Cotta Transmission Cutaway Model

[crueby]

Hi Chris,
When I built my transmission models I purchased spline stock and spline bushings from Stock Drive Products.  I'm sure the dog rings slide on some kind of spline and making the internal splines would have been a real pain.

Hi George,
They didn't use splines on these early ones, the sections where the dogs were went from round up to a larger square section, a lot like the old line shop shafts did. Not the best for strength but easy for them to manufacture. I'm sure the more recent products from them went to splines.

[crueby]

RE the photo of the big shop.

"Head down and focus on the work boys. The suits are here to watch."

I think I can ID most of the machines and the work being done at most of the stations.

I did a small double-take: The man in the left foreground looks like he's playing with his laptop!!!! (What is he probably really doing?)

ShopShoe

   That guy up front does look like he has a screen, it must be some cast parts he is assembling there though.   

[crueby]

Got all the blanks trued both sides and trimmed to thickness, have started drilling/reaming the shaft holes in them, ready for turning to diameter on the arbor that will also be used for cutting the gear teeth (background).

Its repetitive work, but its Cotta be done!   

[Twizseven]

Chris,

This looks like another very interesting build.  I think you must use a different timeclock and calendar to the rest of us normal people.  Yours seems to have many more hours in the day.

Out of interest could your CAD plans be put through slicer software to produce gcode and then to 3D print the gearbox components and be able to produce a fully 3D printed model of the gearbox.

Have a great Christmas and keep the elves away from the wine and beer.

Regards,
Colin

[crueby]

Chris,

This looks like another very interesting build.  I think you must use a different timeclock and calendar to the rest of us normal people.  Yours seems to have many more hours in the day.

Out of interest could your CAD plans be put through slicer software to produce gcode and then to 3D print the gearbox components and be able to produce a fully 3D printed model of the gearbox.

Have a great Christmas and keep the elves away from the wine and beer.

Regards,
Colin

Hi Colin,
I forget that most of you live on that dimension where there are a measly 24 hours in a day!   

I did 3D print a version of this model a while back to verify that I had everything correct in my interpretation of the patents and ad pictures. It functioned, but being plastic it was a bit flimsy for use at the museum as a demo piece for visitors. I could have improved it with metal shafts and bearing inserts, but its more fun to build it all out of metal. The printed version did highlight a few things that needed adjusting, so it was well worth doing that before committing it all to brass and steel.
 
Chris

[crueby]

All of the gear blanks have been trimmed to length and diameter now, here are the sets for the two copies of the model I'm building (minus one that is already over on the arbor on the mill)


Here is that one set up ready for cutting its teeth:


And back and forth and roundy round with the cutter. I have made up the advance lists for the rotary table for all the gears, so as each cut is made another tick mark on the list to keep track of what the next movement is. For this gear, its two full turns plus 28.6 ticks from the previous location. The spreadsheet kept track of all the numbers and rounded them off to a tenth of a tick for me.


One gear down, 17 more to go!

I'll be taking breaks between gears to keep the brain sharp (as sharp as it gets anyway), getting distracted partway through one is not good. Keeping the list of moves and checking off each tooth helps.

[Charles Lamont]

I have been doing some dividing head work recently. I find it helps to repeat the mysterious incantation to myself as I do it "Two turns and six holes, lock and flip." ('flip' is the reminder to move the sector fingers round)

[Krypto]

It's no fun when you get at the end of the gear cutting and end up with a fat or skinny tooth!

[crueby]

Definitely  helps to be focused and  follow the same steps in the same order!  I write out the nbr turns and what tick to stop on for each tooth, and check them off after each cut, since I  am using a cranked rotary table, no sector or dividing wheel. Just as accurate, just a different process.


So far four gears are cut, all goid so far!

[cnr6400]

  I was trying to remember my list of tricks when starting a gearmaking project, but I drew a blank at first...      (sorry worst pun ever...this week anyway)

[crueby]

I was trying to remember my list of tricks when starting a gearmaking project, but I drew a blank at first...      (sorry worst pun ever...this week anyway)

My Director Of Pun Inspections would like to have a word with you...  (and yes, the acronym is a pun)



 

[crueby]

12 gears cut, 6 to go! 

[RReid]

That's a whole buncha teeth to pull out of that rod! Looking great.

[Michael S.]

But someone was very hard-working!
The gears look good 👍

Michael

[cnr6400]

  Gears are looking great Chris! (just my o pinion)