Need help from turret experts

[Dick Linn]

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.

[Cowmankoza]

Originally Posted by UCGL_Guy

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.

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

[Sam N.]

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

[Alpha 997]

Originally Posted by Sam N.

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.

[Scott Morgan]

Originally Posted by pstrapp

I would suggest checking out 75's Turret

http://www.roboraiders.com/showcase/...turret_idw.PNG

http://www.roboraiders.com/showcase/?page=assy&type=sub

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

[pklevann]

Here are some pictures from our 2001 robot. We made a sandwich of three aluminum plates, the base, the rotation ring, top plate or gear plate. The base had a 1/4" groove milled in at a specific diameter (20+ inches, it was 6 years ago). The rotation ring had a groove machined in the bottom at the same diameter as the base and a groove in the top machined at a slightly smaller diameter if I remember correctly. The top plate had a groove machined at the same diameter as the top groove in the rotation ring. The grooves were only 0.060" or 0.090" deep. We filled these grooves with 1/4" ball bearings. The rotation plate had the old window motor attached to it. I had measured the gear on the window motor and then in cad created an internal spur gear that was the size we wanted. We slapped the plate on the cnc and let it cut the teeth for the top plate. To check our position we created a lexan gear that attached to a pot located on the rotation plate. The whole system was very smooth, stable, easy to control. On last years robot (2006) we made a similar turret with a few modifications and improvements. I can't find any pictures of that one yet, but if I do I will post them. Last year we had the pleasure of watching our robot tip over going up the ramp and having the "Head" break off, sending ball bearing flying all over the field. Zip ties make horrible bearings, but they do keep you in the game.

[Alpha 997]

Thank you the posts. These are great help.

[Herodotus]

I don't seem to have any good pics but this year we used the front piece off of a scooter as our turret base, and then just attached a gear to it to turn it. Works well for something like an arm but if you are having a wider load such as a ball launching turret from last year I think something along the lines of a lazy suzy would work better. Last year we made our own custom sprocket so the balls could go through the center.