Yes they are expensive but looking at the post from John they will get a proper workout so maybe not expensive. On the other hand you could make them and Mod 1 is one of the easiest as you can use standard tooling. I made a tangential cutter to make the shape on one side of the cutter then flipped it over to do the same on the other side.

Oh dear, I had hoped not to get drawn too deeply into this discussion, but, in for penny ….

I’ll just add a couple of links which a) may be of general interest and, b) might help.

“Clickspring” on YouTube has many videos on clockmaking, as well as his renown reconstruction of the Antikythera device.  This link will take you to a video describing the manufacture of a cycloidal gear cutter – or, at least, a close approximation thereto.  The notes in the video description link to the (free) spreadsheet calculator to which he refers in the video.  It downloads as an XLS file, which I loaded into LibreOffice Calc with no problem:  Cycloidal gear calculator

Let me just add that I have no experience in clocks or cycloidal gear making.  You must decide for yourself if the linked information is any use to you.

John

One thing that might point towards cycloidal gears as a good choice is the fourth row down, where it says ’11t lantern (pinion)’.

An 11t involute gear is technically without the range of a standard set of gear cutters. It is not a showstopper but would require some thought.

On 20 September 2024 at 04:52 Alan Charleston Said:

You said:

Is it possible to convert a 3D model in a pdf file to an orthographic projection.

There are some difficulties with your thought process.

In your first post you say “There is a 3D rendering of the item [in the pdf]”.

Yet you ask ChatGPT about a “3D model”. The answer it gives is correct for the question it has been asked.

The problem is that you have not asked it the same question you ask in your initial post.

A 3D rendering is not a 3D model.

The rendering is a screenshot or photograph of the model, not the model itself. Unless the model information is embedded into the pdf, it will not be possible to extract anything other than the picture shown above.

You can think of it as the distinction between attaching a screen capture of a spreadsheet in an email and attaching the actual spreadsheet file to the email. You cannot take the screenshot and do anything meaningful with it in Excel.

In order to embed the model, you need a pdf _writer_ with this capability. Unless the creator of the pdf has that software, knows how to drive it correctly and performs the embedding step, the model will not be in the pdf.

Give your ChatGPT a second problems: upload to it the pdf file and ask it to find the 3D model hiding within. Using my own natural stupidity, I tried it here (https://pdfcrowd.com/inspect-pdf/) and it tells me the pdf file contains two images (pictures).

On 21 September 2024 at 07:16 Alan Charleston Said:

Hi DC31k,

It’s a 3D Model in the pdf file as the image can be rotated to show different views and individual elements can be viewed in isolation…

Alan is correct in that what’s inside the PDF does much more than render.   Appears to emulate a sub-set of a 3D-CAD display.  The rest of the CAD tool is missing so you can’t edit the model or export technical data from it.   Part  dimensions can be viewed and extracted manually, but a huge amount of work.

“Universal-3D” feels like a good idea that never caught on.  An advanced viewer that allows PDF readers to rotate around 3D-parts and animate 3D-assemblies, probably using a stripped down version of the original CAD model.  Possibly too complicated a feature for management, and not complicated enough for CAD trained engineers!

Although  u3d was open-sourced, I can’t find it.  Might have come with an extract tool useful to Alan.  I don’t think it’s related to the active game platform U3D, or if it is U3D has moved a long way from the original concept.

Dave

Interesting project, having perused the orrery site and videos for a while and noted that Gearotic only offer a fully paid for version, have decided that the best route for producing gear drawings is via fusion 360 using their involute gear form generator. The other parts will have to be done by ‘hand and brain’. As the maker states, it is largely an artistic endeavour rather than a precise astronomical calculator.

Involute gears preferred for me because I don’t think friction build up is so critical as the mechanism seems to operate from high to low speed (possibly excluding the moon and Mercury). Mod 1 cutters are readily available, the pcd distancing is less critical and may be easier to set up. Also might be able to purchase small bevel gears rather than attempt to make.

I noticed the motion of the calendar wheel on the original version was rather erratic and thought it might be due to meshing issues between the small lantern pinion and its driver, so the performance of these two gears may be quite critical.

The query I have is the 11t gear undercutting in involute form. Not sure how to achieve this. Could it be done by carefully filling away the tooth flanks and checking clearances with the 147t driver? Would the driver teeth also need modifying or topping in some way for smooth action?