SunSurfer
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Posts posted by SunSurfer
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JJ Anderson plate/binding setup for La Molina, March 2010.
Image has been cropped from freely available FIS La Molina photos on fis.Smugmug.com
SunSurfer
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15mm sounds very little. I'd expect that when the board is pushed through a turn, the board is bending a lot more than that. Just my opinion though.
Remember, I'm talking only about the amount of decambering between the 2 attachment points, not the amount seen along the whole running length of the board. The same spreadsheet can be used to calculate that by slotting in the running length of the board instead of just the distance between the two plate attachment points.
A board with a 160cm running length would decamber by around 8 cm if the same 4 metre radius curve was applied.
SunSurfer
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This will probably only be of interest to people with a technical interest in decoupling plate design.
At the sliding end of the plate, how much movement will occur as the snowboard reverse cambers / decambers in the deepest part of a carving turn?
The geometric answer is the length of a chord, connecting the two ends of the arc that represent the plate attachment points on the board, subtracted from the distance separating the attachment points. The sagitta is the maximum distance between chord and arc.
I was playing with my prototype decoupling plate mockup by decambering the board and was surprised to see how little slide movement appeared to be occurring. If I actually worked through the geometry rather than just making a lazy guess what would be the result.
r = radius of decamber curve
x = known arc length (attachment point distance)
c (circumference) = 2*Pi*R
a (arc angle) = x/c*360
L (chord length) = r*sine(a/2)*2
s (sagitta) = r - square root((r*r)-(L/2*L/2))
When the math is done, if the distance separating the attachments was 700mm, and the board decambered by a sagitta of approx. 15mm between those two points, the chord connecting the two attachment points arc is now approx 699mm long i.e just 1mm different! The decambered curve of the board at this point matches the edge of a circle with a 4 metre radius!
Using the same math calculation however, a separation distance of 500mm, bent to the point of approx 159mm radius, produces a circle of circumference 1000mm, an arc angle of 180 degrees, a sagitta of 159mm, and a chord length of 318mm. The values are clearly consistent, just by looking at them.
I had thought that the slide movement required would be an order of magnitude larger and had built that kind of allowance into my own plate design. This result is leading me to reconsider how I allow for the sliding movement!
I've sat down and done the math and saved it as an attached, zipped, spreadsheet for anyone who wants to check the math or plug in their own figures.
SunSurfer
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http://www.dailymotion.com/video/x43vku_old-school-certified
Something I've not seen a snowboarder do, just skiers, before I found this video.
SunSurfer
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http://www.dailymotion.com/video/xcfcg7_snowboard-bulldog_fun
Not carving, but these dogs are really into it!
SunSurfer
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Photos from the latest FIS PGS at Valmalenco reveal more details of the Apex plate design and in use.
http://fis.smugmug.com/Other/LG-SB-FIS-WC-Valmalenco/11451389_DGBGr#809160687_aPrQX-O-LB (apologies, links not working properly now. Photos are towards the end of the 2010 season FIS snowboard photos)
shows the slots at front and rear of JJ Anderson's plate with the impression of selectable positions for the rear hinge point.
http://fis.smugmug.com/Other/LG-SB-FIS-WC-Valmalenco/11451389_DGBGr#809157644_PxDFq-O-LB
This photo of Michael Lambert carving shows the Apex plate flexing, possibly to a greater degree than the snowboard itself.
Notice also the relative positions of the pivot points in relation to the binding position on JJA's board. To my eyes the front pivot is farther ahead of the binding centre than the rear pivot is behind the rear binding centre. Looks to me like a mechanism for using plate flex to additionally absorb front foot shocks from bumps/ruts etc.
Further photos from the race are at
http://fis.smugmug.com/Other/LG-SB-FIS-WC-Valmalenco/11451389_DGBGr#808435990_7pp5R
SunSurfer
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Have got the slide mechanism made to my satisfaction.
The photo has the UHMWPE centre box raised about 2mm to help show the way in which the slide works. In use the box has just a 1mm raise under it to allow the hinge unit to slide.
