Burn-Bros twin plug Marelli rotor
 

An open letter from one Pelican


Re: Burns Bors Rotor

914/6 wrote on 10-07-2005 10:43 AM:
Henry , How is the copper arms on those rotors holding up, Do you think brass would offer a longer lifespan?
I have been invioced by aron to buy , but I was little worried about the coppers lifespan. I would be using in a factory Marelli distributor with jag cap and burns bros rotor saving the oem stuff.
What do you find for wear ?
Thanks Jeff


My response

I believe that the product is very high quality. I would like to tell you that they last forever but we only have a very limited time on this new product. I can say that we have seen no wear issues. But remember that we have very limited test miles. I can say that I take great pride in workmanship and I use these rotors with absolute confidence.

I have an original Bosch cap from a 69 911S that came with copper contacts. I based my decisions on this. I believe the real reason behind the change from copper to brass was strictly one of cost.

Optical pickups ? We're talking about the contacts on the ignition rotor.http://forums.pelicanparts.com/uploa...1128743392.jpg

Henry...as I look at the pic of the rotor, is the vertical stud at the left for the second firing post?
It would be better if instead of that post, there was a ring of metal around the center insulator to keep power on the rail at all times.
I know the spark will jump to the post when it comes to each firing point, but would a carbon brush (or similar) not be better?
Bob

The Burn-bros rotor is a replica of the original Marelli rotor. It works so why try to reinvent the wheel?
Here are some pictures to help clarify how these parts work together.
Burn-bros rotor

http://forums.pelicanparts.com/uploa...1128743392.jpg
Marelli cap
http://forums.pelicanparts.com/uploa...1128793995.jpg
Bosch rotor
http://forums.pelicanparts.com/uploa...1128794031.jpg
Bosch cap
http://forums.pelicanparts.com/uploa...1128794064.jpg

OK...I see the difference.
The Marelli cap has the ring in it, not the rotor, to allow 360 deg contact (or close proximity) for the spark.
I still think the idea is sound...and to prove it...even the Marelli cap has a carbon brush for the center contact.
Both will work, but with a brush contact, the spark would be more even accross the RPM range.
Bob

NO
A carbon brush forced to travel around a long ring would generate a totally unacceptable amount of carbon dust and would suffer from premature failure do to wear.
BTW: the orginal Porsche Marelli rotor did have a carbon contact.
The original Marelli caps had auxiliary holes drilled in them to combat the dust created by the center post.

http://forums.pelicanparts.com/uploa...1128807772.jpg http://forums.pelicanparts.com/uploa...1128807786.jpg

If a carbon brush would not work for longevity...I wonder if the same material that is used in brushes on slip rings in altenators would be OK.
The 2 slip rings in an altenator and their brushes seem to last for a hundred thousand or more.
And the speed of the distributor is half or less than alt speed.
Not giving you the needle Henry...just suggesting alternatives for a longer lasting system.
I tend to look for long term fixes ....just lazy ....LOL
Bob

Hello Bob.

The wheel has been invented some little time now...

The dizzy arm to cap connection has a few volts more than the alternator..

Kind regards
david

Hey David...if you can't re-invent the wheel avery now and then....why bother with life?..LOL
I have been in the electronics industry for..(embarrassed)...more than 40 years.....Wow...time flies when you're having fun.
Begin Rant
We re-invent circuits every day.
It's called progress...or advancement...or change for the sake of change...whatever.
Maybe planned obsolesence would be a better term.
If new ideas are not allowed or looked at....we would still be driving steam cars.
If you asked 25 engineers for a solution to a problem you would get 25 or more answers.
End Rant
You get the idea....not every solution agrees with every person.
Bob

Everybody wanted one, Anyone have one , and is just happy ?
Works good ?
Thank You Henry for your reply.