Chain Driven Telescoping Arm

[BadKarma]

for class i am planning on making a telescoping arm, now my question is how could i run this arm on a lopped chain drive? I am very curious to how team 56's arm ascends up and down from their chain drive and if there is anyway i could apply this to my own project. both sprockets look hard mounted and i cannot seem to figure out how it works. any suggestions or help is appreciated.

[KenWittlief]

Last year team 578 had a telescoping arm, with a chain that was pushed up the center of the tube.

The only mistake we made was using a plastic chain, the links kept shearing on us. A metal chain version would have been great.

[Kevin Sevcik]

I'm vaguely hoping you meant Team #57, as we had a chain driven 2 stage telescoping tower. It was triangular, and had lots of lightening triangles to turn it into a lovely trap for fingers. (No, it didn't ever get used that way, thankfully)

If so, I'll have the kids in charge of it get in touch with you and explain things, since they're the ones that are up on all the details on it.

[Deetman]

Team 1014 used a chain driven telescoping arm this past year. What we did was we had our sprockets on the outside of the larger box of the arm, and the chain would actually run inside this larger box. In the smaller, telescoping part we had holes tapped in 2 places that we put a small screw into that also went down through the #25 chain. The length of the telescoping motion prevented the screws going through the chain from ever getting to the sprockets. This worked surprisingly well. It never broke and when we needed to take the telescoping part of the arm out it was very quick and simple.

Some pictures:
This is looking up the inside of the larger box without the extension in it.


Overview of the robot (you can see the chain routing)


Unfortunately I don't have any pictures of the attachment of the extension to the chain and I don't really have access to our robot to take a picture for you. Feel free to look around our gallery at www.dublinrobotics.com to see if there are any other pictures that can help you out.

[dez250]

It just happens JVN covered earlier how he built the Ribbon Cutter Vex Bot stage extention with a chain drive. Check it out and see if that helps.

[David Guzman]

Team 1251 used a telescoping arm this year, it is pulled out with strap but you can apply the same concept with chain. In every place the strap bends we use UHMW rollers to reduce friction. We used a window motor connected to a pully to pull the strap, overall it works great, it is not as strong as chain but it served the purpose.

I made a quick sketch of how the straping goes. You can also find pictures of the robot here:

http://www.chiefdelphi.com/forums/sh...ght=techtigers

I hope this helps, and good luck.

Dave

[Ronald_raygun]

About this whole chain operated arms, does anyone know the concept behind team 233's arm? That thing went up fast.

[David Guzman]

Originally Posted by Ronald_raygun

About this whole chain operated arms, does anyone know the concept behind team 233's arm? That thing went up fast.

I'm pretty sure that the set up of the chain is very similar to the one I posted before, but their arm is so fast because they used two Fisher Price motors with a reduction that pulls the chain very fast. I was talking someone from their team and he was telling me that it could fully extend in 1.1 seconds, which I find amazing.

Dave

[Doug G]

We did something this year similar to what David described using nylon strap to extend our telescoping arm, I would strongly look at using a lighter material than chain. Chain may be good option if your planning to lift several hundred pounds, but for what we encounter, the nylon strap is more than adequate, easy and cheap to acquire, low friction if you use UMHW rollers, and you can have telescope stages within a 1/4" of each other. Ours is shown here .