Most of the club guys use Intermountain., I'm the oddball. Modeling a coal road, we have LOTS of open hoppers, where you can easily see the entire axle, so even with th esmall resistor int he corner, you cna see it on most cars. Maybe I'm just picky. I even noticed a few of mine that need touchups because they weren;t completely covered in the black paint.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
I do something very similar to Randy. I use Intermountain wheel-sets (buy them in packs of 100) for the most part as they have a metal axle (whereas I think the Protos have a plastic axle). The intermountain wheels sets have an insulated end and a non-insulated end. These wheels are also blackened like those Randy described. I use and exacto to scrape the back of the wheel and the axle to clean off the blackener. I use the 603 size surface mount resistors (10,000 ohm). I use the tip of a Pin to apply the CA to the resistor and glue it at an angle over the plastic insulation on the insulated side of the wheel. I have a very fine pair of tweezers I use for this process. I then use another pin to apply the silver paint (I got mine from my local electronics surplus store). The Paint is quite thick (its used to repair traces on PCB's) and a brush doesn't work very well for me. I use the pin to apply a trace between the insulated wheel and the resistor and another from the resistor to the axle of the wheel-set. The reason I like the Intermountain wheelsets is because the tread doesn't need to be polished and the metal axle can be used as a trace so there is no need to paint one all across the axle to the other wheel.
As previously stated, the traces will not conduct electricity until they are dry. I use a volt meter to check each wheel set. It should read within 5% of 10 K ohms.
I sit in front of the TV while doing this as it is a bit of monotonousness process.
I don't bother to paint over the Resistor once it is installed because it is barely visible. The paint doesn't even stand out. I will try to post pictures later when get home.
I do this to 50 wheelsets (of a package of 100). Each Car will get 2 wheelsets with the resistors and 2 that are blank (one of each goes on each end of the car).
I have done about 150 cars so far for the layout. I have a full signalling system on the layout so every car needs it.
Colorado Front Range Railroad: http://www.coloradofrontrangerr.com/
Thanks for the info I'll be trying this out after I order everything, Jim.
I use all Proto 2000 wheels and follow this pretty much exactly:
http://www.mpmrr.net/wheels1.html
My silver paint I got from eBay, a seller called semicro (it's used for scanning electron microscope slides). It's NOT cheap, but don't use the carbon type paint, use silver. A little goes a long way, it hardly looks like my bottle has been touched and I did about 70 wheelsets. I have the 18% stuff but next time I want to try the 36%.
Since Proto wheels are blackened, I use a small burr on the dremelto clean up a small portion of the rear face of each wheel right down to the axle. You have to get right down tot he axle but not cut the wheel off. It's the smallest burr in my Dremel set - really tiny - so you're not goign to cut the axle in half unless you REALLY try. Do both wheels directly across from one another.
For gluing the resistors on, I got a bottle of a thick CA I actually foun at HD or Lowes, from Locktite. It comes in a bottle that has little squeeze arms on the side designed to dispense small drops and it worked perfectly. You need a VERY tiny drop of glu to hold the resisto, if it gets up on the edges where the conductive pads are, it will be useless since CA is an insulator.
What I did was put my wheelsets in one of those wheel painting jigs that holds 4, each witht he area I hit with the Dremel facing up. I pulled 4 resistors from the ammo tape reel the come on, and put a drop of CA on the axle right next to one wheel (instead of dead in the middle). Then using my magnifier light and a small tweezer, picked up and placed each resistor. Two of the sides are tined, these are the contacs. The size specified is rectangular, the long way goes parallel with the axle. While the CA was drying (it's thick, takes a few minutes), I painted the wheel faces with a microbrush and some grimy black paint.
Once the CA was cured (if it's not set it seems to react with the solvent in the silver paint, so don;t rush) it's time to paint the conductive lines. First of all, the paint needs to be WELL shaken. More then regular paint. Silver is heavy and settles out - in minutes. If you look at the bottle when it's been sitting there for a while, what's on the bottom is pure silver. You can fele the weight when you shake the bottle. So shake well. A small brush is needed. Mine came with a small one in the cap. From the picture shown on the seller's eBay store, it looked like the cap brush was going to be far too large, however, when I actually got it, it was tiny like a fingernail polish brush and worked quite well. Whatever you do DO NOT KNOCK OVER THE JAR. It's one thing to spill a $4 jar of paint. Spilling a $30 jar of paint..different story. Not to mention that if I spill a plain jar of paint, as long as it's before 9pm I can go to the LHS and get another, gotta wait a few days to get the silver stuff..
