This is the first of two attempts at motorising MishaT's Nautilus gear set. (My second is here: http://www.thingiverse.com/thing:176585) In the past, I have used a rather expensive although very solid, geared DC motor for projects like this but have never had a go at 'hacking' a servo motor to achieve the same thing - low RPM, low voltage and a decent amount of torque.
The problem with using a servo motor of course, as well as doing the hacking, is that there is no immediately obvious way of hooking up the drive shaft to turn an axle. This requires some creative thinking which is why this project is still "work in progress" - there will be better ways of coupling the motor to the M3 axle bolt which I have used no doubt so the challenge is on!
The motor is run from a standard 1.5V battery as shown in the video. http://youtu.be/HtOLFmOW6Bc It is not quiet so maybe enclosing this thing in a box would be a good idea. (Please excuse the quality of the video - I will turn the radio off next time).
The choice of servo by the way was quite arbitrary - it was one of two spares I had in my work box, having used one of a packet of three for an Eggbot derivative over the summer.
Rather than go through a set of instructions, I will provide details of what each of the STL files are for and let you, the creative maker go and get on with it. Saying that, if you have any questions, please leave a comment and I will respond as soon as I can.
This is a 3mm panel onto which the gears are mounted. It has an odd shaped hole to take the profile of the servo motor which I used, a Turnigy TGY-1800A. The hole is a tight, interference fit on purpose as I did not use any screws (or glue) to hold the motor in place.
Print two of these and slot them onto the display panel above. These are feet to keep the panel upright - or should I say, tilted as the panel sits at an angle of 15 degrees.
ServoConnector_Top_1 and ServoConnector_Base_1
These fit together, trapping one of the horns which come with the servo motor. There are three locating pins/holes which might prove tricky to print - I suggest you print these parts alongside others and switch on any cooling fans which you have in order to stop the pins falling over. (I had to clean out the three holes using a 1.5mm drill once the bottom had come off the printer). Glue the two halves together once the horn has been trapped - I don't particularly like using glue and trapping pieces in place but it was difficult (for me) to come up with anything different). Once the servo connector parts have been secured together, The assembly is pushed onto the servo drive and secured using the small screw which comes with the servo motor. An M3 nylon nut is then glued in place into the top ready to accommodate the M3 bolt which forms the drive shaft for one of the gears.
This is a rework of MishaT's original file. You need two of these. Fit M3 screws and washers through each gear each of which have a trapped M3 nut on the other side. One of the gears then screws into the servo coupler and the second through the hole in the display panel onto a washer and M3 nylon nut.
The Servo Hack
The principle here is to disconnect the electronics inside the servo motor from its DC motor, remove what is used to limit the movement of the DC motor shaft and then connect wires to the DC motor to power it from a 1.5V battery. Specifics will vary from motor to motor so I suggest and internet search using terms such as "servo motor hack".