Flippers

[ballistix_buddy]

Hiya,
Were meaking the flipper on our featherweight powered by pneumatics. How do you attach your rams to the flipper and the robot. Do you have it pivorting or just punching the flipper arm. Thanks
josh miller,james davis,Team BallistiX

(Message edited by ballistix buddy on December 05, 2007)

Gravity style here. Punching the arm.

we use gravity style to, most do now i think

[leorcc]

With a flipper, 2 things to keep in mind: Pressure, and flow. Pressure is nothing without flow, and flow is nothing without pressure. This is true in all versions, low pressure ( 16bar) or high/full pressure (max 70 bar).

Make sure you have a buffertank that is capable of feeding the cylinder of your flipper without a significant loss in pressure (there will always be a little). The rule of thumb is 3 times the volume of your cylinder for optimal performance.

And keep the pipes short and wide, with as little bends in them as possible.

Also, make sure you have a reliable drive. There comes a time your robot runs out of gas, and then it is paramount that you can keep driving.

(Message edited by leorcc on December 06, 2007)

[pressure]

A question for you Mario and Leo, when you have fired the flippers on your robots what method do you use to vent the rams so they will return?

[maddox]

All the Hannibalitos have the Cutlet exhaust hole system

This isnt more than a 1.5mm to 2mm hole in the ram to vent. As soon the Burkert closes the ram loses pressure, and the bungees retract the rod and arm seperatly.

Disadvantages, you lose about 5 kg of force, and a bit of gas as long you keep the Burkert open.
Buffertank about mandatory, as a bottlevalve wont have a much larger flow than the exhaust hole.

Advantages.
Cheaper
Lighter
Less space needed.

another little point i have noticed FULL PRESURE when empted into a large buffer must be near LOW presure well ours is

but works brill

[leorcc]

Not really. In the gasbottle the CO2 is liquid, and it gets the chance to expand and boil to gas in the buffertank (ideally you would want it turned to gas before it reaches the buffertank but that is not always possible). So you always have more gas in the bottle than in the buffer (unless you have like a 5 liter buffertank but that would be just silly in a feather) until all the liquid in the gasbottle is gone.

The trick is to make sure your buffertank and pipes get the chance to heat up again. The boiling process of the co2 is drawing heat from its surroundings and freezes the pipes, valve, tank, anything it can draw heat from. The more time it gets to settle and thaw out, the more pressure it can build.

[pressure]

Thanks Mario/Leo, thats about how Skink is set up, it has a tiny hole (about 1/2mm) at the bottom and a 6mm hole at the top so it looses pressure rapidly once the ram is fully extended, a lot of gas is wasted though. Skink does not have a buffer tank at the moment, something we need to add.