I’ve recently just started designing our lifter. Unfortunately, I don’t have permission to release our idea, but what I can say is that we are using a winch type mechanism.
I want to design a small winch capable of lifting just our robot (120lbs) using as many COTS products as possible. Have any of you thought about a design for such a winch.
We are thinking about using two counter-rotating drums that are driven off a single motor. The questions we have is what motor/gearbox to use.
Got a better idea for you, depending on your winch setup. 1 drum, 2 sections, running the outbound cord off one side and the inbound off the other one. I’ve been on a team that did 3 steel cables off one drum, powered by 2 Fisher-Price motors with KOP gearboxes, for lifting a robot.
Setup: the F-P motors are mounted as described in other threads. Each powered one end of the drum through an adapter. The drum itself was lathed into 3 sections–center was the “incoming” cable and the sides were both “outgoing” during a lift. The incoming cable and the outgoing cables were wound in opposite directions.
What I’d do these days, given that that adapter is no longer in the KOP: make an octagon for a FP-keyed shaft interface, and make something similar for a drum of the appropriate size. Or find a source for it.
Thanks Eric and Timy! We have the FP motors, and the small motors left in the KOPs. We might consider ordering a few CIMs.
How does this idea sound? A CIM (or two CIMs) attached to a worm gear/ gear set that turns one drum. To turn the other drum, spur gears are between the two drums causing them to counter-rotate.
Can we use more than 4 CIMs? I forget what the rule is.
<R52>
D. One, two, or three additional 2½” CIM motors (part #FR801-001 and/or M4-R0062-12) in
addition to those provided in the KOP. This means that up to five, and no more, 2½” CIM
motors can be used on the ROBOT.
Thank you Jun! I think I was thinking about a rule from a previous season which allowed the use of only 4 CIMs. Its nice to know that we are allowed to use 5 instead of 4.
Even if you plan on being light (90 lbs + 10 lbs battery + 20 lbs bumper =120 lbs), “the man” is right that you should assum 150 lbs. as your team may want to add future functionality (reset arm, more poerful kicker…) or may have trouble making it to the designed weight. By the rules though, you shouldn’t excede 150 lbs and be competition legal, so that is a better assumption.
You could use a differential windlass principle for a winch. It’s easy to get a tremendous mechanical advantage if you don’t mind using quite a bit of cord. Search on “differential windlass” or “Chinese windlass”. Same principle is used in chain hoists (chain falls). It might eliminate all the heavy, expensive gearboxes.
Oh, perhaps someone can figure out how to use this 33:1 torque multiplier in a winch application:
Also consider that you don’t want the lift to take 15 seconds - design for much faster than that. How many times we’ve seen a nice lifting mechanism, engaged and lifting with 15 seconds to go…and they don’t make it, because their design sacrificed speed for power.
We’re using a similar winch driven by a CIM and toughbox using sprockets and chain. A bifold arm driven by 2 Denso’s extends the hook, a pair of cylinders lifts up the front wheels, we drive up against the bar and lower the cylinders to attach the hook, then retract the arm and start winching. 2 " dia drum on the 3.1:1 winch gives us over 400# lifting force and gets us above the platform in <10 seconds. (in case an alliance member wants to come along for the ride)
We are considering meshing two fisher price motors and gear boxes. we used a similar design in 2007 and it worked well for us. a positive is that they are lightweight and still provide all of the power and speed you would need in a winch. Hope it helps.
we are using a hand wench and changing the hand part to the motor and i cant say much more so i cant tell you much more but try a hand wench that has gotten us this far…
