Although my first radial engine model was successful for what it turned out to be, I decided to build another one. It’s much more reliable than the first, although it doesn’t feature CNC-router-cut MDF gears.
I did make most of this on a CNC router, but for the most part it could have been done with conventional tools. The MDF “flywheel” would have been difficult without access to computer controlled machining as well as the polycarbonate support that it’s glued/screwed to. Unlike the first model, a gear-reduced motor is directly attached to the bottom piece of 1/4 inch MDF.
To support the flywheel seen in the picture to the right, a piece of scrap polycarbonate (roughly 3/8 inch thick) was used as a shaft collar. The top was tapped for two 4-40 screws to attach the flywheel to, and the side was tapped for another 4-40 screw to allow it to be locked against the motor shaft. Once assembled, only one of the top screws was used with Gorilla glue to lock everything down.
Here’s a list of the components you’ll need. All the wooden parts were cut out of MDF with my 7 x 12 ZTW CNC router.
- Flywheel (1 x 1/4 inch MDF)
- Base (1 x 1/4 inch MDF)
- “Pistons” (4 x 1/4 inch MDF)
- Blocks to restrict piston’s movement (4 x 1/2 inch MDF -each slot 1/4 inch higher than the next)
- Shaft collar or makeshift substitute as described above
- Drive motor (I used this motor from Allelectronics)
- 1/4 – 20 bolt (1 1/2 – 2″ length. Smooth towards top of shaft if possible)
- 1/4 – 20 nut to lock bolt to flywheel
- 4-40 screws (1/2 inch length is ideal, but different sizes would work)
Cut all these parts out from the included .dxf files, then 1/4 – 20 tap the MDF on the flywheel. The 1/2 inch blocks used to restrict the “pistons” need to be glued to the center of each of the four sides.
The base has some extra holes that may prove useful, but delete them if you want. Also, there is no “shaft collar” drawing included. Use 1/4 inch MDF for all parts except for the “Radial Base.” Once everything’s cut out, assemble as discussed earlier. Here are the drawings:
Have fun! With some creativity, this project can be done with manual tools, so give it a shot! Be sure to send me some photos if you do build one of these. Also, if you need access to DXF files, but don’t have AutoCAD, just download Draftsight for free! (or check out my review of it here). As with the first engine model, this isn’t really what I was trying to make. It may still turn into something else, so be sure to check jcopro.net obsessively until then or just subscribe to the RSS feed!
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