• Linear motion hack

    lion mclionhead • 3 days ago • 0 comments

    The current design has a single ABS pushrod creating a linear brush motion & a rotating brush motion.  The rear cover can be popped off with destructive force.  It still can be pressed back on.

    The problem is the motor pushes 1 way on the linear section while relying on a spring to push the other way.  The spring doesn't have enough force, so the stress of the bristles tends to stick the brush all the way in 1 direction.

    The motor seems to push both ways on the rotating section, so it doesn't have any problems.

    The 1st idea was to clean off all the silicone grease & try gluing the pushrod to the linear brush.  Helas, a medium CA glue just went all over the place & stuck the brush solid.  It actually did stick to the pushrod, but fractured between the pushrod & the brush. 

    During this process, it became clear that this mechanism was intended to reduce the manufacturing precision.  The start & end point of the linear motion is non deterministic.  The easy solution is to have the motor push 1 way from any starting position.  Then the spring pushes the other way from any ending position.  Trying to fix the pushrod to the brush would make the pushrod hit a hard stop & break. 

    Some further ideas are increasing the tension of the spring & increasing the voltage to make the linear motion more assertive.  If the linear motion can't be restored, it might be good enough with just a rotating brush.  That's all the 2000 edition did & what all the other toothbrushes do.