Clunk goes the forks

norbsa48503 said:

LAB, I am aware that John's kits are a cartridge set up and do not reuse the stock tubes. You miss my only point. The travel with this kit is controled by limiting slider travel by using the rod, tube and cap to stop the slider from using all the travel avialible between the bushings.

So the valve controling rebound has the job of keeping this top out from clanging. Just that simple like it or not

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I fully understood what you meant. But perhaps it's not that simple-as the rebound adjustment may not have any influence on the rebound buffer stop?


John? Would you care to add anything?

norbsa48503 said:

I think that if most people just did some testing with oil in and springs out to feel what the fluid is doing for the road feel the questions would go to a higher level.

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A good tip — must try that myself!

OK so in this set up you have one set of internals controlling the rebound, it is just that one side providing the travel limit? Or, are the rod lengths controlled to a high degree of accuracy so that the rod, cap and valve combination are set as a mechanical perfect pair to limit travel? I have found many front ends with bent over 2MM dowels from hard top outs. That is one reason to drop the system of using this combo to control travel. Yes oil will dampen the blow but if you limit the travel with a valve you have a potentially very heavy weight to hang off one fork leg with a 3/8 rod put under pressure. Of course the advantage of John’s set up is the valves that only have to work to one purpose can be set and designed to that purpose with much finer control.

norbsa48503 said:

OK so in this set up you have one set of internals controlling the rebound, it is just that one side providing the travel limit? Or, are the rod lengths controlled to a high degree of accuracy so that the rod, cap and valve combination are set as a mechanical perfect pair to limit travel? I have found many front ends with bent over 2MM dowels from hard top outs.

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While the Lansdowne dampers may have a similar outward appearance to the originals, (I have never dismantled my own, as they come "Loctite sealed" and I think John recommends they should not be dismantled unnecessarily) but a photo John sent me a while ago of the prototype components, shows the Lansdowne damper internals are nothing like the originals, so there are no dowels to bend, and even if the Lansdowne dampers did top out, I doubt it would be anything more than a minor annoyance-with no damage done to any parts, and I know John has made a number of minor improvements to the damper kits since he sent me that photo, so John is the person to answer the technical details about exactly how the dampers operate-if he wishes to do so.

Well it's easy to find how they work, just leave the cap off and do a stroke check. Than put the cap back on and re-check it. If the internals are controlling the stroke than you will see it go from 6" to 4 1/2' or so depending on the setting inside. Now if in fact the internals are in control of the stroke than in the end when the front comes unloaded than the weight of the wheel, brakes, axle, and sliders come down on that single 3/8 rod, secret internals or not. I am not saying the kit is no good far from it. But a frank discussion of how it all works seems prudent so as to understand what that clunk could be doing to the guts of the front end.

norbsa48503 said:

Well it's easy to find how they work, just leave the cap off and do a stroke check.

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As I believe I said, they are semi-"sealed" units. [Edit: unless by "cap" you meant the fork top bolts and not the damper tube "caps"?]

norbsa48503 said:

If the internals are controlling the stroke than you will see it go from 6" to 4 1/2' or so depending on the setting inside.

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Yes the Lansdowne dampers control the stroke (limiting the fork movement to the standard 4 1/2") but I never said otherwise.

Had this problem on my 750 when i bought it in 78 - turned out to be lack of o rings on headlamp brackets letting them bounce up and down between the yokes. Took ages to find the source of the noise!

myjota said:

turned out to be lack of o rings on headlamp brackets letting them bounce up and down between the yokes.

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It would be hilarious if it turned out to be that after all the technical debate. :lol:

Just a thought, is the front spindle tight ?

Cash

I get confused on which kit is which at times. If no mechanical stop provided the forks should expand just over 6" before the top and bottom bushes clash BUT when forks are able to expand full 6" the factory Roadholder hydraulic soft indefinite stops can function as designed, wonderfully I've found.

Just hydraulic dampening, no matter how good or progresive will not act as a top out or bottom stop, though it may delay or prevent top out-bottom if forks not loaded or unloaded hard and long enough to over come spring and oil resistance in time to miss clank/clunk. If Landown kit still limited to 4.5" travel then its physically limiting travel by its internal part fouling, not by real protective hydraulic lock stops as Gerg's hobot spring spacer long rod kit.

I take special note of clunk-clank coming external to forks, thanks, may save me much turmoil some day.

I mention again there is no concern about weak support of forks when full extended to no bush/bush over lap as can only get that way when NO load on forks and then as soon as ANY load put back fork instantly and complinatly compress to over lap again before any significant load to deform them hits.
I've tested this in horrific impacts hitting stuff/holes in unintended shocks that almost knocked my teeth out playing Steve McQueen in pastures. No problemo to fork thank goodness.

