I’m also woking on researching and designing a big turret. Any thoughts, advise, examples or tips? I know that 25 has a really really nice one.
114 has our old one from 2006 - It’s rather well designed and very accurate - albeit perhaps on the heavy side.
Talk to a Rex114 about it.
Check out this post by Wayne Cokeley about 25’s turret design. In addition, depending on your application (ie, how much of an unbalanced load it has to hold, and how far out) large diameter lazy susan bearings from your local hardware store may work fine.
Going in the opposite direction, radio amateurs often use novel mechanisms to rotate large or larger antenna arrays. A goodle search on “moonbounce” or “large antenna array rotator” should turn up some good info.
Some have even used army surplus tank turrets for that purpose.
Like Luke said, it depends on the load and unbalance you need to deal with.
Don
Check out out 2006 AimHigh shooter… had a suspended shooter turret, great double-bearing system, was very light (less than 5lbs, can’t remember exactly, know the whole superstructure of the robot weighed 15lbs), accuracy of +/-0.5deg.
If you want more info let me know.
-q
also, try talking to the martians. They’ve been building turreted arms for quite some time now.
Make sure your gears are strong, especially if your turret is going to take a lot of abuse. At one regional, we stripped off eight teeth on a fourteen tooth gear. :eek:
Titanium? 
You can read about a lot of great turret designs in FIRST Robots: Behind the Design. Not only are the descriptions more in depth then you would normally find in a chiefdelphi discussion, there are a lot of great pictures as well.
696 did a nice one in 06. Won them the Innovation in Control Award. Here’s a pic. http://www.chiefdelphi.com/media/photos/23631. It was comprised of 4 rings. Inner and outer, and then an upper and lower of each. Each ring had a 45 degree chamfer milled around it. When placed together, inner, outer, upper, and lower, these chamfers would form a diamond shape. In this groove rode alternating steel and delrin balls. This groove gave us 4 points of contact on the balls, so that the turret could be loaded in any direction (axial, radial) and still rotate buttery smooth. It’s large diameter made it quite stable.
Especially check out 111’s turret design. I’ve read that write up at least 4 times and my mouth keeps watering.
I would suggest checking out 75’s Turret
http://www.roboraiders.com/showcase/assets/images/assemblies/turret_idw.PNG
Yes, they do take a lot of abuse so make sure they are well-supported/mounted. Our 2006 turret took a lot of abuse and finally snapped at Monty Madness final match. It did not work for a couple matches at IRI also because it had been beaten down so much. The 2004 turret which used a chain was a bit stronger. I’ll see if I can dig up a few pictures and post them.
Wow that’s insanely complicated.
In our design this year we used Ultra-High Molecular Weight Polyethylene (UHMW) Disk sandwiched between two 3X3 aluminium box, with a sproket welded to the box and a bolt going tru all to keep it centered. The UHMW provided a very low amount of friction, making it very easy to turn. I will post a pic later to show it a bit more clearly
For my money if 12" is large enough - order the $28 lazy susan from McMaster Carr. We used them on the last three years machines and they take a lot of abuse before giving out. for $28 you can’t make one any cheaper any better.
I remember years ago checking out some of the stores in Chinatown in NY. One place had this great ball-bearing turntable in the section that sold dishes and restaurant supplies. It was an aluminum bearing housing for a lazy-susan thing meant for a dining table. It was about 2 ft. in diameter and looked to be quite well made. I don’t recall the price, but it was certainly reasonable compared to milling something from plate. maybe $50. That grocery store is still there, on Pell St, 1/2 way between Doyers and Bowery, on the south side of the street. Second floor has all kinds of interesting stuff. Think out of the box.
Personally I’ve never been a fan of lazy suzan’s, usually they tend to become extremely hard to turn when an off centered load is placed on them
1351 made a turret both this year and last year.
Note: I will use “turret” and “turntable” to describe the same thing
The turret on our robot for the 2006 competition was of much use. The ramp in 2006 was slippery and narrow. It was quite dangerous to move around up there because the robot might get stuck or even tip over.
We would get up onto our opponent’s ramp and not even worry about robot positioning because we have a turret to compensate for any misalignment of the chassis. It worked very well and was very useful.
This year, we designed a turret at the base of an arm that was supposed to be comprised of two 5.5 foot articulated sections. I’m not entirely sure what we called it but we modled the turret around how a car wheel is attached to a drive shaft.
In my opinion it was the most useless thing ever. We never got our arm to work to “requirements documents” specifications. The arm turned out much shorter and lighter. Still, it was a very slow device. The chassis could realign itself faster than the turret to move.
Now an example of a good turret would be team 692. They also had a turret but instead of mounting their entire arm on it like we did, they integrated their turning system at the very top of their arm. That way the thing didn’t have to be strong enough to carry the weight of an 11 foot flailing arm. Instead it worked fast and smooth because it wasn’t bearing too much weight.
The moral of the story is: only use a turret if you need to achieve some sort of movement and/or orientation that your chassis can not. Don’t throw one on for the heck of it and unless your team is incredibly beastly, completely ignore the words “cool factor”. Coolness does not outweigh functionality.
Hope this helps,
Sam
Thank you for the great advise.
probably my favorite robot this year
But for turrets I’m interested in Bishop-Wiscarver’s rotary systems, I was impressed by their display at nationals