Gina

Calculation for the main drive chain sprocket which will be attached to the green gear in the photo above :-

1. Radius of the gear  = 84mm
2. Pitch radius if sprocket teeth wants to be less say 75mm
3. Link pitch = 20mm
4. Circumference of new sprocket at tooth pitch = 471mm.  Maybe 480mm which is 24 teeth.
5. New diameter of tooth pitch = 152.8mm so radius = 76.4mm
6. Angle per tooth= 15°

The chain drive gear was too big so I've made a new one.

Been designing the chain drive gear.   The first photo shows the gears laid out on the new acrylic panels and in the second, I have removed almost all the parts from the Mark 1 clock to make use of the panels and framework to test the gearing.  Once I have finalised the layout I shall transfer it to the new panels with the clock face further up the space.

I have been experimenting with printed gears to test the feasibility of fewer gears and I'm going to try it.  In the attached photo, the yellow gear is the centre/minutes wheel and drives the orange gear with a 10:1 ratio.  This in turn drives the escape wheel (light grey) with a 6:1 ratio giving an overall ratio of 60:1 as required.  The position of the escape wheel makes its shaft ideal for a seconds hand with  dial just below the 12 o'clock mark.  The smaller gear on the main centre wheel is for the chain drive.

I did another net search to to see if I could get any ideas for alternative clock mechanisms and found one with a reduced number of gears as shown below.  Fewer gears might help to reduce friction and would unclutter the clock a bit.  The doubt was whether the higher gear ratios would work but with a bit of testing I think they may.  One advantage of one less gear pair is that the escape wheel turns clockwise which would allow a seconds hand to be attached to the shaft.

I couldn't get the original (Mark 1) clock to work properly and also decided I was trying to cram far too much into it and it was very cluttered.  These points together made me decide to start again with just the main clock mechanism and get that working first then add other bits.  So I've dumped the perpetual calendar and that will go into a separate project.  I'm keeping the auto-winding mechanism as I'm too lazy to wind it, and the moon globe as that is no problem (much the same as the Moon Dial Clock).

This blog continues from my threads in The Lounge, in particular  DIY Grandfather (Longcase) Clock Mark 2

The box makes use of 500mm square x 4mm acrylic sheets providing right-angle corners.  The build volume is about 300mm (1ft) cube.  The printer has been designed to be capable of printing with any sort of filament of 1.75mm diameter with an extrusion temperature up to 300°C and bed temperature up to 150°C, though I have only tried with 280°C and 110°C.  I am currently using a 0.8mm nozzle though other sizes are available (0.4mm, 0.6mm, 1mm and 1.2mm).  Printing surface is borosilicate glass 300mm square which is heated with a 24v 300W heating pad.

The electronics uses the RepRap standard Arduino Mega 2560 microprocessor board and the RAMPS interface board, powered by a PC style ATX PSU with +5v and +12v power rails and providing the power for the stepper motors and hotend heater etc.  Power for the print bed heater is provided separately by a 24v PSU.  Heating is quite fast taking about 4 mins to get from 20°C to 100°C.

I had originally designed this printer to use Bowden filament feed but this proved so troublesome that I made the decision to use direct feed with a small, lightweight extruder and stepper motor mounted on the X carriage.  This is the E3D Titan Extruder (the name is a coincidence - I named my printer before their extruder came out) and is not only small and light but is reckoned to have a superior hobbed shaft.  I am also using their Volcano hotend with better filament heating and flat ended nozzles.

This printer is based on the RepRap principle with all parts readily available and all designs open source.  Furthermore, this principle often makes use of one 3D printer to make parts for another and this printer embraces this principle wholeheartedly.

The construction is based on a box to provide the main framework and this also provides a fume cabinet for using ABS filament which gives off noxious fumes when printing.  To provide views of the printing process three sides and the top of the box are clear acrylic sheets.  An opening front door provides access.  Base and back are currently 6mm plywood with appropriate bracing but I'm considering replacing it with thicker material.  In line with the RepRap principle the corners of the box are made from many 3D printed plastic sections including door hinges and catch.

For the main movements in X, Y and Z directions, V-slot aluminium extrusion is used in combination with matching ball bearing wheels.  This provides smoother, more accurate and more reliable movement than stainless steel round rods and linear bearings.  It is also a lot lighter than stainless steel rods.  This printer (as can be seen) moves the nozzle in the XY plane and the print bed to provide Z motion.  This arrangement was chosen because the X and Y axes have the main movement and reduces the effective moving mass.

The drives use ultra-low stretch and very strong fishing line cord rated at 100lbs breaking strain.  This is driven by drums and runs over ball bearing pulleys for the X and Y drives.  This arrangement uses fixed motors and avoids having their rather high mass on moving parts.  The Z drive uses 3D printed spur gears to provide a reduction drive from stepper motor to drive drum.  The drum is on a horizontal axle and simply lifts or lowers the bed with cord.  As with the X and Y stepper motors, the Z motor is also mounted on the back panel.

Titan printer front view with door off.

As requested, a photo of the finished clock.  I'll be adding details of the construction shortly, copying relevant excerpts from my rather long thread in the DIY Astronomer forum.  It's not really a blue moon, it's lit with a white LED but the digital photo has coloured it blue

A couple more photos.  X carriage and rail just on the table and top view of both X and Y carriages.

The X carriage partly equipped.  Needs hotend heater and various cables.

This top  view diagram shows the principle - this actually refers to my biggest 3D printer project but the same principles apply.  This Mini printer is simply a smaller version of the bigger one.  The orange square with the red border is the print bed, the rail sticking out from under each side guides the bed and holds it in the right horizontal position.  The ends of that rail are attached to two carriages that run on the side uprights which form the Z rails.  The print bed moves up and down to form the Z axis.

The X axis is comprised of the horizontal rail shown above the bed, which the X carriage runs on.  At the ends of the X rail are the two Y carriages which run on the two front to back rails.  XY motion is controlled by cords running over pulleys and attached to drums on a pair of stepper motors.  This drive arrangement for the X and Y axes is called Core-XY.

Decided to use a different corner fastening instead of the plates.  Once built the sides will be boxed in with clear acrylic sheets.  This will stiffen everything up (if it isn't stiff enough anyway) and provide a fume cabinet for printing ABS.  The frame will be constructed from V-Slot rails some of which will take the wheels of the carriages.  The Y carriages run on the lower top horizontal rails and the Z carriages on the inner vertical rails.   V-Slot extrusion is actually cheaper than other sorts.

I can't seem to be able to edit the description of this entry   I haven't been using blogs until just recently but found this and thought I could edit it to a proper entry.

I am new to blogs but I think I have sussed this out.  The forums are more suitable for posting things where the main purpose is to ask questions or have a discussion.  Blogs seem to be more suitable for build projects where the main content is going to be contributions by the originator and there may be fewer questions or comments.  Also, unlike the forums, blogs have a two level structure where each blog can have a number of sub-sections with each of those similar to a thread in the forums.  If I have this wrong maybe @Ant can correct me

The main frame.

I think I need to look at some other blogs.  Have to see how I do that...

Do I add the next post here?

Do I continue here like on the forums?  Curious!!