|Bearing & Hardware
||2/14/12 8:02 AM
I'd like to get a list together of all bearings and other hardware that we might need for the clock so I can start rounding it up. I've been following the discussions so if you could just confirm the specifics to make sure we get everything we need in the right sizes that would be very helpful.
Bearings? brass tube? Just tell me what you need and I'll make sure we have it in the shop for next time.
On Mon, Feb 13, 2012 at 5:31 PM, Mathieu Glachant <syv...@gmail.com>
Looks like you were totally right on the arms getting damaged if the inner rings hits them too close to their attachment point on the outer ring.
Surveyor printed the second design out, and posted a picture in the comments showing that the ABS whitened under the stress.
I'm going to have to add some more arm length, perhaps with a solid spur under it to provide support to the inner ring...
I'll doodle something on paper to show what I mean, since OpenSCAD doesn't run on this laptop.
On Sun, Feb 12, 2012 at 3:48 PM, <ruste...@prototribe.net>
It looks like you're going to run into issues with the ratchet arm
flex. The inner wheel begins applying its force at the bottom of the
arm, meaning that it will need to do all its flexing right there at
the base of the arm as opposed to being able to flex across the
entire arm. You could possibly undercut the ratchet arms a bit or
possibly even punch a circle at the base of the arm on the side
towards the center of the circle (see the black dots in the pic
below). That may introduce enough flexibility into the arm.
Alternately either increasing or thickening the total number of arms
or taking a two tier approach should increase the axial load bearing
capabilities. Though in both cases the ratcheting will become more
Here's a quick sample of breaking things into two tiers. Note, you
can't really see it, but the arms are separated from the green disc
by about 0.5mm in this picture. It emulates what you've got in one
tier, while maintaining a high ratchet teeth ratio. The print is
trickier and would need to be done upside down (with the arms on the
build surface) and with support material. There are many variants of
this with the bottom disc having various parts cut-out or even
possibly replaced with triangular arms, etc...
I noticed that the ratchet drum you're using seems to be based on
the mcad gears lib and the teeth are sparse with the ratchet arm
faces not being in full contact with the ratchet wheel when bearing
load. I believe this may make a difference in the load bearing
capabilities as well.
Hope it helps!
On 02/12/2012 02:31 PM, Mathieu Glachant wrote:
I just published a derivative of RustedRobot's fine
ratchet design, which is intended to improve the axial load
bearing capabilities, removing the need for a complicated and
thick part with spokes that reach over the inner ring to reach the
It works (hopefully, anyway) by having the outer ring resting
directly on the inner one, with the ratchet arms only needing to
stop the rotation, not carry the axial load which is now
transmitted directly, ring to ring. This should allow us to
integrate a ratcheting drum into any wheel without breaking the
connection between large gear and pinion gear, adding more
thickness than the minimum needed for the string, or connecting
the drum externally via some sort of physical API.
Plus, it's even prettier than the original ratchet, possibly. :-)
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