Odd Ideas of People Who Should Know Better

On Saturday, November 30, 2019 at 1:57:55 AM UTC+1, AMuzi wrote:
On 11/29/2019 6:33 PM, Tom Kunich wrote:
On Thursday, November 28, 2019 at 1:55:56 PM UTC-8, James wrote:
On 29/11/19 7:30 am, wrote:
On Thursday, November 28, 2019 at 8:12:55 PM UTC+1, Tom Kunich wrote:
On Thursday, November 28, 2019 at 10:44:21 AM UTC-8, wrote:
On Thursday, November 28, 2019 at 1:22:06 AM UTC+1, Tom Kunich wrote:
There have been comments here recently of the electronic shift groups.

If you do not have a NEW frameset that is constructed entirely with electronic shifting on mind, the electronic group actually has more drag (less aero) than a standard manual group.

Hanging wires and batteries and the associated mounting paraphernalia for it is quite aerodynamically dirty. The new carbon fiber bikes specifically made for electronic shifting had wires and batteries internal to the frame. Even the battery is inset into the seat tube. The battery remains in place and is charged with a small external connector.

I have seen at least three people here make comments about them using stepping motors. Stepping motors have to hold their position with power so that is simply not true. They use solenoids and ratchets which only require a power surge and then can remain in place powerless.

I was wrong about the stepper motor but they also don't use solenoids and ratchets. It is a simple DC motor. See

https://www.youtube.com/watch?v=hAW5DvLSkak&t=1380s

From 22 min on a guy disassembles a Di2 RD.

Lou

That sort of mechanism cannot be very reliable without quite a bit of current draw.

Looks like a pretty standard solution for positioning to me. Small motor, encoder and large gear ratio (small high rev motor).

That sort of surprises me since I could do a better job than that with my eyes closed.

Of coarse.

I didn't do a lot of minimum power design but enough to see that isn't a good means of accomplishing a job like that.

Power isn't the problem

Though I could probably come up with a better way than solenoids and a ratchet I think that it would be both more accurate than that and use less power.

Practice proofs that accuracy isn't the problem either.

Whenever you are forced to drive against springs you are saying that power isn't limited.

Again power isn't the problem.


Agree. It looked perhaps like the motor had a worm gear on the output
shaft? Also mentioned here
https://en.wikipedia.org/wiki/Electronic_gear-shifting_system#Implementation

Once it has moved to the new location it doesn't require energy to hold
that position.


--
JS


I agree that a worm screw would be a better idea, but remember that this is in a vibration prone device and worm screws will move under those conditions especially if they are working against springs.

I thought of a way to handle it pretty easily though I certainly wouldn't outline it since it is patentable.


Review the original Mavic Mektronic design. Likely expired
patents by now and quite clever. With today's manufacturing
materials and techniques and electronics, could be great.



It would be interesting what choices SRAM and Campagnolo made actuating their electronic shifting devices. From the looks of the RD it seems that Campagnolo chose for a linear actuator.

Lou

On Saturday, November 30, 2019 at 4:10:56 AM UTC-8, wrote:
On Saturday, November 30, 2019 at 1:57:55 AM UTC+1, AMuzi wrote:
On 11/29/2019 6:33 PM, Tom Kunich wrote:
On Thursday, November 28, 2019 at 1:55:56 PM UTC-8, James wrote:
On 29/11/19 7:30 am, wrote:
On Thursday, November 28, 2019 at 8:12:55 PM UTC+1, Tom Kunich wrote:
On Thursday, November 28, 2019 at 10:44:21 AM UTC-8, wrote:
On Thursday, November 28, 2019 at 1:22:06 AM UTC+1, Tom Kunich wrote:
There have been comments here recently of the electronic shift groups.

If you do not have a NEW frameset that is constructed entirely with electronic shifting on mind, the electronic group actually has more drag (less aero) than a standard manual group.

Hanging wires and batteries and the associated mounting paraphernalia for it is quite aerodynamically dirty. The new carbon fiber bikes specifically made for electronic shifting had wires and batteries internal to the frame. Even the battery is inset into the seat tube. The battery remains in place and is charged with a small external connector.

I have seen at least three people here make comments about them using stepping motors. Stepping motors have to hold their position with power so that is simply not true. They use solenoids and ratchets which only require a power surge and then can remain in place powerless.

I was wrong about the stepper motor but they also don't use solenoids and ratchets. It is a simple DC motor. See

https://www.youtube.com/watch?v=hAW5DvLSkak&t=1380s

From 22 min on a guy disassembles a Di2 RD.

Lou

That sort of mechanism cannot be very reliable without quite a bit of current draw.

Looks like a pretty standard solution for positioning to me. Small motor, encoder and large gear ratio (small high rev motor).

That sort of surprises me since I could do a better job than that with my eyes closed.

Of coarse.

I didn't do a lot of minimum power design but enough to see that isn't a good means of accomplishing a job like that.

Power isn't the problem

Though I could probably come up with a better way than solenoids and a ratchet I think that it would be both more accurate than that and use less power.

Practice proofs that accuracy isn't the problem either.

Whenever you are forced to drive against springs you are saying that power isn't limited.

Again power isn't the problem.


Agree. It looked perhaps like the motor had a worm gear on the output
shaft? Also mentioned here
https://en.wikipedia.org/wiki/Electronic_gear-shifting_system#Implementation

Once it has moved to the new location it doesn't require energy to hold
that position.


--
JS


I agree that a worm screw would be a better idea, but remember that this is in a vibration prone device and worm screws will move under those conditions especially if they are working against springs.

I thought of a way to handle it pretty easily though I certainly wouldn't outline it since it is patentable.


Review the original Mavic Mektronic design. Likely expired
patents by now and quite clever. With today's manufacturing
materials and techniques and electronics, could be great.



It would be interesting what choices SRAM and Campagnolo made actuating their electronic shifting devices. From the looks of the RD it seems that Campagnolo chose for a linear actuator.

Lou

I had a hard time trying to figure out how that mechanism could possibly work. You have an optical space counter but what if it moves under load? You can't tell if it moved up or down. There must be a locking device in there that would allow you to step to the right location and then lock the mechanism and depower the motor.