I want to experiment with resistor wheel sets for 009 (for whole train block occupancy detection), and assume I'll end up with something from the world of N gauge. Alternatively, if necessary, I could add resisters to wheel sets with metal wheels. Does anybody have experience or advice?
I am not really sure what you are trying to do here. Is this for DC or DCC?
If the answer is DCC then it is very simple in that you do not need to do anything at all. You can use one of the occupancy detection modules available as they work by detecting power usage through the loco. You just need to set up relevant track breaks to make the blocks work.
Tom,
Yes, it has been done. I would not say it is common but then it is not unusual either. There have been discussions and experiments in MERG (Model Electronic Railway Group).
There are a number of possibilities:
1. situations such as coach lighting through pickups provide it
2. similarly, pickups on a brake van to power the tail light provide tail end protection
3. a tiny SMD (Surface Mount Device) axle-mounted resistor soldered across the wheels has a similar effect
4. as does painting across the wheel insulator with resistive paint.
It depends how sensitive the track circuit detector is, but about 10 K (ohms) is a fair compromise, though it depends whether whole train or just tail end protection is needed. My experience is with DC only. Some DCC track circuit detectors may not be sensitive enough, though if they can detect a locomotive that is stationary with no "functions" activated they should be. The resistance of individual axles is a compromise between the detectability of an individual piece of stock and the total parallel resistance and power load of many pieces of stock.
It has been a while since I looked at it, "solder paint", paint-on solder or silver (real, not silver coloured) paint is much improved so 3 is likely to be easier and more reliable than it used to.
I experimented a little bit with 4. Much black paint is slightly conductive. With many coats of black acrylic I was able to get 30 K to 50 K but I was not convinced that it would consistent and reliable enough, as well as it taking a lot of time.
I've since discovered that the control pockets in some electric guitars are lined with what looks like graphite paint instead of the more usual copper foil so it might be worth re-investigating if a source can be found. (It is possible to make very effective resistors with an ordinary soft lead pencil on paper. I used to do a schools electronics workshop using the principle, where the resistors controlled the frequency/pitch of an audio oscillator - the longer the line, the higher the resistance, the fatter or darker the line, the lower the resistance.)
It is simpler if there is always a brake van at the end of the train as tail end track circuiting will detect a broken train and when the whole train is inside a block section. If there is not then it means wiring all stock, though fixed rakes of (say) skips or slate wagons only need the end vehicles to be adapted.
Thank you Jim and Graeme,
Sorry, I should have specified that this is for DCC and that the goal is to have whole-train occupancy detection. I am interested in sorting out full automation (to be switched off whenever I want, of course) and I'll want every wagon or coach (because I will also shunt a lot) to have resisters (except inner axles on bogies) so I can know when every block is cleared.
Er, I am in Afghanistan at the moment and the nearest actual model railway rolling stock is probably a thousand km away. For that matter, the nearest real rolling stock is hundreds of km away. I'll receive my Hattons order in a few months. This is all preamble to the question - are most rolling stock wheels conductive? I had thought they might not be, meaning that surface mount devices wouldn't do. But if they are, Jim's 3rd and 4th solutions look spot-on.
Tom
have a look at http://www.southdownsrailway.org.uk/index.php/rolling-stock3/wheelsets/19-resistor-wheelsets some pertinent stuff there.
Andy
The ease with which you can attach SMD resistors will depend on the wheel type as you indicate. Clearly it is a lot easier in OO than in N or 009. If the wheels are the solid metal type where one wheel is insulated from the axle by a smallish plastic cuff then a resistor of a suitable length can be "propped up" and glued at 45-ish degrees over the cuff with one conductive end against the inside of the wheel and the other end against the axle. Then the ends can be "cold soldered" to wheel and axle with conductive paint.
It will be a lot harder with (e.g. Parkside Dundas) wheels which have much larger plastic inserts on both wheels giving wheel spoke detail between metal tyre and axle. It may be easier to use metal wire wiper/pickups on the back of the wheel and mount the resistor on the chassis.
I understand the quiescent current for DCC decoders is generally about 10 mA, so 10 K should be about right.
Excellent information!
What kind of wheels do the Peco 009 ready to run coaches and wagons have?
I have now determined that Peco ready-to-run 009 stock has plastic wheels. I am planning to buy metal alternatives for my resister experiments. As my wagons (and my micrometer) have not yet reached me here in Kabul, please could some kind soul tell me the Peco stock wheel diameter? I will put my trust in the Gods for the axle length, back-to-back etc. but need to know what diameter to order.
