We will for sure try our best.
Thanks for the tip. Just one question, are you using aluminum on your lift in toss up? Seem to me you are in the game video.
He cut 1x2x1x35 c channel.
The lift is entirely aluminum C-Channels.
The prototype you have posted looks good, if you were to have no load on the top of the lift. You do want to be using the 1x2x1x35 C channels in a scissor lift like this, especially considering the cubes are each over 1/2 kg and the mass of what you want to handle them on top of the lift.
Aluminum C channels to build a reasonably high scissor lift would cost a bit if you don’t have them already, however if you take good care of them throughout the season they are a VERY good investment… it is one of the best and most versatile structural pieces of metal that a team can own so you will use them again and again…
I haven’t built a scissor lift yet, but this year seems like a good year for them.
Good luck on this design!
www.youtube.com/watch?v=fAdXwDMKF2k
I will have to experiment to find out how well they handle the weight. In the video the top of the lift seems heavy.
Yes, although 35 hole aluminum c channels are currently out of stock, they are still on our top list. Maybe i will consider to use aluminum angle and c channel at the bottom, and bars at higher stages.
There are many more places to get the C-Channel than just VEX itself:
From the few scissor lifts I have built, or helped build. It appears more space between the bars on each X, leads to more instability. Many of the best scissor lifts I have seen have little space between the bars on each X.
Thank you very much. Right now I have made the new model and reduced the width to 1.5 inch. Going to post a pic tomorrow, and most likely that is the 1st skyrise lift design we are going to experiment on.
You might be able to avoid this problem, but the fourth vex robot I ever built used 1-bars 1.5 inches apart. The Day before a tournament, the slides at the top of the lift jammed while the lift was going full power upward. The 1-bars bent to about 15 degrees. Not in the weak direction, in the 1 hole wide direction. I had to replace the 1-bars that night and never run the lift above 70 power at the tournament. After that, I scrapped the robot and used a bar lift.
Just so you know, the lift was 3 stages and used 4 motors and was rack powered at the bottom, 1:1 (or 1:1.6? I hated that robot, so I don’t really remember whether they were internally geared for torque or speed) direct driven to 12 tooth gears.
My advice is: try using something a little stranger, like 1x1x1 C-channel. At the tournament, the lift didn’t break, but 1-bar can’t handle as high unexpected loads as C-channel.
Thanks a lot. We are considering that right now.
My major goal is to make the lift as thin as possible, while not adding more friction. The base and lift plan are basically fixed for us, but the intake-- we are really not sure yet. So I hope to leave as much space in the middle as possible.
About directly mounting c channels together with one screw a joint, I am really trying to avoid that, although more than likely we are going to experiment. Because similar to you, I did a two stage scissor lift in toss up, well, without having much experience. It was powered from the bottom, built of the new linear slides. It required ridiculous amount of power at the beginning and was extremely unstable. So we are really trying to do something light, durable and really, really stable.
If you want to get maximum efficiency, then power the scissor lift from a vertical slide connected to the center of the first X. That gives a uniform ratio throughout the lift, because the top of the lift always goes ([num of stages]+0.5)*distance gone by the slide. I still recommend that you use something stronger for maybe just the bottom few stages of the lift, like 1x1x1 C channel, but how you are planning on doing it could be strong enough for what you need it for.
By the way, I measured and calculated that one 25 long Aluminum C channel is only 0.0217 lb heavier than two aluminum 1 bars connected by three 1.5" standoffs (with 6 0.375" screws). If you use 4 standoffs connecting the two 1-bars, that would be only 0.01028 lb lighter than the C channel of equal length.
Just a warning. If you use the scissor lift made of 1-bar connected with standoffs, please don’t fall over onto the field perimeter while at full height carrying 4+ pounds of cubes. At least one stage of the lift would be completely destroyed. :eek:
By the way, a rotationally powered scissor has an upward force of
(torque of motor) x gear ratio(driven over drive) x cos (angle of bars from horizontal) /(num of stages2distance between pivots)
cosine is 0.98 at 10 degrees (from horizontal) and 0.34 at 80 degrees (from horizontal)
I think that is the right math, correct me if it’s not.
Also, you can make 1x1 angle with a vise and sheet metal. In steel that’s $15 for 8 25 long angles, or 1 stage of a scissor lift. And you get 4 1-bars!
That’s as opposed to 13 dollars spent on 8 1-bars! 1x1 Angle is a better deal!!!
In aluminum it’s $25 for 12 angles, and $30 for 16 bars. 1x1 Angle is still a better deal!!!
And by the way, the fact that I am using rows of exclamation points does not discredit what I am saying. !!!
:eek::eek::eek::eek::eek:
The constant ratio lift is my first choice, well, after seeing the game. I actually debated with myself about using either slide or chain to do it… then after some CAD work I discovered it would be too space consuming, considering the size of the cube. The rotational scissor only requires clearance for motors.
The information about aluminum c channel is interesting. We never had them and never thought they were that weightless. Definitely to consider.
About the tipping issue, well… since this is a rotational lift, the weight would be on the back at its full height, since we make the back joint nonmovable. So… in the new prototype I made the anti-tipping bar about 16 inch at full height… will post a picture or a new thread soon, but pretty sure you can guess how to do it.
Edit: one more question, you talked about 111 c channel, it seems that I cannot recall a similar product… are you refering to the old inner linear slide? Or new linear slide? Or self-made c channel? Just wondering.
I did my math using my TI 89 titanium calculator…
I just calculate the function between time and height of the lift under ideal condition (motor free speed), and compare three graphs in the same window. The rotational, verticle and horizontally powered lifts. The trig curve generated by rotational lift seems acceptable.
Self made. It’s a little tricky, but I can make any length up to 17.5" with just a 4.5" wide vise and a 1/4"x1"x8" bar of hard steel. It fits a lot of strength into a very tiny space.
By the way, there are definitely ways of fitting a uniform ratio scissor lift onto an efficient scoring bot :D:D:D:D:D