A Simple Elevator

[nnfuller]

After graduating I took some time off from robotics, however I will be home over winter break and will be helping mentor my team during their design phase. Over the years I have helped build many robots and systems, but I have never built a elevator/lift. My team is very capable but do not have access to high precision work. They have a small mill and a team member has his own lathe. What would the CD community suggest as a method for building a lift that would have been competitive in the 2011 game? Basically I do not think they have the machining ability to build 254/1114esque lift, however it would be nice to have a solution in my back pocket in case their early designs seek out something like this.

Thank you for your time.

[AdamHeard]

Originally Posted by nnfuller

After graduating I took some time off from robotics, however I will be home over winter break and will be helping mentor my team during their design phase. Over the years I have helped build many robots and systems, but I have never built a elevator/lift. My team is very capable but do not have access to high precision work. They have a small mill and a team member has his own lathe. What would the CD community suggest as a method for building a lift that would have been competitive in the 2011 game? Basically I do not think they have the machining ability to build 254/1114esque lift, however it would be nice to have a solution in my back pocket in case their early designs seek out something like this.

Thank you for your time.

How small a mill? We made a full 60" tall "254 style" elevator on a 14" travel knee mill.

It was actually pretty easy on the fabrication side.

[nnfuller]

How small a mill? We made a full 60" tall "254 style" elevator on a 14" travel knee mill.

It was actually pretty easy on the fabrication side.

It is a SMITHY CX-329
http://www.americanmachinetools.com/...op_milling.htm
Do you have any advice/documentation on your process? I guess my concern was with tolerances on a 254 style system. Had you built a version of this system before the build season?

[AdamHeard]

The tolerances aren't as critical as you would think. If someone knows how to use the mill, their tolerances are likely good enough.

Check out our 2011 prototype CAD (posted in my sig) to see the elevator. Where we did gussets, and a waterjet rack gear, you could do completely different. The overall layout and bearing setup is decently easy though.

We mill 12-14" sections at a time, and then scoot the part down and rezoro off the last hole drilled by just shoving the drill bit in the hole (more specifically, we just leave the drill bit in the last hole drilled, open the vice, full travel X, reclamp vice). We call it "table jumping". We do it for any tubing longer than table travel.

[Brandon Holley]

Also- designing something with built in adjustability can help get around *almost* any machine tolerance issue. Design approach is crucial.

-Brando

[nnfuller]

Originally Posted by Brandon Holley

Also- designing something with built in adjustability can help get around *almost* any machine tolerance issue. Design approach is crucial.

Do you have any examples of an adjustable system like you mentioned? I would be worried about things like adjustment screws loosening, but perhaps others have had success here?

[JamesCH95]

Originally Posted by nnfuller

Do you have any examples of an adjustable system like you mentioned? I would be worried about things like adjustment screws loosening, but perhaps others have had success here?

There are many fastener locking solutions out there, but steer clear of split lock washers. I prefer nylock nuts and Nord lockwashers, personally. There is always safety wire and castle nuts for the supremely cautious.

You can always brute-force it and re-tighten critical fasteners after every match.

[pfreivald]

Bosch Rexroth extruded aluminum with Ecoslide carriages served as our (winch-driven) cascade lift in Overdrive and our (lead-screw-driven) robot lifter in Breakaway.

http://www13.boschrexroth-us.com/Fra...t.aspx?units=1

It was almost shameful how little manufacturing capability we needed to create either device, and both worked exactly as we designed them to. (Mind you, we've learned some about design in both cases, and would make them even better now -- but still might use these products.)

[jwfoss]

In 2011 2168 used 80-20 for our lift and it work out fairly well. With the resources we had it made the most sense at the time. Moving forward we will likely look into something like what 67 did in 2011 (Look under the 2011 Build Season image in this Gallery)

[ttldomination]

Originally Posted by pfreivald

Bosch Rexroth extruded aluminum with Ecoslide carriages served as our (winch-driven) cascade lift in Overdrive and our (lead-screw-driven) robot lifter in Breakaway.

http://www13.boschrexroth-us.com/Fra...t.aspx?units=1

It was almost shameful how little manufacturing capability we needed to create either device, and both worked exactly as we designed them to. (Mind you, we've learned some about design in both cases, and would make them even better now -- but still might use these products.)

How was the durability of the pads on this? Did you notice that the tower was swaying when all the way up high?

When we made our lift with 8020, it was fast and came together nicely. However, it was heavy. One issue that was critical was that when the tower was at its maximum height, the tower would sway. We found that this was because of the play that would develop in the plastic slides (in all fairness, those slides are meant for compression loads). In short, would not do again.

One solution that I found nice was use the iGus products. If I had to do it again, I'd have to track down exactly the types to use, but IIRC, 1771 simply used some super-light c-channel lined with the iGus products. Worked like a charm.

- Sunny G.

[DampRobot]

Originally Posted by ttldomination

How was the durability of the pads on this? Did you notice that the tower was swaying when all the way up high?

