A Little Help, Please

Drzook

Drzook

Charter Member
Hey all,
On a lark I decided to swap out virtual engines on my Lockheed Vega from the default Wasp to a BMW-132 (same as that on the Junkers W34 and Ju-52; basically a license built P&W Hornet). It wasn't too much to find out weights on the engines in question and adjusting the cfg file to reflect the higher weight of the BMW was a snap. I took my Vega on a couple of test flights to see what nearly 300 extra horsepower and only 400 extra pounds does to a plane. Climb rate was up by over 50%, to 3000fpm+. Range will likely suffer due to the bigger engine but...did I mention the 'homesick angel' climb rate? Top speed was estimated to be over 225mph; however at around 200mph it starts shaking like a paint mixer:isadizzy:.
I know there is some line in the cfg file that can stop this; anyone care to share?

Oh and if anyone was wondering why a BMW 132 it was because recently I stumbled across OBIO's wonderful soundset for single BMW 132 engines and I just love that tick-tick-tick sound it makes.:ernae:
 
I am flattered by the fact that "my" sound pack...actually Lawdog's work with my tweaks...inspired your insanity.

The shaking could be due to the MOI needing adjusting. The MOI is in the section of the config file that looks like this:

;Moments of Inertia
empty_weight_pitch_MOI = 1550.000 <==adjust this if shake is up/down
empty_weight_roll_MOI = 1130.000
empty_weight_yaw_MOI = 2330.000 <==adjust this if shake is side to side
empty_weight_coupled_MOI = 0.000
CG_forward_limit= 0.000
CG_aft_limit= 1.000

I don't know if the MOI settings need to be raised or lowered. MOI is one of those areas that are still outside of my understanding...but I am sneaking up on them.

Or it could be due to the plane exceeding the maximum speed setting in the air file. I have no clue how to fix that....air files and me get along like gas vapors and lit road flares. Every air file, or nearly every, that I have tweaked has resulted in the plane jumping into the air, spinning about and exploding.

OBIO
 
I'm thinking it's the maximum speed setting; anywhere 195mph and slower and it behaves great.
I'm pretty sure the real version could go faster than 200mph without breaking much of a sweat; after all Wiley Post was believed to break 300mph in Winnie Mae (sans landing gear and in the jet stream but still pretty fast) and the Orion was just a retractible geared low wing version of the Vega and that could do 225mph.
Now if I could figure out where the Vne setting is on the cfg file. I looked at the air file but there didn't seem to be much there. I thought it was the reference speeds section in the cfg file but that didn't seem to do anything.
 
Just wanted to say thank you OBIO. Your hunch about the MOI values was exactly what was needed to cure the shakes. I posted this thread in the FD forum here where Sparks gave me some helpful advice. I changed the pitch MOI from 1788.8 to 2300 and that did the trick. Not sure about the fuel burn but that Vega gets up and goes!:gameon:
In real life there were several of Lockheed's 'wooden wonders' that were powered by something other than a Wasp. IIRC there was a Vega that was powered by an R-1690 Hornet for some air race (no cowling so it was aesthetically challenged). Roscoe Turner's Air Express was also Hornet powered. Charles Lindbergh's Sirius had a Wright R-1820 Cyclone for motive force and there were several Orions that were Cyclone powered as well (Swissair's 'Rote Orions' come to mind).
 
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