differences between commando and atlas crankshaft (2016)

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pierodn

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Hi All.
What are the differences between commando and atlas crankshaft?.
Are they interchangeable?.
Ciao
Piero
 
pierodn said:
commando and atlas crankshaft?.
Are they interchangeable?.
Click to expand...

Not directly, no.

The Atlas used a single row primary chain, and the Commando has a triplex primary chain.
This means the Commando crank has a longer 'nose' on the output shaft,
to accommodate the much wider triplex sprocket.

I haven't actually tried this though, just eyeballed it.
 
pierodn said:
Hi All.
What are the differences between commando and atlas crankshaft?.
Are they interchangeable?.
Ciao
Piero
Click to expand...

An Atlas crank that had the alternator on the crankshaft is the same as a Commando except for the balance factor.

The earlier crank without the alternator on the crank has a shorter pto shaft. Jim
 
All Atlas's had alternators.

Its that shorter pto shaft on the Atlas that would prevent the Commando triplex sprocket fitting there.

Not to mention that the single row Atlas sprocket fits onto a short taper,
and the Commando triplex sprocket fits onto a (longer) parallel shaft.
hth
 
Where would the triplex sprocket fit ??

differences between commando and atlas crankshaft (2016)


EDIT.
Hmmm, the triplex sprocket will fit onto there.
So is there room for everything to still fit up, as in the Commando. ?
 
1. different balance factor- check

2. Looking at above pix-drive key on taper is 3 oclock..... when pistons/crank throw is UP
commando alternator keyway will be at 6 oclock (down/bottom)
Atlas crank alternator keyway will be at 12 oclock (top/up)

3. not counting the differences within the commando production run
 
Rohan said:
Where would the triplex sprocket fit ??

differences between commando and atlas crankshaft (2016)


EDIT.
Hmmm, the triplex sprocket will fit onto there.
So is there room for everything to still fit up, as in the Commando. ?
Click to expand...

Yes, the triplex sprocket will fit the same -as well as the alternator.

As DD said, the rotor keyway is indexed 90 degrees off, so a new timing mark will need to be made. [just like the Maney crank]. Jim
 
So, dimensionally, the Atlas and P11 and Commando crank are all the same - on the drive side of things.

What do we make of the different indexing for the keyway ?

Is that because on the Commando it gets the mark on the rotor to align with the little degree scale.
Whereas on the P11 and Atlas that wasn't involved, so the keyway had been placed differently. (?).
 
When my crank broke across the big end journal in the 1990's, I ended up fitting an Atlas crank on my previous Commando, and I seem to recall that the threads for the rotor nut were very slightly different. It was a while ago, but can anybody confirm this?
 
comnoz said:
pierodn said:
dynodave said:
1. different balance factor- check
Click to expand...

Hi.
But is usable for a Commando or needs a rebalance?
Thanks.
Piero
Click to expand...

It would need to be re-balanced. jim
Click to expand...
Sorry Jim,
but what means re-balanced.
Let me explain: I go in the shop (they don't even know what a Norton is!!!) and ask to re-balance the crank?????
They know?
Thanks.
Piero
 
The high balance factor of the Atlas crank should be lowered to around 55% called for when using isolastic mounts. Jim



Sorry Jim,
but what means re-balanced.
Let me explain: I go in the shop (they don't even know what a Norton is!!!) and ask to re-balance the crank?????
They know?
Thanks.
Piero
Click to expand...
 
Piero, I personally would never have my crank balanced by a person who does not even know what a Norton is.
 
The vast majority of automotive crank balancers have this capability, however being capable and being able to actually do it on a Norton crank is not the same. Best you ask the crank balancer before you send the crank out if they have ever balanced any Triumph T120/T140 cranks before and what their procedure is. They should ask you to send out all the rotating parts eg con rods, pistons etc and then weight them (and the con rod is weighed on its side so you get the rotating or small end weight not the full weight) . If the balance factor is 50% they should add a weight equal to 50% of the weight of the rotating parts and then statically balance the crank by drilling the flywheel, if you have asked for it to be dynamically balanced they should then spin the crank and drill the sides of the crank so one side weighs the same as the other when spinning.


https://www.youtube.com/watch?v=3tQptjetY4M
 
Send your crank and pieces, I can balance it for the Commando factor. Have been building Norton engines now for over 30 years.
Cheers
 
Make sure your crankshaft will be balanced dynamically as static balancing only will not take care of dissimilar cheeks!
 
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