Arm mechanism
 

How does having a telescoping arm sound with rollers inside??

Re: Arm mechanism
 

sounds good. you would have to have a way to keep it from tipping over though.

I personally would go with the 80/20 w/ linear bearings approach using cable and pulleys.

-vivek

good luck!

Re: Arm mechanism
 

yeah i know we have some 80/20 but its really heavy so we dont know yet we are thinking about it though and we have to arms probably from pneumatics that would come out to stabilize us

team 2191

Re: Arm mechanism
 

Prototype!

Re: Arm mechanism
 

we are prototyping and its not that bad.....yet

Re: Arm mechanism
 

hmmm... seems like good ideas, im just worried about air supply volume. in our teams designs, my students are worried about the number of cycles available per actions. for example a (1" bore) 6" stroke piston to move arms, or lift a ball - how many cycles are expected. we've tested a huge 18" piston we had laying around and we got 1 out stroke and on the return stroke our compressor kicked in. this makes it difficult to incorporate/ simplify designs.
any input from the vets?

Re: Arm mechanism
 

I would be very, very worried if I were you and planning on using pneumatics to lift the ball up that high. There simply isnt enough air there to continuously hurdle.

-vivek

Re: Arm mechanism
 

in my experience u have to clean ur rollers often, or they will "lag" or stutter. maybe a lead screw. thats what we used on our robot last year to telescope are arm. it worked very well and was pretty quick.

Re: Arm mechanism
 

Fortunately you don't have to continuously hurdle, you pretty much have to make a 10 to 15 second or more lap between hurdles. Which seems to be plenty of time for the compressor to catch up.

Of course we're only planning on having to move about a pound or two of metal up about a foot to shoot, the ball has to move the rest of the way on it's own!

Re: Arm mechanism
 

It sounds like "whirr" if you do it right, and "clack clack grunge snap @$@%^!!" if you don't.

You may also want to look at the IGUS bag of materials and contact them about their YES program. IGUS is very generous about donating some excellent materials to teams, so if you see something you like in the KOP and would like more, you should contact IGUS with your ideas.

There is also a powerpoint on lifts and how to build them on the FIRST website somewhere... anyone got the link to that one?

Jason

Re: Arm mechanism
 

In 2005 we had a telescoping arm which had HDPE (High-density polyethelene) blocks inside on which the aluminum rectangular form slid, instead of rollers. The friction is quite low, the simplicity, stability and durability quite high. Let me know if you need more details.

Don

Re: Arm mechanism
 

We did the same thing (same year too) and I would warn against it. Although the basic design is solid, we discovered that HDPE blocks cut in dry, cold January don't work too well in humid, warm Atlanta. Instead of HDPE, I would used UHMW (Ultra-High Molecular Weight) Polyethylene, which doesn't have those problems (or, at least, not anywhere near as bad).

Re: Arm mechanism
 

Can someone please email me with details on how to make a telescoping arm because i dont really understand how to make one or even how it works.

Re: Arm mechanism
 

Is Building Competative Manipulators by Greg Needel the one you are thinking of?