Metrication advocates are at it again

HAhaha! That's a keeper.

Ed Huntress

yes, the French government should require it.

Here's a hint for you, Mark. You talked about a turbocharger using the "waste energy" of the exhaust gases as against the supercharger drawing power from the engine. You're wrong. No free lunch here.

There is waste energy in the exhaust gases, but it's in the form of heat, not pressure. There is very little back pressure in an aviation engine. Add a turbocharger to that system and you'll increase the back pressure, which will do two things. One, it will make the scavenging of the cylinder less complete, which will reduce intake of the fresh charge and thus the power of the engine. Two, the increased back pressure will act against the piston on the exhaust stroke, which will directly reduce the power output of the engine. If it takes

100 horsepower to run a supercharger on an engine, you will reduce the power output of that engine by at least 100 horsepower whether you drive that supercharger from the crankshaft or through an exhaust turbine. And then, with the exhaust turbine, you'll lose some more power due to less exhaust scavenging.

You are right about aviation engines having more complex supercharging requirements due to changes in barometric pressure. That's why you'll find hydraulic or other variable drives on aviation supercharger systems. Plus dump valves, which I believe you'll find on most of the turbo systems as well.

John Martin

Turbochargers typically are 30% to 50% more efficient than mechanically driven superchargers, in terms of piston horsepower/shaft-output power. The scavenging and back pressure (pumping pressure) losses are much less than the mechanical power required to drive a supercharger on the same engine that produces equal net power.

By every measure, ranging from fuel consumed to peak piston pressure, turbochargers produce more power with less engine stress and less fuel waste.

There are some studies from MIT's engine labs that lay it all out in detail.

Ed Huntress

$2 a month per line. That's one of the reasons I use rotary phones. The other is that they tend to be more robust against lightning damage.

Gary

well the trade off is it takes forever to dial a 10 digit number :^(

T> >Does your phone company actually charge more for touchtone dialing? >

If I was a telemarketer, I might care.

Gary

The telemarketers wouldn't care, Gary, because almost none of them do any dialing.

Their computer does the dialing, you answer, and IF there happens to be a telemarketer free he'll pitch you. If not, the computer will hang up on you. To me, that stinks.

And I'm a marketing consultant whose clients mail out unsolicited catalogs and do some limited outbound telemarketing. No computer dialing and hangups, though.

John Martin

They're only units of measurement. They don't really mean anything. Your units are just as arbitrary as anyone elses. Who cares. Besides, boneheads like you don't seem to mind using thousanths of an inch, but thousanths of anything else is metric crap....you're a real professor...

incremental

As one advocate of the Imperial system once said "If God had intended us to us a metric system he would have given us 10 fingers...oh!"

When I did my engineering Australia was in the change-over period so we were taught in both units and examined in both units. In the exams, you could not just pick questions that were in your preferred units.

I don't suppose anybody has over $1000 invested in standard measuring products, calipers, mics, etc. I would hesitate to switch just because of the personal cost. Specially seeing so many jobs (that don't belong to us) is being sent overseas

Russ Wizinsky

"Patrick Gomolchuk" wrote in news:0ryRb.19222$P51.13955@clgrps12:

Having used the metric system for the past 13 years almost exclusively here in the US, I find it much easier to use than the imperial system. It is much more simple to convert between units.