Piston engine torque?

[sstearns2]

Scott, You're correct when you say that the slow speed is related to the need to avoid a reduction unit. I'll admit that it has been a while since I checked; but the last time I looked, a Rotax (either two or four stroke) has a TBO of less than five hundred hours. To me, that is a longevity problem!

According to Diamond Aircrafts website the TBO for the turbocharged 914 is 1000 hours. The NA 912 is considerably higher. Anyone out there work on 4 stroke rotax's care to comment on their longevity?

In fact, high reving recip engines do suffer longevity problems when compared to low rpm engines. A F1 engine turns somewhere around 19K RPM, and makes a bunch of power, but I wouldn't want to hang one on a Kingaire even though it makes enough power to pull said Kingaire.

Well you could goto a top fuel drag race and see engines that run at 7 or 8000 rpm that need an overhaul after running for 10 seconds.

How about my honda engine that turns 4000 rpm on the highway everyday? By your logic the big V-8 turning 2000 rpm next to me should last way longer. Does it? The honda engine long reputation of going for well over 150,000 miles. Does the big V-8 go for well over 300K?

My point is that if the engine is designed to operate at high RPM then it's not a problem.

Scott

 

[enigma]

My point is that if the engine is designed to operate at high RPM then it's not a problem.

Scott

We agree on that.

However, the high rpm engine will require either more weight, or more expensive materials, and it will require a complicated PSRU. I just wrote a long rant on the design requirements of a PSRU and lost it somehow. (I'm stuck with a low speed internet connection, and somehow I got kicked off while I was typing) I don't feel like retyping, maybe tomorrow.

BTW, I just happened to get a block of reserve so I don't have anything better to do than argue on the internet. Nothing personal!

enigma

 

[TonyC]

(I'm stuck with a low speed internet connection, and somehow I got kicked off while I was typing)

When I was in those shoes, I got in the habit of CTRL+A, CTRL+C before I ever hit "Submit Reply" or "Preview Post." That way it'd be saved on the clipboard if the connection hiccuped. All was well again with a little CTRL+V.





For Pete's sake, Man, get yourself some DSL or Cable ! !





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[enigma]

When I was in those shoes, I got in the habit of CTRL+A, CTRL+C before I ever hit "Submit Reply" or "Preview Post." That way it'd be saved on the clipboard if the connection hiccuped. All was well again with a little CTRL+V.





For Pete's sake, Man, get yourself some DSL or Cable ! !





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Thanks for the tip.

Crashpad woes my friend, I'm just glad that no one else is here and I can get away with hogging the phone line

enigma

 

[gfvalvo]

Well, you can take your pick:

1. Airplane engines turn at low RPM because props need to turn slowly and direct drive is simpler than gear reduction (and no power is lost to said reduction).



2. Airplane engines turn slowly because that is one way to make them last a long time.



Both are true.

How about my honda engine that turns 4000 rpm on the highway everyday?

Running down the highway at 65 MPH your Honda’s engine is probably developing less than 20% of its maximum power. An airplane engine spends almost its entire life running at somewhere between 60% and 75% of its maximum power. That’s a HUGE difference. Try taking one of those light-weight, high-RPM, high-power motorcycle engines and running it for 2000 hours at 70% maximum power. Watch out for sudden and violent self-disassembly! This leads to:



3. Airplane engines are built like brick sh*t houses relative to their maximum rated output power. A major reason is so they’ll last a long time.



Granted, they are, in fact, producing a lot of torque. But that is so the can develop a lot of POWER while running at low RPM. This brings us nicely back to #1 ablove.

 

[enigma]

When I was in those shoes, I got in the habit of CTRL+A, CTRL+C before I ever hit "Submit Reply" or "Preview Post." That way it'd be saved on the clipboard if the connection hiccuped. All was well again with a little CTRL+V.





For Pete's sake, Man, get yourself some DSL or Cable ! !





.

Tony, your PM inbox is full.

 

[TonyC]

Tony, your PM inbox is full.

It gets full?!?!/ Hmmmm... time for a little housekeeping, I reckon



brb