The other photo shows the aluminium plate that holds the centre box down, and restricts the movement of the hinge unit.
The front hinge is identical to the rear and placed identically to the rear in relation to the binding inserts on the snowboard when the board is in the unridden position. When the board is decambered the UHMWPE box moves towards the rear relative to the front hinge. The sliding surfaces are
a) underneath - UHMWPE hinge unit / snowboard deck
b) sides - UHMWPE box /UHMWPE hinge unit
c) top - 1mm thick cutting mat plastic layer under aluminium plate / UHMWPE hinge unit
To quote from Wikipedia UHMWPE "has extremely low moisture absorption, has a very low coefficient of friction, is self-lubricating, and is highly resistant to abrasion (15 times more resistant to abrasion than carbon steel). Its coefficient of friction is significantly lower than that of nylon and acetal, and is comparable to that of Teflon, but UHMWPE has better abrasion resistance than Teflon"
I haven't yet resolved the final shape of the aluminium plate that holds the centre box in place, nor have I finished shaping the excess UHMWPE from the hinge unit.
Next to build the top plate. Rigid first, then a lightly cambered flexing version.
SunSurfer
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and tomorrow morning I will anaesthetise two patients for spinal nerve decompression, with one requiring an instrumented fusion. I've been working regularly with one of the two subspecialty trained spinal-orthopaedic surgeons in this city since May 2006. In this part of the world, Australia & New Zealand, spinal surgeons are either neurosurgeons or orthopaedic surgeons first.
The surgeon I work with declines to operate on around 95% of the people referred to him with "back problems". Why? Because any spinal surgeon who has been in the game for any period of time will have patients they have made worse, not better.
He tells all his patients that surgery will not make their back pain better, but will likely improve pain and/or function in the part of their body supplied by the squeezed nerve(s). To have any chance of achieving that outcome he has to see on MRI scan a physical problem e.g. disc bulge (prolapse), narrowed spinal nerve exit hole (foramen), or some other problem that will cause nerve compression.
He will do the minimum he can to relieve that pressure, and only performs fusions on patients where the removal of bone and or tissue to relieve nerve pressure creates an unstable spine. Commonly to relieve pressure it is necessary to remove the spinous processes, the laminae that join the facets to the spinous process, and some or all of the facet joints of each vertebrae. He does not do fusions without pedicle screws, connecting rods and bone graft.
The metal ware holds the bones in place while the bone graft, over a period of 6-12 months, actually physically grows to form new bone and joins the two bones together. If the bone graft does not do this the metalware will eventually break because of the stresses placed upon it.
Smokers do not form new bone as well as non-smokers and so have a much higher failure rate. In smokers he will sometimes additionally remove all the remaining disc material between the two adjacent bones and insert a spacer (fusion cage) + bone graft between the bodies of the two adjacent spine bones (vertebrae). This makes for a circumferential fusion, fusing both the back & front of the spine bones. He also perfoms this operation where it is otherwise necessary to remove all the disc material.
A healthy lumbar spine moves at all levels. Fusing one level means, even once the patient has made a full recovery & has a solid fusion, that to achieve the same degree of overall movement, more movement needs to occur at each of the remaining levels.
Even if you undergo fusion surgery for the right reasons it will not make your back "normal" or even reliably reduce back pain. It will probably make leg symptoms better, but even then nerves are fragile things and may not recover, and may also be damaged accidentally during surgery.
There are significant risks associated with this level of surgery.
Overall risk of death for spinal surgery is around 1:1000, deaths due to bleeding, deep venous thrombosis and pulmonary embolism, as well as underlying conditions the patient has.
Risk of post operative visual loss (potentially blindness) is around 1:10,000.
Around 3 patients in every 100 will have an accidental tear of the membrane surrounding the spinal cord during the surgery, this rate being higher in repeat surgery. These tears can usually be successfully repaired but will prolong your hospital stay, and can give you an absolutely wicked headache until they form a waterproof repair to prevent the loss of fluid from around the brain and spinnal cord.
You also need to ask about your surgeon's and institution's wound infection rate. If your metal ware gets infected it may well have to be removed, substantially reducing the chances of a successful fusion.
