Longcase (Grandfather) clock with 3D printed gears etc.

[Gina]

Designed and now printing the pendulum suspension bracket.  Here are some screenshots from the slicer.

 

 

 

Edited February 6, 2021 by Gina
Typos

[Gina]

Screwed the pendulum suspension bracket to the back of the case and tried the pendulum on it - all good.  Then drilled and tapped holes in the back acrylic plate for screws and bearings fro the arms.  Finally put clock on the case, arranged the arms either side of the pendulum rod and took a photo.

 

[Gina]

With the escapement as well as the pendulum behind the back plate, I shall need a bigger gap.  I have some wider timber which I can use but ATM I only have an estimate of what gap I shall need, so I think I'll just use spacers for testing so that I can check what's wanted.

[Gina]

Printing some spacers. 

 

Also printed a "bracket" for the bearings that hold the arms.  Just a block actually to space the arms 15mm from the back plate.  This also means that I can enlarge the holes in the acrylic back plate for adjustment if needed.

[Gina]

15mm spacers fitted between back plate and side members of the case.  Now have clearance but not excessive.  The alternative timber I have for the sides would only give an extra 11mm so won't do.  Just as well I checked!  I can add some thin plywood to finish off the outsides of the case so that's not a problem.  Anyway, I need to get the clock working before I think of the overall appearance.

 

Here's a photo.  Looks alright so far.

[Gina]

Next job I think is to design and print the stops for the arms.  These need to be adjustable with the clock assembled even for testing and this adds difficulty.

 

The arms will need something to push (or pull) them towards the centre to push the pendulum to keep the clock running.  The clock I'm basing mine on uses weights but an alternative is springs - or one extension spring between the two arms should work

[Gina]

Have an idea...  A pair of cams on shafts going through the two plates to the front.  These could be Allen head bolts.  Here's a copy of the screenshot of the model in CAD - I think the cams could go just below the worm.

 

[Stub Mandrel]

1 hour ago, Gina said:

The arms will need something to push (or pull) them towards the centre to push the pendulum to keep the clock running.  The clock I'm basing mine on uses weights but an alternative is springs - or one extension spring between the two arms should work

 

Being mischievous, would a rubber band be a good fit with the clock concept?

[Gina]

That's a thought Neil 🤣  However I have a lightweight extension spring that I think would be ideal.

[Gina]

Designed and now printing cams.

 

[paul]

Very interesting and fun watching this unfold Gina👍

[Gina]

Thank you Paul.

[Gina]

Small redesign of the cams.  Installed and taken a couple of photos.

[Gina]

Seems I need to improve the arm pivots.  ATM I'm using small ball bearings like the clock I'm copying but they don't hold the arms well enough.  Also, ball bearings are not recommended for this sort of motion.  I'm thinking instead of SS bearing shafts fixed in the arms and running in plain PLA bearings.

[Gina]

Printed the bracket and the RH arm, fitted a 3mm SS shaft/axle and it lines up fine.  Now printing the LH arm.

[Gina]

The LH arm had lifted off the bed at the top end and the axle hole went wrong so will print another.  Also, the bracket was too narrow and the acrylic plate was not stiff enough to stop it bending downward very slightly from the weight of the arms.  Since good accuracy is required for everything to line up well, this cannot be tolerated so I designed a wider one.  Small holes are for the arm axles and the bigger ones for mounting screws.

 

Edited February 8, 2021 by Gina

[MarkAR]

Coming along nicely Gina. 👍

[Gina]

Thank you Mark 😀  Just printed replacement parts. tapped holes, tapped axle into hole in LH arm. screwed bracket to panel and inserted arm axles into holes.  Both arms are now parallel to the plate.  Success!!

[Gina]

Assembled parts of the clock so that I could test the escapement and see what adjustments are needed. 

 

Main problem is that the pallets the lock the escape wheel don't engage so probably need to be bigger.  Turning the escape wheel "waggles" the arms by pushing with the pushpins on the protrusions on the arms.

 

Back, where pendulum goes.

 

Front, the side that shows when the clock is completed.

[Gina]

Trouble is that every modification involves printing a whole new arm so I'm wondering if I can work out somehow to replace the critical parts separately.  ie.  plug in or screw in etc.

[Gina]

Here are screenshots of the CAD models of the present arms.

 

 

[Gina]

I think the lock pallets can be fixed.  The up/down can be adjusted by moving the pivot which is already moveable by moving the bracket.  I have made them slightly wider and I think this aspect can be covered by the cams.  I have put holes on the arms where the pushing parts go so that these can be printed separately and attached with screws.

 

 

[Gina]

Printed both arms and driven the axles in.  Tested in place and so far so good.  The pivot bracket wants adjusting slightly to level the arms and get the lock pallets equally spaced between teeth on the escape wheel.  This is easy - just need to loosen the fixing screws.  This adjustment feature was designed.

[Gina]

Designed the parts to add that push the arms outwards.

 

 

[Gina]

Attached the "push parts" with M4 screws and reassembled - it looks like it should stand a chance of working.  I need to arrange drive to the escape wheel.  I could attach a length of cord to a spoke on the escape wheel, wind it round the timing pulley and attach a weight.  However, if it went straight down the weight would interfere with the pendulum, so I need to arrange a side pulley.

 

I'll take some photos tomorrow and also hoping I may be able to run a real escapement test.

Edited February 10, 2021 by Gina