To see this working, head to your live site.

Goodbye ratchet springs

Steve,

I absolutely love your clock designs & have had a great time printing & assembling mine (Large Moon Phase). I'm working on a second one for a gift & decided to replace the metal springs in the ratchet with print in place springs on the clock. Three less pens I have to destroy for their springs. ;) Anyhow I thought I'd share in case you'd be interested in removing some springs from your fantastic design.

Kindest regards,

T.J.

This prints with the screw countersink down.

This includes gear 7 without the spring holes.

6 comments

6 Comments

TJ Reichert

Beautiful clock! Glad to hear the springs are working for you. I have them in 2 clocks & have been running them for quite a while now without any problems.... yet. :)

TJ Reichert

Very cool! Your changes make all sorts of sense. Thanks for sharing.

rscamp

Replying to

I just finished building the clock. The plastic springs seem to work fine and the clock has been running on test for over 24 hours now. I'm really impressed with the quality of Peter's design and the provided Assembly Notes. These have to be top notch if I was able to get it to run first try! 😀

rscamp

When I bought the build files for SP14 I thought I would try plastic springs for the pawls. Before I even started I found your post. Thanks for coming up with this good approach and saving me some work! I did modify what you had done for the convenience of using the original Gear 7b.

Here are a couple of considerations with regard to stress and fatigue failure of this plastic spring. Firstly, the shallow step in Gear 7a Ratchet results in only small incremental strain which is helpful. Secondly, I found a reference that indicates it is possible to achieve a very high cycles-to-failure with PLA if the stress is less than 1/10 the ultimate strength of the material. Here is a link to the paper "On the fatigue strength of 3D-printed polylactide (PLA)"::

On the fatigue strength of 3D-printed polylactide (PLA)

Now if someone could do an FEA analysis and/or make a test jig and do a cyclic stress test on this part we'd be all set. 😀

TJ Reichert

May 27

Understandable, I thought the same but with these types of flex springs the flex is along the whole spring length & not isolated to one small area. Theoretically they should last quite a while. Time will tell. Thanks again for sharing your fantastic designs.

T.J.

Steve

May 27

That's a good design. Thanks for posting.

I never design flex parts because I expect the clocks to last 10-20 years and don't know if PLA can handle that much flexing. If the spring holes were left in place, then there would be a quick recovery if the tab does break off.