When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I've got a small amp (75Wx4 RMS) sitting around, so I was looking to put it in the trunk. I've seen lots of people mount theirs on the back of the rear seat, on top of the spare tire, or even on a shelf hanging down from the rear deck
The thing is, I don't want the amplifier taking up valuable cargo space in the trunk, and fold down my rear seats a lot to put my bike in the back of the car, so the back of the seat isn't going to work (imagine the bike snagging the power wire ).
A drop-down shelf from the rear deck makes the most sense, since the space between the speakers probably won't get in the way of loading anything in the trunk. Problem with the shelf idea is the controls are on the top of the amp, so I can't make adjustments with it in place. I could take the amp off the shelf, make adjustments, and put it back on, but where's the fun in that?
Instead, I got some inspiration from a pull down knife rack we have in our kitchen
1 is what to make it out of. I bought a bunch of aluminum L-bracket from Home Despot, which will work for the arms, but for the shelf and the top mount, I'm going to need something that comes in sheets, which they don't carry in any kind of thickness that's going to have some strength. Anyone an experienced metalworker out there that might have a good idea for what sort of gauge aluminum I'd need for this and where a good supplier might be?
2. How to make it latch closed. The springs will do a lot to take the weight, but they're not going to work over bumps. The kitchen version uses magnets, but that's not a good idea near a piece of audio electronics.
So I see that you can get aluminum diamond sheet, 1' x 1', the heavy duty kind, which is 3/32" thick. That, mounted to three L brackets on the sides... or four, why not... should be sufficiently strong to do the job. If you're worried about it, two sheets back to back, with one small bolt/fastener in the middle, will definitely do the job with the L brackets involved.
I also had this thought of a restaurant supply and one or two aluminum sheet pans... They'd be thick enough...
Just spitballin' here. I wouldn't want to get too thick unless you were gonna use it for heat sink purposes, and then I'd probably be using active cooling... aka a couple of fans on the amp itself. Maybe a 120MM 12VDC for a PC, and mount it. I did that on the Mark VIII when I did the amps back there. Tray thing was already in it, I repurposed it, and then had the amps cut off, so I put in some fans and tada problem solved.
And it's thick enough at the 9" or so square/rectangle you're using, plus those angle brackets, it'll do just fine, I'd say. Maybe need standoffs to keep the amp itself off the plastic, or insulate it with a bit of aluminum sheet, but it'd definitely work for that pull down shelf...
However, to be honest? Given that upper bracket design, I'd be going with sheet steel. Stronger for the forces involved. You can bend that upper bit into shape not a problem. Sand it, clean it, shoot it with etching primer, shoot it with paint, done. In the trunk it won't rust, it's not going to be much weight... And thinner overall too. And cheaper, because the pricing on even the aluminum sheet pans seems... stiff.
As far as how to close... on one corner, or both, put a long bolt and use a thumbscrew setup. Or similar. Make it so you have to actively secure it. It's hanging from the package tray, and gonna go over bumps. You'll want it completely secure, and straps and such ain't gonna cut it. I'd say 'wing nut' but they're not pretty. Maybe a little bit of all thread, then a hex joiner that a PC thumbscrew can go in so it looks kinda decent. Or maybe some Zeus clips... Oooh, these things: https://www.ebay.com/itm/26448707494...kcid=28&chn=ps
Yeah. I'd do those.
I'm sure some of that you thought of, and/or rejected for various reasons, but there I go. Hope it helps anyway! I like this project, looking forward to seeing how you figure it all out!
So I see that you can get aluminum diamond sheet, 1' x 1', the heavy duty kind, which is 3/32" thick. That, mounted to three L brackets on the sides... or four, why not... should be sufficiently strong to do the job. If you're worried about it, two sheets back to back, with one small bolt/fastener in the middle, will definitely do the job with the L brackets involved.
I also had this thought of a restaurant supply and one or two aluminum sheet pans... They'd be thick enough...
3/32 (13 gauge) would probably do the trick, I was thinking I'd want at least 1/16 (16 gauge) for stiffness. The sheet pans are an interesting idea, and you can get them in different thicknesses, although 16 ga is $40.
Originally Posted by houtex
Just spitballin' here. I wouldn't want to get too thick unless you were gonna use it for heat sink purposes, and then I'd probably be using active cooling... aka a couple of fans on the amp itself. Maybe a 120MM 12VDC for a PC, and mount it. I did that on the Mark VIII when I did the amps back there. Tray thing was already in it, I repurposed it, and then had the amps cut off, so I put in some fans and tada problem solved.
And it's thick enough at the 9" or so square/rectangle you're using, plus those angle brackets, it'll do just fine, I'd say. Maybe need standoffs to keep the amp itself off the plastic, or insulate it with a bit of aluminum sheet, but it'd definitely work for that pull down shelf...
Heat sinking shouldn't be an issue, it's a class D amp which is very efficient and runs pretty cool. I had this one under the seat of my truck, and in a hidden compartment in the back of my old Focus (completely enclosed) and never had an issue w/ overheating. Problem w/ acrylic is I find it to be too brittle. With the stress of 2 lbs hanging from it, I think the screw holes would start cracking. What I could use is an Ikea cutting board. I've used them on projects like this before. It's Polyethylene which is pretty easy to work with, it's stiff, durable, and best yet it's only $3 (I already have a stack of 4 of these sitting on my shelf for these kind of projects).
