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Great stuff.... love Prof. Kelly!


Thanks for posting Jon....
 

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13 moving parts, just as simple as I hoped.
"simplicity is not necessarily easy" - that quote will come in handy.
 

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Dang! He is the man!

"simplicity is not necessarily easy"

Yup. The bombs they dropped on Japan looked simple too, but they required a deep understanding of the workings of our universe, and unleashed the hounds of h3ll.
 

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Yup, and most of those moving parts are bearings.

Only three main moving parts, the rotor and two gears.
And an oil pump. And the utterly bizarre shifter mechanism, which has to be the craziest thing ever. (The gear shift becomes a mechanical motion which is then detected and the reading sent to the motor controller. Why???!!!? I know there is motion to put the car into park, but this goes beyond that.)
 

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And an oil pump. And the utterly bizarre shifter mechanism, which has to be the craziest thing ever. (The gear shift becomes a mechanical motion which is then detected and the reading sent to the motor controller. Why???!!!? I know there is motion to put the car into park, but this goes beyond that.)
The gear shift mechanism just drops a lock onto the gears when P is selected.That didn鈥檛 seem all that complicated to me, although he did comment that the controller was a lot bigger than he expected.
 

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The gear shift mechanism just drops a lock onto the gears when P is selected.That didn鈥檛 seem all that complicated to me, although he did comment that the controller was a lot bigger than he expected.
I suggest you rewatch, starting here, where Prof. Kelly talks about how the mode switch is wired to an 鈥渙uter blue connector鈥 and how all different gear positions have a mechanical position of the mechanism.
 

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Can we find an explanation, with that configuration, for that grinding noise heard when putting the shift lever in park while the car is still in motion. Someone has proposed the noise to be generated by a speaker???
 

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Can we find an explanation, with that configuration, for that grinding noise heard when putting the shift lever in park while the car is still in motion. Someone has proposed the noise to be generated by a speaker???
It's not the transmission. It certainly is not the parking pawl (the teeth are too widely separated and the shaft moving far too slowly for it to make any kind of rapid clicking/grinding noise).

It's my understanding that it's the system that is used to apply the brakes in emergency braking situations 鈥 for that system, being quiet wasn't a design consideration.
 

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I suggest you rewatch, starting here, where Prof. Kelly talks about how the mode switch is wired to an 鈥渙uter blue connector鈥 and how all different gear positions have a mechanical position of the mechanism.
Thanks for the clarification, but I鈥檓 still confused as to why you think this setup is bizarre.

An electronic signal is received and that activates the mechanical gear selector. How else would it work that would be less bizarre?
 

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...the utterly bizarre shifter mechanism, which has to be the craziest thing ever. (The gear shift becomes a mechanical motion which is then detected and the reading sent to the motor controller. Why???!!!?
I expect that this is a standard part that they use in other transmissions as well. They just ignore all of the positions except "park" vs. "not park" because only park (which engages the parking pawl) is relevant in the Bolt. That would be my guess, anyway.

The reason the mechanical input is read back out for the computer is to confirm that the requested "gear change" actually occurred. In the Bolt, for example, the mechanical arm would be activated by a motor, and if the motor stalled or otherwise failed then there would be no way to know unless there was an electronic way to detect if the arm actually moved to where it was supposed to go.
 

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Thanks for the clarification, but I鈥檓 still confused as to why you think this setup is bizarre.

An electronic signal is received and that activates the mechanical gear selector. How else would it work that would be less bizarre?
There is no need whatsoever for anything mechanical to happen besides 鈥淧ark鈥 and 鈥淣ot Park鈥. In the Bolt there are different mechanical positions for drive, low and reverse even though no gearing needs to move because these different modes are entirely handled by the motor controller. No special gear is engaged for reverse, the controller just runs the magnetic field in the opposite direction around the stator.

Moreover, a sensor reads the mechanical position and sends it on to the motor controller.

So, it appears that to select reverse, rather than having the shifter send an electronic signal to the motor controller directly, instead it sends a signal to a motor which moves a linkage which adjusts a mechanism that is read by a sensor that is connected to the motor controller. That's pretty convoluted!
 

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I expect that this is a standard part that they use in other transmissions as well. They just ignore all of the positions except "park" vs. "not park" because only park (which engages the parking pawl) is relevant in the Bolt. That would be my guess, anyway.

The reason the mechanical input is read back out for the computer is to confirm that the requested "gear change" actually occurred. In the Bolt, for example, the mechanical arm would be activated by a motor, and if the motor stalled or otherwise failed then there would be no way to know unless there was an electronic way to detect if the arm actually moved to where it was supposed to go.
It would be vastly cheaper to have a single (self-sensing) solenoid to move the parking pawl. Current automatic transmissions have many such solenoids for moving clutches and gear positions so it's pretty well known how to do this reliably.

My guess is using a standard part meant less safety validation was required.

(I'm still vaguely horrified that switching between drive and low causes something to needlessly clunk away inside the motor.)
 

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There is no need whatsoever for anything mechanical to happen besides 鈥淧ark鈥 and 鈥淣ot Park鈥. In the Bolt there are different mechanical positions for drive, low and reverse even though no gearing needs to move because these different modes are entirely handled by the motor controller. No special gear is engaged for reverse, the controller just runs the magnetic field in the opposite direction around the stator.

Moreover, a sensor reads the mechanical position and sends it on to the motor controller.

So, it appears that to select reverse, rather than having the shifter send an electronic signal to the motor controller directly, instead it sends a signal to a motor which moves a linkage which adjusts a mechanism that is read by a sensor that is connected to the motor controller. That's pretty convoluted!
Thanks, I was wondering what all those separate gear positions were for, since the motor is permanently linked to one gear set. Now that you鈥檝e explained the purpose of this mechanism I agree that it does appear odd, certainly not the simplest setup.

As Sean mentioned, maybe it鈥檚 just a legacy part setup, but with all the expense Chevy went to in designing the motor and drivetrain, it looks like an afterthought.
 

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After watching this video I have a question about D versus L in the Bolt. I understand that the spinning rotor will generate an electric current and that this current is fed back into the battery, but wouldn鈥檛 the amount of current being generated when you lift your foot off the accelerator be the same whether the Bolt is in D or L?

What causes one to dramatically slow the car while the other doesnt鈥檛?
 

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Thanks, I was wondering what all those separate gear positions were for, since the motor is permanently linked to one gear set. Now that you鈥檝e explained the purpose of this mechanism I agree that it does appear odd, certainly not the simplest setup.

As Sean mentioned, maybe it鈥檚 just a legacy part setup, but with all the expense Chevy went to in designing the motor and drivetrain, it looks like an afterthought.
Might be that the shift actuator is used across the GM product line so they buy or make these by the millions. So it's proven and cheap, even though it's overkill for the Bolt.
 
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