4 Bar Linkage flipper mechanism

D0ntstare · Post by **D0ntstare** » Tue Oct 19, 2010 11:13 am

Righto, after spending the last 7 hours trying to get this system to work I have finally decided I must be doing something wrong, I have cut out 4 different length arms tried them all in different positions around the robot but nothing seems to damn well work, the flipper will never full close or it tears the servo from its holding

... maybe the servo is in the wrong way round im not sure.

Here is an image to see if anyone can help

Regards

Bentley

joey_picus · Post by **joey_picus** » Tue Oct 19, 2010 12:24 pm

All I can really suggest from experience is a shorter linking arm (which Iam guessing you've tried) and/or moving the bracket on the flipper back...I'd try getting the flipper to close properly first before worrying about how high the flipper goes.

D0ntstare · Post by **D0ntstare** » Tue Oct 19, 2010 12:38 pm

Well where I have the bracket it seems that it wants to close in that position, however it does not actually do it when in practice, I may just leave it for someone with more experience at the AWS, I don't really want to go drilling more unnecessary holes in the flipper

AS to a shorter linking arm I have several different lenghts most are to long which is fair enough and they were from early versions of it, once I had everything lined up the way it should be when closed I properly secured everything in place, it works flawlessly in the movement side of things, it just does not want to fully close, and if the shorter length arm comes in it pulls the servo from its mounting :/

Remote-Controlled Dave · Tue Oct 19, 2010 12:44 pm

Is it jamming on something Bently? Something stopping it closing completely? I know that's probably the first thing you checked, but its always worth suggesting, just in case.

joey_picus · Post by **joey_picus** » Tue Oct 19, 2010 1:03 pm

Could you rotate the servo arm on the shaft slightly to make sure it closes, or does it touch the floor when fully down as it is?

D0ntstare · Post by **D0ntstare** » Tue Oct 19, 2010 1:13 pm

Yesterdays problem for around half hour was caused by a jam but I increase the size of the plate on the back of flipper to stop that, I have just tried it again with an even smaller link and this time I have noticed a heck of alot of flex in the poly carb, the 1 mmm cant handle it I don't think, I have a feeling its buckling under the torque and jamming its own linkages, but the closing problem seems to me to be more a fact of the servo is actually wrenching itself from its position under the force and strain, almost like its pulling against its own weight?

The servo could be rotated probably 3mm downwards but the flipper is miles of from fully closing as in like 30-40mm of gap between the base and the tip of the flipper.

joey_picus · Post by **joey_picus** » Tue Oct 19, 2010 1:31 pm

What have you got holding the servo down? In Jigsaw's system the servo is never pulled against its mount, only pushed onto it, so some foam tape is sufficient to hold it in place, but you might be needing something more substantial to hold it on.

Jigsaw also has a 1.5mm polycarbonate link rather than 1mm so that might be worth considering - you probably have the weight to go for a metal linking rod actually if that would help.

D0ntstare · Post by **D0ntstare** » Tue Oct 19, 2010 1:35 pm

I have some old metal rod from a coat hanger that may work

, as to the servo mount i'm using the same.. some simple double sided foam tape, although its not the heavy duty one that you use which in my opinion could be helping towards the overall problem.

Remote-Controlled Dave · Tue Oct 19, 2010 1:58 pm

Ahh, tape, my specialist subject! lol

Some foam pads are not great in ants, because, although they stick down well, there is movement in the foam. Its easy to tear one off its mount just by ripping the foam, rather than having to unstick the actual glue, if that makes any sense.
I'd recommend trying a thinner double sided pad. Though this wont solve the closing problem, it may help keep the servo in place.

D0ntstare · Post by **D0ntstare** » Tue Oct 19, 2010 2:08 pm

Lol

,

Hmm I have not seen different thickness's of the pads where do you get yours from? I have only seen different lengths, then again my pads were only 3 quid for a large pack in the works so they probably aren't ideal for sticking something thats creating that much torque?

Will the AWS have people willing to help me out with this problem? or is everyone really busy at this event and do not have the time to faff around with other peoples robots?

I think the problem needs to be seen by someone who has a bit more experience and more knowledge of what and where the problem is occurring.

I will try the metal bar linkage in a bit when I can find the 3 mm drill bit

to see if that helps the problem.