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Originally Posted by artdutra04
To solve for the forces/speed of elevator, look no further than reducing everything to free body diagram(s). Remember in a free body diagram we want everything to equal zero in static calculations (which we have simplified this to). We are neglecting the weight of the elevator parts in these diagrams. Also, we are assuming all rope forces are perfectly vertical (which they should be if you designed the elevator right)....
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Ah, that's exactly what I needed. Thanks for drawing those out, and I see where I messed up on my own diagrams.
Quote:
Originally Posted by DampRobot
Could someone (Adam?) go into a bit more detail about rigging the cabling in an elevator? For example, what type of cable is best, how do you deal with tensioning and stretching, and how do you tie it off the best? What are good ways to attach the cable to the drum, how do you keep it from getting tangled, and what are good ways to do pulleys?
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If you look at RAMP's latest videos, there's one that goes into detail about elevator rigging and such. There's a video coming that's going show the elevator rigged with #25 chain. Although, if you have a request for more detail, perhaps send a message directly to Adam Heard or the 973 Ramp youtube account.
In the past, my team has used whatever pulleys are available on McMaster. If you want to go custom, you can purchase the pulleys and then make your custom brackets and everything, but for us, it was easier to go COTS for the entire assembly.
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Originally Posted by Jon Stratis
Let's imagine a 2 (moving) stage elevator.
Continuous means you have a single cable that runs through every stage. Whel you pull on it, you'll (usually) have just the smallest stage moving (the one your mechanism is attached to, holding the game piece). Pull up 4 ft, and that stage moves up 4 ft until it hits the top. At this point, that stage is motionless, relative to the next stage. That next stage then starts moving, and if you pull another 4 ft, you get 4 more ft of movement. So in the end, 8 ft of pull gets you 8 ft of movement.
Thus, continuous results in the same size spindle for both up and down.
Cascade is a little different. The wire from the motor hooks on the outer stage, while the inner stage has a wire that goes over the outer stage to attach to a fixed point. So, when you pull on the wire, you start moving the outer stage, which also moves the inner stage. As a result, pulling 4 ft of wire pulls the outer stage up 4 ft, and the inner stage up 4 ft relative to the outer stage - 8 ft total. As a result, to power it down your spindle needs to be twice as big to give you twice the distance for the same rotation.
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Oh, so, I see. I suppose cascade has two variants: one where each stage is powered with a closed loop and one where the loop is closed when the carriage is attached back to the "spindle." That makes a ton more sense.
- Sunny G.