3 speed transmissions

[R.C.]

Does anyone know where to buy a 3 speed transmission or specific instructions on how to build one

[vivek16]

I believe dewalt trannies are 3 speed. I am not positive on this though.

Andymark does not sell 3 speed ones.

If you don't mind me asking, why do you need 3 speeds? Most teams find 2 sufficient.

thanks, Vivek

[Joe G.]

Dewalt transmissions are the main 3 speed transmissions commercially available practical for FIRST. They can be purchased directly from Dewalt, and then must be modified, according to the instructions in Dr. Joe's Whitepaper "Nothing but Dewalts" to accept a CIM motor.

Also, if you're going to custom fabricate a tranny, it's much simpler and lighter to do 4 speeds rather than 3... Unless you go servo, which is not the most reliable (in my experience) for a 3 speed.

[R.C.]

How do you make a four speed?

[Valley Raider]

Do you use CAD models?

I don't have any of my models with me but I could post one them so you can take a look. I have a 2 and a 4 speed, we build the two speed one. Its going to be hard to just describe it how to make one if you've never seen one up close. I'll put something together and put up a post. I've been meaning to have the design critiqued by the CD crew.

I would recommend searching for post on this topic, there are thousands.

[EricH]

Originally Posted by rc_cola1323

How do you make a four speed?

Build a two-speed, then add another shifter section. (OK, not quite that easy, but that's the basic idea.)

[A_Reed]

You would have your first two reductions coming in off of your main input or lay shaft going to your primary shifter shaft and then a 1:1 reduction and another reduction off of your primary shifter shaft to a secondary one.

This gear selection would give you four speeds.
Shaft 1 gear a + Shaft two 1:1 = Reduction a(1)
Shaft 1 gear b + Shaft two 1:1 = Reduction b(2)
Shaft 1 gear a + Shaft two Gear c = Reduction a * Reduction c = Reduction x(3)
Shaft 1 gear b + Shaft two Gear c = Reduction b * Reduction c = Reduction y(4)

I have these pictures for a bit of a visualization. this is something I designed a while back with the use of the gearset of an AM Gen 2 for the first stage, the shaft would be custom. It could also be done without the 1:1 but I chose to keep the original Gen2 reduction and only use a third gear to go further.

[neoshaakti]

Im pretty new to the concept of two or three speed transmissions (our team just stuck to the KOP toughboxes)
What exact do those pneumatic pistons do?

this is kinda stretch, but does anyone have a two or three speed transmission in action on video or something

thanks

[sdcantrell56]

I would really recommend either using an andymark 2 speed or using the dewalt if you do not have a machine shop willing to do the work for you. The precision required to make a transmission is very very important.

[EricH]

Originally Posted by neoshaakti

Im pretty new to the concept of two or three speed transmissions (our team just stuck to the KOP toughboxes)
What exact do those pneumatic pistons do?

this is kinda stretch, but does anyone have a two or three speed transmission in action on video or something

thanks

The pistons shift gears. Servos can also be used, if you are careful.

I'm sure there are some, but you'd get the whole robot. (330 2007-2008, for example. No gearbox-only shots, but there are times you can tell they shift gears.)

[Pat Roche]

Originally Posted by neoshaakti

Im pretty new to the concept of two or three speed transmissions (our team just stuck to the KOP toughboxes)
What exact do those pneumatic pistons do?

The pneumatic piston is used to shift the dog between gear sets. The gears that the dog engages are on bearings so they can spin independent of the driven shaft. The pneumatic pushes the dog against the gears locking them against the gear to power it. The dog is basically a rotating disc that engages into the gear via pins or other couplers. In the pictures posted above there is an internal shaft that the pneumatic pushes that is pinned to the dog.

Also if you are looking to make your own three speed transmission I would suggest looking up team 222 Tigertrons. They have a really sweet three speed transmission that they've used in the past (I haven't seen them this year so I'm not sure if they used it again or not).

[camtunkpa]

Originally Posted by Pat Roche

Also if you are looking to make your own three speed transmission I would suggest looking up team 222 Tigertrons. They have a really sweet three speed transmission that they've used in the past (I haven't seen them this year so I'm not sure if they used it again or not).

We haven't used the three speed since 2004, but we have used our TigerDrive 2 speed version since 2006. The TigerDrive is still a ball lock transmission but it is much more compact and light than in 2004. The main reason we switched to a two speed is because we really hadn't seen the need for three speeds in recent games. One nice thing about the ball lock is you can keep stacking gears together until you run out. We had talked about making another three speed based off of our current TigerDrive that would weigh no more than 4 lbs, but this year's game really didn't need it. I guess the best advice I could give is the best spent time is going to be determining whether or not the game and your team strategy requires 3 speeds.

More information on our three speed can be found here: http://www.chiefdelphi.com/media/papers/1539

[Daniel_LaFleur]

Originally Posted by rc_cola1323

Does anyone know where to buy a 3 speed transmission or specific instructions on how to build one

Here is the instructions on making a 3 speed robot legal transmission from the DeWalt transmissions and mounting it to the CIM motors and the robot.

The BoM and where to buy are in that white paper although I'd suggest experimenting with different ways of shifting other than the servos.