Friday, August 8, 2008

TBs TechNuggets 07 - Inside the PF XL-Motor

Have you ever seen inside...?

A few weeks ago, Brian Davis mailed me about his photos from the inner parts of a PF XL-Motor.

This is a perfect fit for the "Have you ever seen inside...?" sub-theme under "TBs TechNugets", which I started some months ago with the TECHNIC Clutch and never returned too (except for the recent LA dissection, although not in a specific post), despite having several material in the queue to post...

Nevertheless here you have some interesting photos for the inner parts of this huge and powerful PF motor, which delivers up to 40 until it stalls [1].

For the complete picture series from the disassembling process, please refer to the respective Brian's folder at BS (despite almost every picture shown here...).
Thanks Brian to have opened one and have killed both yours, our curiosity and of course also the motor... (some other motors, should now be safe... )

Attention: Don’t try this yourself unless you are prepared to loose the motor!...
As you can see from the pictures, the disassembling process is destructive, unless you are ready to glue the parts in the end...

This info have meanwhile, also been added by Philo to complement his PF info page.
As he mentioned, realize on the dual stage planetary gear reduction.
You can even see the grease over the gears for lubrication.

Thanks for the hint, Brian!


coreyfro said...

I don't know how to e-mail Brian Davis or I'd ask him.

Can you tell me any of the relevant of the electric motor housed within? I would like to try replacing it with a stepper. I think it's about time a real Lego stepper was made.

TechnicBRICKs said...

What exactly would you like to know about the housed in motor?

I have some open, but this OEM motors does not exhibit any reference or branding.

If you want to replace the motor with another type, you'd have to open one anyway. So I'd recommend you to do that and further check what's inside.

Coreyfro said...

I intend to, but Lego says it will be the year 2020 before I can get my hands on one.

If I could just get the shaft diameter (probably a 16th of an inch) and the diameter and length of the can. It doesn't look like the screw holes are important for the mounting in the housing.

Once I have that, I can start shopping. I intend on using the motor housing, a stepper, L298 Hbridge, and an Arduino Mega to make a new robotics platform for Lego. It will take NXT Servos, Sensors, PF Motors, Hobby Servos, OEM sensors, and steppers.

TechnicBRICKs said...


The shaft diameter is exactly 2,0mm (0,0790in).
The can diameter is about 31,95mm (1,258in)
The can length is more difficult to specify because of the protrusion in the back, that fits into the housing, but you may consider 22,84mm (0,899in) end-to-end.

Don't forget the shaft includes a metallic gear that fits into the 2-stage orbital gearbox module.

The screw wholes in the can are also important to fit into the 2-stage orbital gearbox module.

Don't forget to give us news here, about your developments. ;)

coreyfro said...

Sounds like a 500 sized motor. Probably close to the characteristics of the following:

I have found 25mm steppers that might work:

There are lots of 35mm steppers that are probably too big. Obviously, regardless, new screw holes will need to be tapped.

If this unit can work, then 48 steps in to a 36 to 1 gear box would get us 1728 steps per revolution of the unit, though, doubtlessly, it would be painfully slow.

TechnicBRICKs said...

Unless you probably find a deeper one, and eliminate the gearbox or fill its space.

Good findings!

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