Turns out Helical Beam Couplers aren't meant to handle that much stress . . .

[Tom Line]

Generally in industrial applications the lead screw will be turned down at each end so that it can sit on a thrust bearing package. In my plant, we then drive them with a timing belt.

An easy way to do that is to get a shaft collar that fits over the threads and pin it in place. Then you don't have to machine down the end.

http://img.directindustry.com/images...84-4327425.jpg

http://gallery.nibou.com/albums/LINE...w_Supports.jpg

Your system is putting a huge amount of axial load into the motor shaft directly. They aren't made to support that type of load.

[Madison]

For FRC applications, we had success with using a coupling nut (http://www.mcmaster.com/#93023a661/=rw83fu) welded to the lead screw. The 1/2" hex interfaces well with a lot of FRC components, making it very easy to drive. We supported the lead screw on each end with thrust and ball bearings. Our lead screw was ~18" long and flexed a bit since we didn't load it evenly, but the setup did a good enough job of isolating the screw from everything else to be very reliable.

We used this in 2010 on our kicking mechanism.

[DonRotolo]

Those couplers are also not able to manage that much misalignment.

[Monochron]

The interesting challenge with building a support system for the leadscrew is that, because the leadscrew does not stay stationary as the ball holder is raised, the support system would have to be mounted only to the motor and the leadscrew itself. It might make a good off-season project.

Originally Posted by Madison

For FRC applications, we had success with using a coupling nut (http://www.mcmaster.com/#93023a661/=rw83fu) ...

Yeah, we use with one very similar to that, a little shorter and different diameter and TPI. We were bounded mostly by funding and really wanted to avoid paying $14 for the nut when the leadscrew itself was so expensive.

Originally Posted by DonRotolo

Those couplers are also not able to manage that much misalignment.

Right, it wasn't intended to. Like I said above, I added this in hopes that it would absorb some of the vibration and noise, not to make the system perfect.

[hzheng_449]

Originally Posted by Monochron

We were bounded mostly by funding and really wanted to avoid paying $14 for the nut when the leadscrew itself was so expensive.
.

Where does you team purchase beam couplings? I had the impression that helical beam couplings generally ran >$25, and I'd love to know where you can get them for less.

[Monochron]

Originally Posted by hzheng_449

Where does you team purchase beam couplings? I had the impression that helical beam couplings generally ran >$25, and I'd love to know where you can get them for less.

We got them for $6 from China on eBay. Shipping takes about a month (and is free), but as long as you plan ahead properly and commit to buying early then you can save a huge amount of money. In fact, I don't think a single fastener on our robot came from outside of China (aside from KOP and Vex ones obviously). Paying Lowes or Fastenal prices for anything other than stock metal just wasn't in the budget for us.

I'm interested to know the quality difference between the ones we got and a $45+ coupler from McMaster.

[kevin.li.rit]

You can keep the leadscrew stationary and use a simple linkage to translate the linear motion of the lead screw to a rotational motion.

[Clem1640]

These beam couplings are really good for coupling rotational sensors with drive shafts so that small misalignments won't damage the sensor. we use them in our swerve drives to couple the Magnepot Hall Effect Potentiometer which provides us with drive angle measurements for each of our wheels. These couplings are absolutely wonderful and work flawlessly in this application. A photo of the installed coupling is provided:

http://wiki.team1640.com/index.php?t...0209_csm-2.jpg

On the other hand, they won't hold up to very high torque (use Lovejoy couplings for this), massive misalignments or huge angular displacements (use flex joints here). They also cannot be used as the device which keeps everything aligned by itself.

The movie was entertaining, though.

[Monochron]

Originally Posted by kevin.li.rit

You can keep the leadscrew stationary and use a simple linkage to translate the linear motion of the lead screw to a rotational motion.

That's really awesome. Did you end up using that mechanism in your robot this year? I wish I had seen some like that at competition.

[kevin.li.rit]

Yes, that entire thing was mounted onto the robot.

https://www.youtube.com/watch?v=N_gfnubBvvU

[kevin.li.rit]

Also here is test of the tilt too.
http://youtu.be/78J20Rpzcw4?t=17s

[Al Skierkiewicz]

I know you can't see it in the video but your coupler got into a resonant mode where the parts were vibrating independent of the lead screw. When the resonance hit the right part of the coupler, the stresses increase significantly. That is why you had parts of the coupler deform more than other parts.

[Oblarg]

Originally Posted by kevin.li.rit

You can keep the leadscrew stationary and use a simple linkage to translate the linear motion of the lead screw to a rotational motion.

Oh wow, that's clever. Thanks for sharing that.