# Ball-bearing Wheels for Power Pick-up



## krs (Feb 29, 2008)

We had a discussion on mls not too long ago about the suitability of ball-bearing wheel sets for power pick-up.
Tried the mls search function, but I couldn't find the thread.

In any case, the suggestion in that thread was that ball-bearing wheel set are only usable for relatively low current applications like lighting a car but can';t be used as power pick-up for locos for instance because of the higher current.

I now came across this description of an American Mainline Diesel:
American Mainline is now offering EMD GP60 in 1:29 scale and 45mm gauge in electric. This model is constructed by brass and stainless steel chassis with removable plastic body, and *features individually powered die-cast trucks with ball bearing metal wheels*, operating directional lighting and marker lights, lighted number boards, interior cab details with lighting, clear plastic windows, brass castings, and knuckle coupler. Each model incorporates plug and play modular PC boards and electronics, built in speaker, and is DCC/RCC & Sound ready with authentic looking details such as see through steps, cooling fan, windshield wipers, and more. 

I don't have any American Mainline engines with ball-bearing metal wheels.

I wonder if anyone on mls has any and if tthey comment how long they have had the engines and if there are any problems with the power pick-up as has been suggested in the other thread.

Knut


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## altterrain (Jan 2, 2008)

I doubt the wheels have ball bearings in them (unless an unpowered axle). You wouldn't get very far that way. Maybe they meant the ball bearing axle bearings. 

-Brian


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## Greg Elmassian (Jan 3, 2008)

The product is not delivered yet and has been delayed several times. I would also expect that Brian is correct, there will be ball bearings on the axles to support load. 

So far, the American Mainline locos have been steam, and use carbon brush pickups on the loco, the tender of their first sparkie (K4) had ball bearing pickups on the tender, but their latest loco, the 0-6-0 has carbon brush pickups on all 8 tender wheels. 

(I own both of these locos) 

Regards, Greg


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## krs (Feb 29, 2008)

Looks like I may have jumped to the wrong conclusion. 

Reading "powered trucks with ball-bearing wheels", I assumed the power was via the ball-bearings but it doesn't really say that specifivally. 

Knut


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## altterrain (Jan 2, 2008)

Knut, 

I think you may have missed what I was saying. You can't have ball bearing wheels on powered axles/wheels. If you did, the loco would not move. The axles would just spin and spin and spin.... 

-Brian


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## Greg Elmassian (Jan 3, 2008)

Interesting fact is that Aristo USED to pick up power in it's new "prime mover" modular gearboxes... but they stopped, the new ball bearings on the axles have ceramic balls, so there is no conduction between the inner and the outer race. 

Power is picked up from a single ball bearing pressing on the axle with a spring, and it's not too great for a number of reasons. 

The point is that a major manufacturer used to use ball bearings for power pickup and changed, nuff said. 

(by the way, the idea of what they changed and how it was changed is good, the implementation is flawed) 

See it on my "prime mover basics" page on my site, under Aristo motive power. 

Regards, Greg


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## krs (Feb 29, 2008)

Posted By altterrain on 14 Oct 2009 02:37 PM 
Knut, 

I think you may have missed what I was saying. You can't have ball bearing wheels on powered axles/wheels. If you did, the loco would not move. The axles would just spin and spin and spin.... 

-Brian 


Brian -

Wouldn't that depend where the ball-bearing actually is?
The linkage between the loco wheels and the motor drive obviously has to be rigid, but that doesn't mean there can't be ball-bearings supporting this whole assembly and that these (theoretically of course) are used for power pick-up.

I'm not thinking of ball-bearing wheels like the LGB ones where the wheel spins while the axle is stationary.

Nobody has seen the AML GP60 yet and there is nothing similar from them already on the market as Greg mentioned, so every one's guess is as good as mine, however, since that loco has only two axles per bogie, I have a hard time believing that not both of them are actually powered in each truck which of course begs the question where the un-powered ball-bearing wheels are.


Knut


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## bottino (Feb 7, 2008)

Interesting discussion. I just built a sound car out of an Aristo two bay hopper. I was advised by someone who knows, to buy some ball bearing pick up axles. I went to Star Hobby and that's what I asked for. (Made by Aristo). I put them in the trucks, and attached wires to the pickups. The sound works just fine. The axle and the pickup tab do not turn, but the wheels turn very nicely on the axle. So do they really have ball bearings, they pick up just fine, and turn really well. 
Paul


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## krs (Feb 29, 2008)

Where the discussion in the other thread ended up was that ball-bearing pick-ups are OK for light current loads like lights but not OK for the heavier current draw of loco motors. 
Power for a sound car falls somewhere in between. 

