850 yoke offset… why…?

Does slower steering mean more force required at the handlebars to change course?
 
Onder said:
Does slower steering mean more force required at the handlebars to change course?
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In short, yes.

But in my tests at least, the offset yokes did NOT result in either. The steering is at least as light as it was before.

My guess is that’s why they went with offset yokes. I think that if they had raked the headstock enough to achieve the trail they desired, the steering would have been too slow, too heavy. Although offset yokes also effect trail, my thinking is that the reduced fork rake angle counteracts the negative effects to a degree.

But, for the record, that is all 100% uneducated guesswork !
 
If you ride bicycles (think road bicycle here) the difference in trail is apparent, particularly if you like to ride without hands. A racing bike will have very little trail because it is designed for rapid lane changes in the length of the bike, but nearly impossible to ride without hands on the handlebars. A bike that is stable enough to pedal with no hands on the bars will not allow a rider change lanes like that. It isn't that it is a noticeable difference in the power it takes to steer the bike, it just simply won't be able to do it because the lean angle required to move over that fast would be so exaggerated that it would be difficult to recover. However at high speeds it does take considerable more energy and focus from the rider to hold the racing bicycle in a straight line.

And I believe that raking the forks back compared to the angle of the headstock moves the contact patch aft, which increases the trail, not diminishing it.
 
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rvich said:
And I believe that raking the forks back compared to the angle of the headstock moves the contact patch aft, which increases the trail, not diminishing it.
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Indeed, as already stated, vs the parallel yokes, the 1.5 degree offset yokes moved the wheel spindle centre line backwards 18mm, thus increasing the trail.

What I don’t know is, whats the difference in feel between changing the trail this way, and changing the trail by the same amount by raking the headstock?

I now assume there is a difference.
 
Nigel,

I believe the difference is with straight yokes the center line of the headstock is parallel to the fork tubes. When the yoke angle changes the two center lines are not parallel any longer. I compare it to the caster angle of a cars front end. I don’t think the 18 mm you mentioned is enough to put it back past the CL of the headstock like I originally stated but from my understanding just moving back (to a point) adds to straight line stability.
Pete
 
Deets55 said:
Nigel,

I believe the difference is with straight yokes the center line of the headstock is parallel to the fork tubes. When the yoke angle changes the two center lines are not parallel any longer. I compare it to the caster angle of a cars front end. I don’t think the 18 mm you mentioned is enough to put it back past the CL of the headstock like I originally stated but from my understanding just moving back (to a point) adds to straight line stability.
Pete
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Strange 47 posts about offset, rake & trail yet not a single one from Acotrel. I hope you are OK Acotrel.
 
holtcorseaux said:
Strange 47 posts about offset, rake & trail yet not a single one from Acotrel. I hope you are OK Acotrel.
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acotrel is no longer a member of this forum.
Edit: acotrel has since been allowed to return to the forum but is on another (temporary) ban due to his habit of going off-topic!
 
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i have to say i feel the steering on the 750 "skittish" at times and riding with one hand ...interesting & to be honest I'm not even sure on the heritage of the yokes that were in the box of bits
So changing up to 850 yokes has been on my To do List for a while
Question. What exactly in ANG type?
Looking on AN there are early and later 850 yokes, what is the difference...??
 
olympus said:
so what is ANG?
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Plenty of info on that subject already on the forum and in this thread so you could search ANG yokes.

Basically, the 850 ANG yokes angle the forks so the spindle/axle is set back from where it would otherwise be if the forks were parallel to the steering axis.
850 yoke offset… why…?


olympus said:
What are the differences (physically) between pre Mk3 & Mk3
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I believe they are the same offset. The actual differences are due to the extra hole in the Mk3 lower yoke for the brake line fitting (as the disc is on the LH side) and the addition of the threaded lugs on the upper yoke for the Mk3 console and the change to the steering lock hole for the Neiman lock.

Note that the pre-Mk3 upper yoke AN sells (although currently "out of stock") as "06.4080" is the pre-Mk3 (Mk2/2A) 06.5538 yoke for the Neiman steering lock!
andover-norton.co.uk

Andover Norton - UPPER YOKE C/W STEM 850 (

UPPER YOKE C/W STEM 850 (
andover-norton.co.uk
 
Fast Eddie said:
Perhaps we need to be clear when we talk offset. There is the ’fork offset‘ ie the measurement between the steering stem and the fork stanchions. Then there are ‘offset yokes’ ie yokes that do not hold the forks parallel to the steering stem / headstock.

I can’t recall the exact fork offset but IIRC the offset of the top yoke is the same in 750 and 850 yokes, it’s only the bottom at differed on the 850s ‘offset yokes’ as it kicks the fork angle back in.

Earlier posts state the 850 kicked out the rake by one degree, and the yoke offset kicked the fork angle back by one degree (edit: corrected by Ludwig as 1.5 degrees).

Theres lots written about rake and trail, but not a lot about changes to fork angle via offset yokes. But fork angle dictated by yokes clearly makes a big difference (in my tests at least).
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Hi all,

I did some careful measurements. My findings and math modelling suggests the following:

Trail ( with std 19" wheels, rolling diameter 647 mm)

750 '71 -'73 : 84.7 mm
850 : 103.2 mm

The difference in trail based on the above is 18.6 mm which is about the same figure FE quoted in posting #1.

The angle in the lower and upper yoke is taken to be 1.0° (I measured 1.04 degrees; NV would have chosen a multiple of 0.5 degrees for manufacturing)

Reference offset at the lower surface of the upper yoke appears to be identical to the 750 yokes (71.4 mm or 2-13/16"), so this is taken to be the datum plane.


Similar to Ludwig, I have opted for a 18" front wheel, which reduces trail a little.

Computed trail for an 850 frame / 850 yokes / 18" tyre is 101.3mm

while computed trail for an 850 frame / 750 paralell yokes / 18" tyre is 89.2mm.

The latter would be the configuration offered by CnW, among others. Contrary to advertising, high-speed stability is reduced vs. the stock configuration, but steering will be quicker.


Playing with the numbers and responding to a question raised earlier in this thread, a frame rake of 30 degrees would have been necessary when using paralell (750 style) yokes in order to achieve
approximately the same trail as for the 850 frame/850 yokes combination.

A MathCad calculation sheet will be shown shortly.

- Knut
 
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