Cim-Sim gearbox for shooter questions

[Kevin Sevcik]

This is turning into a stumper. The only advantage the rest of us have over you is that our 6" and 8" wheels have more rotational inertia than your 4" wheel. So your 4" wheel doesn't store as much energy and more of the energy for the shot has to come from your motors.

This might explain everything, though. Your wheel would be losing most of its energy at the beginning when it's just pulling the ball and starting to compress. Then it's running slower through the high compression and you don't have enough compression afterward to make up for it. If you don't have good grip on your wheels, that'd likely make things even worse, wasting what little stored energy you have in friction while the wheels are slipping.

I think you'd probably be best off by increasing the grip on your wheels and trying to increase their rotational inertia. You can do that by increasing the mass or the diameter of the shooter wheel. Or both. Or by attaching a separate flywheel to your shooter axle somewhere it won't interfere with firing the ball.

[Kevin Sevcik]

Also, also, were you getting the same symptoms with the 6" wheels? Why'd you switch away from those? We're running:
- 2x -0673 FPs (~600W)
- CIM-SIM direct drive
- 2x 6" AM performance wheels
- ~1.5" compression

We're getting pretty good distance out of this setup, shooting from the key at about 70% drive on the motors.

[cgmv123]

Originally Posted by Kevin Sevcik

Also, also, were you getting the same symptoms with the 6" wheels? Why'd you switch away from those? We're running:
- 2x -0673 FPs (~600W)
- CIM-SIM direct drive
- 2x 6" AM performance wheels
- ~1.5" compression

We're getting pretty good distance out of this setup, shooting from the key at about 70% drive on the motors.

• 2 9015's
• 2 CIM-Sims through 2 Gates belts with no reduction
• 4X 8" past KOP wheels
• ~1.5" compression
• 60° launch angle

It's working great for us. I think we need 50-60% to shoot from the key. We keep our gearboxes nice and greased. Grease would fly if you added anymore.

[RoboCat2005]

Originally Posted by Kevin Sevcik

Also, also, were you getting the same symptoms with the 6" wheels? Why'd you switch away from those? We're running:
- 2x -0673 FPs (~600W)
- CIM-SIM direct drive
- 2x 6" AM performance wheels
- ~1.5" compression

We're getting pretty good distance out of this setup, shooting from the key at about 70% drive on the motors.

The 6" actually worked a little bit better then the 4", we switched to the 4" on Saturday morning to try it and it we actually took a step back. We had a mentor from the GatorZillas come over and he said we had way to much compression early, as in when the ball first hits, and not enough on exit; this was with the 6" in. So we tried switching to a smaller wheel to try to counter that. We cant just turn the hood around, otherwise we would have done that.

The 6" wheel is the AM white plastic hard wheel, and the 4" is the plastic one that was on the FIRST Choice list.

[Retired Starman]

Our team is using Cim-Sims with the 9015 motors, one on each gear box. But we have a shooter with two pairs of wheels with one gear box for each pair of wheels. The hood drag is too great in your design. The wheels may have sufficient linear velocity, but the the hood is keeping the ball from getting up to speed. In short, there probably is a lit of slippage of the wheels against the ball.

With our design, we have four 5 3/4 in diameter by 3/4 in. aluminum wheels in our shooter. Two disks to a axle. Once we spin up, the balls move through with very little decrease in speed of the wheels. We shoot 32 ft. with an arc 16 ft. high.

I'd look at ways to cut down on the drag in the hood.

Dr. Bob

Chairman's Award is not about building the robot. Every team builds a robot.

[Kevin Sevcik]

Your problem with the 6" wheels may have been too much compression too quickly. Your problem with the 4" wheels is definitely the lack of compression through most of your shooter. I understand that you can't flip the hood around or anything at this point. I think you still have options for increasing your exit compression now that you have 4" wheels. You need to make up a liner for the exit side of your hood. This can probably be a piece of lexan that fits inside the hood, and a few spacers made of wood or something that push the lexan away from the hood and closer to your wheel, increasing your compression. You might also benefit from friction tape on your wheels to make them grippier, and I still recommend a flywheel or heavier wheels so you can store up energy and your wheels can maintain a higher speed as the ball goes through.

