This is Mr.Tangents “hook” mobile goal intake, i wanted to know if this would work with one standard high torque motor?Thanks in advanced.
A lot of teams are doing this with 1:7.
yeah i know i tried that, a 1:7 doesn’t fit on our robot.
I’ve also seen a team do 1:5 torque with full aluminum and 12 hole 4-bar
Thanks, but I just want to know if the hook would work.Our robot does not have much space so we need something compact, like the hook.
We do not know how your robot is like, so we cannot say if it would work on your robot, but I would suggest just trying it out It’s only a screw or two and 1 or 2 stand-offs.
Generally speaking, these sorts of questions are best answered by testing. However, some quick-and-dirty math can give you a ballpark estimation.
The worst case scenario for this linkage is when it’s fully extended forward and attempting to lift the nearly 3.7lb mobile base. From the perspective of the motor, it is attempting to lift the base at a distance of d inches from its axis of rotation, where d is the length of the c-channel attached directly to the motor. (I’m ignoring the weight of the arm here as well, which really shouldn’t be omitted… so, we’ll just round and say that the weight is 4lbs instead of 3.7lbs.) In this configuration, you’d be experiencing torque of (4lbs)*d. So, if that distance is about d=7.5 inches (I can’t estimate very well based on the video), you’d be experiencing about 30 in-lbs of torque.
That’s a lot of torque! But you have a 5:1 gear ratio, the motor would only need to provide 6 in-lbs of torque to lift the goal. Looking at the motor efficiency curves that jpearman so helpfully posted years ago, we see that this is well within an efficient, low-current range for your motor.
Of course, if your hook weighs more than 6oz, or if my estimated distance is wrong, my resulting numbers might be a little off. I recommend you try doing the math for your robot configuration, but my back-of-the-envelope calculations suggest it’s worth a shot.
EDIT: I’ll also note that I straight-up maximized the torque experienced by the motor, rather than looking at the torque at a particular angle; e.g. if the motor’s linkage is at t degrees above horizontal, then the torque experienced at that point would be (4lbs)dcos(t). So, if you don’t fully extend the linkage, it will take less effort to raise the arm again.
Thanks
@RoboDesigners
Does adding gears between a driven gear and the one attached to the c channel decrease the torque? My robots mobile goal lift has 2 HS motors geared 1:5, and by my math it should be able to lift around 10 lbs at the end of a 7.5 inch arm. 10 lbs translates to a mogo with >10 cones on it. Howver, in real life it cant lift more than a mogo with 2 cones on it.
But do you really need to lift a mogo with more than 2 cones? A fresh mogo should be ok right? you’d then stack onto it and placing it down wouldn’t be an issue (it’ll pull itself down with gravity - just give a little brake).
Its true that we wont need to be picking up more than a fresh mogo, but what doesnt make sense to me is why the math is so inaccurate. I havent taken friction into account yet, but it doesnt make sense to me how the math says it can do 10 lbs easy but in real life it jumps down to like 5.
That is how my current mogo intake is set up, with some standoffs in the back as a sort of hook, it works quite well for us.
I’m not sure either :/. Our old lift was running 1:5, except one version had the 60T gear secured to the bot (as the pivot point), while the other version had the 60T gear secured to the mogo arm. Securing the gear to the mogo arm worked much better for no reason? It could be because of the weight of the parts and the angle of the bar between the ground? We have a torque motor geared 1:9 and we can still also only lift a mogo with 3/4 cones on it at the ends of the 15 hole arms (although we have c-channels running forwards to “extend” the lift, don’t know if that affects anything.
I mean if your ever paired with an external stacker that can’t move mobile goals being able to pick up a mobile goal with ~5 cones on it is something you probably want to be able to do.
I’m not sure if I’ve seen an external stacker without the ability to pick up cones, although usually in eliminations you’d have enough choices, and in quals pushing it into the 5pt zone to get a 5+5(high stack) bonus wouldn’t be a bad idea.
Yea I guess but it still seems useful to be able to pick up mobile goals that are already stacked. You never know what the qualifiers will throw at you.
speaking of quals…(is already triggered)
My team used this lift with one normal motor and it works very well up to 5 cones. With a little bit of tweaking or another motor, it could do more cones.