LocostUSA.com

Learning how to build Lotus Seven replicas...together!
It is currently October 23, 2018, 7:55 am

All times are UTC - 5 hours [ DST ]




Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: November 15, 2015, 2:19 pm 
Offline

Joined: August 18, 2015, 12:41 pm
Posts: 88
Location: Seattle area (Woodinville)
If you were to build a second car, is there anything that you would do differently that you think that other builders would benefit to learn about. Conversely, is there anything that worked particularly well that you would recommend to others? Please limit this thread to electrical.

_________________
Jerry Henneman

Jack of many trades
Master of unfinished projects
build blog/log at https://jerryslocost.wordpress.com


Top
 Profile  
Reply with quote  
PostPosted: November 16, 2015, 1:28 am 
Offline
User avatar

Joined: June 8, 2010, 8:02 pm
Posts: 584
Location: White Rock, BC, Canada
-my biggest thing is to spend the extra money on a NICE fuse panel. Mine is working so far, but I don't trust it. I'm pretty sure I will eventually get some contact issues from it.
-buy a larger fuse panel than you think you would possibly need. I thought I had, but I still have several in-line fuses
-buy nice braided split loom. It's more expensive, but looks 1000x better, and is less likely to catch fire.
-cable-tie brackets that you can rivet down are awesome.
-trailer wire is a good way to get several wires to the same area very tidy.
-keep as much of the OE wiring you cut out as possible. The wire/connectors will come in handy when you need different sizes etc.
-make sure you have a proper crimper. I knew this well before starting the Locost, but it's important. You should be able to pull hard on a crimped connection and know it's going to stay together.
-positive battery terminal cover is important! I figured I was fine by turning the kill-switch off. Then a throttle cable touched the terminal. Fortunately it did so while I was there, but that could have burned the shop down.

_________________
Build log: viewtopic.php?t=9291


Top
 Profile  
Reply with quote  
PostPosted: November 17, 2015, 12:43 am 
Offline
User avatar

Joined: March 30, 2011, 7:18 am
Posts: 1417
Location: central Arkansas
Rather than looking at a huge tangle of wires in disgust, deal with the wiring one circuit at a time. Install the fusebox, add the brake light switch, wire the brake lights, and watch them work. Then wire up the turn signal switch and turn signals. Then add the taillights. if you get all three of those working without odd things flashing at the wrong time, you're home free.

Keep on circuit by circuit. By breaking it down into a dozen simple circuits the job is much easier.

Make your own wiring diagram. If it gets too cluttered, split things up in multiple pages.

The wiring behind the dashboard can be a mess. Stuff runs forward, back, and to the engine harness. Not too much you can do other than being as neat as possible. Besides a diagram, some pictures are good.

For EFI engines, I treat the engine harness as separate from the chassis harness as much as possible. You'll still have ignition, fuel pump, and maybe instrument wires in the chassis harness, but I keep all the ECM<->engine wiring in its own bundle.

As you run each wire use a turn of masking tape to hold it to the bundle. Keep everything neat. Watch for moving parts, sharp edges, of bulkhead pass-throughs. Remember, if a wire goes through a hole, the hole has to be big enough for the connector on the end of the wire to go through if the harness is supposed to be removable.

I've spent far too much of my life chasing wonky grounds. I now ground the battery to a starter mounting bolt. No need for current to go across paint, rusty bolt threads, gaskets, etc. I ground from there to the chassis. The last time I wired a car, I made a separate "ground harness" that grounded everything to the starter. EEs will probably laugh.

Welding cable insulation isn't rated for automotive use, but it has been... seventeen years since I first used it, and it's still doing just fine.

There are various ways crimp lugs can be attached to battery cable. The neatest way is to find a shop that crimps hydraulic hoses. They have collet crimpers that can make beautiful OEM-style crimps on lugs and terminals. That said, I no longer use them - I use Belden collet terminals. They're cast copper, not lead, and they make them for battery posts and lugs. Just stick the wire in and tighten the collet.

Battery cables MOVE when you shoot a couple hundred amps through them. A friend kept burning battery cables on his Chevy; the cable was a good five inches from the header tube, but every time he turned the key there were sparks. I watched while he tried to start it and watched the wire wiggle like a snake and try to weld itself to the header tube. You need slack between the cable and the starter, but make sure the cable can't touch anything at the limits of its movement.


