Light case vs heavy case: protection from shock transfer

[StringJunky]

This has been asked on a guitar forum. Scenario: Two cases, one is substantially heavier than the other in that the shell is much thicker. The fit for the guitars is close all around and the interior material and structure is identical. Dropped from some arbitrary height with an acoustic guitar inside, which would protect the guitar from shock the best? The difference between the two is the weight; Let's say one is double the weight of the other.

Also, would a snug fit protect better than having a little space around the guitar, so that it can move a bit?

Edited July 11, 2018 by StringJunky

[DrP]

I can't answer your question as written I am afraid because I do not know the answer.  But, the best cases from what I can tell seem to have a very hard exterior with tight fitting, soft, shock absorbing padding on the inside.

At a guess - I'd go with hard shell with a tight snug fit into a soft padded interior. The most expensive guitar case I ever bought is like this and it is excellent  -  you can jump on it or throw it onto a plane and the guitar will be fine inside.

[StringJunky]

1 hour ago, DrP said:

I can't answer your question as written I am afraid because I do not know the answer.  But, the best cases from what I can tell seem to have a very hard exterior with tight fitting, soft, shock absorbing padding on the inside.

At a guess - I'd go with hard shell with a tight snug fit into a soft padded interior. The most expensive guitar case I ever bought is like this and it is excellent  -  you can jump on it or throw it onto a plane and the guitar will be fine inside.

The point of focus is the weight of the shell and how it transfers the impact to the contents. The cases shells can be assumed to be unbreakable. What you suggest is the received wisdom. The poster was wondering how  physicists would see the scenario and I thought I'd ask here.  Basically, is it worth carrying an extra 14 pounds or does actually cause a worse outcome? The cases will fall at the same velocity but the heavier cases has more momentum, doesn't it?

[DrP]

20 minutes ago, StringJunky said:

The point of focus is the weight of the shell and how it transfers the impact to the contents.

I don't think that 'weight' would be that relevant.  It would have more to do with the 'hardness' of the material and it's ability to distribute the stress of the impact...  so a little compressibility but high strength for the outer shell and a soft shock absorbing inner lining. I can't see how the weight would be relevant at all.  Sorry - that's all I've got.  

 

[StringJunky]

1 hour ago, DrP said:

I don't think that 'weight' would be that relevant.  It would have more to do with the 'hardness' of the material and it's ability to distribute the stress of the impact...  so a little compressibility but high strength for the outer shell and a soft shock absorbing inner lining. I can't see how the weight would be relevant at all.  Sorry - that's all I've got.  

 

Ok. Cheers. What you say makes sense. So, would you say the extra weight is superfluous? Say, comparing a Hiscox Pro to a Calton. The latter are very heavy apparently and about $1000.

Edited July 11, 2018 by StringJunky

[dimreepr]

23 minutes ago, StringJunky said:

Ok. Cheers. What you say makes sense. So, would you say the extra weight is superfluous? Say, comparing a Hiscox Pro to a Calton. The latter are very heavy apparently and about $1000.

It's not about weight, it's about the ability to dissipate the energy evenly across the entire mass. 

[koti]

If both cases would be identical with only the mass being the difference the lighter one would give better protection to the guitar. The reason is that the heavier case would hit the ground with a higher force than the lighter case. More force = more damage.

Edit: same goes for a scenario in which you bump the case against something, even with a perfect fit of the guitar inside there’s still more momentum acting on the bridge and the construction of the guitar. If you say kick the both cases laying on the ground - same thing, always more force will be acting on the heavier case thus on the guitar inside. The same goes for both cases being flown into space and being bumped, kicked around in zero gravity (obviously the drop scenario doesn’t apply in zero gravity) The only scenario when it doesn’t matter is when there are small forces being applied onto the two cases, a mikd bump or a tap which would not be enough to move either of the cases. 

Edited July 11, 2018 by koti

[John Cuthber]

40 minutes ago, koti said:

If both cases would be identical with only the mass being the difference the lighter one would give better protection to the guitar. The reason is that the heavier case would hit the ground with a higher force than the lighter case. More force = more damage.

Yes and no.

There's more damage done, but not to the guitar.

Ask the people who make tanks for the army.

[koti]

29 minutes ago, John Cuthber said:

Yes and no.

There's more damage done, but not to the guitar.

Ask the people who make tanks for the army.

I don’t think its a good example. A 20 ton guitar case with a tightly fit guitar inside, when droped from 6 feet would create more damage to the guitar than an identical, lighter case. Tanks are built the way they are for other reasons.

At least I think so.

Edited July 11, 2018 by koti

[StringJunky]

1 hour ago, John Cuthber said:

Yes and no.

There's more damage done, but not to the guitar.

Ask the people who make tanks for the army.

My question is: is more energy - a shock wave - transferred to the guitar from it being inside a heavier weight than a lighter weight? Everything else being equal.

Edited July 11, 2018 by StringJunky

[John Cuthber]

Shock waves are unlikely to pass efficiently from a dense material to a less dense one.
However, the fundamental question isn't well specified.

