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Offline revmox  
#1 Posted : 17 June 2022 07:03:57(UTC)
revmox

Australia   
Joined: 26/05/2021(UTC)
Posts: 58
Location: Australia, East Maitland, NSW
DC wheelsets have been covered in this forum before but the information is spread across a number of posts. I’ve just modified some carriages so I’ll put what I found into one post and maybe that will help some other beginners.

Marklin has its own unique wheel standard called NEM 340, most of the “normal” manufacturers seem to use NEM 310 as a base. Wheelsets made to NEM 340 are often called AC wheelsets to reflect Marklin’s original 3 rail/stud track and AC power system while the others are called DC wheelsets.

Here’s the standards in German from https://www.morop.org/index.php/en/.
nem340_d.pdf (41kb) downloaded 2 time(s).
nem310_d.pdf (68kb) downloaded 0 time(s).

If you’re a Marklin user that doesn’t sprechen then this online German to English pdf translator can be handy https://www.onlinedoctra...german-to-english_de_en.
Here’s the standards translated.
nem340_d.de.en.pdf (88kb) downloaded 9 time(s).
nem310_d.de.en.pdf (128kb) downloaded 10 time(s).

As can be seen in the following picture showing Roco DC vs Marklin AC, the major differences are that DC wheelsets have a shorter axle, a narrower tread as well as a lower, sharper flange. Obviously, DC wheelsets must be insulated.

AC-DC.JPG

This difference means that DC wheelsets sometimes have running problems on Marklin track, particularly going through point work. Here’s a slow motion video of a six carriage test train going through a Marklin 24671 curved point. The first three carriages have standard Roco DC wheelsets and can been seen to catch on the nose of the frog and bounce up - making quite a racket in the process. The second three carriages have been modified and can be seen to pass through without much drama.

Slow Video 10MB.mp4 (10,677kb) downloaded 27 time(s).

Clearly the best fix for this problem is to replace all DC wheelsets with the correct AC wheelsets. However, the high price and poor availability of the correct AC wheelsets has meant that some people have found a workaround by simply reducing the spacing between the wheels, called the back to back measurement, by 0.5mm. For the Roco DC wheelsets I have that means a reduction from 14.3mm to 13.8mm. The wheels are a push fit on the axles and are not that difficult to get to move. However, getting them to end up at exactly 13.8mm apart and guaranteed to still be “square” on the axles is maybe not so easy.

With 20+ axles to do I decided to 3D print two small precision depth cups with the right recesses to take the ends of the axles. Placing a wheelset to be modified in them and giving two VERY LIGHT taps with a hammer can quickly turn out the desired result with all the finished wheels measured at 13.8 +/- 0.03mm. There are many ways the same result could be achieved. Note that this workaround still leaves the issue of the insulated wheels not operating some detection tracks.

COMBO 50.jpg
thanks 4 users liked this useful post by revmox
Offline H0  
#2 Posted : 17 June 2022 09:16:01(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 14,568
Location: DE-NW
Originally Posted by: revmox Go to Quoted Post
This difference means that DC wheelsets sometimes have running problems on Marklin track, particularly going through point work.
I don't have any problems with Roco wheelsets on Märklin C track.
I have problems with Piko and Liliput wheelsets. I slightly reduce the wheel spacing on wheelsets that have problems - with a small correction of about 0.2 mm the DC wheelsets work fine for me.

Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
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Offline marklinist5999  
#3 Posted : 17 June 2022 14:17:06(UTC)
marklinist5999

United States   
Joined: 10/02/2021(UTC)
Posts: 1,659
Location: Michigan, Troy
Me either.
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Offline revmox  
#4 Posted : 17 June 2022 23:55:23(UTC)
revmox

Australia   
Joined: 26/05/2021(UTC)
Posts: 58
Location: Australia, East Maitland, NSW
I suppose it is the luck of the draw. I have 6 of the 24671/24672 curved points on my small layout and about a dozen Roco 4 wheel freight wagons that I bought new and second hand. They all had some degree of this issue. In the slow motion video you will notice that most of the little 4 wheel Roco wagons had a 3D printed coal load. I deliberately made those quite heavy to reduce the extent that the wagons "bucked up" going through the points - without those loads there was the occasional derailment.

I bought the Roco stuff just after starting with Marklin on the very firm assurance that "Roco is compatible with Marklin". I guess it would be truer to say "Roco can be made compatible with Marklin" and that is also true for some other manufacturers.
thanks 1 user liked this useful post by revmox
Offline H0  
#5 Posted : 20 June 2022 09:20:36(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 14,568
Location: DE-NW
Originally Posted by: revmox Go to Quoted Post
I bought the Roco stuff just after starting with Marklin on the very firm assurance that "Roco is compatible with Marklin". I guess it would be truer to say "Roco can be made compatible with Marklin" and that is also true for some other manufacturers.
Many dealers will swap the wheelsets (often free of charge) if you indicate you are using Märklin tracks.
Without that information, you will get DC wheelsets that will sometimes cause problems.

I avoid 24671/2 because too much Märklin rolling stock is giving me trouble on these turnouts. Life is easier with only R2 and above.
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
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