Gr95

Does anyone else have the problem with keeping there sub box in one place. It seems like if I drive enough my box works its way to the middle of the trunk. I was just wondering if anyone has had and fixed this problem. Any sugestions would be great. For now I have a small adjustable shower rod across my trunk that does the job but it looks really bad...........thanks for any help.

Gr95

The only problem with that is I put a full size spare in my trunk. So I really cant make the wood lie flat across......

Whitemax

Place them on the bottom of box, and they will hold under most conditions....

Matt93SE

iTrader: (44)

what about just cutting a small piece of plywood and sticking it along the far edge (on the bottom) of the box?
you could screw into that, and them somehow fasten that to the car just behind the seat..
???


/* just throwing out bones here. */

mingo

iTrader: (4)

use thinner wood, it should fit in between the spare tire and the trim peice that goes over it, and screw L brakets on, so you can unscrew the screws from the box when u need to get to the spare.. i don't know if u get what i'm sayin'.

deathwish

In my Integra I just put some eye bolts on the box and then used bungi cords to hold it to the rear seat latches for the fold down seat. You should be able to find something in there to attatche them to, and you don't need to cut/drill any holes in your car Of course, my box weighs so damn much it doesn't go anywhere, so it's not really tied down...

mingo

iTrader: (4)

u best becareful then, if it's hella heavy then when it moves, it will be movin'. this guy i know have dents that protrude out from the inside of his car because his heavy sub box moved this one time and slamed agains some part of his trunk.

max95q

iTrader: (10)

I Have a Ten in a nicely weighted box. It not too heavy but my box stays in the same place regardless of driving fast or not.

jmax

You idiots. It doesn't matter how heavy the damn thing is. Actually it does. It will move! What's the law of momentum? Something like mass x velocity squared. If you stop fast, like when you run into a tree, the box will continue to move at whatever speed you were going a moment before until something - the rear seat, front seats, your body and then the tree - stops it. By the way, a tissue box on the rear deck when a vehicle stops suddenly from 60mph can hit the back of your head with enough force to instanly kill a human being.

My point being - screw the damned thing down. The L-brackets were the best suggestion. Screw them into the floor of the trunk or one of the side walls. Just don't screw into the gas tank.

Matt93SE

iTrader: (44)

M * v^2 is kinetic energy, not momentum..
but your point is a valid one..

My box isn't bolted down, but then again, it's held in place by my amp rack that IS bolted down.. my sub box is shoved against the back of the rear seat, so it can't move forward even in a werck. it would have to totally destroy the rear structurs of the car to come through my trunk.
Then again I have a 3rd gen and don't have fold-down seats (but I will sooner or later, when I make mine a fold-down type. ;-)


Yes, you DO need to bolt it down. a sudden stop or wreck where the box is even a few inches awsy from the rear seat can cause the box to slam into the back of the seat with enough force to break latches and injure passengers in the back seat. I've been there, seen it in another car. (friend's '92 probe.. guy in the back seat got whiplash abd 2 bruised vertebrae after the driver slammed on his brakes and the box slammed into the backseat and broke the latch, landing on the passenger's back.)

deathwish

You don't have to bolt it down. My who assembly weighs on the order of 250 pounds. We have this whole thing called friction see, and friction depends on the downward force called weight. I've gone to SCCA autox races with my stuff in there and it does not move. Not that it would matter if it did, it's all custom fit so there's not more than 1 inch it could move....

[Edited by deathwish on 10-25-2000 at 08:50 AM]

jmax

You don't have to bolt it down. My whole assembly weighs on the order of 250 pounds. We have this whole thing called friction see, and friction depends on the downward force called weight. I've gone to SCCA autox races with my stuff in there and it does not move. Not that it would matter if it did, it's all custom fit so there's not more than 1 inch it could move....

'Deathwish'- now that I believe. The rest is bull. Friction helps a little but it doesn't stop the box from moving. If you know anything about acoustics then you know that when the subs move, unless the box is secured to the vehicle it will move the opposite direction of the cones. This decreases output to some extent, I've never measured withan spl meter. It also gives you different output because we know how important the sub placement in vehicle is for max output and for SQ output.

deathwish

I love this guy! Calls us all idiots and as proof of this gives us the wrong formula for momentum. You go boooy! If you know enough about friction, you'd know that it <b>will not</b> move until the static friction force is overcome.

