The new 38440 UP GE ES44AC has smaller diameter AC wheel flanges compared to the AC flanges made previously before approx 2010. Marklin is trying to make them closer to the DC wheel flanges (smaller diameter) that run well on the C-tracks. They discontinued the metal M tracks. The 38440 stops on my metal M track double slip switches 5207 and 5128 because the wheel flanges are smaller in diameter and the edges are not able to make contact with the power conducting metal contacts at the bottom next to the plastic track in the switches. So the edge of the wheel flange does not touch/contact the base metal shiny (chrome colored) plate. I thought the locomotive was long enough to have other wheels touching the rails to make electrical ground contact, but that does not seem to be the case. Probably poor power contact from the other axles to the chassis for ground contact. I have adjusted the shoe but that does not appear to be the problem for power contact.

Any one have any solutions? Thanks. Half my layout is K track also, so I can only run this lok on the K track sections. C track was commercialized after my layout was laid, so I do not have C track on my layout.

Thanks Jean.

All 6 axles are grounded. I just measured them. Let me number them. From the front, Axles 1, 2, and 3 in the first bogie, and axles 4, 5, 6 in the second bogie.
Axles 1, 3, 4 and 6 are geared. Axles 2 and 5 are free turning.
Axles 3 and 4 have all 4 wheels with tires, (4 tires total on 2 powered axles), so probably cannot get power from the rails. Axles 1, 2, 5, and 6 can pick up power from the rails.
Distance between axle 1 and axle 4 is about 6 1/4 inches.
Distance between axle 1 and axle 3 is about 1 13/16 inches.
Distance between axle 1 and axle 6 is about 7 inches.

I have a section on the layout where the TWO metal M 5207 double slip switches are connected by a M track 5110 (7/8 inches long) in between. That puts the distance spacing between the centers of the 2 x 5207 where the plastic tracks are, at about 7-8 inches, so that explains why the locomotive stops with loss of power and does not have ground track rail current. I think that explains it. Both bogies are on the tracks with no rail current. I push it a little and the lights light up and it moves on.

My old ALCO PA also have 6 axles and they run fine in this area. These were made by Marklin in the early 2000s and the AC wheels had larger diameter wheel flanges and the edges of the wheel could get current from the bottom shiny metal contacts.

So it looks like these loks will only be run on my K tracks, which is fine. This lok is very heavy and has a lot (and I mean a lot) of plastic parts for details, so be very careful in handling this lok.

Again, Thank you Jean.

Hi Bill
Why not using regular current-conducting couplers for this. It may connect ground from other cars.
Re your issue I also looked at the storage capacitors Märklin 60974. They plug on the SUSI interface of the mLD3, mSD3 decoders but it seems it does not plug and plays with your loco.
Cheers
Jean

Jean thanks, I like your current-conducting coupler suggestion. Will give it a try.

Thanks analogmike. I did not realize there was an earlier version of the 5207 where the rail at the center of the double slip switch is metal. Yours matches the one shown in the Marklin 1961/62 catalog that I have. Mine matches those in the catalog 1997/98 where the 5207 is all black and all plastic in the center. So basically no rail current (ground) contact to the wheels. I will just have to run the lok on my K track.

Also, one thing I noticed, following the numbering convention I used of axles in post 3 above, I noticed that the pivot for the front and rear bogies are not above the #2 and #5 axles but above #3 and #4 axles. So, I noticed that because of the heavy nature of this lok the weight pushes down on the #3 and #4 axles, but causes the axles #1 and #6 to lift up easily of the bogies and derail on not-levelled tracks. My metal M tracks are bumpy. My ALCO PA loks have pivots above the #2 and #5 axles and run beautifully on my metal M tracks, including 5207, even at high speeds.

So I will run this lok on my K track only and be happy with that.

I agree with you Eduardo totally, that the newer marklin locomotive models are much more delicate to tolerances and that they will run much better on C track.
I do have a lot of older pre-1990 locomotives and cars that make a good clickity and clackity noise on the metal M tracks and the sound really soothes me and helps me in reducing my work stress environment when I come back home at night. My father ran these older loks in the 60s on metal M tracks and brings back good memories.