[marccenter]

I don't think you will be able to swap your Andy-Mark 9015 motors (am-0912) for the Bane-Bot motors because the output shaft dimensions are different. I have both sitting in front of me and can see that the output shafts are different. The Bane Bot output shaft is significantly shorter in length. Note that the Bane-Bot 550's I have in hand have been recently ordered (new for 2012). YMMV (your mileage may vary).

I am also seconding Kevin's suggestion above for the additional flywheel on your bottom wheels. We added this on Saturday to produce significantly more ball spin. Cavaet - not fully tested.

[Kevin Sevcik]

Originally Posted by marccenter

I don't think you will be able to swap your Andy-Mark 9015 motors (am-0912) for the Bane-Bot motors because the output shaft dimensions are different. I have both sitting in front of me and can see that the output shafts are different. The Bane Bot output shaft is significantly shorter in length. Note that the Bane-Bot 550's I have in hand have been recently ordered (new for 2012). YMMV (your mileage may vary).

I am also seconding Kevin's suggestion above for the additional flywheel on your bottom wheels. We added this on Saturday to produce significantly more ball spin. Cavaet - not fully tested.

How long to the shafts really need to be? Our -0673 shafts were way too long to easily get 100% engagement anyways. I think you could get the Banebots motors to work fairly easily.

[billbo911]

Originally Posted by Kevin Sevcik

How long to the shafts really need to be? Our -0673 shafts were way too long to easily get 100% engagement anyways. I think you could get the Banebots motors to work fairly easily.

We are using 2 BB RS550s, Cim-Sim, 26:17 chain increase driving 2 8 in. wheels. We can easily shoot from the top of the key, and even sink the bottom basket while on the bridge.
The 550s easily have enough shaft to engage the pinions. The key is to mount them with a set screw or Loctite 609 retaining compound (or similar product), or both.

[RoboCat2005]

Originally Posted by billbo911

We are using 2 BB RS550s, Cim-Sim, 26:17 chain increase driving 2 8 in. wheels. We can easily shoot from the top of the key, and even sink the bottom basket while on the bridge.
The 550s easily have enough shaft to engage the pinions. The key is to mount them with a set screw or Loctite 609 retaining compound (or similar product), or both.

Is that 26:17 is that the teeth on each sprocket? and by what you have stated guessing it speeds is up to a decent speed? We had a 32 tooth to a 12 tooth speed increase and the best we could get was during autonomous, place the robot back wheels touching the free throw and could hit the front corner of the fender.

[RRLedford]

We have been using a Banebot Cim-U-lator with the dual 550 motor setup.
We have adjacent dual 8" AM gray urethane wheels on a 5/8" shaft with a 1:1 ratio 30 tooth pulley pair drive. The balls are pinched against a mostly flat 1/4" plywood sheet with its surface covered by high friction shelf liner.
The plywood is slightly bent at entry end to give a funnel shape. We have been able to shoot initially 40+ feet before we started having gearbox and/or motor troubles.

We did install spacers for maintaining airflow between the 550 motors and their gearboxes, using large 3/8" steel washers cut into a 4-lobe spider to match the vent & mount holes there.

We were initially burning up the 550 motors from a having a bad wire terminal connection arcing issue.

After that was fixed, we are still destroying the 550 bearing at the pinion gear end of the 550 shaft (two already). We broke in our gearboxes gradually before loading them, even changing grease after 1 hour.. They were running cool during the break in stage with everything spinning at full speed. Any ideas why motor bearing would self destruct so quickly -- 30 min to 90min of use and less than 100 shots?

We are converting today to the single 775 motor setup of the Cim-U-lator and testing for how much distance/RPM we lose from the fact that 775 is an 18V motor running at 12V. We can regear for more RPM if necessary, but we hope this larger motor can handle whatever the shaft loading issue is that is killing the 550 motor's front bearings. Any ideas why the 550 bearing nearest gearbox would be getting thoroughly chewed up so fast?

Which allowed AM motor(s) used this year with CIM-sim gearboxes are giving good distance for shooters?, and will any AM motors match up properly with the dual motor CIM-U-lator gearbox, as far as motor mounting and shaft diameter (in order to use same pinion gears as fit the 550 shaft)?

-Dick Ledford