Dual input or Two Gearboxes?

Hello there,

I’m looking for some advice for my team’s one wheel power cell shooter.

Right now the shooter is being directly driven off of two CIM style NEO motors on opposite sides of the hood; however, after reviewing some threads I realized that the setup we have will dramatically decrease the life of our precious motors because the flywheels (I use the term “flywheels” loosely because it is just two 6" traction wheels) were only being supported by the bearings inside the NEO!!

We are now looking at adding bearings in the side of our hood as well as making (a) custom gearbox(es) utilizing the side of the hood as one side of the gearbox.

The question is, is there any benefit to a dual input gearbox on one side of our hood, or two single input gearboxes on both sides of our hood?

Thank you for your time!!

A dual input gearbox will probably weigh less but it’s hard to say for sure. I don’t know if there would be any meaningful difference in efficiency or performance but I assume that there would not be.

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Here is a reference picture of what it is now. Not completely accurate in terms of that is not how our axel exactly looks like but you get the idea.

Hmm, yeah that is what I thought too. I’ll leave this thread open so if anybody else has any more input they can chime in.

something like this? A belt reduction or upduction would be compact and would de-stress your motors


Hmm, I never really looked at belts as being a viable option for driving the shooter motor. We always have worried about belt tension/ slipping.

Very interesting though. Thank you for sharing!

Those traction wheels are almost definitely going to delaminate at high RPM. If you’re going to use them, be careful and have spares.

On topic, most of the shooters I’ve seen people prototyping with NEOs or Falcons or even CIMs have them on a direct drive–a motor on either side of the shooter would get rid of the need for a gearbox (though as you say, you definitely want that additional support either way). I know one team that’s actually gearing Falcons up.

We’re using a 1:1 gearbox on one side for packaging purposes–our shooter hood is all the way to one side of the robot, so we couldn’t have a motor sticking out one side.

We’ve had similar skyway traction wheels on our 2012 bot since 2012 without delam problems. It’s anecdotal evidence, but I’d feel fairly safe if I was them.

Rebound Rumble made for softer shots at much lower RPM–you couldn’t just brick it and have it go in. Maybe they’ll have success with them–but until they’re sure they should definitely be careful, and meantime I’d recommend a backup plan in case of failure. Two local (insofar as anything is local to us) teams had failure of Fairlane wheels two nights ago, which at the speeds they were going (~5000-7000 RPM) were entirely predictable; they deformed and pulled right away from the hubs.

The math on any kind of rubber on a 6" wheel at 5000 or 7000 RPM is…not kind.

Can you just put bearings in the existing setup and otherwise leave it more or less exactly as is? You may need to stand off the motor slightly to allow for this as the motor boss can’t take up the same space as the bearing, but you should be able to make your setup work without this huge redesign.

+1 for that answer. The other option since there is a lot of unused volumes inbetween the wheels and the sideplates is to put a .25" plate on standoffs and put the bearing on that plate. Either ones would be a relatively easy way to remedy the problem

Hm, part of the redesign was to give the ball more velocity by having the option to increase or decrease our rpm by .333. However, seeing these answers and other threads I realize that we probably don’t have an optimal setup for best utilizing the surface area/ rpm speed and for keeping the flywheel from delaminating. I don’t know the maximum speed for the hi-grip 6" wheels, but at 100 percent speed and a 1:1.33 overdrive theoretically, the wheel will be spinning at 7,566 RPM. If we do gear up we will likely not be wanting to max out our motor. At 1:1 we are spinning the wheel at 5676 RPM which sounds a lot safer than the overdrive.

Right now we have 2" of compression with 6" Hi-Grip 80A Wheels and 9" of PVC lining over the 1/4-20 threaded rod. Is there any way you guys can think of to make this design best use the rpm it has to launch the ball effectively? Right now with this setup, we shoot with the apex at 17-18 feet out and 10.5 feet high.

You might want to consider using a flywheel to increase the moment of inertia of your system.

We’re using the same method as shown here.
Also, love the robot design @mrnoble ! Can’t wait to see more of it!

Yeah we have thought about that, I can see about what steel gears we have to just put on there.

Thank you for all your help guys!

We spun multiple 4 inch wheels up to 10k RPM for testing and the andymark HiGrip wheels held up the best. We only spun the 6 inch ones up to 5.5k, as that was just a prototype.

Very interesting, we will try spinning these things at 7.5k rpm (in an enclosed area with nobody in it) to see how it holds up before we put it on the robot.

Just please be careful and keep all students (and adults!) off to the side when you’re doing anything with flywheels.

Will do sir!!

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