I'm looking at several truck products with electrical pickup by Micromark. They apparently work by means of thin metal "wipers" that ride against the axles. Unless they are sprung pretty tightly I cannot see how these don't fail pretty quickly -- like they would stop making good contact and then your caboose lights would be blinking like mad every time it passed over a turnout. And if they are sprung tightly enough to stay in contact, wouldn't they impede rolling (or increase drag coefficient or whatever)?
Anyone have any empirical data about this?
Thanks,
-Matt
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
I have made a couple of these, using simple loops of stranded wire wrapped around the axles. They work OK. With stranded wire, there can be multiple current paths. The axle connection has the lessor motion vs. wheel wipers, so less friction.
A bit of electronics inside can help. A simple diode bridge and a capacitor can smooth out current fluctuations and deliver DC rather than the AC-like DCC signal.
It takes an iron man to play with a toy iron horse.
I have a few tenders that have these. They work well, but they tend to accumulate dirt/corroded material. A gentle cleaning is required from time to time to ensure good contact.
Simon
MisterBeasleyA simple diode bridge and a capacitor can smooth out current
It always sounds so easy. I have only just gotten used to the idea of using resistors, and now capacitors and diode bridges? Does a diode bridge get me into the multiverse?
Seriously, though, thanks for the hint.
Hi Matt,
I have used several types of power pick up wipers. Logically, the best pickups will gather power from all wheels. Axle wipers only gather power from the wheels on one side of the truck, but that doesn't mean that they don't work. However, they are best used with some sort of keep alive system as was mentioned in a previous post.
Here are some home made wheel wipers using 0.005" brass sheet. The brass is simply cut into a 'T' shape and drilled to accommodate a brass bolt and nut. It takes a bit of adjustment to get the contact pressure right without causing too much rolling resistance but that is not difficult:
Here is another home made method using phosphor bronze wire from Tichy Trains. The wires shown are actually too thick so they were hard to adjust. Something like 0.0125" wire would work well:
Here is another home built wheel wiper system. In this case the phosphor bronze wires wipe the backs of the wheels. By the way, the whole truck was scratchbuilt for my McKeen Motor Car project:
Another phosphor bronze wire pickup. This one is on the drive system for an HOn30 industrial mule:
Here is the mule awaiting yellow paint:
Another Phosphor bronze pick up system:
I have made a few axle wiper contacts in the past but apparently I didn't take any pictures of them. As I said, they do work but a keep alive system is strongly recommended. In fact, I would recommend a keep alive system for any illuminated car.
This is one type that I don't recommend. They are from Streamlined Backshop. I used them on my fleet of cabooses and I found the rolling resistance to be pretty strong. They are probably okay if you are only using them on one car in the train, but I certainly wouldn't use them on a fleet of passenger cars:
In case I haven't given you the link to Tichy for their phosphor bronze wire, here it is. I can't recommend it strongly enough! It is far superior to brass. I keep all sizes on hand:
https://www.tichytraingroup.com/Shop/tabid/91/c/ho_wire/Default.aspx
Cheers!!
Dave
I'm just a dude with a bad back having a lot of fun with model trains, and finally building a layout!
Hello All,
Yes, I have tried the trucks and wipers you are describing on a tender to try and increase the reliability of an HO USRA 0-6-0 over unpowered frogs.
When I "tested" the trucks- -unpowered- -on the tender, the resistance (drag) produced was unacceptable versus the benefits of adding tender pickup.
To get the "best" contact, the wipers are put under the axles. The spring tension then pushes the wipers up against the axles.
Creating both reliable electrical contact and significant drag.
To decrease the drag the wipers can be pushed down on top of the axles but over time I could understand how they could lose their spring tension and become unreliable.
For me, the high drag factor was too much.
D.I.Y. or axle/side frame contacts (Athern BB type) would be my choice if I chose to "electrify" this tender in future.
Hope this helps.
