The rest of the story ...

TOMA is forcing me to think through how I'm going to build the first few sections of Siskiyou Line 2 (SL2) to completion. All the scenery and structures need to be complete, the backdrop needs to be completely done, and the everything needs to work, including the signals.

On my first layout (SL1), I did not put any thought into a number of things including signaling. My thinking was "I'll worry about that later" ... which turned out to be a really bad idea. Trouble was when later came, I realized I had made critical mistakes in layout design that could not be easily corrected without doing a "rip and replace" of several parts of the layout.

Even though the dismantling of SL1 and the starting of SL2 construction has been put on hold until this coming winter ( see my last blog post), the TOMA planning process has gotten me off my laurels as to signaling, for one thing. I've done enough research to know now I need resistance wheelsets on my rolling stock.

Since I'm also working on book 2 of my Run like a Dream series on rolling stock, it seemed like a perfect time to explore doing resistance wheelsets. The book includes the comprehensive rolling stock checklist I'm using with my Siskiyou Line rolling stock. The bulk of the book covers everything needed to get the rolling stock to pass the checklist and perform its very best on the layout, as well as how to debug any issues that may arise.

One line item on the checklist deals with checking that each piece of rolling stock has resistance wheelsets that comply with my standard. As a result, I did the research and worked out how to make my own resistance wheelsets.

Yes, you can buy resistance wheelsets too, but making them myself is easy and very inexpensive. Plus I can use my standard all metal wheelsets to comply with my single-supplier rule for most consistently predicable performance.

MAKING MY OWN RESISTANCE WHEELSETS

For supplies, I get some 10K SMD resistors in the 1206 size. I also get some Bare Conductive Electric Paint (Amazon:  a.co/fJZ1Smg, $13.89 a tube, Prime). Here is a photo with the 10K SMD resistor and electric paint shown, plus a finished resistance wheelset in the middle of the frame:

 
​The materials needed to make my own resistance wheelsets. In the middle is a finished Intermountain all-metal HO wheelset with the resistor installed.

The process is simple: I just use some gap-filling flexible superglue (Amazon: a.co/dT2HTUW) to glue the tiny resistor on the end of the wheelset with the plastic insulating bushing. I make sure to bridge the plastic bushing with one end of the resistor resting on the metal axle and the other end of the resistor resting against the metal back of the wheel. 

Then I apply the conductive paint to the metal ends of the resistor and onto the metal wheelset axle and wheel back. With conductive paint, it does not develop its full conductivity until it's completely dry, so I give it a couple hours, then I test the wheelset with an ohm meter:

 
Testing a finished wheelset to make sure it reads a perfect 10K.

I set the meter multiplier on 1K and connect up the test probe clamps to each end of the wheelset. As you can see here, the reading (if done properly) is a perfect 10K.

When I put wheelsets on the cars, I put two wheelsets per car on the inside of the trucks away from the couplers to make sure they don't foul the coupler. The "R" indicates resistance wheelsets:

 
I install two resistance wheelsets per car (indicated by the Rs). Two per car helps guarantee the car will trigger the signal detection.

I like using the two wheelsets as insurance that at least ONE of them will function and cause the signal detectors to register that something is in the block.

Locomotives automatically will trigger the signal detector because the loco motor circuit is connecting the two rails to each other with current flowing through. But rolling stock will not trigger the detector unless they have resistance wheelsets installed that allows a tiny current to flow from rail to rail. By installing two resistance wheelsets in all rolling stock, then whenever there is anything in the block, the signals will trigger.

Even though I'm not working on the layout itself right now, I'm still moving forward on things SL2 will need to get up and running. Thanks to TOMA, I'm being forced to work through all the things needed to get a fully functional railroad. I love that TOMA is making me find and solve the issues early this time around!

Slick!

Hi Joe,

Very slick procedure.  It took care of the thought (dread) of having to solder resistors onto the trucks for me.

You've successfully added one more thing to my to do list!!!

Nick

Joe, how is that Bare

Joe, how is that Bare conductive stuff holding up for you. I tried to use it and found that the about a week after the paint cracked and came off the wheel axle. I did clean the axle and back face of the wheels prior to doing the application. I ended up switching to a liquid silver paint that works like a charm. Just an FYI to check your first few maybe a week or two after doing them. Don't get to far in and then have to go back and re-do.... (#%*@)

a set of n scales that I did for a friend

Liquid silver paint?

