Spectrum 4-8-2 Electrical Question

[mechengr]

I have a fairly new (less than 1 yr old) Spectrum 4-8-2 Heavy Mountain. Having some problems with "unscheduled" stops and starts. I need some simple, plain explanation of how the "track-to-engine" power system functions. I am having an extremely difficult time understanding and getting a grip on how this works on this locomotive.

I know that each of the 8 drive wheels of the locomotive has a wiper to conduct electricity. I know that the tender also has a wiper on each axle to conduct electricity.

Apparently it is necessary to have a wiper on each drive wheel and to be certain that each wiper is, in fact, making good contact with it's drive wheel before the locomotive will run reliably. If one or more wiper isn't making contact, the locomotive stops and starts erratically or may not run at all. Why is this "all-wheel-contact" necessary? It seems to be "saying" that all 8 drive wheels must be in contact with the track at all times in order for the locomotive to run. It seems like this is overkill and makes this locomotive very "picky" about electrical contact.

I read on a previous message that one way to check the connections between the locomotive and tender is to keep the tender on the powered track while lifting the locomotive off the track. If the connections are good (mine are), the locomotive drive wheels will turn. If this electrical power for the motor is supplied from the tender, why is electrical power thru the locomotive wheels necessary (and critical) in order for the locomotive to run, as long as the supplied tender is used with the locomotive?

Will greatly appreciate any guidance/clarification on this.

[Atlantic Central]

Even with sprung drivers it is common for wheels of model steam locos to loose contact with the rail from time to time. The idea is, if all the wheels pick up power, when one or two are not in contact, the others will be and vise versa.

It sounds to me like your problem is not the driver wipers. These locos also pickup power from the tender and this can be a much better contact than the drivers, BUT, the proper arrangement of the wiring harness to allow free movement of the tender and the loco will effect electrical pickup.

To solve this problem I add weight to the the tenders (about 2-3 oz) of all my Bachmann Spectrum locos and in the case of the Heavy Mountain I modify the drawbar to allow more room for the wires. To do this I carefully bend a "dip" in the drawbar, close to the loco end, right below the plug/socket location.

Conflict between the loco and tender because of the wires will lift some wheels of both the loco and the tender off the rails and result in the kind of problem you discribe.

Sheldon

[ta152h0]

If I may pipe in here, I had similar problems with my 4-8-2 HVY MTN and discovered my track wasn't perfect, the rail joints were not smooth and some  rail joiners were loose, and a few were actually pushed under the adjoining track. After reapairing all the joints and sanding smooth the offending rail tops, the locomotive runs fine without bucking itself off the electrical contact.. Just another day

[Joe Satnik]

Dear MechEngr,

You need an Ohm-meter, and you need conductive lube.   

You can buy a Multi-meter for a reasonable price at a tool store such as Harbor Freight.  If there is a "zeroing" adjustment for Ohms, learn how to use it. 

Put the engine and tender upside down in a padded cradle with the wiring harness connnected.

Clean, then apply a small amount of conductive lube between the pickups and the wheels.  If possible, work it in.     

Using the Ohms x 1 setting, probe from one left wheel to all the other left wheels.  Every wheel on the left side with a pickup should show a "low Ohms" connection to any other left wheel with a pickup.  A "low Ohms" connection should be 1 ohm or less. 

Repeat the process for the right side.

"Open" (no connection) readings indicate wipers not making contact with the wheel, bad (loose, broken, poorly soldered, miswired) internal wiring, broken wiring harness, or spun tender trucks.  Some wheels by design don't have an electrical pickup..   


There should not be a "low Ohms" connection between any left engine wheel with a pickup and any right tender wheel.

There should not be a "low Ohms" connection between any right engine wheel with a pickup and any left tender wheel.


If you have a DC control engine (not DCC) you should be able to see the resistance of the motor (10 to 20 ohms?) between any left and right pickup wheels in the two tests above.  DCC should read higher.

If you see a "low Ohms" connection (1 ohm or less) in either of the above two tests, you probably have a "spun" tender truck.  Spin the offending truck 180 degrees on its bolster to correct. 

Mark the underside of the tender to indicate the correct orientation of each truck.     

Hope this helps.

Sincerely,

Joe Satnik       

[Ozzie21]

On The heavy mountain if you remove the trailing truck from the locomotive you will see two copper wipers that contact a small pcb. These are from the drive wheel pickups and over time the ends can become oxidised and so become a poor conductor. If your good with a soldering iron you con solder the individual ends to their contact pads on the pcb. Ensure that you do not bridge the gap between the contact pads on the pcb or the factory smoke may escape.

Charles Emerson
Queensland
Australia

[mechengr]

gentlemen - Thanks for the replies and suggestions. I've been away for a couple of weeks, so haven't gotten to checking out the possible solutions yet.

Joe - can you give the name of a conductive lube to use.

Thanks again.

[trainmanchris]

 light mountain isthe same(power pickups)but it runs great.....

[Joe Satnik]

Dear ME,

Here is Bachmann's:

http://www.bachmanntrains.com/home-usa/products.php?act=viewProd&productId=1086

You could also Google "conductive lube" or "conductive lube hobby" or "Bachmann 99981"

Hope this helps.

Dear All,

Does anyone have a favorite source for Bachmann Conductive Lube # 99981 ?  Thanks.

Sincerely,

Joe Satnik

[Yampa Bob]

Mechengr,

Poor trackwork, dirty spots on rails and wheels, passing over insulated frogs at turnouts, cause momentary interruptions in current flow, ranging from reduced current to no current at all.  Redundant pickups let the loco float over the bad spots and maintain the current to the motor.

For strictly DC operation, slight interruptions won't hurt anything, other can cause erratic operation.  However, a DCC decoder requires a more critical and constant  current flow, so pickups are also added to the tender wheels.

[Jim Banner]

Mechengr, you asked why all wheel pickup was necessary.  I just posted on another thread why all wheel pickup is desirable and gave some figures to show how desirable.  It also illustrates how great an effect a little bit of dirt can have.  You might want to click on the link below and have a look.

http://www.bachmanntrains.com/home-usa/board/index.php/topic,6223.0.html