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Tech Forum : Pneumatic piston to replace trunk lid springs?

- BMW E21 Community
   - Tech Forum
      - Pneumatic piston to replace trunk lid springs?
MayanArch   Posted Sunday, Sep 23rd 3:54am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1392
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
How about removing those springs that go across the back of the trunkc, under the rear deck?

Those are in the way of installing speakers of any quality or size. They get in the way of the magnet.

I feel like cutting them off, and replacing them with pneumatic springs.....like the ones that are used in the E30 hood.

Any observations or insight welcome.

How big would those pistons need to be?

Where to place them?

ichiwan2   Posted Sunday, Sep 23rd 5:40am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 294
   
Kuala Lumpur, Malaysia
BMW320/6(e21)
What kind of sound system are you planning on? Have you considered putting boxed subs instead of hanging them on the parcel tray?

Am using Focal 11 inch sub in box which is good enough for me.

MayanArch   Posted Sunday, Sep 23rd 5:56am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1395
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
Dont want just subs. I am a bass player. I want to hear natural mid range bass like 6" and 8" speakers can give.....unubstructed.

Thump, thump is fine for the bass that your ears cant hear....but your body should feel. Not good for bass that is supposed to immitate a bass guitar.

melloh   Posted Monday, Sep 24th 1:40am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 602
   
California, USA (San Jose)
1980 320is, 1991 318is
A few years ago "plate" speakers were suggested to use in the stock placement with no sheetmetal cutting. Would this help?

http://www.crutchfield.com/S-f20MYUWQzGf/cgi-bin/ProdGroup.asp?search=plate&osp=&skipvs=T&g=51400

MayanArch   Posted Monday, Sep 24th 5:44am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1398
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
melloh wrote:
A few years ago "plate" speakers were suggested to use in the stock placement with no sheetmetal cutting. Would this help?

http://www.crutchfield.com/S-f20MYUWQzGf/cgi-bin/ProdGroup.asp?search=plate&osp=&skipvs=T&g=51400


Those go well up front next to the glove compartment....but if you want any sort of mid range bass you need 6.5" and larger woofers.

PYLE makes some pretty shallow woofers....but still. You really only have about 1.5" there...and no one makes a magnet that small.

I had my daily driver on plates in the front, and 5.25" coaxials in the back and I could not stand the shrill of the music. Too much treble and no mids or lows whatsoever.

Bill in MN   Posted Thursday, Sep 27th 7:17pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 181

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i
Mayan

I pulled the springs from both hood and the trunk lid so as to install pneumatic tubes. I've not gotten around to getting them in yet but somewhere in my shop I've got the specs. If I can find them I'll forward them to you. Trying to reload the hood springs is a bitch and a half, prompting me to go with alternatives.

If you didn't want to mess with the geometery of putting the pneumatics in, you could always go with a generic prop rod that pivots and clips to the underside of the lid.

MayanArch   Posted Friday, Sep 28th 2:39am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1400
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
Bill in MN wrote:
Mayan

I pulled the springs from both hood and the trunk lid so as to install pneumatic tubes. I've not gotten around to getting them in yet but somewhere in my shop I've got the specs. If I can find them I'll forward them to you. Trying to reload the hood springs is a bitch and a half, prompting me to go with alternatives.

If you didn't want to mess with the geometery of putting the pneumatics in, you could always go with a generic prop rod that pivots and clips to the underside of the lid.


Yeah, its the geometry that I cant work out in my head. I am thinking it is a matter of buying a piston....making a bracket to support the base....and then finding where it would hit the trunk lid fully open. Right?

The problem is where the piston mounts would go. This is tricky for the Baur as the underside of that rear deck holds the targa top racks.

The hood seems much easier to do than the trunk lid. I am not at all bothered by the hood. Its that rear deck that I want to free up.


chupchup   Posted Tuesday, Oct 2nd 3:40pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 251
   
Singapore
320m20
The Infinity Reference 6412cfp n 6412cfp looks pretty good for the front of the car. the 60W should be able to handle my power amp nicely.

Bill in MN   Posted Wednesday, Oct 3rd 12:09am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 182

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i
Mayan

Something worth considering....

