Large Scale Central

Warning! Bachmann Hopper shorted axles

General Discussion
#1

I have just found the third axle [from two cars] on my Bachmann 3-bay coal hoppers that was shorted across from wheel to wheel. The first one I found had some trackside wood bark smoldering, melted the truck journals, and tripped the circuit breaker on my power supply. Since then, I have found two axles on a second car that were shorted. When the offending wheel is removed from the axle and a battery and voltmeter test is done , there is voltage transfered between the outside of the wheel and inside of the plastic bushing at the center, to the axle. I guess the entire set of hoppers will have to be checked for conductivity across the axle and wheels. Note melted journal and pitted wheel:

Ordinarily, this would not be a problem for me running track power. However, one of my lines is track power capable for visitors. This is when the short happened. I contacted Bachmann 2-1/2 weeks ago [ 9 days before Marty’s] and got a less than satisfactory response. First there was an attempt to blame my MRC power supply. When I refuted that idea, I was told to send in the offending parts and if they agree, a replacement would be returned in about four weeks from date of receipt of my parts. The fact that I wanted to take these cars with me to Marty’s, was of absolutely no consequence. As example of better customer service, another company making Garden Train products has even given overnight delivery of replacements when there were exceptional circumstances. To those of you that run track power, I suggest that you check any of these cars you have to make sure “magic smoke” doesn’t show up on your layout. JimC.

#2

Ummm I noticed some rust on the truck screw there…its been noted previously that rust will cause a short across the rails, particularly if cars are left out in dampness where dew or even rain may flow. It might not be Bachmann’s fault but rather Mother Natures…

#3

Id like to see inside the plastic center bushing. It’s possible that rust bridged the gap between the axle ends.

#4
Bart Salmons said:
Ummm I noticed some rust on the truck screw there.......its been noted previously that rust will cause a short across the rails, particularly if cars are left out in dampness where dew or even rain may flow..
I was not aware of that possibility. I'd better watch out with my stuff. I have a few freight cars which stay outside most of the time and occasionally get wet.
#5

Jim,

I’m having trouble understanding where you found the short. Seems difficult to get from the wheel to the axle and then to the opposite wheel. Again what did you find?

Barry - BBT

#6

Barry,
There is a dead short from one wheel, through the axle, to the other wheel. I know you might think that is impossible since there is a plastic [non-rotating] bushing between the metal wheels and the metal axle. After some discussion on another site, it seems likely that a conductive trail of the [dry] graphite lube I used on the journals must have formed between axle and wheels [cars were outside]. Although it baffles the mind that this could independantly occur on both wheels on the axle, apparantly that has happened on at least three axles.

I started using the graphite to avoid dust collection when oil or greese is used to lube the journals. “My Bad!”

Another picture of a dissassembled wheel/axle that is shorted will be taken and posted.

JimC.

#7

Yea, graphite’ll do that. Its conductive, so I’d avoid using it anywhere near the axles. There’s a reason they tell you to use it to lube pickups on track power!

#8

Jim:

Very interesting situation!

You mentioned using a “battery and voltmeter test.” Do you have a Volt-Ohm meter? If so, what is the measured resistance between the wheels? What is the measured resistance between a wheel and the axle? Does careful cleaning of the surfaces of the plastic bushings raise the resistance to a usable level?

Are the plastic bushings between the wheel and the axle melted? Are the plastic sleeves over the axles melted? I am having a hard time understanding how the axle ends would melt the journals without first melting the bushings. Assuming this is heat caused by a low resistance path from the wheel to the axle, it would heat the axle between the wheels first, with heat spreading to the axle ends by (thermal) conduction. It would seem that the truck journal would be the last to melt.

I use dry graphite on my truck journals, but since I’m 100% battery powered, I haven’t seen the problem you are experiencing.

Happy RRing,

Jerry

#9

(http://1stclass.mylargescale.com/pimanjc/kitbash%20Folder/BmnWhlShortPbm-r.jpg)

Here is the promised picture of the wheel/axle. A power source was attached to the wheel. The probe of a voltmeter [in series] was placed in the center of the wheel bushing while in place. Battery voltage was shown in the meter. That voltage was then transfered to the axle, which in turn, transfered the voltage to the other wheel [around the bushing-somehow]. Jim C.

#10
Jon Radder said:
Id like to see inside the plastic center bushing. It's possible that rust bridged the gap between the axle ends.
I forgot that Bachmann wheels were a solid axle. So it looks like the graphite ended up coating both sides of the wheel bushing creating a path through the axle from wheel to wheel. I'm surprised it could carry enough current to cause the heat you experience, but obviously it did.
#11
Jon Radder said:
I'm surprised it could carry enough current to cause the heat you experience, but obviously it did.
Jon if you would like an exciting experiment. Put a nine volt battery and three or four .38 special rounds in your pocket and go for a jog.

(Disclaimer: Do not try this at home, or anywhere else for that matter!) Jack

#12

Jim,

Thanks for the findings. I have seen this before, tough to figure out, but it does happen.

Thanks again for sharing.

I don’t use conductive anything except a small amount on the back of the pickup wheels,

if track power. I lube with synthetic oils or synthetic grease.

Barry - BBT

#13

Seems like a lot of pro and cons about the graphite. Later RJD