Hello Everyone!
My team considers using Linear Actuators to climb the pyramid. Are we allowed to use Linear Actuators if it does not violate the electrical and pneumatic rules?
Thanks!
Pre-made electrical linear actuators likely include non-legal motors. They would have to be modified to operate with one or more of the legal motors listed in R32.
If you are using a lead screw, acme screw, or ball screw, without a motor, It should be legal provided you drive it with a legal motor and no other rules are violated.
NOTE: This is my interpretation of the rules and is not official. The only way to get an official answer is via the Q&A system.
My team is considering using a linear actuator to raise/lower a turret. Are there any other limitations regarding size of the actuator?
Begum,
If you would like to PM me with the part number I can give you my opinion off line. Otherwise, you might want to pose the question to the Q&A for an official response.
Depending on the weight of your bot pneumatic linear slide actuator will probably not lift it. We tried it today with a 110 Lb weight and 250 MM and 300MM actuators neither would handle a vertical lift. The other thing to realize is that linear actuators always stay the same length. which may make it difficult to use for climbing.
They are not allowed in the competition because of illegal parts and the pre-made nature of it.
???
Explain please.
A linear actuator is a commercial off the shelf (COTS) item, so it should be okay, as long as you use an approved motor on it (Table 4-1), and the “fair market value” does not exceed $400 (Rule 4.1.3).
Since this is in the pneumatics section, we are talking about pneumatic linear actuators. Thus, no motor is involved.
Rule R78 in Section 4 states you can use a pneumatic cylinder. A linear actuator is just a guided pneumatic cylinder, so I think you’re okay.
However it might be difficult to find one with enough force for under $400. Remember, we can only use 60 psi, so if you needed 150 lbs force (robot, battery, bumpers & a safety margin) you’d the need piston area to be 2.5 square inches (150/60). That’s 1.78" diameter or bore. The next common size is a 2" bore, but those are very expensive, WAY over the $400 limit.
Here are a few listed on Mcmaster Carr.
You can get free cylinders, up to 2"x36" in the KOP via the Bimba PDV.
Yup, and you can use a Bimba cylinder to build your own linear actuator. It probably won’t be as precise as a COTS linear actuator, but you don’t need precise to climb pipes. 
If you’re going to use pneumatics building your own linear actuators are a must to stay within cost. Getting normal cylinders (http://www.mcmaster.com/#standard-air-cylinders/=l2ot0l, using the PDV for Bimba works well too) and using linear slides from somewhere like Igus, 80/20, or Bosch as guides and support works well.
If you only need high force in one direction clever use of springs, surgical tubing, etc. can allow you to cut down the cylinder size. A 1.5" bore cylinder has about 105 lbs of force, loading it with 30 lbs of force from surgical tubing in one direction can give you 75 lbs extending but 135 lbs retracting.
You might also want to do the math on how much of an air charge will be needed to lift the robot using pneumatics (with whatever mechanical assist you’ve got built in).
For a thirty-point climb, we found it rather prohibitive. For a ten-point hang it might be just what the doctor ordered!
FYI -Two years ago, shortly after kickoff, we ordered 2"x24" cylinders from Bimba with the PDV and they arrived the Saturday of the final build weekend.
The smaller diameter ones have always arrived quickly.
According to tests we performed, pneumatic cylinders of the right size work great with pulling a robot up to maybe the first level. Just consider the weight that pneumatics adds to your robot, however.
Thanks, we’ll have to keep that in mind. The 2x8" ones we ordered are pretty integral to our design.