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 :frowning:

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 :slight_smile: 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.