Starting at one side of the resistor, paint a line from the side of it to the back of the wheel. Do not let the paint span the resistor, that makes a short circuit wheelset. It's hard to describe the application technique but forget what you know about proper brush painting because the silver paint does not flow and smooth on like pigment paints. It's basically a carrier with actual particles of silver suspended in it, and as the solvent evaporates it leaves behind the silver which must form an unbroken solid line to be conductive. If you have too litle, it won;t conduct, but you cna always add more later.
The one thing to kep in mind is, it does not conduct until it is completley dry. So don;t be scared. I was worried when the first 4 I did didn;t work, yet the paint looked dry. 10 more minutes and suddenly they worked. Keep a multimeter handy, the wheel jig exposes enough tread that you should be able to touch the probes and check, resistence should be right about what the resistors are. Or just wait until the paint is definitely dry and pop them out. I have my benchtop meter connected to a strip of sectional track with clip leads, so I can set a wheelset on there and check. You may have to press down a bit to get a reding, or if the wheels are totally clean, slide them a bit.
I put two resistors wheelsets, with a 10k resistor, on each car. One resistor and one plain per truck, so I made up sets of each, painted, some with, some without, resistors, and then went to work installign them. Only ones that tested good. If they were reporting as open circuit, I tried adding more silver paint. Usually that worked. In the end I only have 2 out of 70 that would not work. One I think the CA got on the edge, the other I'm not sure.
Since the silver paint is highly visible under the car, even if on the inside edge of the truck, and the plain P2K axles are shiny black anyway, I also painted all the centers. I started brush painting them in the jig but the tried a better way - I just used a cheap can of flat black paitn from Walmart. The first one I did I was worried the paint would react with the silver pait, but it didn't, other paints may be different, but I just did a quick spray of the backs and axles witht he flat black, and it hides the silver nicely.
Once assembled I stick the truck on my test track with the meter connected to verify it is still working. The the get assembled back to the car. In hindsight I should have also been painting the trucks while they were off, now I have to go back and do that. Once assembled, I test the whole car. With a pair of 10K resistors, it shoudl read no more than 10K and no less than 5K. What really helped was using a wire brush in the Dremel to polish the treads of each wheel. Before that, I had to press on the car to get a reading. After polishing, they read as soon as they wheels are on the rails. Plus the wheel tread of a car in use should be shiny. Hold the opposite wheel so the whole thing doesn't spin at Dremel speed and it goes quickly My Dremel is variable speed, I used a medium-slow setting for the wire brushing step.
That was my major project last year at this time, so I could have my cars for my club train ready to go, since we required detection. My present home layout is an unsignaled branch so I have no detection installed, but eventually I will expand to portions that shoudl have signals. So I have hundreds more cars to do. I bought a few more wheel jigs to help speed up the process - doing just 4 wheelsets at a time and havign to go away and wait for paint or glue to dry was the major slowdown. I also have an idea for a wheel testor that will just give a simple red or green LED to indicate the resistence is within spec. Not necessary but something I cna mess with to do some PIC programmign and design. Plus it would be battery powered and portable, instead of my benchtop meter which requires a wall outlet for power.
Paint:
http://www.mouser.com/ProductDetail/MG-Chemicals/8420-P/?qs=OuvZCHmSPC%252bLuVgb7xcPr19hslw/c8kZb1oSR7PpEEM%3d
I haven't done it myself yet, but I would go for these:
http://www.mouser.com/ProductDetail/Xicon/263-10K-RC/?qs=jBethxrBxZaqbmgc1fFFTvoFQVGxIiJwgNLh9Oqx2GI%3d
These are 10K ohm. I actually found a video that uses those exact resistors:
http://www.youtube.com/watch?v=xVshMV6Hb_Q
Getting ready for signaling and detection and was looking for ideas and info to make my own resistance wheel sets,parts and where to buy them. Also any tips on how you made yours and the parts list or numbers. All my cars have metal wheels installed, I am using all Digitrax equipment. Saw a video on u tube but he was using N scale and 1k ohm resistors and conductive paint. Thanks Jim.