NEB wet clutch for P11

[Schwany]

I ordered an NEB wet clutch for a 500-750 Norton from British Bike Bits (Burton's Bike Bits) on May 12th. Theoretically it works in a P11 among others that use the old 3 spring AMC clutch. It arrived in 4 days to a Seattle WA USA address. I know it does not have a cush drive. Don't care. I probably won't get around to installing it until June.

I'll need a tool I currently don't have to lock the clutch while I tighten the nut.

It uses 6 small springs. It is lighter than the AMC clutch. The 7 steels are very thin. The 8 fiber plates are a composite product, and very light weight. I don't know what they are made of. I may end up with a different rear hub eventually. Will depend on how clunky it is. Also may not be the best idea for a road bike that will see a lot of miles. Fortunately, mine won't see that many. I hope to get in a couple of long rides, but probably won't break 3000 miles per year.

I'll update the thread as I get further into it.

Pics

 

[Schwany]

Flip side:

Caged ball bearing. Circlips. Not a great pic, but you get the idea.

It is almost an all-aluminum clutch.

No documentation comes with the NEB clutch. It did come with a NEB sticker.

I'll probably torque it down around 55 ft lbs and see how it goes. The bearing arrangement might be similar to the Commando clutch, so whatever torque works for a Commando should work on this clutch. The surface the lock washer for the clutch nut is up against is unusual in that it is a plate held down by 3 countersunk screws. It is gold in color in the earlier pics.

With this clutch the spring adjustment is simple. The spring nuts get turned/screwed down until hitting a spacer that sits inside the spring. With new springs the tension should be equal on the friction plates.

Since there is no documentation regarding anything about the clutch, I will probably put a thin coat of oil on all the steel and friction plates as well as the bearing. I have not decided what lubrication I'll use in the primary with this clutch.

I think these clutches are balanced. There is a dimple in the center that lines up with one of the spring studs, and one on the pressure plate that can be lined up when the pressure plate is installed.

Here's a pic of the sticker with balancing dimples in background.

 

[gnolan]

I doubt that is a balancing dimple. More likely a index mark so the pressure plate locates in the splines correctly.
Is the center section of the hub (the piece secured with the flat head screws) steel or aluminum?

Nice looking piece. Looking forward to hearing how it works.

 

[Schwany]

I doubt that is a balancing dimple. More likely a index mark so the pressure plate locates in the splines correctly.
Is the center section of the hub (the piece secured with the flat head screws) steel or aluminum?

Nice looking piece. Looking forward to hearing how it works.

Thanks for the correction. That is what the dual dimpling does. Nothing to do with balancing.

I was out looking at it some more and you can't just drop the pressure plate down on top without indexing it. The pressure plate has a gear on the bottom that fits down over the center. The center drives the steel plates. Opposite of what the AMC clutch does.

That gold colored (zinc finished?) piece secured with the 3 black countersunk flat head screws right in the middle is steel. The is what the lock washer will be up against when the nut holding the clutch on the main shaft is tightened.

 

[Junglebiker]

Hey! I didn't get a snazzy sticker with mine!

 

[mdt-son]

I was out looking at it some more and you can't just drop the pressure plate down on top without indexing it. The pressure plate has a gear on the bottom that fits down over the center.

The pressure plate has a gear? the interaction with the clutch center is rather short, isn't it? I've never seen that before. Please post a picture of the pressure plate's inside.

The center drives the steel plates. Opposite of what the AMC clutch does.

AMC had this arrangement at first and reversed the design around 1960 (from then on the clutch basket slots actuated the steel plate lugs). For the Commando clutch N-V copied this arrangement, although the number of slots increased considerably. Friction plates have a much lower moment of inertia than steel plates (and subsequently lower kinetic energy when spinning up), and it makes sense to drive them from the clutch centre which has the smaller diameter, provided the clutch basket offers an equal or larger bearing area for the steel plates. This is the case for the Commando clutch basket, not so for the AMC clutch basket I believe. Providing a large bearing area for steel clutch plates with lugs has an immediate weight impact. Steel plates with tangs need a clutch hub with many teeth (i.e., cutouts), so this automatically increases it's diameter and reduces the friction area for a given clutch basket size. Thus clutches need more plates for a given torque capacity.

