Belt drive / alternator question

Fast Eddie · Jun 1, 2014

Gents,

My bike is fitted with a Norvil belt drive kit, that I'm very happy with and intend to re-use.

Whilst assembling the primary side, I noticed the alternator rotor nut only grabs by a few threads and I'm not comfortable with this given the torque that it requires.

It looks to me that my set up uses the stock rotor spacer, but as I have a pulley that's wider than the sprocket (in the centre portion) it must therefore be pushing the rotor further outboard than standard.

So, I'm planning on slimming the spacers down a tad. And will have to play with the rotor and stator spacing, but it looks like I need to move the rotor inboard further than the stator, meaning that it wont sit centrally anymore, so, one question I have is, how important is it to centralise the rotor to the stator when spacing them out? (I'm not referring to the rotor / stator air gap, but there position relative to each other).

And my second question: before I go re-inventing the wheel, what have other Norvil belt kit users done about this?

pete.v · Jun 1, 2014

Fast Eddie said:
Gents,

My bike is fitted with a Norvil belt drive kit, that I'm very happy with and intend to re-use.

Whilst assembling the primary side, I noticed the alternator rotor nut only grabs by a few threads and I'm not comfortable with this given the torque that it requires.

It looks to me that my set up uses the stock rotor spacer, but as I have a pulley that's wider than the sprocket (in the centre portion) it must therefore be pushing the rotor further outboard than standard.

So, I'm planning on slimming the spacers down a tad. And will have to play with the rotor and stator spacing, but it looks like I need to move the rotor inboard further than the stator, meaning that it wont sit centrally anymore, so, one question I have is, how important is it to centralise the rotor to the stator when spacing them out? (I'm not referring to the rotor / stator air gap, but there position relative to each other).

And my second question: before I go re-inventing the wheel, what have other Norvil belt kit users done about this?

I faced off my rotor to except a belleville wacher. I feel there is a lot of meat there and you could machine enough to give yourself adequate threads to secure the rotor. This, along with your shimming, should get you where you need to be.

It seem there is much give in the relationship on how far inboard or outboard the rotor is to the stator and still get full function.

1up3down · Jun 1, 2014

Eddie, that seems odd to me as I have a Norvil belt and the alternator nut is threaded fully.

Maybe something is hanging up from your initial installation.

I would remove the alternator nut, rotor, stator and belt from pulley to figure what is not fully home.....

Nortoniggy · Jun 1, 2014

I'm pretty sure I left the spacer out altogether and just used a largish washer between sprocket and rotor. The rotor being inline with the stator isn't critical but on mine I made new spacers to fit behind stator on it's mounting posts to get it a bit further inboard. The stator is still a bit outboard of the rotor but it charges ok. I don't think it lines up very well with the original setup anyway.

Ian

Nortoniggy · Jun 1, 2014

Found a picture of mine

pete.v · Jun 1, 2014

I am sure you know this but what the heck. That rotor spacer can go on 2 ways, the wrong way and the right way.

bwolfie · Jun 1, 2014

I also found this when I fitted a 40mm wide belt kit on my alloy bike. My solution was to just make a longer nut for the rotor. Problem solved.

Fast Eddie · Jun 1, 2014

pete.v said:
I am sure you know this but what the heck. That rotor spacer can go on 2 ways, the wrong way and the right way.

Pete, you should never assume that I know anything! This is my first Commando, and I didn't know that, and I now know that my spacer isn't standard, as its symmetrical!

The current spacers do align the stator and rotor nicely... Just too far outboard.

1up, the pulley is seated very nicely, this engine has been striped totally and I'm just in the reassembly stage and am happy with the woodruff key fit etc.

I even thought about omitting the spacer altogether and butting the rotor directly up to the pulley, but I'm uncomfortable doing that (just doesn't seem right) and then I'd have the misalignment issue.

Bwolfie, Norvil sell a longer nut specifically for the 40mm belt application! I have one coming so I can pay with it, but I only have a 30mm belt so want to understand why I seem to need it! Plus I'd like to get the weight as far inboard as I can if possible (less stress on crank etc).

Here's my pulley and spacer, anyone see any obvious errors?

Dances with Shrapnel · Jun 1, 2014

It does not look like much key available to engage the alternator rotor as it is now.

Any chance you could cut down the center spacer on the crankshaft and three outside pedestal spacer equally to bring the rotor and stator back further without fouling the belt?

I have yet to run a belt and alternator so not much help here.

Fast Eddie · Jun 1, 2014

Dances with Shrapnel said:
It does not look like much key available to engage the alternator rotor as it is now.