Overall, fusion surgery is not to be taken lightly. Many surgeons I work with have an over optimistic opinion of their results, and in particular the risks associated with achieving those benefits.
SunSurfer
Disclaimer: These comments reflect medical practice in New Zealand, not in the USA. They are provided to help you to ask informative questions of your own surgeon and help you to make an informed decision about any surgery offered.
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Softbooters don't have to have duck feet!
You might enjoy Salomeya's other vid as well.
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It pretty much looks the same as the video you can see here
Many of us have seen the video, and I've pored over screenshots from it to try to work out a number of things. Are you able to answer any of these questions?
1/ Is the carbon fibre plate essentially hinged to the snowboard at both attachment points and the hinge point able to slide at one end, or, is it something different?
2/ If Q1 = Yes, is the slide at the front?
3/ Can you describe the mechanism at the two attachment points in more detail?
SunSurfer
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Back in 1902 in USA there was a race to develop heavier than air flight. Samuel Langley was a world renowned scientist, inventor and engineer. He had at his disposal the best talent in the US for machinists, craftsman, researchers, etc that big money could buy. He and his large team repeatedly failed to create a working aircraft. At the same time a couple of poor uneducated bicycle mechanics who knew almost nothing of 'traditional science' just did things their own way. Wilber and Orville Wright and succeeded where the best experts did not.
http://en.wikipedia.org/wiki/Richard_Pearse
I couldn't let this one go by! New Zealanders have been mucking around in their sheds for a long time! New Zealander Richard Pearse is thought to have successfully flown and landed a powered, heavier than air machine 9 months before the Wrights flew at Kitty Hawk.
SunSurfer
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......Consider moving the hinge axis forward, as close to the 4x4 screws as possible. That should put less stress on the plastic in between them, and it would put a smaller footprint on the board, for less disruption of the board's flex.
The board (Riot Supercarve 180cm) I'm prototyping this for has a max distance of 50cm between it's outermost binding inserts. With my preferred stance width of 50cm, the plate needs to be substantially longer, and to support the plate, and prevent plate overhang and board flex leading to plate tip hitting the board I've had to move the hinge away from the binding inserts in the board.
I would prefer to have them as close as possible as NateW suggests, ideally the hinge attachment screws would go directly into inserts in the board, but that would mean modifying the board, something I'm trying to avoid.
Different boards have different insert distances, so a versatile system would have some ability to cope with those differences while still using the standard inserts.
The board setup is forcing some compromises, but at the same time the difficulties it throws up are making me think very hard about ways around them.
SunSurfer
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1/ This is the rear hinge unit.
2/ The screws attaching the hinge to the UHMWPE go into a barrel nut that has a smooth 9mm outer diam shaft, and a 2mm deep x 14mm diam cap. The nuts are inset into the base of the plastic and only the smooth shaft of the nut is in contact with the plastic to avoid the thread of the screw wearing away the plastic under loads.
3/ bjvircks post 18 has the guts of the design correct apart from the lack of barrel nuts through the plastic. (not shown in the original photos) and similarly T-nuts will be used in the attachment points for the bindings / toe & heel units on the plate.
4/ So far all the plates I've seen seem to be rigid.
I have a cambered flexible slalom skateboard I built 20 odd years ago, the camber helping to soak up vibration and momentary losses of traction in tight turns. I haven't seen a flexible plate yet but thought that the flex might add yet another vertical shock absorbing capability into the system, a bit like Fin was trying to build into his HFP.
Half the fun of all this will be experimenting and seeing what the result is, comparing to a rigid plate. The flex will add to the amount of slide motion that needs to be accommodated.
5/ The strength of the 3mm plate in the hinge is a concern. I looked far and wide for various hinge options including marine stainless steel hinges (too heavy). This was the only extrusion I could find that was anywhere near suitable and had a hinge pin of the kind of diameter I would even begin to entertain using. Very few hinges are available locally that are wider than about 100mm.
