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H: Hubs, Wheels and Tyres Hydraulic Steering Damper

oexing

Well Known and Active Website User
VOC Member
#21
At that price customs are not interested, at least not in my country. You´d pay VAT if ever at all.
I am a bit astonished that you get that quoted stroke with your set up but then I only judge from the pictures and was wrong obviously. I´d have to see it in real life. Still I think the damper should be set more towards the crash bar for better kinematics and the alu lever modified accordingly. But still only my thinking, not knowing . . . .

Vic
 

timetraveller

Well Known and Active Website User
VOC Member
#22
I think that you might find it harder than you think Vic. I made five plastic or wooden prototypes before I got it as I wanted it and I had the advantage of having a UFM off the bike and on a work stand so that I could play with the parts and have a good view of what was going to hit what. I still got it wrong because as soon as I mounted the UFM plus damper on to an engine I found that the long ally arm was hitting the front exhaust valve spring cap. Fortunately only by about one millimetre so that I could relieve the ally arm by that amount. The next batch of arms, which will be milled out rather than laser cut out, will have that mod incorporated. If you can produce a better design then you would be doing us all a favour. If you want to use the same damper then you are limited to that 75 mm total travel and in reality one cannot use all of that. I settled for about 65 mm and Vincent for about 70 mm. I know that a longer lever arm would produce more movement but both Vincent and I are using most of what is possible with these damper. I look forwards to seeing if you can produce a better design.
 

oexing

Well Known and Active Website User
VOC Member
#23
Norman,
I was thinking in getting the lever roughly 90 degrees to the damper rod - like for brake arms to Bowden cables. I see the levers in the pictures almost parallel to the damper rod which seems a bit contra-productive. So I´d place the damper very close to the Sidecar lug to get some distance between it and the steering bearing. The lever would point to the rear of the bike and about 90 degrees to the damper rod. Don´t know yet if space was enough to achieve that. Anyway no extra long lever planned, but a near 90 degree action with the damper should do and not a lot of swivelling action of the damper cylinder to be expected as in your design - my guess only . . . .

Vic
 

timetraveller

Well Known and Active Website User
VOC Member
#24
Hi Vic. Let us know how it goes when you try it. I could not get a layout like that to work but I'm always happy to see someone find a solution to a problem that I could not solve.:)
 

oexing

Well Known and Active Website User
VOC Member
#25
Yes, certainly , but not this year, still busy with the engine for a while. You may be right in warning of any snags I do not see yet before trying to get this working. I am always happy to share any ideas and details I come upon when tinkering with motorbikes hoping someone finds them useful - or simply for interesting discussions that may lead to some other new ideas and inspirations.

Vic
 

macvette

Well Known and Active Website User
VOC Member
#26
Thanks a lot for the pictures, yes, that is roughly what I was thinking of. BUT, I´d place the damper a few inches more to the rear of the bike when having it across and parallel to the crash bar. Judging from the pictures I guess the dampers do only a fraction of their stroke. The rod universal joint on the alu lever should better be placed more to the back of the bike to get more motion . It is too close to the centre line of the steering bearing to be real effective. The dampers would be OK when directed to some cylinder head nuts, so a lot more of stroke is achieved.
I am not in a stage to decide yet but will no way mount that silly crash bar so I guess to go for a bracket bolted into that side car lug to place an across damper close to the lug and fabricate an alu lever much shorter and pointing about 45 - 60 degrees to the left and rear when sitting on the bike. The lever could be clamped by the old steering damper knob assy just as it does with the friction discs, maybe a locating pin added, no screws required.
When a crash bar is fitted one could fabricate a bracket clamped onto that and get the across damper positioned the critical inches further back for more stroke. The alu lever will point a bit more to the back and be shorter to more effect - I think . . .

