How to Lift

If you would have two 393’s on lifting a six bar what would be your choice of gear ratio or lifting method

  1. Would you use a gear ratio (if so what would it be)
  2. Would you use linear slides
  3. Other
  4. Would you set your 393’s to Torque or Speed
  1. Yes, 1:7 (12t:84t), 1:7 is most controllable and has a good speed.
  2. Depends on intake, if you have a vertical style intake, similar to 1200 Syntax Error’s then go for linear slides. But if you have angled intake, I suggest going with a six-bar.
  3. Torque.

Would you advise against a 1:5 (12t:60t)

I would not advise against it, but for the sake of controllability and reliability my suggestion would be 1:7. With the higher gear ratio there is a less chance of your lift motors overheating.

Going 1:5 is certainly possible and can be easily done, but I use 1:7 and have never had a problem with the lift being too slow.

i suggest you have height pre-sets if your going to make your arm that fast but other than that you should be fine. as long as the ratio gives you as much torque as you need

WE have a lot of weight on our arm do you think that 1:5 would still be fine
Anyway Thanks For Your input :slight_smile:

You could try the cam wheels. It has not been tried before, but with a pot you could accurately control a four or six bar. It would probably also relive stress on the axle. Granted this is all theoretical and I have never tested this, but I came up with it when I was considering uses for the new advanced motion kit.

1:7 if u have a heavy arm
(although it CAN be balanced out by elastics)

We had 1:5 on our last robot and it worked well. The only problem was that we literally had to split up 100 rubber bands in 8 different places in order to make it work.

Similar in use to a linear slider rack is to use the linear-screw in the new advanced mechanisms kit. It should be good to avoid backdrive

I use 4 269s at 1:7 and that works amazingly, I did have 1:5 with the 4 269s but the motors burnt out really easily, so I suggest 1:7 especially if you have a heavy lift, I also suggest putting elastic bands on it as well

Mark

We should’ve used a six-beam… Our scissor lift requires a double torque ratio (I don’t know if there’s a name for it). What we have is:
12:36, and then 12:84, with the 36 tooth gear on the same shaft as the second 12 inch gear. I think the full ratio is 1:10, and we’re using 269s with elastic!

12:36-12:84 is 1:3-1:7 is total of 1:21
If you have a two-stack scissor lift, then the final stage moves 2x as fast as first stage;
Eqv ratio is 1:10.5

Comparing gear ratios for Arms without knowing length of arm, or if the load is concentrated in a vertical stack at the end of the arm, vs distributed in a ramp up the length of the arm
is like
comparing wheel drive gear ratios without saying what size wheels are used,
or how many motors are connected, (“we’re using 269s with elastic!”)
or what type of motors they are.

O.o that’s 1:21 u got thergah, he beat me to it

Our scissor lift is 3-stack so that our manipulator can hang over the 30" goal and block other teams’ scoring attempts while we’re scoring or defending (it works very well in the autonomous mode; all other teams that try to score in the same goal as us in the autonomous period fail to score due to our blockage). I didn’t know that the double ratio multiplied the torque. Perhaps we can change down the 12:84 to 12:60 for more speed.

Sorry jgraber that is a typo. I meant to say we use four 269s. We have 24 strains of elastic on the lift. Here is a picture:
Note that the picture is slightly out of date. The pneumatics are no longer present.
http://vexraptors.weebly.com/uploads/6/6/6/2/6662532/1325297733.png