Cotta Transmission Cutaway Model

[crueby]

Thanks guys!  Just cut the first of the largest ones, one more big one and then the smallest ones left. I left the smallest ones to last since cutting them will dig into the end of the arbor a bit. 

[Zephyrin]

it's good to stay focused enough to cut all those teeth manually without mistakes, congratulations !
I envy you, but is not finished yet

[Kim]

Whew!  That's a lot of gears!  You're on the downhill side now, Chris.   

Kim

[crueby]

it's good to stay focused enough to cut all those teeth manually without mistakes, congratulations !
I envy you, but is not finished yet

Yeah, I hear you!  I'm able to do one or two gears at a sitting, then need to go do something else for a while and let the brain reset.

[john mills]

Hi
wonderfull to see all those gears.
cutting on the dividing head is very satisfying as the teeth take shape.but takes concentration.
Would the original teeth have been a stub form.I have cut a lot of gears on hobbing machines that were American stub form mostly 14 to 3.5
dp 20degree pressure angle.
john

[crueby]

Hi
wonderfull to see all those gears.
cutting on the dividing head is very satisfying as the teeth take shape.but takes concentration.
Would the original teeth have been a stub form.I have cut a lot of gears on hobbing machines that were American stub form mostly 14 to 3.5
dp 20degree pressure angle.
john

If you look at the Cotta ad in the first post on this thread, you can see their drawing of the tooth form. Definitely a flatter top shape than the standard involute that I  am using. Is that the 'stub' form? And I  am using a rotary table, not a dividing head, to cut the gears. This is the Sherline rotary table, 5 degrees per full turn of the handwheel.


 

[crueby]

All the gears are successfully cut!        Here are the sets, one for each model:


Here is one of the sets arranged about like it will be in the finished model. The input shaft comes in at the upper left, the output shaft goes out at the upper right. The long gear at the bottom right is the reverse idler, it will connect the two right hand gears. Some of the gears will be fixed to the shafts, some will be free-spinning when the respective clutch is not engaged.


Next up will be to cut the dog clutches...

[Roger B]

That's some fine work 

I will be following along   

[crueby]

That's some fine work 

I will be following along 

Glad to have you along for the ride!

Just looking at the clutch rings/carriers, think I may need to make up a square broach cutter for the center holes, for where they slide on the square shaft sections. I have an arbor press and normal keyway cutters, but I'd rather stick with the square sections on the original.

Hmmm... seems like a normal keyway broach cutter with a new guide/holder setup could do the trick too? Something to ponder after lunch!

[Roger B]

I also need to make a rectangular hole for my Junkers engine. I looked at my keyway broaches but the cutting edge is narrower than the body so I may need to make a custom broach 

[Krypto]

Nice job on the gears! That was a lot of cutting.

Yeah, square broaches are expensive! I only have a used one in 1/4" that I picked-up years ago that I thought might come in handy for a tool holder at some point.

You can buy sleeves that are already broached square that could be pressed into your gears.

http://www.greenbaymfgco.com/12L14-sleeves.php

Some other shops sell these as well.

[crueby]

Been playing around, sketching in Fusion to see if I could adapt a normal keyway broach, not much progress there. BUT, I remembered a little broaching tool that CNR taught me how to build way back in early 2019 when I was building my Marion steam shovel, and needed to put some squared recesses in the inside edges of the slew/crowd engines. Here is a like to it, from Feb 27, 2019:


https://www.modelenginemaker.com/index.php/topic,7530.msg196208.html#msg196208

Went and dug it out of the back corner of a shelf where it has been patiently waiting, just knowing it would be used again someday, and took some measurements of the cutter and the frame. It has a 3/8" wide/.362 deep cutter head on it, which would nearly fit fine in a 1/2" hole in the parts I am doing now. If I first broach a keyway, then it DOES fit in the hole. Then, could use it to nibble away the corners of the hole as needed. The clutch slider parts are over 1" thick, so using a small end mill wouldn't work for the entire hole, this way would work if I make a little holder for the part to hold it aligned on the end of the tool's frame.

Yes, I could spend a lot and get a normal square push broach, but I don't have a press that is tall enough for a 1/2" version. Could also buy a rotary broach, also expensive, and it would have to work on a deep hole. This tool would work in my arbor press, AND I already have it made (it might just need a slight sharpening on the cutter, it was used to cut two slots each in 4 steel engine frames).  And its a lot of fun to use a home made tool for oddball jobs like this!


Hmmmm.....   

[wagnmkr]

Go for it!   You know you want to!

 

[crueby]

Go for it!   You know you want to!

 

Yup!

[crueby]

There is also this neat video from Clickspring showing how to make a push broach.
https://www.clickspringprojects.com/square-broach.html