The bracket on that damper below has a better positioned universal joint - and it is a very good price, so I got one recently , great. Link:

Steering damper

Vic
Hi Vic,
The damper here is the same as the one I used and later supplied by Norman ( Chinese damper). Vincent's damper looks dimensionally the same but is more sophisticated, acting proportionally, the Chinese one is linear. Nevertheless, their mounted geometries are identical or at least very close. The damper pivot in your link is moveable so can be move from where it is to the centre of the damper body provided that the clamp is fitted so that it doesn't interfere with the damper valve body. The stroke on these dampers is 70mm.
The fore and aft mounting position needs to be such that the steering stops limit the travel before the damper reaches its limits and that the damper stroke is equally divided each side Of the damper body. The further the damper pivot is behind the centre of the steering stem, the longer the stroke used on the damper so the stroke and damper body pivot point are what determine the fore and aft position. Conversely, mounting the damper pivot closer to the centre of the steering stem reduces the stroke on the damper but increases the damper body rotation.
I started with an NHK damper whose body mounting ( like the one in your link) is fixed at the end of the damper but gave up trying to find a way of mounting it across the axis of the bike because of various interference issues on my twin even without a crash bar.
I asked Vincent for some advice and he posted some dimensions for me in the modified steering stem thread. Having got a Chinese damper, I prototyped a few actuating arms using the damper pivot in your link and as used by Norman and the boss for the original damper on the UFM as the hydraulic damper body mounting point. On my first attempt at making a real link ( as opposed to a mock up) to the damper rod and the damper body mounted behind the supplied pivot, I was not happy with the clearance of the damper rod and spring box on full left lock or the clearance of the damper body from the from the front cylinder exhaust cap full left lock.There was clearance but I thought that if I was unlucky enough to have a proper tank slapper I would prefer more so I went with a pivot mounted on the damper body centre line using the boss for original friction damper. Norman and I had quite a bit of correspondence on these issues and I would say that using the original friction damper stop as the mounting point is the way to go with this type of damper.
Vincent and I posted info and pictures in the modified steering stem thread on this subject.
Regards Mac
Forgot to say that my version uses 60mm out of an available 70 mm of stroke 5mm each side
 

timetraveller

Well Known and Active Website User
VOC Member
#28
I recently measured the actual stroke of my damper and it is 75 mm. One could not use all of that but it gives you some idea of what you might be able to get away with concerning lever arms. I use about 65 mm of the total potential movement.. To give people some idea of prices. The dampers which I and Macvette use cost about £30. The Hyperpro, depending upon which model is used, costs about £320. One could be changed for the other if one wished and had the money.
 

oexing

Well Known and Active Website User
VOC Member
#29
Now here is my idea of damper concept - worked on the bench, temporary setup without head lug bearings in there. So don´t be too eagle eyed in the Youtube video clip that I uploaded to give an idea of the motions. I did run into space problems with my first thinkings but finally changed places with damper rod and cylinder and liked the features as shown. No big problem to have even more clearances to girder parts or head lug casting but it should do like that. I´ll do more photos in daytime later. When a crash bar is fitted that could be used to clamp a bracket to it to provide the anchor bolt for the damper rod in the same relative position like in my alu bar that is fixed in the sidecar lug.
I think this configuration should provide more stroke around the neutral fork position and that is most important I believe. Judging from your pictures with the long alu lever more or less parallel to the damper cylinder I suspect the damper does not do much around the middle position but a lot more with more deflection on the handlebar - not sooo great if my thinking is correct ??
The mounting plate for the cylinder is a 4mm alu simply clamped tightly with the original steering damper knob, even friction discs may stay there. An alu dowel could be handy for keeping the position of the alu lever fixed on the Brampton bottom disc, but having no big torque to deal with. Distance between centres on the alu lever is 57mm presently, still safety space left on the damper rod both ends. Try to get the cylinder and rod roughly parallel to the girder fork bolts when full left lock is set, so in right lock this does not change much and middle position looks allright too, not so much swivelling of damper as in known designs above.
Hope you like it and prepared for discussing this.

