NEB wet clutch for P11

Joined
Apr 22, 2020
Messages
1,418
Country flag
The surface is hard all right, but the base material still has the modulus of aluminum. The designer of the clutch overcame the problem of dissimilar materials by enlarging the pressure area acting on the aluminum. In their design, only a small fraction of the pressure load acts on the spline ends. Essentially, the small washer is there to ensure the large washer stays flat. It's a bit complicated to explain - load distribution is a product of area and modulus of the backing material.

In your loading scheme, virtually all pretension load and running load will transfer via the nut and small spacer into the splined ends, and there is very little pressure on the hub pushing its splines towards the tapered end of splines, which is the real design intent.
I fear you will see abnormal wear and clutch drum "wobbliness" before long. I guess you will just have to monitor the clutch assembly as miles stack up.

- Knut
I'm thinking you are wasting your time in the message box and should be writing a dystopian science fiction novel. ;)

On the plus side of this experiment, nothing gets modified to the point that going back to the AMC clutch can't be done easily.

Given how little I actually ride the P11, I doubt I'll have any issues with the NEB clutch other than banging the gears some without any cush rubber in the clutch center hub or my rear wheel hub. Shifting into first from neutral might be a bit crunchy.

By the way, I think the AMC clutch also fastens with the nut pretension load on the shouldered end of the spined shaft. I'll be checking on that soon. If it actually tightened up on the taper spline cut, I would need a clutch puller to get the AMC clutch off. However, the clutch slides on and off after the nut is removed. The main difference is the little spacer is not part of the NEB hub like it is on the AMC clutch. It actually free floats in there. So I suppose it is possible that things could loosen up and trash the alloy splines if not torqued down tight. I'm not going to worry about it.
 

mdt-son

VIP MEMBER
Joined
Jan 19, 2012
Messages
1,501
Country flag
I'm thinking you are wasting your time in the message box and should be writing a dystopian science fiction novel. ;)
Haha! Engineers should always conceive what can go wrong in a particular design. It helps avoid some pitfalls, but not all.


- Knut
 

mdt-son

VIP MEMBER
Joined
Jan 19, 2012
Messages
1,501
Country flag
By the way, I think the AMC clutch also fastens with the nut pretension load on the shouldered end of the spined shaft. I'll be checking on that soon. If it actually tightened up on the taper spline cut, I would need a clutch puller to get the AMC clutch off. However, the clutch slides on and off after the nut is removed. The main difference is the little spacer is not part of the NEB hub like it is on the AMC clutch. It actually free floats in there. So I suppose it is possible that things could loosen up and trash the alloy splines if not torqued down tight. I'm not going to worry about it.
No, it doesn't. See picture in #1:

The spider has provision for using a puller (the theaded boss).

- Knut
 
Joined
Apr 22, 2020
Messages
1,418
Country flag
No, it doesn't. See picture in #1:

The spider has provision for using a puller (the theaded boss).

- Knut
The NEB is fastened up against a shoulder at the front of the splines the same way the AMC is. That picture is deceiving. I'm sitting here looking at the clutch and the mainshaft. The rear of the clutch does not hit the 4th gear sleeve shoulder. If it did it would not function as a clutch. It's close though. It butts up against a step shoulder on the front clutch side of the mainshaft splines. I could circle where it butts up in the picture, but have more important things to do. Basically the AMC clutch is fastened the same way that the NEB will be fastened. No sense for NEB to reinvent the wheel. Not to put too fine a point on it, but if you had both clutches in hand like I do, you'd see how it all works. It's also possible that we are on the same page in different books. ;)

The NEB clutch does not want to slide on the splines like the AMC clutch does. My guess is a machine work error though and not an intentional tight fit. It should slip right over the splines. I have to find what is hanging it up and clean it up with a file. I don't want to beat it into place, because I'd never get it off.

A clutch puller is not necessary for the AMC clutch on my P11 even though the hub center is threaded.
 

Junglebiker

VIP MEMBER
Joined
May 16, 2018
Messages
204
Country flag
I wondered about that. Mine is the same way, I have to tap it on with a hammer and then very carefully pry it off to remove it. Perhaps it was a slip fit before the hard anodizing?
 
Joined
Apr 22, 2020
Messages
1,418
Country flag
I wondered about that. Mine is the same way, I have to tap it on with a hammer and then very carefully pry it off to remove it. Perhaps it was a slip fit before the hard anodizing?
I thought similar about the anodizing, but don't know enough about anodizing (without using google) to have a clue how much difference it could make to the dimensions. Anodizing is a pain to remove that much I know. Currently I'm trying to get the NEB clutch on and off by hand without a hammer with the inner case removed.

