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Radial Engine with Drive-Cam

Efficiency and smoothness
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A while back I posted an idea for a Boxer Radial engine which was surprisingly well liked. I like the idea myself, but it got me wondering if it was possible to make a one-layer radial smooth and efficient, as they have a reputation for being the opposite.

Well some engine companies are experimenting with camshafts instead of crankshafts to bring the pistons up because they are more efficient and reduce side loading. But none to my knowledge have worked with radial engines.

My idea is actually quite simple. There would be a 6-cylinder radial engine with cylinders evenly spaced, meaning for each cylinder there would be one 180 degrees apart. But unlike the crankshafts of radial engines which allow only one cylinder to be at TDC and only one at BDC at a time, this would have a symmetrical cam lobe to make it identical to a boxer configuration. But here's the kick: the cam lobe on which the pistons are moved up and down is fixed in place, and the engine rotates around it. To keep the connecting rods attached, there are two rubber wheels with a few millimeters gap between them that fit into groves in the lobe. The wheel up top is pushed up by the cam, and the wheel on the bottom is pulled down.

I'll rephrase a few things and add an illustration later.

acurafan07, Dec 13 2007

So pretty much the same as this without the weird valve system Radial_2fRotary_20E...h_20Rotary_20Valves
[discontinuuity, Dec 13 2007]

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       Congratulations on reaching idea post #50!   

       Just too bad that nearly forty of them are all the same thing...
lurch, Dec 13 2007
  

       [lurch] thanks, I guess. I don't quite follow you on how they're "almost the same thing", seeing as how they are about different things. It might be true there are a whole lot of engine ideas but, hey, you post what you know. They seem to be well liked too.   

       And I just deleted an un-workable idea, soon to be replaced with a (hopefully improved) one. For now, down to 49 again.   

       [rasberry re-tart] that seems to be about the valvetrain whereas this is about replacing the crankshaft with a camshaft. I know in that idea the engine rotates like this, but that is often the case in old radial engines. My idea says nothing about valves. But I have bunned that idea before, and I think it would work well on this engine.
acurafan07, Dec 13 2007
  

       lurch must not be that machanically inclinded.   

       All your ideas are really "unique"   

       Always makes me think and build it in my mind.   

       Although, I must admit, I can always tell from the title that the idea was posted by you   

       As to this idea, oookay. . , So a radial revtec huh?
evilpenguin, Dec 13 2007
  

       Thank you for the kind words.   

       As to the question, kind of. Only unlike the revetec which has a complicated drive system including two counter-rotating cams, this has only one and it's stationary. I guess the second part of the idea is that it would be a boxer configuration which is impossible to do with a crankshaft and only one layer in a radial.
acurafan07, Dec 13 2007
  

       The best thing about using a stationary cam with a double-action follower, is that you can 'tune' the shape of the cam to give optimum performance as the pushrod travels around it. I don't know enough about engines to suggest shape changes, but particularly the profile at/after ignition could make better use of the explosion (rather than the mechanical dis-advantage of the crank/pushrod near TDC).
neutrinos_shadow, Dec 13 2007
  

       //lurch must not be that machanically inclinded// <giggle>
I got my first car at age 13... and had to rebuild the engine (4 pistons were melted) before I could drive. I had that engine out on the bench 9 times before I got my driver's license.
However, in the process I said a lot of things I'm glad my mommy didn't hear and I decided that fixing engines wasn't the *only* thing I would do in my life.
  

       The "all the same thing" part of my comment is just... well, I can think up at least 100 different things that I could do with LEDs in the back window of a car. Should I post them all? How far do you have do go before someone decides that, like electricity-producing gym equipment, we have seen enough variations on "another way to arrange the cylinders on an internal combustion engine" to turn it into a cause for an [m-f-d] tag?   

       I'm not suggesting that it should be such. But maybe, maybe... I dunno. New year's resolution of one a month?
lurch, Dec 13 2007
  

       [neutrinos_shadow]: actually the idea is about the pistons and connecting rods being driven by the drive cam, not the valvetrain.   

       [lurch]: Well like I said, I post on what I know. My ideas aren't only for how to arrange cylinders, in fact I believe only this and one other are about that. If I see an advantage in a different design of something, I post it. If I see an opportunately to implement an already-baked concept on something else that would work well with it, I post it. Seems to be a good enough formula for me. The thing about engines is that they just so happen to be the heart of whatever it is they propel. So unlike 100 different ideas for LEDs in a window, engine ideas are generally useful.   

       Re-building an engine at 13 is impressive, and not something I would claim to have been able to have done.
acurafan07, Dec 13 2007
  

       Yes, I knew about your age. And I'm pretty sure you could have handled that engine (351 Cleveland), and if you had that engine, couldn't drive, and had a shop like my dad's, you would probably have had it apart more often than I did.
lurch, Dec 13 2007
  

       //pistons and connecting rods... valvetrain//
I know - I mean modifying the shape of the drive cam; it doesn't have to be a perfect ellipse, and changing the shape at 'TDC' could improve the transfer of energy from explosion to driveshaft. Cam profile design is tricky, but can allow clever things to happen (eg. some camera zoom lenses use carefully shaped face cams to shift the elements inside in precise ways).
neutrinos_shadow, Dec 13 2007
  

       Oh sorry I guess I missunderstood. And you're right it probably shouldn't be a perfect ellipse.
acurafan07, Dec 13 2007
  
      
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