probably a lot of you have (or have had) trains that sound like a trapped bumble bee...

is there any way to stop them sounding like this?

are there any cv values to do with motor control for example that can be adjusted?

i have 2x class 150s and 1x class 142 and they basically run ok, I'm not unhappy with the smoothness or anything, (they are all well run in by the way), they sound fine at very low or very high speed, but at mid speeds they sound really annoying... its just such a horrible noise, not at one pitch, but exactly like a trapped bee...

i realise this is a minor problem as they do all run ok but the noise is just bugging me!

i have checked and no actual bees are trapped in the dmus by the way.

cheers


tim

Sadly several of my Dapol locos (both steam and diesel) whine quite loudly, as do my Farish later model class 31 and class 25. The older the loco the more quiet they are
I have others so quiet/smooth I lose them on the layout!
Oh, this is on DC BTW

NO BUMBLEBEES WERE HARMED DURING THE MAKING OF THIS THREAD.

As you mention CV values, I'm assuming DCC control...
On analogue DC control, that sounds typical of using an unsuitable feedback controller. (The standard solution is to replace with a more suitable controller!)
I'm not an expert on DCC programming, but I believe there are settings on some chips which provide for a feedback like output to the motor.

thanks for the replies so far!

hi nobby - i guess i am lucky to just have 3 buzzy trains then!! i dont mind loud runners its the buzzing at variable pitches that does my head in!

hi pld - are you referring to back emf? I've never tried adjusting this before but might give it a go.


cheers


tim

Quote from: bluedepot on November 01, 2021, 07:07:28 PM
hi pld - are you referring to back emf? I've never tried adjusting this before but might give it a go.

I'd have thought more to do with the PWM frequency chosen rather than BEMF as such.   

Old decoders (last century ) used to drive the motors with quite a low frequency PWM which was very "buzzy" much like running a loco on half-wave on an old H&M controller.   Modern decoders tend to use rather higher frequencies eg. 16KHz which if anything may "sing" rather than "buzz".  There's usually a setting to select the PWM frequency.

Back-EMF is related to the "load control" or "constant speed" function which senses the motor rotation by sampling in between the PWM pulses and uses a negative feedback algorithm to try and keep the speed the same (within reason).  Different types of motor generate different amounts of BEMF (for example coreless motors less than traditional iron core) so some decoders will have settings to change the "tuning".  In my experience badly tuned feedback control tends to result in jerky running rather than noise.

hi

thanks that makes sense.

my class 142 has dapol imperium decoders in it. i don't think these have a cv to adjust pwm frequency - at least not mentioned in the instructions...

any ideas?

cheers

tim

Quote from: bluedepot on November 01, 2021, 08:18:56 PM
hi

thanks that makes sense.

my class 142 has dapol imperium decoders in it. i don't think these have a cv to adjust pwm frequency - at least not mentioned in the instructions...

any ideas?

cheers

tim

Ask in DCC thread?

Quote from: bluedepot on November 01, 2021, 08:18:56 PM
hi

thanks that makes sense.

my class 142 has dapol imperium decoders in it. i don't think these have a cv to adjust pwm frequency - at least not mentioned in the instructions...

any ideas?

cheers

tim

Use Zimo decoders instead   

John P

yes i suppose i could try different decodee

it just came with dapol imperium in it

cheers


tim