Can you be more specific, like provide a brand and maybe an online link?

I haven't had enough time to let this process age much, so I'll keep an eye on things and let you know. Meanwhile, the liquid silver paint sounds interesting ... tell me more.

Joe, how much current loss

Joe, how much current loss per car doing this? I am wondering if more than one hundred cars would cause a noticeable drop on the layout? Suppose there were several hundred of these cars on a layout, would that be enough of a power loss to cause problems? I am thinking that every car on the layout would then be a source of power loss. So if one had a big yard and lots of industry tracks with cars in them could this be a new issue to address?

I am thinking of this in terms of club size layouts that might have up to 1000 cars on the layout.

Doing the maths

Dear Rob,

Maths time :

- Assume each detected axle is 10K Ohm.
- Therefore. 2x such axles per car in parallel = 5K Ohm presented at the rail, per car

Assuming:

- 14V RMS at the rail (DCC spec)
- Perfect pickup of the wheelset at rail (questionable, but we'll go with it for the sake of the example) 

14V / 5K Ohm = ?? Amps

= 0.003 Amps (3 milliAmps) per car

Context, that's significantly less than one LED (typically 20 mA to achieve full brightness) in a locomotive.

Now, multiply by 100 cars on a layout,
and we have a total additional load on the booster of 0.3 Amps,
or the same as a reasonably efficient current day HO diesel mech.

Once we get up into the 1000s of cars, there may be something to worry about,
(would be 3Amps of load using the above values),
but then again, If the layout is genuinely big enough to host 1000 cars on-rail at the same time,
I'd expect the booster farm to be equally large/grunty...
(and most any layout of said size would likely be broken up into multiple-booster-districts,
with the cars and-thus-load being spread around between individual boosters/districts,
IE all 1000 cars are unlikely to all fall on top of one particular booster).

Happy Modelling,
Aim to Improve,
Prof Klyzlr

PS we are also assuming 3mA is enough to trip the detectors in use,
raising the per-car current draw (lowering the axle resistor value)
would require doing the maths anew....

Thanks professor. So if

Thanks professor. So if everything works out right 1000 cars with resisters would pull about 3 amps if they were all on the layout on powered track. A 100 car train would pull less power than one locomotive under most conditions.

That's cars PER booster

"When I put wheelsets on the

Hi Joe, Can you clarify this part, why would a resistance wheel set be more likely to foul a coupler than a regular wheel set would? .....DaveB 

Resistor location

Dear Dave,

The way the resistor is placed in the pic below

may put the resistor in the line-of-fire of the coupler draftgear box lid, edge, or even the screw(head) as the truck rotates to take a given-direction curve, (if the resistor axle was the outboard one). 

Some modellers prefer to install the resistor parallel with the axle, half-way between the wheels,

which would possibly put the resistor and the draftgear box screw in conflict, particularly if the truck is the "loose one" on a 3-point-configured car, and the car was transitioning from flat-to-upgrade (or some other condition which would make the truck rock fore/aft, closing the gap between the outboard axle and the draftgear lid).

By placing the resistor-equipped wheelset as the "inboard axle", it generally tends to avoid the issue from the outset... (and also hides the additional "weird bump on the axle/wheel" under the body shadow of the car... ).

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Silver Conductive Pens...

Ah yes, the conductive pens. They are quite a bit more expensive. But that is not the real problem. The shelf life is not very good unless you sit down and do your whole fleet until the stuff is used up. If you do 20-100 cars then move on to other tasks, when you come back the conductive pen may be dried out enough to not work.

I received a new pen from the supplier and out of the package it was already clogging and dried out.

I've been using little pots of "wire glue" that cost less than around $6. They have a shelf life closer to 2 years, For that price you may be throwing out half the pot, but who cares? A pot would do at least 500+ cars at two resisters per car.

I also use 10K resistance for N scale. The C/MRI DCCOD has sensitivity adjustment and will detect your finger placed across the rails. 10K resistance is very reliable and has insignificant effects on track or booster performance.

What about a combination of current-sense and infrared?

While my layout isn't big enough for any signals, I've always been interested in signal system implementations should that day come.  One thing I've thought about is using a combination of current-sense detection and infrared.

For current-sense, hook that up as normal.  As long as a locomotive (or powered caboose/EOT) is in that electrical block, it is sensed as occupied.  Now, place an infrared detection circuit at each block boundary, and as long as anything is covering the sensor at that boundary, it can trigger both adjacent blocks as being occupied. As a train progresses, the locomotive ensures that it is detected while fully within a block, and the IR detection ensures that both blocks are detected while it is crossing a block boundary.

