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Fergus Kyle
Joined: 03 Jun 2007
Posts: 291
Location: Burlington ON Canada
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 Posted: Mon Jul 09, 2007 10:04 am Post subject: FW-Eng ground |
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'lectric Bob:
I'm having trouble setting out the basics. I am using B&C's braid
strip (11-1/2" long) to join Firewall Ground (big Bolt on Froest of Tabs) to
engine block mounting bolt on Rotax 914 - a rare possible spot in the
distance.
The $10 voltmeter says "7.3 Ohms" give or take - and I wonder if
that is in the ball park in view of the braid length - otherwise it's FW to
eng mount which may be worse......
Best of regards
Ferg
Europa A064 914 mono
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Eric M. Jones
Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts
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| Posted: Tue Jul 10, 2007 11:37 am Post subject: Re: FW-Eng ground |
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| Quote: | The $10 voltmeter says "7.3 Ohms" give or take - and I wonder if
that is in the ball park in view of the braid length - otherwise it's FW to
eng mount which may be worse......Best of regards Ferg |
Ferg,
7.3 Ohms is not even close to reasonable. You want 0.0073 Ohms maybe.
Your meter won't measure it. Measuring very low resistances is not for the faint-hearted. Basically you should run high current through the part and measure the voltage drop. This is done quickly (often by a pulse) because the part changes resistance due to heating. Then R equals I/E.
Measuring very high resistances is hard too. They use "meggers" which apply kilovolts, then they measure current through the part. Cool.
The engine ground strap is a needless weak point. Some improvement is possible. "I have a truly marvellous proof of this proposition which this margin is too narrow to contain."
"No one travelling on a business trip would be missed if he failed to arrive."
- Thorstein Veblen
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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net |
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Ivor Phillips
Joined: 16 Jan 2006
Posts: 253
Location: London UK
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| Posted: Tue Jul 10, 2007 1:08 pm Post subject: FW-Eng ground |
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Hi Ferg
I ran a welding cable through the ring mount to one of the two bolt
holes just below where the vacuum pump is fitted, There is good
continuity back to the forest of tabs, and a relatively short cable run,
but long enough to allow for engine movement,
Regards
Ivor
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rvreynolds(at)macs.net
Guest
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| Posted: Wed Jul 11, 2007 2:28 am Post subject: FW-Eng ground |
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Did you "zero" the ohm meter? Are the batteries fresh? Measure a
piece of 18 awg to insure the meter is reading correctly.
Richard Reynolds
On Jul 9, 2007, at 1:54 PM, Fergus Kyle wrote:
| Quote: |
'lectric Bob:
I'm having trouble setting out the basics. I am using B&C's braid
strip (11-1/2" long) to join Firewall Ground (big Bolt on Froest of
Tabs) to
engine block mounting bolt on Rotax 914 - a rare possible spot in the
distance.
The $10 voltmeter says "7.3 Ohms" give or take - and I wonder if
that is in the ball park in view of the braid length - otherwise
it's FW to
eng mount which may be worse......
Best of regards
Ferg
Europa A064 914 mono
|
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http://www.matronics.com/Navigator?AeroElectric-List |
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