Designing a "belt + roller" conveyor for balls

[Greg Needel]

so here is another question, what diameter rollers do you all like to use? I know that there are minimum diameters for the different thicknesses of polycord, but I have never fell upon a standard roller diameter that seemed to work better than others.

[Knufire]

Originally Posted by Greg Needel

so here is another question, what diameter rollers do you all like to use? I know that there are minimum diameters for the different thicknesses of polycord, but I have never fell upon a standard roller diameter that seemed to work better than others.

469 tends to go 2"; most of their rollers are 2" x 0.035" 6061 tube. 2012-2014 were all like this.

[Everett33]

Originally Posted by Knufire

469 tends to go 2"; most of their rollers are 2" x 0.035" 6061 tube. 2012-2014 were all like this.

What do you use to transfer the power from a gearbox to the 2" tube?

[GeeTwo]

Originally Posted by Greg Needel

so here is another question, what diameter rollers do you all like to use? I know that there are minimum diameters for the different thicknesses of polycord, but I have never fell upon a standard roller diameter that seemed to work better than others.

We did something pretty small (about 1") for our 2012 robot. This was our rookie year, limited budget, and we spent most of it on registration and shifters. The diameter was selected so that we got the right speed for one of the motor/gearbox combinations we had (I believe it was a window motor).

[Lil' Lavery]

Originally Posted by Greg Needel

so here is another question, what diameter rollers do you all like to use? I know that there are minimum diameters for the different thicknesses of polycord, but I have never fell upon a standard roller diameter that seemed to work better than others.

IIRC, slightly more than 1.9" (OD of Sc40 1.5" PVC).

Going into further detail, we then wrap the 1.5" PVC with shelf liner. We create our spacers/grooves by using rings of 2" PVC over that assembly.

We used this approach in 2009, 2012 and 2013, and were largely happy with it. We still get some amount of wandering polycord, but it's not really a big deal.

[Chris Endres]

The 254 conveyor slideshow goes over a lot of what you're looking for. McMaster sells polycord (we usually use the 3/16" OD): http://www.mcmaster.com/#round-belts/=zsnxr5

We love polycord, especially for rollers, you can cut and weld it together in a few minutes, and it's super easy to replace. It is also good to use polycord in applications where come slipping is need or expected, mainly so you don't strip a timing belt.

Most rollers we use are polycarbonate tubing with a machined or 3D printed hub that is inserted into a bearing which then fits a into a plate. The hub is then riveted onto the tube.

For pulleys, we usually use custom machined "rope" pulleys with a hex or round keyway bore. We last used poly cord on our 2014 robot roller.

[Tom Line]

*glances around*

I'll let you in on a little secret I figured out this past year.

Get a polycarbonate roller from mcmaster with 1.125 ID. Put a bearing on one end, and put a versa hub on the other. You see, many common FRC bearings are 1.125 OD, and the versa hub's "hub" is 1.125. Super glue them in and you're done. You can either direct drive the versa hub (if you pick a 1/2 bore hub), leave it to run on the plastic with a 3/8 shaft, or bolt a 25 sprocket to the hub if you want to chain drive it.

That's it. Zero work rollers.

http://www.mcmaster.com/#8585k63/=zsp0kc
http://www.andymark.com/product-p/am-0209.htm
http://content.vexrobotics.com/vexpr...g-20141010.PDF

Not very expensive either, and clear so you can put all sorts of gimmicks inside them

[Gdeaver]

One off the constant recurring problem with intakes and conveyor belt lifts is jamming and the resulting fried motor. Especially with the RS series. In 2014 we added a ball clutch to our ball intake system. If we had not developed this we would have had bins of fried motors. We used and AM 9015 with a banesbot planetary. Took a solid .5" shaft collar. Drilled six holes radially in the shaft collar and broached it for the BB shaft. The holes were drilled so that a .1875 ball bearing would sit just below the midpoint. A Martin #35 sprocket that is about .375 thick was then drilled with holes matching the shaft collar. These holes were drilled so that the ball bearings would sit above the midpoint. The 2 are put together on the BB shaft followed by a series of spring bevel washers. The number and pre-loading of the washers determine the clutch release point. The whole thing was done by hand on a drill press and worked amazingly well. We had investigated magnetic and friction clutches. The ball clutch performed better. So my advise is that adding a clutch to a intake or convoy is a really good idea. May be able to dig up some photos if any one is interested.

[Lil' Lavery]

I'm a little puzzled at the need for a specially designed clutch in an intake system (especially a belted one). It seems a lot simply to design your system to slip before it stalls your motor, especially if you're using a fan-cooled motor (such as the RS series). Almost every polycord-based conveyor will do pretty much automatically.

In other words, have your intake roller/conveyor act as your clutch.

[Gdeaver]

I was more referring to the ball intakes that were common in 2014. These usually were belt or chain driven. Yes, poly cord will slip but if it happens frequently it stretches and wears. We had similar problems to a lesser degree in 2010 with the soccer balls.

[Michael Hill]

This is what I love about FRC. Before this thread, I had never heard of crowned pulleys. #SuchLearning

[Gregor]

Originally Posted by Tom Line

*glances around*

I'll let you in on a little secret I figured out this past year.

