Back shaft on RS-770/775 or RS-550

[pavie]

Hi,
We are looking for 770/775 or 550/540 motors (anything compatible with the PG planetary gearboxes from AndyMark) that have a back shaft (for encoder installation). All we found is a 540 at BaneBots (here). Any pointers would be appreciated.
Thanks!

[Ether]

Originally Posted by pavie

Hi,
We are looking for 770/775 or 550/540 motors (anything compatible with the PG planetary gearboxes from AndyMark) that have a back shaft (for encoder installation).

Is this for non-FRC-competition use?

[pavie]

FRC use.

[MichaelBick]

Most encoders are not going to be able to handle 15,000+ rpm. This is the US Digital one that I've heard most people use and even the ball bearing version cannot handle anything above 15,000 RPM, which is less than the free speed of the banebots 775s/550s motors. I would recommend that you put the encoder on the final output shaft because it is easiest for the programming team.

[pavie]

We use custom discs that handle these RPMs (and more:-) fine. We need it on the back end due to other design considerations and accuracy.

[Ether]

Originally Posted by pavie

FRC use.

Here are the 2012 FRC legal motors.

Are you thinking that a 775 with backshaft whose part number is not in the list would be legal under R48-I ?

[pavie]

Don't know - hence the question :-)

[Ether]

Originally Posted by pavie

Don't know - hence the question :-)

Hopefully now that the intent of your question has been clarified you may get some answers from persons who have some insight into the interpretation of R48-I in your situation.

[ksafin]

As Michael said, I'd suggest sticking to putting encoders on the output shaft of whatever gearbox you're hooking this puppy up to.

Tolerable RPM, and there's lots of easy ways to hook up an encoder to these gearboxes (generally).

[Ether]

Originally Posted by ksafin

As Michael said, I'd suggest sticking to putting encoders on the output shaft of whatever gearbox you're hooking this puppy up to.

pavie stated the following in an earlier post:

Originally Posted by pavie

We use custom discs that handle these RPMs (and more:-) fine. We need it on the back end due to other design considerations and accuracy.

@pavie: what is the intended application? and what "design considerations" and accuracy requirements are driving the requirement to put the encoder on the back end? If you provide more insight into what you are trying to accomplish, you may get more targeted answers.

[AlexH]

https://www.surpluscenter.com/item.a...tname=electric

for non frc applications

[Cory]

If anything you want to locate the encoder at the worst possible point for accuracy. Any slop, backlash, etc is all downstream of your encoder and cannot be measured.

[Ether]

This is why I am prodding the OP to provide more detail about what he is trying to accomplish.

[kaliken]

Originally Posted by Ether

This is why I am prodding the OP to provide more detail about what he is trying to accomplish.

It almost seems like he is attempting to direct drive something. I noticed he mentioned that he is looking for a motor that can directly attach to a PG planetary gearbox.

Originally Posted by pavie

(anything compatible with the PG planetary gearboxes from AndyMark)

So if he is indeed directly driving the actuator, he has no where to mount an encoder on the output shaft.

My thoughts, either a pass through encoder (e.g. an US Digital E7P with a pass through cover) or you may need a simple driven shaft with an offset encoder.

Again like mentioned before, if you keep the encoder position you originally are planning... position accuracy will suffer due to gear backlash, slop. It will be tough to compensate for as the true position is technically unobservable with an encoder before the gearbox.