Prototype Small Wheeled Shooter

[AllenGregoryIV]

Originally Posted by dodar

You sir, have just lightened up alot of robots.

We hope so.

Originally Posted by Ether

Try slowing that second motor down (the BAG motor) . Try running it at ~10 volts.

See what happens. Easy enough to do.

Thanks for the recommendation; we still have a lot of work to do to optimize the whole setup. With the versplanetaries we can swap around motors and gear combinations so quickly that we plan to test a large number of them. We're also going to try to standardize on voltage as well, but that will take a bit more programming (since we don't have any type of speed feedback we can't do Bang Bang yet). We'll take your advice and test it. We agree that the last wheel is spinning too fast and is most likely slipping.

Originally Posted by ParkerF

Allen,

This is great work! I admire your lack of hesitation to give away this information. Shows you and your team's true colors.

Thanks and good luck at making it even better!

-Parker

P.S. - Have you tried shooting from the floor? What kind of angle do you expect to have to pitch the shooter to for the 3pter?

Thanks for the compliments. That really depends on how high we end up shooting from and our distance away from the goal. I'm not sure we could give a number. That height was less than 5 feet so in theory we could just shoot from there.

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

We took the ring gear, sun, and planets out of a 10:1 versaplanetary. I'm not sure if you can do the same with the other gearboxes. Paul Copioli can probably expand on that. If I remember I'll post pictures in tonight's blog update. We'll probably have to swap around a few of the gear ratios during testing anyway.

Originally Posted by Robo Hamsters

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

My thought would be to get an AM 8mm Hub and drill out the Banebots wheels for that and bolt them to it. I think it would work better than the 8mm to 1/2 hex adapter (It's not very long).

Originally Posted by Tom Line

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.

It's much easier than that. The spline on the output shaft is the same as the one on the sun gear. You just remove the whole 10:1 stage and bolt the front and back of the gearbox together.

[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.

[JB987]

Originally Posted by AllenGregoryIV

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.

Great work guys. Can you tell us the distance away from the goal you were shooting into in the video?

[Tom Line]

Originally Posted by IndySam

8mm 500 Hex Adapter Shaft (am-0588)

Wow. I'd never noticed that before.

[AllenGregoryIV]

Originally Posted by JB987

Great work guys. Can you tell us the distance away from the goal you were shooting into in the video?

The front of the board was at about 15 ft.

[Ether]

Originally Posted by AllenGregoryIV

We're also going to try to standardize on voltage as well...

If you want to do speed control, your voltage at the desired shooting speed has to be a bit less than the lowest voltage you expect to see from your battery while you're shooting -- in order to allow headroom for you control algorithm to work.

[Shu]

Did you or are you going to try the larger diameter (3.875" or 4.875") Banebot wheels?

[AllenGregoryIV]

Originally Posted by Shu

Did you or are you going to try the larger diameter (3.875" or 4.875") Banebot wheels?

We didn't and we aren't planning too. We don't have any, and we like the small form factor. We did have a 4in RC Buggy wheel you can see in previous prototype videos on the blog that worked very well but it was too big for us.

[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.

[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 ?