Replacement Athearn Bombardier BiLevel Trucks, aka making the train roll

[nkalanaga]

I doubt that soldering to the bearings would damage them.  My concerns were heat damage to the frame, if the soldering was done after the bearing was installed, or the bearing being forced out of alignment if the wires didn't sit exactly right.  Very fine wire probably wouldn't exert enough force to twist a bearing, but if it wasn't rigidly attached, even that small chance would be eliminated.

Plus, by not soldering, assembly, and disassembly if needed, would be that much easier.

[craigolio1]

Peteski, the description says bronze.

Nkalanga, the plan was to solder the wire to the bushings prior to installation. The magnet wire is so thin I just can't see it putting enough strain on the bushing to move it out of alignment, but that is something I hadn't  thought of and it makes me want to use the thinnest wire possible for sure. I agree about the ease of service without the wire being permanently attached to the bushing. Thats something to consider for sure.

Craig.

[mmagliaro]

There's a flaw in your current measurements.  You cannot assume that just because you have 4 wheels on the track, each with a magnet wire to its bearing, that you can conduct 4x the capacity of the magnet wire.
There will be moments when only one of those wheels is actually conducting, and during those times, all the current will flow through one magnet wire. 

So you need to design this so that each individual magnet wire can handle the total current.

#34 magnet wire is only rated at 56 mA

[peteski]

There's a flaw in your current measurements.  You cannot assume that just because you have 4 wheels on the track, each with a magnet wire to its bearing, that you can conduct 4x the capacity of the magnet wire.
There will be moments when only one of those wheels is actually conducting, and during those times, all the current will flow through one magnet wire. 

So you need to design this so that each individual magnet wire can handle the total current.

#34 magnet wire is only rated at 56 mA

While I agree with your assessment, IMO for very short runs the wire can carry much greater current. It is all about the resistance.

Resistance of 34AWG copper wire  is 0.261ohms per foot.  The wire leads in the trucks will probably be less than 1" in length (before they are bundled together and soldered to a thicker feeder wire.  So 0.216/12=0.018 ohms per inch. From that you can calculate a voltage drop and power dissipation with a known current. I'm not going to calculate the voltage drop or power dissipation for higher current.  It's fusing current for duration of 10 seconds is 5 Amps. So I think it is quite safe to use 34AWG wire in this application.

My info came from "Tables of AWG wire sizes" section of https://en.wikipedia.org/wiki/American_wire_gauge

Craig, so the bushings are bronze.  It also solders well. If it is sintered bronze, some of the solder might soak into the microscopic voids in the metal, but I don't think that will affect bushing's functionality.  But if it is already impregnated with lubricant, it might be difficult to solder.

[craigolio1]

I won't try to use lube to impregnate the bushings until after I solder. I hope someone hasn't already impregnated my bushings.

Craig.

[peteski]

I hope someone hasn't already impregnated my bushings.

That just sounds strange. 

[craigolio1]

Haha. I know. I couldn't resist. Sorry.

Anyway. I have some extra bushings so I think I will solder one to see how that goes. I've taken apart enough of my projects because something isn't working (actually working on an Atlas loco right now that is about to have motor leads soldered to the motor tabs because it stopped working). I'm a big fan of trying make it so that I never have to get back into it and like to solder what ever is practical.

Craig

[peteski]

I'm a big fan of trying make it so that I never have to get back into it and like to solder what ever is practical.

Craig

You and me both!  Except when it comes to the wiring between the shell and chassis. I like to be able to remove the shell without having an umbilical cord connected to the chassis.

[CNR5529]

 

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So the trucks finally made it across the border, and already got their 24 hr bestine soak. Now I will procede do defuzz the prints before handing them off to Craig for testing with the bushings. We will soon know if this endeavor was worth while!

[Nick Lorusso]

Watching patiently. This might get me to by so GO Transits.

[mmagliaro]

While I agree with your assessment, IMO for very short runs the wire can carry much greater current. It is all about the resistance.

Resistance of 34AWG copper wire  is 0.261ohms per foot.  The wire leads in the trucks will probably be less than 1" in length (before they are bundled together and soldered to a thicker feeder wire.  So 0.216/12=0.018 ohms per inch. From that you can calculate a voltage drop and power dissipation with a known current. I'm not going to calculate the voltage drop or power dissipation for higher current.  It's fusing current for duration of 10 seconds is 5 Amps. So I think it is quite safe to use 34AWG wire in this application.

My info came from "Tables of AWG wire sizes" section of https://en.wikipedia.org/wiki/American_wire_gauge

....

Peteski, your calculations about how much current a short length can carry are correct.  I am more worried about how hot that little filament-sized wire will get, even if it doesn't "fuse" (burn through) in a short-circuit condition.   5A (typical booster limit) through that length at that resistance works out to about 1/2 watt of power.  That's a lot of heat for that little wire to dissipate.

I agree that it will support the required current if nothing goes wrong.  I'm still a little worried about what happens when something does go wrong.  I guess my only advice would be to try to make sure that wire doesn't touch anything plastic.

[peteski]

Peteski, your calculations about how much current a short length can carry are correct.  I am more worried about how hot that little filament-sized wire will get, even if it doesn't "fuse" (burn through) in a short-circuit condition.   5A (typical booster limit) through that length at that resistance works out to about 1/2 watt of power.  That's a lot of heat for that little wire to dissipate.

I agree that it will support the required current if nothing goes wrong.  I'm still a little worried about what happens when something does go wrong.  I guess my only advice would be to try to make sure that wire doesn't touch anything plastic.

You are correct of course. It would be prudent to  use heavier gauge wire of possible.

[Lemosteam]

Why not add a small slit for 010 PB wire to be visible in the snap pocket and when the bearing is snapped in it will make contact with the PB wire (and maintain that contact).  The pocket would need a groove for the wire to deflect into so the bearing will still fully seat. The wire would exit out the top or bottom of the truck and could have grooves to glue it in place to hide it and then it bends up like a truck tab piercing a small hole in the bottom of the car where a connector could be added or a wire soldered to that.  Red below is the wire.
________                                                     ________                                                                   
|       \  ||                                                    || /          |
|         \||                                                    ||/           |
 |         |\_____________________________/|           |
                                      O

[craigolio1]

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So the trucks finally made it across the border, and already got their 24 hr bestine soak. Now I will procede do defuzz the prints before handing them off to Craig for testing with the bushings. We will soon know if this endeavor was worth while!

Awesome work! Looking forward to phase 2.

[peteski]

Why not add a small slit for 010 PB wire to be visible in the snap pocket and when the bearing is snapped in it will make contact with the PB wire (and maintain that contact).  The pocket would need a groove for the wire to deflect into so the bearing will still fully seat. The wire would exit out the top or bottom of the truck and could have grooves to glue it in place to hide it and then it bends up like a truck tab piercing a small hole in the bottom of the car where a connector could be added or a wire soldered to that.  Red below is the wire.

Why of course! I like it!