However, I think all this depends on the actual engineering that went into the wheels in the first place including the lubricant and a number of other factors. 
I spoke to the engineer who was involved when the LGB ball-bearing pick-ups were developed and tested. Many people used these LGB ball-bearing pick-ups on the first car behind a two-axle engine to feed power back to the engine through that little connector on the LGB engines to improve operation on dirty track. The problems occurred when the engine derailed and cause a short circuit which would eventually trip the circuit breaker in the power pack. 
But the problem were not the ball-bearing wheel sets, they had no trouble handling that high current until the breaker tripped, the problem was the really small gauge wires in the engine between the motor and the power connector at the back, 
Those power connectors (which were there on LGB almost from day one) were really meant to feed the lights in the passenger cars at 33ma per bulb not handle a short circuit current when something derailed. 

Knut


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## Greg Elmassian (Jan 3, 2008)

Actually, the real problem is high current can pit the balls and races, you can put heavier wires. I know you were talking to the LGB engineer, but I'll bet he's not the ball bearing manufacturer. 

Talk to any manufacturer of miniature ball bearings about running a couple of amps through them.. then you will have the real info. 

I understand from LGB's point of view, the rest of the wiring was not designed to handle a lot of current. 

Also the lube has no bearing (pun intended) on the current carrying capability of the bearing... again ask a manufacturer. 

That said, I have several things with ball bearings to pick up power. My LGB ones are on lighted cabooses, my aristo one on a lighted caboose are fine, the ones running my sweeper car that has a motor drawing a fair amount of current have noticeably degraded they used to be perfect, now they are intermittent unless the car is rolling. 

Regards, Greg


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## lownote (Jan 3, 2008)

I'm not an EE or even close, But I've been also assuming it has something to do with how many ball bearings are drawing how many amps. I carefully reworked a lionel Atlantic so that it now has 18 power pickup points. Eight of them are ball bearing wheels. So far so good, but it hasn't been that long. Isn't the argument partly that current density through any ball bearing will be lower if there are more contact points? Rather than three amps coming through two ball bearings, three amps will be coming through eighteen points? 

I may be way off base on that though, and I've never actually measured the curretny draw on any loco. 


George's page on wheel pitting is really interesting. Reducing the current draw on a USAT loco drastically eliminated wheel pitting.


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## krs (Feb 29, 2008)

Greg - 

Which make of ball-bearing wheels are you using on your sweeper car? 

As to the lube (and I really know nothing about the design), early last year (I think it was last year), people had problems with the power pick-up of the LGB ball-bearing wheel sets. The car with the ball-bearing wheel sets would light fine just sitting on the track but as soon as it moved the lights would go out. 
That was blamed by LGB/Marklin on incorrect manufacturing related to the lubricant used. 
LGB replaced all the wheel sets they had in stock and also what was at dealers, a few cars with the defective wheels found their way to customers and were replaced as the problems came up. 
I have used many of the LGB wheel sets since without any problem, but at some point the amount of lubrication apparently caused this electrical problem. 
I could never find out any more details about it and since the problem was a one-time manufacturing issue and was resolved, I didn't pursue it - but with the LGB wheel sets at least, lubrication and conductivity are somehow linked. 
That at least was the LGB story and I really have no reason to doubt them. 

Knut


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## Greg Elmassian (Jan 3, 2008)

On base completely, although there is one fly in the ointment... Ohms law... the current through each bearing (when many in parallel) is dependent on the resistance. 

Since nothing is a perfect conductor, and there will be short term variations in resistance as the wheel turns, the current is not always perfectly evenly distributed. 

But bottom line, more in parallel will spread the load on average. Remember that not all the balls will be conducting at all times, the ones taking the load at the time will take the lion's share of the current in each bearing. Better bearings will have tighter tolerances, and SHOULD have more balls in contact at the same time. 

Only real measurements will tell. My sweeper car only has 2 axles, so that's probably the reason I'm noticing pitting now.. 

George's point is putting a resistor will help reduce the really big current draw that happens at startup/acceleration. Sort of like a big current limiter. 

Regards, Greg


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## krs (Feb 29, 2008)

Has any one ever taken one of these ball-bearing wheels apart to see exactly how they are constructed and what kind of lubricant, if any, is inside. 
I assume the LGB, Aristo, USA Trains and others could all be different. 

Knut


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## Steeeeve (Sep 10, 2008)

Apparently there is a lot of research on electric arc bearing damage. 

http://www.electrical-source.com/062008/articles/arc_bearing_motor.htm 
http://www.pump-zone.com/bearings/bearings/how-to-prevent-electrical-erosion-in-bearings.html


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## krs (Feb 29, 2008)

Interesting articles but neither one is really relevant. 
Both of these investigate the damage caused by fault currents that find their way through the bearings - here we are looking at a ball-bearing design that is meant to carry current. 

Knut


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## krs (Feb 29, 2008)

Posted By altterrain on 14 Oct 2009 02:37 PM 
Knut, 

You can't have ball bearing wheels on powered axles/wheels. If you did, the loco would not move. The axles would just spin and spin and spin.... 

-Brian 


I just remembered that a Swiss company has exactly that - ball bearing wheels on powered axles/wheels - specifically for some LGB engines to give them more pulling power.
The info unfortunately is only in German:

http://www.digitoys-systems.ch/cms/...;Itemid=27


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