However, the hinge is also directly abutting both the top and rear/front of the plastic plate and so supported by it. The plate will also abutt the hinge along the hinge's length so that the forces the rider applies will be also transmitted along the whole length of the hinge. All the attachment screws for the hinge have been placed reasonably close to the hinge axis to minimise the leverage forces on the 3mm aluminium. If it's strong enough when set up this way then it allows me to custom make hinges that are suitable for my wider boards.As well, having the front floating reduces the decelleration shocks the hinge will have to cope with from impacts with bumps etc. Whether it will cope with a full nose burying cartwheel is a different matter!
6/ My academic background is medicine, not engineering. NZ is pretty isolated in carving snowboard terms. I'm aware that there are some very knowledgeable people on the board so I'm very much interested in everyone's constructive thoughts and opinions. If the dialogue helps me and helps others better understand what plates do, so much the better.
Thanks to all who have contributed so far.
Pictures of the front unit will be few days away yet. I've got a fair amount of other work that has to be done so the workshop will have to wait.
SunSurfer
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Having watched all the different designs of plates emerging over the last year or two, I was determined to try my hand at making my own.
Of all the designs I saw and thought about, the system used by Benjamin Karl seemed the most fruitful starting point.
My aims were as follows:
Allow the board to follow its' natural curve as much as possible, eliminating the flat spots caused by attaching the bindings in the conventional manner.
Reduce the weight compared to Karl's - which appears to be made completely of aluminium.
Be able to attach the system to the conventional binding inserts on the snowboard.
A system like this needs to be hinged at both front and rear attachment points so that as the board curves, the plate moves independently of the board. Secondly, one of the hinge points needs also to slide, to allow for chord of the snowboard's arc to shorten as the curve deepens. One of the puzzles with the Karl & Apex Composites (Canadian team, not Apex Snowboards) plate systems is how
these features are accomplished.
I was aiming to make the system robust enough that wear was minimised at both the hinge and slide points.
Should I put the sliding attachment at the front or the rear of the board? My initial thought was to fix the front but a reply to a question to Jack Michaud made me go the other way - fix rear and slide front. That way the snowboard absorbs much of the energy of bumps, ruts etc. while the plate slides over the top.
Enough for now. I've been thinking, designing and beavering away over our summer in the Southern Hemisphere while you guys were carving it up in the North. I've just completed the rear attachment/hinge mechanism. (Photos attached). I hope to have this all up and running by the time our season starts in mid-late June.
The green plastic base plate is 1cm thick Ultra High Molecular Weight PolyEthylene (UHMWPE), i.e. P-tex as used in ski & snowboard soles, also as used in joint replacement bearing surfaces. The green pigment indicates that this particular version is particularly abrasion resistant.
The board I'm trialling this on has its' outermost binding inserts 50cm apart. My favoured stance is 50cm as well. The screws mounting the hinge to the plastic plate are 6cm behind the rear outermost binding insert point of the snowboard so I've used a 6 x 4cm mounting screw pattern to try balance the rotational forces from the plate once it's in use. All the bolts you can see are 6mm metric stainless steel 304 or 316 alloy.
The hinge is custom, home made, aluminium, and 18 cm wide. A local company makes an extrusion for making the hinges, 3mm thick plate (photo). It allows me to fabricate a hinge of any size I wish. The plastic sleeves that go inside the extrusion, between the hinge leaves, are also supplied by the same company. The single hinge pin is 5mm 304 alloy stainless steel, with a metric thread cut in the last few mm, and 5mm Nyloc metric nuts on the ends. The hinge needed to be slightly more than 1 cm above the board to prevent the hinge body from bottoming out on the board hence the second layer of aluminium beneath the hinge plate.
The plate with bindings attached will screwed through the 4 holes in the folded up leaves. Stainless machine screws will go through the holes to T-nuts, mounted flush in the upper surface of the plate.
The cuts in the surface of the UHMWPE are there to increase the ability of the plastic to curve with the snowboard. UHMWPE this thick is pretty stiff!
This unit demonstrates the hinge mechanism. The front unit, designed but yet to be built, will show the sliding mechanism, which has been separated from the hinge and utilises the very low friction qualities of the UHMWPE.
