Samhomgsa current draw?

[daniel_leavitt2000]

I'm looking at adding DCC to a few old brass engines (A U23B and a U33B). Will a standard one amp decoder be enough?

Also, has anyone tried replacing the stock wheel wipers with something a bit more solder friendly?

Any other tips? I'm worried about shorts.

[peteski]

You are taking about N scale brass engines with stock motors?  Sure, any N/Z scale decoder (1A motor current rated decoder) will work.  Those motors should not be consuming any more power than any other N scale size motor.

But as you suspect, shorts (between either rail, and motor or function outputs) can spell death to a decoder.

[ChristianJDavis1]

I've used the newest Lokpilot V5 nano(?) Decoders with great success in N scale brass units by Samhongsa, and even an HO unit, and they are only rated for .8 amps, I believe. I have never had a problem with blowing one, but I would say definitely do some maintenance on the drive before trying to install a decoder. As far as shorts go, I have a lot of Samhongsa B and C truck diesels and none of them shorts very often unless it has derailed for some reason or the pilot hits something. For the wipers, I can't really help, but I have not ha anytrouble soldering to them, but at least one half of the wipers is help in place by the truck assembly, so should come right out and you can replace it with whatever you want.

*Edit* I forgot to mention ESU has an overload protection you can load before you ever install it in a locomotive; if the current draw is too high, it just won't work versus frying the decoder.

[MK]

*Edit* I forgot to mention ESU has an overload protection you can load before you ever install it in a locomotive; if the current draw is too high, it just won't work versus frying the decoder.

Oh?  Do you need a LokProgrammer to load it?

[peteski]

The following info was taken from the LokPilot V5 decoder manual.

5.2.7. Protection
All function outputs as well as the motor output have protection against overload and short circuit. We want you to enjoy your Lok-Pilot decoders for a long time.

6.9.1. Overload Protection of Function Outputs (Blinking)
The function outputs of LokPilot decoders have electronic protection against overload and short circuit. The decoder keeps checking the sum of all function output currents. If the current is too high, the decoder will switch off the outputs. After about 1 second, the decoder tries to switch them on again. Should the current still be too high – perhaps due to a short circuit – the same procedure starts again.

CV124 Extended Configuration #2

Bit 5 Motor Overload Protection

0=Motor is not switched off when blocked (stalled).
1=Motor is switched off for a few seconds when blocked (stalled) to avoid burnout

So it appears that there is nothing additional to "load" -- the over-current protection for *ALL* the outputs is built-in, and always enabled.  The CV124 setting just adds another layer of protection for stalled motor (regardless of how much current it consumes).  ESU likely detect stall by lack of BEMF from the motor.

[nstars]

Also, has anyone tried replacing the stock wheel wipers with something a bit more solder friendly?

Any other tips? I'm worried about shorts.

My brother has worked om several Samhongsa brass locomotives and in all cases he has replaced the two steel wheel wipers in a truck with one home made phosphor bronze wiper at the back of the wheels. He mounted this wheel wiper on a piece of PCB so he could use the frame of the truck as the second pole. Note, the PCB required some milling of the truck frame.

This method reduced internal resistance significantly while retaining 8 wheel pickup. This made the use of regular DCC decoders possible.

Marc

[Kentuckian]

My brother has worked om several Samhongsa brass locomotives and in all cases he has replaced the two steel wheel wipers in a truck with one home made phosphor bronze wiper at the back of the wheels. He mounted this wheel wiper on a piece of PCB so he could use the frame of the truck as the second pole. Note, the PCB required some milling of the truck frame.

This method reduced internal resistance significantly while retaining 8 wheel pickup. This made the use of regular DCC decoders possible.

Marc

I would love to see a photo!

[daniel_leavitt2000]

I am thinking of replacing all the pickups with phosphor bronze wire, as I have several sizes in inventory. I am hoping the round profile would produce less friction. Now I have to figure out how small I can go before resistance heats them up too much.

