Model Railway Forum banner
1 - 1 of 8 Posts

· Registered
193 Posts
Dear All,

Zimo have a way of calibrating a loco for certains speeds which is described in this snippet from the Decoder Manual :-

"For some time now a desire has been expressed to control train speeds by actual km/h or mph uni-form for all locos (i.e. 40 mph) instead of the usual speed step method (1-126), which represents a fraction of the loco-specific maximum speed. The MX620 offers this speed control as an alternative, activation with CV #135 = 0.

During a calibration run, the loco travels at medium speed for a given distance (100 scale yards). Passing the start and endpoint of this distance is registered by switching the headlights (semi-automatic procedure). CV #135 determines the conversion factor between the speed step and the actual speed. For example: if each speed step = 1km/h the speed range goes up to 126km/h; if each speed step = .5km/h the top speed is 63km/h (useful for secondary lines, trolleys, narrow gauge etc.).

This kind of control is not just for visually pleasing driving characteristics. That is the job of the BEMF load regulation. This is rather for the exact adherence to the desired speed in mph or km/h and/or the stopping distance. This new requirement is reached by constantly calculating, ad-justing and recalculating the traveled distance. The necessary data (EMF values measured up to 200 times per second) and the computing power are available in all current ZIMO decoders.

The km/h or mph speed control offers a number of operational advantages; from the strict adher-ence to speed limits (caution or 35mph …) to the trains' precise estimated time of arrival in the next station. The accuracy of this control should also bring big improvements in double or multi-traction (consisting) - although this has to be confirmed by field tests.
Activating the km/h or mph speed regulation also has one disadvantage though: the graduations at very low speeds are less sensitive since the speed steps from 0 to full speed are equidistant and not as denser in the low speed range, as is usually the case."
1 - 1 of 8 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.