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-   -   Gearing Mini CIMs (http://www.chiefdelphi.com/forums/showthread.php?t=130546)

Gdeaver 19-09-2014 07:10
Re: Gearing Mini CIMs
 
This is a link to our web site page with a write up on our surgical tubing shooter with a winch pull back. Some pictures to show what we did. Our shooter is an example of what happens allot in first. It was week 5 with no pull back solution and the pneumatic approach was going no where. Dead end. We took an AM shifter that had been used in a previous year and rigged it up. It's not perfect but the whole system - Roller intake, shooter, swerve worked very well. Looking back, if we had to design this again and had the time, I would have gone with a ball lock release mechanism.
http://wiki.team1640.com/index.php?t...BOT_X_Shooting

Nathan Streeter 19-09-2014 14:10
Re: Gearing Mini CIMs
 
Perhaps some folks can share their ideas more... but we really liked our launching mechanism...

We used ~100lbf of constant-force springs to provide the power, and used a miniCIM in a modified BallShifter to pull it back, hold, and release. We used a unique gear ratio (somewhere around 10:1, which had good torque but was on the non-optimal side since it was only initially designed for 2/3 the spring force), added a 3/8" ratcheting wrench to provide the stop, packaged it into a basic two-plate with standoffs frame, and put a 1" spool of Spectra cord on the output shaft. This all worked great!

I'm about to leave on vacation for the weekend, but there were some important design constraints in doing the above... for one, the dog shifting mechanism won't be able to retract under that amount of load... we tried... don't bother (unless you have a sense of adventure, like MacGyvering things, and/or have some extra cash to spend). :-)

AdamHeard 19-09-2014 14:16
Re: Gearing Mini CIMs
 
Quote:
Originally Posted by Gdeaver (Post 1400474)
Actually you can use the motor to hold the surgical tubing pulled back. That's what we did this year. We used a cim but could have used a mini cim. Used the parts from a Andy Mark shifter and added one more reduction stage. Used a force sensor to measure the pull back force and a PI to hold at about 120 LBS of tension. The holding current was surprisingly low and the motor only gets slightly warm even after extended run times. Only problem is the Andymark dog design has very little contact and the dog and gear wear. They have to be replaced periodically. Benefit of the design is that we can just kill power and the ball is just released with out shooting. At the end of the match the shooter is not in a cocked state. good for safety.
Curious, what force sensor did you use?

Gdeaver 19-09-2014 16:49
Re: Gearing Mini CIMs
 
You can search all over but there are not many choices for a amplified and conditioned 5 volt force sensor.
http://www.digikey.com/product-detai...6951-ND/809397

Yes, this was one of the build seasons major crisis. We had both a 3 stage andy mark and a vex pro ball shifter. Looked at both. Choose the andy mark because it could be modified the fastest. Was tested after 1 night's work and we went for it. Looking back the ball shifter is what we should have done but there was no time to devote to it. Make your choices and live with them. Yes, it does take a 1.5 inch pancake at 40 psi to rip the dog out. We replace the dog gear before each competition. I like balls. We also used a ball clutch on our intake roller to prevent RS motor burn out.

Ether 19-09-2014 17:24
Re: Gearing Mini CIMs
 
Quote:
Originally Posted by Gdeaver (Post 1400739)
it does take a 1.5 inch pancake at 40 psi to rip the dog out. We replace the dog gear before each competition.
Do you cut motor power before disengaging the dog clutch?

wireties 20-09-2014 18:00
Re: Gearing Mini CIMs
 
Quote:
Originally Posted by Gdeaver (Post 1400474)
Actually you can use the motor to hold the surgical tubing pulled back.
True, of course, but you are wasting power driving around with the motor holding the surgical tubing back. You can gear it so things are easier on the motor but that is a compromise also - it would take longer to pull the tubing back.


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