hello!
I am currently trying to figure out the best intake system for a scissor lift. I am thinking that side rollers could be helpful, but I am also thinking there could be better way to intake the cubes. Any help would be very appreciated!
See relevant threads:
https://vexforum.com/t/best-skyrise-lift-intake/26686/1
https://vexforum.com/t/best-type-of-cube-intake/26657/1
[https://vexforum.com/t/idea-brainstorms-for-vex-skyrise/26236/1
and to answer your question, itās all up to what your robotās design requirements are. Are you looking to hold a large amount of cubes at once, or just 1 or 2 at a time? Do you want a speedier robot that quickly owns posts, or a āNuclear Optionā robot that can completely shut out a goal? Itās all up to you.](https://vexforum.com/t/idea-brainstorms-for-vex-skyrise/26236/1)
https://vexforum.com/t/best-type-of-cube-intake/26657/1
[Idea Brainstorms for VEX Skyrise!!!! - VRC > Skyrise (14/15) - VEX Forum
and to answer your question, itās all up to what your robotās design requirements are. Are you looking to hold a large amount of cubes at once, or just 1 or 2 at a time? Do you want a speedier robot that quickly owns posts, or a āNuclear Optionā robot that can completely shut out a goal? Itās all up to you.](Idea Brainstorms for VEX Skyrise!!!! - VRC > Skyrise (14/15) - VEX Forum)
Iām thinking a speedier robot and just a few cubes. Would an elevator be more beneficial than scissor lift?
Iād say, for your purposes, an elevator might work out better. I donāt have much experience physically building either mechanism yet, but from what Iāve gathered on the forums (and from personal CAD experience) each lift mechanism has itās pros and cons. Weāre using a scissor lift primarily because of our design goals (Be able to reach every goal and skyrise section) but your goals may be completely different, in which case the robotās needs will change.
I will say this: Be sure to lubricate the slides on your lift. Everybody seems to be talking about using white lithium grease. Do everything possible to completely minimize friction. That would go for an elevator or a scissor.
Are you planning on reaching all of the posts and all of the skyrise section increments?
Yes my team would like to have the ability to reach that high up. We actually have build a lift that currently goes that high; however, we might change the lift design.
If i were you i would just make a flying robot so you dont have to deal with lift systems. Then other teams can use the parts from your scissor lift
I see what you did thereā¦
No but seriously a scissor lift is a slower stronger lift for heavier loads. If you plan to pick up a few cubes and be faster a double reverse four bar would be more ideal.
I can vouch for this. Iāve got a robot that currently can pick up 2 - 3 cubes, build a full height skyrise, and score cubes in all height goals including a full height skyrise. I could give some help if youāre looking for a RD4B.
Is a double reverse 4 bar a fast lift compared to a scissor lift?
A well built scissor lift on a fast gear ratio can go quite fast
Neither is necessarily faster than the other. It all just depends on how you build it and gear it.
Which lift would required more torque?
Again, we canāt make blanket rulings for all lifts under the same category. It depends on size, slop, friction, material itās made of, and the intake. You should be using math to determine which will take more torque. Donāt just post every question you have, and expect others to tell you what to do. 1st person testing is more valuable than words in a forum.
Again, itāll depend on how itās built, materials, gearing, etcā¦ It really wont be that big of a difference as far as speed and torque requirement, as long as it is built correctly. I have seen both types of lifts work very well, and very poorly. Try building some prototypes, I know that is what helps me better make a design decision. Good luck!
when it comes down to which lift requires the most torque think of it this way
efficiency
you are taking a power source (rotational force, that is torque, from motors)
transfering it into lift movement
and get the end result of kinetic energy(the lift going up/down)
now, the input force will alway be greater than the output force because of defficiency of the lift
different lifts are more efficient than others, and also depending on how well built they are. Factors that affect efficiency of lifts include friction, and vectors(angle of force relative to the linkage/etc.)
elevators have a lot of slides, 1103ās lift worked really well, but note that it only had to go ~35", not 60" 1103ās 2 stage lift had much less friction that a 4-5 stage would
scissor lifts have average 4 slides, compared to 1103 2 stage lift that had 6
most of the energy lost in scissor lifts is finding an efficient way to power it(vertical or rotational), and also in the many joints it has. Scissor lifts have a lot of joints due to the amount of stages. However joints have much less friction that sliding parts underwieght. This is why i think that for a 60" lift scissorās are more efficient than an elevator
double reverse 4 bar is also much more efficient than an elevator, because it has no sliding parts, only joints.
torque/speed/gear ratios
so what dictates the speed and torque requirements of the lifts?
the more efficient you are in transfering your torque into vertical movement, the lower gear ratio you can have, and the faster your lift will be with the same amount of torque versus a less efficient lift that is slower, uses a higher gear ratio, and uses the same amount of torque
this is why i think that an elevator would be slower than a scissor of double reverse 4 bar.
Obviously if you wanted to you could make one faster than the other but in general a reverse 4 bar is faster and a scissor is stronger. You could make a reverse 4 bar strong with a huge gear ratio but it would be ridiculously slow which defeats the purpose of a reverse 4 bar. Likewise a fast scissor could lift next to nothing. So i see what you guys are saying that it depends how you build it but each lift has a speciality.
Iāve noticed some things while prototyping all of these different types of lifts. If you turn a scissor lift sideways, you get a mechanism identical to an 8 bar or 6 bar or however many bar-red lift you want. Similarly a reverse double 4 bar is like a scissor lift but with half has many bars; one joint is removed at each stage. So itās interesting how reverse double 4 bars are thought of as fast, but not as strong as scissor lifts. Scissor lifts just have more bars and joints. The reason scissor lifts are slower is the linear slidesāmore friction, and it is difficult to keep forces perpendicular to both the slide and the bars of the scissor lift. From what I have seen and played around with. Any kind of 6 bar or 8 bar will not be that effective this season because the cubes are too heavy and parallel bar linkages create a cantilever which would make the robot unstable. Also because of the weight of the cubes and the height they have to go, reverse double 4 bars do not have the support or the stability to hold more than a cube or two. Reliable, not necessarily fast, linear lifts will win this game.
The thing to remember with RD4Bās is that because there is two arms to them, if you have a 7:1 gear ratio, it is twice as fast as a normal 4-Bar lift with a 7:1 ratio. So you could infact have a gear ratio of close around 13:1 or 15:1 and be the same speed as a normal 4-Bar with a 7:1 lift but with added strength.