High lift help

I am working on a high lift with a fork lift/platform lift style design. I have a question as to how i should keep the forks from tipping downward at the very front? The forks tip down when there is a robot on them as it is lifting. Also, what is the best way to set the pistons to deploy the forks themselves?
Will post pictures later if needed.

A picture of what you have would help, or better description of how the “forks” are attached to your chassis.

Also, how much load do you have on them and how far out? With cantilever the material will bend some and how you have them attached may introduce some play that be the source of some the bending.

Ok i will post some pictures here soon. And if i lift any weight the forks tip down at the front.

If it is tipping and not bending, then it sounds like the structure that you are using needs to be reinforced. Depending on the mechanism it can more or less challenging.

I have seen some designs where their forks or platform tips back when they are all the way up. Do you know how i could achieve this without messing up the lift itself?

Here is a video of @3921C lift with the ‘tipping’ issue.

The lift release was bad but that is not affecting the tipping issue. Also the release is better now since i changed it

What do you mean by “lift release?”

The lift generally looks fine to me, as you’re able to lift a robot high enough. When you’re talking about “tipping” do you mean the tipping of the robot being lifted?

The lift looks to be a four bar linkage, which should hold the forward structure perpendicular to the ground as it lifts. If it is a 4 bar, is it possible there is a misconfiguration with the linkage? How does the lift front behave unloaded? Is the does the front part stay in the same orientation all the way up?

It seems to be a wild ride up on the way up as the sides are not lifting simultaneously, there is a risk of throwing the partner robot off balance (I can’t see if there is a mechanism to attach the robot to your lift, so that might not be an issue).


Also, looking at your structure, the part that holds the robot dips into you rear supporting structure on the lift. It is compound the effect of the rear support on the lift not being perpendicular to the ground and the hinge (I think it is that, but I have been proven to be poor at forensics using videos :slight_smile: ) tilts it even more inwards.

The robot that is lifted tips towards the front. The release pistons misfired so it offset the lift. When the forks are empty it stays aligned all the way through the lift.

The front of the 4 bar is spaced the same as the rear of the 4 bar. There is a small plate that compensates for the hinge offset.

Ok, from the video there is a lot of flexing going on with the structure, I am assuming aluminum for the c-channels. Also, I see the structure holding the robot tuck into the lifting structure on the four bar side. A plate to prevent that from happening might help the robot being lifted from drooping.

Here is a snapshot of all the elements drooping.

Picture of lifting
Seems to me that structure bends, so it is not perpendicular to ground and the structure that holds the robot is not parallel to the lift structure. Steel may be better in this application.

I like the stabilizing structure that comes out. Nice job!

One thing you can do is to test the deflection based on load. For example, use 5# loads incrementally to determine when the aluminum deflects to the point that the forks droop. You can compare that with using steel and see if it is the material selection that causes the droop.

I know it is not the materials because another team used the same materials and had no issues

@3921C Is it possible for you to post another video that includes the back of the robot as well? It seems that when the weight of lifted robot is applied, there isn’t any bending on the 4-bar linkage part, as 3 wide c channels are very strong when bent like that, but I suspect that the joint where the linkage is attached to the robot is weak. When it is fully raised, the vertical c channel is diagonal, which is because that c channel is always parallel to the back one, and if the back one is diagonal, the front one won’t be. One idea to prevent one side from going up faster is to connect the 2 sides of the lift.

I don’t know if steel vs aluminum really makes a difference in this case. Aluminum should be strong enough to resist twisting sideways. I mean the 3 hole side wont bend like this:
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Plus aluminum is lighter which is almost always good. P.S. Hi! (look at team number)

It seems as though the prongs droop because the angle of the joint actually changes. A way to alleviate this is by adding c-channels at 45° angles to both sides of the joint (the vertical c-channels and the horizontal prongs). Like this, but at 45° angles instead of whatever this angle is (iPads are not conducive to text-based scale drawings).
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The c-channels appeared to be twisting to me (torsional) in the video. Agreed about reinforcing joint.