### Author Topic: Designing a mechanical kicker  (Read 2023 times)

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#### Chypsylon

• Beginner
• Posts: 3
##### Designing a mechanical kicker
« on: January 26, 2012, 03:07:06 PM »
Hi,

our Robot has to kick a ball (approx. 95g, 74mm in diameter). Up to now, we've used a simple solenoid, on which we applied a rather high voltage (~180 V) to achieve a strong shoot. But the new competition rules prohibit any voltages higher than 15V (understandable if you consider the lethal amount of energy stored in high voltage caps), so we have to find an alternative way of kicking. Last year, some Teams used pneumatic kickers, but you need large pressure-tanks and the number of shoots is limited, so we would rather like to implement some kind of mechanical kicker.

Our idea is to build kind of a crossbow mechanism with rubber bands. But the problem is that we can't figure out a simple and reliable way to retract and release the rubber band. Could anyone point us in the right direction?

Another option would be a spring based kicker (like the starter used in pinball), but there's still the same problem of retracting and releasing...

If I've left out any (essential) information, please let me know.

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: Designing a mechanical kicker
« Reply #1 on: January 26, 2012, 04:14:27 PM »
Hi,

What will be the shortest interval between each kick?

A solenoid could still work if (re-)wound for low voltage.

Whether you use a rubber band X-bow or a spring, the loading mechanism will be roughly equivalent: A device that pulls back and locks a plunger of sorts and then a release mechanism (which could be a smaller solenoid). The possible issue with this method is the speed at which you can reload.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Engineering is based on numbers - not adjectives

#### Chypsylon

• Beginner
• Posts: 3
##### Re: Designing a mechanical kicker
« Reply #2 on: January 27, 2012, 01:52:00 PM »

What will be the shortest interval between each kick?
kicking roughly every 10 seconds should be sufficient, faster is of course always better

A solenoid could still work if (re-)wound for low voltage.

We've been using  this one rated for 3V (http://www.tremba.de/zylindermagnete/db-zylindermagnete-ZMF-2551d.001.pdf ,datasheet in german tough  ), but the shoot isn't that powerful. We could still try to wind our own solenoid, gotta look through those coilgun sites...

Whether you use a rubber band X-bow or a spring, the loading mechanism will be roughly equivalent: A device that pulls back and locks a plunger of sorts and then a release mechanism (which could be a smaller solenoid). The possible issue with this method is the speed at which you can reload.

I've stumbled upon this mechanism http://www.youtube.com/watch?v=UIQHtQL6O3M&feature=player_detailpage#t=18s . I really like that idea for its simplicity We would have to use a worm gear to prevent the "bar" from sliding back and for additional power and probably some kind of position feedback like an encoder or just some switches.
What do you think?

#### Soeren

• Supreme Robot
• Posts: 4,672
##### Re: Designing a mechanical kicker
« Reply #3 on: January 28, 2012, 12:34:10 PM »
Hi,

kicking roughly every 10 seconds should be sufficient, faster is of course always better
Then there's ample time for a reload

We've been using  this one rated for 3V (http://www.tremba.de/zylindermagnete/db-zylindermagnete-ZMF-2551d.001.pdf ,datasheet in german tough  ), but the shoot isn't that powerful.
Is it that one you have used with 180V, or at what voltage have you tested it?

We could still try to wind our own solenoid, gotta look through those coilgun sites...
If you have a spare solenoid to sacrifice, strip it of the old winding (measure the gauge/diameter of it) and replace with heavier wire - bifilar (or trifilar) winding will probably be best and/or you can make several sections along the winding length and make a number of complete windings to put in parallel.

I've stumbled upon this mechanism
[...]
I really like that idea for its simplicity We would have to use a worm gear to prevent the "bar" from sliding back and for additional power and probably some kind of position feedback like an encoder or just some switches.
What do you think?
I don't think that concept will work, as you need to load and lock it, to be able to fire it at a precise moment.
You'd need  lot more power than what is used in the video.
No need for encoders, just make a lock/release that signals when it's ready (loaded).
You could make something similar to a X-bow nut for the release.

What have you been using besides the solenoid for kicking the ball (i.e. the piece actually touching the ball)?

How much room is there in the direction of the kick?

Besides elastic bands (which would need to be very strong) and compression springs, a leaf spring may be a good option and may be easier to control.
Regards,
Søren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?