Loony Claw

The Loony Claw is the first open source design from The Loony Squad. It is designed to give teams inspiration to make their own claws for the 2022-23 FIRST Power Play season. This design incorporates some key features which make it incredibly robust and reliable, as well as compatible with many common COTS and custom parts.

The Loony Claw is primarily constructed of 3D printed parts, which makes it lightweight and easy for most teams to manufacture. It only takes 5 3D printed parts to construct the most basic version. These parts are all under 120mm on their longest side, so most common printers easily fit them.

The remainder of the construction is comprised of common COTS hardware, including nuts, bolts, and bearings, as well as a servo and servo horn. The design is compatible with both a standard size servo and the Axon Mini or Mini+ low profile servos. This allows for high versatility and a variety of possible configurations.

The claw can be mounted directly to any part with a 32x32mm hole pattern, which includes all goBILDA Channel components, as well as grid plates, pattern plates, and more. Some REV and Tetrix parts are also directly compatible. There is also native support for mounting directly to a set of goBILDA Viper slides, which are in common use by teams for the Power Play season.

Nearly 150 teams are using this design, and many custom versions exist. Teams have created claws compatible with REV servo horns, versions with lengthened or thickened arms, mounts of sensors, knuckles to tilt the claw, and so much more. The community has also given the The Loony Squad lots of feedback and suggestions for improvement.

Here'es where to get access to STLs and assembly instructions: https://forms.gle/8PFMWhVr79feCkGb6

Links

CAD: https://cad.onshape.com/documents/129dc57b75a629234258d945/w/393048bd49f90455ff9c0a22/e/27d7fd42ed9d4c0cc4e530dd?renderMode=0&uiState=63acb20ee6cfd24bb7ea4020

Instructions and 3D printable STLs: https://forms.gle/8PFMWhVr79feCkGb6

Features

Mounting for any standard servo (including goBILDA, REV, Studica, Hitec, etc.)
Mounting for Axon Mini/Mini+ servos
Universal 32x32 or 32x16 mounting pattern
Herringbone-geared claws to resist twisting under load
Wide area for attaching grippy material
Bearing supported shafts on both claws
Servo protection via a bearing below the main claw
No need for a servo screw (can't fall out, so no maintenance!)
Fully 3D printed design for easy manufacturing, construction, and repairs
Common M4 hardware throughout
Fully detailed assembly instructions for all versions
Over 320 users and a strong community for support on the National FTC Discord (https://discord.gg/first-tech-challenge)
310 gram max weight (goBILDA speed servo with camera, Low-Side U-Channel mount, and REV color sensor)

Places Used

The Loony Claw has gone international! Over 320 teams from in 17 countries are using the design. Here's the map:

More stats:

States: 40 + Washington DC
Countries: 11 (USA, Romania, Canada, Australia, Mexico, Netherlands, England, China, Dominican Republic, Brazil, Greece, Cyprus, Kazakhstan, Saudi Arabia, Libya, Taiwan, and Lesotho)
Cities Outside the USA: 51

Update 1.10 (2-7-23)

This update adds overlapping claws for a more secure grip. All the grippy materials we typically recommend work well with this design. The amount of overlap is configurable in the configuration menu.

Thanks to Hunter for this idea :)

This update also replaces the nut inside the servo-side bearing with another 3D printed 8REX shaft. The hole through the shaft is 3.3mm, so it can be tapped and then a bolt can be threaded in for increased shear strength.

Update 1.9 (1-29-23)

This update adds the ability to customize the grip height of the claw. Whether your robot needs to grab right at the base, right at the top, or anywhere in between, you can adjust the claw to match perfectly. The adjustment comes in the form of a configuration input when importing the document. This input names "Grab Height" is a dimension in millimeters measured from the top of the large flange at the bottom of the cone to the bottom of the claw. The range of this dimension is 8mm to 85mm, which is the lowest the claw can possibly grab - before the cone hits the base block - to the very top edge of the cone.

This update allows for conversion of existing robots to the Loony Claw. Simply place a cone in your current claw and measure the distance from the top of the cone flange to the bottom of the claw. Then input that dimension into the configurator of the Loony Claw and export the claws it generates. Voila! You're ready to print and compete.

Update 1.8 (1-26-23)

Inspired by a design from kaavlu, we created a set of arms that allow the claw to function as a vertical intake. These claws are printed in two pieces and bolted together so each part can be made in the optimal orientation for strength. All the parts except for the claws are identical to the original Loony Claw.

Thanks to kaavlu for the inspiration :)

Update 1.7 (1-26-23)

This update eliminates the need for the 1502 series 6mm spacer that forms the axle pin for the idle arm. It is replaced by a 3D printed 8REX shaft built into the base block. This means both claws use the same 8REX bearings bearings, making for a less expensive construction.

Thanks to kaavlu for this idea :)

Update 1.6 (1-15-23)

This update is only for the silicone claw liners. After testing, we found the original liners to be too small to properly hold the cone at the base. The update increases the diameter of both the plastic claws and the liners so the final product matches the contour of the cone. If your robot grabs the cone in the top third instead of the bottom third, you may want the original smaller liners. To get these files, please email officialloonysquad@gmail.com.

