Well that won't work. Anyone have a ruler handy?

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Well, the Allazurra triple clamps won't work.

Please see this Norton 850 triple clamp picture:

Well that won't work. Anyone have a ruler handy?


Norton 850 triple clamps have a offset of around 2.78" (about 70.5mm for those metrically inclined).

My lovely light weight aluminum Alazzurra clamps have an offset of about 1.79" (about 45.5mm for ... yadda yadda).

The Alazzurra clamps would increase my fork trail by ~ 1.0" (about 25mm .. etc.).
Voila - instant 'Great Lakes Freighter loaded with iron ore' handling.

Would as many people as possible with an alternate motorcycle (70's Ducati 750 GT, etc.) and a ruler amuse my efforts by taking a couple of measurements from their triple clamps?
Info required: aproximate fork tube spacing, fork tube diameter and offset.
See picture - if measurements are close - please reply with bike, year, and measurements.

Newer sport bikes probably won't work as they have less steering head rake and thus require even less offset than the Alazzurra clamps.

If anyone has installed different clamps already and kept their 'wonderful Norton handling', please send me some details.

(My other options are a CNC custom job or weld up 'bosses' on a set of Norton clamps and have both clamps machined to fit straight 35mm tubes).

Thanks in advance for everything,
 

L.A.B.

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teeb said:
Norton 850 triple clamps have a offset of around 2.78" (about 70.5mm for those metrically inclined).

The Norton lower clamp offset amount ought to be slightly less that the upper one? As the 850 (ANG) clamps angle the fork legs from the steering stem line, the 850 steering stem and fork legs do not run parallel to each other, the front axle/spindle centre being moved back by about 1 inch or so as a result.
Have you taken this into consideration when measuring up the different clamps? Would they hold the forks parallel to the stem?
If so, then you may find that the relative positions of the wheel axle may not be that different, and the amount of trail may not be increased as much as you think?
 
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Hi L.A.B.
A very significant and interesting point; thank you very much!

I have not looked into this yet, but will as I had read about the difference between the 750 and 850 triple clamps, but couldn't see much difference (I could only see a small difference in the offsets), I am planning to take my frame, 850 clamps, a friends 750 clamps and a pair of new tubes into work and set them up on the surface table and measure the differences.
Kind of like an episode of 'mythbusting'.

Yes, clamps with slightly different offsets will change trail considerably.
As a mechanical engineer that has been designing automated machinery for ~12 years this 'different offset - top clamp to bottom clamp' solution shocks me a bit. But then again, this is the British motorcycle industry.

If the 850 offset is different from top clamp to bottom clamp, this means the bored holes in the lower clamp must be bored at a slightly different angle to the hole for the center yoke (steering axis).
Also, the tapers machined in the top yoke must be bored at a slightly different angle to the center yoke (steering axis) to accept the taper at the top of the fork tube.
Producing parts this way adds significant expense and set up time compared to three holes bored parallel to each other.
Checking if the angle is correct during quality control would be more difficult as well. (Oooppps, I wrote something bad – did I really say quality control?).
If I came up with this solution at my company, I'd be smacked with a hockey stick (Canadian eh :wink: ).

Maybe Norton was cheap and had lots of cast steel 'not machined' 750 clamps stacked in bins that would be thrown into the smelter 'cause the offset would be wrong for the ‘new 850 model’. Instead of simply casting new clamps with a different offset to maintain the trail and wheel base, they bored holes at differnt angles.

Well I’ll have some fun on the surface table.

If they are different in offset, I guess I shouldn’t be surprised.
I took apart my Brembo/BMW F08 calipers today to clean them out and measured the pistons with a 1-2” 1/10,000 micrometer – they have 1.5” pistons (well exactly 1.4932”). Hmmm, imperial pistons in BMW calipers and Japanese master cylinders… …

On a similar note, my 850 clamps do not have 'ANG' cast in the bottom.
 

L.A.B.

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teeb said:
On a similar note, my 850 clamps do not have 'ANG' cast in the bottom.

As far as I know, all 850 clamps/yokes should have ANG cast into both top and bottom clamps to be correct for the 850 frames, which have the 1 deg. difference in head angle from the 750 frames?
Are there any numbers cast in to these parts?
Are you certain your frame is an '850' one?
---------------------------------------------
A rough check of my own 850 (Mk3) top yoke (as it is fitted on the bike) appears to show that it may have more offset than yours, by around 1/4" but without removing it to measure it properly I couldn't guarantee that.
 
