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  #1  
Old 11-24-2007, 06:03 PM
Mark7986 Mark7986 is offline
 
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Question DeltaHawk Diesel Engines

Does anybody know anything about the DeltaHawk engines. I'm just starting an RV 7 and they say firewall forward is almost ready. Sound like a good alternative to 100LL.

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  #2  
Old 11-24-2007, 07:02 PM
Pirkka Pirkka is offline
 
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Quote:
Originally Posted by Mark7986 View Post
Does anybody know anything about the DeltaHawk engines. I'm just starting an RV 7 and they say firewall forward is almost ready. Sound like a good alternative to 100LL.
I guess they did say this at their web page about a year ago. Do you have another source?
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  #3  
Old 11-24-2007, 10:14 PM
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Tandem46 Tandem46 is offline
 
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Plenty of past discussion on this engine. Just go to RV Firewall Fwd, then Alternative engines. Below are some of the past threads. They're kinda out of date due to slow (but steady) progress at DeltaHawk.

http://www.vansairforce.com/communit...ad.php?t=16197

http://www.vansairforce.com/communit...read.php?t=310


http://www.vansairforce.com/communit...ead.php?t=6752
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  #4  
Old 11-25-2007, 08:04 AM
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Quote:
Originally Posted by tobinbasford View Post
.......slow (but steady) progress at DeltaHawk.
what's your source on this? company PR? or do you know something definitive?

DH has been "moving forward" for longer than it took to land on the moon (literally). This is a classic case of an under-managed, under-funded company trying to eek out a path as a mom&pop in a "3-ultra" environment (ultra capitial-intensive, ultra high-risk, ultra low-volume).

One need look no further than the challenges experienced by Eggenfellner and Thielert using proven engines designed, built and supported by $multibillion manufacturers with millions of engines in the field. The experience of DeltaHawk illustrates the monumental challenge of giving birth to a clean-sheet engine design, let alone in an unforgiving environment such as aviation.

DH is proof that "simple" is anything but.

That being said, I am hopeful that someone will resuce the company from itself .... despite the inherently nasty vibration profiles of V4 configuration, the concept is the most viable among all new purpose-built powerplants in light recip aviation.

As for DH being ready for installation on RV's or anything else, steer clear. There are many years of testing ahead....assuming they make it that far. DH will surely fade into history (soon) unless it is acquired by a large well-funded company familiar with the peculiar trevails of aviation. Until owners/management of DH come to grips with the situation, DH will languish until it dies from starvation of capital and loss of credibility, one of which is curable, the other is not.
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  #5  
Old 11-25-2007, 08:10 AM
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Ron Lee Ron Lee is offline
 
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Default Don't be the first

Personally I would wait until a company has a proven track record.
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  #6  
Old 11-25-2007, 12:25 PM
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pierre smith pierre smith is offline
 
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Default A friend of mine...

.......who has a Zenith 801 almost built has waited over 2 1/2 years for his Deltahawk.
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  #7  
Old 11-25-2007, 01:19 PM
1:1 Scale 1:1 Scale is offline
 
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Quote:
Originally Posted by bumblebee View Post
despite the inherently nasty vibration profiles of V4 configuration.....
Can you elaborate on this please? A 4 cylinder, two stroke, V-4 with the DH's crank will have a combustion event every 90*, as opposed to a flat four 4 stroke's every 180*. Seems it should run relatively smooth....
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  #8  
Old 11-25-2007, 02:28 PM
SvingenB SvingenB is offline
 
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Originally Posted by 1:1 Scale View Post
Can you elaborate on this please? A 4 cylinder, two stroke, V-4 with the DH's crank will have a combustion event every 90*, as opposed to a flat four 4 stroke's every 180*. Seems it should run relatively smooth....
I would think so too, maybe? A two stroke diesel is the smoothest running engine there is, but is a V-4 dynamically balanced like a V-6?
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  #9  
Old 11-25-2007, 02:54 PM
flyvans.com flyvans.com is offline
 
