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Old 12-05-2010, 08:18 PM   #131 (permalink)
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Potentially OT but thats a big part of my decision to go hybrid. use the E-motor for what its great at, low end torque and the diesel for what its good at, droning on for hours down the highway.

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Old 12-05-2010, 08:53 PM   #132 (permalink)
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Quote:
Originally Posted by Old Mechanic View Post
The road racing rivalries between Mercedes and Auto Union prior to WW2 are also a fascinating study in competition between in line and horizontally opposed engines.
Minor quibble: The Auto Union cars used V16 engines with a fairly narrow angle (60 degrees, I believe), with a supercharger. They ran a surprisingly low red-line (4000 RPM?) in part so the engines could last a little longer between rebuilds.

I believe the M-B racers were inline engines, though.

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Old 12-05-2010, 09:25 PM   #133 (permalink)
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Quote:
Originally Posted by some_other_dave View Post
Minor quibble: The Auto Union cars used V16 engines with a fairly narrow angle (60 degrees, I believe), with a supercharger. They ran a surprisingly low red-line (4000 RPM?) in part so the engines could last a little longer between rebuilds.

I believe the M-B racers were inline engines, though.

-soD
Yep they were 45 degree engines, thought they were opposed.

I think MB used both inlines and some V8s later.

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Old 12-05-2010, 10:44 PM   #134 (permalink)
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Thanks, Frank.

Quote:
Originally Posted by Frank Lee View Post
Note that back in the old days (100 years ago) engines did have quite low compression ratios, like 4:1. And in conventional engines anyway, the more squeeze you put on the mixture, the more bang you get when it ignites, and the more power it makes. So the traditional relationship has been more C.R.=more power.
So, maybe with a supercharger on the "Blanchard Cycle" engine, with a small pressure tank, so the "mini" intake cycle would be consistently pressurized?

This would make the compression load into a more constant and even drag, and it would allow the large offset to still work for the power stroke, and avoid the problem of having the lack of leverage on the up-stroke.

Having the pressure tank getting precharged with some pressure makes it closer to the way steam engines work.
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Old 12-05-2010, 10:47 PM   #135 (permalink)
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Having the pressure tank getting precharged with some pressure makes it closer to the way steam engines work.
Um... How exactly are you going to go about pre-charging this pressure tank? Where will the required energy come from?
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Old 12-05-2010, 10:58 PM   #136 (permalink)
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The supercharger would pressurize the tank. Obviously this is a loss, but unlike a compression stroke, in the design I proposed a large offset of the cylinder to the crankshaft center, so you would get a much better mechanical leverage and generate torque with the power stroke (instead of bending the crankshaft sideways), but do the offset reduces the power of the up stroke by a similar amount.

So, I cannot avoid the compression loss, but doing it with the supercharger allows it to keep the advantage on the power stroke.

Quote:
Neil I did look over your proposed design in the first few posts. I believe one of the disadvantages of engines that have opposed cylinders like the old air cooled VW was that I have not seen one of that design that was terribly efficient in the first place.
I think disc type valves are an improvement over poppets in theory, but I am not sure if they have the ability to last and be low maintenance.
Okay, the VW and most opposed engines have separate crank pins, whereas this proposed design, the pair of opposed pistons share a crank pin; so one piston pushes the other through it's exhaust stroke.

Why would an opposed piston design be inefficient? Porsche, Ferrari, Subaru, and plenty of others have had successful flat opposed designs?

My biggest concern related to the configuration of the "Blanchard Cycle" engine is odd ball vibration, that would set up a twisting reaction. Even the BMW Boxers have this. This design is not really "flat" in a true sense...

On the wear and tear on disk valves, I was thinking of using both a radial and a thrust plain bearing. Or, another possibility is to have rotating conical valves with ports through them. This would have a large surface area to support the valve against the pressures in the cylinder, but still be a low-drag rotating design.
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Old 12-05-2010, 11:07 PM   #137 (permalink)
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What steady-state pressure will your tank be pressurized to? This question relates to the required volumetric expansion ratio you will need in order to extract useful work from your motor.

I also assume you're going to use gasoline or E10 or diesel fuel for this motor?
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Old 12-05-2010, 11:21 PM   #138 (permalink)
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This is a schematic design exercise -- the exact specifics are a long way off. Do you think a small turbocharger would be better than a supercharger? Is the pressure tank unnecessary?

Keeping in mind that piston engines were invented for steam power, and adapted for gasoline -- steam has a (more or less) constant back pressure, so the pressure in the cylinder is maintained all the way to the bottom of the stroke. Whereas, ignited fuel in a much shorter expansion time, and since it start very near TDC, much of the peak pressure is "wasted" in bending the crankshaft sideways, rather than developing torque.

I think I am assuming some sort of volatile fuel like gasoline or alcohol. Diesel would probably not work in this design.
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Old 12-06-2010, 12:11 AM   #139 (permalink)
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Scuderi Engine - Wikipedia, the free encyclopedia

This might be along the lines of your thinking Neil.

Most steam engines used either two operational tactics when they evolved.

Multiple cylinders of increasing size that extracted more energy out of the steam like the double , triple and even quadruple expansion types.

The second tactic was to actually shut off the input of steam and allow the expansion to continue to get better efficiency.

The titanic had a turbine and multiple expansion engines because the multiple expansion types were more efficient and economical.

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Old 12-06-2010, 12:16 AM   #140 (permalink)
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I think if you look through the EPA ratings of the various opposed designs that have been available here the mileages of those types seem to be lower than other types.

A lot of people seem to have become advocates of the OPOC engine but it like other engines with large reciprocating masses will see losses climb dramatically when they are operated at higher RPMs.

Bill Lear of Lear Jet fame dumped a fortune into trying to compete at Indy with a steam powered racer.

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