Get a polycarbonate roller from mcmaster with 1.125 ID. Put a bearing on one end, and put a versa hub on the other. You see, many common FRC bearings are 1.125 OD, and the versa hub's "hub" is 1.125. Super glue them in and you're done. You can either direct drive the versa hub (if you pick a 1/2 bore hub), leave it to run on the plastic with a 3/8 shaft, or bolt a 25 sprocket to the hub if you want to chain drive it.

That's it. Zero work rollers.

http://www.mcmaster.com/#8585k63/=zsp0kc
http://www.andymark.com/product-p/am-0209.htm
http://content.vexrobotics.com/vexpr...g-20141010.PDF

Not very expensive either, and clear so you can put all sorts of gimmicks inside them

This is fantastic. Nice find.

[GeeTwo]

This is right on the edge of the topic, but I've decided it's worth posting on this topic, because it is a "belt + roller conveyor for balls". For our latest off season project, we've broken our team into three project teams to add some systems to our 2015 robot. Our final 2015 robot had a 4-wheel omni tank drive, and a 6'4" tall lift (including signal light height) on the "front". For this exercise, we gave the students autonomy, with the mentors available as "knowledge resources"; we'll base our build season balance of mentor vs student design decisions on the results of this challenge.

The floor of the classroom shall have a great many tennis balls (courtesy of our head coach from his house, so I personally expect a wide variety of "dead" balls with a fair number of "live" balls).

• Team 1 has to pick up tennis balls in the "right half space" outside of the original robot's frame perimeter and pass it to team 2.
• Team 2 has to accept balls from team 1, pass them behind the lift, and deliver them to team 3.
• Team 3 has to accept balls from team 2, and place them into a standard FRC tote in the "left half space" of the 2015 robot.

The tote begins and must end in a fairly small taped box. (If the team decides to carry it around, that's cool, but there are zero points if the tote does not end up back within the taped box.)

I've been working with all three sub-teams on their mechanisms, but it's team 2 I'm going to address here. It was pretty obvious that "passing the ball around the back" was a much simpler task than the other two, so the teams figured out that team 1 would hand off to team 2 fairly low, and team 2 would hand off to team 3 fairly high. "Passing around the back" is currently planned through a length of 3" diameter aluminum dryer hose, driven by gravity. This means that it is up to team #2 to additionally lift the tennis balls up from where they receive them from team 1 to somewhere quite a few inches above where they will deliver them to team 3. So far, I'm digging the teamwork - team 2 accepted additional tasking because they had been potentially under-tasked by the constraints.

So the question is, how do you lift a tennis ball by four or five feet? I would have probably pursued a polycord-and-plexiglas solution similar to our first year's basketball lift, but given the lack of another robot beating them up, team 2 decided to use a velcro loop. We are using a couple of 3" PVC drain covers glued together and covered in "Cro" (the hooks of velcro) to drive a 3" wide "belt" constructed of dual-sided velcro with the "Vel" (loops) inside and "Cro" outside. The opposite pulley may simply be a fixed axle that "loops" rub around, or may be another spool turned by the velcro loop.

*** - for anyone who does not already know, VelCro is brand name constructed as a contraction of two French words (both of which have English cognates). I do not speak French, but I've grown up in Southeast Louisiana, where French is ubiquitous in place names, food, and other random things, only a bit ahead of Spanish and German. When I went to France a couple of decades ago, I was able to puzzle out most of the road signs. Anyway, Vel is the first syllable of Velour, which means loops, and in English means a rather soft fabric which has a bunch of loops sticking up from a substrate layer, similar to but much softer than carpet. Cro is the first syllable of "crochet", which means hooks. There is a style of yarn work called crochet which uses hooks to pull yarn into intricate shapes. My mother was a serious practitioner of crochet in the late 70's and early '80s, and I did a bit of practice in it.

[Tom Line]

Originally Posted by Gregor

This is fantastic. Nice find.

Thanks. Kudos to the team who integrates a cheap slip ring and puts LED's in one.....

[Jared Russell]

Originally Posted by Tom Line

*glances around*

I'll let you in on a little secret I figured out this past year.

Get a polycarbonate roller from mcmaster with 1.125 ID. Put a bearing on one end, and put a versa hub on the other. You see, many common FRC bearings are 1.125 OD, and the versa hub's "hub" is 1.125. Super glue them in and you're done. You can either direct drive the versa hub (if you pick a 1/2 bore hub), leave it to run on the plastic with a 3/8 shaft, or bolt a 25 sprocket to the hub if you want to chain drive it.

That's it. Zero work rollers.

http://www.mcmaster.com/#8585k63/=zsp0kc
http://www.andymark.com/product-p/am-0209.htm
http://content.vexrobotics.com/vexpr...g-20141010.PDF

Not very expensive either, and clear so you can put all sorts of gimmicks inside them

When 341 made extensive use of polyurethane flat belting in 2012 (and 2013), we used exclusively 1.25" OD, 1.12" ID aluminum round tubing from Online Metals for our rollers. 10 seconds on the lathe (or a minute with a deburring tool) and it is a great fit for a hub or 1.125" OD bearing.