I prefer to be safe than sorry. Especially when the bump and wheel radius are both 2 inches. I’m estimating our robot weighed about 16 pounds
The robot is very heavy, however there is acutally 2.25 inches of ground clearance so it is perfectly fine. Thanks for the advice!
Could you explain how you came out 72 pounds.
I used very minor calculations and threw out a lot of variables that I would normally use.
I knew each motor had 14.6 inch pounds of torque. To avoid risks of stall torque, I lowered each value to about 6 pounds (about 40% efficiency). I saw that the gear ratio was 3:1 because the motor was connected to a 12 tooth gear to a 36 tooth gear(36/12), and there were 4 motors, so the torque multiplier was 12. Multiply 6 by 12 because that’s the torque per motor and the multiplier, giving you 72. I assumed that radius was 1 inch because it used a 12 tooth gear, but a 12 tooth gear is .5 inches, so it’s even more force. But I just threw it out cause i’m ignoring a ton of variables anyways
Restated in math form
-14.6 inch pounds of stall torque= about 6 pounds of usable torque
-12 tooth to 36 tooth=36/12= 3
-Formula= ((usable torque) x (gear ratio) x (number of motors))/ radius = approximate lifting force
-(usable torque) x (gear ratio) x (number of motors) = (6) x (3) x (4)/(1)=72
Other variables I ignored and assumptions I had
-Pressure angles: (power decay due to angled vectors)^(number of gears)
-Friction (hard to use in real life anyways)
-Current weight of the lift system + intake + game pieces or drivetrain
-motors were programmed at full force
-This wasn’t used for hanging (very fatal since I didn’t see the videos at the time). they would need the extra torque to stay in hanging position, or a locking system
-no elastic power
Oh, well that’s good. I forgot that the only things which caught on our drivetrain were the sprockets. So you don’t need to worry.
Thank you very much for your detail post.
I agree with your 72 pounds calculations based on the radius of 0.5 inch. But the arms will easily range from 12 to 16 in depending on the designs, such as 6-Bar or scissor. If the arm is 10 inches, the lift power will drop to 72/10 = 7.2 pounds. Am I right?
For this type of arm I believe the way to solve
144/(amount the arm is lifted for every turn of the 12 tooth gear)
because it is built linearly the height raised is of equal ratio as the power needed.
compared to a lever on a 6 bar being in a circle
Do you guys still have the planetary transmission?
Have you changed any components on your robot since I last saw you at the idea factory?
We had planetary transmission last year. Not going to use it this year because too heavy and high friction. Are you going to use it?
We have been thinking that it could possibly be useful for this years game. However, we don’t have any transmission implemented for this weekends tournament.
So this is what happened when I was making my robot. I intended to have a planetary transmission, so I built a 1X5 c-channel chassis with space for 2 sets of planetary gears and 4 motors. I had it built, it had very little friction, and it worked great, but the torque mode was essentially useless. The chain is simulating a planetary gear, but it does not really do its job very well. It just skips the sprockets, if I had a real planetary gear with teeth and not a frickin chain, it would’ve worked.
Well, the drivetrain is slowed down, it used to be 1:2, but now its internal high speed. Other than that it is all what you can see in the videos! What letter team are you in gladstone?
I’m part of the vex jets middle school team and we like your design. we have three teams:4073a, 4073b and 4073g. Team b and team g are doing 6 bar lifts. teama which is the team I am on is doing a scissor lift. we want to know if you had any problems with the lift because we had problems. team b is working really good and it can score in the cylinder. team g is having troubles with their lift. :(team a just finished the lift and it works good we still have to attach the intake.when we attach the intake we hope it works good. If it does we will try to hang.I want to know if you have problems when it comes to hanging with your scissor lift. Thanks, and can you reply back as soon as possible.
I am from the vex jets middleschool team and I want to fnow if you had trouble high hanging with the scissor lift
High Hanging with a scissor lift is usually fine. With a 4 motor scissor with small pinions on a rack the robot should be able to easily pick itself up. However, you will need a hanging lock to keep the robot up.
Can you guys get over the bump?Can you guys fit in the 18 by 18?Can you guys go under the 12in troph. Because what team 4073a did we can fit under 18 by 18, and go under the 12in troph. we haven’t tested if we gan go over the bump. We are stiil working on it. Can you responed before febuary 12,2014.we are doing a shcrimage with team 4073b and team 4073g. I am talking about your scissor lift. Do you still have it ,because the videos stanley has been posting you have only the 6 bar lift. also we have an idea for the big ball intake. It uses 6 inch leg wheels. Look it up on vex forum and find out what it is if you don’t already know what it is. Team 4073b is using it and it works pretty good.
http://idesignsol.com
On my channel I have videos of my high hanging scissor lift robot. It fits in 18X18X12, I don’t know honestly why you ask that it’s kinda obvious it does. Goes over the bump too…anyway.
http://www.youtube.com/watch?v=-v_ENtly8g4
thank you,I wanted to convince my team to hang.
I had an idea for the big ball intake. It is 6in leg wheels for the big ball intake.do you think it will work. It would look like this except the design of 7793r’s intake.http://botsnstuff.com/w/images/thumb/a/ab/2059ATossUp1.jpg/400px-2059ATossUp1.jpg
Do you see the big ball intake. on this robot. This isn’t team b’s robot it is a random picture just to show you the big ball intake, but do you think it will work.
