Pagoda SL Group
W113 Pagoda SL Group => Electrical and Instruments => Topic started by: jfkb2 on September 05, 2013, 02:20:06
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Can anyone please tell me what the copper straps on the backside of the hood latch are for? They look like they are some sort of a ground but I have not found it yet. Does anyone have a part number?
How are they attached or where are they wired to etc. The ones in the picture I have added have a bit of patina, not from my car because I guess I need these and don't know enough about them.
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This was a topic of considerable discussion a few years ago. For purposes of that discussion this it was agreed to call this a "thingy". Supposedly this is part of the radio static suppression. Believe wind across the hood can cause it and this thingy dissipates it.
Gus
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Nice, I had a former life as an RF electronics technician and I could not help but notice the ‘RF ground fingers’ on my W113 hood latch. I don’t have the perfect answer but here is what I do know about them: 1) It is the perfect place to put 'wiping ground fingers.' Each time you open and close the hood, the fingers flex and swipe the contact surface: they self-clean, Elegant! You will notice the copper is clean where it makes contact. 2) It is a radio frequency (rf) ground, with many good contact points, which tells me it’s for a rather low level of current, thus requiring a good contact. We still have to guess why they went to this effort. Typically, it is to keep radio frequency radiation out, or in. My guess is the rf from the ignition coil, wires and plugs is very broadband and the hood is the right size to re-radiate some radio frequencies within the typical German radio bands to the car antenna and this ground eliminated the problem.
I have no insight on if an air stream induced electron charge could be grounded through just the latch and the front hinges.
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Is anyone aware of the availability and the part number for the copper piece?
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The information is great thank you. I too am still looking for a part number and how this is wired.
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The copper strip is NOT wired, just wedged under the plate that holds the latch release.
There is no MB part number for it because it was part of a radio interference suppression kit supplied most likely by Bosch or Becker (but am not sure who supplied it).
It is NLA.
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In the electronics world, this part is known as "fingerstock gasket" and is generally made of brass in high-spring applications, or beryllium copper in low spring applications. The three largest suppliers in the USA are Orbel, Laird, and LeaderTech. While maybe not a 100% match, you could find a suitable replacement from one or more of those suppliers with stock product.
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Michael 'Wikipedia' Salemi ...
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If anyone comes across a suitable example please let me know because I don't have one.
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Michael 'Wikipedia' Salemi ...
Don't know if that's a compliment or insult, so I'll leave it at that.
Suffice to say that in my present line of business I represent one of those companies, so not only am I familiar with the product (actually visiting the factory and seeing it made just in mid July) but of course, the competitors too. It has a lot of applications in anything that needs protection from RF or EMI (radio frequency or electromagnetic interference). You'd generally find it on a control box, let's say, that houses electronics and either generates RF/EMI that the designers want to keep IN the box, or electronics sensitive to EF/EMI and they want to keep it OUT of the box. That's the complex, technical use: simple uses are in things like battery contacts or ground straps, or our own little BST.
In the case of our own little "BST" (brass springy thing, I think we called it some years ago) one of the larger stock profiles might work.
http: //www.orbel.com/emi-rfi-shielding/finger-stock-gaskets
http://www.leadertechinc.com/PDFs/enclosure-shielding-solutions-11/folded-series.pdf FSDS series/folded
http://lairdtech.thomasnet.com/item/askets-and-metal-grounding-products-clip-on-series/clip-on-gasket-series/97-632?
http://omegashielding.com/099-400-00.php
There are other manufacturers, and some of the stock product is carried at distributors, such as:
http://www.mouser.com/Search/Refine.aspx?N=4294907871&Keyword=fingerstock
In manufacturer's terms one piece would be good for several cars. I have taken no measurements, but suggest that one of the products that manufacturers designate for "large enclosures" might work.
All that being said, if there is sufficient interest in getting an exact and precise duplicate made, this is very easy. The hard part becomes how many need it, how many want it, and how much are you willing to pay? Most of the cost would be in set up and soft tooling charges.
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Don't know if that's a compliment or insult, so I'll leave it at that.
A compliment!
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PS: If your car was not delivered with a radio then this item would not be required. Therefore its not on all cars.
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Kevin,
your conclusion is probably correct most of the time but not always.
My 280SL left the factory without a radio but the data card shows code 533: "INTERFERENCE SUPPRESSION WITHOUT RADIO SET",
thus it does have the copper strap. According to docs by the 1st owner handed down to the 2nd (I am the 4th) the dealer in the USA then installed a Blaupunkt radio.
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Wouldn't finding a used one be easier than these other options?
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Well Dan, would you happen to have on? ;D
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Kevin,
your conclusion is probably correct most of the time but not always.
My 280SL left the factory without a radio but the data card shows code 533: "INTERFERENCE SUPPRESSION WITHOUT RADIO SET",
thus it does have the copper strap. According to docs by the 1st owner handed down to the 2nd (I am the 4th) the dealer in the USA then installed a Blaupunkt radio.
Makes sense.
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...and in today's Wall Street Journal was an article on how AM radio stations are becoming mostly static these days anyway...regardless of our BST! :D