Wrong placement of center of mass of some engines (jet and rapier)

[Guest]

What the heck?

I guess it's either a bug or Squad did this with the idea of making plane balance easier but it's really an annoyance more than anything else to me.

And it's essentially having the model part and physic part in 2 different spots, very bad.

[Grumman]

It's deliberate, and I like it. It's a bit of a kludge, but it simulates the fact that a jet engine is inside the fuselage, not just a nozzle strapped to the back.

If you don't like it, there is a variable in the config files for this offset - set it to zero and it should return to the old, unrealistically back-heavy implementation.

[Guest]

I figured that much. Not a bad idea but overly exagerated.

I mean look at the distance between the part and the CoM! This is ridiculous

See I'm making a SSTO / vertical lander, and this is really, really terrible for the balance

How do I revert this? In the config file of the part or in the craft file?

[selfish_meme]

Most jet engines are several metres long what's ridiculous about it?

J58 in the sr71 was over 5 metres long before intakes and nozzle. I think the whiplash is modeled on it vaguely.

Edited July 23, 2015 by selfish_meme

[Grumman]

How do I revert this? In the config file of the part or in the craft file?

Go to the config file for the part. Find a line something like "CoMOffset = 0.0, 2.3, 0.0" and change the second value.

[Wemb]

It does let you do some really sneaky things though - the idea of slapping one of these engines onto a rover solely to put it's centre of mass somewhere below the surface it's travelling on is very cool, if incredibly cheaty.

Wemb

[Coga19000]

It does let you do some really sneaky things though - the idea of slapping one of these engines onto a rover solely to put it's centre of mass somewhere below the surface it's travelling on is very cool, if incredibly cheaty.

Wemb

Wait, what is there to be won by this configuration? My humble and uneducated quess is that the river will just spontaneously explode due to the KSP physics engine.

[Wemb]

Wait, what is there to be won by this configuration? My humble and uneducated quess is that the river will just spontaneously explode due to the KSP physics engine.

Think about where the center of mass is? What happens when cars turn corners - and how that affects what will eventually happen to them if they start to topple?

When you turn in a vehicle, you're producing a sideways force. As your center of mass is above the ground this creates a torque and thus an upward lift on one side of the vehicle - if this gets too big, you'll flip. Or, if your on Minmus, if you go over a pebble, you'll flip.

If your CoM was below the surface of the ground the torque would act in the opposite direction - gluing you to the ground the harder and faster you turn. I suppose, eventually, you'll 'produce enough downforce to 'crash' into the surface - but the crash resistance of the wheels is pretty big, especailly compared to that of gravity in places where you really could do with more downforce.

Ah! Here you go - found a video:

Wemb

Edited July 23, 2015 by Wemb

[cantab]

It makes some sense - as mentioned, a real jet engine isn't just a nozzle. But I think it could have been implemented a lot better by changing the models to be longer.

[Grumman]

It makes some sense - as mentioned, a real jet engine isn't just a nozzle. But I think it could have been implemented a lot better by changing the models to be longer.

But 90% of that model would have to be able to clip into whatever fuselage you are using where you couldn't see it. You couldn't just use the engine as the fuselage, or else it would not work with parts like the MK-2 Bicoupler.

[klesh]

Jet engines are long, though most diagrams include the intakes too. the CoM decision makes sense to me.

http://www.airplanesandrockets.com/magazines/air-trails/images/jet-turbine-engine-cross-section-air-trails-july-1951-2500x1482.jpg

[Starwaster]

It makes some sense - as mentioned, a real jet engine isn't just a nozzle. But I think it could have been implemented a lot better by changing the models to be longer.

Why? The only part you will see is the nozzle. Where is this longer model going to be? Inside? Where it won't be seen?

Here is an F16 engine. The horribly drawn red line marks where the nozzle begins. You can only see what is to the left of the squiggly line. Everything to the right is buried deep in the part you attached it to. The blue + is roughly where its center of mass is. (above a point dead center between the wheels on the carriage)

There's just no point in having anything more than the nozzle for most of the jet engines we have in this game.