Egg damage: Touch it up myself, or let a body shop handle it?

[Jeff7]

Damage:

I was driving home awhile ago and someone going the other way whacked the car with an egg. Based on our relative speeds, it was the equivalent of a 70+mph hit, on the driver's side back door.

The stuff stayed on there for awhile....I'm not particularly fastidious about keeping the car clean. That's what rain is for. *cough*

I really didn't know that egg was such a big deal.
My only experience with eggs has been in cakes or scrambled in a frying pan.

Most of the white scrubbed off with laundry detergent and dish soap, at least until my arm was thoroughly tired, and I started at it late in the day and it's getting dark earlier now. (Those cleaners are designed to remove that sort of thing, so what the hell, why not.)
The worst of the damage that I'm concerned with is where the impact itself blew away the paint, right down to the metal.

I've got a small bottle of touch-up paint made for this car's year and model, as well as clear-coat.


I've never attempted paint touch-up, so I don't know what the results will be. DIY, or auto body shop?

 

[Sabrewings]

I've had good experience fixing that sort of damage with Dr Color Chip. Not sure what touch up kit you have.

 

[razel]

It definitely looks like it's down to the metal and you did use the right immediate products you had from doing further damage. Don't bother with the paint body shop. Only go if the clearcoat starts to fail.

Normally, I'd recommend a polish or paint cleaner, but in your case prior to the touchup paint, put dishwashing fluid (like Dawn or Joy) onto a wet paper towel and cover the area with it then cover that with plastic bag on top. Essentially like baked, caked on food on a pot you're soaking it. The plastic bag prevents it from drying up. Leave it for 20 mins, remove then rinse with hot water. Yup... sounds funny huh. But the kinetic energy from the heat will help.

Once the surface is clean. Use a toothpick to apply the touch up paint and let it sit for 24hours to 1 week. The thing about touchup paint it often if the surface isn't clean it'll come right off. Which is why I recommend a polish or paint cleaner, like Meguairs Ultimate Polish or Mothers Ultimate Step 1.

 

[yhelothar]

Touch it up. If it's down to the metal, you'll need a primer touchup pen.
Sand the area down lightly with 1000 grit to give everything good adhesion. Some of your touchup paint will inevitably bleed past the chip and you want to make sure there's a good surface for the paint to hold. Make sure you don't overdo the sanding and go through the clear coat. You don't want to go past the orange peel on the factory paint. Next you'll want color in the pits with your touchup pens. Just one or two coats should be fine. The trick to making everything look good is in the clear coat. Get a clear coat touchup pen. Fill it in a bit past the level of the surrounding paint. This should take many coats to do so. After it dries, you sand everything so all it's all flush with the surrounding paint with 1000 grit, 1500 grit, and 2000 grit, and buff it out with some rubbing compound.

 

[LTC8K6]

Based on our relative speeds, it was the equivalent of a 70+mph hit, on the driver's side back door.

Both of you were going 70+mph?

 

[Jeff7]

Both of you were going 70+mph?

I was going ~35mph one way, and the other person was going ~35mph the other way.
So, the impact from the egg would have been the same as if someone chucked an egg at 70mph at a stationary car.



Touch-up paint brand: I think I got it from a Subaru dealer online, I don't remember anymore. I bought it a few months after I got the car in 2012. I'm on lunch break at work at the moment, so it'll be a few hours until I can get the brand of the paint.

I've got a bit of what might arguably called "relevant experience" from my PC case-modding days, including some use of Bondo, and then plenty of fine-grit sandpaper and rubbing compound.
That was a $40 case though, not a car.

 

[LTC8K6]

I was going ~35mph one way, and the other person was going ~35mph the other way.
So, the impact from the egg would have been the same as if someone chucked an egg at 70mph at a stationary car.

Well, I was trying to politely tell you that it doesn't add up that way.

When two moving objects collide, you don't add the speeds together to get the force of the collision on each object.

The total force is divided among the two objects. Neither one sees the whole force.

A simple example is two cars of the same weight traveling at 55mph. They hit head-on flush. Each car sees the force of a 55mph collision with a stationary barrier. Neither one sees the force of a 110mph collision with a stationary barrier.

The actual formula is more involved, and you have a great weight disparity in your case, but the general idea is the same.

The total force is divided up, not added together.

For informal discussion purposes, the egg hit your car with the force of a 35mph impact.

 

[Pulsar]

Well, I was trying to politely tell you that it doesn't add up that way.

When two moving objects collide, you don't add the speeds together to get the force of the collision on each object.

The total force is divided among the two objects. Neither one sees the whole force.

A simple example is two cars of the same weight traveling at 55mph. They hit head-on flush. Each car sees the force of a 55mph collision with a stationary barrier. Neither one sees the force of a 110mph collision with a stationary barrier.

The actual formula is more involved, and you have a great weight disparity in your case, but the general idea is the same.

The total force is divided up, not added together.

For informal discussion purposes, the egg hit your car with the force of a 35mph impact.

