fmmjqtft's Modified Lego Power Functions XL Motor

[DLuders]

On his Brickshelf gallery, fmmjqtft posted 5 images of a modification to a Lego Power Functions XL motor. Can anyone tell what the modification does? There is no explanation or narrative on his Brickshelf post. Would you do this to YOUR PF XL motor?

[Conchas]

I'm pretty sure it disables one of the planetary gear stages, thus decreasing the overall gearbox reduction, raising the motor output speed and decreasing maximum torque available.

Perhaps the original 36:1 reduction from the two planetary stages, turns into 5:1 or 6:1 from one single stage.

These gearboxes are however quite complex, as they have several possible modes of operation, and mental extrapolations are not that straightforward...

http://technicbricks...pf-m-motor.html

Must check exactly how it behaves, as I've some of these gearboxes open at home, for a project that I never had the time to document and post...

[SuperCow]

The gears that are cut, are also glued so that they cannot turn anymore.

This second stage(cut) will turn at the same speed as the first stage.

As the cut gears are glued, the output shaft will turn as well the same speed.

Thus increasing the output speed of the XL motor, en reducing the torque.

[allanp]

It looks most certainly to increase the output speed. I would not do this to my own motors as i'm too much of a purist, but I do wish these motors did not have so much gearing down in them, it makes using them boring, partly because they are slow and partly becuase they have done the work of gearing down to get more power for you. Using the white clutch gear is also a waste of time on these motors. I much prefere using the old ungeared motor because of all those cools gears and pulleys spinning really fast! If I was to do a similar modification it would be to remove all gearing, mounting the output axle hole directly onto the motor shaft. I could probably shorten the whole motor by at least a stud by doing that too. Alternatively I could keep it the same size and put in a bigger, more powerful motor

Edited December 2, 2010 by allanp

[fmmjqtft]

The modification makes the motor 6x as fast.

The stage of planetary gearing which is modified is the one furthest from the motor. The three modified planet gears are glued onto the orange piece, and the orange sun gear goes between these three modified gears and then more glue is applied between the teeth of the sun gear.

I originally did this modification because I needed two very fast motors, but did not want to buy the RC motors, mainly because of their inconvenient shape.

If there is any question as to how strong this modification is, I did this to 2 PF XL motors 2 years ago and they have not broken.

[allanp]

I would love to see them in action!