Top
 Profile  
Reply with quote  
PostPosted: May 2, 2016, 8:17 pm 
Offline

Joined: August 18, 2015, 12:41 pm
Posts: 88
Location: Seattle area (Woodinville)
TRX wrote:
The last time I wired a car, I made a separate "ground harness" that grounded everything to the starter. EEs will probably laugh.

At least one recent commercial airplane uses these. It's called a current return network. Anyone laughing should look up "ground loop".

_________________
Jerry Henneman

Jack of many trades
Master of unfinished projects
build blog/log at https://jerryslocost.wordpress.com


Last edited by JerryH on May 3, 2016, 3:43 pm, edited 1 time in total.

Top
 Profile  
Reply with quote  
PostPosted: May 2, 2016, 11:28 pm 
Offline
Toyotaphobe
User avatar

Joined: April 5, 2008, 2:25 am
Posts: 4718
Location: Fort Worth, Texas
JerryH wrote:
TRX wrote:
The last time I wired a car, I made a separate "ground harness" that grounded everything to the starter. EEs will probably laugh.


The Boeing 787 uses these. It's called a current return network. Anyone laughing should look up "ground loop".



I'm like Sgt. Schultz and "I know nothing!", but I thought a ground loop was a bad thing. At least that's what I've been warned about several times in installing stereo equipment in cars.

_________________
mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 11:21 am 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7551
Location: Massachusetts
Quote:
I thought a ground loop was a bad thing.


Basically it is. This is a difficult subject and books are written about it. It's been a major issue with computer logic and high speed design for decades now. At this level these days we worry about things that I need reading glasses to even see.

The first thing to grasp is simple, just that if electricity is flowing, like water, it is seeking a different potential. So if there is current flowing on a ground wire, it cannot be the same voltage at both ends.

A "ground loop" occurs when you have connections between grounds that are at different potentials. For some reason there are currents flowing on the grounds and when you connect these two grounds, now current will flow thru that connection in addition to how they were flowing before. In a car it's normal to have current on your grounds, they are half the circuit. In a house, it is mostly not normal to have currents on your grounds.

This can be an issue if you are trying to measure things with sensitive instruments, that would include audio equipment (especially turntables), various sensors in general and communications equipment. If you have a record turntable, it measures thousandths of a volt while the stylus follows a groove on a record. If that turntable is plugged into a different branch of your house's system than the amplifier, there is a connection now between the ground shield of it's cable that goes around the house to the chassis ground of the amplifier. If any current runs on this it can put a signal on the wires inside the cable.

For older cars this didn't matter very much. Modern cars are trying to sense things with their ECU's and communicate between various electronic pieces, so they can be sensitive to this.

I know an engineer responsible for an update to a popular and important airplane which entered service in the 70s. More and betterer stuff was required and well into this process he realized the grounding in the plane would not support this. All of us reading this together will not earn enough money in our lifetimes to pay for this cost overrun... :shock:

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 12:36 pm 
Offline
User avatar

Joined: December 17, 2010, 1:24 pm
Posts: 1333
Location: Gainesville, Mo.
With all this talk of ground loops, and airplanes, and ground loops being a bad thing, I kept thinking of a botched landing in a "taildragger"! :wink:

_________________
Mike - Read my story at http://twinlakesseven.blogspot.com/


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 1:01 pm 
Offline

Joined: August 18, 2015, 12:41 pm
Posts: 88
Location: Seattle area (Woodinville)
horizenjob wrote:
A "ground loop" occurs when you have connections between grounds that are at different potentials.... For older cars this didn't matter very much. Modern cars are trying to sense things with their ECU's and communicate between various electronic pieces, so they can be sensitive to this.


So it can be an issue with cars running EFI. But I'm planning to use a separate ground harness primarily because the books and articles I've been reading repeatedly stress the importance of good grounds, and how often in-service electrical problems turn out to be due to bad grounds.

_________________
Jerry Henneman

Jack of many trades
Master of unfinished projects
build blog/log at https://jerryslocost.wordpress.com


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 1:22 pm 
Offline

Joined: July 6, 2008, 11:15 am
Posts: 1050
Location: Cave Creek, AZ
As important in automotive applications is shielding, bonded to ground. All of the sensitive sensors we use now don't like transient currents messing with their own. The magnetic field produced by the positive cable that spins your starter is huge. It'll move the needle on my hiking compass at 12 feet. That magnetic field is absorbed by anything metallic nearby, and if that happens to be an un-grounded wire, the current induced into the wire can do some serious mayhem.

