Mechanical changes (continued)

Observations during tests

I notice derailments that did not happen before, and, curiously, rather in pulling. Well, they happen mostly in a place where the track is particularly badly levelled, but not only.

However, I deduce that my “improvements” are somewhat questionable and in any case insufficient. Probable causes are:

For the first point, as the coach height misses a few tenths of millimetre, I decide to slightly raise the bodies.

For the second point, and in conjunction with the first, I will create a three-point suspension.

And finally, concerning the third point, I decide to install conductive bearings on the driving coach, something I have already done on several vehicles: DEV U50 coaches, Est metallic coaches, three-axle Sud-Est metallized coaches, VB2N, etc.

3-point suspension

Simple and (rather) quickly done. The bogie pivots must first be given a little more backlash by digging the chassis holes, from above, to a 5 mm diameter and a depth of about 0.5 mm. This is the longest point to realize, because the body and the interior fittings must be disassembled.

The chassis is supported on the bogies by 12 mm outer diameter rings. This support is obviously far too wide to let the bogies moving freely. On these rings, I glue an Evergreen 0.25 mm thick rectangular profile, on one end lengthwise (for an almost one-point fulcrum), and on the other end perpendicular (2-point fulcrum — first photo).

Once the (cyanoacrylate) glue dries, I cut what exceeds to get four tiny supports — second picture. Do not forget to scratch the paint before gluing!

Gluing of Evergreen profile

Gluing of profile on the 2-point fulcrum end.

Cutting of Evergreen profile

Result after trimming on the (false) one-point fulcrum end. False because it is actually 2-point: it lacks the possibility of pivoting on a transverse axis.

Logically, the height of the risen coach should be increased by 0.25 mm. This is not the case: just 0.1 to 0.15 mm. It is usually the contrary: you get a higher height than expected with the spacers’ thickness, and it is easy to explain: when stacking flat objects, the height of the set is greater than the sum of the objects’ thickness, due to bad contact and flatness defects. But I just observe the fact…

Good news: such equipped coaches, launched individually at high speed, do not derail any more. Now let’s take a look at the case of the driving coach, which has its brakes permanently tightened…

Conductive bearings

For the technique, I refer you to the article already quoted. Here, the axle point housings are of rather large diameter (almost 3 mm). The bearings stamp must therefore be large enough to centre properly.

The electrical connections are made at the bottom of the bogie sides, with thin wire.

A long time ago, I replaced the original axles with ø 9 axles whose particularity is to have axes of 1.5 mm in diameter. Now, as usual, I want to get axles with isolated axes and non-insulated wheels: I have to find suitable sleeves.

Modified axle

I am fortunate to have one (and only one!) suited ballpoint pen cartridge, but I admit that I have not found anything standard on the Internet: the smallest Evergreen tube, ø 2.4 mm, has an inside diameter of only 1 mm. As for boring properly without a lathe…

The presence of sleeves on the axles makes it necessary to increase the width and height of the notches of the bogie beams: width 4 mm, depth 4 mm from the surface, see photo. This is done with a ø 4 milling bit.

View of a current pickup bogie

The insulated wheels are exchanged with the non insulated wheels of another coach, which will therefore be equipped with all insulated wheel axles. After the necessary adjustments (see drawing): shortening of the half axles so that they do not touch each other, distance between points decreased by about 1 mm, distance back-to-back of the wheels equal to the length of the sleeve, i.e. 14.4 mm, the axles are mounted and their free rotation verified.

The wires which were connected to the current pickup strips before are soldered to the connection between the bearings. The coach is reassembled, and now it runs as well as its buddies.

Test again: at full speed (equivalent to 120 km/h) as at medium speed, in pulling as in pushing, in curve of 500 mm as on a series of turnouts, the entire train now passes without flinching.

0.25mm x 1.0mm Evergreen strips
ref. 269-PS-102
€4.90 per 10 — price 2015
at micro-modele.fr

ø 9.0 mm axles LU-SPARE-9.0-24.75DC
€1.40 piece per 10 — price 2014
at micro-modele.fr