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Curta Calculator Scale Replica

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Robo_Pi

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I originally found the reddit post. The wording there had me thinking their intent was to build one.
Sounds like the guy has some cash. He says he paid someone to make all those Solidworks drawings. I can't imagine that being too cheap.

He also mentions that he might have some parts laser cut. If he's willing to farm out a lot of the machining work he might do ok. That post on Reddit has been archived. I wouldn't know how to contact this fellow. Maybe through his GitHub page?
 

ttabbal

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Those spiral parts make me want to put a stepper on my rotary table and use it as a fourth axis on my CNC router. It would need a jig to support the shaft, but I think it's at least possible.

For the gears I think if I were going to try for myself, I would make a stack of off center washers. Then file the keyway, put them on a mandrel and file or maybe flycut the gear teeth.

Or maybe I'll wait for @Robo_Pi to make a punch press and buy from him. :D
 

Robo_Pi

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Or maybe I'll wait for @Robo_Pi to make a punch press and buy from him. :D
I walked by the lawnmower today. :grin:

I was really tempted to start tearing it apart but I had to weld up my tractor hitch today. I know I know,.... excuses, excuses!

It's raining out now and I'm also hungry. So not it's likely I'll tear the mower down today.

Maybe tomorrow. Who knows?
 

Robo_Pi

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How to Calculate the Square Root of 2 on a Curta Calculator

 

racer8412

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Jeez a lots gone on since I last checked the thread, school was a pain but I did more research over the weekend and did START working on a punch die design, it's nowhere near being finished but i'm working on it.
 

Robo_Pi

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Jeez a lots gone on since I last checked the thread, school was a pain but I did more research over the weekend and did START working on a punch die design, it's nowhere near being finished but i'm working on it.
That's cool. :cool:

There's no rush on my part. I have no deadline. Obviously you would like to have a home-built Curta in hand inside of a year. I make absolutely no promises that you can meet that deadline. :grin: Personally I feel that if we meet that deadline I'll be tickled pink.

Is it possible? I have no clue. I don't even know if the punch press idea is going to pan out. I have been drawing up a punch and die in Fusion 360, myself, and I confess this doesn't look easy. We will either become the best punch and die makers around, or we'll fail. That's how life works.

I'm slightly optimistic in that if we can manage to punch out the center hole that alone will be progress. I don't know if you've read the details in this thread, but as a second alternative to punching out the entire gears we could just punch out disks with the proper center hole, and then machine the outside profile using a milling technique. So I'm confident that we'll eventually have some gears in hand. The only real question will be how much work it will take to produce them.

If we could succeed in punching out entire finished gears in one fell swoop, that would be much preferred. That production method would loan itself to ultimately building multiple Curtas with much more ease. On the other hand, if we end up having to machine the gears, even on a batch arbor that's going to slow down the whole process (although it might ultimately produce better gears that way). Either way we can still move forward. I'm thinking we're going to need the punch press either way. You may not need one as elaborate as I'm hoping to build with a lawnmower crankshaft. It may be possible to press these tiny gears out by hand on a manual press. I've always wanted a crankshaft punch press so I'm going in that direction for personal reasons.

But yeah, there's no rush here. I'm working on other projects myself. I won''t bother to list them all here. :grin: Too many to list.

It probably won't hurt to start thinking about how to make the sleeve that goes inside the gear: There will be over 30 of these needed. Three different flavors.

These are part numbers 10055 (aka 410354), 10056, and 10140 (aka 401359). They will all require similar machining and tools but there are subtle differences in their lengths and shoulders.

10055 aka 410354 Transmission Sleeve.JPG

10056 Transmission Sleeve.JPG

10140 aka 410359 Transmission Sleeve.JPG


The manufacturing process for these will be fairly easy. Just start with tubing of the right size, then turn down the smaller diameter on the lathe, and finally using a compression die to fold in the wedge shape. This can easily be done with a small hand press. But more dies will need to be made.

Time consuming to make them all, but fairly easy to make.

There will also be ferrules to go with these, But the ferrules are just short pieces of tubing, so those will just need to be cut to proper length.

Then the transmission gears will be finished and we can move on to making a transmission shaft. Although, in reality we might want to make some transmission shafts early on so we can have something to test-fit these sleeves on. The transmission shafts will also eventually need to have pinion gears that fit on the top of the shafts. But let's take one nightmare at a time. :grin:

The quickest way to turn these sleeves would be to feed in the tubing through the lathe spindle till it hits a preset stop. Then turn down the smaller diameter and part it off. Do this again and again until you're blue in the face or have all 30 some sleeves done. A collet would be preferred over a chuck for this operation, but not absolutely necessary. Then when these are all machined they would all need to be run through a compression die to form the wedge shape.

Just looking ahead. The ferrules would be parted off in a similar fashion. No other machining needs to be done on those.

I'm played out just having typed all this information into this post. :grin:
 

hman

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OK, thread is a bit old ... but I've bee binge-watching Adam Savage videos, and ran across this one. Enjoy!
 
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