[peteski]

I am thinking of replacing all the pickups with phosphor bronze wire, as I have several sizes in inventory. I am hoping the round profile would produce less friction. Now I have to figure out how small I can go before resistance heats them up too much.

What is the smallest PB rod/wire you have?  At the the short length the pickups have and relatively low current, I don't think heating will be a problem. Will those pickups rub against the tread, flange, wheel back, or axle?

[nstars]

I would love to see a photo!

I’ll see what I can do.

MArc

[daniel_leavitt2000]

What is the smallest PB rod/wire you have?  At the the short length the pickups have and relatively low current, I don't think heating will be a problem. Will those pickups rub against the tread, flange, wheel back, or axle?

I'm thinking of .001" rod. I'm not sure if it's possible to do wheel back wipers without causing a short. I have yet to test this model. I really hope it does not have any split gears, I don't know where to get replacements.

[peteski]

I'm thinking of .001" rod. I'm not sure if it's possible to do wheel back wipers without causing a short. I have yet to test this model. I really hope it does not have any split gears, I don't know where to get replacements.

0.001" PB rod?! Are you sure?  That's thinner than a human hair!!  More like a wire or a filament than a rod.  Where did you find it that thin?

That will not make a good electrical wiper, but not just because of the limited amount of current it can handle. It is also too soft. Wipers need to be stiff and springy enough to remain in positive contact with the wheel or axle. Too little pressure and the contact will be unreliable.

I was thinking more like 0.005" - 0.008" rod.  Brass locos I have serviced use wipers that are even thicker (probably more like 0.010", but in short lengths, that is a bit too stiff IMO).

As for cracked gears in brass locos, we have some good experts here who can likely steer you in the right direction for finding replacement gears.

Also, have you checked out Spookshow's page on these? http://spookshow.net/loco/hmuboat.html

[daniel_leavitt2000]

0.001" PB rod?! Are you sure?  That's thinner than a human hair!!  More like a wire or a filament than a rod.  Where did you find it that thin?

That will not make a good electrical wiper, but not just because of the limited amount of current it can handle. It is also too soft. Wipers need to be stiff and springy enough to remain in positive contact with the wheel or axle. Too little pressure and the contact will be unreliable.

I was thinking more like 0.005" - 0.008" rod.  Brass locos I have serviced use wipers that are even thicker (probably more like 0.010", but in short lengths, that is a bit too stiff IMO).

As for cracked gears in brass locos, we have some good experts here who can likely steer you in the right direction for finding replacement gears.

Also, have you checked out Spookshow's page on these? http://spookshow.net/loco/hmuboat.html

Yeah that was supposed to be .01"

[peteski]

Yeah that was supposed to be .01"

Ah ok, that makes more sense.    I would likely go thinner. Even 0.080 0.008" or 0.050 0.005" (if you can find it), would have plenty of thickness to carry the current, and should be flexible enough not to create too much friction, while till exerting enough pressure for a good contact and be springy enough to stay in contact with the wheel as the wheelset moves laterally or vertically in its bearings.

[mmagliaro]

Okay everyone,  all together now!   3 digits for the wire thickness...   LOL!   

.010", .008" or .005"  ?

.010" is a "maybe", but in my experience is far too stiff for an N Scale wiper.   .008" is pretty commonly available (Tichy Train Group
carries it in convenient 12" lengths).  But if these are typical contacts that are only about 1/2 the length of a diesel truck,  (from the attachment point to the wheel) even .008" is stiff.

If you can get some phosphor bronze strip or sheet that is .005", it would be better.

My go-to place for this is Eileen's Emporium in the UK. 
https://www.eileensemporium.com/materials-for-modellers/product/phosphor-bronze-flat-section-1-0mm-x-0-15mm-x-150mm/category_pathway-1100
That's a strip  1mm x   0.15mm (about .039" wide and .006" thick).

Eileen's sells really nice product and they are very reliable.  You just have to wait a couple of weeks for it to be shipped from England.  But once you accumulate a stash of various metals and sizes, it's awfully nice stuff to have around.