Help me gut my altimeter!

[hyamesto]

Be patient.......
Meanwhile, i can show you my real altimeter.
Your missing piece is this shaft, with a gear......


With a piece of paper to better contrast....

Its a 12 teeth gear, one point connected to barometric part, and the other to drive the gearbox....

The next photo, is your broken 2 parts gear. Its a Gear compound....

The bigger gear has 40 teeth, and the smaller gear has 13 teeth. This are a gear compound, that is the gears are fixed to one another.
The next photo it´s the location inside the gearbox...



The gear system is:
Pinion 12 teeth pinion (direct 100 feet needle)
40 teeth -13 teeth gear compound 1
39 teeth -24 teeth gear compound 2 (Connected to 1000 feet needle)
48 teeth -12 teeth gear compound 3
60 teeth gear (Connected to 10.000 feet needle)


12 teeth pinion drive a 40 teeth gear compound 1. (3/10 relation)
13 teeth of gear compound 1 drive a 39 teeth gear compound 2. (1/3 relation)
24 teeth of gear compound 2 drive a 48 teeth gear compound 3 (1/2 relation)
12 teeth of gear compound 3 drive a final 60 teeth gear. (1/5 relation)

This is a 1:10:1000 gearbox.

A design with autocad......



But again, be patient, because this gearbox can be cut in acrylic.... but it´s no good for a simulated altimeter (remember the zeroing...).
With this gearbox, you need at least 100 turns minimal to zeroing the altimeter.
I recommend work with 100 feet and 1000 feet needle gearbox (10 turns to zeroing) and work the 10.000 feet needle with a servo.
Remember, the real altimeter has a effective range of -1000 feet to 20.000 feet for a Cessna.

Read this:

http://www.unitedinst.com/Products/S...s/d126281.aspx

In the weekend, i will try to upload a video of my others instruments...

Regards.
Horacio

[SimSupervisor]

Thanks a lot for those pictures and explanations. I never worked gears before, this will be my first time. I was hoping to just "use the original gears"...

I would be happy to have to drive "only" two motors. At the current point (without gearbox) I need to drive three, and would be happier with only two. If I would have the original gearbox I'd be OK to have a longer zeroing, but if I am to build it from scratch, you are right it makes no sense.

The only gear I am really missing, is the 40:13 gear compound. I still have the "center" 12 teeth gear, but its shaft was broken. I was hoping to manage another one. On my altimeter, the 48:12 teeth compound is passing trough the gearbox and the 39:24 teeth gear is on the other side compared to the 43:13. These still work. If the compound wouldn't be damaged, I'd be trying to interface to it with some motor.

But things being what they are, I am looking at making another gearbox. I'll see what I can come up with.

And post pictures of my trials and error in the process.

[hyamesto]

I´m sorry, but the 43:13 gear it´s really the most necesary part. Mine gearbox is equal to yours (the 48:12 passing trought gearbox too).
If you are interested in scrachbuild the original gearbox but with bigger gears (not change the functionality at all), i can make a Coreldraw file (every laser cut service accept this format) and send you the gearbox ready to make a laser-cut gears in acrylic, and with some brass or aluminium tubes and wires, you can reuse the rest of the instrument. I give you a list of materials, dimmensions and a guide to doing this.
Only need the exact dimmension (diameter) of the "circle" of piece in which is placed yours gearbox, and the shaft diameter of the stepper.


Maybe you should enlarge the holes of the needles to match the tubes.

Or, if you can wait, i must begin to design my altimeter, with servos and a stepper, and scrachtbuild the overall instrument.

Regards.
Horacio.

[hyamesto]

A beginning of design of my altimeter.....

Regards.
Horacio.

[SimSupervisor]

that could be interesting! I will look around for a place that does laser cutting, I guess I would have to order online.

How do you manage the needle shafts from the gears?

Thanks for teaching me about those kind of mechanism.



My original piece is 73mm wide, but where it sits in the original instrument, the border narrows the usable to aprox 66mm. Also, I will have to pass a geared potentiometer trough one of the holes to interface with the kollmans dial that is still geared to the kollmans knob. pierce on the area away from the three holes, where the actual knob is.

I still have to choose the stepper.

The way I see it, most of the time the instrument will be near ground at power-up, zeroing could in theory be done going down and wouldn't need the whole 100 turns every time. I don't think I mind the extra zeroing time.

[hyamesto]

How do I manage the needle shafts from the gears?, easy.....
Using K&S aluminium tubes, like

http://www.ksmetals.com

In Montreal, you can find in:

https://udisco.com/index.php

This are the telescopic aluminium and brass tube from my instruments and some music wires (not showed), gluing the laser cut gears to them....



Regards.
Horacio.

[SimSupervisor]

That's a great idea!
I'll get tubes and manage my design from there.

This is going to be interesting to learn

[SimSupervisor]

That's a great idea!
I'll get tubes and manage my design from there.

This is going to be interesting to learn