When you're top's lowered, rear speakers will be totally useless. The rear deck is completely covered by the lowered top.

MayanArch   Posted Wednesday, Oct 3rd 4:22am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1402
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
Bill in MN wrote:
Mayan

Something worth considering....

When you're top's lowered, rear speakers will be totally useless. The rear deck is completely covered by the lowered top.


You are 100% right. However, in Miami's 3 days of winter (3 days of 57 degrees or higher)...that will be a problem.

Otherwise, your car is your air conditioned refuge!!!!!!!!!!!

Bill in MN   Posted Wednesday, Oct 3rd 3:05pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 183

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i
Hmmmm a convertible and you can't even use it

It's just the opposite up here. I don't recall the last time I drove the e21 with the top up.

MayanArch   Posted Wednesday, Oct 3rd 11:34pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1403
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
Bill in MN wrote:
Hmmmm a convertible and you can't even use it

It's just the opposite up here. I don't recall the last time I drove the e21 with the top up.


I exaggerate. Miami from November to April is paradise. There is no better place on Earth.

However, the heat and the humidity the rest of the year is brutal. Every year I am in awe as to just how hot and humid it can get.

I was in Minn one winter. It was the ONLY time in my life I was indoors for more than three days straight. Not even when I got operated.

My brother and I got sick of being in a hotel room, so we decided to go see hockey game. We lowered the window to pay for parking, and the window froze in the down position.

Now I know why you guys have bridges spanning between your buildings downtown.

Bill in MN   Posted Thursday, Oct 4th 3:44am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 184

Minnesota USA
1988 735, 1986 535 turbo, 1981 Baur 323i
I live in the northern part of the state. We usually have a period every winter when it doesn't get above -20 during the day and usually hovers at about -40 at night. Oddly enough, a person gets used to it. My old super eta used to run like a champ in the frigid temps.

Getting back to your original post, I looked all over for the measurements on the struts and can't find them. I'm guessing my fab guy has them in his shop and they're probably buried by now. I'll ask him when I run into him in the next few days.

wilbryant   Posted Wednesday, Dec 19th 9:39pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 57

GA
82 Baur 323, 95 M540
Mayan,

When I set out to install a stereo system in my Baur I encountered the same problem. I'm a real music lover listing to mostly jazz and Blues I appreciate the rich sounds of mid bass. So my approach to this problem was to build and install some custom kick panels. I was able to come up with panels to accommodate 5" MB Quarts mids and a 6" mid bass speakers. And in the trunk I installed two 8" solobraic sub in a small custom box that sits low enough to still allow me room to store the top. I also have enough room to store gulf clubs as well.

I have a clean rich sound that I can hear with no problems going 75 mph down the highway with the top off and rear down.


MayanArch   Posted Thursday, Dec 20th 9:32pm [Edit] [Quote] [IMS] [View car]
Member
Post nr. 1474
   
Florida, USA
Baur E21 2.7 1982, Baur E30 318i 1985, 323i 1978
wilbryant wrote:
Mayan,

When I set out to install a stereo system in my Baur I encountered the same problem. I'm a real music lover listing to mostly jazz and Blues I appreciate the rich sounds of mid bass. So my approach to this problem was to build and install some custom kick panels. I was able to come up with panels to accommodate 5" MB Quarts mids and a 6" mid bass speakers. And in the trunk I installed two 8" solobraic sub in a small custom box that sits low enough to still allow me room to store the top. I also have enough room to store gulf clubs as well.

I have a clean rich sound that I can hear with no problems going 75 mph down the highway with the top off and rear down.



Will,

Share pics please. This sounds interesting, although I already pulled off the trunk mechanism springs and installed the 6x9 speakers in the rear deck.

I am still looking to figure out a way to get the pneumatic pistons to replace those springs.

Either that, or normal slinky style springs to actually pull those trunk lid arms ..... and hence the lid up.

wilbryant   Posted Friday, Dec 21st 2:46am [Edit] [Quote] [IMS] [View car]
Member
Post nr. 58

GA
82 Baur 323, 95 M540
No problem I will gladly post some pictures, I have already put in a request to have my download size increased. In the mean time you can send me an IM with your personal email and I will send you my construction pictures as well.


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