Any chance you could cut down the center spacer on the crankshaft and three outside pedestal spacer equally to bring the rotor and stator back further without fouling the belt?

I have yet to run a belt and alternator so not much help here.

I agree, theres not much key there!
I think I could move the stator inboard 3mm.
The spacer shown is 7.9mm, which I could remove altogether.
That would put everything as far inboard as possible and have the stator / rotor misaligned by 4.9mm.
What say you fine chaps to that, would that amount of misalignment be ok to their functionality?

texasSlick · Jun 1, 2014

Someone (I think it was Ludwig), recently posted he moved the rotor in and out of the stator on a test jig while measuring the amp output. He found the output to be rather insensitive to the rotor's position. from his data, I surmise you could "steal" 1/8 to 3/16 inch.

However, the special nut suggested by Bwolfie, may be the easiest solution.

Slick

pete.v · Jun 1, 2014

Fast Eddie said:
Here's my pulley and spacer, anyone see any obvious errors?

I will go out on a limb. Doesn't that spacer go inside of that gold plate as it would with the RGM unit?

I realize that it is a different but......

Fast Eddie · Jun 1, 2014

pete.v said:
Fast Eddie said:

Here's my pulley and spacer, anyone see any obvious errors?

Click to expand...

I will go out on a limb. Doesn't that spacer go inside of that gold plate as it would with the RGM unit?

I realize that it is a different but......

Not on this one Pete, that pulley is a solid lump of alloy behind that plate!

pete.v · Jun 1, 2014

Then why the spacer? What do you see as its function? The RGM unit is probably narrower and the rotor ride right against the plate. The spacer behind the plate supports the plate on the RGM which allows the rotor to butt up flush.

Looking at the parts in the kit, I do not see this spacer.

texasSlick · Jun 1, 2014

pete.v said:
Then why the spacer? What do you see as its function? The RGM unit is probably narrower and the rotor ride right against the plate. The spacer behind the plate supports the plate on the RGM which allows the rotor to butt up flush.

Looking at the parts in the kit, I do not see this spacer.

PeteV makes a good point....why not bin the spacer? Also, you can use different length spacers behind the stator to move it in/out if you need to keep the rotor and stator aligned.

Slick

Hobot · Jun 1, 2014

30 mm belt, no spacer but thin hard back up washer and standard end nut.

Fast Eddie · Jun 2, 2014

hobot said:
30 mm belt, no spacer but thin hard back up washer and standard end nut.

Ok, having looked at Hobots pic, and the Norvil parts kit on line, and at mine again, I suspect you chaps have correctly surmised that the design intent here is to have no spacer between the pulley and the rotor at all.

Why did I think it needed one? Three reasons:
1. Because it had one, so I assumed it should be there!
2. Without it, even with slimmed down stator spacers, the rotor will not be central to the stator, although I now realise this is probably a non issue
3. It looks to me to be a better idea to clamp the rotor tightly on the steel centre part only, although I can still achieve this with the thin- ish washer replacing the current spacer.

Will have another look now...

Keith1069 · Jun 2, 2014

I have the same belt drive for many years now. The spacer I use is appx. 060". Engagement of the nut is about 5/16", not correct but enough. Attached pic shows more clearly and you can just see the end of the crank. I'm guessing the spacer is for alignment? Does the clutch sit out so far that a thick spacer is needed? Can you thin down or reduce those on the gearbox shaft?

Fast Eddie · Jun 2, 2014

Thanks for all the input guys, it helped me approach this from a sensible perspective.

I've ended up with a 1mm (040" ish) spacer between the pulley and the rotor and by using a new, standard style star washer and nut, I've used almost all of the available thread on the end of the crank.

Now I've just got to hack off approx 3.7mm off of the stator spacers to get the stator as inboard as possible whilst leaving approx 1mm clearance between it and the pulley.

Sorted!

pete.v · Jun 3, 2014

Fast Eddie said:
Thanks for all the input guys, it helped me approach this from a sensible perspective.

I've ended up with a 1mm (040" ish) spacer between the pulley and the rotor and by using a new, standard style star washer and nut, I've used almost all of the available thread on the end of the crank.

Now I've just got to hack off approx 3.7mm off of the stator spacers to get the stator as inboard as possible whilst leaving approx 1mm clearance between it and the pulley.

Sorted!

I would not be so concerned on how much the stator covers the rotor. As far as cutting down the spacers, it is important that they are equal in thinkness as to preserve the relationship between the rotor and stator and eliminate the chance for interference. If you get the stator on the cockeyed, it's bound to touch the rotor somewhere and make it hard, if not impossible, to get .010" clearance all around.

I think the clearance is the key to good efficiency from the alternator.

Belt drive / alternator question

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