Re: Physics debate
Posted: Wed Jan 11, 2023 10:46 pm
We determined that the ball of the foot is a fulcrum and the leg is a lever, and you can lever onto the tip of the ski.
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Thanks to Tom M, we now have the test I described above for everybody to see on Youtube:Verskis wrote: ↑Tue Jan 03, 2023 7:59 amHere is one more experiment. Upper picture has the binding with springs (this could be again substituted with NNN BC with flexor, Xplore with flexor, 3-pin with bending duckbill (the duckbill is a torsional spring)).
Lower picture is exactly the same situation with horizontal force (hand) pushing the boot forward, but the binding is now just the toepiece of a TTS binding (=same as alpine touring tech binding toe part) with very low friction pins as a pivot point. With that binding, you are unable to affect the readings of the scales, as the springless binding does not transmit any torque to the ski.
suksikuva2.png
There was one thing I'd like to continue discussing with GS: with freely rotating binding (and without torsionaal spring like boot duckbills), whenever the heel is off the ski, the skier's mass(x gravity = weight) would only be able to produce normal force (perpendicular force to the ski bottom plane) at the pivot point of the binding. The front of the ski (dare I say "tip" anymore?) and the rear of the ski (aka tail) would get the exact same loading, if the ski would be symmetric front to back.GrimSurfer wrote: ↑Wed Jan 11, 2023 1:29 pm
3. The mass applied to the front of the ski is the result of pressure provided by the skier’s weight. Nothing else “creates” this mass.
Verskis wrote: ↑Fri Jan 13, 2023 5:50 pmThere was one thing I'd like to continue discussing with GS: with freely rotating binding (and without torsionaal spring like boot duckbills), whenever the heel is off the ski, the skier's mass(x gravity = weight) would only be able to produce normal force (perpendicular force to the ski bottom plane) at the pivot point of the binding. The front of the ski (dare I say "tip" anymore?) and the rear of the ski (aka tail) would get the exact same loading, if the ski would be symmetric front to back.GrimSurfer wrote: ↑Wed Jan 11, 2023 1:29 pm
3. The mass applied to the front of the ski is the result of pressure provided by the skier’s weight. Nothing else “creates” this mass.
Now with the cables or flexors or duckbills or whatever the spring system is, the skier is able to manipulate the loading of the front part of the ski versus the rear part of the ski. The total force will be the skier's weight even with the cable bindings, but not 50/50 split anymore. This is something we all have been trying to say all the time, and what is confirmed by Tom's excellent video.
I think that’s all he was trying to prove, that force gets applied to the tip, absent weight, and gravity. You didn’t seem to believe that happens. Or maybe that it happens with bumpers and duckbills but not from cables.GrimSurfer wrote: ↑Fri Jan 13, 2023 6:51 pm[
Tom’s test was appropriate for measuring the different flexors. His results yielded comparative data for this.
The method he used was t appropriate for determining weight transfer. Why? Because the vector of force applied by his assistant was wrong… it was 90 degrees from the force exerted by a skier.
People using the video as the basis for talking about tip pressure would be like NHTSA determining frontal crash standards for cars by dropping a test sled on the roof of the car.
Measuring force at one point (ends of skis) provides one data point. If the scales had been placed in various positions along the ski, we could have had some kind of discussion about forces along the length of a ski… provided we kept in mind that issue of the wrong force vectors.
I don’t expect many people to understand, or even accept, this. So I don’t intend to prolong the pain by extrapolating from a test that only achieved one thing: Providing comparative values of different flexors.
It WAS about skiing. And interesting. Except for the Sartre quotes. Zzzzzz. Should measured the cablesfisheater wrote: ↑Fri Jan 13, 2023 8:54 pm@Tom M Great video and I agree that there isn’t a best system, only a system that works best for that particular skier.
You sure have some beautiful, and just darned nice to ski terrain.
I commend you for staying above the fray. I didn’t and I apologize to the guys that didn’t need to listen to a PO’d rant, when they just wanted to read about skiing.
It’s one of those subjects, I suppose, that holds great interest to some while angering others.Lhartley wrote: ↑Fri Jan 13, 2023 9:39 pmIt WAS about skiing. And interesting. Except for the Sartre quotes. Zzzzzz. Should measured the cablesfisheater wrote: ↑Fri Jan 13, 2023 8:54 pm@Tom M Great video and I agree that there isn’t a best system, only a system that works best for that particular skier.
You sure have some beautiful, and just darned nice to ski terrain.
I commend you for staying above the fray. I didn’t and I apologize to the guys that didn’t need to listen to a PO’d rant, when they just wanted to read about skiing.
The video proves that the boot-binding-ski combination can be used as a lever to pressure the front of the ski, which you have been denying all the time.GrimSurfer wrote: ↑Fri Jan 13, 2023 6:51 pmVerskis wrote: ↑Fri Jan 13, 2023 5:50 pmThere was one thing I'd like to continue discussing with GS: with freely rotating binding (and without torsionaal spring like boot duckbills), whenever the heel is off the ski, the skier's mass(x gravity = weight) would only be able to produce normal force (perpendicular force to the ski bottom plane) at the pivot point of the binding. The front of the ski (dare I say "tip" anymore?) and the rear of the ski (aka tail) would get the exact same loading, if the ski would be symmetric front to back.GrimSurfer wrote: ↑Wed Jan 11, 2023 1:29 pm
3. The mass applied to the front of the ski is the result of pressure provided by the skier’s weight. Nothing else “creates” this mass.
Now with the cables or flexors or duckbills or whatever the spring system is, the skier is able to manipulate the loading of the front part of the ski versus the rear part of the ski. The total force will be the skier's weight even with the cable bindings, but not 50/50 split anymore. This is something we all have been trying to say all the time, and what is confirmed by Tom's excellent video.
Tom’s test was appropriate for measuring the different flexors. His results yielded comparative data for this.
The method he used was t appropriate for determining weight transfer. Why? Because the vector of force applied by his assistant was wrong… it was 90 degrees from the force exerted by a skier.
People using the video as the basis for talking about tip pressure would be like NHTSA determining frontal crash standards for cars by dropping a test sled on the roof of the car.
Measuring force at one point (ends of skis) provides one data point. If the scales had been placed in various positions along the ski, we could have had some kind of discussion about forces along the length of a ski… provided we kept in mind that issue of the wrong force vectors.
I don’t expect many people to understand, or even accept, this. So I don’t intend to prolong the pain by extrapolating from a test that only achieved one thing: Providing comparative values of different flexors.