Found out why the pivot on our 2014 arm wasn't working

[jnicho15]

[frcguy]

Context? Is that a VersaPlanatary stage? Either way I'm impressed

[s_forbes]

Neat! I like when things break, it's educational!

Looks like a 5:1 versaplanetary stage. What motor was driving it, where was this stage in the transmission, and what did the mechanism look like?

[RoboChair]

Originally Posted by jnicho15

Nothing against your post, but I would like to make people aware of a very useful feature on imgur. Every image you upload has 7 different choices for what size to actually display via the link. You just have to add one letter to the end of the image address before the .jpg as highlighted below. On your imgur all images uploaded page, when you click on a picture there should be a window that pops up with the list of sizes below that you can select from to automatically generate the link for easy copy+paste.

Original: (what you posted) http://i.imgur.com/c4He7g5.jpg
Small Square: http://i.imgur.com/c4He7g5s.jpg
Big Square: http://i.imgur.com/c4He7g5b.jpg
Small Thumbnail: http://i.imgur.com/c4He7g5t.jpg
Medium Thumbnail: http://i.imgur.com/c4He7g5m.jpg (what I used)
Large Thumbnail: http://i.imgur.com/c4He7g5l.jpg
Huge Thumbnail: http://i.imgur.com/c4He7g5h.jpg

THIS HAS BEEN A PUBLIC SERVICE ANNOUNCEMENT.

Thank You for your time.

[frcguy]

Originally Posted by RoboChair

Nothing against your post, but I would like to make people aware of a very useful feature on imgur. Every image you upload has 7 different choices for what size to actually display via the link. You just have to add one letter to the end of the image address before the .jpg as highlighted below. On your imgur all images uploaded page, when you click on a picture there should be a window that pops up with the list of sizes below that you can select from to automatically generate the link for easy copy+paste.



Original: (what you posted) http://i.imgur.com/c4He7g5.jpg

Small Square: http://i.imgur.com/c4He7g5s.jpg

Big Square: http://i.imgur.com/c4He7g5b.jpg

Small Thumbnail: http://i.imgur.com/c4He7g5t.jpg

Medium Thumbnail: http://i.imgur.com/c4He7g5m.jpg (what I used)

Large Thumbnail: http://i.imgur.com/c4He7g5l.jpg

Huge Thumbnail: http://i.imgur.com/c4He7g5h.jpg



THIS HAS BEEN A PUBLIC SERVICE ANNOUNCEMENT.



Thank You for your time.

Additionally, when you want to share just a picture it's generally better to upload the picture to CD-Media. It has built in discussion features and makes it easier to find images as opposed to a post with an embedded image.

[cbale2000]

How on earth did you get that stage to fail in 4 different spots at the same time? And all across the pin holes. Almost looks like someone cut it into 4 even pieces.

[Cothron Theiss]

Originally Posted by cbale2000

How on earth did you get that stage to fail in 4 different spots at the same time? And all across the pin holes. Almost looks like someone cut it into 4 even pieces.

Seeing this makes me like the VersaPlanetaries even more. Their manufacturing tolerances and material consistency must be very good for all four pin holes to fail at about the same time. This is assuming that the OP exceeded the torque ratings on the gearbox. I'd love to hear how this happened.

[AdamHeard]

Originally Posted by Cothron Theiss

Seeing this makes me like the VersaPlanetaries even more. Their manufacturing tolerances and material consistency must be very good for all four pin holes to fail at about the same time. This is assuming that the OP exceeded the torque ratings on the gearbox. I'd love to hear how this happened.

It's more likely that one failed, then the rest did in order.

[cbale2000]

Originally Posted by AdamHeard

It's more likely that one failed, then the rest did in order.

If one had failed before the others wouldn't you expect to see differences in the breaks or other damage elsewhere in the gearbox?

[jnicho15]

Originally Posted by s_forbes

Neat! I like when things break, it's educational!

Looks like a 5:1 versaplanetary stage. What motor was driving it, where was this stage in the transmission, and what did the mechanism look like?

It was a 2-stage VP driven by a CIM (pre-CIM Converter). This then drove the sprocket in the middle of the picture through a chain reduction which then rotated the whole arm. We had many failures during the season with this gearbox, and in this case the output stage failed.

[s_forbes]

Originally Posted by jnicho15

It was a 2-stage VP driven by a CIM (pre-CIM Converter). This then drove the sprocket in the middle of the picture through a chain reduction which then rotated the whole arm. We had many failures during the season with this gearbox, and in this case the output stage failed.

Do you know what the reduction was for the other stage by chance?

Vexpro has a fantastic user guide for their versaplanetary gearboxes that shows what load rating you should expect the gearboxes to withstand. I bring it up every year when we're designing to show the students that there is a limit to what the gearboxes can do. It's an excellent example of "here's what the supplier says their product can handle. We have to stay in that range or it might break".

I also try to make sure that our versaplanetary assemblies have the highest reduction stages near the motor, and not the output shaft. The lower reduction stages have more meshing gears and should be able to handle higher torques, so they are the ones you want at the output of the gearbox.

By the way, I have to mention that with the beautiful carbon fiber tube and aluminum clamp construction that your team uses every year, I'm not surprised that the gearbox was the weak point. The construction of your mechanisms looks really solid!

[jnicho15]

Originally Posted by s_forbes

By the way, I have to mention that with the beautiful carbon fiber tube and aluminum clamp construction that your team uses every year, I'm not surprised that the gearbox was the weak point. The construction of your mechanisms looks really solid!

Looks can be deceiving...

[Ian Curtis]

Originally Posted by s_forbes

Vexpro has a fantastic user guide for their versaplanetary gearboxes that shows what load rating you should expect the gearboxes to withstand. I bring it up every year when we're designing to show the students that there is a limit to what the gearboxes can do. It's an excellent example of "here's what the supplier says their product can handle. We have to stay in that range or it might break".

For us, this always ends up as: "Here's what the supplier has rated their product for. We've had some requirement creep, so we're going to assume they did their homework and eat into their safety factor."