This is the kind of stuff that always bugs me about so called performance upgrade parts. They often require too much fiddly hack work to make fit. I don't have a machine shop at my disposal, so everything I do is hack work.

What were you carefully prying the clutch off with?
 

Junglebiker

VIP MEMBER
Joined
May 16, 2018
Messages
204
Country flag
Pry bars, but I would apply a little pressure, rotate 100 some degrees, apply a little pressure, rotate, apply, rotate, apply, etc. Took forever.
 
Joined
Apr 22, 2020
Messages
1,418
Country flag
I ended up making a simple puller (not pictured) for the NEB clutch so I could install and remove the clutch repeatedly when test fitting for the right size shim to prevent the back of the clutch hub from hitting the 4th gear bush sleeve, or whatever that sleeve is. When torqued down to no more than 35 ft lbs without a shim the hub hit the sleeve locking up the clutch and making it direct drive and nonfunctional. It won't be nonfunctional when I get done. The shim does not go behind the hub. It is actually inside the spline ID of the hub and butts up against the spacers in front of the hub. The puller uses the three threaded bolt holes on the front of the hub. It's a piece of 5/16th aluminum with three holes in it, some spacers, and three long M5 bolts that screw into the hub and pull the clutch forward enough to take off by hand. I could make a sophisticated one that bolts up to the hub and uses a larger center bolt arrangement to push against the end of the mainshaft, but what I did was the quickest to make. It also causes the least harm to the mainshaft. That's my theory anyway.

NEB wet clutch for P11


NEB wet clutch for P11


The tight fit on the splines I was whining about earlier is not a machining error. The clutch goes on smoothly with a nut and wrench. The tight fit should prevent the alloy clutch hub splines from getting beaten up by the steel mainshaft or wobbling once torqued down. To get the clutch on the mainshaft during the test fit process, I pushed the clutch on by hand until there was enough thread showing inside the hub to start a spare shouldered alternator rotor nut on top of a big washer. Once the clutch was up far enough on the mainshaft I could use the standard clutch nut against the NEB spacer stack on top of the hub.

This NEB clutch as delivered would not work on my P11 if torqued to 50 ft lbs, which I consider about right for an alloy final drive component with a nut the size used for the clutch. It can be installed and work with less torque on the nut and feel tight and secure, but I'd rather be sure. I'll be using a star washer similar to what is used on the rotor and not the big OEM lock washer. Not enough thread showing for the big lock washer.

Today I'll find out if the primary chain run aligns with the clutch and engine sprockets. If not, I may not be using this NEB clutch. I've been messing around with it too long already, and the wear life of an alloy sprocket is short enough, but if the chain run is not aligned it will be really short lived. The old AMC clutch works without all the drama.
 

Junglebiker

VIP MEMBER
Joined
May 16, 2018
Messages
204
Country flag
I'll remember your puller solution. If I had known that I was going to be installing/removing it so many times, I would have gone ahead and made something better than what I had. But each time I installed it I thought, "There! That's sorted." Only to realise a little while later, "oh. That needs to come off again." This has been how I have been learning about Nortons! Endless repetition.
 
Joined
Apr 22, 2020
Messages
1,418
Country flag
I was about to give up on this NEB clutch install, when I said to myself F... it, I'll make a 5/16th thick shim and stuff it in there to see how it goes. Reason for going big is I could not get the primary chain on the clutch chain gear because the NEB clutch chain gear is not a 1/4" offset gear like the AMC clutch. It is completely flat. There was not enough clearance between the gear and the inner primary to get a chain on. I needed another 1/8". I don't know how Junglebiker got so lucky, but this clutch was not even close to working on my P11 as delivered. I have the chain gear in the same alignment location now as the AMC clutch, so in theory it should line up with the engine sprocket.

Negatives are the NEB clutch is out there on the mainshaft splines further than it should be. Fortunately, it weighs less than the AMC clutch. I may be able to get away with it. If not, it will be a nasty destructive lock up when it breaks the mainshaft. Remains to be seen. I also have to use a thinner nut. Current plan is to cut my spare rotor nut shoulder off and use the remaining nut. Bigger nut, but a thinner nut. Also it is very likely that oil in the primary will splash up and out of the hole in the inner primary for the mainshaft. It does anyway, but it now has a full 1/4 inch of open space between it and the back of the clutch chain gear. On the plus side the hub bearing will get plenty of oil on it.

I do have reservations about continuing with this clutch, but as they say no risk no reward. I've come this far, I might as well try it. Yippee
 
Top