For the bottom shelf I probably could easily go the plastic route, for the top bracket I think I really have to go with sheet metal, given the stresses on those hinges. On the kitchen version they're pretty stiff (although I'm sure a lot of that is the springs).
Originally Posted by houtex
However, to be honest? Given that upper bracket design, I'd be going with sheet steel. Stronger for the forces involved. You can bend that upper bit into shape not a problem. Sand it, clean it, shoot it with etching primer, shoot it with paint, done. In the trunk it won't rust, it's not going to be much weight... And thinner overall too. And cheaper, because the pricing on even the aluminum sheet pans seems... stiff.
You might be right on that, I've been reading up on bending aluminum and you really have to be careful about what alloy and temper you're working with before you try to bend it. The stuff I bought from Home Depot (6063 T5) isn't especially great for bending and you have to anneal it if you don't want it to split (I have experience w/ that bending some homemade brackets for my motorcycle). Steel cuts a lot easier too (aluminum tends to gum up your cutting wheels). Maybe I'll make another run out to the store to see what gauges they have.
Originally Posted by houtex
As far as how to close... on one corner, or both, put a long bolt and use a thumbscrew setup. Or similar. Make it so you have to actively secure it. It's hanging from the package tray, and gonna go over bumps. You'll want it completely secure, and straps and such ain't gonna cut it. I'd say 'wing nut' but they're not pretty. Maybe a little bit of all thread, then a hex joiner that a PC thumbscrew can go in so it looks kinda decent. Or maybe some Zeus clips... Oooh, these things: https://www.ebay.com/itm/26448707494...kcid=28&chn=ps
Yeah. I'd do those.
I'm sure some of that you thought of, and/or rejected for various reasons, but there I go. Hope it helps anyway! I like this project, looking forward to seeing how you figure it all out!
Lee Valley Tools, they are a Canadian Company but do have American Stores and a big online site. They have a hardware section and get a lot of things in that you cannot find elseware including drop down hinges. It may be worth the search, I built a cookbook holder that dropped down similar to what you are doing, with a kit from them. Oh, I like the idea by the way it looks good.
So... I helped? Looks like maybe I helped the thinkin' process anyway.
I like those latches, btw. And that cutting board makes a LOT of sense to me!
Yep, I decided to try out some 22 gauge steel from Homeless Despot and it worked pretty good. Steel is a lot easier to work with.
Here's progress so far. This is just kind of mocked up, got to make the bottom platform, there's a lot of edges to clean up, might round some corners so stuff doesn't catch on it when I'm putting things in the trunk. I might also add a spacers on the shorter arms and notch the longer ones so they can nest together a little more.
Yeah, sorry VGM, have to agree. I just see that thing bouncing and rattling all over the place, maybe even unlatching itself.
That one on the amazon link is interesting, need to see if I can find pics of it unlatched so I can see how it might work on this one. Might be able to use it on the sides to lock the arms to the upper housing.
You're gonna need to put some plastic/nylon/teflon washers between things to reduce some of that (lookin' at you, arms on the side pivot points), and then rubber feet/strips are everywhere and can be strategically placed to fix those issues.
You're gonna need to put some plastic/nylon/teflon washers between things to reduce some of that (lookin' at you, arms on the side pivot points), and then rubber feet/strips are everywhere and can be strategically placed to fix those issues.
Just a thought. Keep it goin'!
Yep I was thinking about that, also thinking I'll use some dynamat on the top of the mounting bracket to keep it a little bit isolated too
Another thought...Nylon bushings might help keep the aluminum and Steel isolated from each other too. As we all know from our factory hoods, steel and aluminum don't play nice together
Yeah, sorry VGM, have to agree. I just see that thing bouncing and rattling all over the place, maybe even unlatching itself.
That one on the amazon link is interesting, need to see if I can find pics of it unlatched so I can see how it might work on this one. Might be able to use it on the sides to lock the arms to the upper housing.
No worries. The idea just popped into my head. Thought Id mention it, but I didnt think about it rattling, thats a good point! If I find something else Ill post it.
Not much new to report, been doing some motorcycle stuff lately. But I got a bunch of #6 and #8 nylon washers from Lowes that put a stop to any kind of rattling. Tonight I'm going to take it all apart and grind/file all the sharp edges and look at where's the best place to bolt it to the underside of the rear deck.
Still thinking about latches. Maybe one of the easier ones is to lock the arms to the housing with a pin (preferrably something spring loaded)
I didn't center things as good as I thought I did, so looks like I've got a rubbing issue too
Hm. Watching this develop... this came to mind: If you pin/secure the tray up, then release it, won't the weight bring it crashing down to the stops? I'd be wondering if some sort of dampener wouldn't be advisable.
'Course, that's an admittedly pansy idea for rugged men and women what understand that tray and all and know to care beful and support it when unsecuring it, but the problem is kids and idiots abound what might also get their hands on it, possibly... I should know, after all, as I am one.
Just a thought. Dunno how you'd even address that to be honest....
/Maybe I just go back to lurkin'...
//I'm stealing this, btw, when you're done and happy with it. Just wanted you to know that.
2/10/21, 02:46 PM
I like this project, looking forward to seeing how you figure it all out! 
Looks like maybe I helped the thinkin' process anyway. 
