How to slow down a Lionel Trolley

[trainlivebob]

Hi folks,

I have an issue with two Lionel trollies running on the same track with stop and go track sections.

The one trolley is a 6-18404 from the 80s that has a geartrain different than the PW #60 trolley which runs very slow.

By themselves they are no problem, but when I run them on the same loop and thus the same voltage, they will not keep in sync with my stop and start track sections.  Im thinking the best way to make them compatable is to slow down the newer one by reducing the voltage to the motor.  I would need to fit the electrical components inside the trolley.  It would have to be reduce about 2 or 3 volts. resistors sound like they could reduce the voltage but would generate a lot of heat.

Can anyone tell me how to do this and provide a bill of material, or description?

Thanks, Bob

[8ntruck]

You can use bridge rectifier to drop voltage when wired in a certain way.  Each one will produce a voltage drop of between 1 and 2 volts.  Seems like you could mount one or two in your trolley to modify the speed. When I used this method to reduce voltage I'm a downhill section of my layout, Radio Shack was still in business - that is where I got the bridge rectifiers.

Unfortunately, I don't remember the details.  Lionelsoni, one of the forum members, provided directions to do this several years ago.

You might be able to do some sort of search on the forum to find this.  I'm not as active on this forum as I used to be, so I can't be of much help with this.

Good luck and sorry I was not more help.

[trainlivebob]

OK, thanks, Ill do a search to see if I can get the details

[lionelsoni]

Connect two diodes in anti-parallel, that is, with each diode's cathode connected to the other diode's anode.  Wire in series as many of these pairs as you need for the desired voltage drop.  Figure on about 1/2 volt for each pair.

Or use bridge rectifiers.  Connect the + and - terminals of each bridge module together.  This is equivalent to two of the anti-parallel pairs described above.  You will get about a 1 volt drop between the two ~ terminals or 1/2 volt between the + and - terminals and either one of the ~ terminals.

[trainlivebob]

lionelsoni

Connect two diodes in anti-parallel, that is, with each diode's cathode connected to the other diode's anode.  Wire in series as many of these pairs as you need for the desired voltage drop.  Figure on about 1/2 volt for each pair.

Or use bridge rectifiers.  Connect the + and - terminals of each bridge module together.  This is equivalent to two of the anti-parallel pairs described above.  You will get about a 1 volt drop between the two ~ terminals or 1/2 volt between the + and - terminals and either one of the ~ terminals.

 

thanks Bob 

what do I connect the other two terminals of the bridge rectifier to?

I assume the motor but which of the 3?

[lionelsoni]

The idea is to make some number of 1/2-volt voltage-dropping gadgets that you will wire in series somewhere between the pickup and the motor.  The simplest such gadget is an anti-parallel pair of diodes.  You can also make the equivalent of two such 1/2-volt gadgets, wired in series, out of a bridge-rectifier module.  One of the equivalent gadgets is between one of the ~ terminals and the + and - terminals connected together.  The other equivalent gadget is between the + and - terminals connected together and the other of the ~ terminals.  Note that you will get a 1-volt drop between the two ~ terminals of a bridge-rectifier module (with no connection needed to the + or - terminals).

[trainlivebob]

Ok, thanks,

I have lots of bridge rectifiers on hand.  3 amp ones, and for a trolley they should be fine.

So I connect the + and - terminals of the bridge together,  and the ~ terminals get wired between the pickup wire and the motor.  If I need more than one bridge, I just put another one in series.

physically looking at my trolley I see a black wire coming from the collector to one of the motor brush springs.  So I just solder the bridge in series in this wire.  Correct?

Do they need a heat sink or can I just mount them with foam tape to the inside of the trolley shell?

Bob

[lionelsoni]

I think you've got it!  Put it any place in series with the motor circuit that is convenient.  The wire from the pickup should work fine.

The circuit will generate a few watts of heat, but it's hard to say absolutely for sure whether something as small as a trolley would be a problem.  You can feel the rectifier modules every so often at first, until you are satisfied that they're not getting too hot.

Keep in mind that you are not limited to 1-volt steps in adjusting the speed, but that you can use half of one rectifier (or a two-diode anti-parallel pair) for a 1/2-volt adjustment.

Another thing--there's no need to connect a rectifier's + and - terminals together unless you are intending to use only half of the rectifier, as for a 1/2-volt adjustment.

[8ntruck]

Bob - thanks for chiming in on this.  I remembered the technique, but my retired mechanical engineer's brain lost the details.

[trainlivebob]

Thanks Bob

I didnt realize the need or lack of regarding the + and - terminals.

Good tip one 1 V and 1/2 volt

Now on to the soldering iron.

Bob

[lionelsoni]

You're welcome.

I would be interested to hear from (the other) Bob, to know how it worked out for him.  If there's anything I learned in my (electrical) engineering career, it's that it's true, as they say, no news is good news--you will only hear about it if your design doesn't work.

[trainlivebob]

I learned that I did need to connect the + and - terminals together. 
when they were not the trolley was dead.  I thought I would need 2 bridges (2V)

but with two it was more like 4V drop

so ended with one bridge. It slowed it down and matches the other trolley on a straightaway. It works well after it get going but can't start up fast enough on curves. So ende up with another problem. 
syncing 2 trolleys on one track is tough!!

[lionelsoni]

Sure enough, the + and - do have to be connected.  I don't know what I could have been thinking about.  Sorry about that.

How did you measure the voltage drop?  I would have said that the right way is to use a true-RMS voltmeter to measure the track voltage and the motor voltage separately and then subtract one reading from the other.

But then I'm the guy that got the +- thing wrong. 

[trainlivebob]

I used a standard multi meter on the track.

I got a baseline speed at a voltage for both trolleys. Then I lowered the voltage on the fast trolley to match the slow trolley baseline speed.  That was a 2 volt drop.

But 2 bridges wouldnt hardly move the trolley when the slow trolley was at speed on the same track.  just took out the bridge and it matched speed.  So I just inferred the voltage drop from the bridge.

Bob