QUOTE (eddscott @ 25 Sep 2008, 18:07)
<{POST_SNAPBACK}>On these hornby/lima offspring rather than the pancake motor they've shoehorned a can motor in its place and this has one capacitor across the terminals. I cut it off and reset the CVs to default but both locos still stutter. I've left them with CV54 at 001 and CV55 at 030 and at step 1 on the powercab you can see the stutter but its quite faint and from 3 onwards its barely noticeable.
*** The stuttering you mention is the low quality motor cogging at slow speeds - its only 3 pole from memory.
I really don't think your back EMF settings are right for this motor. In particular you are minimising the back EMF assistance
Why don't you reset the bachmann decoder to default which is CV8 to 8 and do the same sort of changes I recommended to Nick - they may have the same effect for you, as they are designed to smooth the start of loco's and particularly the CV3/4/5/6 settings work to help motors that are a bit coggy.
The bachmann/esu decoder has a different number range in the CV's concerned so set as follows:
CV2 = 0
CV3 = 10
CV4 = 10
CV5 = 55
CV6 = 42
Then, if more tuning is needed play with back EMF.
When you play with back EMF change ONE cv at a time and note the effect. If you change two at a time you have no frame of reference to work with
CV53 = Determines the back EMF that the motor should supply at maximum speed. The more efficient the motor, the higher this value may be.
CV54 = Determines how strongly load control effects the motor - The higher the value, the stronger the impact on the motor.
CV55 = Determines the momentum of the motor Motors with large flywheels of large diameter require small values I suggest the hornby almost certainly needs a very high one!
first try the following: these are similar to the ESU defaults and are usually good with most motors. (ESU make this decoder)
the highest value possible in all these CV's is 64
CV 53 = 56
CV 54 = 32
CV 55 = 24
next try this (but I suspect CV54 is possibly too low)
CV 53 = 56
CV 54 = 20
CV 55 = 40
Yes... you can fiddle with CV55 a lot but only adjust in steps of 5 at a time upwards... it may need to go quite high
No....Don't at any time reduce CV54 too much - It controls back EMF effect strength and if you reduce it to a very low level, you are losing all the motor control advantage of back EMF and the quite coggy hornby motor needs the help!
Richard