When we made our lift with 8020, it was fast and came together nicely. However, it was heavy. One issue that was critical was that when the tower was at its maximum height, the tower would sway. We found that this was because of the play that would develop in the plastic slides (in all fairness, those slides are meant for compression loads). In short, would not do again.

One solution that I found nice was use the iGus products. If I had to do it again, I'd have to track down exactly the types to use, but IIRC, 1771 simply used some super-light c-channel lined with the iGus products. Worked like a charm.

- Sunny G.

We did an 80-20 lift in 2008, and in many regards, it was our best robot in recent memory. (We almost made it to division finals, I believe.)

The first stage was 2x1 80-20 with the standard nylon slides. It was slightly lightened (the back half of the 80-20 was replaced with welded on c-channel), but very similar to a system you could put together in an afternoon from regular 80-20. The second stage used v-shaped rollers that fitted into the grooves in the back of the 80-20.

While that system was fairly simple to design and execute, I wouldn't go with it again. First, it was very heavy, even with the lightening on the first stage. Second, it was poorly counter weighted. And third, the nylon sliders introduced a lot of friction into the system. You really have to pull on it to get it to lift up, and it took two CIMs to raise. I never noticed any sway, but then again, we haven't competed with it in a while.

For the OP: 80-20 is a good solution if you don't want to do bearings riding on the outside of 2x1 tubing (like 254 did in 2007 and 2011). However, don't count yourself out of that design too soon. Almost any design can be modified to fit your machining abilities, so take a look at 973's CAD to see how much machining is really required.

[luciano841]

Team 841 built an elevator system with a drill press and chop saw in 2011. The elevator uses 2x1 square tubing as the outer section, 2x1 c-channel for the center and a rolling device in the center (consisting of 2x1 square tubing connected with flat bars).This elevator design worked very well for us and will definitely use it again if the need arises.

Everything was measured with a tape measure, center punched by hand and then drilled with a 1/4 drill bit.
We noticed that there needs to be enough room for the parts to move within the system, make sure that the bearings do not apply too much tension to the moving components.

Here is a link of our design with 254 and 973.
http://www.chiefdelphi.com/forums/sh...77#post1085150

[pfreivald]

Originally Posted by ttldomination

How was the durability of the pads on this? Did you notice that the tower was swaying when all the way up high?

The ecoslide pads are beastly, and hold together very, very well -- I had forgotten that we didn't even use the carriages on Shiela, just the pads (screwed into the second stage of the lift, inserted into the first stage, which was the Bosch stuff). The elevator we made consisted of two rails spaced almost to the sides of the robot, stiffened with a few small crossbeams made of 1/2" L aluminum. It didn't sway.

http://www.team1551.org/Sheila2_400x600.jpg

Our robot lift in Breakaway used the ecoslide carriage and lifted our whole robot no problem over and over again -- it didn't sway because it had little weight up top: it was just used to lift a hook, and then drew down to lift the whole robot.

[nnfuller]

Thank you everyone for their input. Our team used 80/20 sliders for our minibot deployment in 2011, and we swore them off after that. So I have tried to mock up a lift I think we could build image below:

Specs:

• Two stage Lift with the primary towers built out of 1x2 1/16 wall Aluminum
• Second stage uses 1x2 1/8th wall C stock
• First stage uses bearings in bearing blocks designed to be shimmed out in order to get a precise fit to control front to back motion and the side to side motion is controlled by Delrin slides riveted to the top of the towers and bottom of the first stage.
• The second Stage slides are milled Delrin inserts. These can be milled and sanded until they slides cleanly in a test piece of C channel.
• All of the gusset plates are .050 Aluminum sheet with 3/16 Rivets
• Top black brace is made of 1/4in plywood.
• Since this is a mock up the tower is not adequately braced, but for now im interested in critique of overall design.

[AdamHeard]

Patrick.

The 80/20 and similar extrusions are a solid low resource way to make an elevator, but it is a great weight hit.

I'm not saying don't do 80/20, but just hoping people explore the "254 style" of custom aluminum w/ bearings and realize that it doesn't have to be an insane amount of work. It easily can be a day of manually milling (as ours was about a half day of manually milling for a single robot) by someone who knows their way decently on a mill.

In the end, whatever gets the most robot done in the time it needs to get done is the better option, but I hope people don't assume that because "254 did it..." or did something similar, that it is impractical for another team to do it.

Originally Posted by JamesCH95

There are many fastener locking solutions out there, but steer clear of split lock washers. I prefer nylock nuts and Nord lockwashers, personally. There is always safety wire and castle nuts for the supremely cautious.

You can always brute-force it and re-tighten critical fasteners after every match.

Why steer clear?

Often times on our robots, due to our standardization on #10-32s and our love of lightweight manufacture, we can never even get close to proper preload on a bolt before we destroy the parts clamped. In these situations the spring force of a spring lock washer is helpful.

I agree for properly preloaded joints they aren't the solution, but it's surprisingly rare that we can properly preload on our robots without going to impractically small fasteners.