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Hi L.A.B.,
Yes, that is very possible as the VIN plates can be swapped easily.

Well, I have access to 4 basket cases (my bike would be included as one basket case - even though no baskets are involved - well except for the owner perhaps) and I'll note which frames are which style and the same for the triple clamps - and note the casting marks - then get back to you with the results.

Thanks a million,
Steve.
 
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i used ducati 500 parrallel twin yokes with shortened stanchions and ducati 18 inch weels works great
 
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O.K., so is there a noticable difference in handling between the 750 and the 850? If so, which way?

Maybe Norton was cheap and had lots of cast steel 'not machined' 750 clamps stacked in bins that would be thrown into the smelter 'cause the offset would be wrong for the ‘new 850 model’. Instead of simply casting new clamps with a different offset to maintain the trail and wheel base, they bored holes at differnt angles.

I would bet money on that being the case. I always get a kick out of the way Norton switched the disc brake from the right fork to the left by reversing the leg with the caliper brackets. I've asked some motorcyle guys as to why most single discs are on the left side. No one seems to know why. Anyone have a good explanation? With the master cylinder being on the right side it would seem the disc would be on the right side also.
 

L.A.B.

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JimC said:
O.K., so is there a noticable difference in handling between the 750 and the 850? If so, which way?

The 850 setup gives better high-speed stability.

Maybe Norton was cheap and had lots of cast steel 'not machined' 750 clamps stacked in bins that would be thrown into the smelter 'cause the offset would be wrong for the ‘new 850 model’. Instead of simply casting new clamps with a different offset to maintain the trail and wheel base, they bored holes at differnt angles.

JimC said:
I would bet money on that being the case.

I would have to disagree, as changing the angle of the drillings would require the hole centres to be moved substantially. It would be possible to do it that way with one out of the two yokes I suppose, but only if the other was a new part of different dimensions?

In any case I don't see how they would have got the 850 'ANG' lettering and different casting numbers onto the 750 items, as these are cast-in and not stamped on the parts?

Production of the 750 model also continued alongside the 850 model for around 10 months, and as far as I know those 1973 750 Mk V frames/yokes did not have the 850 frame/yoke geometry?

So I doubt there would have been any great surplus of 750 yokes left over that would not have actually been required?
 
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I guess I would of lost my bet. I was basing my assumption on the way Norton had done most other things, like the aforementiond disc switch. The casting letters and numbers prove your case, L.A.B.
 
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This is lynxnsu's 750 MkV (well that's what it started out as) fitted with Ducati 500 Parallel twin Marzocchis

It looks as if I've been losing a fight with ImageShack so I've reloaded a couple of pictures. Not sure if they're the originals though.

Well that won't work. Anyone have a ruler handy?

Well that won't work. Anyone have a ruler handy?

Well that won't work. Anyone have a ruler handy?
 
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Whoa, hey hold on a minute there…!!!!

Whoa, hey hold on a minute there… :eek:
Lynxnsu and 79x100 – HEY WOULD YOU DO ME A HUGE FAVOUR?
This is what I am referring to.
Those forks are off a 500 Ducati/Cagiva Pantah – No?
As I don't think there were a lot of the 500 parallel twins around...
From the picture they appear to have way more offset than my 650 Alazzurra triples.
Would you be so kind to measure the center to center distance between the fork tubes (I think the tubes themselves should be 35mm tubes the same as the Alazzurras) and the offset (the distance between the tubes and the center of the spindle/bearing axis) like the picture I posted to start this thread? :D
I would be very,very greatful as most Japanese yokes seem to have less offset (although similar tube diameters)
:wink:
 
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Teeb,

I'll hassle the man to take some measurements.

The forks are definitely Parallel twin but i'm not sure if they're from a valve spring or desmo model (not sure if they differed but he'll know).

There were quite a few of the earlier valve spring models rattling around Europe until they ritually disembowelled themselves, then there were quite a lot of chassis parts but I don't think they're so easy to find now.
 

L.A.B.

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The (apparently reversed) forks and wheel are of the type fitted to the parallel twin GTV / Desmo models:

Well that won't work. Anyone have a ruler handy?


Well that won't work. Anyone have a ruler handy?
 
