Tape Measure Container Grabber

[Trey178]

Originally Posted by cjl2625

Spectrum has a similar idea for containers.
They posted some details on their blog.

After ruminating on the concept for a few days we finally had a successful proof of concept test. Thank you cjl2625 for the link and another thank you to to Spectrum for creating such a simple solution.

I ask whoever runs the forums to keep this thread open for other teams to discuss.

[gpetilli]

Originally Posted by Trey178

After ruminating on the concept for a few days we finally had a successful proof of concept test. Thank you cjl2625 for the link and another thank you to to Spectrum for creating such a simple solution.

I ask whoever runs the forums to keep this thread open for other teams to discuss.

I believe the saying on this forum is post a video or it never happened. What is your proof of concept and does it work?

[GeeTwo]

We're using a tape measure in our robot this year -- as a tape measure, of all things. We cut a hole in the side of the case and glued a volume knob to it, and fitted a 10-turn potentiometer into it. We're using it to measure lift height. Of course, since we can only go 10 turns, we can only use about 1/4 of the tape. It should be convenient to calibrate. -- Oh yes, it will probably also be in the field of view of the onboard camera, so the driver can read it as well if the resolution supports it.

[Trey178]

Shown below is a well used AndyMark wheel off of our robot from last year (2014). Running it is a BaneBots motor with a 64:1 gearbox. The tape is an old, tattered item just laying around our shop making it a perfect test candidate. A much rougher setup, but it still works.

[JamesBrown]

Originally Posted by Trey178

In order for this mechanism to work, one end of the tape needed to be attached to the frame. Where and how was it secured?



For the tape itself, did you remove it from the stock reel or use it as part of the assembly?

We removed it from the stock reel, and made our own.

[GeeTwo]

Originally Posted by Tristan Lall

You might want to investigate whether it works better with the numbers facing up, or down.

Every metal tape measure I ever remember using had the numbers printed on the concave side. This allows the tape to resist kinking due to its weight when extended horizontally better when the numbers face up. Not that you should totally dismiss testing this, but please do post if you learn something different!

[GeeTwo]

Originally Posted by JamesBrown

We removed it from the stock reel, and made our own.

You must make sure that you curve the tape as you reel it out if you want it to stand up; a flat tape will bend easily (if it didn't, they couldn't put it on a spool). Tape measure cases have a slot that is slightly narrower than the tape to force this curvature as it leaves the case.

[solopilot]

The band needs to go around the bin or tote. No prob if the tote is not surrounded by other totes. However, totes are pushed together closely in the landfill areas. How will the band go around it?

[cdicorpo]

Trevor,

I'm glad to see people took note of our design! We worked closely with 1099 throughout the season, and what Sam already said was pretty accurate. The actual design was fairly complex, using many 3D printed and laser cut parts. But the basic design is this: We used Stanley Fatmax tape measures (most rigid at long distances) and we (carefully) removed them from their housing. We then fed one end into a 3D printed core and wound it around, much like a peg on a string instrument (look up violin peg for an idea). The newly wound tape was encased in a laser-cut acrylic housing. We built two of these assemblies, and drove them from two externally mounted window motors connected through a shaft in the middle. For extra support on the tapes, we 3D printed two rollers to sandwich the tape (one concave and one convex) and cut special rubber bands to squeeze them together. Our hook design was really what made the whole thing work, so I'll let you figure that one out. One thing to note is: The Stanley Fatmax tapes can extend horizontally about 10ft or so (if I remember correctly) without collapsing. This may work for you. Also, our design was not perfect. Sometimes the tapes would crinkle and split, so we had many extra lengths made to simply swap out and rewind the tapes. The thing with tape measures is they have amazing tensile strength (over 800lbs we tested) but relatively weak shear strength if you bend them at sharp angles. If you're seriously considering this idea I can get you some detailed photos of our prototypes and leftover parts. Just let me know. Can't wait to see what you guys come up with!

-Chris

[Trey178]

Thanks for the share Chris. To reiterate, our idea wads to pull the containers on the step onto our side of the field without (possibly) moving any totes in the landfill. That 10ft limit is more than enough for what we want. On another note, we are also considering other brands of measuring tape if only to save a little money, but we'll use the Stanley brand if nothing else works.