Sturdier triple clamps

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The change in the top yokes from tapered to parallel is probably connected to the change from drum to disc brake on the Triumphs.
 
prob mostly old tech vs new,

new folks mostly could care less about old tech,

not to mention, vast improvements can be done cheap, in comparison
 
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Quote. Set up properly, there is absolutely nothing wrong with the way a Norton handles. If there is a problem, fix what you've got, don't go searching for an answer to a non existent problem.
That's the same thing you hear from the BMW guys.

Yet there are problems with the Roadholders-topping and bottoming out for example. They are an old design
First introduced in 1946 and then modified in 1953, Roadholder fork construction stayed relatively constant until the end of Norton production in the mid-1970s. Quote

Comparing even a well set up BMW with a well set up Norton is laughable! I have a Lansdowne conversion in my front ens and it doesn't display any of the nasty traits of BMW front ends. Th Hyde fork brace for Nortons is as ugly as sin and does absolutely nothing for a Norton. Comparing Triumphs and BMWs to a Norton and then saying that converting the forks to parallel tubes will cure a non existent problem doesn't cut it with me I'm afraid. You're barking up the wrong tree.
 
All t140s with a disc front end have parrellell fork tubes as far as I know they are also wider than the conical hub front ends
So not interchangeable unless you change the whole lot
Can't see it being very difficult to make a pinch type top yoke for a commando ,but don't forget the top yoke on an 850 is de raked by 1°
If you have a 750 you could probably modify two bottom yokes,and fit clip ons just to try it out, and let us know
Personally I don't use Norton forks but I'm sure they can be made to work very well
 
mdt-son said:
In your case, twisting has nothing to do with the yoke / upper triple tree (clamp). Twisting is due to biaxial bending of fork tubes (L+R).
The parameters are: Fork tube length from lower triple clamp to wheel axis; Modulus of fork tube material (normally around 200 GPa); Inner diameter of fork tube; Outer diameter of fork tube.
My thinking is, if you experienced a "signaficant improvement" by fitting a Betor fork (which I don't know anything about), then there are either geometry differences between the fork tubes as noted, or a weakness in the bearing support of the triple tree in the headstock. If you send me the respective fork tube data, I will calculate the bending stiffnessess of both.

-Knut
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As I understand it Knut, the biaxial bending you are referring does not seem to consider the restraint of the axle and the outer tubes - admittedly this will not be much on a Roadholder due to the rather small diameter of the axle. However, if an effective fork brace was fitted, this would give more support to the inner tubes in bending, effectivly reducing the unsupported length. This effect would of course be reduced by the clearance between the inner tube and the bushes in the outer tube, so again, probably not a lot of cop here.

Actually, it's amazing that the Roadholder works so well, considering how floppy it is :)
 
Pete Komarek
By twist do you mean holding the front wheel between your knees and try and turn the handlebars or is the front noticeably flexing riding along?
I have standard Mk 3 steel upper and lower clamps holding standard Roadholders with Maxton cartridge internals.
Can,t twist them at all doing the above and bike handles great at all road and (occasional) track speeds, solo or fully loaded.
 
SteveBorland said:
As I understand it Knut, the biaxial bending you are referring does not seem to consider the restraint of the axle and the outer tubes - admittedly this will not be much on a Roadholder due to the rather small diameter of the axle. However, if an effective fork brace was fitted, this would give more support to the inner tubes in bending, effectivly reducing the unsupported length. This effect would of course be reduced by the clearance between the inner tube and the bushes in the outer tube, so again, probably not a lot of cop here.
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The axle does not restrain bending of the inner tube appreciably, since it is clamped to the sliders which are allowed to rotate on the inner tubes. Yes, a small bending moment may be transferred when sliders start to bind ... but realistically, actions on the fork tubes should be considered independently. Essentially, the axle transfers biaxial shear force and axial load from one side to the other.

For the same reason, a fork brace of the Hyde type connecting to the sliders has limited effect. Yes, it helps sliders to move in paralell, but resist twist (flex)? Nay ....

-Knut
 
KiwiNeill said:
Pete Komarek
By twist do you mean holding the front wheel between your knees and try and turn the handlebars or is the front noticeably flexing riding along?
I have standard Mk 3 steel upper and lower clamps holding standard Roadholders with Maxton cartridge internals.
Can,t twist them at all doing the above and bike handles great at all road and (occasional) track speeds, solo or fully loaded.
Click to expand...
Hmm, odd that. I have a MkIIa, the fork is good (for a Roadholder that it..), but it's very easy to demonstrate wheel twist like this. My Ducati with 38mm forks is far more resistant, I don't think I can notice any twisting without risking serious damage to my knees.. :)

I don't experience any problems hough when riding. Perhaps next time I am at Spa, when I expect to be pushing the bike more, there I might well notice something.
 
SteveBorland and Pete Komarek
I just got home from work and did the knee twist test on both my Mk3 18" and FJ 1200 17" front wheels using tape on the mudguards as a marker.
Both are 8mm max relative to the mudguard which may add a little extra and with firm twisting in both directions. (straight edges on sliders and forks probably more accurate but this is a quick comparative check)
If you have an inch/25mm flex that sounds way too much.

