Lift help

Our robot has benefited so much from the help that we’ve gotten from previous posts. Our mogo lift, though, isn’t doing so well. It’s very weak at picking up the mobile goals and even when we put some reinforcements on the sides, it just won’t lift it up. If you could help us understand how to better build this thing, please tell us! (Don’t mind our weird chassis; our parts are coming in soon)

EDIT: The pictures are pretty low quality, but I’ll try to explain it as best I can. It is a rack-and-pinion lift with two motors and 12-tooth gears.

I would love to help but for some reason the link is blocked for me. Could you post some pics please?

Sorry @Easton here you go!
Photo on 12-15-17 at 6.10 PM.jpg
Photo on 12-15-17 at 6.10 PM #2.jpg

I can’t see too much, but I’ll assume you need a higher gear ratio.

There are a few problems that I see with your build so far:

  1. Don’t cantilever any axles! Especially those which will be supporting 4-7 lbs of force.
  2. Make your Mogo carrier lighter. There is a lot of extra metal which does not add a meaningful amount of support.
  3. While using a rack and pinion system isn’t exactly a bad idea, they aren’t made to be able to support the weight of a Mogo. If you do continue with this design, try to add sliders as supports on the front end of the carrier. However, I would highly recommend switching to a 4 bar if you want to be able to score in the 20 point zone easily.
  4. Use sensors if you can. They will help you keep both sides on the same plane.

Yeah I can’t see the gear ratio, what is it? Also thanks for the pics. But a side note, I don’t think you need the upper portion of the lift. If you support it from the bottom and top of the flange of the mogo you should be good. Not to mention it could get in the way of your stacking mechanism. But if you don’t mind some rebuilding, do a 4 bar

@RoboTurtleLord okay! I don’t know what cantilever means, but I’m guessing that it’s something regarding the axles being the only thing lifting it up??

@Easton The only gears I used were 12-tooth gears. I’ll take off the top part :stuck_out_tongue:

After I’ve made the changes, I’ll post more pictures of the robot and try to explain the blurrier parts. Thanks!

S T E E L

To clarify, cantilevering means the axles are only supported on one side of the load bearing portion of the axle. This is bad because it causes bent axles, friction, and strain for motors.

+1 (Beat me to it LOL)

S N I P E D :slight_smile:

@Easton @RoboTurtleLord so I should get something to hold up the end of the axle?

Exactly.

I would recommend doing the same thing for your Mogo Carrier. Using linear slides or something, have the other end of the carrier supported. This will reduce the excess load being put on the pinions and motors.

@RoboTurtleLord due to how frustrated I just became with this thing, I’m starting to lean towards the four-bar lift that I wanted earlier on in the robot’s building process. The thing is, I’m not sure where to start. I can’t really build from a picture unless it’s really detailed (and that’s no fun) and the gearing scares me. Where do I start for a four-bar?

@infinitechVEX

While a 4-bar may look like a challenging build, it is really not if you know how it works.
I think that the best place for you to start may be to build a bare-bones 4-bar. What I mean by this is create only the linkage and don’t worry about the gears, mount and motors. Use the Mogo carrier that you have made and a few c-channels to make the linkage. I have attached a picture to help you visualize.

Once you have made the linkage, it should be easier to understand how it works and where you can mount it. Motors and gear ratios are very simple and making a gearbox shouldn’t be hard. I would recommend a 2 motor 1:5 ratio which would mean that you should use the 12 tooth metal pinion gears to drive the 60 tooth high strength gears connected to the axle on your linkage. Again, make sure that all of your axles are well supported on both sides.

The 60 tooth gear should be screwed on to the blue c-channel on the back of the lift (see picture). and just do the same on both sides. Then just use two c-channels (these can be the ones on your base) to support the axle. Powering them shouldn’t be too hard from there.
Untitled.png

@RoboTurtleLord Okay, I’ve built the linkage. I haven’t put it on yet, but I have drawn a rough sketch of what it might look like based on your description.

Green = motors
Light blue = axles
Pink = 12-tooth gears
Lavender = 60-tooth gears

The box in the middle represents the actual part that grabs the mogo.
robot.jpg

Ok, so your drawing is very close. You need to make sure that the motor is driving the 12 tooth gear so you have a torque ratio. You also don’t need any gears on the front of the linkage. Just make sure that arms are able to pivot freely. Finally, looking at the drawing, some of the axles are still not supported on both sides. I will try to send you a picture of how we supported our axles for reference.
robot.jpg

@RoboTurtleLord Okay, thanks! I’m having to rebuild my chassis because the mogo grabber (I have no idea what to call it) isn’t fitting. I’ll attach a picture once it’s done.

No Problem!
I don’t think that I have seen a name for it either(other than Mogo intake).

@RoboTurtleLord I’m guessing I need to attach the gear to both the chassis and the back c-channel for the intake? I just attached the motor and it seems to fall off the gear if I try to turn it.