Twin driving units........

[maxi-model]

Check all the wiring and skates and wheels for debris and clean. Make sure any contacts/plugs are clean and oil free to eliminate any risks of voltage drop between pick ups and motor. likewise check for any dry/broken soldered joints/wiring. Check motor commutator/brushes/retaining springs/clips are clean, oil free and carbon free between the the commutator segments. Might be the magnets in the slower motor are weakening with age and use. Re-gause ? Ensure all bearings and gearing run free and are properly lubricated. If you can remove the motor make sure the motions are not binding in any way and the "quartering" is correct.

If all this fails to fix the problem and you have been able to test each motor at identical voltages to check for RPM mismatch then you might need new motors (a matched pair). Otherwise you might be able to live with it as it is if the mismatch is not too great. Might just be normal. I sometimes run with 3 locos D&RGW style. Fastest loco at the front, middle speed in the middle, slowest at the back. No problem, keeps train from de-railing in the corners.

Max.

 

[Neil Robinson]

If possible check the current drawn by each motor block separately. With the motor turning the gears wheels and rods but lifted off the track the two should match fairly closely and be around 0.25A to 0.33A each with around 12V to 20V applied.

 

[maxi-model]

Cheers Max, paragraph one done except for cleaning the motors.

You're welcome Kim. Coming from the slot car hobby background one of the first places to go if two ostensibly matched cars no longer are, apart from the pick-ups, is the motor. Over-lubrication of motor bearings is usually the problem, oil getting on the commutator and brushes plays havoc causing carbon dust to gunk it all up and interfere with the current flow. On older cars this along with weak magnets is the problem. But no two identical cars deteriorate at the same rate !
Max.
P.S. Have you looked at the pinned topic at the head of this section ?

 

[Neil Robinson]

I reckon I can do that Neil by unplugging the back drive unit and reading the current draw on the navigator for the front drive then reverse the process.
Kim

O.K, worth a try in my opinion. It would be more accurate if any lights, smoke, sound and anything else other than the motor were turned off during the test. How will you apply power with the loco off the rails, does it have skates to clip power leads onto or have you got a rolling road??

 

[Zerogee]

Check the quartering on both units. It seems to be quite common for these LGB 6-wheel power units to slip a tooth out of quarter (happened on a second-hand Mallet I bought) which is often not enough to actually stop the unit, but enough to slow it down and make it jerky.

Jon.

 

[Brixham]

Had EXACTLY this issue with a friends analogue Sumpter...purchased in 2000, only run lightly....
A test run in 2009 showed that one bogie was much slower than the other....
A light drop of oil on the axle bearings restored normal running...both units now started at the same voltage..and then seemed to run at the same speed. A static and then a track test confirmed this...

Malcolm

 

[Neil Robinson]

Ah, IMHO the design of motor to connector arrangement on the Mallet isn`t LGB`s best example .
The track pickups and one side of the motor are the rods similar to those used on many other later motor blocks but the other motor connector is a tab. A little judicious bending of this and the tabs on the motor may be in order.

If all else fails check the copper tracks on the board as well as the wiring. If any twin bogie loco derails and at least one pickup wheel touches the opposite rail it will short out the power via the loco`s internal wiring.