First iteration of Bob, the unstable robot scissor lift.
Features:
six bar scissor lift
Precision slow speed high torque rising intake roller
Slick Poly-carbonate intake ramp
six wheel four motor high speed/torque drive
Scoring:
Can reach all goals
Plans for improvement:
Descoring into own intake
Improve stability
increase lift torque
Just a warning. NONE of the scissor lifts at the REX scrimmage did well. Be sure that the arm cannot jam itself by having both sides raise/lower at different speeds. This killed almost all the teams that used scissor lifts.
I would, but there is so much that could go wrong with compound gearing that I chose not to. good idea though. I think if I can use elastics and stabilize the arm so the motors work in sync. Also, if I add two more motors, it should be able to lift it flawlessly…
I don’t have enough sacks to test it yet. with the welcome package, all you get is two green sacks, but im assuming there will be a problem if I pick up too many.
Our Gateway lift used a 1:21 ratio, and we didn’t have many problems with the compound ratio. Just be sure to use high strength gears!
Some good ways to stabilize your lift include adding lots of cross-beam supports between the sides of your lift and using a 12" shaft to connect the two rack gears together (so they spin at the exact same speed).
It’s almost scary how much this robot resembles our Gateway bot, Steve the Scissor Lift.
Because of their low reliability and difficulty to perfect, scissor lifts rarely succeed in the early season. At our first Gateway tournament, our scissor-lift robot ranked 26th. However, once you get them working better, they do tend to succeed. At our third tournament, we ranked 2nd and were the tournament champions.
Thanks for the advice. As much as It might seem, I didnt TRY to copy your bot, but I may have gotten some inspiration from it. I must also mention a big THANKYOU for some inspiration on the top linear slides. it was a pain trying to figure out a stable surface for my intake to hang from. I did not copy it exactly though. Mine is a whole bunch simpler.
Anyway, I didnt think of connecting the rack gears together. that would help a lot. thanks.
I’m confident that the ammount of time I have before the first tournament will give me enough time to finish, test, program, and practice with it.
Looks pretty good so far, but as Ive said many times, we still have around half a year before the first competition so trying out some of the ideas such as the 1:21 gear ratio wouldn’t be such a bad idea and it wont effect that much. Keep me updated of your progress at school.
If you’re going to use a scissor lift, you may want to consider an alternate means of powering it. The powered rack approach leads to a very poor transmission angle of power to the rest of the lift, which will both limit how far you can safely lower the scissor lift, and create a torque demand that varies tremendously throughout the scissor lift’s travel, spiking to unheard of levels in the lowermost position. Alternatives include gearing on one of the “crossed” joints, or a linear slide that pushes one of the joints upwards. None of these are ideal (a scissor lift is an inheritly inefficient mechanism, due to the number of joints, and aforementioned transmission angle at the sliding joint), but both will dramatically improve your lift’s quality.
Also, there’s no need to fear multistage gearing, if you build it solid. It’s often a necessity. Well designed, it works…there’s a multistage gear reduction inside of each and every motor on your robot.
A word of advice for the top slides; if you can, use 12.5" slides instead of 17.5" slides. The shorter slides are lighter, and every bit of weight-shaving helps.
Given the skepticism, yet the fact that I have plenty of time, I think in five months at my regular four hours a day of work, I think I can get it to work regularly and efficiently
yeah. I mean, the people who had tournaments to go to a few days ago can be rushed, but everyone else?..Just slow down and focus on learning. you make something, then make it better. If that doesn’t work, change it.
You should gear your scissor lift on the bottom bar for like 1:21 so it can go up with a good amount of objects.