Uh... Jeff is correct. If an egg is thrown from a vehicle moving at 35 mph and hits a vehicle moving in the other direction at 35 mph, then the closure speed of the egg on the vehicle, relative to the vehicle, is 70 mph. It's pretty basic physics.

 

[Jeff7]

Brand of touch-up paint is from the aptly-named company Automotive Touchup.

Uh... Jeff is correct. If an egg is thrown from a vehicle moving at 35 mph and hits a vehicle moving in the other direction at 35 mph, then the closure speed of the egg on the vehicle, relative to the vehicle, is 70 mph. It's pretty basic physics.

And I figured the difference in momentum was sufficiently lopsided that I didn't have to work out whether it was truly an elastic or inelastic collision, or the fact that the motion vector of the egg was not perpendicular to the impacting surface. I'm sure that some of the egg did bounce off, but plenty of it was firmly adhered to the side of the car.


Fly hits a windshield.
Physics says that the car will slow down a bit.
Enough to warrant an extra press on the gas pedal to offset it? Probably not.


For purposes of this thread, it was a damn fast egg hit, enough that the crushing eggshell was able to destroy the paint and expose metal. Most of what I read about egg damage was more concerned with the effect of the egg white on the paint itself. I guess in a normal egging, it's idiots throwing eggs at stationary objects, and there's a limit on how fast you can throw an egg, determined mostly by the strength of the eggshell versus the length of a human arm and the maximum acceleration you can get in that distance.







...and in spite of the treadmill, the plane takes off.

 

[LTC8K6]

Uh... Jeff is correct. If an egg is thrown from a vehicle moving at 35 mph and hits a vehicle moving in the other direction at 35 mph, then the closure speed of the egg on the vehicle, relative to the vehicle, is 70 mph. It's pretty basic physics.

No one said anything about the "closing speed".

The impact force is a 35mph force, despite the "closing speed" of 70mph.

You don't add the two speeds together to get the force on only one of the objects involved in a direct collision.

It's pretty simple.

If you and I each line up facing each other, and we each throw an egg at 20mph, and the eggs hit, each egg sustains a 20mph impact force.

This same discussion comes up over and over again...

 

[MongGrel]

...

 

[Jeff7]

How's about this: The velocity physics can go in their own thread in OT and be resolved there.

 

[LTC8K6]

How's about this: The velocity physics can go in their own thread in OT and be resolved there.

Not worth it's own thread, and I doubt it would be resolved... :biggrin:

 

[angminas]

If you switch doors, the egg will take off.

 

[RGUN]

No one said anything about the "closing speed".

The impact force is a 35mph force, despite the "closing speed" of 70mph.

You don't add the two speeds together to get the force on only one of the objects involved in a direct collision.

It's pretty simple.

If you and I each line up facing each other, and we each throw an egg at 20mph, and the eggs hit, each egg sustains a 20mph impact force.

This same discussion comes up over and over again...

Excellent point, now how did I miss the fact that Jeff7 was able to place an additional egg directly in the impact zone to absorb the blow?

 

[LTC8K6]

Excellent point, now how did I miss the fact that Jeff7 was able to place an additional egg directly in the impact zone to absorb the blow?

I'm not sure how you got that idea about my example?

If I had used watermelons as an example, what would you have said?

"Where did the watermelons come from?" :biggrin:

 

[Ferzerp]

Your understanding is a bit off really. The energy transfer is more about what acceleration each object experiences as well as its mass. You can't really simplify it to the two cars example. In that case, the 35 mph cars both experience a ΔV of approximately 35 mph.

The car vs egg problem is a bit different. If the egg stayed intact and stuck to the car, the egg would in fact experience a ΔV of 70 mph (or rather *slightly* less since the car would lose a fraction of 1 mph in velocity), and the car would experience the same energy transfer. However, it is never that simple since the collisions aren't perfectly elastic.

That said, just saying "two objects colliding at the same speed in opposite directions only experience a force equal to their individual speeds" only holds true for objects of exactly the same mass that both come to rest due to the collision. It is all about the ΔV of each object.

 

[tweakmonkey]

While we are here discussing the physics involved I'm interested was this a Free Range egg? Or maybe just grass fed. I wonder if it was organic. Does the impact of a duck egg have the same concerns as a chicken egg? How can you be sure it wasn't a duck egg? Or maybe it was the egg from a new species that happened to begin its existence the very minute you drove down the road? However you look at this tragedy, the real issue at hand is that the world is now one egg poorer and the delicious meal that could have been enjoyed will never come to be. I say we have a moment of silence for this could-be Denny's breakfast or cookie dough ball. Does true silence exist??

 

[RGUN]

I'm not sure how you got that idea about my example?

If I had used watermelons as an example, what would you have said?

"Where did the watermelons come from?" :biggrin:

It's relevant given your example. So when they crash a car into a barrier at 30mph do we consider that a 15mph impact, or do we understand that the barrier is rigid? Does it matter if the car is stationary and the barrier moves, or if they both move at 15mph?