I am curious to see how your clutch holds up! Did you ask about it's torque capacity in dry condition? I believe this clutch is essentially a dry clutch intended for single cylinder engines, like G80CS and DBD34?

Being part of the clutch basket, I guess the sprocket is made of anodized aluminum as well?

- Knut

 

[Schwany]

The pressure plate has a gear? the interaction with the clutch center is rather short, isn't it? I've never seen that before. Please post a picture of the pressure plate's inside.

I am curious to see how your clutch holds up! Did you ask about it's torque capacity in dry condition? I believe this clutch is essentially a dry clutch intended for single cylinder engines, like G80CS and DBD34?

Being part of the clutch basket, I guess the sprocket is made of anodized aluminum as well?

- Knut

Nobody to ask. British Bike Bits never answered my question 2 years ago about whether it would fit inside a P11 primary. And I have yet to find any support information related to the wet/dry NEB clutch. NEB does not have a website unless it requires a secret handshake to get to. Their clutches may be supported by the race community of which I am not associated.

This clutch is marketed for pre-Commando 500-750cc Norton motorcycles with AMC gearboxes. If I start thinking about it too much I'll probably just put it on the shelf and forget about it. I seriously doubt it will last in a street bike. It is for the most part the same as the race clutches NEB produces for a single cylinder speedway bikes and whatever people do with BSA's. When I saw that set of gear teeth bonded or machined into the bottom of the pressure plate the first thing that came to mind was how the hell does this thing release without tearing those teeth up.

Anywho, I'll go out and take a pic and prepare myself for some more Knut techno gloom and doom.

Here ya go...

 

[Schwany]

Hey! I didn't get a snazzy sticker with mine!

I got that sticker, and it was dropped during shipping or before it was shipped. One of the teeth is a bit flat on top and had some concrete grit embedded in it. I cleaned it up and filed it into a usable shape. Plenty of tooth left, so not a show stopper

 

[Junglebiker]

Regarding dry use: I have an older NEB speedway clutch that was given to me by a friend who wasn't sure what it was. It is very similar to the one we are talking about here, you can tell that they were made by the same people, same style springs, and so on. IIRC, speedway bikes run a powerful single cylinder engine and a clutch, no gearbox, no neutral, just a clutch and a set of final drive sprockets and chain. If I am not mistaken, they all run dry clutches and I know that older ones have the clutch literally completely hanging out there in the breeze. (btw, if you haven't watched speedway racing, I highly recommend it. Lots of it on YouTube. )

My point (just in case it got lost in my rambling) is that the NEB speedway clutch and the one that is sold for use in Nortons are very much alike--if there is a real difference, I suspect it must be in the composition of the friction material, though I really don't know.)

I'd get my NEB speedway clutch out and take pictures, but it's on the other side of the planet from me right now. I think it might have a steel basket and sprocket, but I honestly can't remember. Anyway, here's a link to one that looks a lot like the speedway clutch I have: https://www.frp-uk.com/product/neb-clutch-spare-parts-standardelite-gpv/ (not to be confused with the one that I have for my P11).

 

[mdt-son]

Here ya go...

Thanks. Upon investigation I found a similar feature has been around on 750cc bikes and up since the mid+80's. I guess the design objective is to ensure the pressure plate lifts squarily. It's nicely made!

- Knut

 

[Junglebiker]

I've looked at several other NEB clutches for other applications and it appears as though only the Norton Commando and Atlas applications have the steel plate in the centre around the CS. If this plate were removed, I believe enough threads would be exposed on the CS for the nut to fit. This is the direction I am going to go with mine.

 

[Schwany]

I've looked at several other NEB clutches for other applications and it appears as though only the Norton Commando and Atlas applications have the steel plate in the centre around the CS. If this plate were removed, I believe enough threads would be exposed on the CS for the nut to fit. This is the direction I am going to go with mine.

