WesWorld

1.) what's the best way to accurately 'tweak' an aircraft to get a historical HP figure?

2.) has anyone else noticed that it seems to give unGodly high weight numbers for guns?

1. The answers may vary I set the propeller diameter to something that seems reasonable, slide the efficiency up or down depending on when the base model of the engine came out and then twiddle with the bypass to get the right number.

However, RA and Hrolf know waaaay more about engines and can probably give you a different way, I know Hrolf has been concerned about fuel consumption and efficiency's effects on that.

2. It has been noted. Historical aircraft weapons varied greatly in weight, due to shell weight, muzzle velocity and other aspects. However, most of the final weight is supposed to be "bracing".

In particular there is a issue (to me) with the Cannon/MG numbers if you're trying a 13.2mm/15mm/17mm MG vs. cannon.

I have managed to very nicely SIM several historic aircraft to the right weights and speeds, so while rough it is ballpark. Now go try to put a 20mm in a turret ..Muhahahahahahahaha

3. As an additional bit of info, on the Airframe H63 "unstreamlined cross section" tab, RA has indicated a number as little as 1/3 the default is acceptable for inlines vs. radials.

here is a linke to some OTL gun weights. You can manually enter them on the gun tab if you unprotect the sheet. It will then generate the appropriate bracing for that gun.

Gun weights

In many, but not all, cases the lighter guns also have lower MVs or round weights.

Yeah... when you make artillery light, something has got to give. That's why in RL, I love the Ma Duce; it's like trying to lug around a 6 foot stick of pulpwood, but she can handle any kind of punishment.

Little heavy, very capable, very reliable. That's a winner.

However, for air-to-air, that web site does delve into the merits of various weapons combos, there's an hotlinked index when you scroll to the bottom of the page.

To get a required horsepower, set the diameter of the propeller first. Anything between 8 and 14ft is reasonable for fighters and bombers tend to be a bit larger at around 12-15ft at the moment. Then in the efficiency box put something around 20-23%. Then adjust the bypass ratio to get the correct horsepower.

Quoted

3. As an additional bit of info, on the Airframe H63 "unstreamlined cross section" tab, RA has indicated a number as little as 1/3 the default is acceptable for inlines vs. radials.

I've been taking it as relative frontal area compared to a 9-cylinder radial engine. A V-12 is 39% the frontal area for example.

Re: 1 - The fuel consumption issue has pretty much been resolved: you use the Efficiency setting to set the SFC (specific fuel consumption). This thread http://88.198.26.117/kunden/oponn/wbblit…eadid=5419&sid= has numbers we've found for a number of different engine, but in a few cases there are anomalies to track down (the V-1710, for instance, is almost surely a non-cruise power setting). That's probably either the first or second thing to set, after that set the propeller diameter based on something reasonably similar, and then adjust the bypass to get approximately what you want for low altitude power. Supercharger altitude is probably 15,000 feet or lower at this period.

Re: 2 - As far as I can tell, the spreadsheet formulas are designed to produce fairly reasonable numbers for a couple bore sizes, but they fall down when you get too much bigger than that (you don't want to see how heavy it thinks a 50mm MK-214 should be). For sizes of guns above .50 for machineguns and 20mm for cannon, you're better off unprotecting the sheet.

Quoted

Originally posted by Hrolf Hakonson
Re: 2 - As far as I can tell, the spreadsheet formulas are designed to produce fairly reasonable numbers for a couple bore sizes, but they fall down when you get too much bigger than that (you don't want to see how heavy it thinks a 50mm MK-214 should be). For sizes of guns above .50 for machineguns and 20mm for cannon, you're better off unprotecting the sheet.

Oh, trust me, I saw.
I was wondering how heavy it would be to install 3x37mm in a light bomber for anti-shipping work. The M4 37mm weighed about 215 pounds empty, and about 255 pounds with a loaded drum. Imagine my surprise when Planebuilder spits out 1007 pounds PEER GUN. That is insane.

From looking at the varying weights between models of the Yak-9 with enigne mounted cannons, I estimated that a low powered 37mm should be around 250kg with higher powered ones around 300kg including the bracing. For larger guns of around 45-50mm, something like 450-500kg seems reasonable.

Luckily it's really not necessary to use the User Equipment page for these things, since you just enter a weight in the User Equipment box on the Airframe page.

Based on what I've found, the lighter weight MK-214 50mm cannon (a high velocity 50mm) weighed 490kg. The heavier weight BK.5 weighed 540 kg. These weights include the mountings, muzzle brakes, etc.

Quoted

Originally posted by Red Admiral
From looking at the varying weights between models of the Yak-9 with enigne mounted cannons, I estimated that a low powered 37mm should be around 250kg with higher powered ones around 300kg including the bracing. For larger guns of around 45-50mm, something like 450-500kg seems reasonable.

250 kg is a bit big for a 37mm cannon.
As for bracing, I know a low-velocity 40mm only needs only about 100 pounds of bracing to keep it from rattling itself loose... God knows I lugged one around enough.

With the M4 37mm weighing only 213 lbs empty, adding in a 5.5 pound mag with 30 rounds at 1.34 pounds each, I get 259.67 pounds per gun. Since the muzzle velocity and projectile weight of the weapon is lower than that of the Mk-19 with which I am familiar, I would assume that the necessary weight of mounting would be only marginally heavier for the M4, to take into consideration the fact that it weighs 3x as much as the Mk-19.

As a Mk-19 doesn't really take any kind of mounting weight (45 pounds), I'd say that the M4 could be mounted on 125 pounds for a total of about 385 pounds, for guns and mount- about 175 kg as opposed to 250 kg that you suggest. Now, I'm a heavy weapons man, not an aircraft engineer, so i could be vastly wrong... but that's my guesstimate.

The complete round for the M4 weighs 1.99 lbs, the projectile by itself weighs 1.37 lbs. The M4's muzzle velocity is A LOT higher than that of the MK19: the M4's muzzle velocity is around 2,000 fps, where the MK19 is around 800 fps. What I'm finding difficult to find is the weight of the MK19's grenades.

Quoted

Originally posted by Hrolf Hakonson
The complete round for the M4 weighs 1.99 lbs, the projectile by itself weighs 1.37 lbs. The M4's muzzle velocity is A LOT higher than that of the MK19: the M4's muzzle velocity is around 2,000 fps, where the MK19 is around 800 fps. What I'm finding difficult to find is the weight of the MK19's grenades.

Crap... I misread that entry.
LOL!
I got my units turned around- thought it was 610 fps instead of 610 m/s. Yeah... that puts it's MV about 2.25x the Mk-19's, so a lot more bracing would be needed. My bad.

I can't remember the total weight of a Mk-19 round; I can tell you that a belt has 32 (old belt) or 48 (new belt) rounds, and that the box is 'heavy'... call it half the weight of the gun. I'm sure that if I dig around in our library at the unit I could find individual round weight, but I'm thinking somewhere in the 1-1.25 pound neighborhood.

EDIT: site I found says .75 pounds

40 x 53SR 43.6 rim diameter USA HE / 245g 240m/s
Modern high-velocity automatic grenade

250-300kg seems about right for a 37mm weapon.

At the other end of the scale is the 102/35 weapon used on the Piaggio P.108A which weighed 1500kg including the recoil system. However, the magazine weighs another 1200-1300kg.