Sound System in a shopping trolley

Hello everybody, I'm a new face around here with an idea for something a little different.  What I'm wanting to build is a mobile sound system strapped to the back of a mountain bike, probably in a shopping trolley. This might sound a little strange but it's for carnivals/festivals/outdor parties, just something to give you a giggle and make you dance for a while.

I'm thinking about building a plywood box the size of the trolley, ventilated with 12v PC fans. What I want to know is how would I go about earthing such a device? I remember seeing an earth rod type thing hanging from the back of old Metro's when I was a child, is the kind of thing I should be looking for or is there a better solution out there?

Also what does Ohm's law mean in relation to car audio?  Is it going to limit the output of the system?

What else should I be thinking about?  I'm sure there must be plenty I'm missing out here.

I know this isn't the kind of thing you guys normaly deal with but I'm told there's some real 12v genius' around here.

This is all still in the planning process so it'd be wicked to see what you guys have to say about this :)

- Trolley Dash

why not use a portable radio? bosch makes a jobsite radio/cd player that runs on both battery and ac power. just a thought!  i can tell you just want to make it yourself

Cheers guys, glad to hear the ground isn't gonna be a total headache...

That's it Electrostatic, it's something I wanna get my hands dirty with.  I also want a fair bit of output, nothing ridiculous mind.

So what do you guys recon to a cd player with 2 RCA outputs, one for subs and one for a pair of 6x9's? A 600w amp for the bass and 300w for the 6x9's. Running from a large car battery or maybe a lorry battery depending on the weight of it.  Does this sound like the kind of setup I should be aiming for?

With 900watts in the trolley I'm guessing that would mean I need to mount/hang the head unit with some sort of vibration absorobing material?

Cheers bud, I never thought about seperate chambers, but it makes alot of sense.  It's got me onto thinking about storage of this thing, I have no garage so it's probably going to be a bunch of seperate chambers that are removed from the trolley when it's not in use. 

This is my 'shopping list' I have compiled so far, have I missed anything off?

1 x head unit with 2 x RCA outputs

1 x 400w sub powered by a 600w amp

2 x 100w 6x9's powered by a dual output 300w amp

1 x large car battery

Wiring kit for head unit and 2 amp wiring kits

1 x battery charger

OK, what do I do about fuses?  Do the head unit and each amp require seperate fuses?

Right that's all I can think of for now...

Sound OK?

Right I just realised I don't need any wiring kit for the head unit, just the power wires that come from the back of the unit.

Now what about x-overs?  I had an amp in the boot of my car a few years ago and it had a x-over frquency pot on the back of it, is this the norm with car amps?