There is a tradeoff.  The infrared detectors are more expensive than resistors, but you need fewer of them. Resistors are cheap, but you need to modify hundreds of axles, and cars that aren't equipped still don't get detected (like visiting equipment).

Thoughts?

Craig

Joe, this is not an exact

Joe, this is not an exact match to what I used but can not find the link I used and the bottle is all gone. It did my fleet of 300 +/- cars and after a while the remaining liquid did dry up. 

https://www.amazon.com/Grams-silver-Conductive-paste-brush/dp/B01GKLIJMI/ref=sr_1_3?ie=UTF8&qid=1505927969&sr=8-3&keywords=silver+conductive+paint

I recently purchased another container of a different brand but have not used any of it yet. 

In regardss to the question about the difference a fleet of resistor wheel sets make... NONE!! I run with two boosters and my railroad is split prety close to the center of the run. I see no difference is voltage at the railhead. 

"may put the resistor in the

    Thanks Prof.   I guess these resistors are bigger than I was imagining. When I find interference issues it's usually the flange backs not the axles causing the problem .......DaveB

Test TOMA

Joe,

You should make a single test TOMA section to validate all your new standards. After you are finished you could either incorporate it, recycle it, use it as a diorama for making outdoor photos or auction it off.

Tim G

Tim, you got it!

Tim you got it! That's exactly what I plan to do.

That's one advantage of TOMA, for sure. The "build it to completion" approach bakes in testing most of your layout construction methods and standards up front.

There is a maxim in building software (my career background) that I think applies here: plan to throw the first one away.

The idea is you learn *so much* from the first attempt that you should bake in a process right up front for maximum learning that you can then roll over into building something that will last.

So yes! I plan to throw the first TOMA section away, since it's where I will do a LOT of learning.

Chainsaw TOMA....

Well, I think the title says it all, doesn't it?

The TOMA advantage

Joe,

This is where TOMA has a big advantage over traditional layout building. I am 47 years old and first became serious about Model trains 40 years ago. Over the years I have built numerous layouts. Each time learning something and using the new found knowledge when building the next. Often I would get pretty far along with one when I would realize, man I could do it better now that I have learned from past mistakes. But the problem is that you are reluctant to tear it all down and start over. I can only imagine how you must feel replacing SL1!  This is why I would wholeheartedly suggest the TOMA concept to folks early on. It is a whole lot easier to replace a couple of 2x6 foot modules than room full of bench work at various stages of completion.

I look forward to seeing this first SL2 'Concept' TOMA section appear on the pages of MRH.

Tim

The toughest thing I think is

The toughest thing I think is to realize something has a flaw. Then next it is tough to find a cure for the flaw, in some cases the flaw or flaws become great enough to cause one to want to start over. I offer everyone a tip of the hat that decides to start over after discovering the flaws. I offer an even bigger tip of the hat To Joe and others for deciding to do a beta test in a small way to test the viability of various options and to experiment with what may work best for what the builder is trying to accomplish. Thanks for tossing this concept out to the rest of us. I suspect it may become as important a milestone in our hobby as the beyond the basement concept and some others we are all now familiar with.

Joe

where can we order the right size resistors from?  You had links for the glue and paint but no resistor link? 

Go TOMA

Pat

Got the resistors from Amazon

Infrared - resistance hybrid block detection

Craig -

I've implemented your idea with a twist on all my short blocks, mainly the OS at the end of sidings that is usually 3 to 4 cars long.

I have current sensing for each block and all the caboose's have lights along with the end car of passenger trains. So, I needed to sense the rest of the train when the head end or tail end wasn't in the block. A single optic sensor anywhere in the block will work, and then have that sensor turn on a relay that connects a resistor across the rails, that way you only have 1 sensor input and the logic is easier to deal with.

The thought of installing 600 resistors on metal wheel sets that needed to be purchased instigated the above plan.

Clark Bauman

@craig - modular signal system

Craig - look at the design of this system, it sounds like just what you had in mind. gs

Book 2

When is your 2nd book going to be out?  I know nothing about resistors on wheels or why I need them. Something to make the signal system work. But I am doing the TOMA method now cause of you amd trainmasters tv.  Just ordered my second piece of benchwork.  

Now need to do some studying and need book 2.  When can we expect it?