The Yamaha has done 42,000mls since fitting new O.E. bushes and seals in 10/2005 and the Commando 16,000+ miles since the Maxton rebuild using their own bushes and seals in 10/2008.
Putoline full synthetic fork oils used with tapered roller steering head bearings in both bikes.

If you don,t look at the mudguard while twisting, both feel solid, but pretty impressive for the lower mileage 35mm Commando forks as the sliders are 80mm shorter, from the 17mm axle centre to seal face and has a 3.5" spoked alloy rim.
I,ve fitted a second disc assembly using a modified right side slider, so no lower clamp bolts, relying only on the axle tightness to resist flex here.
FJ has a cast 3.5" alloy wheel with substantial, clamped 41mm fork legs and lower clamp bolt for the 15mm axle.

I think it,s safe to say the Commando tapered retaining method on the top clamp is perfect and any excessive twist may be due to other factors as mentioned by other posters.
 
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It might be very easy to make a set of parallel fork yokes for a Commando that would crash you. With my Seeley which also has 27 degree rake, I use about 30mm of yoke offset. If you did that with a standard Commando with the Isolastics, it would probably mishandle and grab you by the throat. I've never had a twist problem with parallel yokes, only ever with the tapered top yoke. With a road bike, the handle bars are usually fairly long - so if you get any twist, the effect is magnified. A tank-slapper with long handlebars is much more difficult to control than with clip-ons. The reaction comes through the handlebars and with long bars the size of the movement is much greater, but the forces involved are still sufficient to launch you.
If you are making fork yokes - the first time you ride the bike, it might pay to chose a place where you can crash safely.
 
Fullauto said:
Comparing Triumphs and BMWs to a Norton and then saying that converting the forks to parallel tubes will cure a non existent problem doesn't cut it with me I'm afraid. You're barking up the wrong tree.
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Perhaps- I am assuming old designs can be improved. Wiggled the Norton front end around and it is stiffer than the Triumph. Interesting that Kenny Dreer went to sturdy full clamps.
 
KiwiNeill said:
By twist do you mean holding the front wheel between your knees and try and turn the handlebars or is the front noticeably flexing riding along?
I have standard Mk 3 steel upper and lower clamps holding standard Roadholders with Maxton cartridge internals.
Can,t twist them at all doing the above and bike handles great at all road and (occasional) track speeds, solo or fully lo
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That is what I meant-Consensus I'm hearing is Norton triple clamps work much better than other iterations.
 
Pete Komarek said:
Perhaps- I am assuming old designs can be improved. Wiggled the Norton front end around and it is stiffer than the Triumph. Interesting that Kenny Dreer went to sturdy full clamps.
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Well, at least he did when he changed to other forks, but they don't have tapered tops, so he really didn't have a choice. I don't recall him using pinch bolt top clamps on earlier bikes with Norton forks, but maybe there were some. All the Kenny Dreer bikes I've seen had non-Norton forks, and hence pinch bolt top clamps.

Ken
 
mdt-son said:
The axle does not restrain bending of the inner tube appreciably, since it is clamped to the sliders which are allowed to rotate on the inner tubes. Yes, a small bending moment may be transferred when sliders start to bind ... but realistically, actions on the fork tubes should be considered independently. Essentially, the axle transfers biaxial shear force and axial load from one side to the other.

For the same reason, a fork brace of the Hyde type connecting to the sliders has limited effect. Yes, it helps sliders to move in paralell, but resist twist (flex)? Nay ....

-Knut
Click to expand...

I think this is also a perfect explanation why it's not worth fitting such a fork brace - very limited effect and very difficult to stop it causing bindingof the forks. If one was seriously worried abouthte sliders not moving in unison, it would be better to solve this down at the axle. Unfortunately, there's not much space down there to change anything...
 
SteveBorland said:
I have a MkIIa, the fork is good (for a Roadholder that it..), but it's very easy to demonstrate wheel twist like this.
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Let's keep apples and peaches separated, shall we?

Firstly - does your front wheel twist? That is a possibility, given the odd spoke arrangement at the disc type hub, one side of spokes having nearly no prestress according to what I've read. (I don't use this wheel type myself.)

Secondly - are your sliders firmly supported at the fork tubes? If bushes are worn, no wonder you can feel a twist.

Thirdly - are your headstock bearings preloaded to the correct tension? If the stem is allowed to wiggle even the tiniest amount, the deflection down at the axle will be very noticeable.

If the front end is set up properly, the twisting you feel should be NIL, at least when h/bar is turned by a human force. :)

-Knut
 
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Nortoniggy said:
From an engineering perspective the taper fitting is superior to clamping the tubes. It's much easier to manufacture a clamp setup though.

Ian
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Can you explain why it is superior? When I look at how a taper is tightened that seems to be a large part of how well it works.
 
Pete Komarek said:
Can you explain why it is superior? When I look at how a taper is tightened that seems to be a large part of how well it works.
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Do you think clamping the primary drive sprocket to the crankshaft would be superior to the taper it fits on normally? A taper is a strong and positive way of locating two components. If the taper is accurate it doesn't need to be exceptionally tight.

Ian
 
How accurate do you think Norton made the taper on the fork tubes and in the top yoke ? Was it of critical importance amongst the myriad of other production issues ? With a parallel fit, as long as the clamp is tight, there is zero movement. With the taper, there only has to be an error of a degree to create the situation where it is tight at the top and loose at the bottom and vice versa.
 
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