Tom

_________________
Sometimes, I'm as confused as a baby in a topless bar.

My short term memory is absolutely horrible and so is my short term memory.

https://www.youtube.com/watch?v=sG16m2e4O6I


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 4:11 pm 
Offline

Joined: April 1, 2010, 10:26 am
Posts: 348
I re-wired my car with a Painless style harness, much easier and nicer then the stock harness, I was amazed at the weight of the stock harness once I got it removed from the car. When I did the engine swap it was recommended I use new engine and chassis harness, at first I thought this was crazy as a friend used a Ford racing harness for a 302 swap and it was $500. But the new Honda engine and chassis harness were only $120 each. It make is so much nicer when you dealing with totally new wiring not crusty old crap with broken plugs.

Graham


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 7:57 pm 
Offline
The voice of reason
User avatar

Joined: January 10, 2008, 4:47 pm
Posts: 7551
Location: Massachusetts
Quote:
the importance of good grounds, and how often in-service electrical problems turn out to be due to bad grounds.


Good connections need to be gas tight. If they are not that good then there will be oxides formed, corrosion. Soldering and crimping both provide such a connection. Fresh lock washers will also do that where the sharp metal edges dig in. I don't think the car chassis is a bad conductor, it is likely better than a copper wire - but it is important to get a good connection to it.

Being gas tight implies it will also resist humidity. Water vapor is actually very difficult to guard against. A water molecule is smaller than oxygen and nitrogen molecules for one thing.

If you are using connectors ( automotive ) you should be able to see where the metal is marked by a sharp edge. If it doesn't do that anymore you probably need a new connector. They are not rated for many cycles and if they are corroded they may have lost that edge.

_________________
Marcus Barrow - Car9 an open design community supported sports car for home builders!
SketchUp collection for LocostUSA: "Dream it, Build it, Drive it!"
Car9 Roadster information - models, drawings, resources etc.


Top
 Profile  
Reply with quote  
PostPosted: May 3, 2016, 9:23 pm 
Offline
User avatar

Joined: July 17, 2015, 1:56 am
Posts: 158
Location: Morrisville, PA
If you look at your donors schematics carefully ( or megasquirt ) you will note that most sensors are powered by the ecu and grounded at the ECU. If you crack open the ECU you will find all chassis grounds are filtered by capacitors. Also the ECU has additional filtering and conditioning on the 12v supply in it to prevent noise from the alternators rectifier.

The knock sensor itself being a piezo crystal is very easily overcome by noise as it produces voltage from the vibrations of the motor and the computer needs to be able to read them clearly.

Grounding common or like grounds, well at least from where i worked in the RF field is call single point grounding. Then you had chassis and earth depending on requirements and design.

:cheers:

_________________
-STu

There is no shame in defeat, so long as the spirit is unconquered

My Build Log


Top
 Profile  
Reply with quote  
PostPosted: May 5, 2016, 12:46 pm 
Offline
User avatar

Joined: October 24, 2008, 2:13 pm
Posts: 3648
Location: Carlsbad, California, USA
This grounding harness thing is very interesting, but how does it prevent the loop? Even if you have many grounds leading to one place on the chassis, isn't it possible to loop locally anyway since the potentials will still vary all along the harness?

Maybe someone can insert a URL to a concise Internet article that would show some examples and answer some questions?

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


Top
 Profile  
Reply with quote  
PostPosted: May 7, 2016, 8:08 pm 
Offline
User avatar

Joined: July 17, 2015, 1:56 am
Posts: 158
Location: Morrisville, PA
Lonnie-S wrote:
This grounding harness thing is very interesting, but how does it prevent the loop? Even if you have many grounds leading to one place on the chassis, isn't it possible to loop locally anyway since the potentials will still vary all along the harness?

Maybe someone can insert a URL to a concise Internet article that would show some examples and answer some questions?

Cheers,


Wiki..
[url]
https://en.wikipedia.org/wiki/Ground_lo ... tricity%29[/url]

_________________
-STu

There is no shame in defeat, so long as the spirit is unconquered

My Build Log


Top
 Profile  
Reply with quote  
PostPosted: May 8, 2016, 4:30 pm 
Offline
User avatar

Joined: October 24, 2008, 2:13 pm
Posts: 3648
Location: Carlsbad, California, USA
@stuie84
Thank you, sir!

Cheers,

_________________
Damn! That front slip angle is way too large and the Ackerman is just a muddle.

Build Log: viewtopic.php?f=35&t=5886


Top
 Profile  
Reply with quote  
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 16 posts ]  Go to page 1, 2  Next

All times are UTC - 5 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 3 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
POWERED_BY