"Uhh...I didn’t know it was 'impossible' I just made it work...sorry"
the wipers that go onto the axle work -kinda- okay ... what works somewhat better are the wipers that go onto the back of the [smooth] wheel .. even better are the wipers that go onto the top of the tread surface ...
however in each case of -better- contact you can run the risk of increased drag on the wheel itself ..
I have heard of modelers using a kadee flat centering spring for electrical pickups
Terry
Inspired by Addiction
See more on my YouTube Channel
I've occasionally used axle wipers on tenders, but much prefer wheel wipers on steam locomotives drivers.
A couple photos....
Wayne
Gosh, thanks everyone for the discussion. My thought was about lighting cabooses and maybe passenger cars, but there's a whole raft of good info here about getting locos to run better.
crossthedogMy thought was about lighting cabooses and maybe passenger cars.
For lighting my string of Rivarossi Heavyweight passenger cars I added jumpers from one car to the next so all the cars form a parallel electrical circuit with one another. It was easier than adding more wipers, and all flickering is gone.
-Kevin
Living the dream.
MisterBeasleyA simple diode bridge and a capacitor can smooth out current fluctuations and deliver DC rather than the AC-like DCC signal.
are capacitors needed for lighting circuits?
while the DCC waveform is AC, the voltage is constant with either polarity. a bridge should result in a constant voltage, possibly with very short negative (zero) spikes when the DCC polarity reverses
greg - Philadelphia & Reading / Reading
gregcare capacitors needed for lighting circuits?
Hi Greg,
Installing capacitors in your car lighting systems will pretty much eliminate any fllickering because of dirty or uneven track, or dirty wheels.
The circuits are simple to build. If you want to be able to turn the lights off then you can use a micro slide switch or a locking magnetic reed switch.
If you want a circuit diagram, let me know and I can post one.
hon30crittercapacitors in your car lighting systems will pretty much eliminate any fllickering because of dirty or uneven track, or dirty wheels.
but if you're going to add a capacitor for that purpose, wouldn't a single diode instead of a bridge be adequate?
crossthedog I have only just gotten used to the idea of using resistors, and now capacitors and diode bridges?
Are you using DCC, Matt? I thought I recall your layout was DC so any thought of a 'diode bridge' (rectifier) and capacitors won't do much for you.
Where I can I prefer to use trucks with bronze strips that pick up rail current from the needle points on the axles. Very little rolling resistance added at all.
Trucks_wired-pkg by Edmund, on Flickr
Athearn makes several types, some even include a molded on caboose generator.
https://www.athearn.com/product/ho-70-ton-truck-with-electrical-pickup-2/ATHG61383.html
Tangent is another source for caboose trucks with reliable pickup.
https://www.tangentscalemodels.com/product/70-ton-gould-caboose-plain-bearing-trucks-with-blackened-normal-tread-wheelsets-and-power-pickup-sku-112/
gregcgood point but if you're going to add a capacitor for that purpose, wouldn't a single diode instead of a bridge be adequate?
Yes. This is the 'flicker-free' circuit I've been using for several years now and it is simple, cheap and efficient:
DCC_light anti-flicker by Edmund, on Flickr
Sometimes I have up to ten LEDs in the circuit (I use a 1/4 watt at R2 in that case) the cap is usually the largest I can sneak into a hidden space. Sometimes getting a 2200µF in there. Don't really need much, the 470 will work just fine in most cases.
ATSF_10-6_Pine-King-wire by Edmund, on Flickr
My total cost for the flicker-free part of the installation is about 75¢.
Good Luck, Ed
As I understand it, the DCC 'power' is not formally AC; it is like blocks of nearly-square-wave PWM (for the data component) with periodically reversing polarity (for the same reason as used in old telephone modems, but that's not important here). Most decoder outputs already "rectify" this to DC, appropriately PWM'ed when needed, and I presume 'well enough' filtered. Google 'Wheatstone bridge" for a less technical understanding about how a diode bridge functions as a rectifier of complex or fast waveforms.
