wheel to get that hot and melt the centre, it makes me very glad I've not gone DCC!

Philip


If a short does not cause the command station to shut down, and thus remove all current from the track, then the layout is badly wired.

If people persist in supplying layouts with high current command stations, without any moderation of the maximum current in a given section of track, then the layout is not wired in a defensive manner.

The problem could be avoided with good wiring practises and appropriate current limits to sub-areas within the layout.



martin goodall wrote:But radio-contolled on-board batteries are an entirely different proposition,


There were a lot of laptop batteries recalled a couple of years ago due to them catching fire. You didn't have to do anything to make them burn, just have the misfortune to own one.

A short circuit inside the loco will cause high currents to flow unless current limiters are fitted to the battery, and the short circuit occurs after the current limiting circuit.



No solution, other than perhaps push-along, is completely "safe".



- Nigel

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Tim V
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Re: Beer and Buckjumpers

Postby Tim V » Thu Nov 15, 2012 5:10 pm

I was concerned at the use of a PP3 battery in that article in MRJ. 9V 300mah on short will produce a lot of current, enough to cause a fire.

As Nigel says, proper use of current limiters is the way forward, it's called the coin test in DCC. If putting a coin across the tracks does not cause the controller to shut down, you've got a serious problem.
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Re: Beer and Buckjumpers

Postby Armchair Modeller » Thu Nov 15, 2012 6:46 pm

Philip Hall wrote:If a short can cause a wheel to get that hot and melt the centre, it makes me very glad I've not gone DCC!

Philip


Rest assured, it can happen with DC too. I once parked a loco so that its leading wheels just bridged the gap between 2 sections. We only noticed when the smoke and smell of burning plastic alerted us to the situation...... :o

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Re: Beer and Buckjumpers

Postby Paul Townsend » Fri Nov 16, 2012 9:33 am

Tim V wrote:150 degrees? Are you kidding?

I think that loco needs a serious looking at. Probably high resistance from gears/pickups/axles. Or poor motor.

The motors in my locos do not get warmer than can be held by hand.


The hot loco was not mine, just a visitor with a funny smell....the paintwork was discoloured too! There were other problems which led to taking the body of and the temperature measurement. This was pre-Highbridge going DCC so fortunately it was a dc loco so no decoder frying but it was only drawing 600ma which is less than Tim's current visitor to Highbridge! My point is that the approx. 6watts generated had nowhere to go in a tiny body so motor temperature gradually rose in the running session.

Agreed that a modern motor rig doesn't usually get hot but I still see the need for a word of warning re combining the temperature rise of motor and decoder and recommend thermal separation when possible. Not all small locos will be as efficient as the best or as lightly loaded as Flymo's tram.

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Re: Beer and Buckjumpers

Postby Paul Townsend » Fri Nov 16, 2012 9:40 am

Tim V wrote:I was concerned at the use of a PP3 battery in that article in MRJ. 9V 300mah on short will produce a lot of current, enough to cause a fire.



Fortunately the PP3 batteries have a higher internal resistance than single cell Nicads ( which CA produce huge currents).

Even so the electronics need to have some form of current trip or limiting.
Bottom line is a 125, 250mA or 500ma fuse...available in sizes of c. 6mm long 2mm dia. wire-ended tube at about £1 a go. My Escap motored locos always had one fitted in their DC form.

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Re: Beer and Buckjumpers

Postby martin goodall » Fri Nov 16, 2012 11:33 am

After reading the last few comments, perhaps we ought to go back to clockwork! :mrgreen:

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Re: Beer and Buckjumpers

Postby nigelcliffe » Fri Nov 16, 2012 1:04 pm

martin goodall wrote:After reading the last few comments, perhaps we ought to go back to clockwork! :mrgreen:


Trapped fingers in gears with spring still driving forwards, springs flying out cutting things... no thanks.

Hence my comment about push-along.

- Nigel

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Re: Beer and Buckjumpers

Postby Flymo748 » Fri Nov 16, 2012 1:27 pm

nigelcliffe wrote:If a short does not cause the command station to shut down, and thus remove all current from the track, then the layout is badly wired.

If people persist in supplying layouts with high current command stations, without any moderation of the maximum current in a given section of track, then the layout is not wired in a defensive manner.

The problem could be avoided with good wiring practises and appropriate current limits to sub-areas within the layout.

Hi Nigel,

As I'll soon be wiring some track for DCC, what words of experience can you share with us about good and bad practice in supplying track?

I did think that DCC controllers came with cut-offs that shut down the power in the event of a short. There seem to be enough warnings made about the problems caused by a short circuit stopping all activity on an entire layout that I'm surprised something like this could happen.

Cheers
Flymo
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nigelcliffe
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Re: Beer and Buckjumpers

Postby nigelcliffe » Fri Nov 16, 2012 2:18 pm

Flymo748 wrote:
nigelcliffe wrote:If a short does not cause the command station to shut down, and thus remove all current from the track, then the layout is badly wired.

If people persist in supplying layouts with high current command stations, without any moderation of the maximum current in a given section of track, then the layout is not wired in a defensive manner.

The problem could be avoided with good wiring practises and appropriate current limits to sub-areas within the layout.

Hi Nigel,

As I'll soon be wiring some track for DCC, what words of experience can you share with us about good and bad practice in supplying track?

I did think that DCC controllers came with cut-offs that shut down the power in the event of a short. There seem to be enough warnings made about the problems caused by a short circuit stopping all activity on an entire layout that I'm surprised something like this could happen.

Cheers
Flymo


You could try the backnumbers of Snooze where Mick Moignard wrote an extensive series of articles on DCC. I expect Mick will be at Warley show on the Sunningwell Command & Control stand (a DCC supplier from the Oxford area).


The biggest problem comes if the command station doesn't shut down in the event of a short. This is checked with the "coin" test. Put a coin across the track to create a short circuit (and try everywhere, not just one place). If the command station (or power-district cut-out) doesn't shut down, your wiring is poor and needs fixing.
The failure to shut-down comes because there is too much resistance in the wires, so rather than >5A flowing (in a 5A rated system), about 4.5A flows. The command station cannot tell the difference between running two dozen trains and a short drawing 4.5A, so supplies the current. 4.5A at 14v is 63Watts, a lot more than my soldering iron !
The failure of the coin test is usually because a piece of thin wire has been used, or a weak solder joint. For everything other than the shortest bits of connection, use decently thick wire for the main track power "bus" around the layout. Very short pieces of thin wire are generally fine (eg. to track dropper wires), their resistance won't be significant. Andrew Crosland (designer of the Sprog DCC programmer) did some calculations on the use of copper foil as layout wiring; the resistance of the foil was too high to be used as the main bus wiring, though it may be useful in shorter lengths for local power distribution.


Next biggest comes from the way some command stations shut down and reset. Quite a few will try to reconnect power automatically. They do this by pulsing power at the layout to see if it is cleared. Not much of a way around that.


Finally, lowering the current cut-out threshold.
I think it is wise to divide anything but the simplest layout into electrical sub-sections. These can be disconnected for fault finding. One or more sub-sections could be combined into a "power district" (to use the US term which will be found in many documents). You can have as many power districts as you like. The power district is protected by its own cut-out device, set to the lowest current you can, consistent with being able to run your trains. For almost everything in 4mm scale, that's well below 1.5A for one or two locos moving within a power district. A small layout might have a single power district.
Commercial electronic power district cut-out devices are available from firms such as DCC Specialities who make the PowerShield range which have a good reputation and can be set to various current levels. MERG have a design for one, but I don't think it has reached production as a kit yet. Some people report using commercial resettable fuse devices, I'm not sure whether these are truely effective.
A different approach is current-limiting devices, rather than cut-out. The cheapest of these is a 21W car indicator bulb in series with one of the track feed wires. If the layout is wired into power districts, the bulb can act as a current limiter for a single power district (so several bulbs for several districts). The bulb will illuminate at about 1.8A of current, and limit the current at this level, so a short beyond the bulb is limited to that power, and will never shut down a command station with a higher current rating. The things to remember with lightbulbs is that they are working as a current limiter - THE CURRENT IS STILL FLOWING !!, though the voltage after the illuminated bulb is fairly low. And, a 21W car bulb can get hot, so put it in a proper bulb holder in a ventillated place, not under the scenery where it's a fire risk !
Using current-limiting light bulbs is a contraversial topic on various DCC forums. On the whole, I wouldn't use them, and would go for cut-out devices. I did fit bulbs for someone who was having problems with their DCC system re-setting in a user-hostile manner if the command station detected a short.


