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-   -   Elevators: Cascaded vs Continuous (http://www.chiefdelphi.com/forums/showthread.php?t=110011)

jspatz1 14-12-2012 10:42

Re: Elevators: Cascaded vs Continuous
 
1 Attachment(s)
Quote:

Originally Posted by Jared341 (Post 1201554)
I have often heard that cascaded elevators require a return drum of a different diameter than the feed. But wouldn't the following work?

Each segment of the elevator can have a closed loop of belt/chain attaching it to the prior stage. It should be anchored at the top of the previous stage (or motor for the first stage), and the bottom of the next stage. It's important that the total length of the loop doesn't change as it travels up and down.

You still have the speed and force multiplier effect with each stage, but you won't have to worry different feed and return speeds.

My aging brain is not visualizing this, perhaps you could sketch it. The purpose of a return/take-up cable is to drive the elevator down as well as up. You could create a closed loop cable between the 2nd and 3rd stage, but it would not drive the 3rd stage. Remember that the lift cable for the 3rd stage is anchored to the 1st stage, not the 2nd. It therefore needs a corresponding return cable which is also based on the 1st stage (the 2X take-up). It is a closed loop overall, but not between stages.
We solved the 2X take-up issue by making our winch drum a 2-stage drum (photo) with the return stage 2X diameter of the payout stage. Made the cable rigging quite simple.

Jon Stratis 14-12-2012 11:19

Re: Elevators: Cascaded vs Continuous
 
Quote:

Originally Posted by jspatz1 (Post 1201823)
We solved the 2X return cable issue by making our winch drum a 2-stage drum (photo) with the return stage 2X diameter of the payout stage. Made the cable rigging quite simple.

Funny, we did exactly the same thing when we did cascade!

Jared Russell 14-12-2012 12:43

Re: Elevators: Cascaded vs Continuous
 
1 Attachment(s)
Quote:

Originally Posted by jspatz1 (Post 1201823)
My aging brain is not visualizing this, perhaps you could sketch it. The purpose of a return/take-up cable is to drive the elevator down as well as up. You could create a closed loop cable between the 2nd and 3rd stage, but it would not drive the 3rd stage. Remember that the lift cable for the 3rd stage is anchored to the 1st stage, not the 2nd. It therefore needs a corresponding return cable which is also based on the 1st stage (the 2X take-up). It is a closed loop overall, but not between stages.
We solved the 2X take-up issue by making our winch drum a 2-stage drum (photo) with the return stage 2X diameter of the payout stage. Made the cable rigging quite simple.

Here is a picture of what I was envisioning.

The motor is directly connected to a continuous belt/chain/cable around only the first stage which is anchored to the bottom of the second stage. Thus the motor can drive the second stage both up and down. The rest of the system is constrained based on these two moving parts.

Basically, it is a conventional cascade lift, attached to a cascade "lowering" system.

Wayne TenBrink 14-12-2012 13:04

Re: Elevators: Cascaded vs Continuous
 
Quote:

Originally Posted by jspatz1 (Post 1201823)
My aging brain is not visualizing this, perhaps you could sketch it. The purpose of a return/take-up cable is to drive the elevator down as well as up. You could create a closed loop cable between the 2nd and 3rd stage, but it would not drive the 3rd stage. Remember that the lift cable for the 3rd stage is anchored to the 1st stage, not the 2nd. It therefore needs a corresponding return cable which is also based on the 1st stage (the 2X take-up). It is a closed loop overall, but not between stages.
We solved the 2X take-up issue by making our winch drum a 2-stage drum (photo) with the return stage 2X diameter of the payout stage. Made the cable rigging quite simple.

Each moving stage acts as a closed loop, but the linkage involves the two stages before it. For example, the cable (belt, chain, etc.) would be anchored to stage 3, run over pulleys at each end of stage 2, and be anchored to stage 1. The stage 2 cable would be anchored to stage 2, run over pulleys on stage 1, and be anchored to the non-moving chassis/frame. The stage 1 cable would be anchored on stage 1, run over pulleys on the chassis/frame, and be anchored/attached to the drive drum. The ends of each cable terminate at one anchor point which includes the tensioning adjustment. The other anchor point for each cable is normally a clamp restraint on a continuous section of the cable. When loosened, it allows for adjustment of the location of that stage relative to the other stages. It doesn't matter which of the stages the different anchor points are on.

We have used both methods (continuous and cascading). Both work fine if done well, and both stink if done poorly. My advice is to use a design that allows for easy access to cable tension adjustment and replacement, and make it so that the cable cannot come off the pulleys when tension is lost.

jspatz1 14-12-2012 14:01

Re: Elevators: Cascaded vs Continuous
 
Now I get it. Clever. Gets rather complex with double the cables/belts and pulleys, but it would work. I would probably still choose the 2X take-up reel, it is easy to do and greatly simplifies the rigging.

EricH 14-12-2012 19:17

Re: Elevators: Cascaded vs Continuous
 
Quote:

Originally Posted by Wayne TenBrink (Post 1201849)
Each moving stage acts as a closed loop, but the linkage involves the two stages before it. For example, the cable (belt, chain, etc.) would be anchored to stage 3, run over pulleys at each end of stage 2, and be anchored to stage 1. The stage 2 cable would be anchored to stage 2, run over pulleys on stage 1, and be anchored to the non-moving chassis/frame. The stage 1 cable would be anchored on stage 1, run over pulleys on the chassis/frame, and be anchored/attached to the drive drum. The ends of each cable terminate at one anchor point which includes the tensioning adjustment. The other anchor point for each cable is normally a clamp restraint on a continuous section of the cable. When loosened, it allows for adjustment of the location of that stage relative to the other stages. It doesn't matter which of the stages the different anchor points are on.

330 did that for multiple years (1999, 2000, 2001, 2004, with a single-stage moving piece in 2002). No variation in drum diameter between up and down cables; the return cable simply attached at the top and fed back to the drum. The main issues with those lifts (all blue, all cable-driven) were when cable needed restringing--break out the aircraft cable crimpers and sneak them in somehow to make the crimp. I can't recall tensioners being used at all.

The other issue I can recall was a direct result of two FPs trying to drive the lift down past its hard stop in 2004. I think we were able to bend the C-channel back to normal; I do know that it held up through the rest of the regional and the Championship and offseasons, and if we powered it today it'd probably still function.:D


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