H: Hubs, Wheels and Tyres Hydraulic Steering Damper
- Thread starter greg brillus
- Start date
I did have a "D" style friction damper on my girdraulic equipped Comet and it was both oil free and done up tight when I had the slapper that shattered my right wrist. Wrist recovered ,all be it with a permanent kink, I now have a hydraulic damper set on almost its stiffest setting. I have had subsequent head shimmy on poor roads but no slappers - the damper did/does its job!
Martyn
OK Chaps, a few weeks ago I said that I would have a go at designing a hydraulic steering damper for the standard girdraulic steering head. Orders continue to come in for the item designed to go with the JE modification and as I am waiting for some parts to be machined for some alternator kits I decided now was the time.
Let us go back a bit and look at Vic's design, #29 above. I thought this was ingenious and it certainly stops some of the rotation of the damper body but I felt that it should be possible to do better than rely on the friction damper to resist the rotation of the new damper plate. If you look at the base of a standard steering head you will see that there is a short tube projecting downwards which locates the centre of the normal friction damper. It seemed to me that one should be able to use that, and the two holes at the front of the casting to make
a more secure location. I therefore made up a model of what I thought might work from some 3.5 mm thick ally plate and it looks like this.
Please note that this is all made by hand and uses in stock screws etc so please excuse the packers etc. My intention is that this plate would be located by the two screws/bolts at the front and some of the plates of the original friction damper holding the new plate securely over the raised tube.
When installed on a 'D' steering head it looks like this.
You can see that it clears all parts of the engine and a crash bar with ease but there is a problem. Vic had cleverly made and anchor for the end of the hydraulic arm that fitted into the sidecar fitting. If one has a crash bar (or sidecar) fitted then one has to use some other way. In the photograph the 'anchor' is just a couple of bits of wood but it allows me to work out the approximate distance from the crash bar, both fore and aft and up and down that the anchor point needs to be. Very roughly it is one inch in front of the front face of the crash bar and level with its base. Now it would be possible to design something to clamp around the crash bar but that raises another problem. The diameter of the round part of this crash bar (one of the good quality ones from either Maughan's or the Spares Co, machined from solid is 24.21 mm or 0.953". It is not clear that there is a standard diameter for crash bars. So it needs some input to decide whether one can come up with an anchor design to fit to a crash bar, even the enclosed 'D' crash bars, or whether it is gong to have to be some very clever clamping device that will fit a variety of diameters and be strong enough to withstand the force that might be imparted if a speed wobble did try to develop.
Having gone through the exercise with Vic's design I decided to go back to making a combination of my design for the JE steering head and the above. A new ally plate was made that has the lever arm like my earlier design for the JE system but is located like the above design.
Above is a picture of this alternative design on one lock and another picture of it on the other lock
. It suffers from the same problem at the system for the JE steering head in that there is more rotation of the damper body but it uses the same feature of mounting the damper body on a special bolt to fit into the original friction damper anchor pin. This means that it can use some of the same parts and thus keep the cost down. Mounted on a bike it looks like this
and clears all parts of the engine and the crash bar.
Both these designs allow most parts of the standard friction damper to be used to locate the new plate although the friction damper itself will be inoperative. I would make the plates from 4 mm thick stainless steel plate and get them CNC cut to ensure smooth curves and a nice polished edge.
Is there anyone out there who wants to stick with the standard steering head but who would like to have a low visibility hydraulic damper?
Let us go back a bit and look at Vic's design, #29 above. I thought this was ingenious and it certainly stops some of the rotation of the damper body but I felt that it should be possible to do better than rely on the friction damper to resist the rotation of the new damper plate. If you look at the base of a standard steering head you will see that there is a short tube projecting downwards which locates the centre of the normal friction damper. It seemed to me that one should be able to use that, and the two holes at the front of the casting to make
When installed on a 'D' steering head it looks like this.
Having gone through the exercise with Vic's design I decided to go back to making a combination of my design for the JE steering head and the above. A new ally plate was made that has the lever arm like my earlier design for the JE system but is located like the above design.
Both these designs allow most parts of the standard friction damper to be used to locate the new plate although the friction damper itself will be inoperative. I would make the plates from 4 mm thick stainless steel plate and get them CNC cut to ensure smooth curves and a nice polished edge.
Is there anyone out there who wants to stick with the standard steering head but who would like to have a low visibility hydraulic damper?
So, now I can provide some numbers of my last setup for the Brampton fork: I added a rotary encoder from the shelf, funny 0.09 degrees resolution on the small black box in the photo, plus a tiny linear encoder, max stroke 11mm and read 66 degrees from lock to lock, 33 degrees one side. At straight ahead steering one degree rotation of steering produces 1.05mm stroke on the damper rod and close to the locks that reduces to 0.80mm due to lever effects, shown on the DRO.