Here is the official guide for creating the silicone liners: https://www.youtube.com/watch?v=xngmaokrwq0

Update 1.5 and 1.5.1 (1-11-23)

Housekeeping update:

Reoriented all STL files in the GitHub repository so they're in the correct printing orientation when downloaded
Updated STEP files of each claw assembly to include sensors

Update 1.4 (1-10-23)

This update adds a camera mount to the non-Axon versions of the claw. The servo mount and viper adapter have been modified with two additional holes to screw on the camera mount from above. The camera must be added after the servo has been installed. Tapping the holes in the camera mount is recommended, but screwing directly into them works as well.

Thanks to Sriram for this idea :)

(Also in this update are a number of changes to the CAD doc. All options are now configurable, so choosing the right version for your robot is easier than ever)

Update 1.3 (1-9-23)

This major update adds two new very useful features to the claw: an integrated sensor mount and molds for making silicone-lined claws.

Sensor Mount

We modified the servo mount bracket (for both the standard servo and Axon Mini version) to have two 4mm holes on the front. These holes are made for securing a sensor to the front of the servo with a single zip tie. The sensor is constrained vertically by the 3D printed bracket and the zip tie, and horizontally by the servo behind it and its own flange pressing against the zip tie. For additional security, a second zip tie can be passed through the sensor's holes and around the back of the servo. This solution is made to be as lightweight, inexpensive, and painless as possible, costing only a few cents in zip ties plus the cost of plastic for reprinting the bracket.

We recommend using a REV Color Sensor v3, as its short range (1-10cm) is perfect for the short distance from the sensor to the cone. It also prevent false positives when the cone is not fully seated in the claw. Other REV sensors can be used, such as the REV 2m Distance Sensor or even the REV Touch Sensor (with some modification for the latter), but the Color Sensor v3 is the sensor of choice.

Thanks to team 11572 for the inspiration for this addition :)

Silicone Claw Molding

The second improvement in update 1.3 is the addition of integrated molds for making silicone liners for claws. This design is inspired by https://www.thingiverse.com/thing:1480408, which has built-in molds for pouring silicone liners for its claws. It also has triangular dogs to keep the silicone attached to the claw. We tested this method for claw liner creation and found the material to be well-suited to gripping the Andymark cones in PowerPlay. However, the small triangular dogs were not enough to keep the silicone pieces held onto the claws and were impossible to reattach once disconnected.

To solve this issue we made the dogs larger and made them extend all the way to the top and bottom of the claw. The larger size makes them harder to detach, and the top and bottom being exposed means you can slide the silicone pieces back onto the claw should them fall off. Our recommended method of attaching them is to mold the claws in place, remove them by sliding them off, and then apply CA glue before sliding them back onto the 3D printed part.

Thanks to team 11572 for directing us to this design :)

Here is a great video from Matterhackers about making silicone molds with 3D prints. While their application is slightly different, it covers preparing the molds, mixing the silicone, pouring the silicone, and removing the molds - which are the same steps required to mold the claws.

Here is an overview of the most important steps for creating silicone liners for your Loony Claw:

Mask the bottom of each claw with tape to prevent the silicone from leaking out. Aluminum tape works well for this. The goal is just to cover the hole in the bottom of the mold.
Mix the silicone according to your product's instructions. Each claw will need 6.5 mL of silicone, but mixing a small amount extra is recommended. Here is an inexpensive platinum cure silicone kit from Amazon: https://www.amazon.com/Silicone-Molds-Making-Kit-Liquid-Translucent-Silicone-Casting/dp/B08LZ3J82H/ref=sr_1_6?keywords=platinum%2Bcure%2Bsilicone&qid=1673302740&sprefix=platinum%2Bcure%2Caps%2C110&sr=8-6&th=1. This kit mixes at a ratio of 1:1 by volume and cures to a shore hardness of 20A.
Pour the silicone into the mold and tap the sides to release as many bubbles as possible (You can also use a vacuum chamber to remove bubbles if you have one).
Let the silicone cure.
Remove the tape and slide the silicone liner out of the claw. Use side cutters or a knife to cut off the thin ribbed mold from the outside of the claw. This plastic part can be discarded, it is no longer needed.
(Optional) Remove the silicone casting. Apply glue to the dogs and inside wall of the claw. Slide the molded silicone back onto the dogs and let cure.
Done!

Update 1.2 (11-16-22)

Improved servo mounts by replacing goBILDA L-beams with an all-in-one 3D printed part. This makes for a lighter, less expensive, less complicated, and more robust assembly. We have removed the original servo mount files from the CAD and GitHub, as the new version replaces them entirely.

Update 1.1 (11-11-22)

After the initial release, we received lots of feedback asking for a way to mount the claw to a set of goBILDA Viper Slides. To solve this issue, we created this additional 3D printed piece. It holds 6 captive nuts and replaces the goBILDA Low-Side U-Channel part that forms the rear structure of the claw. This part has holes to mount the claw directly to a Viper Slide stage.

The only modifications to the slides are:

Longer M4 screws (16mm) to mount the claw to the final stage
(Optional) drilling out the lower 2501-0001-0002's holes to allow the screws to mass through more easily into the nylock nuts in the claw
- This step is highly recommended because it will make screwing in the screws and installing the claw much easier because the screws will not be double threaded. If, however, your team does not want to drill out the threads in the slide brackets, this step can be skipped.