ANGELA TROTTA THOMAS CHRISTMASTIME HOBBY STORE ongoing motor/board problems

Some more info as I'm going through things, I have no idea what sub-model of the RF-300 motor Lionel uses, but the spare I tried out is an RF-300C-11440.

Specs on this motor are below:

RF-300CA-11440

Voltage range:0.7-5.0

Nominal Voltage: 2V

No Load Speed: 2200

No Load Amperage: 0.018

Speed at Max Efficiency: 1600

Current at Maximum Efficiency: 0.055

Torque g.cm at Max Efficiency: 2.8

Torque mN.m at Max Efficiency: 0.27

Output Power at Max Efficiency (watts): 0.057

Stall Torque g.cm: 12

Stall Torque m.Nm: 1.18

Stall amperage: 0.17

Based upon the board components and output, should this motor be having problems starting and turning the display?

Do you have a way to test the motor's performance against its specifications?  (Amp draw with no load, amp draw under load, amp draw at stall, etc.?)  I am wondering if the motor might be the issue.  That and it may be operating at close to its non-operating parameters.

Also, do you have a (measured) DC power supply that you can use to test with a slightly higher voltage (say 3.5 volts)?  Make sure you disconnect the current power supply from the circuit during this test.  If you don't, you will back feed and damage the current power supply.

I'm guessing its the motor not performing at it's specifications, but without testing hard to tell.

@DaveGG posted:

Do you have a way to test the motor's performance against its specifications?  (Amp draw with load, amp draw under load, amp draw at stall, etc.?)  I am wondering if the motor might be the issue.  That and it may be operating at close to its non-operating parameters.

Unfortunately, my meter can do millivolts, but not milliamps, it's a Fluke with the clamp-style amperage. I haven't sprung for a more expensive meter yet.

Also, do you have a (measured) DC power supply that you can use to test with a slightly higher voltage (say 3.5 volts)?  Make sure you disconnect the current power supply from the circuit during this test.  If you don't, you will back feed and damage the current power supply.

I have a DC power supply on the bench. I'll try a few higher voltages to see how the motor behaves.

I'm guessing its the motor not performing at it's specifications, but without testing hard to tell.

I agree. I just find it odd that we have 3 motors that are bad in two different gearboxes (the original motor/gearbox combo, the replacement motor I had in the original gearbox, and now a new motor/gearbox combo from Lionel).

As I mentioned, all the boards are outputting the same 2.9 volts even though they're labeled as 5v at the motor output.

I wish I had a way to identify the "stock" motor specs. That would be a great help.

Looks like the same gear box as the Lionelville hobby shop, I recently had one that also couldn’t muster enough torque. Upon further inspection the brushes in the cheap motor crapped out. You can get a pack of 3 motors on Amazon

@zhubl posted:

Looks like the same gear box as the Lionelville hobby shop, I recently had one that also couldn’t muster enough torque. Upon further inspection the brushes in the cheap motor crapped out. You can get a pack of 3 motors on Amazon

Yep, basically all Lionel accessories use these RF-300 motors, but they come in different specs with regard to torque/operating speed/voltage range. That's a big part of the question here- just which of these is correct.

There's an old thread about the Lionel Ferris Wheel on here and there was a label inside calling out the RF-300CA-09550. If they're using the same motor about two decades later (possible), it's a tough one to find at this point.

@DaveGG posted:

Do you have a way to test the motor's performance against its specifications?  (Amp draw with load, amp draw under load, amp draw at stall, etc.?)  I am wondering if the motor might be the issue.  That and it may be operating at close to its non-operating parameters.

Bought a new DC power supply with adjustable max voltage and amperage outputs.

Using this, I went to the chart on these motors and went from lowest stall current up until I got to a place where the motor would run, then purposely forced a stall. Figured that this could tell me what motor I have if nothing else would.

The motor I have appears to be the RF-300CA-11400. Stall current is listed as .28 amperes. I'm stalling it and getting .279 ampere draw shown on the display on the power supply. While running, the motor is bouncing around on its draw between .24 and .27 amps. On the spec sheet, the motor's max efficiency is listed as being at .11 amps, and a no-load draw of .018 amps.

Seems the motor is riding right on the knife's edge with regard to current draw as it operates, being only .01-.06 amps away from stalling...

So, thoughts on where that leaves me?

I'm thinking it leaves me with an inefficient and undersized motor in a gearbox designed specifically for that motor.

Found another motor, the RF-300CA-12250. These have a stall torque of 2.51 mN.m vs the motor Lionel installed at 2.06, and it also has a stall current of .39 amps, or .11 more than the stock motor. The trade-off is it runs at a no-load speed 500 RPMs faster, and a max-efficiency speed 430 RPMs faster.

May need to modify the board to reduce the speed somehow.

Tremendous and diligent work, Andrew.

I wonder if anyone has this accessory that works as intended? It was not an inexpensive item.

@Paul Kallus posted:

Tremendous and diligent work, Andrew.

I wonder if anyone has this accessory that works as intended? It was not an inexpensive item.

I think they all have these issues. I'm on the 3rd motor/gearbox on this thing (original, 1st replacement, now the one I'm using to figure out motor specs). The motors are failing because they're operating right on the edge of stall at all times. The gearboxes are clunky and cheap. For the cost of the accessory it's really low quality. I have the older Lionel hobby shop as well, and it's run every day in December for the last two years when the Train Garden is open (3 hours minimum every weekday, 6 hours minimum, every weekend day) without failure. It also ran during the 2019 season. So we have a confirmed minimum of 350 hours on it without issue. This has run correctly for a max of 45 hours and is on its 3rd set of guts to do so.

