Author Topic: Resistance wheelsets  (Read 2021 times)

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Bill H

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Resistance wheelsets
« on: October 18, 2021, 08:08:00 AM »
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Any druthers or experiences with resistor wheelset specs for a large amount of cars running on a Digitrax layout? I have heard 10k ohms to 22kohms 1/8 watt to 1/4 watt.

Kind regards,
Bill

Ed Kapuscinski

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Bill H

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Re: Resistance wheelsets
« Reply #2 on: October 18, 2021, 10:00:31 AM »
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Ed;
Any reason why you went 10k ohms resistance? Someone told me not long ago that Digitrax recommended 22K, but I have seen a lot of folks running 10K. Same puzzle about 1/4 watt or 1/8 watt. I seem to remember Daryl Kruse went 10k 1/8 watt. Maybe it really won't make much difference. Just was thinking about a couple of hundred cars and a dozen engines with sound taking a lot of juice...

Kind regards,
Bill

Ed Kapuscinski

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Re: Resistance wheelsets
« Reply #3 on: October 18, 2021, 10:29:50 AM »
+1
Ed;
Any reason why you went 10k ohms resistance? Someone told me not long ago that Digitrax recommended 22K, but I have seen a lot of folks running 10K. Same puzzle about 1/4 watt or 1/8 watt. I seem to remember Daryl Kruse went 10k 1/8 watt. Maybe it really won't make much difference. Just was thinking about a couple of hundred cars and a dozen engines with sound taking a lot of juice...

Kind regards,
Bill


The article I read said 10K does the trick. I think this was it:
https://jamestrainparts.com/2015/12/07/adding-n-scale-wheelset-resistors-for-circuit-detection/


John

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Re: Resistance wheelsets
« Reply #4 on: October 18, 2021, 10:56:49 AM »
+1
I use 10K and some graphite paint .. put one resistor wheel on each truck, and you should be fine .. 

John

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Bill H

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Re: Resistance wheelsets
« Reply #6 on: October 19, 2021, 07:02:57 AM »
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...put one resistor wheel on each truck, and you should be fine ..
John:
Are you actually putting two resistors on each car i.e. one on each truck ?

Kind regards,
Bill

Sokramiketes

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Re: Resistance wheelsets
« Reply #7 on: October 19, 2021, 09:01:27 AM »
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Your question is somewhat dependent on which detectors you're using.  10k is enough for a good detector like the Chubb DCCOD.  22k might be what's needed with Digitrax current detectors.  Or, 10k at each end of a car. 

C855B

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Re: Resistance wheelsets
« Reply #8 on: October 19, 2021, 10:36:41 AM »
+1
Your question is somewhat dependent on which detectors you're using.  10k is enough for a good detector like the Chubb DCCOD.  22k might be what's needed with Digitrax current detectors.  Or, 10k at each end of a car.

10K at each end of a car would amount to 5K per car. Resistors in parallel divide the value. That's too little resistance, "too little" meaning enough increased parasitic current draw on track power to take away from available propulsion power. A train with 50 cars each with two 10K wheelsets is going to be 100Ω, and therefore draw 140mA on a DCC MRR, almost as much as a non-sound loco not working too hard.  I (strongly) suspect the Digitrax recommendation of "22K" is likely one on each truck, amounting to 11K per car, so we're roughly back to 10K per car.

10K has been the recommended value for detection since... well, since dirt. I recall putting 1/10W 10K "old style" resistors on HO models back in the 1960s, wrapping one lead around the axle and soldering the other lead to the back of the insulated wheel.

That conductive paint Ed found is da bomb. I was brewing my own conductive glue out of CA and graphite powder, and it was a hassle to get the formula right and have it stay open long enough to do more than one or two wheelsets.

I use one per car, on the inner axle of the "A" (brakewheel) end. This seems to handle most situations, although 86' cars like auto parts boxes and piggyback/container flats get one on each truck, again on the inner axle.

John

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Re: Resistance wheelsets
« Reply #9 on: October 19, 2021, 12:48:53 PM »
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John:
Are you actually putting two resistors on each car i.e. one on each truck ?

Kind regards,
Bill

Not all -- but I do on some .

John

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Re: Resistance wheelsets
« Reply #10 on: October 19, 2021, 12:54:31 PM »
+1
Your question is somewhat dependent on which detectors you're using.  10k is enough for a good detector like the Chubb DCCOD.  22k might be what's needed with Digitrax current detectors.  Or, 10k at each end of a car.

I have Digitrax BOD4, BDL16, and RRCircuits BODs ... they all work with 10k resistors .. I went around to each block, and dropped a 10K resistor across the tracks to test them ..

Sometimes detectors don't work if the wheels are not making proper contact .. to overcome that, I've put resistors on about 10% of my fleet .. seems to work

Sokramiketes

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Re: Resistance wheelsets
« Reply #11 on: October 19, 2021, 01:22:39 PM »
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You're right of course... brain fart.

Bill H

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Re: Resistance wheelsets
« Reply #12 on: October 21, 2021, 06:25:30 PM »
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Mike:
OK, 10K it is. Any thoughts on 1/8 or 1/4 watt?

Kind regards,
Bill

peteski

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Re: Resistance wheelsets
« Reply #13 on: October 21, 2021, 06:35:03 PM »
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Mike:
OK, 10K it is. Any thoughts on 1/8 or 1/4 watt?

Kind regards,
Bill

1/8W is plenty good.

Assuming there is 12V at the track the resistor will  dissipate (12 x 12)/10000= 0.014W That is just a fraction of 1/8 (0.125) Watts.
But also consider the physical size of the resistor. If 1/8W is physically too difficult to work with, use 1/4W.
. . . 42 . . .

mrp

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Re: Resistance wheelsets
« Reply #14 on: October 22, 2021, 04:30:01 AM »
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I use a 10K resistor. Size is 1206.
I find 1 per car is enough to set off the detectors, in my case Bruce Chubb C/MRI detectors.
But, for long cars like TOFC cars, I use 2 per car.

A different brand of detector may need different resistance to work reliably.
So, some experimenting is needed.
Dirty track and wheels can degrade the performance, so you may find you need 2 per car.
Also, you may find the detectors work better if the car is rolling as opposed to standing.

The resistor is mounted at a 45 degree angle using a dot of gel super glue.
For the electrical connection, I use Super Shield by MG Chemicals

Michael Pennie