A 16 cylinder radial engine with variable pitch propeller.
About this creation
So, this is just a small project I've had built for a while, and I thought I would post up some pictures.
This is a 16 cylinder radial engine with variable pitch propeller. The crank is built using the standard half offset crank pieces that is common on all Technic engines. Each piston is connected to a standard Technic connecting rod. Opposing connecting rods are linked by a thin 1x7 liftarm. There are a total of 8 thin liftarms, with 4 per row of cylinders. The liftarms kinda flop around, but it works very well with no binding. I ran the whole setup during the entire BrickCon event, and everything worked flawlessly (although the motor started to whine at the end).
The variable pitch mechanism is built without the use of a swash plate. Everything is done through gearing. The propeller hub is built like a shaft within a shaft. The outer shaft spins the prop assembly, and the inner shaft changes the blade pitch. Under normal conditions, both shafts are driven by the motor and spin at the same speed. However, when the hand crank on the side is turned, the speed of the inner shaft changes and the result is a change in blade pitch. The differential is the key to the whole system and allows the speed of the inner shaft to vary.
I'm pretty happy with how it turned out. The only problem I have is the number of cylinders. To my knowledge, there was never a 16 cylinder radial engine built. Because of the spark plug firing order, most, if not all, radial engines were built with an odd number of cylinders per row. Radial engines were built with 3, 5, 7, or 9 cylinders per row. Two row engines, like mine, would have been 6, 14, or 18 cylinders. Then there are the engines that have more than 2 rows, like the Wasp Major with 4, or the giant Russian Zvezda radials with 6 or more rows. I think that covers most radial engines, but I'm sure there are exceptions as well as more obscure engines out there.
Anyways, I just thought I'd show a little project I've been working on. I hope to build a plane to go with the engine some time. Sorry about the dark pictures. It was overcast the day I took them.
Excellent design all around. Of all the variable-pitch hub designs I've seen, I like yours best because it's strong and imposes no limits on obtainable pitches. In fact, your hub inspired me to try one of my own. (Theres a photo of it about halfway down on another MOC's page at http://www.mocpages.com/moc.php/383704/). Couldn't quite make out all of your gearing, so I synchronized the prop drive and pitch control shafts with a longitudinal subtractor instead. Works quite well, but I'm also getting low prop speeds due to all the internal friction.
Using the differential and clutch gears to pass two different inputs along the same axle is something that just never gets boring to check out. In this one, it's even used for quite practical purposes. That, and you are the first guy except myself I've ever seen to make use of the half-bush-style teeth ring on the clutch gears... ;)
Very very nice work - a really great technical piece. I had a look at a real one of these last week on top of a skyscraper in Hong Kong (weird place for one to reside I know) - I think it was a 14 cylinder Pratt and Whitney - and it was beautiful. Much like this in fact. 5/5
I like it
October 24, 2011
really nice, i imagine it was hard to make it work