ZIMO Brake Key - Force Progressively Applied or Not?

[pauliebanger]

Here is an explanation of the way in which the Brake Key feature on ZIMO decoders operates, and how it differs from others.

 

You may be aware that several other manufacturers have their own version of a 'brake' which serves to slow the model more rapidly than the value in CV4 would normally allow.

 

High values in CV4 to adequately simulate the high momentum in a heavy train results in long duration coasting, but can also cause difficulties in stopping at a precise location or in a specific time period.The purpose of all the braking features, including the one I designed for ZIMO, is to provide some additional control for the operator.

 

The provision of an on board brake feature, operated by an F key, allows the operator to temporarilly modify the effect of CV4 and cause the model to decelerate or to stop completely in a shorter distance or duration under full control.

 

The way that the decoder's software achieves this varies from brand to brand, as does the operational requirements.

 

In at least one brand the brake key over-rides the throttle speed step setting as well as providing an increased retardation force. Releasing the brake key allows the model to accelerate to the former speed unless the operator changes the setting before the release. This is an efective way to 'automate' the procedure to some extent, and is a legitimate way to control model trains. It does not follow normal real life practice when most of the time, the throttle/control lever/ regulator is closed before any brakes are applied.

 

Other solutions require the throttle setting to be reduced in advance of operating the brake control, ZIMO included. This more closely resembles what the driver/engineer would do in a real locomotive.

 

As far as I have been able to establish all use a simple substitution of one value in CV4 for a different, usually much lower, value. This provides for a higher deceleration rate and the model slows in a shorter distance and duration. This results from the deceleration being changed to a different rate whenever the Brake is engaged, returning to the preset CV4 figure at other times. In other words, there are two distinct but linear rates of deceleration applicable dpending on the status of the brake control. 

 

The ZIMO Brake feature, however, extends the simulation to include continuously variable and constantly increasing retardation force which progressively increases the effect such that the first portion of braking is very modest retardation and the very last portion is the highest retarding force the various CV settings will allow.

 

This ensures that, after reducing the throttle opening, a short dab of the ZIMO Brake Key will have almost no visible effect, and even a series of short dabs will not materially alter the actual road speed of the model. Longer duration applications of the Brake Key result in progressively more rapid deceleration. Releasing the Brake Key returns the deceleration to the rate in CV4 and the model will continue at this (linear) rate until either an acceleration request is received or the Brake Key is operated again. At which point, the rate of deceleration will again be increased progressively as before. Each time the Brake key is released, the duration of brake application is reset to 0 and the process of progressively increasing the deceleration force begins afresh with the next Brake Key press.

 

All this results in a braking simulation which is closer to the effect of real brakes, in my view therefore the best implementation of such a feature.

 

The diference is, perhaps, modest under some conditions, but always quantifiable. How significant an improvement over what has gone before is subject to the operator's or observer's perception, so I make no claim on that issue.

 

So yes, the retardation effect arising from each ZIMO Brake Key application is progressively increased for the duration of the application or until maximum retardation is reached.

 

Kind regards,

 

Paul

[Nigelcliffe]

Paul,

 

can you provide sample CV values which allow the progression to be illustrated.    

 

Your explanation is fundamentally different to the messages sent by Zimo's support staff which indicate that the brake key substitutes one value of deceleration for another. 

 

 

 

- Nigel