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Thanks for the time and effort L.A.B. and 79x100.
What are you names - I've read them before in the postings, but don't want to mix either of you up.
If those are 35mm Marzocchis similar to those fitted to the early Alazurra, they are supposed to be quite good. A fellow in CA (I think) associated with the Yahoo Alazzurra site has won quite a few races with them on a Alazzurra and prefers them to the later 38mm (?) as the internal damping system changed for the worse with the 38mm (or so I have read, but not experienced).
I think I'll pop over to visit a friend that has a Pantah race bike and take a good look at his front end, triple clamps, etc.
Did I mention you guys are a great help? :D
 
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forks used are indeed those shown for duc twins but stanchions have to be shortened or let them slip through the yokes .last solution is easier also to provide place to fit clocks but does not look so neat. also by shortening them they look as if they were made for the bike.distance between centres is 17cm and offset is 6 cm Handeling is 15o% as quite a few people in IOM have experienced just look where the slides stop and compare with your Roadholders The overlap is MUCH bigger.Added bonus is the double and small(read light)disc set up I converted them to floaters and swapped the calipers to the back for handling KEEP MODIFIING
 

Ron L

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lynxnsu,

With the Marzocchi forks and triple trees, what final rake angle does this give? What modification did you do to the adapt the trees to the Norton frame? Cut the steering stem or add spacers? Steering bearings?

Did you adapt the rear wheel from the Duc vertical twin also?

It's a very nice looking setup and add to that the better handling!

Neat looking exhaust system, too.
 
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well that won't work ...

Lynxnsu, where is your oil tank?
teeb, Years ago, being bored and having several bevel drives and associated parts available, I installed the triple clamps w/forks and wheel with no adverse problems. Seems that the bearing dimension is 25 mm for the Duck parts and the Norton's is 1 inch, basically a drop-in, with proper spacer from McMasters and the usual fiddling required to do anything like this, and the addition of running the Duck rear wheel. Hated to re-install on Duck bevel at later date.
 
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O.K. now things are rolling....

Yeah Lynxnsu, sweeeeettttt!!!!!!!!
So I'm aiming for a similar setup (Cagiva/Ducati stuff).
Alazzurra cast front wheel, Brembo disks w/Brembo calipers, Marzocchi Forks.
Alazzurra rear wheel with REAL FAT RUBBERS FOR CUSHIONING the changeable drive sprocket, same Brembo brakes.
No more inner tubes!!!! Wheel rim sizes are close to the Commando.

So you get 170mm between fork tubes and 60mm offset?
The Alazzurra has 195mm between tubes and 45.5mm offset. So there is a difference in offset, but not much!
Where did you get those pipes? I always imagined that the pipes would go through there, but hadn’t yet arrived at the point of making my own. I’ve seen similar on trials bikes – you can’t drag them unless you’ve done something really bad!

Ron and Katescottageiom, I haven’t gotten to adapt the triples yet (thanks for the info Kates.. I am so looking forward to the end results) as the Alazzurra donor kept the steering stem. The Ally bike was turned into a racer and I bought the entire front and rear end (less some bits like the stem). The Marzocchi yokes are cast Aluminum, so the stem was just pressed out and pressed back into the YZF1000 front end that went on the race bike. (So if anyone has Ally/Pantah stem or triples available...)

Lynxnsu - oil in frame, no? Did you expand the top tube?
(I figure the Commando top tube will hold only about 1.7 liters – not enough).

I threatened to, so I did take various Commando triple clamps to work and measured them:
Bike
Geoff 750 #1 Top Offset 2.781” Bottom Offset 2.781” Difference 0.000”
Geoff 750 #2 Top Offset 2.776” Bottom Offset 2.776” Difference 0.000”
Geoff 850 #1 Top Offset 2.759” Bottom Offset 2.685” Difference 0.074”

0.074” over 5.75” gives about 0.74 degrees (5.75” is the aprox. spacing between bearings in fork bearing races and where the offset measurements were taken).

Did I mention my original 850 triple clamps are twisted? :cry:

Whew, that's a letter. :roll:
 
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Teeb, pm sent. Lynxnsu doesn't seem to have got around to replying but I have a couple more pictures from him. :)

These are the fork yoke mounting components.

Well that won't work. Anyone have a ruler handy?


Rear swinging arm is Mk111 Commando. Exhaust system is a one-off.

Well that won't work. Anyone have a ruler handy?
 
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Re: O.K. now things are rolling....

teeb said:
Lynxnsu - oil in frame, no? Did you expand the top tube?
(I figure the Commando top tube will hold only about 1.7 liters � not enough).

There is some extra capacity

Well that won't work. Anyone have a ruler handy?
 
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