REFLECTOR: Engine Selection

[Al Gietzen]

Just a couple of comments on this power, efficiency and speed thing.  Torque
is a measure of force; HP is a measure of work; force times time - or acting
through a distance.  So it is the HP that does the job.  Hp is simply torque
times rpm.  You can have high torque a lower rpm but if it gives you the
same HP you've gained nothing; unless the prop was more efficient at lower
rpm.  I thought this was true as well - until I studied some prop
performance charts and found it wasn't true.

 

160; 180; or 200hp - IMHO, these are all low for a fixed gear 173.  Getting
161 mph at 5500 ft with 160 hp translates to 173 mph with 200hp (remember;
speed goes as the cube root of power).  That's 153 kts.  Hardly impressive.

 

Al

 

Subject: Re: REFLECTOR: Engine Selection

 

Plenty of power. He's got a 173 RG. The Velocity was originally designed for
160 hp.  The DH180A4 is 180 hp up to 18,000 feet. The DH200A4 is 200 hp at
18,000 ft. Plus, the diesel has better torque at lower RPMs than a Lycoming,
and propellers are more efficient at lower RPMs. Plus it weighs less if you
take into account that it is 30% more fuel efficient, so you don't need to
carry as much fuel weight to get the same range. A DH160V4 is in the
factory's test airplane.  With the 160 hp engine they clocked it at 202 mph
at 15,500 feet, and 161 mph at 5,500 feet. And that is with a fixed pitch
propeller.

 

The DeltaHawk has half the moving parts of a Lycoming, no spark ignition to
interfere with the radios, and burns readily available and slightly cheaper
Jet A.  It is much smoother because it's a two-stroke. Plus, since the
DeltaHawk test platform is a Velocity Std RG, the firewall foreward package
is pre-designed.

 

No, I don't own stock in the company. Just excited about the first
significant improvement in general aviation powerplants in 50 years.

 

Doug Holub

Std Top Door, 50% done, 80% to go

----- Original Message ----- 

From: NMFlyer1 at aol.com 

To: reflector at tvbf.org 

Sent: Tuesday, June 15, 2004 9:18 PM

Subject: Re: REFLECTOR: Engine Selection

 

nice idea Doug... but not enough power scotty 


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