High Hanging

ok so what i would like to know is has any other team built a robot that has high hung BOTH SUCCESSFULLY and RELIABLY at a competition and has documentation of it. The members of team 1727A and I would like to know whether or not our robot, “Ahab”, is the first to ever high hagh in competition. We achieved this at the Northwest Maryland VEX Robotics Competition where we were undefeated and ranked 2nd on October 30th, 2010. so, as can be expected to ask, ARE WE THE FIRST???

This was posted here on 6-15-10…
No video, though, so it didn’t happen! :smiley:

yea i saw that page to but i find it hard to believe due to the lack of evidence, we on 1727A however have video footage of every one of our matches at the Northwest Maryland Vex Robotics Competition, (but in order to keep the process by which we accomplish high hanging a secret, we havent released these videos yet but they will be released for viewing in the near future)

our robot can hang now :slight_smile:
heres a vid of hanging (credits to them for helping us figure out a similar mechanism to hang)
in this thread: https://vexforum.com/t/clean-sweep-in-round-up-video/17853/1
more specifically the vid: [http://www.youtube.com/watch?v=D8_JSheLcI4

skip to 6:16 and 8:25 for hang clips](http://www.youtube.com/watch?v=D8_JSheLcI4)

Wow! thats a very innovative design u hav there. did u need to use high strength motors and do you have plans for high hanging?
my robot uses a double extension mechanism

that is not our robot
post in the specified thread if you have questions
(mine arnt even answered yet :P)
our robot is similar, thats all i can say now

well post a full review of our robot as we grow nearer to our first competition (Nov. 20)
and its a pretty darn epic robot for first season :stuck_out_tongue:

You haven’t signed up for the Jump Start Tournament yet and there are only eight slots left. You’all better hurry. :slight_smile:

Team 2348 had a high hanging robot (semi-consistent) at the McKinley Invitational on August 21, 2010. Here is a link to a Video.

We were able to hang three out of six matches. It was a reasonable design, but we did have too much stress on the axle so it twisted. The actual robot was very unstable, but we wanted to be the first to high hang in real competition. Being so early in the season, we did look at the numbers and realized that we would have won all our of matches if we high hung each time.

We have been experimenting with other designs including a winch, but it seems too slow. This coming weekend, we are hoping to debut a better high hanger at a competition in Mililani, Hawaii. It has successfully “climbed” the ladder to high hang.

Axial stress is a huge problem with designs that hang in my experience. My team back in high school had multiple shaft shear failures and often walked out of matches with very twisted shafts.

If you want to live on the edge of your design and run a low safety factor, you can case harden your Vex shafts. This will effectively prevent twisting while making the shafts more brittle. This is preferred since a brittle shaft is less likely to damage other things (mainly gear hubs) and the shaft as a whole is stronger. Please ensure case hardening is legal under this year’s competition rules and only case harden when supervised by an adult or other responsible person as it is a pretty hot process. You also may wish to evaluate if you can use a design that puts less of a load on a Vex shaft than you are applying as the above team did.

I personally thought that high hang was pretty successful and relatively quick, showing how to build a robot that “slides” up the side of the tower without getting hung up.

I am another member of 1727A who has some video footage from the Northwest Maryland VEX Robotics Competition on 10/30/10. I will have the videos of “Ahab” high hanging online by the end of the day.

Sounds like Hanging A’Round to me! We aren’t the TWISTED BOTZ for no reason. We made a lot of twisted axles that year (once we stopped breaking gears).

Jon T

This is the one video that is up on youtube right now.
More videos might follow soon but will talk with the other members of 1727A
First Part: http://www.youtube.com/watch?v=swGBn_XFvtE
Second Part: [http://www.youtube.com/watch?v=znhkbAF-qvg

oh and I also agree with Patrick that both robots have a nice design](http://www.youtube.com/watch?v=znhkbAF-qvg)

our partner team tried to lift their robot with a 1:27 ratio for the arm
and the axle got completely DESTROYED!! it was twisted at least 3 times before we realized

did your hang fail the other 3 times?
or did somebody defenced on you?
or did you try to play defence yourself?

nice simple design for a lightweight robot
my only critique is that it is unable to pick up and score tubes :frowning:

Second Part: [http://www.youtube.com/watch?v=znhkbAF-qvg

oh and I also agree with Patrick that both robots have a nice design](http://www.youtube.com/watch?v=znhkbAF-qvg)

nice designs as well as the above
i think they both used the linear slide rails and it was effective for a lightweight robot

currently though, our robot’s chasis is composed entirely of steel frame parts but we plan on building a new chasis that still utilizes the strength of the steel parts where they are needed, while replace the other pieces with light weight aluminum

Be sure when weighing steel versus aluminium that you weigh exactly how the steel parts are stronger and if that is needed. Material failure is a rather infrequent problem in Vex…

A solution to twisting shafts that may help would be additional gears on the shaft, in particular putting 1-2 gears on either side of your arm load. The arm failures my team had were on arms only connected to the shaft via the black hubs and a single gear on the arm’s side. In general, those little back hubs cause a lot of problems and I would avoid them in an arm application (which is the only way I can imagine you hooked up an arm to a 27:1 gear reduction)

thats exactly y we have our robots arm bolted to the 84 tooth gears that are on both sides of the mount. in addition, these 2 gears are bolted to eachother as well

The other three times:
First attempt, robot fell over and unable to recover.
Second attempt, gearing was still not enough.
In our fifth match, we had substitute driver who just didn’t get it together.

We also spent time knocking over stacks of tubes.

I really just pushed the students to hang early in the season and we did.

The easiest way to avoid shaft failure in a situation with LOTS of torque? Don’t transfer the torque through the shaft. Sometimes it is unavoidable, but often you can solve the problem by bolting gears directly to your torque arm (be it a robot arm, pulley, wheel, whatever) at the final stage, and bolting gears to each other in the earlier stages. I’ve managed to build some RIDICULOUSLY torquey joints with VEX (especially since the high strength gears came out) without too much trouble.

In addition…
In my experience, most shaft “twist” failures happen not because of the load on the torque arm, but because the torque arm hits a hard stop, and the load goes to infinity (infinity being an approximate value). At this point, if there is significant enough reduction, the motors are free to just rip things apart. If you use a limit switch to stop the motor when the arm is at the end of its travel, this issue is alleviated.

(i.e. assume a motor/gearbox combo is capable of outputting 20lbs of force at stall on the tip of the torque arm, this will easily lift a 1 lb weight without any damage to the mechanical system. If you take this same system, and stall the arm on a hard-stop, this force may be enough to do some damage…)

The other solution to the “high load” problem is simple – remove the load from the motor/geartrain. Use “passive assistance” (i.e. counter balance, spring loading, etc) to take up most of the load. In many situations you can make it so the motor doesn’t need to do much work at all…

Just some thoughts…


Now that rope is legal in VEX robots, there is bound to be a large influx of the number of Low Hanging robots if not High Hanging robots. Those of us on 1727A are satisfied with our current hanging device, so we currently helping other teams that attempt to hang with any difficulties they experience as well as help them brainstorm new ideas. So, any thoughts of implicating the winch and pulley kit for hanging purposes??