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osh wasn't much of a reassurance either, didn't look like they wanted to sell many engines to experimentals, really... pretty unfriendly folks at their booth.
guess the military uav market means less risk and probably more bucks...
too bad that such a nice concept simply seems to drag aloooong...

my 20cts,

bernie
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  #10  
Old 11-25-2007, 04:06 PM
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bumblebee bumblebee is offline
 
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Quote:
Originally Posted by 1:1 Scale View Post
Can you elaborate on this please? A 4 cylinder, two stroke, V-4 with the DH's crank will have a combustion event every 90*, as opposed to a flat four 4 stroke's every 180*. Seems it should run relatively smooth....
vibration in recip engines is very complex and not "obvious".....here's a Cliff Notes version of some issues.

-- a piston on a crank is similar to an unbalanced washing machine.
-- as the crank rotates, the CG of the piston/pin/counterweight combination is not centered on the crank and the CG path is not circular .
-- H engines (boxers) have mostly self-canceling "washing machines" BUT they are not perfectly balanced until H8
-- H engines tend to "rock" from side to side (shake your head "no")
-- V engines are statically unbalanced until 90-degree V8 (4x90) BUT a 90-V8 is still dynamically unbalanced due to unequal "mass lengths" between "top" and "bottom" positions (TDC and BDC).
-- with the exception of certain V12's, all "V" engines have centers of rotational mass that are not on the centerline of the crank

V4's are horrible....surpassed only by the infamous Harley single-pin V2.

on a scale of 1-10 (1 being harsh) the following engines are

V2 (single-pin/harley) = 1
1-cyl (lawnmower, etc.) = 2
V4 (90*) = 2
I4 (w/o balance shafts) = 3
V6 (90*) (w/o balance shafts) = 4
V6 (72*) (w/o balance shafts) = 5
single row radial = 6
H4 (lycoming, subie, etc.) = 6
V8 (90*) = 7
H6 (lyco, subie, etc.) = 8
double row radial = 8
I6 (bmw, caterpillar, etc.) = 9
V12 (only if 2xI6 on same crank) = 9
turbine; electric = 10+

vibration patterns in recip engines are well known yet each engine design will exhibit unique vibration profiles.

there are 2 types of PRIMARY vibes in a recip engine: pulse vibe and dynamic vibe (i emphasize "primary" b/c the engine gurus know there are many other vibes in a recip engine).

"stroke" will affect "pulse" vibe in that an engine with more pulses per revolution will be smoother. 8 cyl vs 4 cyl, etc. thus a 2-stroke will be "smoother" than an equivalent 4-stroke all other things being equal.

for engines themselves dynamic balance (rotational vibration) is FAR more important than "pulse" vibration (EXCEPT for aircaft propellers...more on that later). all engine designers must decide the best compromise between power, smoothness, size, weight, compactness, complexity, fuel efficiency, emissions, cost, etc.

V4's have very strong "wobbles" along the "nod" axis (nod your head)and "wag" axis (wag the tail).

a 2-stroke V4 will be "smoother" than a 4-stroke V4, but the dynamic properties do NOT change. a 2-stroke V4 spinning at 2500 RPM will have the same "pulse" smoothness as a 4stroke V4 spinning at 5000 RPM

in terms of rotational balance, diesel is similar to gas (V4 = V4)
in terms of pulse balance, diesel is worse than gas (pressure spikes)

adding a prop to the crank complicates things enormously....the crankshaft "rings" bc it acts like a torsional spring as it winds and unwinds with every pulse. the energy "pumped" into the prop gets reflected back to the crankshaft like a wave bouncing off the wall of a pool. if the prop is metal, it also "rings" at certain frequencies as the blades bend and recoil with every power pulse. (this is why changing to electronic ignition and/or high compression pistons results in different operating limits for the same prop).

the bottom line: any vibes from the original configuration (V4, V8, diesel pulses, etc.) are magnified by the propeller and reflected back into the engine as larger vibes .... harsh engine + prop = harsher vibes

when the whole mess is bolted to a metal airframe with its own "ring" signature, one can see how the vibe issue becomes amazingly complicated.
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Last edited by bumblebee : 11-25-2007 at 07:32 PM.
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