Author Topic: Crankshaft Main Bearing Journal  (Read 1461 times)

Online Nourish

  • A's Best Friend
  • ***
  • Join Date: Aug 2013
  • Posts: 124
  • Karma: 0
Crankshaft Main Bearing Journal
« on: 30.01. 2014 10:01 »
Does anyone know the size and tolerance of the drive side main bearing diameter as mine has worn and it is at the moment being welded up for refinishing - unless that is that there is a better bearing to fit?
Cheers

Offline Briz

  • A's Best Friend
  • ***
  • Join Date: Apr 2013
  • Posts: 209
  • Karma: 7
  • West Norfolk UK
    • Custom cycle developments
Re: Crankshat Main Bearing Journal
« Reply #1 on: 30.01. 2014 10:52 »
It ought to be an interference fit for a 30mm ID bearing. No viable alternative to 30mm.
So I'd guess 1.182 - 1.1825"
Take along a bearing; whoevers doing it should be able to work from that.
How worn was it? unusual for the drive side to wear. I guess the bearing was spinning on the shaft?

Online Nourish

  • A's Best Friend
  • ***
  • Join Date: Aug 2013
  • Posts: 124
  • Karma: 0
Re: Crankshat Main Bearing Journal
« Reply #2 on: 30.01. 2014 11:36 »
I havent a bearing to fit as yet but the journal had loads of center punch marks on it !
What is the bearing number?

Offline Briz

  • A's Best Friend
  • ***
  • Join Date: Apr 2013
  • Posts: 209
  • Karma: 7
  • West Norfolk UK
    • Custom cycle developments
Re: Crankshat Main Bearing Journal
« Reply #3 on: 30.01. 2014 12:55 »

Online Nourish

  • A's Best Friend
  • ***
  • Join Date: Aug 2013
  • Posts: 124
  • Karma: 0
Re: Crankshaft Main Bearing Journal
« Reply #4 on: 30.01. 2014 14:47 »
Why does a British manufacturer back in 1948 use a metric bearing - surely there must of been an imperial equivalent ?

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 5057
  • Karma: 48
Re: Crankshaft Main Bearing Journal
« Reply #5 on: 30.01. 2014 15:56 »
Nourish,

To hold my main bearing in place, I've just used Loctite 641 retaining compound for the first time on my engine still on the bench. So, I can't swear by the performance, but this was the approach recommended by various forum members I respect and, also, by my machinist.  According to Loctite, the 641 is good for gaps up to 0.006", but they have other blends for up to 0.020" (wow!). Be sure to check out page 16 in the product information. Here is a link:

http://www.henkelna.com/us/content_data/326508_9294_LT5021_Retaining_Brochure_FINAL.pdf

Richard L.
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Offline Briz

  • A's Best Friend
  • ***
  • Join Date: Apr 2013
  • Posts: 209
  • Karma: 7
  • West Norfolk UK
    • Custom cycle developments
Re: Crankshaft Main Bearing Journal
« Reply #6 on: 30.01. 2014 16:24 »
Why does a British manufacturer back in 1948 use a metric bearing - surely there must of been an imperial equivalent ?

You'd have to ressurect old Bert Hopwood and ask him!
Nearest imperial equivalent is 1 3/16" (1.1875) which is .0064" bigger than 30mm. Dont complain! metric is almost always cheaper than imperial!

Metric stuff was getting to be in general use even then; the bore & stroke measurements of your A10 are metric. The 30mm main bearing was used on Nortons & Triumphs too, although early Triumphs had 1.1875" shafts, which still causes confusion.

Online RichardL

  • Outside Chicago, IL
  • Wise & Enlightened
  • *
  • Join Date: Nov 2007
  • Posts: 5057
  • Karma: 48
Re: Crankshaft Main Bearing Journal
« Reply #7 on: 30.01. 2014 18:04 »
This inspired some amusing historical research.

I'm thinking that, after WWII, BSA wanted to design-in bearings for which they could choose more sources than, I assume, just SKF. The rest of Europe, except Ireland, had already completed, or was close to completing, metrication before the war. If they were going to choose a standard for something that they couldn't make themselves, it made sense to choose what most of the rest of the industrialized world were using. (Emphasis on "me thinks".)

Richard L. 
Plan on signing up for the world-wide 2020 DISTINGUISHED GENTLEMAN'S RIDEon September 27, 2020 (if it's not cancelled and we are free to move about by then). Watch website at https://www.gentlemansride.com for details.

Online muskrat

  • Global Moderator
  • Wise & Enlightened
  • **
  • Join Date: Jul 2009
  • Posts: 8253
  • Karma: 106
  • Lake Conjola NSW Oz
    • Shoalhaven Classic Motorcycle Club Inc
Re: Crankshaft Main Bearing Journal
« Reply #8 on: 30.01. 2014 19:31 »
But they went back to imperial for the A50/65.
Cheers
'51 A7 plunger, '57 A7SS now A10CR,  '83 CB1100F, 88 FXST .
Australia
Muskys Plunger A7

Offline trevinoz

  • Newcastle, N.S.W. Australia.
  • Wise & Enlightened
  • *
  • Join Date: Jul 2006
  • Posts: 2901
  • Karma: 67
Re: Crankshaft Main Bearing Journal
« Reply #9 on: 30.01. 2014 20:56 »
And they used the same imperial bearing on the long-stroke as the early A65.

Trev.

Online morris

  • Wise & Enlightened
  • *
  • Join Date: Aug 2012
  • Posts: 1593
  • Karma: 24
  • Antwerp, Belgium
Re: Crankshaft Main Bearing Journal
« Reply #10 on: 30.01. 2014 21:17 »
And there's more metric than just the crank bearing......
'58 BSA A 10 SA
'52 BSA A 10 Plunger
'55 MORRIS ISIS
The world looks better from a motorbike
Belgium

Online chaterlea25

  • Wise & Enlightened
  • *
  • Join Date: Jun 2009
  • Posts: 3253
  • Karma: 47
Re: Crankshaft Main Bearing Journal
« Reply #11 on: 31.01. 2014 00:17 »
Hi All,
I have often wondered about the imperial /metric bearing reasoning or lack there of  *eek*
For that matter why are the bore and stroke of all the Uks makers metric??
I know that veteran Triumphs used metric main bearings (MC22) along with lots more manufacturers
What is really puzzling is when there are metric and imperial bearings on the same engine crank, Rudge and BSA singles for example
Norton ?/ BSA Gearboxes are the same. ON some Burman gearboxes there are bearings with a metric OD and imperial inner (or the other way round?)

Fkd if I know  *????* *????* *????*

John
1961 Super Rocket
1963 RGS (ongoing)

Offline Briz

  • A's Best Friend
  • ***
  • Join Date: Apr 2013
  • Posts: 209
  • Karma: 7
  • West Norfolk UK
    • Custom cycle developments
Re: Crankshaft Main Bearing Journal
« Reply #12 on: 31.01. 2014 12:34 »
Its probably down to the ins & outs of corporate ordering.
A canny sales rep from a bearing company comes up with a good deal on 10,000 bearings and the design engineers are 'encouraged' to incorporate them....