Tethers

[fluppet]

Fred - no, I think I understood: flipper attached to robot by normal hinge, ram hinged at the bottom, ram attached to hinge by a ball joint, yes?

I just wondered why a ball joint. With my limited knowledge of mechanics, they would appear to be less strong (per unit weight) than a traditional hinge - from the point of view of the flipper being pulled away from the ram, at least. Presumably your ram moves only in the same plane as the hinge and ram anyway, so theres no benefit to allowing it to move the other way (unless you want to avoid twisting your ram as the flipper bends). Id have thought a hinge where the ram meets the flipper would help reinforce the main flipper hinge, too.

Presumably tension on your flipper isnt an enormous problem (because you have a tether - see? back on topic! mind you, if the tether is supposed to be a safety device then you may not want it to be stressed under normal conditions...) but I was just curious at the choice. Im not quite sure how this helps it run smoothly.

Not being critical, just trying to learn a bit of engineering!

btw, do you know how hard it is for someone with my user name to type flipper? (A bit unfortunate, given my plans for pneumatics.) Ive managed to type flupper and flippet several times in the course of this post. Possibly I need some sleep.

--
Fluppet

[m2xt]

My understanding relates to how many points the flipper attaches to the body / chassis and not the ram base to the chassis. A three point is one for the ram and two for the pivots.

Paul

[big_nipper]

So strickly speaking as long as you have one or two points on the flipper and a teather (or three points on the flipper arm) the RAM does not have to have any fixing points to comply with the rules.

I think most is common sense, but been board at work I thought Id say something stupid.

Have you noticed how quiet the forum is today?

[jim]

Fightingrobots.co.uk is down at the moment - see the thread in General - which explains why its quiet.

[big_nipper]

Already been there, I hope its sorted soon or we will all have big problems.

[fluppet]

Fred: You type how I feel (bad cold, spent all day in the A2 traffic jam in a car with the heater stuck on, got to work 6:30pm...) :-)

Thanks, glad I understood. Dont think theres anything *wrong* with your approach, I just wondered if you had a reason for it!

Id be interested to know what everyone else does. I presume most are normal hinges at the top (need to dig out some tapes and check, but since I spent last week moving house [no, I hadnt lost the forum when the links went down, the blissful silence was for another reason] it may be difficult) with the exception of the Gravity push-linked variants. Am I mis-presuming?

--
Fluppet

[kaideejee]

Im planning to have a round silver-steel bar running laterally across the underside of the flipper, with the clevis on the end of the ram attached around this bar. Fairly standard I think, but please feel free to correct me anyone?

Not sure how Ill fasten the *bar* to the flipper yet tho.

-- Kev