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#1
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Re: non-pneumatic "kicking" mechanism
Since the only arrangement of elements with any structural integrity is the triangle, and since it is more efficient (less material) to apply and direct force via tension ---
Our kicker is an aluminum triangle "pendulum" made of tee-slot channel with gusset plates at corners and a "toe" on low corner for ball contact. Triangle's top corner clamps to 5/8 axle through ball bearings. At low corner of triangle is attached a 1500lb test 1/8 x 1/4 synthetic cable that runs through forward mounted pulley which turns cable rearward, toward bank of bungee cords, pre-tensioned to ~50LBS. Rear corner of triangle has strong travel stop cord attached to solid frame anchor point. It stops the kick at end of travel, and it sustains the minimum pretension force on bungees. On its path rearward to the bungee group, the kicker cable passes through a winder plate that is driven by a geared down CIM motor to ~12RPM. Winder rotates 0-180 degrees in just over 2 seconds to shorten tension cable up to 12", depending on desired kick strength (bungee tension rises to ~120Lbs at max.). Kick is triggered by instant disengagement of winder cable from the winder plate using 2" of pneumatic cylinder piston travel to actuate the disengagement. The kick can be triggered at any point in the wind up cycle from 0-180 degrees. The trigger design is a very simple medieval-type concept and there are no other masses accelerated during kick, except the kicker & cable, and that is all I can say about it. We are waiting to finish the gear box setup for the winder to confirm what level of wind torque it can hold while motor is de-energized. If de-energized motor allows winder to UN-wind, another system will be needed maintain the wind up tension/torque while waiting for the right moment to launch a kick. Will confirm results of gearbox test when finished. So far, our kicker has consistently placed shots within a 30" dia. circle at 35+ feet. We still need to "possess" balls well enough to maintain this level of accuracy during match play, and this remains the bigger challenge. We do expect to be able to consistently score two or more goals from far end in autonomous mode. -RRLedford Last edited by RRLedford : 01-02-2010 at 03:36. |
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#2
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Re: non-pneumatic "kicking" mechanism
Here you can see our kicker.
http://www.chiefdelphi.com/forums/sh...highlight=1860 Without pneumatic systems. Only a CIM motor with gear box!! |
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#3
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Re: non-pneumatic "kicking" mechanism
Our kicker is powered by surgical tubing right now, but for competition we will find something stronger. We pulll it back with a window motor, and we have this sort of locking ratcheting mechanism which we will release with another window motor. Our range is looking to be around 40 feet, but it's variable on how far back we wind up the kicker.
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#4
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Re: non-pneumatic "kicking" mechanism
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#5
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Re: non-pneumatic "kicking" mechanism
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I was wondering if you read this somewhere or if your team discovered it by testing. Thanks. ~ |
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#6
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Re: non-pneumatic "kicking" mechanism
I have read on Delphi that the spring constant of surgical tubing is very temperature-dependent. I've also heard from others' testing (at this time I don't remember who) that their surgical tubing powered prototype had issues with consistency.
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#7
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Re: non-pneumatic "kicking" mechanism
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~ |
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#8
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Re: non-pneumatic "kicking" mechanism
I'm not so sure that the use of bungee cords sacrifice force when compared to surgical tubing.
You can easily make up for it by applying more/different bungee cords to achieve the force you are looking for. If consistency and durability are better with the bungees, its a no brainer, right? |
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#9
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Re: non-pneumatic "kicking" mechanism
Our kicker is going to be a large spinning blade/paddle thing. We will be able to adjust the speed/turn it off at will, allowing us to control the ball how we want to. Our tests give us about 10-15 feet, but we are changing the kicker mechanism now to have a larger paddle and possibly 2 motors.
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#10
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Re: non-pneumatic "kicking" mechanism
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#11
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Re: non-pneumatic "kicking" mechanism
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The veracity of the premise has not yet been established. ~ |
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#12
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Re: non-pneumatic "kicking" mechanism
Yeah exactly. I guess one of our team members read somewhere on CD about harpoon gun tubing so now one of our mentors plans to get us a few different diameters of the stuff so we can figure out what works best. There are a lot of stretchy materials to use, and surgical tubing is probably not the ideal material.
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#13
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Re: non-pneumatic "kicking" mechanism
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"Surgical" (latex) tubing is ideal for these applications. speargun and slingshot tubing ~ |
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#14
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Re: non-pneumatic "kicking" mechanism
Quote:
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#15
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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. Last edited by Chris is me : 02-02-2010 at 09:26. |
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