Tom,
I've put the calipers on some Peco nylon-type 009 wheelsets, and the wheel diameter is coming out at 6mm. By the way, you may have picked a bad time to be converting to metal wheelsets, as I am informed the trade are having a hard time getting supplies, with traditional manufacturers closing-shop. The manufacturers of the actual wheels tend to be all about the same age, and retiring about the same time. I understand this is one reason why Parkside Dundas are not selling their Irish wagon kits right now - shortage of wheelsets. Probably best to lay-in a stock while you can. Its an ageing hobby - just look at the photos of the 009 events.
Kindest,
Andrew
Thanks so much, Andrew!
I'm not very much of a spring chicken myself, even if I am still only pondering my first layout.
Tom,
Some additinal info to keep you occupied while you wait for Space-A out, or whatever. Attached is photo of the Peco 6mm wheelsets, nylon-plastic type, part number NR-100 >>>
Tom,
And the Peco 6mm nylon-plastic spoked version, part number NR-101. I know what it's like to be at the far end of a long line of supply and communication. I started collecting the Peco wagonsin Gabon, Africa.
Photo below >>>
Tom,
Plus, Andrew Hastie of Parksdie Dundas does some nice metal wheelsets which may be right for you:
http://www.parksidedundas.co.uk/acatalog/N_G_WHEELS.html
He has some 6.2mm wheelsets, part number PN58, but I do not know if they will drop-in for Peco wheelsets.
If I have any in my workshop, I'll try and take a bad picture of those too. May even try them on a Peco L&BR van and let you know. It's boiling hot in my workshop here tonight - hope it is cooler where you are.
Kindest,
Andrew
I replace peco wheels with Farish wheels which are 6.2mm but I have to just run a file over the pin point
I have just taken my digital calipers to some wheelsets -
The Parkside Dundas ones I have are just under 15 mm, point to point. (14.95 mm, 14.97 mm etc, but it is hard say if I have the axles parallel to the calipers.)
The Peco ones are about 14.8 -ish mm.
Effectively the same, but being moulded nylon the needle points are not as sharp.
I must admit that rather than take the tip off the needle points as Mozzer does, on the one or two PD kits I assembled that were a "bit tight" I just gave the axle boxes a little squeeze to impress the sharp axle ends into them.
Something to bear in mind is that the PD wheels have metal tyres and the wheel is a plastic insert.
I was kindly given a pair of Farish wheelsets by another modeller to try. They are slightly longer at about 15.2 mm but went into a Peco RTR wagon. The needle looks a little more "pointy" than on the PD wheels. However they have solid metal wheels with just a slim insulating cuff or muff (both wheels), perhaps just 0.5 mm thick and certainly under 1 mm. I think this would make them easier to add a resistor to.
Edit: thinking again, if the resistor is the right length, it might be possible to lay it flat against the plastic wheel disc on the PD wheels, but there is not much thickness in the metal tyre so you would need to be careful of fouling check rails etc.
Thank you all!
I now have two sorts of wheels on order and I'm now investigating resistors and conductive paint, as well as resistant paint. If I also get my multimeter and ceremonial First Wagon in September I will begin my experiments and continue my dreaming. But my Digitrax equipment, not to mention my SetTrack 'train set' will only arrive in December. Layout construction is not expected until 2018, very sadly.
I use conductive glue (Wire Glue) with SMD resistors glued at 45 degrees between the back of the wheel and the axle.
The circuit is completed by "painting" the glue with a pin from the resistor along the axle to the other wheel.
In order to get a good circuit, you need to clean the wheels on the axle(s) with the resistors. I fit one axle with resistors on a 4 wheeled vehicle, two axles on bogie vehicles.
The advantage of all this (for non students of DCC) is that it improves "track circuit" detection for a train. A locomotive, while detected. may not carry its signature due to dirty wheels or track.
Hope this helps
Tony
My first Peco two wagons, my replacement Graham Farish metal wheelsets, and some bits of SetTrack have finally met up here in Afghanistan. I didn't really know whether to believe the wheelsets would fit but they did like a dream - and they roll much better than the original Peco wheels! Once I re-wheeled the first wagon I compared how far each wagon would roll down my re-railer and along some track. The wagon with the Graham Farish wheels consistently rolled more than twice as far. (And when I re-wheeled the other wagon it did just as well.)
Next experiment: Adding resisters and conductive paint to the wheelsets to eventually enable occupancy detection. (Not that I yet have anything to occupy.)