I've figured out a way to get full 6+" extension and hydro top stop using the cartridge emulators [Race Tech type] by removing damper rod &valve, cutting damper tube down by length of cartridge and using the spring centering top button modification I think LAB showed us. Cool. Don't yet know if I'm missing out on anything by this mod but only one way to find out someday.

Simplest test to educate all of us would be put in more fluid and also up the grade some to see what effect that has. Beware fork action pumps out the air not pumps it up, so can feel fine 1/4 mile then instantly hydro lock forks which both makes them jump sideways on each little lump but also reverses the expected action of pilot input. I suspect w/o my straight steering practice and Peel's incredible stable chassis tolerance I'd of been tossed off just creeping back to shed on my driveway. Basically had to keep both feet down at 5-6 mph or became about uncontrollable yet remained silent.

Btw hobot is never capitalized as just a handle not a proper Name.

The slider bushings and the staunchion tube stops SHOULD be the mechanical stop for fork extension, NOT the damper rods.

Of course, short of that mechanical stop, the damping system SHOULD engage and provide a hydraulic soft stop before that absolute mechanical stop.

Small diameter damper rods can handle dampened tension. They should not be subjected to impact tension.

It's a good thing wheelies are not favored by those who ride these bikes.

Dampening is not the stay thing or function as hydraulic stops.

Am I incorrect to think that mere dampening strong as it may be only slows speed of travel but does not limit the length of travel?

Am I incorrect that closing off hydraulic passages will limit travel short of metal to metal by the incompressible fluid suddenly being trapped to stop further motion by translating the stop force to all surfaces exposed to the pressure?

Am I incorrect to think that strong enough dampening to slow fork action so much it dose not have time to travel 4.5" to hit metal/metal, would be too dampened to work as desired?

If dampening was non linear progressive I assume that could work w/o true hydraulic stops. Does this hi end kit have this feature?

I'm curious if I can notice removing 1/2 my progressive dampening by installing a rebound dampening cartridge in one leg. I think I like it when forks can extend fast enough to keep some tire traction crossing hollows.

LAB is correct, the Lansdowne kits have quite differant internals,
To start with the original Norton valve arrangement is replaced by a "Solid" brass piston. Which will take a hard knock without any damage 500 LBS on one side will cause no damage to the internals :!: the concept is very robust,and will last a life time..with a yearly oil change .

Damper travel is controled by the damper piston upper-most arrest and the main fork spring coil binding in the other direction,ie full compression which is approx 130mm, =4.1/2 inch's in old money.

The damper as a 15mm top out cushion which brings the uppermost travel to a "soft" stop, as John Dunn reported " Placing the bike on it's centre stand ,the original klonk as now gone"
Best Regards
John lansdowne Engineering

L.A.B. said:

norbsa48503 said:

LAB, I am aware that John's kits are a cartridge set up and do not reuse the stock tubes. You miss my only point. The travel with this kit is controled by limiting slider travel by using the rod, tube and cap to stop the slider from using all the travel avialible between the bushings.

So the valve controling rebound has the job of keeping this top out from clanging. Just that simple like it or not

Click to expand...

I fully understood what you meant. But perhaps it's not that simple-as the rebound adjustment may not have any influence on the rebound buffer stop?


John? Would you care to add anything?

Click to expand...

OK John, so you have beefed up the valve at the end of the rod and now the rebound side alone controls the fork travel? I am sure it works, what do your owners have as an option if it ever clunks? Is there a fine tune for the very last part of the stroke? Would you just change oil? Dial in more dampening?
O r are you really saying that the clunk is impossible with your kit and some oil even though you are using the rod,cap and valve to limit stroke?

L.A.B. said:

norbsa48503 said:

This is really simple stuff if you’re using the dampener valve against the dampener tube cap to stop the sliders from making their full stroke (as in the stock front end) than unless the valves are set right you’re going to get a clunk. Adjust the dampening. It’s nothing bad it just needs adjusting to my thinking.

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But these are not standard Roadholder damper tubes and rods?

As John said, if the clonk was there before the Lansdowne kit was fitted-then it isn't likely to be the Lansdowne dampers causing the clonk-especially as the Lansdowne kits now have a proper built-in rebound buffer.

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I had a clunk once when the RH fork had not pulled all the way up to the top yoke. Then one of the headlamp holders had about 5mm of movement up and down causing a pronounced clunk when hitting bumps.