I'm still thinking away about possibilities/ materials for the actual plate.
Rigid vs. cambered & flexible.
Full bindings vs. just heel and toes pieces
Interested to read others comments and thoughts.
DISCLAIMER: I'm aware that I'm doing this at my own risk and I don't recommend you try this at home. What you get up to in the privacy of your own workshop is your own affair!
SunSurfer
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Front of plate slides relative to the board, now to see the rear.
SunSurfer
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http://www.youtube.com/watch?v=qse5RO-HnXc
There's an Apex plate on this "castoff" Kessler that Matt Morison's father is riding.
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From a purely mechanical point of view, in theory the Apex should work better because it has almost no footprint on the board. As far as I can tell, it basically contacts the board at two lines (bars), so the rest of the board is allowed to flex naturally. The rear bar appears to be fixed and the front bar appears to be able to slide or roll in a slot. Great concept.
Jack, I had formed the opposite view of the Apex i.e. fixed, pivoting front rod, with rear rod pivoting and sliding/rolling in a slot.
Do you believe there is an advantage to fixing rear?
I note that the photos of the F2 Conshox plate http://www.bomberonline.com/vbulletin/showpost.php?p=287268&postcount=33 shows it attached with front fixed, though I can see no structural reason why it couldn't be attached the other way.
The Karl plate appears to have predated the Apex plate in concept. It also has two narrow attachment plates across the snowboard, but I cannot tell whether both pivot points also float, or just front, or just rear.
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Born 1959.
Skater - 1970 onwards - metal wheels on the first board I rode, then started to make my own from old roller skates and laminated plywood decks. Polyurethane wheels available commercially in NZ from about 1975. Got heavily into slalom & downhill, less so into ramp/halfpipe. Still have a pair of Tracker trucks & Road Rider 4s imported from the States in 1976.
Body surfed from 1973, added a handboard from 1986 onwards. Started surfing on a surfboard at age 38 after getting my highly myopic/astigmatic eyes LASIK'd.
Skier - 1976 to 1996, still jump on two planks occasionally.
Snowboard - 1996 onwards. The instructor who gave me my first lesson couldn't understand why I wanted to angle my feet the way I'd ride a slalom skateboard. I wanted to carve from the word go, I just lacked the right equipment. First carve board was a Burton PJ 6.2, but my carving took off just two years ago when I got my hands on a 180cm Riot.
SunSurfer
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Thanks for spotting my error.
Checking FIS photos on the podium of JJA in the race that photo comes from show his board equipped with Hangl plates. I had made an assumption based on what I saw of the plate in the original photo.
I have edited the original post to just show detail of the front pivot of the Karl plate to stay strictly to the original line of thread, to show the various plate systems in use.
SunSurfer
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More photos, this time of as much detail as we have of the hinge mechanism at this stage.
All shots of this plate in action have the attachment points obscured.
Not all the plates are short to the rear. JJA has used a plate with a rear extension this season in the lead up to the Olympics.
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Screen shots taken from the video of the Apex Composites plate makers.
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Detail of the front pivot of the Karl plate.
SunSurfer
(NB: this post has been edited to correct errors, and subsequently to ensure that other board members do not look like wackos talking to themselves. See following comments.)
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When the Canadians are competing this season there's this pesky European who keeeps appearing on the podium with them. Benjamin Karl.
He has over a seasons experience riding his own decoupling plate.
Barring accidents, I expect the medals in the male PGS to include at least 1 Canadian and Karl.
SunSurfer
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Detail of front & rear pivot on the Karl Plate.
Photo help file size
in Carving Central
Posted
I've seen the photo file size limits in the attachment management area 800 x 600 for .jpg & 97.7 kB. Yet some people manage to post photos that are much bigger.
e.g. http://www.bomberonline.com/vbulletin/showpost.php?p=301087&postcount=348
This image is 972px × 940px & 330.91 kB (338,856 bytes)
It is also located at http://www.chrischabot.net/1acesharpy1.jpg
(all info available by right clicking and View Image Info in Firefox)
How do you do it?
SunSurfer