Building an AUTOMATIC MUSIC BOX - HELP!

[Maydori11]

Hello everyone, I am a music composer and total noob. So please excuse my lack of engineering knowledge.
I recently purchased a DIY music box kit from a website . it has a tiny hand-crank, and it's thus next to impossible to play your custom tunes at a constant rate. The thing sounds like crap for this reason alone.
I'd like to automate the crank with an electric motor, since I am under the impression that it's pretty hard to make your own wind-up music box (difficult to get the wind-up mechanism to turn at a constant rate, involves fans and other intricate timing mechanisms, etc).
I am attempting to build a music box that can play without having to turn the gear's crankshaft manually. Here is a picture of the music box:
I have been doing some research and think I have a rough plan. Please correct me if I am wrong, I think I need a DC motor like this one:

Do you guys think this is a good motor to turn the gears? I also want to be able to change the speed so I guess I'll need a rheostat or potentiometer. Which is better and what specs do I need? Will I need to match the voltage of my motor? What batteries are good for this? I would like to save space so if I get two 9 volts = 18V will this be too much for my little 12V motor? Is there a good package kit that has a motor and speed control together? thanks ahead of the help and advice!
Should I tinker an mechanical connection to the crank of the music box ? A 9V battery and a linear regulator like the LM317 from kynix semiconductor can make some difference?
Any advice will be grateful ! Thanks advanced. Thanks for help solving my problem.
Regards,
Maydori
Have a good day!

[Mick Bailey]

I have a very similar unit I bought in the 80s. I used a cigar box and mounted the player on a diy soundboard and it gives a really haunting sound. Better manual speed control can be had by increasing the throw of the crank. As it stands, the crank has too little offset and is fiddly to keep an even rotation.

If you decide to go the way of motorising the unit, be aware that if it jams you need the drive to slip, otherwise the plastic gears can strip.

For speed control a rheostat or pot is not that much better than a hand crank. The load on the music box is not constant - it varies according to the perforations. This can be overcome to a degree by reduction gearing. I would opt for pulleys and rubber-belt drive to get the motor speed down to somewhat higher than you actually need, then reduce the speed to the desired setting electronically. DC motors are best controlled using a PWM supply and a simple supply can be built using a 555 timer as the pulse generator. There are plenty of sites on the web describing how to do this and it's a common technique for simple robotics and model railway control.

[Maydori11]

I have a very similar unit I bought in the 80s. I used a cigar box and mounted the player on a diy soundboard and it gives a really haunting sound. Better manual speed control can be had by increasing the throw of the crank. As it stands, the crank has too little offset and is fiddly to keep an even rotation.

If you decide to go the way of motorising the unit, be aware that if it jams you need the drive to slip, otherwise the plastic gears can strip.

For speed control a rheostat or pot is not that much better than a hand crank. The load on the music box is not constant - it varies according to the perforations. This can be overcome to a degree by reduction gearing. I would opt for pulleys and rubber-belt drive to get the motor speed down to somewhat higher than you actually need, then reduce the speed to the desired setting electronically. DC motors are best controlled using a PWM supply and a simple supply can be built using a 555 timer as the pulse generator. There are plenty of sites on the web describing how to do this and it's a common technique for simple robotics and model railway control.

It seems not easy to do that. Thanks for your suggestion. I will find the specific way.