MÄRKLIN H0 conventional driving and electromechanical automatisation
The Prototype Märklin-H0-Knowledge Layout-Building Modelstock
Märklin-H0-Knowledge A: The very first basic knowlege about conventionally controlled Märklin H0 model railways A13: Wheelsets – Swapping? If so, why?
The question of whether you have to or should replace the wheelsets in non-Märklin vehicles is asked very often. The aim of this article is to collect as much information as possible about it so that everyone can decide for themselves whether the investment is worthwhile or other measures are possible. A complete list of all aspects seems impossible. Terms: The specialist speaks of "wheelset", not of "axle". You are welcome to continue to say "axle", I use the technical terms here. (Definition: An axle is stationary and the wheel is rotatably mounted on it. With the wheelset, the wheels sit firmly on the "shaft", which rotates synchronously with the wheels and transmits torque. – I hope, the technologic understanding is the same in Germany and the rest of the world…) For more information on the prototype For the basis of the model wheelset, see NEM 310. The standards cited below Now to the question of why you have to or should exchange wheelsets: There are two basic reasons that make a wheelset replacement necessary or useful: 1^st the electrical conductivity of the Märklin / AC wheelsets. 2^nd the geometry of the Märklin wheelsets. The electrical reason Märklin-H0 is the only track system in which the two rails have the same electrical function. With two-rail tracks the rails are plus and minus, with Märklin they are both "ground". Therefore, it does not initially matter whether a wheelset is conductive or not. However, if you use "contact tracks", conductivity is absolutely necessary. See the page "Tracks with Function". However, you should consider whether exactly this wagon should trigger a contact track or whether it is sufficient for the first and last wagon of the train to do so. This can save a lot of conversion work and money. The geometric reason The NEM model railway standards specify shapes and dimensions for wheels and rails. NEM 110: Tracks and Turnouts - Guiding Track Dimensions NEM 120: Rail Profiles and Connectors NEM 124: Weichen und Kreuzungen mit festen einfachen Herzstücken (only German: Switches and crossings with fixed simple frogs) NEM 127: Feste Doppelherzstücke gerader Kreuzungen (Only German: Fixed double frogs straight crossings) NEM 310: Wheelsets - Tracking Dimensions NEM 311: Radreifenprofile (Only German: Wheel tyre profiles) NEM 313: Carriage Wheelset with Bearings Pins NEM 314: Carriage Wheelset for Tip Bearings Märklin interpreted these standards very generously and often significantly exceeds tolerances. This leads to wheels with an NEM-compliant profile derailing, being inadequately guided and running onto the frog tips. Märklin wheelsets have a slightly narrower track - this avoids running into the frog tip. NEM 310 specifies 14.4 to 14.6 mm between the wheel discs. Märklin recommends 14.1 mm. To measure you need a good caliper gauge, for people with poor eyesight there are those with a digital display. The Fohrmann company offers a control gauge. The skilled craftsman can make something similar himself. It is noticeable that the Fohrmann gauge for Märklin is 13.8 mm. As mentioned, Märklin currently recommends 14.1 mm. Setting the wheelbase requires special manual skills or a suitable device. Fohrmann offers a wheelset leveller. Experienced hobbyists can also build such a device themselves. The guard rails on Märklin turnouts don't deserve their name - the distance to the rail is far too great. There are ways to improve that.
I use the steel strips from the guide of discarded windscreen wiper blades. They have exactly the width and thickness required for correcting the wheel control arms. Cut off, bend the ends, deburr and glue on.
Here I had tried to bend the plastic wheel guide, but failed and it broke off. The new guide holds with superglue. Others cut strips from old cheque cards.
Märklin wheelsets are optimized for Märklin tracks. The wheel flanges are significantly larger than specified in the NEM; that creates operational reliability.
An example: My 6-axle Roco heavy duty wagon derailed in many places. The original wheelsets: running circle diameter 9mm, point bearing, shaft length 24.7mm, metal shaft - plastic wheel center - metal tires. Since I only had 4 suitable AC wheelsets, I only exchanged the 1st and 3rd wheelset of a bogie. You can now see the differences very well. The wagon is now running perfectly.
