Engines > Your Own Design

The Modular Tower Engine - a new, experimental design

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awake:
With some fear and trepidation, I am introducing a model engine that I have designed, and which I am about half-way through building. The fear, of course, is that I have no idea yet if it will work! Attached are some CAD mockups of what it will look like. The first three pictures provide different angles on the fully assembled engine; the last picture has the ignition components removed so that you can see the details of the crank and cam gearing.

It may not be obvious at this point, but this design was inspired by Longboy's Side Shafter and Super Tee - though I hasten to say that he is not responsible for the gaffes and mistakes that I am no doubt making! The key element of Longboy's designs are the connection of multiple cylinders through gears rather than through a shared crankshaft. You may be thinking, "but this "modular tower" is a single cylinder design." Quite right ... but you may note that the design includes the placement of holes and features that will allow a second cylinder to be placed at the other end of the tower - at which point, the tower will be turned 90 degrees in a boxer configuration, but the cranks will be connected to each other via gearing with the cam shaft. Now you know why I call it the "modular" tower engine!

One major feature of the design is also the primary source of my fear and uncertainty about whether it will actually work: The main shaft, i.e. the shaft on which the flywheel resides, is actually the cam shaft rather than either of the crank shafts. I've never seen this done ... but I can't think of a reason it won't work. That may simply reflect my ignorance and inexperience! One issue could be the piston having to complete all four cycles for one revolution of the flywheel ... but then again, this is also true of the various Atkinson designs. I know the "Atkinson differential" is a beast to get running, but from what I can tell the "Atkinson cycle" seems to be reasonably easy to get running.

I welcome your comments and feedback, disparaging or encouraging alike! Stay tuned for the build ... I will provide pictures and plans as they become available.

crueby:
Very interesting concept, hope it comes together well!

Jasonb:
May need a heavier flywheel than would be usual for the size of engine a sit won't be turning as fast, other than that it's standard mechanicals so should run.

awake:
Here's the first piece of the engine - the "tower," which functions as the foundation for everything else. Since there is nothing out of the ordinary in any of this, I did not take any pictures while machining - just the finished product.

A couple of notes. First, note that this is fully symmetrical - both ends, both sides, both faces are drilled/tapped/bored exactly the same way. This will allow the second cylinder to be added later one. Second, note that the bores are made to take the common-as-dirt 608 "skateboard" bearings - these will be used throughout to support the crank shaft and cam shaft ... which means that both shafts will be 8mm diameter.

awake:

--- Quote from: Jasonb on July 02, 2020, 08:11:10 AM ---May need a heavier flywheel than would be usual for the size of engine a sit won't be turning as fast, other than that it's standard mechanicals so should run.

--- End quote ---

Since the flywheel is under discussion, I'll go ahead and jump ahead to show that next. The pictures below show the finished flywheel and its tapered locking hub. The weight of the finished flywheel together with hub and screws comes out to 2.05 lbs. / 930g.

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