Re: non-pneumatic "kicking" mechanism
 

We finished the transmission for ours today, now we just have to build the actual kicker. It sounds like we aren't the only ones using a pnuematic clutch system. We also have a worm gear system as well for variable positions/tensions.

Re: non-pneumatic "kicking" mechanism
 

Guess what? Spearguns and slingshots use "surgical" (latex) tubing.

"Surgical" (latex) tubing is ideal for these applications.


speargun and slingshot tubing


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Re: non-pneumatic "kicking" mechanism
 

Disregard the previous post, pneumatics are back in
design
fail
modify
evolve
crash
burn
rise from the ashes
etc.

note: i'm totally making that my new signature

Re: non-pneumatic "kicking" mechanism
 

we got our clutch working. all it needed was a bigger pneumatic to disengage it! and some grease.

it kicked ~30 ft at max power.

hint on our clutch- a poor gen2 tranny got extreme modded, andy baker would either laugh or cry...

edit- what the heck, ill say more:

what we did:

removed high gear from genII to make the secdond speed nuetral

dremeled down dogs so they have 30 degree edges (make it so crowbar is not needed to shift)

modded plates and shafts to accept a window motor.

upgraded to a beefier piston.

now it works great. we chained it to an 8" performance wheel as a spool. and the kicker is powered by 2 bands of surgical tubing.

Re: non-pneumatic "kicking" mechanism
 

We're using a linear motion to kick the ball to keep it compact (non-pneumatic). We're still aiming to fit under the tunnel.

Re: non-pneumatic "kicking" mechanism
 

Oh sorry yeah I guess I meant the surgical tubing in the kit, because it varies with temperature and isn't really strong enough for our kicker since we don't want to use like 4 strips of them. We would rather have one stronger piece of tubing or bungee.

Re: non-pneumatic "kicking" mechanism
 

I know I don't have any sources on hand right now, and I'll find some later.

Surgical tubing is generally the most powerful springy stuff per length of material you can (cheaply) get. I recall a Mythbusters episode where they load tested various springy materials and surgical tubing outperformed bungee cords of various lengths by a lot. In Overdrive it was pretty much the perfect material, since you only needed to get the ball somewhere over 6 feet high and this far, and other than that it didn't really matter how hard you hit it once you got past the minimum threshold for success.

Springy material is limited by the amount it can stretch without binding or breaking. A good, safe number for surgical tubing is about 5 times its normal length if I remember correctly from random testing. Surgical tubing wears over time and with repeated use which makes failure easier over time as well. I don't know as much about bungee cords, but material deformation is less of a concern as far as I am aware.

Considering that for many kicking styles, shot distance tolerances may only need to be within several feet of the target distance depending on your goals, surgical tubing may work for you. My team has prototyped with surgical tubing with success. Many long range kicks may just need to "get in the zone" rather than in the goal, and the range of force imparted on the ball that will get it in the goal (lowest being barely rolling in, highest being barely not bouncing out) is surprisingly large. Play with the math and see what you get.

http://www.primelineindustries.com/tools.html has a surgical tubing spring calculator assuming ideal (new) tubing at room temperature.

Re: non-pneumatic "kicking" mechanism
 

We are having a lot of success using latex tubing for our non-pneumatic kicker. We should have the ability to adjust the tension and therefor the 'kick' strength. Using a cim motor we can constantly put tension on the tubing then allow it to spring back. We even worked it out so that it resets in just over 2 seconds

http://www.youtube.com/watch?v=30-gyhhBQ7A

we need a better video and I will post one ASAP. The only delay is moving the kicker from the test platform to the drive base

Re: non-pneumatic "kicking" mechanism
 

Yes, using one larger piece would make a cleaner-looking design.

But your concern about temperature seems unfounded. "One stronger piece" of latex tubing will have the same temperature properties as 4 smaller pieces. And "bungee" cord material varies with temperature as well. For the tiny temperature differences between competition venues, there should be no noticeable difference between the two.


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Re: non-pneumatic "kicking" mechanism
 

Hi Rob,

I saw your video. Nice kick.

Couple of questions:

Do you use the motor to hold the kicker in the kicking position or do you use some sort of latch?

When you release the kicker, is the motor still connected? Or do you have a mechanism to disconnect it so that it doesn't get back-driven?


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Re: non-pneumatic "kicking" mechanism
 

Found the post about temperature for you: http://www.chiefdelphi.com/forums/sh...22&postcount=9

Also keep in mind you can adjust tension in a well designed system throughout the day, so you can make fine tuning adjustments before each match when the venue temperature changes.

Re: non-pneumatic "kicking" mechanism
 

Isn't there a temp sensor somewhere on one of the sensors that you could use to calibrate your shooting distance vs. temperature? then it would all be automatic.

(because programmers never have enough work to keep them busy)

Re: non-pneumatic "kicking" mechanism
 

Hi Chris.

Thanks for the link. The anecdotal information it contains may inspire some teams to go do a little research about the material properties of elastomers used for storing potential energy for kicking, and that would be a good thing (learning!). Maybe a team or two will even run some simple quantitative experiments and post the results - like hanging a 10 pound weight on the end of a piece of surgical tubing and measuring its stretched length at room temperature, then taking it outdoors in the freezing cold and repeating the measurement. Then do the same with a "bungee cord".

As for the relative temperature-behavior merits of bungee cords vs surgical (latex) tubing, which is what we were discussing, I doubt that even a 20 degree change in room temperature would make "surgical tubing" change its behavior noticeably more than a "bungee cord"... especially if it's a bungee cord made with latex rubber!


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Re: non-pneumatic "kicking" mechanism
 

I will post a better view of the kicker most likely tonight or tomorrow. The kicker is not held in a kicking position so no latch is needed.
A sprocket with a pin at the outter radius pulls the arm around and stretches the tubing. Once the sprocket turns 180degrees the pin is no longer in position to hold the arm back and the tubing snaps back and swings the arm.

Also through McMaster-Car there are many thicknesses for the tubing. I do not know but I wonder if tubing with a wall thickness of 1/4" is still affected by temp to any noticable degree (Within normal temparatures for inside ofcourse)

Re: non-pneumatic "kicking" mechanism
 

It could also be used to sense when hell freezes over :rolleyes: