Gina

Here's the escape wheel error - 32 rather than 30

That is wrong.  I think I have a clue what I did wrong due to a brain malfunction!!!

Yep!!  Found it!!!  Try counting the teeth in the escape wheel below.  From lots of coding with binary numbers there are 32 teeth rather than 30!!  DOH!!!

That error is too big to be anything other than a calculation or CAD error on my part!!!  I shall go through the design again very carefully, checking every step!

That didn't do it and the separation of the pallet lock surfaces are a whole 3mm too far apart as compared with the escape wheel teeth.  I just don't know how this large error could have arisen!!.

Fitted the new anchor and it nearly works.  The corner of the RH pallet Is just catching.  I think I can just take a file to the print and remove a small amount.

Slimmed down pallets.

Photo of the escapement.  The LH pallet is about to release the tooth on the escape wheel, but the RH pallet is not clear of the corresponding tooth so cannot move into the gap between teeth.  I see no reason why the pallets shouldn't be a bit narrower.  The drive period would be reduced slightly but that's secondary, I think.

Set up the testing for the clock but the new anchor is wrong.  I don't understand why though - the pallet separation (width of anchor) seems wrong in practice and different from the CAD design.

New escapement anchor finished printing with good result and installed in clock.  I'll leave testing until tomorrow but it looks promising.

New anchor design with reduced drive part angle.

This is a CAD screenshot.  Think I'll try reducing the "drive" projection into the tooth circle.

Analysing that video it seems the RH pallet on the anchor is not working correctly.  I need to redesign the anchor.  Maybe there's too much "drive" angle.

Have the clock assembled including the double weight drive system and stepper motor.  The drive is working and the clock partly runs but there is still the problem that the escape wheel is not exactly even in the position of the teeth relative to the anchor.  I can adjust the anchor height for optimum performance but when the clock runs over part of the escape wheel it skips teeth on the opposite side.  The problem is that the tolerance is just a few tenths of a mm.  OTOH I wonder if the shape of the pallets is ideal. 

Here are photos of the test rig and a closeup of the escapement.

It's printed well and seems fine - vast improvement!  Didn't realise stale filament could be so troublesome!!!

Just printed a new escape wheel with fresh filament to see if it is any better.  Presently cooling.

I agree, involute gears are designed for lowest friction I gather and is what I'm using as I see no need to stick with tradition in my clocks.

I'm going to have to reprint the escape wheel, as in spite of extreme care, the axle is not in the centre of the points circle!!  Or indeed of the pinion.  How this has happened I don't know!!!

An alternative to printing new gears might be to drive the intermediate wheel rather than the centre wheel giving 8x more "leverage" to the drive.  To cater for this change the stepper motor for auto-winding could be driven at 8 steps per second.

Now to the auto-winding system.

With the current system the timing pulley rotates 4x an hour (15m) and I plan a 20t timing pulley on a stepper motor. 

Some calculations :-
    Timing pulley ("great wheel" in clock parlance) takes 15m per revolution = 15x60s = 900s
    Timing belt and pulleys have a ratio of 90:20 so motor pulley takes 900x20/90 seconds per rev = 200.
    NEMA steppers have a stride angle of 1.8° degrees or 200 full steps per 360° (revolution)
    Thus stepping the motor once per second gives the required rate for auto-winding.
    Q.E.D.

This is a photo of the clock "going train".  The white wheel with the timing belt hanging over it is a 90t timing pulley (3D printed).  Under that and attached to it is a 40t spur gear.  Centre wheel is 80t.  Next is 10t pinion on a 75t spur gear which drives a 10t pinion on the escape wheel.  All spur gears are mod 2.25.  The going train has ratios of 8:1 and 7.5:1 (8x7.5 = 60).

On 23/01/2021 at 23:31, Stub Mandrel said:

That would let you double the pinion tooth counts and get a better form.

Do you think that would produce better gears with lower friction?  I'm just wondering if printing new gears with lower modulus would make my clock work better.

Cost of the C-Beam and gantry plates comes to just under £100.  Then I would need to see what V-Slot wheels I have plus a few other bits.  At least these parts are available from a UK supplier and in stock - at least ATM.  All food for thought...

Judging by the Z drive in the Concorde printer with standard NENA17 stepper motors, I think NEMA17 will be strong enough for the Giant, at least the longer ones, which I also have.  I can use the same case as before with aluminium extrusion and acrylic sheet.  I see no real reason to change ATM.  The C-Beam Linear Rail would be less than a metre high as the Z drive would be below the XY plane like with the Concorde.

@tekkydave