Chief Delphi - Dog Shifting Gearbox Feedback

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- - Dog Shifting Gearbox Feedback (http://www.chiefdelphi.com/forums/showthread.php?t=138600)

SerpentEagle

18-10-2015 20:48

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by AdamHeard (Post 1500804)

To elaborate more, there is a strength advantage but not a stiffness advantage. So there are many applications where people might think their plate is too "weak" where changing alloy won't help at all, as what they really want is stiffness.

Wow, I didn't know this. I always thought that 6061-T6 is stiffer than 5052-H32 as it makes logical sense: 5052 bends and 6061 doesnt.

Quote:

Originally Posted by Knufire (Post 1500780)

Yeah, I found plenty of examples of bent 1/8" gearbox plates but we don't have access to a decent brake.

Modulus of elasticity for 6061-T6: 10000 ksi

And for 5052-H32: 10200 ksi

As Adam said, 5052 is actually stiffer than 6061-T6. You would also need a laser cutter to make the plates with 5052 as it cant effectively be machined with a mill.

Joe G.

18-10-2015 20:53

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by SerpentEagle (Post 1500807)

As Adam said, 5052 is actually slightly stiffer than 6061-T6. You would also need a laser cutter to make the plates with 5052 as it cant effectively be machined with a mill.

I wouldn't say "can't." It doesn't machine as nicely as 6061, but it can certaintly be done effectively with care and the correct tools. We regulary perform secondary milling operations on 5052 bent parts with our mill.

Either way, unlightened, unbent plates as thin as .090 are definitely workable for gearboxes.

AdamHeard

18-10-2015 21:13

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by SerpentEagle (Post 1500807)

Wow, I didn't know this. I always thought that 6061-T6 is stiffer than 5052-H32 as it makes logical sense: 5052 bends and 6061 doesnt.

Modulus of elasticity for 6061-T6: 10000 ksi

And for 5052-H32: 10200 ksi

As Adam said, 5052 is actually stiffer than 6061-T6. You would also need a laser cutter to make the plates with 5052 as it cant effectively be machined with a mill.

I was making the point that they are essentially the same stiffness.

SerpentEagle

18-10-2015 21:29

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by Joe G. (Post 1500808)

Either way, unlightened, unbent plates as thin as .090 are definitely workable for gearboxes.

As low as .090? Would bearings stay put with that thin of a material?

Joe G.

18-10-2015 21:33

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by SerpentEagle (Post 1500819)

As low as .090? Would bearings stay put with that thin of a material?

We use positive bearing retention on all of our laser cut gearboxes rather than relying on press fits.

R.C.	18-10-2015 21:48

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by Joe G. (Post 1500822)

We use positive bearing retention on all of our laser cut gearboxes rather than relying on press fits.

Are you saying your relying on the geometry to keep your bearings in? Such as the shoulder of the shaft + the flange of the bearing?

Joe G.

18-10-2015 22:20

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by R.C. (Post 1500824)

Are you saying your relying on the geometry to keep your bearings in? Such as the shoulder of the shaft + the flange of the bearing?

No, should have clarified. Retention is almost always through rivets+washers clamping down on the bearing flange. We'll occasionally do it through other parts of the system, but never something as likely to be seperated from the gearbox during maintenance as a shaft.

electronicsdude

08-11-2015 23:04

Re: Dog Shifting Gearbox Feedback

Quote:

Originally Posted by SerpentEagle (Post 1500644)

With 4 CIMs, according to my spreadsheet, I get around 2 fps less speed on high gear. I know that 6 CIM drivetrains don't have as much improvement as lets say a 2 CIM to 4CIM, but I assume that acceleration and pushing force is a big component to games with defense. Again, according to my calculations, a 4 CIM drivetrain would lose almost 300 inch-lbs of torque on low gear when compared to a 6 CIM with my setup.

On our robot two years ago, a ball shifting setup with two full-size CIM's to a 6 wheel drop center had tons of power, enough to spin four-inch taction wheels. I think the bottleneck is not the amount of motor power or gearbox torque after two CIM's but the traction and number of wheels contacting the ground.

Also think about how much power you consume every match. Its a lot faster to chage a 30% depleted battery than a 50 or 60% depleted battery. If you have the resources to charge enough batteries fast enough than you'd be fine. Just points to consider.

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