We are wanting to try to build a lifting platform that will raise a robot 12". Would it be legal to purchase a screw jack like those used for changing flats and modify it to fit our needs? Reading the manual it doesn’t seem prohibited, but we aren’t sure.
If you can find one for <$400, not hydraulic, and can fit a legal motor to it, it’s fair game.
It’d be legal, but extremely heavy [strike]and difficult[/strike] to pull off. I’d recommend prototyping and playing more to see if you can come up with any lighter options. Pneumatics at the very least.
EDIT: I take back difficult. It’s be pretty easy to buy one of these, rip off the motor, and slap on a versaplanetary with whatever gearing/belt thing it needed. Then bolt it under a ramp. But at 10lbs, I stand by the heavy comment.
Those screw jacks are very energy inefficient and will require quite a bit of power to run.
My suggestion is to look into using a gas shock(s), which are NOT limited to the same 60 psi pressure limitations. Search for gas springs on mcmaster.com to see if there is anything that might work better for you.
Concur with both above. You are planning to lift one of your alliance partner’s robots, right? Team Update01 clarified/modified the definition of a climb:
So you can use the jack (as part of your robot) to lift another robot for the CLIMB, but not your own.
Re Robochair’s suggestion: reasonably priced gas springs available and searchable by stroke length and force at this website.
…but I get all my McMaster orders next morning. It’s literally a less than 16 hour shipping cycle from end of day order to receive next morning before 10am.
More seriously, thanks for that link. I see that they also have CAD models of those parts like McMaster does.
Do the air springs use the air pump to inflate or are they pre-charged and would have to be released somehow to provide lift?
Yes they are pre-charged and you’ll need to manually stow and some how latch the system before the start of the match and then release it once you are ready to lift.
Screw jack models that are up to the task of lifting an automobile with a large safety factor are not light. However you are lifting a fraction of the weight of a car, so can you use the concept to build a suitably sized mechanism that weighs significantly less?
A lead screw is not a very efficient mechanism however it is a compact way to get linear motion and gain mechanical advantage and the type used in an automotive jack do not back drive under the load of a vehicle.
So not a thing out here… part of the price for paradise I suppose…
I need to add here that most jacks have considerable grease on the lead screw. Please read the robot rules about contamination. Particularly R08 and R10.
While we are no longer seriously considering a scissor with lead screw this year, when we were, I figured out that the traditional model of a screw jack is, to be blunt, jacked up for anything with the possible exception of lifting automobiles so you could change their tires. We considered a jack screw 28" wide from pivot to pivot (to fit within both the 33" chassis limitations and more practically half a piece of Versaframe tubing). Trying to drive this “lift” through a screw oriented horizontally results in something that is less than 1/20th as mechanically advantageous at the start of the lift as at the end (we stopped at a 45 degree configuration). After playing with different mount points (and I did a bunch of them), I found (to what should not have been a surprise as I looked back on it) that the most nearly linear way to drive a scissor jack is vertically. That is, have your lead screw lift push UP on either the center joint of the first scissor crossing, or on the first joint above the fixed point of rotation if it’s off to one side. Anywhere else is inefficiently nonlinear.
Gas springs are “pre-charged”. These are most commonly seen in automotive doors which are hinged at the top (e.g. tailgates). They are shipped/sold in the extended state which has the least amount of stored energy, but once they are installed, they begin to store energy whenever they are compressed (the door is lowered).
Also, always install gas springs with the extension rod facing downwards - they have oil to keep the pressure inside, and if you install them upside down, the oil will flow away from the slide and let the gas pressure out.
Slidell ain’t 'zactly paradise, but McMaster doesn’t seem to know about us either.
Inflation has finally caught up.
R12. No individual, non-KOP item shall have a value that exceeds $500 USD. The total cost of COMPONENTS purchased in bulk may exceed $500 USD as long as the cost of an individual COMPONENT does not exceed $500 USD.