# 8 bar

has anyone ever made an 8 bar linkage? the biggest ive seen is a 6 bar like on the NZ style bots. post images if you have seen one!!

Close enough?

NICE!! it would be cool if someone could make one like a 6 bar but with an extra level.

funny you say that. We were thinking about making an 8 bar lift or even a 10 bar lift just to see what it could do.

i can’t wait to see it!

An 8 bar won’t reach any higher than a 6 bar with the intake starting on the ground. The main reason that a 6 bar reaches higher than a 4 bar is that the middle, longest bar is longer than the equivalent bar an a 4 bar.

No, an 8-bar will go higher. It doesn’t have one middle bar, it has two. So compared to a 6-bar it effectively has a discontinuous, slightly longer middle bar where the two parts are separated from each other by a vertical distance. So yes, it would go higher.

Photo credit to team 394: http://www.wix.com/jokai2202/his-robotics#!gallery/albumphotos5=10

I don’t really have the time to look up the link, but I remember there being a thread or a picture of a 2stage chain linkage lift. It got something like 50" of reach.

Ohh… we also thought of a quadruple extending linear lift after we say a piece of our schools work equipment in the gym. Uses for it? Not really… But it sure would be cool.

It may be a while if we get around to it. We have to keep our robot assembled until June.

Or at least, an 8-bar can be designed to go higher.

A 6-bar (in this context), is really just a 4-bar with added stability.
Max height is constrained by height of the shoulder joint, and length of the bar.
The diagonal of a square (root2*18") is typical.
The double diagonal of a cube might be possible with some designs.

The soda-can-8bar uses a low shoulder.
A high shoulder 8-bar could raise the tip from ground to 3*18", if both upper- arm and fore-arm segments can point straight up.

One of my brainstorms for VRCollegeC was an 8-bar with a front tower, centered upper-arm, and split lower-arms forking the front tower.

Actually, it’s possible to get close to 4*18" with some thought, but for this game it’s not necessary.

I am experimenting with an 8 bar design, though. We didn’t have enough linear slides for a 2-stage elevator

I’d like to see a sketch of a 4*18" high reach with an 8-bar.

I think an 8 bar would be cool but i think it is unnecessary. I think 6 bar is plenty good, although it would be cool to build it just for fun. Food for thought i suppose.

An “eight bar”? I’ve never heard of that before. What is it?

That was my post We redesigned to use the same system, which was two four bars linked together by chain, but it was very unstable.

What we ended up doing is adding a second vertical linkage to drive it similar to a scissor lift, and making two of them side by side. It weighed quite a bit, but got 38" of height.

Link to the post mentioned: https://vexforum.com/t/team-1064b-robot-reveal/20356/1
pictures are about a quarter of the way down in the linked album on the thread.

15e6 PSI ? Wow

If you are taking requests, I’d like to see a Rick TYler version of u-joint ackerman drive:

small wheels, 4 wheel drive,
ackerman steering front wheels with Ujoints,
ackerman steering back wheels with Ujoints,
left side motorstack chain drives left wheels,
right motors for right wheels

pictures are about a quarter of the way down in the linked album on the thread.

yours is where i got the idea, but it is more like two 4 bars put together. i was thinking something like this:

Our scissor-lift uses 12 bars… I don’t think that counts, but from our point of view a 6-bar is basically a swinging, sideways scissor lift. Many of the principles are the same.

I posted an 8(9?) bar lift in the pictures section.