I did another alu lever 3.0 in a lazy hour with 60 mm between centres because I could see a bit more stroke available , 64 from a total of 70mm in the China kit, plus a little more space by setting the cylinder with its offset bracket another few mm back towards the engine and is now fairly close to the sidecar lug. The old friction set had its anchor pin at 53mm , our starting size alu lever 1.0 . When turning the Bramptons to their locks you get about 7 mm clearance at the flanges that mate with the friction discs, and the rod, good enough for me. No need for extra safety clearances as the fork stops are very solid cast steel items - and even a damaged damper replaced at € 30.- from China is just peanuts - in the Vincent world today.
In most cases I do not see the need for extra bolts to fix the alu lever to the Brampton but one can add them certainly so as not to rely only on the friction discs. There are no existing bolt holes on that fork that could be used for the lever. The opinion seems to be that hydraulics are no real necessity on Bramptons and most drivers are comfortable with only light friction settings and that is why I just guess nipping up the standard friction plates via knob will lock the alu lever hard enough to do its job. But a countersunk screw there will ease your mind and when added you do not have to think of resetting ever later.
When going for my setup and a crash bar is fitted you will fabricate a bracket that is clamped on the bar. For a batch of sets one could provide a bracket with a clamping diameter large enough for biggest bars in use and supply split adapter bushes like with tele clip-ons or have the owner do his own split bushes, easy enough to do.
As to tank slappers, I looked into some web pages dealing with those. It seems you can expect them to hit you by pulling off high speed wheelies and when the front rubber touches down in minimal deflection to the basic direction you will be challenged even on modern super bikes. So I´d think you can have that on any bike, Bramptons, Girdraulics, high tech teles, provided you are going fast enough and the front wheel gets airborne in a second, by wheelie or jumps on bad roads. Maybe you could try endless mods to the geometry of the steering but still unable to exclude the risk for 100 percent as confirmed by modern super bikes. I would not declare to be safe with a Brampton , just that people seem to be a bit sweeter on bikes with Bramptons - no ?
Mac, your design is set a lot lower with packing pieces. What is the idea, any places on the bike that may clash with fork components - or just the hexagon bar length that holds the cylinder ? Very high packings just do not look right to me, extra bending load on levers - also found on kits sold for modern bikes - poor design I think.
Just came to the conclusion you cannot adapt the 60 mm type lever on the Girdraulics as these have more lock to lock angle of ca. 40 degrees per side ?? On the Bramptons the 60mm lever is perfect with 64mm stroke on 70mm damper, the Brampton does just 33 degrees, 66 degrees total.
Vic
I did another alu lever 3.0 in a lazy hour with 60 mm between centres because I could see a bit more stroke available , 64 from a total of 70mm in the China kit, plus a little more space by setting the cylinder with its offset bracket another few mm back towards the engine and is now fairly close to the sidecar lug. The old friction set had its anchor pin at 53mm , our starting size alu lever 1.0 . When turning the Bramptons to their locks you get about 7 mm clearance at the flanges that mate with the friction discs, and the rod, good enough for me. No need for extra safety clearances as the fork stops are very solid cast steel items - and even a damaged damper replaced at € 30.- from China is just peanuts - in the Vincent world today.
In most cases I do not see the need for extra bolts to fix the alu lever to the Brampton but one can add them certainly so as not to rely only on the friction discs. There are no existing bolt holes on that fork that could be used for the lever. The opinion seems to be that hydraulics are no real necessity on Bramptons and most drivers are comfortable with only light friction settings and that is why I just guess nipping up the standard friction plates via knob will lock the alu lever hard enough to do its job. But a countersunk screw there will ease your mind and when added you do not have to think of resetting ever later.
When going for my setup and a crash bar is fitted you will fabricate a bracket that is clamped on the bar. For a batch of sets one could provide a bracket with a clamping diameter large enough for biggest bars in use and supply split adapter bushes like with tele clip-ons or have the owner do his own split bushes, easy enough to do.
As to tank slappers, I looked into some web pages dealing with those. It seems you can expect them to hit you by pulling off high speed wheelies and when the front rubber touches down in minimal deflection to the basic direction you will be challenged even on modern super bikes. So I´d think you can have that on any bike, Bramptons, Girdraulics, high tech teles, provided you are going fast enough and the front wheel gets airborne in a second, by wheelie or jumps on bad roads. Maybe you could try endless mods to the geometry of the steering but still unable to exclude the risk for 100 percent as confirmed by modern super bikes. I would not declare to be safe with a Brampton , just that people seem to be a bit sweeter on bikes with Bramptons - no ?
