Since i can’t seem to find too specific measurements of the Lynx arms i wanted to know whether the gripper of the arms would be wide, long and strong enough to pick up a tennis ball and carry it around in its grip. The diameter of a tennis ball is 2,5 inch or 6,35 cm.
It would be really helpful to know this since i have a project coming where i would need this ability. Money is not that much of an issue, but time is and i want to keep the hardwarebuilding time to a minimum so i can focus on programming. The kits from lynxmotion really seem to be the best way to go about building something like this.
I doubt that a Lynx-5 or Lynx-6 arm would be able to manipulate a tennis ball as you describe - to me, the grippers seem a bit small for that sort of thing.
something you might look into however: Lynxmotion has a “Robot Hand B” assembly which, along with the Servo Erector Set components, should be able to build a large, robust manipulator that can do what you’re looking to achieve. There’s a nice photo of the “Robot Hand B” unit - actually a pair of them in tandem to make a gripper - here.
A similar gripper, on the end of an arm made from Servo Erector Set parts should, I imagine, have no trouble grabbing and manipulating a tennis ball. If you’re willing to get a bit creative, you might be able to work out a way to actuate both halves of the claw with a single servo, and lighten the mass on the end of the arm a bit, at the cost of a little bit of dexterity - you wouldn’t be able to “roll” the ball between the fingers by moving the two servos in the same direction, but if you don’t need that kind of fine control, you probably won’t miss it much.
I’m guessing that has to be real close to fitting a tennis ball in. plus it looks cool. You’ll want to make sure your servos on the arm can support the extra weight.
Thanks for the fast answers, i seem to have missed the specs down there
That Trigrip really looks nice. For the extra weight, could i still use a Lynx 5 or 6 arm and replace the included HS-475 servos with say the HS-645MG from the Servo Erector Set or would the whole arm have to be built more sturdy?
Also is there a Parts list or assembly guide for the trigrip? I guess i could get what parts i need from the picture… but since i’m not located in America i would like to order as much as i need in one go to cut down on delivery wait time.
If i decide to build it…
Hm… with the Lynx Gripper weighing 6oz it should also be able to attach a Gripper built from the Robot Hand B, or do you think it would be getting too heavy with two servos and the parts needed to connect it?
A tennis ball weighs about 2oz, so thats what it needs to be able to carry.
Edit: oh silly the original gripper is 0.6 in weight… hm… what about upgrading the servos of the Lynx arm like in the former paragraph? Would that work?
The goal of this project is a robot that shall collect the balls lying around on a tennis court, so the arm would be placed on some 4WD rover or something similar and it doesnt need any extra dexterity apart from picking it up and putting it down somewhere else (say a light little basket on the back of the rover eg).
The HS-475’s definitely won’t cut it if you plan to use the 3 finger gripper or something similiar with a couple servos on the end… The 645’s would be better but you might even have to go higher than that. If you want some decent speed out of the arm plus some accuracy, I’d go with digitals, say the HS-5645’s as a starting point. Of course the more power, the better.
If you are looking to pick the balls up off a court, you might be better off using a different design altogether. It could take some time for the arm to pick a ball up and move on to the next one. A collection basket of some type might be more efficient and reliable. A large opening on the front of the rover with 2 horizontal rubber wheels that grab the the ball and shoot it the a basket on the back or something. Like a tennis ball vacuum.
If you have your heart set on using the arm, it could be done. You could always build your own gripper out of SES parts and just use 2 wider fingers.
Now knowing what you’re trying to accomplish with your robot, I’d have to vote in favor of the “ball scoop” design, too. It’s mechanically much simpler to implement, and there are tons of existing designs out there - the collection of tennis balls and similar objects has been a staple of robotics contests literally for decades, and there are many photos and footage out there of designs that have worked quite well.
Something like a rolling scoop would probably far simpler to implement than an arm as well, since you’d only need to roll up to your target object (yellow ball on a contrasting background) and hit it with some part of the scoop, rather than having to be precise enough to grasp it in a claw.
Of course, if you’re specifically trying to implement a claw-type gripper to handle a single ball at once, that’s doable, as well.
If you want to use an arm, you should look at keeping as many servos as possible off of the arm and operate the arm components via a cable or stiff wire. I’ve seen arms that appear to have the gripper operated by a very thin wire running thru a very thin flexable tube. This would keep the weight of the servo off of the end of the arm. Something like how a squeeze of the bicycle brake lever makes the calphers grip the tire rim.
Dubro makes the best quality cable push/pulls by far. They can be modified to any length but they are limited in their bending. And repeated bending int the same place will eventually kink the pastic sheath.
Since i get rated on my programming with this project i decided to definitely try the arm first. If there’s no time to build a more sturdy arm i guess i can still show off the code for taking balls and perhaps cope with the hardware after the rest has to be finished
If that doesn’t work out as planned i’ll try something along the lines of driving over balls to get them inside.
u could probly use 2 of the hand parts without the thumb and have 1 static
or mount some home made extentions (coat hanger) on the regular gripper as for speed dont think ur gonna beat the street sweeper type bots,or bug jim into hurring up on the mega ses brackets
