3992 Shooter Prototype - Major distance and height!

[josesantos]

"Major distance and height" is an understatement! Are you guys running both motors at full speed or is there some kind of speed control involved?

[CalTran]

Originally Posted by josesantos

"Major distance and height" is an understatement! Are you guys running both motors at full speed or is there some kind of speed control involved?

Looks like it's just battery, main breaker, motors. So I'd say that it's running 5310, followed by 6200. No speed control.

[ksafin]

Originally Posted by CalTran

Looks like it's just battery, main breaker, motors. So I'd say that it's running 5310, followed by 6200. No speed control.

That is correct.

Both motors hooked up to PDB with a breaker between the PDB & battery for on/off toggling.

[Darth Drew]

Wow, your shooter is so similar to ours it's scary, great minds think alike I guess.

[dtengineering]

That's AWESOME.

<Tech Inspector Mode>

Just a few things to consider before finalizing your design... are those tires rated for 4,000 RPM, or whatever it is that you are running them at?

An 8" wheel at 4,000RPM would travel... let's see... 0.2m x 3.14 x 4000 / 60 = 42 m/s? That's 150 km/hr. I don't think many dolly carts are rated for freeway speeds!

And you can calculate the "g" forces acting on the tire pretty easily too...

No doubt you'll be building shrouds for the wheels as part of your design, but do a good job of it. If the frisbee, travelling at one half the edge velocity of your shooter wheel travels 50 feet, how far would a chunk of tire travelling twice as fast.

Or, for that matter how far would a chunk of thumb?

I don't want to take away from the fact that that is one heck of an amazing shooter, and I think it is awesome that you posted the video, and I know you've probably got some safety plans in the works already... but I also want teams to know that if they showed up with that shooter in that configuration that they would very like fail tech inspection.

Jason </tech inspector mode>

[ksafin]

Originally Posted by dtengineering

That's AWESOME.

<Tech Inspector Mode>

Just a few things to consider before finalizing your design... are those tires rated for 4,000 RPM, or whatever it is that you are running them at?

An 8" wheel at 4,000RPM would travel... let's see... 0.2m x 3.14 x 4000 / 60 = 42 m/s? That's 150 km/hr. I don't think many dolly carts are rated for freeway speeds!

And you can calculate the "g" forces acting on the tire pretty easily too...

No doubt you'll be building shrouds for the wheels as part of your design, but do a good job of it. If the frisbee, travelling at one half the edge velocity of your shooter wheel travels 50 feet, how far would a chunk of tire travelling twice as fast.

Or, for that matter how far would a chunk of thumb?

I don't want to take away from the fact that that is one heck of an amazing shooter, and I think it is awesome that you posted the video, and I know you've probably got some safety plans in the works already... but I also want teams to know that if they showed up with that shooter in that configuration that they would very like fail tech inspection.

Jason </tech inspector mode>

Seems like a ton of teams are running these wheels at 1:1 direct drive on CIMs.

They're not designed to run at such an RPM, but some statements from AndyMark say that it should be OK.

We've done some of the same calculations ourselves and are aware of the possibilities.

An upper rail to support the end of the shaft, followed by joining the upper rail with the gearbox is our next step.

[dtengineering]

Originally Posted by ksafin

Seems like a ton of teams are running these wheels at 1:1 direct drive on CIMs.

They're not designed to run at such an RPM, but some statements from AndyMark say that it should be OK.

We've done some of the same calculations ourselves and are aware of the possibilities.

An upper rail to support the end of the shaft, followed by joining the upper rail with the gearbox is our next step.

Agreed! The most obvious evidence that the wheels won't immediately fly apart is the fact that yours haven't! I don't think too many teams will run them faster than that. At least that's the short term observation....

For the record I'll copy the statement from AndyMark's product page for these wheels:

RPM Rating and notes:
These wheels are designed to be propulsion wheels for driving a robot or wheel chair. The design intent is to be contacting the ground, being driven by a gearbox at a maximum speed of approximately 500 rpm (which results in 17 feet/sec).

Within some applications, this wheel has been used as a shooter of objects, spinning at a very high rpm. For these applications, a higher rpm shows that the wheel may wobble, since the valve stem is mounted off to one side of the center of the wheel hub. We have seen properly balanced wheels, using securely mounted hardware (longer screws, washers) that can handle 5,000 rpm. When spinning this wheel at speeds up to 5,000 rpm, please take proper safety precautions.

The emphasis on the last sentence is mine. In previous years FIRST has been very proactive about providing direction on appropriate safety precautions for stored energy systems... and a high speed wheel definitely fits that category... and I expect to see specific guidelines being published at some point regarding safety shrouds.... not just to protect against exploding tires/wheels, but also to keep tender fingers out.

You've got an awesome machine there, and I know you have plans in the works to make it better (and safer) but I want to make it really clear to any novices watching videos like this that experienced teams are demonstrating these as "proof of concept" and know that building safety shields in from the beginning is much easier than adding them when the tech inspector insists upon them. I know I speak on behalf of many tech inspectors when I say, "We want to pass you. Please make it easy for us to do so."

Jason