I am in the process of converting my Athearn BB GP-50 to DCC. The loco is a smooth runner and has the gold color motor and flywheels. I haven't tested the amp draw but a store I visited said all BB's draw too much current to convert to DCC. I want to also add sound. I'm curious what the cut off point is where a motor is not suitable for conversion. I was under the impression the older style BB motors were borderline candidates but the newer gold color ones can be converted, provided there are no pre-existing issues. I've ordered a ammeter gauge to test my loco, and I understand adding a decoder with sound will add to the existing measured current. The Loksound decoder I'm interested in is rated for 1.5A. The PowerCab manual says its rated for 2 amps and can run "up to" 4 loco's, which suggests loco's in a perfect world require about 0.5 amps each. So in my case, should I be hoping my BB loco draws less than 0.5 amps to allow for the added load of a sound decoder? Does having the sound option greatly increase the current required by a decoder? Do I just need to test the stall current, or should I test it using various loads of freight cars at varying speeds?
Allowable loco motor current draw before converting to DCC
- Thread starter Toolbelt
- Start date
The Gold motor is what is in current production Athearn RTR models and Roundhouse RTR models, and works fine on DCC. The old iron ring motors can draw over 2 amps, and is generally not suited for DCC (or much of anything else) operation because of its high current draw.
The Power Cab can operate several locomotives, as long as the combined draw from all of them doesn’t exceed 2A.
Unless you’re planning on running multiple-unit consists pulling over 50 cars on heavy grades, you should be fine.
The Power Cab can operate several locomotives, as long as the combined draw from all of them doesn’t exceed 2A.
Unless you’re planning on running multiple-unit consists pulling over 50 cars on heavy grades, you should be fine.
Maybe he was just having a bad day at the store (had to wait 30 mins to speak with the DCC expert). When he said BB's draw too much, I asked if he could test it, and he said he charges $50 for any benchwork. My understanding is it takes about 2 seconds to check the power draw? This was my first time visiting this large regional store about 90 mins away in farm country.
#70326 Athearn RTR replacement motor with hex flywheels (for all models except switchers, RS3's) #12032 Hex couplings available seperately
Athearn RTR replacement motor with hex flywheels (for all models except switchers, RS3's) 5-pole skew wound armature, low current draw, very good motor for the price This is replacement motor for older Athearn Blue Box or RTR locomotive motors, not Genesis. Flywheels are Hex drive not the...
ppw-aline.com
If you read the text of the specs, it tells you it is a low-amp-draw motor.
Iron Horseman
Well-Known Member
Well, there is current draw and there is current draw. Sure one can just throw it on and see where the meter goes, BUT ... There is usually a start up spike current that is higher than a normal running (the original Proto-2000 E and PA units had this problem they could spike up to 4 amps even though running current was closer to 500ma.). Then there is loaded current. As one would expect a motor will draw more current when pulling a load or going up a hill or both. As such for determination of a DCC install there is what they call "full slip" current. That is where the loco is put into a situation where it is not moving but the wheels are still turning. That should be the current draw it uses under normal operating conditions, the wheel slip prevents it from drawing any more. Then there is the max current draw where one presses down on the locomotive until just before the wheels stop turning. Then, of course, finally, there is stall current which is the amount it draws when it is no longer turning but stalled. that set of tests will give a full profile of a motors current characteristics.
I think that is an upgraded 5-pole skew wound armature, low current draw, very good motor for the price replacement motor for the original (like mine). Are you suggesting I simply replace my motor, if it turns out to be drawing too much current? This is my motor which looks similar but not sure if its skew wound.#70326 Athearn RTR replacement motor with hex flywheels (for all models except switchers, RS3's) #12032 Hex couplings available seperately
Athearn RTR replacement motor with hex flywheels (for all models except switchers, RS3's) 5-pole skew wound armature, low current draw, very good motor for the price This is replacement motor for older Athearn Blue Box or RTR locomotive motors, not Genesis. Flywheels are Hex drive not the...ppw-aline.com
If you read the text of the specs, it tells you it is a low-amp-draw motor.
Attachments
Yes, I will put it through various test scenarios to intentionally max out the current. But what would be the current threshold to decide whether this motor is a conversion candidate? 1 amp max?
Basically, it's the "new, improved" version of what you have. If you don't want to take a chance, you could get this motor, and the hex shaft kit, and be about the cost of the hobby shop guy's bench test fee.
That was my impression as well based on Google and YouTube and these forums. I know the old "can" motors were problematic, and I intended to test my loco's amp draw in any case, however this store gave a blanket statement about all BB locos as though "everybody knows that", and I felt I had completely missed something in my research.
Iron Horseman
Well-Known Member
That depends on the rating of the decoder. If it is a 1 amp then yes, if it is a 1.5 then there is room to spare. They make decoders rated up to 4 amps.
I'm trying to detail/upgrade this unit for less than the price of a new off-the-shelf unit at the local store, but it's been fighting me. lol As it stands, I've spent about $75 on detailing and the Loksound w/speaker will add another $160, so a new motor and possibly couplings for $50 will put it way over the top. I'm hoping my draw tests work out and I can avoid having to make that decision. This loco easily pulled 27 cars and I could have added more except the loco was almost touching the caboose on my 4 x 8 layout. lol All figures are Canadian btw.
Crossing fingers that I hit about 1 amp.
Is that Canadian?Crossing fingers that I hit about 1 amp.
Yuppers.
I went to my local regional store and they had my same opinion that the gold coloured BB motors are not problematic when converting. I had to go there anyways as I had busted the rubber motor mounts, so I switched those out for the newer screw secured versions. I only wish their DCC stuff was more competitively priced. They are literally 30% higher on decoders and throttle systems, plus charge a fee to download sound files to any decoder they sell.
Picked up a simple analog amp gauge (0-10 amp scale). I assume I just wire it in series with one of the track feed wires, and may need to change track direction to read the amps? I didn't get a 0 center gauge as it's just for a quick check of amp draw. No shunt required?
Per the OP, Currently (no pun intended) track power is DC only.
True dat. And once I switch to DCC, the PowerCab has a built-in current gauge if needed.
