Helical Loader Help

[IntensifiedAmp]

We want to build a helical loader. Unfortunately we tried different ways (on a prototype) but failed to get a satisfying result on how we would build the helical loader.

We seem to be having trouble getting the exact cuts and measurements for the surface of a helical loader.

Knowing us, it was obviously human error.

So how would YOU go about building a nice, simple, and structurally stable helix for the orbit balls to move through? We've already got the angle we want.

Any help would be appreciated much.

P.S. We'd like to go through many other methods, but Chief Delphi is the best resource you have in experience and which methods work best.

Thank You!

[Dominicano0519]

well i dont have any experience but see if you can get team 25 to help their 06 bot was the best robot ive ever seen as a shooter and they had a helical loading system

[Justin Stiltner]

If you are using a flexible material IE polycarbonate cut out concentric circles, think doughnut shape, then cut one side from the center out in a straight line, and pull the ends apart. Try your methods out on paper, it behaves well like a material such as polycarbonate.

[IntensifiedAmp]

Originally Posted by Justin Stiltner

If you are using a flexible material IE polycarbonate cut out concentric circles, think doughnut shape, then cut one side from the center out in a straight line, and pull the ends apart. Try your methods out on paper, it behaves well like a material such as polycarbonate.

Thanks for the reply Justin,
haha,

That's exactly what we tried. We got a floppy thing going on. Very floppy and it wobbles because of the geometry. We tried cutting it into ovals, because the geometry makes more sense there.

But no luck. Have you tried it before? If so how did you get your geometry to work?
----
We tried cutting the donut in half too. Sure, it works. But.. there has to be a better way.

[lukevanoort]

To be more specific, we're aiming at a helical magazine similar to the ones that teams 66 and 121 made in 2006. Our prototype was made out of 1/32" polycarbonate cut into a doughnut and wrapped around a cardboard tube. When we tried to wrap it around the tube, we were unable to get it to fit right and it buckled when forced into position. Our cuts weren't of the highest quality, but the problems we were experiancing went beyond what I would attribute to our circles not being perfectly round.

[=Martin=Taylor=]

I liked 494/70's approach in the "Behind the Designs" book.

Just get some 1/4" al rod and bend it into a spiral double-rail shape.

Wrap a sheet of poly around it to keep the balls in.

[s_forbes]

I would suggest trying to build one like 469 did in 2006 (picture here). It would probably be easier to build and tweek. If you go to a Lowes or Home Depot you can buy some sprinkler hose, which comes in various widths and lengths and is made of a hard and somewhat flexible plastic. The best part is that it already comes rolled up, so you don't have to deform it much to make a helix.

We just bought 100 feet of 1/2" hose for $14. The hole role weighs only a couple of pounds! (Not like we're thinking of something similar... )

[MrForbes]

Originally Posted by s_forbes

The hole role weighs only a couple of pounds!

I think Steve meant, "The whole roll weighs only a couple of pounds!"

Please excuse his spelling/grammar, he's an engineering student

[907eyci]

there is a book out that has a lot of good 06 bots that use this system use utube it also may help you ( team 694) they have a nice simple one that would not B too hard to build u may wish to ask one of them.

[MrForbes]

this book:

http://www.amazon.com/FIRST-Robots-H.../dp/1592533663

[DonRotolo]

Originally Posted by lukevanoort

When we tried to wrap it around the tube, we were unable to get it to fit right and it buckled when forced into position.

Remember that the center hole is no longer round when you turn the donut into a helix. You may need to trim it a little bit, especially near the 'cut' in the donut.

Cutting polycarbonate with avaition shears may prove useful.

Also, maybe try to be a lot more precise with your cutting? I am sure it can be done...

[MrForbes]

The center hole will "shrink" when you turn it into a helix.

I second the recommendation to use aviation snips to cut the polycarbonate. The red ones always work best for me...

[IntensifiedAmp]

We seem to be doing everything right (which includes that bit of trimming)..
except the preciseness.
Thanks!

What would you recommend as a frame to support the polycarbonate? We have a few ideas and would like a few more comments.

Thanks a lot.

[lukevanoort]

Originally Posted by Don Rotolo

Also, maybe try to be a lot more precise with your cutting? I am sure it can be done...

Our cutting itself isn't too bad (ok, well it wasn't great, but we were rushing). The big problem with cutting appears to be putting an accurate trace on the polycarb for the cutter to follow. Any ideas for making a accurate circle that 20+ inches in diameter?

[Justin Stiltner]

take a flat piece of some material, drill a hole in the end of it sized for your marking tool. drill another 1 radius distance away, and put something sharp there, and hey presto a compass...ish

You can also do this with string, but you need to tie the string to the marker very close to the bottom or leaning the pen in or out could cause your circles to not be smooth.