Straight Line Reciprocating Engine...

[potteryshard]

Forgive me all for posting this in all probability hare-brained notion; it is far out of my speciality, not that I would make any claim to know of what I speak even in that venue.

Nonetheless, I'd like to ask if any potential exists for this notion?

Please see the attached .PDF outlining my thoughts.

 

[TDIMeister]

That's an embodiment of a Cardan or Cardano motion mechanism. There have been dozens of patents over the years filed on this idea (go to google.com/patents and search variations of the keywords "cardan motion mechanism engine").

A PhD thesis from Finland has been written on the subject:

https://oa.doria.fi/bitstream/handle/10024/36120/isbn9789522145345.pdf

 

[BrianPetersen]

Way more parts than a normal crankshaft and con-rod. Lots more potential for failure, and it doesn't look anywhere near as strong.

 

[potteryshard]

In reading the thesis it appears that considerable potential does exist; I didn't realize that this was called a Cardan mechanism, but knew that considerable work had been done in this arena. Becasue of the necessity of the rod to pass through the crank center, the usual arrangement is of a single overhung gear/crank.

There are of course more parts involved; that may not be a detriment if the aggregate mass and expense of those many parts is comparable to the fewer but more massive and expensive components. A multitude of rotating parts may also be a good trade off if the mass of the reciprocating parts may be reduced and balancing shafts eliminated.

As discussed in the thesis, overall reliability and smoothness will be dependent upon the accurate fit and minimal clearance of the gearsets. In this case, where the gearsets are not crank-mounted, but exist as free-floating assemblies, it may be possible to mount the locator gears on eccentrics so that clearance may be adjusted without the use of high-precision gears.

I also don't see this mechanism as terribly fragile; yes absorbing piston pressure through the medium of a gear leaves me uncomfortable; but, because every individual crank is double-ended, and because those crank gears each engage at two (or more) points it would seem that a number of load paths exist to spread out those impulses, and that engineering in reliability shouldn't be insurmountable.

I make no claims that this approach is best or even better; I suggest only that it seems worthy of some thought. I brought this forward simply because progress seems require re-examintion of our basic assumptions periodically.

 

[TDIMeister]

BMW holds a few patents on engine designs using this type of mechanism. Search under the inventor's name, Gert Fischer.

 

[SMOKEY44211]

Check out Bourke engine. That one used scotch yoke to transfer motion. Made a big splash back in the 1950's. Never made it to mainsteam production in any significant volume. I mention it only that piston to crank movement is the same as the version you are asking about.-----Phil

 

[dicer]

The basic mechanism of the standard reciprocating engine, can not be improved on. Its the simplest and most durable design there is for that application. Many ideas have come and gone. Where you think you are eliminating one problem area, another crops up. Most all the supposed "new" designs are lacking some where, either added heat losses, or added parasitic losses do to added monkey motion <-- new tech talk, or gear sets, bearing surfaces etc. All claims for these new designs are just that, claims. Never seems to be a real time working model of any of them. No dyno numbers ever posted or video's of the dyno runs showing the numbers either. All most of these new designs are is talk. And hype.

 

[WhizzMan]

James Watt had to use a sun and planet technology because the crank and rod were patented by someone else. Watt in response came up with quite a few alternatives and patented those. After the patent on the crank and rod expired, everyone in steam engines went to that, until the turbine was invented. I think that the chance on anyone coming up with an engine that's not been tried, patented and shown to fail in practice are rather small. The only more efficient ways to burn fuel so far have been the turbine and the fuel cell. These use an electric motor to do the final conversion to mechanical energy.

 

[gruntguru]

Yes, both of them (except the turbine of course).

Engineering is the art of creating things you need, from things you can get.

 

[tonMech]

This another weird contraption using gears instead of a crankshaft: Quite different, though.

http://www.gearoscillator.com

 

[factsb4pride]

http://www.eng-tips.com/viewthread.cfm?qid=243063&page=15

here is a thread that is related to your questions, though for some strange reason the thread was closed...

 

[JSteve2]

@dicer: I think the basic design of the IC engine will, at some point, be significantly improved upon. It will probably occur because something that is viewed as a constraint today will no longer be a constraint someday. Materials, computerization, or some other breakthrough will change something that has been assumed for a long time. However, I tend to agree that we're not going to simply re-arrange the same mechanical parts we've been looking at for a long time and suddenly have a huge advance. But I have to think if you fast forward 100 years the ICE will still be here but some things will be significantly improved.

To the OP - I think it's worthwhile to keep looking. We may find something useful, even out of something we've looked at before. There may be a reason that something old works now when it didn't before.

 

[patprimmer]

Cost of precision or complex machining and new material will be the controlling factors in my view. Also advances in control systems.

Regards
Pat
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