Sounds good to me. Let me know if you get the spacers off without total destruction. I'm going to take a propane torch to it later.

 

[Schwany]

Finally took the top spacer off. It did take some heat. I was able to get it hot enough with a heat gun. Have not verified if I actually needed to take the top spacer off, but wanted to be sure I could get it off without destroying the allen socket heads if I had to.

Will install the clutch soon. I am not in a big hurry.

Pics

Bearing side.

 

[mdt-son]

Clutch hub is made of anodized alluminum, right? I understand the purpose of the large spacer is to provide a firm surface for the shaft nut to excert pressure upon. This makes sense. By removing the spacer, the shaft nut will act on the alloy and will probably dig in.
Why not machine the hub for the thickness of the small spacer (approx. 1/4" I guess) and reinstall the large spacer? That way you have a solid surface for the nut to act on.

- Knut

 

[Junglebiker]

Clutch hub is made of anodized alluminum, right? I understand the purpose of the large spacer is to provide a firm surface for the shaft nut to excert pressure upon. This makes sense. By removing the spacer, the shaft nut will act on the alloy and will probably dig in.
Why not machine the hub for the thickness of the small spacer (approx. 1/4" I guess) and reinstall the large spacer? That way you have a solid surface for the nut to act on.

- Knut

Beneath the plate is a short steel spacer. The nut bears down on this and it in turn bears down on the end of the splines. Do you really need enough torque to squeeze the spacer out of shape? I did not apply that much torque to mine.
The anodizing is good stuff, very hard. I at one point did a little machining on the inner hub (not really relevant here, so I haven't bothered to discuss it) and that anodizing was tough to cut through.

 

[Schwany]

What he said.

In a standard AMC clutch install there is a thick lock washer behind the nut. That lock washer will be tightened down on the little ring spacer on the NEB hub and possibly dig into the hub a little. The lock washer also digs into the steel AMC hub. I'm probably going to use around 54 ft lbs on the nut. I still need to verify that I can't use the hub with the big spacer as delivered. I don't know why my bike would be any different from any other, but... stranger things

I don't care if it digs into the hub material as long as it holds.

 

[Junglebiker]

@Schwany--btw I am finding that I will probably have to switch to an original style clutch lever assembly--the very nice Domino one I have on there now has a less than optimal leverage ratio which makes for a very heavy clutch. I took 3 springs out and only thus was able to make it feel like a more "normal" clutch (comparable to a cable operated Japanese one).

 

[Schwany]

Good to know. Guess I'll find out how it feels eventually with all 6 springs in there.

I've been using Magura levers for 30 years or so on the P11. The AMC clutch is not a one finger pull with Barnett springs in it, but I'm accustomed to the heavy feel. I don't remember the pull being any lighter with the Norton levers, but maybe my memory aint so good. I did not like the Norton levers regardless, so put Magura levers on it. Most of the other bikes I owned back then had Magura levers on them, so that change made sense to me.

 

[Junglebiker]

Good to know. Guess I'll find out how it feels eventually with all 6 springs in there.

I've been using Magura levers for 30 years or so on the P11. The AMC clutch is not a one finger pull with Barnett springs in it, but I'm accustomed to the heavy feel. I don't remember the pull being any lighter with the Norton levers, but maybe my memory aint so good. I did not like the Norton levers regardless, so put Magura levers on it. Most of the other bikes I owned back then had Magura levers on them, so that change made sense to me.

yeah, I don't care for the Norton ones either, which is why I switched to Domino. Also because the Domino matches my Brembo master cylinder for my front brake. I'm tempted to see what it is like with just 3 springs.

 

[mdt-son]

Beneath the plate is a short steel spacer. The nut bears down on this and it in turn bears down on the end of the splines. Do you really need enough torque to squeeze the spacer out of shape? I did not apply that much torque to mine.
The anodizing is good stuff, very hard. I at one point did a little machining on the inner hub (not really relevant here, so I haven't bothered to discuss it) and that anodizing was tough to cut through.

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