The capacitor in this discussion charges when power is applied, and discharges (usually through a diode, but one oriented in the correct direction for discharge when required) to hold voltage up. It acts the same as a battery for relatively short intervals like the kind of dropouts that lead to 'microarcing'. (An inductor similarly installed would hold current up.) The resistor regulates the rate of discharge from the capacitor.
This is a distraction from the thread topic, which is about arranging assured conductivity from the wheels, but it is relevant to keep in mind because the contact between wheels and some kind of 'wiper' system is only part of assuring good conduction or 'flicker-free' operation. One potential issue with tread-bearing wipers in this context is that dirt or damage of the wrong kind on the wheeltread might cause issues with intermittent contact, and hence microarcing, cumulative with trouble caused by rail-wheel contact.
Bear in mind (no pun intended) that the tension that has to be provided in most of these wiper systems has to permit proper contact of the axles and truck frame. Part of that has been mentioned, in terms of observed running resistance, but the "interface" between a pointed axle end and its bearing point on the coned recess in the sideframe is going to be affected by either lateral or longitudinal pressure on either a wheel or an axle. That is why it seems to me that the 'optimal' system involving pressure is the one already mentioned, that bears upward from below so that the bearing patch is loaded with correct geometry, rather than unloaded to produce something other than stability. Naturally a system that involves no direct pressure, such as the also-aforementioned wraps of wire around the axle, have little or no effect in this (although they do introduce drag, including that from any "conductive" lubricant applied to keep conductive area from oxidizing...)
Incidentally, in my opinion any wiper system needs to have some positive method of adjusting its tension. It is difficult to get that, for example, with a phosphor-bronze contact soldered to the truck, because you have to bend a curve in the middle of the spring to increase its contact pressure, and that can't be done with just two-jaw pliers. You can use jewelry pliers that have one cylindrical or conical jaw, and one concave curved mating jaw, as used for jump rings, or make something with two pins on one side and one on the other, on the principle of a bender. But whatever it is needs to work in the confined space, and precise axis of required adjustment, where the wiper is installed.
i'm always puzzled how multiple electrical contact points between a rail/wheel and some electrical device can fail.
i believe the wipers being discussed are self cleaning, preventing any corrosion from building up. a big advantage. minimizing the contact force will minimize drag on the wheel. curious how small that force can be
wheels rolling across a metal rail don't have this "wiping" effect. while there is a minute amount of friction, it's hardly enough to "wipe" the surfaces clean
i'm curious if there's a way to build a rolling stock wheel cleaner. presumably these wheel accumlate dirt and spread it back on the track after the track
gregcI'm curious if there's a way to build a rolling stock wheel cleaner. Presumably these wheels accumulate dirt and spread it back on the track after the track [is gleamed or cleaned]
The approach I developed was to apply strips of 3M lapping film to long glass strips attached to suitable handles or grips, to make a graduated set of grits as used in track gleaming. Then rotate the wheel externally (probably via a pressure wheel against the rim) while applying the lap to the wheeltread or flange area, simply moving it as the working surface becomes worn or clogged. Logical ways to automate the use of lapping film for this purpose will quickly suggest themselves...
SeeYou190For lighting my string of Rivarossi Heavyweight passenger cars I added jumpers from one car to the next so all the cars form a parallel electrical circuit with one another. It was easier than adding more wipers, and all flickering is gone.
gmpullmanAre you using DCC, Matt? I thought I recall your layout was DC so any thought of a 'diode bridge' (rectifier) and capacitors won't do much for you.
Anyway, my DCC steamer woes are not the topic here.
I have cabooses that I wouldn't mind having lights in, and I'm thinking it may be worth just trying a pair of these trucks with wipers to see whether a light in a caboose would flicker or not (in DC). My old DC locos have old incandescent headlights or new LEDs that I've put in and with only one exception, they don't flicker. I put a nice bright LED in an old switcher, though, and that thing looks like a Navy signal flasher as it goes around the track. And I'm pretty sure it may be track unevenness or schmutz because it seems to flicker in the same places every time.