Imagine getting a hollow wooden ball enclosed in a layer of aluminium foil.
If you drop it, it will get damaged.

Imagine putting it in a thick metal sphere + dropping it.
Well, it might protect the wood, it might not. Certainly, if the metal gets dented it wile damage the timber.
If the metal is thick enough it will survive intact but, even if it does that doesn't guarantee the safety of the wood, because the metal will flex during the impact..

If you put a layer of foam between them then, if the foam is thick enough to take up any flexing of the metal then the wood will be fine.
In that case the weight of the metal is not very important.

[StringJunky]

1 hour ago, John Cuthber said:

Shock waves are unlikely to pass efficiently from a dense material to a less dense one.
However, the fundamental question isn't well specified.

Imagine getting a hollow wooden ball enclosed in a layer of aluminium foil.
If you drop it, it will get damaged.

Imagine putting it in a thick metal sphere + dropping it.
Well, it might protect the wood, it might not. Certainly, if the metal gets dented it wile damage the timber.
If the metal is thick enough it will survive intact but, even if it does that doesn't guarantee the safety of the wood, because the metal will flex during the impact..

If you put a layer of foam between them then, if the foam is thick enough to take up any flexing of the metal then the wood will be fine.
In that case the weight of the metal is not very important.

Right. Cheers. 

[Bender]

It depends on the surface it is dropped on. If a significant part of the kinetic energy is absorbed by the impacted surface, a more massive case would slow down slower and anything inside will experience less acceleration and less damage.

On a concrete surface, the shock absorbing qualities of the outer case become more important if it is more massive.

[John Cuthber]

OK, so I solved the problem for a spherical guitar, and Bender solved it for the case where you only drop the guitar (and case) in a muddy field or above a vat of cold porridge.

I wonder which of those is less use.

 

[DrP]

I dropped my Ovation onto a concrete step last month when the strap came of the button....  it was pretty old and had a few scratches...  I used to use it as a kick about guitar because I got it dirt cheap and it didn't seem to matter much.  Recently though I checked the price of it and, er, I can't use it as a kick about any more...  I had some bits repaired and decided to treat it with respect...  I've had it 15 years at least...   now there is a nasty split in the nut from the drop and I am gutted!     Still plays nice  -  I guess it can go back to being a kick about.

Wish I had been keeping it in any type of case

 

9 minutes ago, John Cuthber said:

OK, so I solved the problem for a spherical guitar,

Bloody physicists! lol.  

 

[StringJunky]

5 hours ago, John Cuthber said:

OK, so I solved the problem for a spherical guitar, and Bender solved it for the case where you only drop the guitar (and case) in a muddy field or above a vat of cold porridge.

I wonder which of those is less use.

 

LOL! It's surprisingly more difficult to specify the precise question than I thought it would be.

5 hours ago, DrP said:

I dropped my Ovation onto a concrete step last month when the strap came of the button....  it was pretty old and had a few scratches...  I used to use it as a kick about guitar because I got it dirt cheap and it didn't seem to matter much.  Recently though I checked the price of it and, er, I can't use it as a kick about any more...  I had some bits repaired and decided to treat it with respect...  I've had it 15 years at least...   now there is a nasty split in the nut from the drop and I am gutted!     Still plays nice  -  I guess it can go back to being a kick about.

Wish I had been keeping it in any type of case

 

Bloody physicists! lol.  

 

Yeah, Ovation is no more and will only become collectible. Can't you get a new nut made. Easy job for a luthier or guitar tech.

[DrP]

12 minutes ago, StringJunky said:

Yeah, Ovation is no more and will only become collectible. Can't you get a new nut made. Easy job for a luthier or guitar tech.

It isn't a high end one - but not to bad... (Ovation Ultra maybe? I'll check when I get home) -  sounds and plays lovely though - great tones and harmonics and superb action.  The damage is purely cosmetic, but has to devalue the thing.

Got it in a second hand guitar store for £120.00 about 15 to 20 years ago. The pick up had bust...  but I got that fixed. Don't plug it in often anyway. Looked it up recently and they go for about 5 or 6 hundred quid!  I was thinking about selling it...  but with the crack I reckon I'll be lucky to get what I paid for it so I might as well keep it. One of the best guitars I've ever had for a semi acoustic.

 

 

[John Cuthber]

22 hours ago, DrP said:

I dropped my Ovation onto a concrete step last month when the strap came of the button....  it was pretty old and had a few scratches...  I used to use it as a kick about guitar because I got it dirt cheap and it didn't seem to matter much.  Recently though I checked the price of it and, er, I can't use it as a kick about any more...  I had some bits repaired and decided to treat it with respect...  I've had it 15 years at least...   now there is a nasty split in the nut from the drop and I am gutted!     Still plays nice  -  I guess it can go back to being a kick about.

Wish I had been keeping it in any type of case

 

Bloody physicists! lol.  

 

Sorry to hear about the guitar.

For the record I'm a Bloody chemist.