# 4 and 6 bar lift height calcs

We are getting ready for the TSA Nationals and did a total rebuild of the robot. We found our axles were twisted and almost stripped. So we are re-assessing our lift. We had troubles on the initial 4 bar lift reaching the top of the tubes and are considering a 6 bar. Are there any height calculators out there? I am not exactly the best math person, so I am hoping to find something on the net.
Suggestions?
Bill R.
#6101

It is possible to make a six-bar such that the middle bar goes completely vertical when fully raised. Therefore, the maximum height is exactly equal to the length of the middle bar.

I hope I would not have to do that:), but we liked the 4 bar with the exception that it just barely got to the right height. I can use 4 motors on the 6 bar if needed. We are at a 5:1 ratio with the 4 bar and had no problems. We ordered a lot of metal and parts trying to revamp this thing. My kids are the #1 ranked TSA VEX middle school team in the state, so they want to make it work going into TSA Nats.

On the 6 barâ€¦ what are the things to consider with the spacing between the middle(long bar) and the upper and lower arms?

Thanks
Bill R.
#6101

Mathematical explanation here
bar axle.lower

Thanks for the links!
Bill R.