Create gear boxes with a laser cutter

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This is a sub project of ( Goal of the project is to create generators for gear boxes that can be used for transmitting power in real projects.

Do we really need more gear boxes? Isn't the internet already full of nice looking gear trains from the simple gear generator up to the 6 gear automatic transmission?

Well yes, but most of them do not fit the bill of this project: Create something that can be actually used and is not just a display model and can be cut out quickly with a laser cutter.

Design Goals

  • Make the gear box work with materials that can be cut with a CO2 laser.
  • Make a motor part of the design. The shaft of the motor should carry the first gear
  • Have a closed housing to allow lubrication with grease and avoid stuff getting into the moving parts
  • Take into account that with increasing reduction torque increases also. Make later gears in the gear train stronger
  • Provide proper bearings - at least for the output shaft. Allow hooking up belt drives or wheels directly to the gear box without a coupling to a supported drive shaft.
  • Have parametric generators. Generate a gear box with the desired reduction. Have multiple designs spanning the range of gear ratios if necessary.

Design Patterns

As laser cutting is pretty much 2D we need means to create 3D structures. Besides the finger joints for joining sheets in a 90 degree angle which is already extensively used in the gear boxes will make use of sheets glued together on top of each other. This allows creating different thicknesses from one type of sheet material and stud holes for shafts and bearings. To allow precise glue up small parts like gears with get holes for alignment pins. Bigger parts will get slots on the outside that other sheets or laser cut clamps fit into and so force the layers into alignment.

As the box will be made from relatively soft materials the output shaft will be supported by ball bearings which not only reduce friction but also increase the area supporting the forces.

I want to try if it is possible to get away with using normal machine screws as output shafts. Hex bolts should make it easy to transfer the torque. It is still unclear if they really fit a ball bearing properly. They also create the problem of mounting them as they end within the driving gear.

  • Cover plate

    Florian Festi04/30/2017 at 21:55 0 comments

    Another issue that needs solving is putting things together - properly. For now there are no lids in that are suited for a gear box. The attitude has been avoiding screws. Most things are just pressed/hammered together with finger joints which are pretty hard to get apart again. For a gear box we want something that we can screw on. Especially as this lid is probably going to hold the shafts in place.

    One way would be using some two layer lid - basically like the RoundedBox. The lower layer firmly attached with finger joints and the upper layer glued to the cut out in the first layer. This creates a lip giving extra stability. May be the first layer could also be attached with finger joint holes creating a ridge around the top in which the second layer fits in.

    This two layer approach also allows for stud hole for the intermediate shafts.

  • Spur gear box

    Florian Festi04/30/2017 at 21:44 0 comments

    Second design to try is a "simple" spur gear box. This will be based on a simple box based on finger joints. There already exists a generator on for quite a while. But it is even further from being usable that the planetary gear box. What's wrong with it basically translates one to one into the projects design goals...

    First scribbling on paper suggests that it will be difficult to come up with one universal design. So this will probably end up as several different generators each for the number of stages from one to probably 4. This should cover the range from 2:1 to 1000:1.

    I am still at beginning with this design. One thing I want to try is having a hex bolt in the last gear and also fit a ball bearing within the same gear in another layer. This should allow supporting the output shaft on the bottom side and so having the full height of the gear box as support (with a second bearing on the top end).

    It very clear that the gears need different strength and though thickness for the different stages. Need to check out if I can automatically adjust the modulus of the gears. May be squeezing even bigger reduction out of the earlier gears. Lots of stuff to try out...

  • Planetary gear box

    Florian Festi04/30/2017 at 21:27 0 comments

    This is the first design I am trying out. There already is a generator alredy online but it is just not there yet.

    The gear box will be build from laminated layers starting at the bottom with the plate for mounting the motor. On top of that are rings and ring gears housing the planet carrier made out of two disks connected with walls by finger joints.

    There will be two possible top sections: One for driving a belt which has a pulley directly on the planet carrier that is supported on top by a ball bearing:

    The second variant will have a plate with one or two bearing that the drive shaft passes through. My idea is to use a hex bolt who's head is pressed into the planet carrier.

    It should be easy to create multiple stage gear boxes by just adding more ring gears and dropping in planet carriers with a sun gear on top.

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