Maximum Speed

[WIMorrison]

I have a loco built on wat I believe to be an Atlas v100 chassis which runs very nicely but WAY to fast.

 

I have speed curve with the maximum value at 81 but this is still a scale speed of 98kph at speedstep 28 and I want a top speed of ~50kph. I can easily cut the value to 40 and this should reduce the top speed and create the curve that is even from SS0 to SS28. My question is do you think that there will be any impact if I do this on performance?

 

I think that there wont be as the loco is fed the same by the Lenz Silver Mini, it is just that the waveform is chopped into the motor and I think I will get better slowing down/speeding up when using ~28 steps than I will using the current ~14 steps as the loco never runs at full throttle.

 

Any thoughts?

[fcwilt]

I set all my locos to be 50 or less simply to make the layout seem larger by increasing the time to get from point A to point B.

 

With a few exceptions (those with cheap decoders) they all run just fine.

 

Frederick

[34theletterbetweenB&D]

Effectively the decoder will be providing the same output at step 28 for the desired  50kph, as it does at present on speed step 14, and proportionally for all the lower speed steps. So if you are happy with the running at present there will be no change. I have genuinely slow prototypes set for their scale maximum speeds requiring CV5 to be in the range 30 to 40, and the lovely smooth performance from DCC is still present.

[Phil S]

For the same track voltage - the maximum speed in 14 28 or 128 steps will be the same.  Even backEMF should be able to make no adjustment at this level - unless the software (decoder make depedent?) atomatically 'allows' for it by reducing the top speed to allow backemf to reinstate it - extremely unlikely as flat out is flat out 8-)

 

The only decoder I have 'knowledge' of is the LGB decoder as described in the manual - from the time when 14 speed steps and even simple addressing only was standard: 2 promoted features of their decoders were (1) memory - of the last valid instruction - to help overcome data loss through dirt etc in the garden - by running on the last known value, and (2) INternal INTERPOLATION of external speed messages - from the 14 external speed steps SENT  to 1024 steps internally - so that changes from one external speed setting to another were made smoother - using the interpolation to ramp the changes from one to the next.   (Provided Acceleration and decellleration CVs 3 and 4 were not set to 0 ie instantaneous) ....With 14 speed steps the changes could be perceived relatively easily - and the effective internal smoothing of them --- this especially useful when the whole range of  INTERNAL speed values (255) is reduced to limit the maximum speed - there were still plenty of internal steps available.    EG on our shunting puzzle, we use a speed maximum of about 1/4-1/3 default maximum.  In the garden possibly 1/2 speed upward  (back in 2002 with R1 curves, the limit was set very low so that a neighbour's child would not derail the train on the R1 corners at 'full speed' ... nowadays, with larger and longer stock, the ciurves and points have been rebuilt to larger radii.  (And as of Friday - after a gap of abut 6 years - the garden line began running again on all tracks   (portable versions have preoccupied in the intervening years).   ) Of course, for some diesels and electric locos - the driver of the 1:1 version may only have a few pre-set steps with time-limits on intenrediate values!

[WIMorrison]

Custom speed ramp written with a straightline from 8 (start of movement) which is 2.4kph to 48 giving a top speed of 54kph and very smooth progression from one to the other I also found that switching BEMF OFF gave smoother control at these speeds.

 

It is the case though that the speed does seem slow, but it looks very effective pulling a train of box wagons as 40kph, this gives a real impression of the weight being pulled and it what you would expect to see prototypically. Though some people did comment at the weekend how slow the trains were running - I might speed up a passenger to 80kph so that they can see a fast train

Edited July 9, 2018 by WIMorrison