Just about to get one of these motors and will do this. It takes me back my days working in Aerospace-wirelocked anything that moved, and if its good enough for things we fly in with our Famlies, that's good enough for me. Plus, I like the look of it, and it adds a bit of Pro looking fettling to the ride.I come back to the topic
TECH NERD ALERT: very long and boring post ?
So, the lockring is threaded ccw. We must take into consideration that these components are designed in such a way that their own inertia acts in favor of tightening.
Let me explain and try to analyze the phenomenon.
Working with such a component, the designer determines the direction of the thread on the basis of the direction of the main stress, which will generate a reaction of the component itself (given by its own inertia) in the opposite direction.
In a system with a spider and its lockring, if the system itself forces the component to turn clockwise, its own inertia will generate an opposite, counterclockwise reaction.
The spider (of course) turns clockwise when pedaling.
I can assume (and I want to clarify it, mine are assumptions as a "nerd" designer) that the Bosch designers have taken into account the accelerations impressed by the rider (raises, starts, etc ...) to the chainring via the pedals, action reinforced by the motor also. Then we have the motor shaft that lets the spider move in a CLOCKWISE direction, dragging the lockring with it, making it snap in the same direction; the lockring is therefore forced to sudden start rotating clockwise. Its inertial reaction will generate an anti-clockwise force (i.e. the inertia of the lockring will tend to oppose the movement that was imposed by the spider, making it rotate counterclockwise). All this is represented in the image below.
Blue disk = spider + chainring
Orange disk = lockring
Blue arrow = rotation force impressed by the spider
Orange arrow = lockring intertial reaction
View attachment 33692
With this consideration, I agree with the Bosch designers: the ccw thread is a correct choice because its inertia works to tighten the lockring threaded connection with the spider.
Off-road, however, there is another stress that can become much more predominant: the kick-back generated by the rear suspension.
The stresses that comes from the rear swingarm in a high speed descent on rockgarden or woods create a reverse chain pull force that pulls the chainring back. These stresses are very impulsive, therefore they create a very strong acceleration (in short, a sudden jerk) that works in the OPPOSITE direction given by pedaling action. The consequence is that the inertia of the lockring works this time in reverse, leading it to unscrew.
It makes me believe (I repeat, they are my assumptions) that these stresses are more violent and above all much more frequent in AM, Freeride, Enduro, etc ... compared to those of pedaling (in Ednuro, AM, freeride, etc .. we're used to pedal quiet till the top then descend "full throttle"). We will therefore have a lockring exposed to a reverse stress, the inertia of which will then push it clockwise, thus tending to unscrew it. Jerk, after jerk, after jerk, the lockring becomes loose.
Having said that, were the Bosch designers wrong? NO. They simply imagined that most of the users with Gen4 will do easy and little off-road rides; in this case, I consider the choice correct.
Based on this, I tried to invent a solution to substantially prevent the lockring from moving clockwise because of the kickback
First, a small 2mm hole
View attachment 33693
... then a tap of a grinding wheel to create a small "pocket" on the inner face
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... and then a nice band of safety iron wire. And since security is never too much, even a bit of threadlocker.
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Now I just have to screw the ring nut again and practice the safety tie using one of the spider spokes. In this way the lockring is prevented to rotate cw (the one that causes the ring nut to be unscrewed) by the wire. It is the same system that I used on the motorbike on the track, where oil caps, brake screws and other components that could be unscrewed had to have the safety tie for regulation.
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Unfortunately, job agenda and bad weather do not allow me to perform tests
I'll come back to you in the next weeks with the first feedbacks from the field
Great little fix and if you do manage to break it/get it to fail, they will probably be scraping you off the scenery anyway due to the speed/abuse/height you were giving it just prior ??.