I've reached the point where my knowledge taps out. Self-taught on electrical/electronic matters.

Have the new motors on the way and will test using the existing board, but if the speed is too great, I'm going to need someone like @gunrunnerjohn to provide some of his great advice on how to drop the voltage from the 2.9v output on the stock board to a lower level (added/replaced board components; with this board being a lot of surface-mount, probably something in-line past the stock output). These are things I want to learn how to diagnose/develop on my own, but unfortunately don't have access to the kinds of people locally to help me along.

When it comes to all this, as I mentioned I'm totally self-taught, but I need a little more guidance on how these boards are designed and get us from a 10-20v AC intput to a 2.9v DC output.

I know that the input leads from are soldered on the back side of the board to component D1, which is a bridge rectifier, getting us from AC to DC. I also can obviously tell what and where the capacitors are. But, I don't know really how the flow on the board gets us from rectified DC to the output voltage of 2.9v and how to tamper with it to change the voltage in any fashion.

A diode drops 0.7V roughly- depending on current- cheap and easy way to do it externally.

In fact, the older hobby shop used just such a string of diodes for that voltage drop.

@Andrew B. posted:

When it comes to all this, as I mentioned I'm totally self-taught, but I need a little more guidance on how these boards are designed and get us from a 10-20v AC intput to a 2.9v DC output.

I know that the input leads from are soldered on the back side of the board to component D1, which is a bridge rectifier, getting us from AC to DC. I also can obviously tell what and where the capacitors are. But, I don't know really how the flow on the board gets us from rectified DC to the output voltage of 2.9v and how to tamper with it to change the voltage in any fashion.

Linear vs switching regulator https://www.youtube.com/watch?v=rfChSvb8FX0

another video https://www.youtube.com/watch?v=giGRrODKJSE

https://www.youtube.com/watch?v=3j7pGHA11rw

Giant hint, we are using switching mode regulator to not produce a ton of heat in an accessory when performing a HUGE voltage drop from say 18V down to 2.9V out. Basically a linear regulator is a voltage divider with feedback control. Just a huge waste of energy to get a large voltage. drop making it impractical.

Again, switchmode- the chip and the inductor are how and why it drops all that voltage and no heatsink required.

VS the old way- a bunch of huge resistors and heatsinked regulator wasting all that energy as heat.

@Vernon Barry, great post, thanks! I'll be watching the videos in the morning- should be in bed already but the wife decided she was going to change out the fitted on the bed at 11:50 EST...

On this board, the inductor is L1 and the chip U1? Also, what are C3 and C4? Additional surface-mount capacitors?

@Andrew B. posted:

@Vernon Barry, great post, thanks! I'll be watching the videos in the morning- should be in bed already but the wife decided she was going to change out the fitted on the bed at 11:50 EST...

On this board, the inductor is L1 and the chip U1? Also, what are C3 and C4? Additional surface-mount capacitors?

MLC- multilayer ceramic capacitors- Low resistance capacitors that can charge and discharge with little loss.

https://en.wikipedia.org/wiki/Ceramic_capacitor

Class 1 ceramic capacitors offer high stability and low losses for resonant circuit applications.

Following back up on this, I purchased a motor listed as a Mabuchi RF-300CA-12350. The closest motor I could find for comparison was the RF-300FA-12350. Not sure the difference on the lettering, but that motor has a no-load speed of 3500 RPMs, but more importantly stall torque of 2.51 m.Nm and stall current of .39 amps.

I purchased a buck converter and this motor, thinking I'd need to drop voltage in order to get comparable speed from the accessory. The motors arrived yesterday, and I started experimenting today.

The stall current on the RF-300CA-12350 is about 340 milliamps compared to the stock motor's stall of 280 milliamps. Of more consequence, this motor when operating is only drawing between 90 and 110 milliamps compared to the stock-sized motors drawing 240 to 270 milliamps. So, I have both a higher max-draw and a lower draw when operating. The motor is therefore much less stressed when running.

Also interesting, at the stock-input of 2.9vdc, I actually have a motor that runs a bit slower than the accessory as built. This isn't a bad thing- the stock motor had the miniature train display making a full revolution every 15 seconds, and this motor has the accessory doing so every 19 or so. I'm ok with that, and is actually the more desirable outcome. The buck converter won't be needed after all.

Why not just install a resettable PTC full which will limit the current draw to 100 MA in series with the motor!

Fuse: PTC polymer 100mA Ø0.51x7.6mm ERF-RN0109000Z THT polymer fuses on the bay

Alan

@Alan Mancus posted:

Why not just install a resettable PTC full which will limit the current draw to 100 MA in series with the motor!

Fuse: PTC polymer 100mA Ø0.51x7.6mm ERF-RN0109000Z THT polymer fuses on the bay

Alan

The current draw on the new motor flickers above 100 mA, and the problem was not that the current draw is going too high for the board, it's that the motor was stalling and burning out. Due to a cheap gearbox design, it was riding the knife's edge of the motor's capability. The stock motor drew between 240 and 275 mA on a motor rated with a stall current of 280 mA.

The new motor is in the same motor family, but has a higher stall torque/current, while drawing a lower current during operation and running at a slightly lower speed. At the same voltage, the new motor draws over 100 mA less than the old, and takes much more effort to stall manually. In all, the new motor is a much better choice for the accessory than what Lionel/the factory installed.