Let's look at this. First of all, you know nothing about my setup. I'm weighing in at 250 pounds. Now, I have no desire to go out and measure it, so let's just guess that the coefficient of static friction for my system on the floor is roughly .4 (that's fairly close for wood on steel). This means that for the box to move, there needs to be an opposing force of 100 lbs. Now, I don't know what kind of SPL setup you are running, but my subs do not produce 100 lbs of force. In fact, most of the force they do produce is a moment about the plane between the system and the floor which will not cause any movement (ok, some due to compressions of the wood, etc but no more than if it was bolted down).

Now, if we look at normal driving, the acceleration required to move my system would be about .4g. Again, I don't know how you drive, but on the street I don't generally exceed .4g. Further, at the autox I did not hear my box move nor did I find it moved when I was finished, leading me to believe there's probably a greater coefficient of friction than I assumed or that it's heavier than I assumed (and yes, I know it did not move because I have the metal marked where it is placed for when I take out and put it back in).

Now, also keep in mind that I said I have about 1" of play where it actually could move if it wanted to. I don't feel the need to go and figure out how fast the box would be moving when it hit the end of it's 1" journey, but let's just say it ain't very fast. In an accident, what would happen is that a big sheet of plywood would smack into the rear strut towers. Now, if it managed to break through them or break in half or some other miracle, and then get through the sheet metal of the rear seatback and the rear seat structure and into the cabin, then that's enough damn force that some lbrackets aren't going to do any good either.

Now I'll give you the benefit of the doubt, perhaps I didn't make myself clear. I was speaking about my system. I can't say on other people's systems, if you just have a box sitting in the trunk you should definately secure it. But my point was, you can design an install such that it does not need to be bolted down as I have done. I'm not sure my car is capable of the performance it would take to move the box, and if I'm driving that fast I'm not worried about the sound anyway. Further, if in an accident there is enough force for my system to break into the cabin, I'd say that's the least of my worries because I'd have just been in a very bad head on collision and I'd probably be dead.

ngthing

My box weights in at over 150lbs, and it moves. (it's not carpeted). if i wre you, i'd take that sucker, put it where the passangers sit in teh back, and you'll have no problem ;p

jmax

That's okay. Unless Alumapro recently reformed their baskets out of lead and somebody reworked the atomic formula of plexiglass- Deathwish's box does not weigh 250 lbs. Which would only be around 113 kilo's anyway. So the correct formula is mv not mv(squared). It's been years since I took any math course let alone physics, statics or dynamics and I never said that that was the formula anyway. I think I said "something like . . ." which was my clue that it probably wasn't exactly right. Newton's second law has not changed. An object in motion will remain in motion until a force acts on it to cause a change.

deathwish

1) What does the atomic formula of plexiglass have to do with anything? The vast majority of my sub/amp rack assembly is medium density fiberboard.

2) What do kilograms have to do with anything? Come over and take it out and put it back in and tell me what it weighs...

3) mv is momentum, 1/2(mv^2) is kinetic energy, these do not changed based on the weight.

4) Newtons second law is F=ma. Newtons first law says that an object in motion tends to stay in motion, and an object at rest tends to stay at rest. This is really simple, what happens when you go to push on a car and it doesn't move? You haven't supplied enough force to overcome static friction. It does not matter that you are applying a force, because an equal and opposite force is pushing right back at you. The same thing happens with a box, it absolutely will not move until you overcome the static friction force. Not an inch, not a millimeter, not a micrometer, nothing at all until you overcome that force. For a box on carpet, this force is not very great. However, for a large, heavy fiberboard piece with a lot of weight pushing down on it, the static friction force is significant.

Look, you can do what you want and you can think what you want, but when you call me an idiot and then tell me the weight doesn't matter when you are quite wrong, that's bound to **** me off. I really don't care when people get physics wrong, but if you're going to insult me and then make an incorrect statement, I'm going to care. Really, we can talk about this sort of stuff without resorting to name calling, eh?

jmax

Show me how an MDF box, not that yours is all MDF, with a volume of roughly 2 cubic feet has a mass of 113 kilograms. I see now you have added the weight of your amps and the amp rack wich was originally not part of the sum. My statement that anyone who thinks that the box doesn't move do to the force of friction in the trunk with the trunk carpet is an idiot is a sound statement and I stand behind it. The force of friction in your trunk is not as great as that of what your tires(rolling) have with the road. Remember, the max can stop from 88 ft/sec in under 130 ft. That's without the aid of a tree or other substantial object.