Norton vs Bob Newby clutch (2016)

The clutch on my 920 is starting to drag very slightly causing problems getting neutral. On removing the plates both the centre & the basket are worn & indented. This I find rather annoying as the clutch has only done twenty thousand miles. The centre is the hardened type. The Norvil basket is supposed to be hard anodised but isn't. I am assured that the latest versions are. The Maney belt drive on my 750 is, as you would expect, hard anodised but I haven't done enough miles on it to know how well it will survive.
So before forking out yet more hard earned cash, is anyone here using a Bob Newby set up. What is it like compared to the Commando clutch which although being light (very important) is a rather on/off affair.

Martyn.

I have BNR on 74 Mk2. I find the clutch to be somewhat grabby and not quite a smooth as I like.
It doesnt have a lot of transition. Guess there is only 3k on it. It has moderately hard lever pull but
as it is a spring type pressure plate, not a diaphragm, you can back off a bit on the adjustment
to lighten the pressure. Not sure how torque you are putting out which would determine it.
On the good side it doesnt need a lot of travel to disengage and it disengages cleanly. It is
very light.
You need to keep the basket bearings lubed and that requires you pull it off.

It really is racing kit and beautifully made. I did have a bit of bother ensuring that the
belt would fit past the stator stud castings. In the future I may mod this area to use
long high strength studs that go directly into the crankcase or something similar.

There are many out there and Bob also makes one for Enfield so they do get street use.

Kenny Cummings uses this on his racer, you need to apply to him for comments.

PM me if you want pix.

I have friend that use them on a sidecar, they need very careful setting up and constant cleaning but they are putting considerably more power through (Imp engine) than a Commando.
Would have thought in road trim that they would be bullet proof, but expensive.

Hi Martyn

I have Bobs kit on a lot of my bikes. They are beautifully made. The clutch runs on ball bearings on a large track & this needs greasing once in a while. Steves clutch is better made than Norvils. However if I were you, I would have a look at NEB. Thiere clutch has the same light spring adjustment & Jawa plates as the Newby but a sealed bearing to boot. All these clutches are light, its only money

Chris

Thanks to you all for the replies. The Newby loose bearing arrangement seems rather crude. Also I wasn't aware that NEB made a Commando clutch. I will give them a call & see if they can supply a 72 tooth drum. The only one listed is 68T which would mean a change of front pulley & belt to keep the 2:1 ratio I like.

Martyn.

I run two New by clutches, one on a 650ss and the other on a 1360 Vincent. The 650SS is his standard type Dommie setup.
I was worried about slippage because the 650SS has been breathed on by Herb Becker. Herb's porting made the stock clutch slip and no matter what I tried it would not hold.
Bob said this Dommie setup had the same plates and springs as the setup he used successfully on his Commando 850 race bike.
It does hold on the SS but it did not initially with a light spring pressure. I had to keep adding pressure to eliminate the slippage. The clutch works great but is a little on the heavy side now that pressure is enough to stop slippage. I would also agree that it does not feather quite as well as some, but smooth operation is not a problem.
It doesn't drag at all.
The Newby clutch in the Vincent 1360 is a one-off he built for that engine, which produces power somewhere in the range between frightening and terrifying. That one doesn't slip even with fairly light spring pressure, but the plates are bigger and there are 7 of them instead of 4? in the Dommie clutch.

Glen

worntorn said:

..........the Vincent 1360 is a one-off he built for that engine, which produces power somewhere in the range between frightening and terrifying........Glen

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Well, if you want to sell it Glen I'll take it off your hands Sorry for going off topic Martyn, but I couldn't resist.

The more I hear the less I like the sound of the Newby clutch. Not progressive & heavy operation are the two things I don't want. The ideal clutch would be something from a modern Triumph or Japanese bike. Not sure if they would be narrow enough though.

Hi Martyn

I have the Newby clutch in my race bikes & I can confirm they are as light as a well set up Commando clutch & dont slip.
On the triples they build up a lot of dust because of the abuse from race starts.
I mentioned the Neb clutch for road use because of the bearing.
Seem to think mine is a 68 tooth drum but as all these firms use blanks I cant see a 72 as being a problem.

all the best Chris

Martyn,

With Barnet plates in a Maney alloy clutch drum the clutch pack will surely be as light as any other? Ad you get the benefit of the diaphragm spring, which is surely the best design for a clutch?

So... What I'm really saying is are you not better off sticking with a Maney belt kit and sourcing the best after market / Commando design, plates etc?

That's the thought process that I went through anyway!