Vic

Youtube link:
damper concept Brampton


P1060193.JPG

P1060200.JPG

P1060202.JPG

P1060204.JPG

P1060213.JPG

P1060214.JPG
 

timetraveller

Well Known and Active Website User
VOC Member
#30
Nicely done Vic. However, are you sure that the system will clear the fork legs/tubes or whatever they are called on the Bramptons? It looks like there might be a clash. I will write later, hopefully with a diagram, why the long aluminium bracket on the other designs does not reduce damper travel like you think. Remember that we are getting about 65 mm of movement on the damper, which is all that is possible.
 

macvette

Well Known and Active Website User
VOC Member
#31
The rotation of the damper body with respect to the bike is less but what is more important is it's rotation with respect to the steering. If you compare this with Vincent's photos, you can see that the damper body remains almost parallel to the steering stem so is more efficient in translating the rotation of the steering into the linear motion required to operate the damper rod.
The length and offset of the damper actuating levers used on Vincent's, mine and Norman's version is determined by the damper stroke in order to get equal travel lock to lock and have the steering stops prevent movement before the damper stroke is used up. This is evident from the picture showing the damper stop in the side car mount where a "static"lever is applied to the damper rod.
When I decided to source a centre body pivot, I found many damper mounting kits for a wide range of modern bikes using these dampers. The mounting details vary but all had actuating levers on the damper rod with the damper body pivoted on the frame so I decided not to re invent the wheel.
I have noticed that with the damper, the steering is lighter than with the friction damper especially at low speed so I wouldn't use the original damper with the new one. I shortened the original damper rod so I could put the original back for appearance and kept all the original bits for a future owner when I join great VOC in the sky.
Mac
 

oexing

Well Known and Active Website User
VOC Member
#34
Norman,
I do not see any clash with fork components, will post more photos. If ever required you could set the lot an inch deeper but I don´t see the need. Did you click on the Youtube link ??
I have certainly kept safety gaps for the rod with fork on its stops left and right and so most of the damper stroke is used. But what is more important: In centered position you get maximal motion at the rod for best effectivity to stop wobble right at the beginning, does not help much when effective damping is only achieved with more deflection from neutral, maybe you post a youtube clip about the earlier damper setup. Mac, do you refer to my setup when describing the almost parallel damper cylinder in all positions ? This is not the case with the very long lever in the known design. I´d be especially interested in the effetive stroke around the critical neutral position with the older idea, so a video clip could clarify this . Another benefit of my idea: No drilling of fork components required, you use the old friction clamping plates and knob, all parts of old system still mounted, only a simple alu shear pin may be a good idea for assembling later without thinking, but not really essential.
I do not see any snag with exchanging places for cylinder and rod at their respective mounting places, just see my youtube link above !!

Vic

P1060204.JPG

P1060206.JPG P1060202.JPG
 

timetraveller

Well Known and Active Website User
VOC Member
#35
If this shows up there should be a graph of the linear movement of the steering damper rod versus angle of the steering head. The straight line with the blue dots is the distance of one end of the damper rod from the damper body as the steering head is rotated. The lower curved line through the brown dots is the differences along the straight line to show up any non linearity of the movement against angle. Ideally these brown dots should be in between each of the upper blue dots. The line fitted to the brown dots is a third order polynomial, but you probably don't want to know that. Look at the lower curve and you will see that there is very little departure from linearity. Actual smallest value between the measurements is 9 and the largest, in the centre of the movement is 13.
1536924907847.png
Yes Vic, I did look at your Youtube video. It was from that that I thought that some of the parts might stick out and interfere with the legs of the Bramptons but you would have to assemble it to be sure that there is no problem. I hope that you can see from the graph that although there is a difference between the ratio of angular movement to damper rod movement it works in the correct way. That is in the centre of the movement, the fourth point in the linear graph, there is most movement of the damper rod. 13 versus 9, about 40% more movement in the centre of the travel.
 

macvette

Well Known and Active Website User
VOC Member
#36
Hi Vic,
I did look at your U tube video. I have slow broadband so posting videos is a pain. Here are 3 pictures, one straight ahead, one full right lock and one full left. The damper body stays almost but not quite parallel to the axis of the Girdraulic concentrics and Vincent's on his Bramptons is similar. What determines the damper stroke is the distance the damper pivot is behind the centre of rotation of the steering. The further aft it is the more damper stroke is used. The length and offset of the actuating arm is a bit of a red herring. The length is set by where the damper is at mid stroke and this is true of your design as well as the "old" versions. The offset (on mine at least) was chosen to minimise lost motion in rotating the damper body with respect to the rotation of the steering so that the damper gives maximum resitance to the motion of the steering ie there is minimum side thrust on the damper. Its not perfect but the best I can do with a hacksaw, drill and files.
Norman has done the math so I can't add any more. Anyway, as they say, there are more opinions in the club as there were bikes made so have fun. Regards Mac
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timetraveller

