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)

[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.

[Taylor]

When we did our 8020 lift in 2011, we found it to be a very simple, machine-less system. I can't speak on behalf of all 8020 distributors, but ours was happy to visit our site and work with us on our design and what parts we'd need to create it. We had to do minimal (read: a couple dozen holes drilled) machining on the system.
8020 also extended a FIRST team discount to us.
Our 2011 robot was far and away the simplest and most effective robot we've produced in our eight seasons.

[Brandon Holley]

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?

Adjustment doesn't necessarily mean "turn a screw to adjust". It can be just a plan of attack on how to tweak things when you get down to your final configuration/implementation.

For our 2011 elevator, we used Teflon pads on the outside of the 1st inner stage of our lift (http://www.chiefdelphi.com/media/img...e4ed3dc_l.jpg). You can see the white little skids on either side up near the top of the elevator.

Knowing these were going to be our primary mechanism to eat up the tolerance stack up from the welding of all the assemblies and machining of the necessary brackets, we knew we were going to rivet these things on with countersunk rivets and shim stock behind them. The shim stock was the adjustment for the side to side slop. We only needed to tune it once on our final assembly and we were set for the year.


Just an example of how you can build adjustment into a design with part of your assembly. It doesn't need to be as elegant as bolt adjustments and the like, but of course pulling those off can be cool as well.

-Brando

[liam.larkin]

Want to 2nd, 3rd and 4th what many have already posted. We (272) have used 80/20 as the primary structural component on our lifts for years. 2004, 2007 and 2011. It has always served us well and we have little to no advanced machining capability. If you would like drawings (STEP files), pictures and/or videos illustrating our design please feel free to send me a private message and I will dig those up for you. GOOD LUCK!!!!

[JamesCH95]

Originally Posted by AdamHeard

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.

Link to older post.

Split lockwashers can cause bolts to work loose from vibrations sooner than normal. I'm coming from mostly automotive experience on this one, and have had miserable luck with split lock washers. I now avoid them on principal and haven't had an instance where I wish I used them (car, robot, or otherwise).

A belville or wave washer (or even an o-ring under the bolt head) might work for what it sounds like you're doing. But if you've never had an issue it's hard to argue with empirical evidence on FRC robots.

[BJC]

Wildstang had one of the simpliest to make elevators in 2011 and ended up World Champions. It was basically many C channels. You should contact someone on their team about some pictures or tips and tricks on that elevator.