- Nigel

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dcockling
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Re: Beer and Buckjumpers

Postby dcockling » Fri Nov 16, 2012 3:24 pm

nigelcliffe wrote:You could try the backnumbers of Snooze where Mick Moignard wrote an extensive series of articles on DCC. I expect Mick will be at Warley show on the Sunningwell Command & Control stand (a DCC supplier from the Oxford area).


Updated version of the Original Scalefour News Articles

All the Best
Danny

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Tim V
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Re: Beer and Buckjumpers

Postby Tim V » Fri Nov 16, 2012 4:20 pm

nigelcliffe wrote:
martin goodall wrote:Hence my comment about push-along.

- Nigel

There was a great Youtube video of that subject called "5 digit control" (from memory), it even had sound. Just searched but couldn't find it.
Tim V
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martin goodall
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Re: Beer and Buckjumpers

Postby martin goodall » Fri Nov 16, 2012 10:04 pm

I've just had an even better idea - static dioramas :twisted:

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Paul Townsend
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Re: Beer and Buckjumpers

Postby Paul Townsend » Sat Nov 17, 2012 10:11 am

Flymo748 wrote:Hi Nigel,

As I'll soon be wiring some track for DCC, what words of experience can you share with us about good and bad practice in supplying track?

I did think that DCC controllers came with cut-offs that shut down the power in the event of a short. There seem to be enough warnings made about the problems caused by a short circuit stopping all activity on an entire layout that I'm surprised something like this could happen.

Cheers
Flymo


I agree with everything Nigel said but add:

Look at
http://www.wiringfordcc.com/switches.htm

for an excellent set of advice, highly respected throughout the DCC community. Slight snag is the use of American wire sizes, but Google is your friend and can provide a conversion table to UK and metric wires.

When I converted Highbridge from dc to DCC last year this was my guide and overcame many concerns raised by others about thin wire as found in old dc MR.
Wiring a new layout is easier than converting but this guide will help, as do Nigel's notes.

I strongly recommend having a few power districts and the Merg DC06 cut-outs, PM me if you want more info or join Merg! Also for fault finding the existence of old dc type section switches is a boon....easier for a converted model than for new. My next layout will include a few of these merely for debugging.....they don't have to be on the main control panel and can just be local to a baseboard.

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Flymo748
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Beer and Buckjumpers - Making contact

Postby Flymo748 » Thu Dec 13, 2012 8:01 am

It's been a couple of weeks since I last posted anything, or indeed had chance to do any modelling. However when I was on the Scalefour Society stand at Warley (and thank you to all the current and new members that took the time to say hello and chat) I had my little Pug running up and down on a metre of plain track - just for something to do. Whilst it ran well, it could have run better. It stuttered occasionally at low speed...

So when I was back at home and had the chance to wield some wire and a soldering iron, I made and fitted an extra set of pick-ups:

Extra pickups 001.jpg


You should be able to see that the forward wheel now has pickups both front and rear. The outboard ones are the new ones, and they slide between the bottom of the frames and the brake rodding. The white rectangle behind them is a small piece of cartridge paper that is epoxied in place. The purpose is to prevent an accidental short against the frame.

Buoyed by the success of this, I went on immediately to put and extra set on the tram locomotive:

Extra pickups 003.jpg


I haven't had chance to perform a test run of either of them yet, although I may just get time to do so this weekend.

Flymo
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