[Question] Good servo for gripper?

[Oasis]

Hi, I purchased a KST DS215MG servo for my antweight gripper, but soon realised that there was a flaw in it, if it can't move to the position it needs to, it resets its position! What this means is after around 10 seconds of gripping it stops gripping entirely because its neutral position resets!

I plan to resell said servo (If anyone wants it cheap I can give it to ya!), but I want to ask, what is a good tried and tested servo for antweight grippers? My budget is quite high so I'm not too concerned about cost

thanks

[peterwaller]

It is never good to have a servo stalled for any great period it is better to introduce some kind of spring tension into the mechanism so the servo can reach its end stop even when the gripper arms cannot meet as below.
https://youtu.be/82EdxPb6ZT0

[Oasis]

Thanks for the reply! Unfortunately my robot is now actually complete and I'm not sure if designing a whole new system is going to be doable, is there any other viable solution I could try?

[Kyro]

for a good solid reliable and cheap servo go for the towerpro mg92b... make sure its a genuine one (servoshop has the real ones)

out of 6 i purchased over a year ago, 5 are still going strong... they have been through multiple events as well as much much practising and seeing how many stacked tins of beans can it flip... (3 but you got to really want it)

i use them for both grabbers and lifters and they can certainly grab and hold things until the battery dies...

i wouldn't recommend them for flippers as they arent the fastest servo but pack plenty of power.

as for incorporating a tensioner of some sort, its could be as simple as having some flex in the grabbing arm...

or could also add a mounting point for the grabber just in front of the servo, and some stiff wire and the spring from a ballpoint pen you could make a non direct spring tensioned grabber...

for your design it looks as though it would only need a new top plate printed... or maybe print a bracket that attaches to your current top plate...

[Oasis]

Thanks, will look into that servo! Do you have any examples of such a system in a grabber I could perhaps refer to? I'm not sure how well I could pull this off blind!

In the case I end up designing such a system I might as well just keep with my current servo seeing as it works just fine in all other areas. Is there any major differences between the two servos?

[Kyro]

think nitro rc car... they usually have something simmilar on the throttle...

the difference between the 2 servo's is like a third of the price and a bit slower for the mg92b

thats all i really know having not used the kst personally

[Oasis]

I'm really sorry, I'm not familiar with this kind of system , do you have any examples of ants with one? Is running without this system obligatory or could I just run how it is with a cheaper servo? Would the recommended servo be able to grip without it resetting or heating from stalling too much? I recall my cheaper servo being fine with my old gripping system

[Kyro]

the idea is purely to take some stress off of the servo...

you could just back off the stick after you have grabbed them so its still holding but not at full force...

sadly i dont have any pictures for an example...

think of a stiff wire attached to the grab arm via a hole and the wire has a bend to hold it in place (like the steering arms on an rc car)
you then attach the wire to the servo horn in a way to allow it to slide (heat up standard horn and twist the end so the mounting holes are 90° from where they started is the easiest way, then just poke the wire through one of the holes) you then put the spring on the wire and bend the wire so that the spring won't come off...

this is for pulling... so the servo would pull the arm, and when it meets enough resistance, the wire will try to pull out of the horn against the spring... simply move the spring between the arm and servo for one that works with pushing...

hopefully this makes sense otherwise id have to draw a diagram

its not a requirement though... the servo i recommended will do what you want it to, and will keep doing it happily.

[Oasis]

thanks for all the help, I'll see what I can design, appreciate it !!

[peterwaller]

Here was my original gripper with just a thin piano wire push rod bent into a curve to allow it to flex rather than stall the servo.