Tape Measure Container Grabber
 

For Ultimate Ascent, one CT team had a climbing system that used a set of hooks deployed via tape measure. Now we have idea to use a similar mechanism to grab the recycling containers off the step without moving the totes in the landfill. Having it be directly driven off a Banebots motor, with a 12:1 gear ratio, gave decent retraction but not much else.

My question to the readers is this: what suggestions do you have for controlling a tape measure so it does not kink when it rolls in or out?

Re: Tape Measure Container Grabber
 

For starters, If you are committed to this, the Stanley Fatmax Xtreme will probably give you the best chance of success. It is the most rigid tape measure that I know of.

As far as avoiding collapse is concerned, joining 2 parallel tapes at the ends so that they can't twist would help.

Also, since sharp kinking tends to permanently damage the blade, once kinking does occur, replacement of the tape could reduce the risk of it happening again.

Good luck.

Re: Tape Measure Container Grabber
 

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

Re: Tape Measure Container Grabber
 

https://www.youtube.com/watch?v=b-1wx_xZ8tA

my favorite robot I ever had a hand in building. check out "sewer tape" it works well for this application.

Re: Tape Measure Container Grabber
 

If I understand correctly, sewer tape is just a thin strip of metal that can be extended out in a loop without sagging?

Re: Tape Measure Container Grabber
 

The team you are refering to is 2064. Their technical mentor was a technology teacher at my High School so i got to hear and see quite alot of that design

Im pretty sure that the 2 hooks they used were riveted to tape measures that without side loads are very strong. They were each ran off of window motors. A ball was pushed against the curved part of the tape so that it stayed alligned and bent less. (Not sure if that makes sense)

Overall was it the best design? It had its flaws especially the fact that the tape measures when touched or vibrated enough would collapse. At Where's Wolcott our team chose 1511 and them. As the #7 alliance we made it to the finals due to the fact that we timed out when each robot would climb another level since 1511's slams would vibrate the pyramid to much for the tape measures.

Re: Tape Measure Container Grabber
 

Whenever anyone talks about tape measures the first team that comes to mind is FRC3280 the RhodeRebels. They used a tape measure back in 2010 to climb. I'm sure that you could contact them, I remember at Boston they had a display/cutaway of the mechanism in their pit.

Re: Tape Measure Container Grabber
 

Exactly, it worked very well for us. We used the 1/8" thick tape that year but it comes in 1/16" as well.

Re: Tape Measure Container Grabber
 

Saw the video and I like the concept. Did some searching and it looks like it comes packaged on its own reel/spool. Could 2106 have assembled the mechanism so that it's directly driven, or belt/chain driven?

Re: Tape Measure Container Grabber
 

We cut the length we needed from the roll and made our own measuring tape holder:
http://www.chiefdelphi.com/media/img...18989dfe_l.jpg

Re: Tape Measure Container Grabber
 

Tape measures were a common accessory in 2002 (to expand the robot size to occupy a zone while scoring in another). They were typically powered by an external drive wheel off of a drill motor and transmission (roughly equivalent to the current RS-775 motors), or by direct drive (sacrificing the retraction mechanism by driving the hub directly).

However, kink-resistance wasn't typically a huge deal (except when teams decided to try to get entangled and draw a penalty by driving back and forth on an opponent's tape measure), so teams simply relied upon the inherent stiffness of the tape measure.

You might want to investigate whether it works better with the numbers facing up, or down. Also consider having quickly installable spares, because if it is damaged during one match, odds are it will kink at the site of the damage (if anywhere) during subsequent matches.

Re: Tape Measure Container Grabber
 

I don't believe 3280 is competing this year, and the Engineers involved have moved on to other teams. I worked with them that year and would be happy to answer questions.

Here is a picture of the spare we had in the pit in Boston
http://www.chiefdelphi.com/forums/sh...highlight=3280

And Here is a picture of the device in action.
http://www.chiefdelphi.com/forums/sh...highlight=3280

As PAR_WIG1350 said the Stanley Fat Max Xtreme is they way to go, or at least was in 2010. He also hit it on the head about kinking, buy multiple tape measures, and prep the tapes so they can be quickly swapped out.

Re: Tape Measure Container Grabber
 

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?

Re: Tape Measure Container Grabber
 

I believe we used a hinge and bolted it to the frame.

Re: Tape Measure Container Grabber
 

There was a video of a DARPA robot I saw some years ago that used three tapes slaved together to create a triangular beam. This was used as a camera pole for a very short surveillance robot. I believe the robot was only 6 inches tall, but the "pole" could extend up 10 to 15 feet.

Re: Tape Measure Container Grabber
 

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.

Re: Tape Measure Container Grabber
 

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?

Re: Tape Measure Container Grabber
 

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.

Re: Tape Measure Container Grabber
 

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.

Re: Tape Measure Container Grabber
 

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

Re: Tape Measure Container Grabber
 

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!

Re: Tape Measure Container Grabber
 

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.

Re: Tape Measure Container Grabber
 

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? :confused:

Re: Tape Measure Container Grabber
 

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

Re: Tape Measure Container Grabber
 

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.