How to Convert a real Cessna Altimeter for Sim use.

Thanks,
Im going to try a digital servo i have and will see how it goes. Is nice to know the jrk works well.
Les

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Originally Posted by 737NUT

I recently purchased a Cessna Altimeter off of Ebay for less than 20.00. (they have several more) I gutted the insides below the main gear plate. The main gear plate holds all the gearing for the pointers and the pointer mounts. This means all you have to do is have one shaft going to the original to make the altimeter work. So, use the methods found in Mike Powell's Building Gauges for Flight Sim's, I went forward with this little project. My goal was a servo based 0 to 20,000ft altimeter. Each turn of the main shaft gives you a 1000ft on the altimeter. I wanted a 20 turn pot for the feedback but found they were to cost prohibitive. I instead opted for the much cheaper 10turn 5K pot. So now I have to gear it so it turns only 180 degree's for each 360 deg turn of the main shaft to keep my 0 to 20k ft. I put a 14t on main shaft and a 28t on the pot. For the motor, i used a nice little geared motor from www.Servocity.com, It runs on 5-12vdc and turns 40rpm with loads of torque, way more than needed here. I have a 12t pinion on it and it drives a 55t gear on the main shaft. (see pics) I gutted a cheap Hitec servo, soldered the pot in place of the servo's pot and did the same with the motor. Voila, a servo driven real GA Altimeter. Works well, very smooth and quiet. This was actually much easier than anticipated. Using Mike's methods for making the shaft and how to build it up for the gears worked great. I could have had a fancy metal plate made for the bottom support but to svae time and money, I used some hobby grade 1/8" light ply. Not pretty but it worked and was cheap. I have a total of about 80.00 in this including the gauge. Any questions feel free to ask.

Rob

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Why did you not use the original servo motor? I love the topic, thanks!!

The Cessna altimeters are the mechanical air chamber type. I removed the air can and gear and arm and replaced with the electronics and nylon gears and brass tubes as axles to make it work. I can say that If I adjust the Alitimeter to match FSX at Startup, it is dead on for the rest of the flying trip. I am very satisfied now with the results.

Unsterstood. Im just not sure why you replaced the Hitec servo motor with another motor? Im sure there is a good reason.

I do understand why you use the multi turn pot on the servo.

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Originally Posted by dc8flightdeck

Unsterstood. Im just not sure why you replaced the Hitec servo motor with another motor? Im sure there is a good reason.

I do understand why you use the multi turn pot on the servo.

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I wanted a geared 6v motor that had more torque and only turns 12rpm. :) The servo motor is to fast and to hard to adapt to the gears I used.

Quote:

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Originally Posted by 737NUT

I recently purchased a Cessna Altimeter off of Ebay for less than 20.00. (they have several more) I gutted the insides below the main gear plate. The main gear plate holds all the gearing for the pointers and the pointer mounts. This means all you have to do is have one shaft going to the original to make the altimeter work. So, use the methods found in Mike Powell's Building Gauges for Flight Sim's, I went forward with this little project. My goal was a servo based 0 to 20,000ft altimeter. Each turn of the main shaft gives you a 1000ft on the altimeter. I wanted a 20 turn pot for the feedback but found they were to cost prohibitive. I instead opted for the much cheaper 10turn 5K pot. So now I have to gear it so it turns only 180 degree's for each 360 deg turn of the main shaft to keep my 0 to 20k ft. I put a 14t on main shaft and a 28t on the pot. For the motor, i used a nice little geared motor from www.Servocity.com, It runs on 5-12vdc and turns 40rpm with loads of torque, way more than needed here. I have a 12t pinion on it and it drives a 55t gear on the main shaft. (see pics) I gutted a cheap Hitec servo, soldered the pot in place of the servo's pot and did the same with the motor. Voila, a servo driven real GA Altimeter. Works well, very smooth and quiet. This was actually much easier than anticipated. Using Mike's methods for making the shaft and how to build it up for the gears worked great. I could have had a fancy metal plate made for the bottom support but to svae time and money, I used some hobby grade 1/8" light ply. Not pretty but it worked and was cheap. I have a total of about 80.00 in this including the gauge. Any questions feel free to ask.

Rob

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Any idea how much voltage these servos can handle? I have 28v DC motors.

Justin

Hi Rob, could you please give me your email ? i would like to contact you for the altimeter...
pablo@dimobili.com
Thanks
Pablo