Contact Overland Solutions for all your custom modifications and setup for overland travel.               Discover the extraordinary with Compass Expeditions.

Go Back   The HUBB > Technical, Bike forums > BMW Tech

BMW Tech BMW Tech Forum - For Questions specific and of interest to BMW riders only. Questions comparing which bike is best etc go in the "Which Bike" forum.
With more than 58 destinations worldwide, Edelweiss Bike Travel is Number 1 in guided motorcycle tours!
Reply
 
LinkBack Thread Tools Display Modes
  #1  
Old 17 Mar 2005
Gold Member
Veteran HUBBer
 
Join Date: Mar 2004
Location: Gwynedd, Wales, UK
Posts: 252
Alternator brush spring tension

Please can anybody confirm that there should be one full turn of the curly spring holding the brushes against the slip rings on an '82 airhead 280W alternator. There's nothing about it in either the BMW workshop manual (which seems to be crap in a lot of things) nor in the Haynes manual. Having said that, it does look like one full turn and a bit from one of the photos. Can anyone tell me any different, please?

ACTUALLY, I'm fitting a 400Watt replacement from Motor Works, there are no instructions whatever included. I think, however, that an extra half turn would be excessive even though the current will be greater.

Sorry to be a pain with all these questions, I comfort myself with the thought that the answers might be useful to others some day.

Thanks yet yet again

John
__________________
Johnef
Reply With Quote
  #2  
Old 17 Mar 2005
Grant Johnson's Avatar
Administrator
Veteran HUBBer
 
Join Date: Jun 1999
Location: Vancouver BC Canada
Posts: 3,929
one turn it is.
__________________
Grant Johnson

Seek, and ye shall find.

------------------------

One world, Two wheels
www.HorizonsUnlimited.com
Reply With Quote
  #3  
Old 17 Mar 2005
Gold Member
Veteran HUBBer
 
Join Date: Mar 2004
Location: Gwynedd, Wales, UK
Posts: 252
Great!

I've just come across a bit of general information regarding brush pressure since posting the thread from the Little Red Book published by Brook-Hansen, official title 'Installation & Maintenance of Electric Motors' If anyone is interested it's an excellent reference book.

It states that 'as a general rule the brush spring pressure should be 0.2Kg per square cm for speeds up to 2,500rpm and 0.25Kg per square cm at higher speeds.

So. Size of my brushes are 10mm by 5mm, that is, one cm. by a half cm. making the area one half of a square centimetre. As the speed is the same as the engine speed then it will be way over 2,500rpm so the pressure should be 0.25 x 0.5 = 0.125Kg i.e. 125gms or four and a half ounces.

Anyway, after all the calculations it wouldn't be easy to measure in my case. One whole turn will do me fine, Grant.

Many thanks

John
__________________
Johnef
Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 Registered Users and/or Members and 1 guests)
 
Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On



All times are GMT +1. The time now is 05:59.