Prototype Small Wheeled Shooter

[Ether]

Originally Posted by Kevin Sevcik

Better question is whether there's anything to be gained adding a third wheel to the setup so you can make a smother transition up to the final wheel speed. Something like starting with the BB550 in a 10:1 then BB550 in a 5:1, then the 1:1 BAG. I'm pretty sure the higher initial velocity your final wheel sees, the farther you'll shoot and faster you'll recover.

1:1 BAG at free speed* is 14,000 rpm. With 2 7/8 dia wheel that's 120 mph tangential speed. With no slippage that's 60 mph.

If the frisbee is not exiting that second wheel at 60 mph it might be because it is slipping.

So, either:

1) crank down the speed of that second wheel a bit to stop the slipping and get a higher exit speed, or

2) crank up the speed of the first wheel, which is presently only 1930 rpm, which translates to 16 mph tangential velocity or 8 mph exit speed. A higher exit speed from the first wheel means a higher entry speed into the second wheel, which may reduce the slipping in the second wheel and give a higher exit speed

* I realize that due to windage and vibration it will be less than that

[AllenGregoryIV]

Originally Posted by Ether

1:1 BAG at free speed* is 14,000 rpm. With 2 7/8 dia wheel that's 120 mph tangential speed. With no slippage that's 60 mph.

If the frisbee is not exiting that second wheel at 60 mph it might be because it is slipping.

So, either:

1) crank down the speed of that second wheel a bit to stop the slipping and get a higher exit speed, or

2) crank up the speed of the first wheel, which is presently only 1930 rpm, which translates to 16 mph tangential velocity or 8 mph exit speed. A higher exit speed from the first wheel means a higher entry speed into the second wheel, which may reduce the slipping in the second wheel and give a higher exit speed

* I realize that due to windage and vibration it will be less than that

Tonight's test has two BAG motors 3:1 and 1:1 (instead of a 550 and a BAG motor) and we're getting 30-35 feet from 2 feet off the ground and 0 degrees of incline. We also moved the blue wheels on the front and it seems slightly better. We're hoping that the harder wheels won't be eaten as fast as the green soft wheels.

[Ether]

Originally Posted by AllenGregoryIV

Tonight's test has two BAG motors 3:1 and 1:1 (instead of a 550 and a BAG motor) and we're getting 30-35 feet from 2 feet off the ground and 0 degrees of incline.

Nice. Can you gear that 2nd BAG speed down from 1:1 to 1.2:1 and try again ?

[Aren_Hill]

Originally Posted by Ether

Nice. Can you gear that 2nd BAG speed down from 1:1 to 1.2:1 and try again ?

Not easily using the VersaPlanetary they have, only 3:1, 4:1, 5:1 and 10:1 single ratios.

[AllenGregoryIV]

Originally Posted by Ether

Nice. Can you gear that 2nd BAG speed down from 1:1 to 1.2:1 and try again ?

Ether, what exactly are you trying to get us to test? We were able to pull back about 80-75% on the joystick before we noticed any distance change. We still know the front wheel is slipping. We're pretty happy with the setup as it is, since we can meet all of our design goals and more. We won't be doing too many more changes to the shooter configuration. Once we get some other systems improved, we will be adding light sensors and white lines to the wheels so we can do bang-bang speed control and more precisely control our distance.

[Robo Hamsters]

Originally Posted by AllenGregoryIV

We just posted a blog entry about our current prototype shooter.

Just wondering how you set the one gearbox to be a 1:1 ratio?

Also, anyone have any ideas as to how you mount the banebots wheels directly to a CIM?

Thanks

[Botwoon]

Originally Posted by Robo Hamsters

Just wondering how you set the one gearbox to be a 1:1 ratio?

Also, anyone have any ideas as to how you mount the banebots wheels directly to a CIM?

Thanks

On their blog they explained that they used a Versaplanetary box with all of the gears within removed. The output shaft of the VP boxes are the same hex as the banebots wheels.

[Robo Hamsters]

Thanks, didn't see that there.

Also we were wondering how you direct drive the banebots wheels with a CIM.

[Tom Line]

Originally Posted by Robo Hamsters

Thanks, didn't see that there.

Also we were wondering how you direct drive the banebots wheels with a CIM.

The reason they are using the versa may be because the output shaft on a versa is actually a .5 hex, which is an ID that banebots sells their wheels with.

Locking a stage in a planetary gear is fairly simple - look up how people did it with globe motors. It involves glueing the sun gear and planetaries together with something, then dremeling off the teeth of the planetaries so they don't touch the ring gear.

FYI, you can't really be guaranteed that you can direct drive a banebots with a cim without installing an insert and broaching it with a keyway. The unfinished bores on the banebots wheels are not actually a measured diameter: it varies. They ream it to .375, but in most cases it comes bigger than the 8mm shaft of a cim from their manufacturer, and hence will not work directly on a cim.

[IndySam]

Originally Posted by Robo Hamsters

Thanks, didn't see that there.

Also we were wondering how you direct drive the banebots wheels with a CIM.

8mm 500 Hex Adapter Shaft (am-0588)

[Tom Line]

Originally Posted by IndySam

8mm 500 Hex Adapter Shaft (am-0588)

Wow. I'd never noticed that before.

[falconmaster]

Originally Posted by AllenGregoryIV

We just posted a blog entry about our current prototype shooter. It uses much smaller diameter wheels than many teams that we have seen post of CD. We're hoping this idea might inspire some teams that are struggling to package their large shooters.

Blog Entry with full specs on the shooter configuration.

Youtube Video

Will all three wheels fit on the versaPlanetary Gear Box output shaft?

[AllenGregoryIV]

Originally Posted by falconmaster

Will all three wheels fit on the versaPlanetary Gear Box output shaft?

The three 0.4" wheels fit perfectly. The two .8" wheels have about .5" sticking over the top of the shaft, we just put a longer 1/4-20 bolt on with a washer, seems to work well enough.

[EricLeifermann]

Originally Posted by AllenGregoryIV

The three 0.4" wheels fit perfectly. The two .8" wheels have about .5" sticking over the top of the shaft, we just put a longer 1/4-20 bolt on with a washer, seems to work well enough.

Why did you go with 2 different wheel thickness? Just what you had around?

[AllenGregoryIV]

Originally Posted by EricLeifermann

Why did you go with 2 different wheel thickness? Just what you had around?

The .4" orange wheels can be bought using the BB PDV. We purchased 2 .8" of all three colors after we tested how grippy they were to the discs. We just left the .4" ones on there for now. We'll best testing a bunch of different wheel combinations over the next week.