H: Hubs, Wheels and Tyres Hydraulic Steering Damper

timetraveller

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No Vic, it is the other way round. You are correct that 40 degrees is when the forks are about fully ahead but if you look at the graph again you will see that there is about 13 mm of movement of the damper rod for each 5+ degrees each side of that. That value of 13 reduces to about 9 or 10 at each end of the stroke, i.e. at full lock either way. That means that the system is most effective straight ahead, just like your system.

Please note that I designed this system specifically to work with the new John Emmanuel type steering heads. With this design the base of the steering head is about 25 mm lower that with the standard set up and is not specifically designed to work with the original friction damper. An original type damper can be used but it requires some ingenuity. So far as I know only two people have used the original type of damper with the new steering heads. One was a bike that Greg converted for one of his customers but which was later converted to a hydraulic damper. The other is Mike Hawthorn who races (very successfully) in a class where hydraulic steering dampers are not allowed. The base of the new steering heads is supplied with three M6 holes drilled and tapped into it and my design was intended to use those holes.

Your design is very ingenious but at first glance it just looks wrong to be moving the damper body rather than the damper rod. However, I really cannot see why there should be any problem with it. It is just like Macvette wrote, every other bike which I/we have seen moves the rod rather than the body of the damper and there might be a reason for that .
 

greg brillus

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So Gregg, do you feel that hydraulic steering dampers are an unnecessary complication when fitted to Girdraulic forks?
No Peter, on the Brampton's, it seems a little over the top, given that the stock friction damper works ok provided the assembly isn't covered in grease/oil. If a bike with Brampton forks is lifted at the front the links will point down at the nose, this is similar to stock Girdraulics, that was my comparison.
 

oexing

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Greg, all the Bramptons had friction dampers from day one anyway as a safety feature, hydraulics still to be develloped then. And my setup is just a few hours of easy fabrication I did at one night recently , worked at first try. But I did a second alu lever , 4mm corrected, in a whiff after seeing some more stroke possible plus a better position more parallel for the cylinder. I am used to hydraulic dampers since 1972 on the Earles fork R 69 S , essential there as the earles fork is very heavy and prone to flutter. The friction dampers are not so comfortable for their stiction when nipped up too much so hydraulics are a real bonus and at € 30.- from China no question.
Norman, sorry I misinterpreted the diagram, so the design is allright. Anyway, maybe you´d like to hold that China damper to the new style steering head , could possibly make life easier as there could be more space to fit all components - I cannot tell. Still I can´t see any snag with moving the cylinder in place of the rod, the cylinder has no eyes to protest. Sometimes it pays to be openminded and think out of the box.

Vic
 
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Oldhaven

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I vaguely remember reading somewhere, maybe MPH, that the original friction damper requires some play between the pin in the fixed plate and the hole in the boss on the UFM. Someone noticed this and made a close fitting pin and was rewarded with a disconcerting slow weave while underway. Does using a hydraulic damper anchored in that boss make this unimportant?
Also, I am sure it is noted in the instructions for fitting a damper supplied with the JE steering kit, but how is the damper bracket fixed to that boss? Is it tapped?
 

timetraveller

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The damper bracket is supported by a specially made stainless steel bolt which has a 3/8 BSF thread on its upper part. This bolt has three different diameters as well as the hexagon to fit a BSF nut (i.e. you can use your existing spanners). This screws into the hole originally intended to take the anchor pin of the friction damper. The internal diameter of this is 5/16" which coincidentally is the right size for tapping out to 3/3 BSF. On my own bike, the ex-Cecil Mills road racer, this hole was already tapped 3/8 BSF but who did that, when or why I have no idea. All the others I have looked at are plain holes. I was aware of the need for some slop to prevent weaving, as described by Oldhaven, but this does not seem to be a problem. My guess is that the damper is meant to prevent rapid movements and as such is actually better than the original friction damper. Most people will be aware of 'sticktion' whereby a friction damper takes more force to start it moving than it exerts once it is moving. The hydraulic dampers move very easily at slow speeds and do not suffer from this problem.
 

vibrac

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When I drag the comet off the naughty step this winter (other tasks permitting) putting some small slop in the damper is one of the things I shall try. I certainly had some slight almost imperceptible weave in the few tests I ran with the new head and damper
 

oexing

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So I found a few pictures of steering dampers to ease some minds when looking at my version of pushing the cylinder instead of the rod. There are numerous kits for bikes that show a bracket fixed by two bolts that hold the tank on top of the frame. This bracket is the anchor for the "static" rod, the cylinder is bolted onto an extension of the top yoke - so that is same idea like mine which I placed below the yokes, same characteristics of motion. When this is allright for fast Ducatis, so that does it for me. I have added some youtube clips about these versions on modern bikes for comparisons. What I do like is the minimal rotation of the cylinder from lock to lock, very useful when there is not a lot of space for swivelling components with the more common layout. The alu lever in my version can have 57 mm between centres to use all reasonable stroke plus safety . BUT the off-centre bracket in the China set places the whole affair another precious bit to the rear of the fork to give extra space when required but still keeping the same stroke. There are more brackets available from other manufacturers for extra offset if necessary - or DIY.
I have made some more photos of the Brampton test set to better show clearances from other perspectives, no troubles to be expected, as all the rest of the girder components only go to the front from here.
When comparing versions I think my proposal is easier to copy as the motion is quite clear to overview, no critically dimensioned long lever to machine (I can imagine all that headscratching to work out this set) and no surprise clashes with rest of bike to expect as the set keeps its alignment quite nicely, no rotating actions in unsuspected places. In case of a mounted crash bar a bracket clamped onto that seems logic as it is close to the anchor bolt for the rod and no big thing to work out : When having the rod pointing to the left side, set the fork to right lock, the rod to full compression minus safety gap, the damper cylinder about right angle to bike centre axis. Now you get the position of the bolt hole on the bracket that I fixed in the sidecar lug - or on the bracket clamped to the crash bar.

Vic
Youtube links :
Hyperpro damper Honda
Ohlins damper Kawasaki
Matris damper Triumph
Ohlins Ducati 1198

Ducati 11.jpg


Ducati 12.jpg


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P1060220.JPG


P1060222.JPG


P1060204.JPG
 

Bill Thomas

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When I drag the comet off the naughty step this winter (other tasks permitting) putting some small slop in the damper is one of the things I shall try. I certainly had some slight almost imperceptible weave in the few tests I ran with the new head and damper
A few of us have found the felt washer on the lower stem is a bit too thick, When new, On a standard set up !,
Not sure if you use them on the New set up, It makes the steering too stiff ?, I would make it thinner.
Cheers Bill.
 

vibrac

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No felt washer at the moment the wandering at say 25 mph was at the mild end perhaps like a slightly under inflated tyre hydraulic damper at lowest setting
Anyway sometime this winter a complete strip and rebuild of forks is on the cards with a variety of suspension dampers
But twin engine mods come first that bikes steering is top draw Brampton with coil over and manual std damper
 
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