Hi, The final extension is stepped down for the last 15mm, By the top guide covering the bleed holes. when set its near impossible to top out...well John Dunn [ Tec Commando adviser] could not get them to Top out..that was riding over every pot hole he could find!..read is report on this forum.

norbsa48503 said:

OK John, so you have beefed up the valve at the end of the rod and now the rebound side alone controls the fork travel? I am sure it works, what do your owners have as an option if it ever clunks? Is there a fine tune for the very last part of the stroke? Would you just change oil? Dial in more dampening?
O r are you really saying that the clunk is impossible with your kit and some oil even though you are using the rod,cap and valve to limit stroke?

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Ludwig..i love your inovation's

ludwig said:

Why not limit fork travel by installing a nylon spacer below top bush in the slider ?
I 'm not so fond of longer bushings ..
The length of the spacer will determine the desired travel .
No more cluncks .
This will also eliminatate the need to screw the damper rod in the top nut and make fork service much easier .
( I posted about this before )
prevent spacer to drop down with a lock screw here :

Cut up an old stanchion and drill trough a top nut to make a ' test tube ':

Screw in the damper of your choice ( here a LD damper ) , put it in a vise , fill with oil and pump away .
This way you can test the effect of diff. settings and oil grades without stubborn springs or sticking bushings and seals ..

John : a progressive spring can easily take 20 cm before coil bound ..

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Spot on HOB!

hobot said:

Dampening is not the stay thing or function as hydraulic stops.

Am I incorrect to think that mere dampening strong as it may be only slows speed of travel but does not limit the length of travel?

Am I incorrect that closing off hydraulic passages will limit travel short of metal to metal by the incompressible fluid suddenly being trapped to stop further motion by translating the stop force to all surfaces exposed to the pressure?

Am I incorrect to think that strong enough dampening to slow fork action so much it dose not have time to travel 4.5" to hit metal/metal, would be too dampened to work as desired?

If dampening was non linear progressive I assume that could work w/o true hydraulic stops. Does this hi end kit have this feature?

I'm curious if I can notice removing 1/2 my progressive dampening by installing a rebound dampening cartridge in one leg. I think I like it when forks can extend fast enough to keep some tire traction crossing hollows.

Click to expand...

ludwig said:

Why not limit fork travel by installing a nylon spacer below top bush in the slider ?
I 'm not so fond of longer bushings ..

Click to expand...

Ludwig, can you elaborate why not?

Gosh almost hate my own posts on this forking subject but its life and death to me.

THE Only cycle I stopped crashing on THE Gravel and actually looked forward to exploring it, both in new places but also new ways to do it in rougher and rougher conditions, was Ms Peel. Factory Cdo and SV650 both shared the complaints of clashing stops and out of cycle non-progressive damping. So fast/hard learned I'm just lucky to make it in and out on them behaving more timid than even novices start out, because I'm no Novice to THE Gravel now and know too well how little how fast they get upset.

On Peel i seek out to ride the very crests of loose uneven berms in between the ruts, as its so uncanny secure sensation with no jarring up the grips and no rebounding secondary effects from road texture or pilot inputs, or rather lack of pilot as Peel about self steers, so i only need to lightly dampen forks so they don't slap during the unloaded intervals. In a way its easier to ride the more unstable stuff because the inputs of throttle/forks/brakes can be so much less for so much more effect. But when predicable its like riding on a hard plane in a boat rather that pushing water below a plane.

Stable rough pavement is total non issue to Peel when leaned, one because of forks and two because of tri-links. As forks get better more load can be applied to chassis and as chassis improved more loads can be forces on forks. Alas in unlinked iso's the effects of one end show up at the other to splash and confuse on what's what. Can not really tell what one end's improvement is really worth if some other weakness is limiting improvement to do its thing.

Any mechanical stops on hard un-deforming- non-elastic components will create some shock back to pilot and spike loads on inner components. No more of that on Peel thank you. Peel got to point only two things to pay attention too, throttle steering and rear patch grip. Factory Cdos skip side to side to wobble forks into clanking spring tuning forks just going straight, or gets into silly hinge oscillation, slapping forks just as they are trying to follow the road travel.
I have had all the complaints mentioned by racers on old and newest forks, so far as I can tell Greg's kit has removed forks form my handling limits and attention no matter what I've tried to reveal trouble as prior.

Deep down I now wonder if our fork solution will turn out like crank bearings, once thought ball and roller were the best way, now known plain jane bushes give both higher loads and higher rpm tolerance.

As this Landsdown kit still has a damper rod, maybe that could vary in dia to get some progressive function with the adjustable base line settings. I might pee in pants and toes curl to feel how good that is. Peel is my mistress I want to try everything on, at least once. I lust at the quality and engineering too so with a bit of re-thinking tinkering may be best forks ever conceived. i"m not very impressed with elite moderns, road to MX, so I'm not teasing about Landsdowns potential in RoadHolders.

BTW a fork brace must be installed to get the most out of good fork action.