Well Known and Active Website User
VOC Member
#37
Just so there is no misunderstanding; no, or very little maths was involved. All I did was measure the distance from the damper body to the holder for the rose joint on the damper rod and rotated the steering head from fully right to fully left. To get some idea of angular measure I fastened (temporarily) a dynamo drive sprocket to the top of the steering head where the damper knob normally fits. The dynamo sprocket has 28 teeth which means that there is 12.8571 degrees between each tooth. A pointer was made up to allow visual indexing of the teeth. Clearly that is not as accurate as, say, a dividing head but was good enough to find out what was happening. The straight-ish line in the graph above is just the seven measurements from lock to lock, giving a total angular movement of about 77 degrees (call it 80). By taking the difference from one point to the next one gets the amount of movement on the damper rod between equal angles over the whole range. I have enlarged the lower graph and moved the angular movement to the values they should have in between the measured points. The graph and fitted curve are shown below. The centre of the movement, dead ahead, is at about 40 on the horizontal scale. Although there is some scatter about the curve due to the crude angular measurement is should be clear that one gets about 13 mm of damper rod movement for each 12 ish degreed of steering head movement in the dead ahead position and this reduces to about 9 to 10 mm near to the limits of the movement. I cannot guarantee that either Vincent's or Macvette's will be identical as they use slightly different geometry but I guess they will be near enough the same.
1537003625986.png
 

Cyborg

Well Known and Active Website User
VOC Member
#38
Perhaps perception of "no or little math" is relative to the amount of poetry one reads?
Interesting thread. I thought I was just going to grab a damper from the dumpster and bolt it on the Comet Mongrel without any fuss. Figuring out the mounting points for the progressive rear shock absorber linkage is causing me to foam at the mouth.

This dingy photo will help illustrate the clearance between the fork girders and the damper. At first glance I thought it might be a concern, but after looking at a set, all the monkey motion takes place forward of the steering stem.
. Bramptons.jpg
 
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oexing

Well Known and Active Website User
VOC Member
#39
Norman, when looking into your last diagram, am I right in thinking that when 40 degrees is straight ahead, a deflection of 5 degrees to the left or to the right produces only very moderate stroke on the damper rod ? That was my very first impression when some pictures were posted of your setup on Girdraulics. But I must admit I could not fully figure out what all these components do or behave in real action, my main interest is definitely the range around zero degree. Any flutter or wobble HAS to be prevented right from the start at straight ahead, zero degrees. at maximum effectivity.
It is obvious from my photos that this is the case when the cylinder is mounted on my type of alu lever and the rod gets its anchor from the sidecar lug beam resp. a bracket on a crash bar. The lever is at 90 degrees to the rod at zero degrees deflection so spot on. Another plus is the bracket that comes with the Chinese set, that places the cylinder ca. 20 mm towards the engine so you gain precious space at full left or right lock. The whole affair is easy to copy , 57 mm distance between centres on the lever leaves almost 5mm safety on both steering locks.
Then no drilling of fork components is required, the lever is locked with knob , same as with friction discs - which can stay there - and no cracking of levers is to be expected as friction discs will slip. I´d say, try it, I don´t have an interest in producing sets or get patents, just hope it will be a lot easier to fabricate at home with little head scratching .
When Girdraulics are to be added with a damper, I cannot say much, maybe the eccentrics require a bit more space at full lock, but you will no doubt see for yourself when trying the cylinder on my type of alu lever. The anchor bolt for the rod could be adjusted a bit in that case I guess.

Vic
 

greg brillus

Well Known and Active Website User
VOC Member
#40
Seems like an awful lot of trouble for forks that tend to behave themselves. Brampton's only misbehave when the bike is way too heavy at the rear unloading the front wheel/forks too much...........when the Brampton tries to become like the Girdraulic.
 

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