But there are also cheap wheelsets made of plastic or with plastic wheels, which often go their own way. Plastic wheels are very light and have significantly greater friction on the rail, so they tend to climb. All-plastic wheelsets have increased friction at the bearing points. The associated wagons are also very light, because plastic wheelsets are not very resilient. The combination of metal wheelsets and ballast often results in useful wagons. The wheelsets of TRIX Express wagons are a special class. These chunky wheels jam at the first points. Replacement is unavoidable here. How do I get a wheelset out of its bearing? From NEM 313 and NEM 314 it can be seen that the wheelset shaft ends (should) have distances in the bea-rings. To remove the wheelset, press it firmly in the direction of one bearing, so that it only protrudes slightly into the other bearing. If you now bend the opposite bearing a little outwards, you can swing out the shaft end there. There are constructions in which the wheel disc jams when tilted in the base plate; then some skill is necessary ... I will come back to the topic of internal clearance below. How do I find wheelsets for Märklin? Wheelsets that are intended for the Märklin system (wheels electrically connected) can be found using the following keywords: Märklin (-axle, -axles, -wheelset, -wheelsets, -wheels) Alternating current axle, -axles, -wheelset, -wheelsets, -wheels) AC axle, -axles, -wheelset, -wheelsets, -wheels) (Running circle) diameter and (shaft) length are not always specified, but the shape of the shaft ends almost always. Leading wheelsets can only be used in the Märklin H0 system; in all other track systems they create a short circuit. Manufacturers or suppliers of wheelsets: In addition to Märklin, some other manufacturers also offer leading wheelsets. So far I have seen some from Fleischmann, Tillig, Roco, Liliput, Brawa, Piko, Rivarossi, Kibri, Trix or in stock. I have the impression that non-Märklin wheelsets are sold cheaper than the "originals". But there are also providers with pharmacy prices where you get exactly what you need. How do I describe the wheelset I am looking for? You have to determine three characteristics of a wheelset in order to find the right replacement: 1^st Running circle diameter (diameter of the running surface), because e.g. the height of the coupling and the buffer changes with the change in the wheel diameter. The brake shoes are matched to this diameter. (By the way: Since we're looking so closely - there are wagons without brakes. So don't be surprised if there are no brake shoes.) 2^nd Shape of the shaft ends, depending on the age of the vehicle 3^rd Length of the shaft, because the bearings have different distances depending on the manufacturer, although the NEM 313 and NEM 314 define them. to 1^st: running circle diameter: Basics: The running circle diameters of FREIGHT WAGONS are in the original between 870 and 923mm (found in wagonspares.com. In 1:87 this corresponds to between 10 and 10.6mm. For the running circle diameter of PASSENGER WAGONS in the original, I found dimensions between 330 and 1250mm (found in various sources). This corresponds to between 3.8 and 14.4mm in 1:87. The NEM does not name a diameter. The models have a large number of running circle diameters: So far I have met:
4,8 mm	Rolling highway
7,5 mm	e.g. Roco heavy duty wagon
9,0 mm
9,6 mm
10,2 mm
10,3 mm
10,4 mm	Märklin
10,5 mm
10,7 mm
10,8 mm	Kleinbahn, Märklin
11,0 mm	Piko, Röwa, Liliput, Hornby, Fleischmann, Lima, Jouef
11,2 mm	Fleischmann
11,3 mm	Lima
11,4 mm	Piko, Lima
12,0 mm	Märklin metal passenger coaches
(I am adding to this list as far as I discover other variants) to 2^nd : Shape of the shaft ends:
Vehicles from the time before World War II up to approx. 1958 have (often) "stub axles".
After World War II the reduced diameter stub axles appeared, called journal bearings according to NEM 313, and often also called needle bearings.
More modern vehicles have tip bearings according to NEM 314. (picture 4)
Occasionally there are also internally mounted wheelsets without protruding shaft ends, e.g. the middle wheelset of the three-axle compartment and conversion wagons. to 3^rd: wheelset shaft length: According to NEM 313, the wheelset shafts with journal bearings should be 25.5 ±0.2mm long, i.e. between 25.3 and 25.7mm. In my collection I find e.g. 26.0mm for Märklin metal passenger coaches. According to NEM 314, the wheelset shafts with point bearings should be 24.5 ±0.2mm long, i.e. between 24.3 and 24.7mm. In my collection I find e.g. 24.0mm for freight wagons from Klein Modellbahn. If you look closely at the drawings in NEM 313 and NEM 314, you can see that the wheelset shafts must be shorter than the mountings on the wagon. If this holder is made of metal, you can often adjust the distance between the bearing points by bending; you can then use slightly longer or shorter wheelset shafts. If this holder is made of plastic, you have no chance; you have to get the exact length. And that can be difficult ... Alternative to replacing the wheelset: conductive paint There is conductive lacquer containing silver. This is a clear lacquer that is mixed with silver particles. You can use it to bridge a non-conductive zone, in our case the plastic socket of the insulated wheel. The problem is that because of its weight, the silver settles very quickly. Shake the lacquer vigorously so that the silver particles are evenly distributed. If you are not quick then, most of the particles have sunk again and you have almost only clear varnish on the brush. Or you were fast enough, then the particles in the brush move to the deepest point. In my experience, the conductive lacquer method is tedious and unreliable.
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