helix
 

ok CD we could really use your help. we are a FTC team and for this years game we are tying to make a helix so if you could add your input that would be great

would it be better to use a stiff bristle or a soft bristle. mind you we are picking up whiffle balls

would the pick up bar be better direct motored or chain/gear driven??

remember we are using the legal FTC KoP so keep your FRC minds a little bit retained

thank you

Re: helix
 

Prototype both, see which works for you. I'm not trying to be sneaky and not tell you the answer, honestly the best solution is to try it and see.

Good luck.

Re: helix
 

we have tried out a stiff bristle and this seems to work but our team is having some discrepancies so i decided to come and ask the CD world and see what every one else preferred because this past FRC season we watched some matched and there were some of each so this is really throwing off all of our plans because as a team we cannot decide

Re: helix
 

definitely need to experiment. We used the grippy stuff (shelf liner) for our FRC helix robot for Lunacy. We made flaps of it that would stick out of the center tube. Worked great.

Re: helix
 

There is no single answer to this question. Finding the right balance of bristle stiffness, density, and length is almost impossible to do without playing with different combinations until you find the one that works best.

Re: helix
 

well thanks for that picture but the only thing we have along the line of shelf liner is non-slip padding. as far a bristles we have tried zipties and they seemed to work ok but we are looking for other ideas as well. what sugestions are there for the drive of the center rod????? either chain driven of direct motored?

Re: helix
 

Not being involved in FTC I'm not sure what parts are allowed to be used this year, but I have seen effective spirals made out of strip brushes (from McMaster), paint brushes, hair brushes, sheets of lexan, tubing (like the picture posted in this thread), cardboard, zip ties, hose clamps, and many other materials.

Re: helix
 

For the drive of the center rod, you want to keep it compact so whatever works for you.

As for what the material would be, if you attach a tube of PVC to an axle connected to your drive on the top, and then with an idler axle at the bottom, it should run pretty smooth.

I don't think you need to use more than one motor for the helix drive, probably geared for torque.

Re: helix
 

We have a team here who did a ziptie tree with a helix design it works great

Re: helix
 

zip tie trees. PVC trunk. I leave the rest of the fun to you. but make sure the zip ties arent to stiff.

Re: helix
 

If you have any, try using the pnuematic tubing that comes in FRC kit, it works great, and once balls get to the top of your helix, they bend so your helix-tube can keep rotating.

this worked great for out 2009 lunacy robot,



ps. If you need them to be stifffer, just shove zip-ties inside the pnuematic tubes.

Re: helix
 

You can use a little surgical tubing, right? That's fairly grippy. Prototype that if you want to try something other than zip ties.

You can get various different FTC legal zip ties of different stiffnesses, try stuff out. You want enough force that it will propel the balls, enough flexibility so that you can keep the helix running with balls at the top without forcing them through the shooter mechanism, and enough stiffness that balls will not roll out the bottom. If you've achieved this, maybe you don't need to look for more solutions.

This is assuming you're using a helix that goes "up". If you're using one that goes "down", test and see if you need anything other than gravity. You might not.

As for how to power it, whatever works best for your design. In FTC I preferred to use gears whenever possible (granted this was vex). They all get the job done.

Re: helix
 

yes we are doing a helix that does go up and not down and you make a valid point with the surgical tubing yes we are alloud to use that materials. as far as the different zip ties of stiffness could you sugest some zip ties that are not super stiff because we do want to keep out center post moving. we are going to probably use a PVC pipe as a center of the "helix tree"

Re: helix
 

we have no sort of pnuematic tubing at all so that was a great idea and we did see a lot of that in FRC but that is not an option for us

Re: helix
 

I guess how you have the shaft driven really depends on the motors your using and the space you have. 1766 made a robot in 2007 that was a direct drive system and it worked great. The only problem was that we had about a 1 inch clearance in between the two motors. If you don't have room for it, there really isn't much loss in using gears. One suggestion is to mount the rotating center on a bearing so that the downward force isn't being applied to the motor. I know this might seem like common sense, but I've certainly overlooked things like this before. So far, I've gotten lucky. But I've been trying to not push my luck.