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Unread 20-01-2013, 02:44
RRLedford RRLedford is offline
FTC 3507 Robo Theosis -- FRC 3135
AKA: Dick Ledford
FRC #3135 (Robotic Colonels)
Team Role: Mentor
 
Join Date: Jan 2010
Rookie Year: 2009
Location: Chicago, IL USA
Posts: 286
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Re: Software control or gearing

Quote:
Originally Posted by Ether View Post
I haven't seen any videos of a successful linear shooter with only one wheel.

With a linear shooter, the frisbee has only a fraction of the contact time that a curved one does. Because of this, the acceleration in the linear shooter must be much greater to achieve the same exit velocity.

Beyond a certain acceleration, excessive slippage will occur, resulting in poor performance.

Adding a second wheel increases the contact time, reducing the required acceleration, and reducing the slippage.




I haven't seen any such videos either, but I also haven't seen any one wheel axis, linear shooters where the pinch edge opposing the one wheel is capable of dynamically flexing and pivoting enough, as the disk passes through, to significantly expand length of the arc segment of contact with the single wheel.

I also haven't seen much reporting on the seriously wide variations of wheel-to-disk friction grip that different formula urethane wheel materials can produce.

We have already found that premium skate wheels at durometer a measured firmness of 75A have dramatically better grip than other wheels only slightly firmer, and with a seemingly less "grippy" urethane formula.

In the wold of skate wheels (boards, inlines, and quads) the range or tweaking of urethane formulas to achieve grip, roll and rebound performance benefits is quite incredible. I highly advise all teams who are doing small wheel (one or two) shooters consider evaluating their options in the skate wheel category. Lots of size selections also available.

These efforts could prove to be as valuable as RPM tweaking, or at least supplement them.

-Dick Ledford
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FTC 3507 RoboTheosis
FRC 3135 Robotic Colonels