The drill is screaming!
I'm installing Shimano's cylindrical electric component battery into the seatpost.
↑This is the type of pressure anchor I'm modifying.
I cut off the upper flange...
...and drilled a wrench flat hole in the lower washer.
The drill only screamed at this point.
Since the pressure anchor's threaded hole is M6,
the 5mm outer diameter electric cable fits through without modification.
I insert this flush with the seatpost end surface
and apply pressure, but it's tedious
because turning the wrench flat without spinning takes a trick.
What really gave me trouble was dealing with
the anchor's spacer and the battery's rattle suppression.
I considered more elaborate methods, but the parts count increased
and approached the weight of an external battery, so I abandoned that.
I also gave up on this approach.
So I went with this instead.
The drill isn't screaming at all.
I tape spokes to the battery,
then wrap cut sponge over it with cable ties.
I don't cut the cable ties because they also serve to prevent rattle.
↑The bottom of the battery is hooked like this.
↑I offset the top of the spoke
so it sits directly above the battery's outer diameter.
I install this in the frame rather than the seatpost.
The customer asked for "as low center of gravity as possible," so this works perfectly.
The sponge is just cut from regular kitchen sponge,
but its thickness lets me adjust the holding force against the frame.
This frame has a 31.6mm inner diameter, and
when I actually pushed it in, it held firmly.
↑It stopped here.
If riding vibrations cause the spoke to flex and tap the seatpost,
I can adjust the spoke shape or sponge thickness.
I added a hook so the battery is easy to pull out.
But I got a bit worried, so I kept the hook length minimal.
It goes quite deep into the frame,
but it's easy to retrieve with a spoke or wire.
Also, with this length in this case,
there's no overlap with the seatpost, so there are no interference issues.
I'm installing Shimano's cylindrical electric component battery into the seatpost.
↑This is the type of pressure anchor I'm modifying.
I cut off the upper flange...
...and drilled a wrench flat hole in the lower washer.
The drill only screamed at this point.
Since the pressure anchor's threaded hole is M6,
the 5mm outer diameter electric cable fits through without modification.
I insert this flush with the seatpost end surface
and apply pressure, but it's tedious
because turning the wrench flat without spinning takes a trick.
What really gave me trouble was dealing with
the anchor's spacer and the battery's rattle suppression.
I considered more elaborate methods, but the parts count increased
and approached the weight of an external battery, so I abandoned that.
I also gave up on this approach.
So I went with this instead.
The drill isn't screaming at all.
I tape spokes to the battery,
then wrap cut sponge over it with cable ties.
I don't cut the cable ties because they also serve to prevent rattle.
↑The bottom of the battery is hooked like this.
↑I offset the top of the spoke
so it sits directly above the battery's outer diameter.
I install this in the frame rather than the seatpost.
The customer asked for "as low center of gravity as possible," so this works perfectly.
The sponge is just cut from regular kitchen sponge,
but its thickness lets me adjust the holding force against the frame.
This frame has a 31.6mm inner diameter, and
when I actually pushed it in, it held firmly.
↑It stopped here.
If riding vibrations cause the spoke to flex and tap the seatpost,
I can adjust the spoke shape or sponge thickness.
I added a hook so the battery is easy to pull out.
But I got a bit worried, so I kept the hook length minimal.
It goes quite deep into the frame,
but it's easy to retrieve with a spoke or wire.
Also, with this length in this case,
there's no overlap with the seatpost, so there are no interference issues.