Mac, your design is set a lot lower with packing pieces. What is the idea, any places on the bike that may clash with fork components - or just the hexagon bar length that holds the cylinder ? Very high packings just do not look right to me, extra bending load on levers - also found on kits sold for modern bikes - poor design I think.
Just came to the conclusion you cannot adapt the 60 mm type lever on the Girdraulics as these have more lock to lock angle of ca. 40 degrees per side ?? On the Bramptons the 60mm lever is perfect with 64mm stroke on 70mm damper, the Brampton does just 33 degrees, 66 degrees total.
Vic
Very nicely done Vic. I have gone back and calculated the movement per degree from my measurements with my original JE steering head lever arm damper. I get 1.08 mm per degree in the centre, you get 1.05, and I get 0.83 mm near the ends of the movement and you get 0.80. I would trust your figures more than mine as you have better measuring equipment but the numbers are essentially the same. It seems that those figures will be about the same whatever linkage, or lack of it, one uses.
Norman, I was a bit puzzled why you did not run into problems with your findings about available stroke and characteristics at mid-position and near steering locks practically identic to mine. Indeed I measured 1.07 mm at neutral steering as seen in the photo and rounded up a bit but it does not really matter with both setups. My lever 3.0 is the 60mm size between centres so this shows said readings like your version, but then your cylinder is mounted at the 53 mm friction pin lug so again I am puzzled why that can be ? Sure, your damper does 75mm , right, my type only 70 mm . You noted about 40 degrees per side with Girdraulics, I got 33 with Bramptons, so we should be very clear to show up limits with various components built into different forks. A sketch with sizes of levers and total damper ranges will help drivers to know what works for whom. I do not know much about Girdraulics and important sizes around these so can only confirm, that the 60 mm lever works perfectly on Bramptons with a 70 mm damper and 64mm active stroke. Anway, at least thankfully there is more than one single proposition for improving both fork types and owners can choose what suits them best for their particular bike.
What I can draw out of this discussion is that I will most likely put one of these dampers onto other bikes in my shed as well. The friction types are frankly only a very poor solution and hydraulics can be added today without spoiling the looks of a classic a lot. The big plus is a much smoother and safer ride when roads are a bit challenging - and I really love good old winding roads , a bit rough is very OK for me.
Vic
What I can draw out of this discussion is that I will most likely put one of these dampers onto other bikes in my shed as well. The friction types are frankly only a very poor solution and hydraulics can be added today without spoiling the looks of a classic a lot. The big plus is a much smoother and safer ride when roads are a bit challenging - and I really love good old winding roads , a bit rough is very OK for me.
Vic
The hex bar which mounts the pivot is that length for two reasons. First the operating arm needs to clear the concentrics on the girdraulics which are lower on the new steering stem than on the original and at full left lock, the damper body.Secondly it is drilled and tapped to take the button head bolt on which the damper is pivoted. I could shorten it by about 5mm but this would leave less material between the end of the internal thread and the transition to the male thread which screws into the UFM.
On the girdraulics, I found that either the damper eye on full right lock or the damper rod on left lock were dangerously close to the spring boxes if the damper was allowed to rotate too much wrt to the steering. Also the is a potential clash with the front exhaust valve cap when this happens. Thats why I went to a centre pivot on the damper body. I suspect that your set up will have issues with girdraulics both with the spring boxes and the valve cap.
I'm not concerned with bending stresses because this is a pin jointed mechanism so with the exception of the frame anchor, these are negligible and your set up uses the same anchor point.
Regards Mac
On the girdraulics, I found that either the damper eye on full right lock or the damper rod on left lock were dangerously close to the spring boxes if the damper was allowed to rotate too much wrt to the steering. Also the is a potential clash with the front exhaust valve cap when this happens. Thats why I went to a centre pivot on the damper body. I suspect that your set up will have issues with girdraulics both with the spring boxes and the valve cap.
I'm not concerned with bending stresses because this is a pin jointed mechanism so with the exception of the frame anchor, these are negligible and your set up uses the same anchor point.
Regards Mac
Last edited:
Hi Mac, If you look at the photograph I put on #14 of my bike on full right lock you will see that the damper parts are not near the concentric where the top of the spring box would be. There is also no problem on the other lock. The only problem I found was that the end of the lever arm was hitting the side of the front exhaust valve spring cover but only slightly. I removed about 1 - 1.5 mm from that arm and there is now plenty of clearance. I had 30 of these lever arms laser cut out of 10 mm thick ali plate and that was a mistake. When these have all gone I will get the next batch milled out to give a much better edge finish. It took seven hours on each batch of ten of the present ones to get the edges to a finish I thought was acceptable. I think that this is all very interesting and I like Vic's design. I find it interesting that so many different approaches all seem to work well enough. In the future there will be no excuse for anyone who would like to have a hydraulic steering damper. Their only problem will be deciding which design to go for.