I’m working on a practice WCD CAD and am using the WCP SS gearbox and would like to use an encoder. How can I mount an encoder to the live axle over the sprocket? What encoder would be best used in a drive-train? I searched CD but I couldn’t find anything specific. Pictures would be great, thanks!
We pressfit a piece of 1/4" aluminum round stock into the back end of the output shaft on our WCP gearboxes, then used some 3M double sided tape and zip ties to secure AMT103-V encoders on. It sounds a little sketchy but it held up to 50+ matches. The AMT103-V fit perfectly in between the 2 CIMs. You might also able to 3d print a better bracket for it. I’ll PM you photos if I have any.
We built a test WCD chassis this off season using WCP SS gearboxes. We mounted CTRE Mag encoders in a similar way to 254 seen here. We made the mounts in about an hour and its very easy to get the right gap by simply adjusting the standoff length.
Optical encoders (such as the AMT103-V from DigiKey as mentioned before) are the way to go, as they provide the greatest accuracy. If you have a lathe, trimming down the thunderhex output shaft with a 3d printed mount is your best option.
If you do not have a lathe, you would be better off using magnetic encoders from CTRE and 3d printing a mount for it on the back of the shaft. This is what I did in the past when I was a student on a low-resource team. Mag encoders are less precise, but are much easier to integrate for this kind of team, and there is a recent thread that goes into some details of this. Another thing to look into if you want to find a lathe is FIRST Help Hubs. There might be a team in your area that can help you out.
If you do not have a 3d printer, I suggest for the future to use one of the AndyMark gearboxes that are built to use COTS parts to mount encoders.
For something to check out (although I have never used it myself) the CIMcoder could work with using your gearbox, however it would be measuring the first stage instead of the output, which is not ideal for your programmers.
where did you get that picture. would be nice to see more close up picture of 254
Considering the domain is “media.team254.com”, I’m going with “somewhere on their website though it’s hard to pin down exactly where just from the URL”.
We 3D printed hex bore versions of vex’s versa planetary encoder. https://photos.app.goo.gl/Q3TSOOzymxGFmjSh1
It’s from their 2017 build blog.
You might also like Pat Fairbank’s 2013 and 2014 build season albums.
I’ve read that a lot of competitive teams (I think 330 but don’t quote me on that) simply connect grey hill encoders using a small length of surgical tubing and some zip ties as a coupler. The low forces involved make this a very quick and reliable method, plus your encoders don’t have to be colinear with your shaft. We had success with this in the offseason. Our encoders were simply floating supported by nothing more than the stiffness of the surgical tubing. We used a piece of tape to stop the encoder from spinning in place. I’ve heard that a well zip tied wire can even replace the piece of tape. To be safe a quick bracket could solve all the “red flags” this method has. But after a season of destroying 3D printed encoder mounts and encoders that were not perfectly aligned, I thought this method worked great.
Lots of teams have success with the surgical tubing method. I personally have not. Clearly I did something wrong, but the lack of robustness of the method makes me prefer helical couplers for encoders.
Is the surgical tubing accurate? And if so, can the encoder just be ziptied to the belly pan? (Does the greyhill work with the Talon SRX?)
We found surgical tubing to be positionally accurate, but the flex in the tubing results in problems for velocity readings. Our testing found some weird oscillatory behavior in the encoder velocity readings when using surgical tubing.
Of course, YMMV based on the particular type of surgical tubing you use and other factors.
We’ve used a short section of pneumatic to make an encoder connection, too.
It’s stiffer than surgical tubing and doesn’t oscillate.
If you use VersaBlocks for your WCD, something similar to this may work for you.
Just like Mark, we also use pneumatic tubing to connect the encoder to the live WCD axle.
I was planning on using a WCP bearing blocks so we didnt need the cam tensioner. Thanks for all the reccomendations. How do you connect the tubing to hex shaft?
This is super cool! Are you willing to share the files for it? We used your last model for a hex adapter multiple times last year.
One way that we’ve done it is by turning down about a half inch of the end of the shaft to a diameter that will give you a nice friction fit with the tubing, then a ziptie over it to ensure it can’t slip. Also, if you’re not using the cam tensioner, do you have any way of tensioning the chain? That’s one of the main advantages of a WCD with bearing blocks.
+1 this looks awesome.
I think I’ve attached what I have so far… Let me know if you can open it. I added a square slot to allow the bearing blocks about .15 inch of travel to tension, loosen bolts - slide, then tighten down. If there’s an easier way of doing it, please inform me. (This is practice for a reason…)
CD.zip (2.45 MB)
I think the issue you’re going to have is that the bearing blocks will slide. No matter how hard you clamp them down, they’ll move around under hard hits. This year, we used VEX bearing blocks and WCP cams, but had a “floating” bearing block in the middle of our drivetrain (the gearboxes were at the back, bearing blocks in the middle and front) and only the front had cams. The middle bearing block was held in place with the clamping screws but it would need to be adjusted every few matches. I think you can use the WCP cams with WCP bearing blocks and I would recommend using them as a hard stop for the bearing blocks. You may also find it easier to use the VEX bearing blocks as they don’t require slots (just an oversized hole that needs way less precision) and imho have better bearing retention.