Flippers

[julian]

Whats the view regarding flippers and where the hinge is? A front hinge like Firestorm vs a rear hinge like Chaos 2. What is the hinge made of?

[dmac]

Depends a lot on what kind of machine, and what pressure, full pressure needs stronger materials that say 10bar.front or rear hinge is entirly ou to you.

[jim]

The front vs rear hinge argument has been running for ages, so I wont go into that. The hinge on Serranos flipper is a 20mm round bar, mild steel I think. That fits inside a larger steel tube, cut up into sections and welded alternately to the chassis and flipper plate. It runs at 10 bar.

[blazerbotics]

our hinge is built the same as jims, but we run full pressure. With front hinged flippers you normally need alot of drive power to get far enough under the other robot, where as a rear hinged you only need to get the tip of the flipper under.

[julian]

I would have thought that self-righting was easier with a front hinge. Some of them sort of roll over.

[blazerbotics]

self-righting was easier with a front hinge waiting for a comment from mute!

[fluppet]

:-) Not necessarily true, anyway. Usually (because of the wedge shape) most of the weight of a flipper is towards the back of the robot. If you put the hinge of a rear-hinged flipper far enough back, it can gently roll the robot around its rear end - assuming said rear end is the right shape. See Spawn Again, WBC or Thermidor for examples.

Achieving the same with a front hinge, although it doesnt place any requirements on the shape of the rear of the robot, does mean that the majority of the weight is being flipped, and more of the flipping force gets absorbed by the robot (the rear end, as it hits the ground, will have more inertia because youre moving the centre of gravity higher). So you may need less CO2 to self right (doing this a front flipper is arguably more efficient, in that its shoving more of the robot), but if you dont have a limiting mechanism then the robot will take more of an impact - note the big impact-absorbing tyres on Firestorm, and the way the original Cassius threw a chain when self-righting.

Not that Ive ever built either type, so this is entirely observational and, in addition to being somewhat incoherent, may be rubbish. :-)

--
Fluppet

[tunna]

Bulldog is a great deal heavier at the front than the rear,this helps,

[julian]

Although Im posting in heavyweights, Im looking towards building a middleweight, so theres not a lot of room for weight redistribution.