six and four bar lifts

My team just decided to switch from a scissor lift to a four or six bar lift. I want to know how high any other teams four or six bar lifts go. The lift must also fit under 12 inches because are bot will go under the barrier. Also what metal did you use? Thanks to those who replied.

My 6 bar can reach about 28 inches.

If you have any questions relating to 6 Bars or 4 Bars we will all be happy to help in any way we can.

I’m fighting my 4-bar lift right now. It’s just BARELY at the point where it can score if I put the right intake and table on it. We spent most of the last six hours staring at it, looking for a solution. I think we’ve finally found it, but I haven’t cut or constructed what we need. Give me another 2 days, and I may have it working. I’ll happily post some more information then.

I have a bunch of pictures posted you might find useful in a photo album (although you’ll have to scroll down to the recently added photos) and you may find some other stuff on the website we’re using as an auxiliary to our engineering notebook.

Our robot is solid aluminum, with the goal being of finding a way to hang. The lift has four motors, geared 1:3.

I have got our 4-Bar right over 24.125" and our 6-Bar is at 27 right now. You can get both to work. Sometimes it just takes more thinking and as Ephemeral_Being said “staring at it”. Take your time and you can figure it out :wink:

Why did you give up on the scissor lift?

Apart from weight, friction and common sense. :wink:

Naaaa I am just teasing you. Scissor lifts are really cool and can take a lot more load than a 6 bar ever will. Carbon Fiber C channels we need you.

The scissor lift is more difficult to build and get to operate. This seems easier and more reliable. Plus the field elements are a lot lighter then the sacks last year so we do not need very much lifting power.

Well, if you don’t want to hang…

Have you thought of using a vertical lift? Those can be made very compact and efficient if built correctly and a double lift would reach approx 24", triple approx 36", quad 48" etc. Just a thought. Ive had some great luck using 4 and 6-bar designs to reach great heights.

it’s essentially the same as a 6 bar, but our chain bar reaches under 29 inches max with 1 piece of steel 1x2x35 hole channel (17.5 inches long)…

holy guacamole. That’s insanely fast for it’s own good. Are you planning to hang with a slower ratio?

just an afterthought. if you’re worried about reaching high enough, you can make the linkage shift by playing with the hole placement

Have you considered using a double reverse n-bar lift? Our team is planning on using that and it is very compact. We did some research before choosing it to be one of our contenders and found a previous post ( ) that had information on them. Pastoral_Invasion talks about it and 254D had a double 4 bar last year.

Mathematically, the 1:3 lift actually SHOULD be able to hang with a large ball. That’s the advantage of aluminum. The four Mecanum wheels weigh more than all of the metal on the robot.

Of course, it’s entirely possible I’m wrong. We might end up switching to 1:5, or something similar if the need arises. This early in the season, we thought it was worth at least experimenting with a fast lift.

How many motors are you putting on this 1:3 lift? We built a 2-motor 1:3 arm, with counterweights and elastic assist (just for an experiment), and it could not lift a large ball.

Realistically, with an 18" arm and a ~12lb robot, you will need at least a 1:7 to hang with just your lift. However, if you have an added mechanism to help you hang, you could probably pull off a 1:5, or even a 1:4 if you tuned it perfectly.

Four motors.

Our robot is under 12 lbs. By quite a bit, actually. We’ve got 2 lbs. of motor, 1.5 in wheels, around 3 (no weights listed) from two batteries, a power expander and a cortex, and the aluminum weighs under 2 lbs. in total. All that put together leaves me with the 9 lbs. robot I intended to build from the start of the season.

We should be able to hang.

How long is your arm? With 2 393 motors at 1:3, an 18" arm is going to stall at ~4.6 lb.
~14 inlbs of Stall Torque per motor
*2 393 motors

  • 3 for the 1:3
    ~84 inlbs of stall torque
    / 18in
    ~4.6 lb

EDIT: Missed the 4 motors bit

*4 393 motors
*3:1 torque

/ 18in


With a 9lb robot, you’re going to cut it very close to your stall torque and you may find that the 1:3 lift hangs slowly and might overheat or trip a breaker before your robot is done high-hanging.

Ah, but it should be possible. And we’re just under 9, too. Which gives me a bit of lee-way to play with.

The entire goal is speed. Faster gear ratio means faster arm means better score. Lighter robot means faster acceleration. Faster acceleration means my Autonomous runs quicker than yours, letting me block you and not the other way around. Lighter robot also means you can use the faster arm to hang quicker, meaning more time scoring during the match.

That’s the theme of this robot. Faster than you. Because if I’m in your way, instead of you being in mine, I control the game.

And it should be awesome for Skills.

Your hanging will not be fast. I think a 5:1 ratio would beat your 1:3 ratio hanging just because it will be so much harder to hang a 9lb robot with your ratio than another robots 5:1 ratio. You also have to take into account Hookes Law for elastics. Those can help you out a tad.

As a guy who sucked at Physics last year, why would a 1:5 be faster than 1:3 when load-bearing? That goes against my internal logic.