4 Bar Help


#1

Hey everyone. Our team is using a double reverse four bar to raise caps. When the lift starts to go up it also goes backwards. What can we do to fix this?


#2

Are the arms the same length.
Also post pictures.


#3

Sorry, but i don’t entirely understand what you are saying. Can u pls send a video?


#4

I’m asking if the two four bars are the same length.


#5

You should also check the spacing between the arms of each 4-bar. Each end of each 4-bar should have the same number of holes between the points of rotation.


#6

please send pictures, a lot of different things can cause this problem.


#7

Once again, send pictures. It’s most likely the spacing.


#8

Here’s a picture for anyone asking. The motor is getting stuck on one of our supports for the base. It starts out below the channel, able to clear it only if it moves straight up but it does not. Moving the whole thing forward helps but we don’t have much more room to spare for that.
image.jpg
image.jpg


#9

Yes they are the same


#10

Is the back tower (where the two 4bars link) leaning back?


#11

Looks like you’re powering it from only one side of the lift, is this correct? That would result in lopsided movement.

You could fix it by moving your motor out of the way of the lift, and then using a long (well supported) shaft and chain to power both sides.


#12

No i don’t believe so. the two towers are parallel


#13

Yes. How could i love it out of the way though? I don’t see a spot on the base.


#14

There should be a spot on the lower lift where the arms don’t cross. If you support that spot well with an L bracket (probably have to come up with something) you should just be able to do that.

As I don’t have your robot and parts in front of me, I can’t really give you an exact solution. But it’s what I would do. Or possibly power it from the middle section. But I haven’t tried that with V5 motors yet.


#15

You can power a dr4b with one V5 motor from the middle section no problem. See the attached picture of an early version of my teams robot which has this.

You could fix this issue by moving the motor. If you look at the cap claw in the attached picture you can see it is attached to a gear box, and the motor is mounted on the same side as the claw but above it. You can’t see the motor in the picture because we had taken it off, but it works.
IMG_1885.JPG


#16

That makes sense. We will try moving the motor to a similar position. Thank you for the help!


#17

Make sure that you make the gearbox tall enough that when you are flipping the cap it doesn’t hit the motor. I used gears in that one, but a chain & sprocket might work better. I think I also had that one mounted on a hinge so that it could flip out.


#18

@linbots92018A
My team built a double reverse 4-bar aka a 6-bar
The spacing is key. We had the same problem as you. You must put spacers in between each of the shafts until the motor can go up and down without a problem. Also, make sure that your whole entire arm is straight and not straying to one side because if one side weighs for than the other than the side that weighs fewer shifts over screwing up everything.


#19

A DR4B is not a 6 bar. Although, formatted correctly, they’d have roughly the same vertical reach.


#20

@Got_a_Screw_Loose
Sorry, I mixed it up but it still can help him though.