pic: Two-speed low profile gearbox + PTO

[Aaron Ng]

I think I see what you are talking about: those shafts that have the gear directly driven by the CIMs.

hmmm. This is gonna be kind of hard to describe without a cad model in front of both of us, but there is a spacer right in front of the 60t(?) dog gear. You can flip the placement of the larger and smaller dog gears, put a thin gear from sdp-si on the hex output where the spacer currently is, and have it be geared 1-1 to an encoder on the inside of the plate. That way it cant ever be destroyed, and it will always be 1-1 with the output, since it is driven by the output shaft.

But that would require a lot of repositioning of gears, as well as requiring a small gearbox plate dedicated to mounting an encoder. Perhaps too much work for something that can be mounted elsewhere with relative ease?

just my two cents.

also, is that a versahub that is on the dog gear for the PTO? the part says vex, but searching up the ID gives a gearbox

[RobotsThatWork]

Ok then if the plates are the same, don't bother making another configuration. Not worth the effort.

Also, is there an advantage to putting the encoder on the gearbox itself? I feel like putting it on a wheel shaft yields more accurate information for coders to determine stuff like distance traveled, etc. since its reading how much the wheel has turned, which directly determines how far you are moving. no math involved(which leads to slight inconsistencies with whats expected vs. whats actually happening). Thoughts?

[Naveed Riaziat]

Originally Posted by RobotsThatWork

Ok then if the plates are the same, don't bother making another configuration. Not worth the effort.

Also, is there an advantage to putting the encoder on the gearbox itself? I feel like putting it on a wheel shaft yields more accurate information for coders to determine stuff like distance traveled, etc. since its reading how much the wheel has turned, which directly determines how far you are moving. no math involved(which leads to slight inconsistencies with whats expected vs. whats actually happening). Thoughts?

The only issue with mounting it on the output shaft is that its often more difficult to get a secure mounting that wont wobble or come off (ie look at our 2015 robots drivetrain encoder). Of course there has been some talk of using a follower wheel so that it accounts for slipping, but not much research has been done into that.

What has been done, however, is mounting a small 3d printed gear on the back side of the output shaft, between the piston and the gearbox plate. Taking a look at the CAD, you seem to have enough room on the shaft itself, but depending on the mounting, the encoder might end up very close to the ground.

[asid61]

The debate on whether encoders should be placed in the gearbox or on the wheel came up recently in another thread. In the end I took away that placing it in the gearbox is both safer and gives less backlash (thus is easier to apply controls to).
You could put something like an S4 encoder on the end of nearly any shaft in the gearbox it seems. Just put a hole in the end of a shaft and add a set screw.

[KohKohPuffs]

Originally Posted by asid61

The debate on whether encoders should be placed in the gearbox or on the wheel came up recently in another thread. In the end I took away that placing it in the gearbox is both safer and gives less backlash (thus is easier to apply controls to).
You could put something like an S4 encoder on the end of nearly any shaft in the gearbox it seems. Just put a hole in the end of a shaft and add a set screw.

Mmmm... not really because of the aluminum box tube that the gearbox is mounted on. Also, I still don't like the notion of placing the encoder on the front plate, where... wait, we have bumpers this year, so hopefully those might provide protection from manipulators from other robots.

But don't forget the shifter pistons on the other side; there are two of them since this is dual speed and PTO. I could perhaps do the idea where we use small gears to connect the output shaft to the encoder. Perhaps use a shoulder bolt as a shaft for the driven gear.