Matchless said:

The more I hear the less I like the sound of the Newby clutch. Not progressive & heavy operation are the two things I don't want. The ideal clutch would be something from a modern Triumph or Japanese bike. Not sure if the would be narrow enough though.

Click to expand...

I'm happy with both my Newby clutches. The Dommie one is a bit spring heavy as mentioned however I have not fitted a Venhills cable to that one yet. That can make quite a difference.
The Newby clutch is incredibly light in weight, it reduced clutch weight by several pounds vs stock dommie, which is not the heaviest (nor strongest) stock clutch.
With the Newby clutch there is no clutch centre. This means no clutch centre weight and also no clutch centre to wear out and cause problems.

Glen

Clearly you are not aware that one great advantage to employing a diaphragm springt compared to coil springs is that for the two types of clutch both giving the same clutch torque capacity the diaphragm spring clutch will give a much lighter clutch lever action at around 555 of that required to free off the coil spring version....NOT MANY PEOPLE KNOW THAT but not many know anything about clutches.......

J. M. Leadbeater said:

....NOT MANY PEOPLE KNOW THAT but not many know anything about clutches.......

Click to expand...

Then it's a good thing that we have you here to enlighten us.

cjandme said:

worntorn said:

..........the Vincent 1360 is a one-off he built for that engine, which produces power somewhere in the range between frightening and terrifying........Glen

Click to expand...

Well, if you want to sell it Glen I'll take it off your hands

Click to expand...

Thanks CJ, but I'm holding on for now ( literally)

Glen

When I said heavy action I said 'moderately' heavy. It isnt objectionable just that I do notice it compared
to my Trident which has a stock diaphragm clutch.
I really only notice the transition when starting, the rest of the time there is no issue.
These are issues you can easily live with when you consider what you are getting in return.

I've used the BNR Commando style clutches with the diaphragm spring for decades on the race bikes, and have been very happy with them. I've never tried his coil spring clutches, but I'm sure the quality is just as good.

Ken

Ken,
I wasn't aware that Bob Newby made the Laycock type clutch. Is yours hard anodised & has it started to become indented ?

I understood Mr Newby only manufactures coil spring clutches because his customers want their clutches to look original.
For information. There is hard anodising and decorative anodising. CORRECTLY hardened pure (99%) aluminium gives a surface hardness of around 800+ Vickets but is totally useless for our belt drive pullleys...... As a comparison 100 ton tensile strength steel has a hardness of around 440 Vickers. The aluminium alloys employed for pulleys is often HE30TF (6082) or if money is not a consideration HE15TF (2014A sometimes still refered to as Duralimium). In the USA one friend uses 6061 for his pulleyts. However the greater the percentage of impurities in an aluminium alloy the lower the hardness of the hard anodised surface thus more expensive HE15TF can give a slightly lower surface hardness than HE30TF. I have my pulleys, when Ia friend twists my arm hard AND LONG enough so I cobble together a belt system for him, hard anodised tro a depth of 0.002 inch of which approx 0.001 is growth on the top of the machined surface and approx 0.001 is in the aluminium alloy thus a pulley grows approx 0.002 on diameter when hard anodised and any oversize on a toothed belt pulley will reduce belt life so I allow for it when the pulleys are toothed. DECORATINE anodising is less a knats cock in thickness and as much use as a protective surfaces for our belt systems as a wet fart...but it looks good and is cheaper. As with everything these days SOME people do a job correctly but many do not. Bob Oswald of QPD in the USA used to do his own hard anodising to ensure it was done correctly but he appears to be keeping a very low profile these days however like many of us he is a old these days and may have retired...... Many decades ago a major UK company gave me suggested hardness values as follows although other UK companies have given slightly different values.
2014ATF and 5083TF 350 - 500 Vickers...6061TF and 6082TF 400-450 Vickers... LM25TF 350-400 Vickers
LM25TF being a cast alloy. Wewll I was toying with having clutch pulleyts cast at the time.....

J. M. Leadbeater said:

I understood Mr Newby only manufactures coil spring clutches because his customers want their clutches to look original.

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Not true. He may no longer make them, but he certainly used to. I have two of them that I bought from him for my race Commando PR back in the late '80s or early '90s.

And they do still look original, as in original Commando diaphragm clutches.

Ken

thats where they came from, i have one on the shelf and no-one knew where they could get one ,i have one for a triplex chain and one for a belt, both for std clutch internals

i used a bob newby for the outfit ,perfect for racing , but will not use one for the road , far too heavy for the arm
a well set up std clutch is sweet and more than adequate for the road imh ,