1/2" Hex Shaft Bevel Gears

[dmorewood]

I'm working on a go cart with a swerve drive in the offseason with a couple of friends. We aim to have this driving at 20 MPH by FIRST competition season. Unfortunately we can't find 1/2 Inch Hex Shaft Bevel Gears anywhere. If anyone knows of a good place to find these it would be a huge help.

[Joe G.]

Hex Shafting is relatively unique to FRC. You're much more likely to find keyed bevel gears in this size. Or, you can broach your own. Getting a good arbor press and broach is a great investment for an FRC team.

[Chris Endres]

Over the summer, I did an extensive search for bevel/miter gears with .5" hex bore, couldn't find anything. It's not an industry standard, so they really aren't in demand.

You can find bevel and miter gears at SDP-SI: http://www.sdp-si.com/eStore/CoverPg/Gears.htm

You can also get bevel/miter gears from McMaster: http://www.mcmaster.com/#bevel-gears/=z2kqn1

Vex pro has 15t miter gears with a 3/8 hex bore: http://www.vexrobotics.com/vexpro/mo.../217-3344.html

But as Joe said, you'd either need to used the keyed bore, or broach your own.

[asid61]

You will probably need to broach your own. The only hex bore miter gear I know of is the Vex one. I would go with their 3/8" hex bore gears and have a reduction to the wheels to reduce the load on them.
SDP-SI sells 1/2" bore bevel gears, all you'd need to do is buy a hex broach and broach them. They also sell 12mm bore bevel gears (as does QTCgear), which you can bore out to 1/2" on a lathe relatively easily.
How much are you planning to spend on this? Swerve drives, even simple ones, are quite expensive.

[dmorewood]

I'm prepared to spend 500-800 dollars on the swerve modules. I found a 1/2 Inch Hex Broach on McMaster. Any suggestions for a good bevel gear to broach?

[Peyton Yeung]

I had good results with these from boston gear.

[Joey Milia]

Originally Posted by Peyton Yeung

I had good results with these from boston gear.

I would recommend going with gears from Martin Sprocket and Gear over those from Boston Gear. The Martin gears are case hardened and will wear better with heavy use. You can find their catalog here http://www.martinsprocket.com/docs/d....pdf?sfvrsn=14 and look up the part numbers at any number of suppliers to find the gears to buy.

[TheHolyHades1]

Originally Posted by dmorewood

I'm prepared to spend 500-800 dollars on the swerve modules. I found a 1/2 Inch Hex Broach on McMaster. Any suggestions for a good bevel gear to broach?

You might want to see if it's possible to increase your budget. I've BOM'd a few swerve designs of mine, as well as looked at a few from teams like 1640 (who provide excellent resources in their swerve central), and I wasn't able to make the cost go under about $200 for each module. You'll also want to take into account manufacturing expenses, which can either be nearly free (tooling) or very expensive depending on how much outsourcing you're doing, and how much that'll cost you. Also, don't forget to budget for an extra module or two as things are likely to break ...

[Dale]

I would recommend going with gears from Martin Sprocket and Gear over those from Boston Gear. The Martin gears are case hardened and will wear better with heavy use. You can find their catalog here http://www.martinsprocket.com/docs/d....pdf?sfvrsn=14 and look up the part numbers at any number of suppliers to find the gears to buy.

I'd worry that case hardened gears would be hard to broach, however. Some teams have used non-hardened gears and then hardened them themselves afterwards.

[JesseK]

Originally Posted by TheHolyHades1

You might want to see if it's possible to increase your budget. I've BOM'd a few swerve designs of mine, as well as looked at a few from teams like 1640 (who provide excellent resources in their swerve central), and I wasn't able to make the cost go under about $200 for each module. You'll also want to take into account manufacturing expenses, which can either be nearly free (tooling) or very expensive depending on how much outsourcing you're doing, and how much that'll cost you. Also, don't forget to budget for an extra module or two as things are likely to break ...

Assuming there are 4 modules!

This is a go-kart which presumably won't get into a pushing match. Seems perfect for a 3-pod design, and eliminates the need for a perfect frame/suspension setup.

[Chak]

You can try using a 1/2'' hex broach instead. It's not a bad investment, the broach will end up being useful later anyways.

Originally Posted by dmorewood

We aim to have this driving at 20 MPH by FIRST competition season.

Wow, that's pretty fast for FRC. You're not using CIMs, are you?

[Nathan Streeter]

Originally Posted by dmorewood

...We aim to have this driving at 20 MPH by FIRST competition season....

I'd like to be the second person to say just how absurdly fast that is for an FRC robot. To be clear you're not converting incorrectly, 20 mph is 29 fps. I'm not aware of anyone that's tried gearing for 29 fps, but I doubt anyone has successfully. It'd take most FRC robots (assuming ~120lbs) far too long to accelerate to be practical. As I recall our team's 'Speed Racer' in 2008 was geared for a free speed of 19fps, which was hard enough to drive... and was on a robot that generally turned rather than stopped... and the robot weighed around 50 pounds with battery (so it could accelerate very quickly).

I suspect something geared for a free speed of more like 14-20 fps would be much more well-suited for a game with demands for a high top speed.

[EricH]

Originally Posted by Nathan Streeter

I'd like to be the second person to say just how absurdly fast that is for an FRC robot.

You're assuming this is for an FRC robot.

Unfortunately for that assumption, it's for a go-kart.