Do you think our team should use 1 or 2 pistons for our mobile goal clamp? Also, what type of piston should we use; single acting or double acting?
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I would most definitely go for 2 single acting cylinders for this game.
A rubber band or 2 is enough to release a mobile goal, so hence single acting.
2 actuators because this year doesn’t really need much pneumatics, so the extra power won’t hurt.
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As @Gigahertz.t said, definitely go for more power, since there aren’t a lot pneumatics necassary.
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I agree. However one thing you might want to watch out for this year is placing your pistons right for the clamp to work. It needs to be positioned correctly so the piston provides enough power both in the X and Y direction for the clamp.
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Vex has a page related to coding and competition that states "The goal is not simply accomplishing the task, but creating a solution that works better, faster, or more efficiently than other possible solutions. "
I think that is a good goal for engineering solutions as well.
You can make one single action cylinder do that job easily.
Wikipedia has an entry about Levers that states:
" Levers can be used to exert a large force over a small distance at one end by exerting only a small force (effort) over a greater distance at the other."
Using this information, you can minimize resource usage using a single cylinder on a lever to forcefully clamp the mogo, and then use a rubber band to retract it.
Lots of teams are going this route this season and having great success.
Some teams are using multiple single acting cylinders on the robot for actuating hang mechs, intake lifts, mogo clamps, ring sorting mechs and doinkers. Using resources efficiently allows them to do all that while minimizing air consumption.
I’ve seen some teams do this. The thing is I’ve seen them do it with the current(new) vex kits. Would you just remove the tube and place a little black stopper piece at the end? Then band it backward to reset the piston?
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We would leave the retraction end of the actuator open, and on the solenoid attach a fitting with a plug in it where the retraction tube would’ve connected.
Or… you could use a lever… and have 2 actuators (for extra extra strength - that’s what we do). The most popular type of “lever” this year seems to be class one or three levers, as illustrated below:
Class one levers do present a mechanical advantage, but do take up more space. But even with both these levers most teams still use 2 actuators.
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Alright that makes sense, in hind sight using a plug on the piston too would leave trapped air or a permanent lack there of, as well as a little bit more weight. I definitely have seen more class 3 levers, Class 1 levers are too bulky so most teams don’t use them. But overall using a lever will be better. I actually saw a team that used standoff and stuff to make a class 2 lever which was interesting, it poked out pretty far so I wouldn’t use it but interesting concept.
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I tried a class 1 lever for my kiwi drive robot. I wouldn’t recommend it, the arc it follows made it unnecessarily hard to tune. the one I had would either press down on the top lip (raising the mogo but not secure) or pull it straight in by catching the lip depending on what a put on the arm. I ended up solving it by using both of these together, but it was overcomplicated and still not very secure.
Here’s an early season prototypes we built and tested.
This prototype used an older 150ml pneumatic tank and
a single action cyclinder to push the 1st class lever down onto the mogo.
We used a single rubber band (not shown here) to retract the clamp.
Later after testing, we ended up moving the cyclinder to the rear portion (red line and arrow) of the class 1 lever to avoid damage to the cyclinder during aggressive game practice.
Once at the rear portion of the lever, we tuned it for greater clamping force by moving the cyclinder mounting point one hole at time further away from the fulcrum point. At some point we found we could clamp a FULL mogo tightly and securely for around 6 actuations.
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