pic: FRC973 offseason teaser #7

[Brandon Holley]

I believe I see some constant-force springs on the lift. What force rating do they have and where did you guys get yours?

Looks good! Can we see a whole picture now?

-Brando

[Tom Bottiglieri]

Originally Posted by Brandon Holley

I believe I see some constant-force springs on the lift.

Hate, Hate, Hate those things.

[AdamHeard]

We'll post a full picture tomorrow, we've been so busy preparing that we just haven't really had time for this stuff. It was really hard to get the robot programmed as all the programming mentors just got back to school Monday.

Originally Posted by Brandon Holley

I believe I see some constant-force springs on the lift. What force rating do they have and where did you guys get yours?

Looks good! Can we see a whole picture now?

-Brando

They're 7 lb I believe, from mcmaster. Both mcmaster and sdp-si seem to have a similar and pretty decent selection.

Tom, these guys aren't too bad at 7 lbs, easy enough to handle by hand without cutting yourself (although I have a few times already). The 40 pounder we have but didn't use scares the heck out of me however.

[Audrey Chu]

Sean lied to me! He said you were all too busy with that last robot to build an elevator.......

[rsisk]

Looking forward to seeing your stuff this afternoon!

[techtiger1]

Adam the color scheme on those bots looks really familiar =). I applaud the amount of off-season work you guys do. The robots look great, best of luck in the off season. Tom those elevators in general are not my friends. They work great when they are working but keeping them working is certainly a challenge. As 125 well knows I am sure.

[sdcantrell56]

Originally Posted by techtiger1

Adam the color scheme on those bots looks really familiar =). I applaud the amount of off-season work you guys do. The robots look great, best of luck in the off season. Tom those elevators in general are not my friends. They work great when they are working but keeping them working is certainly a challenge. As 125 well knows I am sure.

Interesting thought on the elevator. We ran an extremely similar elevator all season long that was incredibly quick and never once had a single problem. That is through 3 regionals, champs, and IRI. We're heading to our second offseason in a couple weeks and the elevator still is perfect.

I guarantee you that Adam and company will have no problems with this elevator. The engineering that has gone into it is more than I have ever heard of on a FIRST team.

[techtiger1]

Sean,

We were missing the pesky constant force spring Tom is so in love with haha. So needless to say the elevator cable on our robot if it was full forced powered down would continually jump off our spool. I know 973 probably didn't have any problems with that elevator. We used a similar elevator style setup as well which is why I was commenting.

[Aren_Hill]

Originally Posted by techtiger1

Sean,

We were missing the pesky constant force spring Tom is so in love with haha. So needless to say the elevator cable on our robot if it was full forced powered down would continually jump off our spool. I know 973 probably didn't have any problems with that elevator. We used a similar elevator style setup as well which is why I was commenting.

973's elevator has no spools for anything to jump off of

[techtiger1]

Aren,

I haven't seen there exact setup as I am stuck on the east coast but I actually pm'd Adam to see if would mind sending some pics of their setup or giving some advice on implementing the constant force springs into the design. I am interested to see how they accomplished a similar design better then the one my team used in an effort to try to better my teams knowledge of this mechanism. I thank you guys for your comments.

[sdcantrell56]

The key to not having cable/rope/whatever jump off a spool is to not use a spool plain and simple. We used 25 chain to drive the first stage and then cascaded the second stage. Adam has an even cooler setup but again no spool. As you found managing rope is a pain and is why many teams this year especially avoided it in lift designs.

Originally Posted by techtiger1

Aren,

I haven't seen there exact setup as I am stuck on the east coast but I actually pm'd Adam to see if would mind sending some pics of their setup or giving some advice on implementing the constant force springs into the design. I am interested to see how they accomplished a similar design better then the one my team used in an effort to try to better my teams knowledge of this mechanism. I thank you guys for your comments.

[techtiger1]

Sean after this season I completely agree with your above statement. Trying to find out about all the alternatives and from our teams own opinions on the best way for us to accomplish this better if we do a similar design again.

[sdcantrell56]

I'm a big fan of the chain route and also the way that 973 is doing it, although chain is easier with less machining resources, there's is cleaner though. You can alsu use timing belt like 971 did although it has to be gt2 or else it will slip. Stick to cascading if possible as it is much easier to counterbalance the elevator.

Originally Posted by techtiger1

Sean after this season I completely agree with your above statement. Trying to find out about all the alternatives and from our teams own opinions on the best way for us to accomplish this better if we do a similar design again.

[apalrd]

Originally Posted by sdcantrell56

The key to not having cable/rope/whatever jump off a spool is to not use a spool plain and simple. We used 25 chain to drive...

You could just use a wide spool and thin cable. That would be much lighter than 25 chain.

We used an aluminum tube (2" diameter, about .030 thick) for our spool, with a sprocket on each end (driven by a banebot transmission/550 each). We used Spectra cable (high strength kite string), which is very VERY strong, light, and very thin (roughtly 1/8" diameter). The spool/drum runs between two sheet metal plates that support the elevator, so the drum is as wide as the elevator (about 20").

We used two 20lb constant force springs for 20lb of total force all the way up, which is actually more than the weight of the carrier assembly. So, if you tip our robot on its side, the elevator begins to go up by itself. We decided it was more important to go up fast than down fast, so we like this. We got our springs from Mcmaster. They are "fun" to work with.

[=Martin=Taylor=]

Why didn't you copy 254 to begin with?