How does the 2 speed Opti Drive work for shifting?
 

Could someone please explain to me how the shifting works on the Revo?

Shifting from first to second is done solely through the centrifugal clutch. The only thing the Optidrive does is make sure the tranny gears are not moving before it will allow you to switch into reverse. This is done via an optical sensor that reads through a crenellated gear inside the tranny. The Optidrive unit is also said to have some type of failsafe in it, but not sure about that...

I'm just trying to figure out how the E maxx 2 speed kit is going to work. They have the window in the transmission case for the sensor to mount.

Would you call this gear "crenellated"?

http://i160.photobucket.com/albums/t...m/trac3980.jpg

Yup, the little square upright "pegs" are the sensor crenellations. The sensor is a U-shaped device that shines a light from one side of the U to the other. The crenellations breaks the beam and tells the optidrive that there is movement and can even tell how fast (but not sure if the optidrive reads the speed).

I sincerely hope that if the emaxx uses a revo-like tranny design (which they would HAVE to if they want an autoshifting two speed with reverse), that they make the reverse gears far more durable. The setup in the Revo were horribly weak. Coupled with poor strength, any dust or debris that gets on the sensor will fool the optidrive into thinking that the truck is stopped when it isn't. The inside of the tranny is sealed, but all the trannys I've taken apart has some "gear dust" in there over time.

Thank you. Now I think I understand better.

The E maxx tranny doesn't have a separate set of weaker Reverse gears. This is all going to be done with 2 sets of tough looking gears. One set for 1st gear and the other for 2nd.

There is NO one way bearing since this is an Electric setup.

I believe plans are to sense the speed of the output gear through the sensor, then automatically shift to 2nd gear. I just hope they make the shift point adjustable since there are so many gearing options at the pinion/spur gears.

I have a feeling that you are right Sike. It will be nice to have an auto shfting servo actuated tranny! I am sure that the control box that the sensor ties into will have some sort of adjustment "knob".

I see. The tranny will shift like the old emaxx tranny, but the servo will be electronically controlled versus being controlled by the user. I wonder how it will work though? During the time where the dog gear is in between gears (effectively in neutral), the motors will be unloaded and rev really high, and then the dog will slam into second gear. Too bad the servo isn't strong enough to act like a clutch type of engagement - would make for a much smoother transition...

If they do make it shift automatically it would explain why the new e-maxx's only come with a 2 channel transmitter.
When it was first found out on the traxxas forums about the 2 channel tx people thought traxxas was being cheap and you'd have to buy the 3 channel tx that came with the old e-maxx if you wanted to have 2 speed later on. Auto shift sounds better.

Hopefully it will have some sort of soft engage. It's not as important with the stock motors, but when I used my brushless maxx with 2 speed I had to let it coast for a while before shifting to second, and even then it would sometimes make a crunch noise from the drive dog.

Well, Traxxas could used the signal from the sensor to tigger the controller to momentarily interupt the throttle signal to the esc, thus killing the power for a second while the tranny shifts. Kind of like how traction control or manumatic trannys work in full size cars. Not sure if that would cause issues with the esc or motors, but would allow the tranny to shift without full power thru it.

What if the sensor just sets things up to shift to 2nd gear, then you have to blip the throttle to change to 2nd?

That would be cool and easy. :yes:

^^ I like that idea..
phil