G-Force?

[carvediem]

wouldn't it be cool to have a G meter on the board? :)

so you could look down and say oh that last one was a 3.6 G turn

anyway while talking about it I realized I have no idea how many Gs actually are involved in carved turns or what the maximum number of Gs that one can pull on an alpine board would be ... any ideas?

[Bullwings]

It wouldn't be very accurate unless you could some how program it to measure sustained G forces. An action like, dropping yourself onto a couch when you're tired generates something like 10+ Gs for a split instant (not sustained or else most people would pass out)...

Now if you equate this to snowboarding, if you were to do something like brake and hit some patchy snow/ice, your edge would skip along it very very roughly, which would generate very high G forces for that split instant, and would probably be higher than any Gs that you generated while carving.

[Thumper]

A lot of aerobatic airplanes have basic g-meters, you could probably velcro one between your feet that has a tattle tale and see what your max G was. For carving, my guess is about 1.5-2.0 max, if that. If it was 3 Gs, that's like your average 180 pound guy doing squats with 360 lbs (540 lbs total pounds exerted on the board.) While lots of guys may be able to exert that much force, I doubt if any could exert that much force and simultaneously retain the finesse necessary for a sustained carve. 3 G carving would be beyond spectacular to watch. Think of the trenches it would leave.

[Corey]

Interesting thought. I have a Race Technology DL1 that I'm going to be using for autocross this summer. I wonder how that would work. It assumes the frame of reference is pretty flat like a car, but I know people somehow use them on bikes.

It's a pretty expensive piece of equipment, I'd need to be 100% sure that some edge chatter wouldn't screw it up! I assume the GPS antenna would be best put on a helmet, but the helmet travels a tighter radius at slower speed than the board does...

[carvediem]

good points and suggestions ... and wasn't aware that there would possibly be G-meters out there that you could just velcro to your legs ... should be a cool little accessory though also regarding its price ...

gonna find out just for fun about how these g-meters work so far and without any knowledge about anything I thought one could possibly engineer this to be a thin pad (if that exists) that could be mounted under one's feet or rather somewhere between the boot sole and board that would simply measure the weight - add a chip and maybe bluetooth cell phone software to that to which you can input the rider's weight at first and if it's 80 kilos and the weighting pad measures 160 you did 2 Gs

or maybe fin should just develop the TDG binding that includes a G-meter

[alexgforce]

Good idea. I wouldn't mind sponsoring the development of such a gadget. I could then market it under the g-force brand

[carvediem]

:lol: right on

[martyagt4]

Get a 3 axis g-sensor, a yaw sensor, and GPS. You could do some serious data logging with that. Shame it's tough to mount some linear or string pots on your joints, be nice to see what sort of angulation you can achieve.

[Thumper]

This thing is like 4 inches deep and could be Velcroed to the snowboard itself.

http://www.aircraftspruce.com/catalog/inpages/accelerometers.php

Instruments - Accelerometers

Mechanical Accelerometers

This instrument registers "G" forces acting on the airframe during turbulence or aerobatic maneuvers. One pointer gives a continuous reading,the other 2 indicate maximum positive and negative loads. A reset knob is provided. In smooth, level flight the instrument indicates +1 "G".

Small "G" Meter

Range: -5G to +10G. Fits 2-1/4" dia. panel cutout. Weight: 0.7 lb. New Manufacture, Matte-White Dial Markings.

FALCON G-METER SMALL 2-1/4 10-09800 $227.95

[Dave*]

I seem to remember a thread along these lines from a few years back on the old BOL forums.

Many a physics formula thrown down involving speed/radius/lean angle etc.

What I seem to remember is the key points ( and they be very blurry)

- on a flat surface carving at a lean angle of 45degrees is about 1 lateral gee

( lean angle is "plumb bobbed" thru your center of gravity)

-on flat surface carving at a lean angle of 22.5 degrees is about 2.7 lateral

gee give or take a few to account for my long term memory loss.

- the gee forces go up exponentially the further over you lean

- I think the gee forces were reduced a bit as flat surface got tilted to down

hill.

No flaming thanks, just firing that from long ago vestigial memories.

Dave*

[AccidentalChef]

Aww, Dave, now you have me thinking about the physics of it all. Just when I thought the most painful semester of my life was going to completely go to waste...

Centripetal acceleration (acceleration towards the center of the circle, what we care about in this case) is described by the equation A = v^2 / r, where A is acceleration, v is velocity, and r is the radius of the turn. If we assume the radius of the turn is the same as the SCR of the board, which should be in the ballpark, pulling 1 G around a turn with a 12m radius means you're going about 24 mph. Pulling 2 G's puts you around 34 mph.

Obviously there are more variables here, but that should be a ballpark estimate. I can work out the angles some time, but now is not that time. :D

[pogokoenig]

Hmmm, is there someone seriously interested in those numbers? Luckily i am a simple minded person- only thinking in a binary way. If I am breaking down in a turn, obviously G Force was too much.

I rather would like to have an instrument for checking the alcohol promille in my blood in the early morning. When it is still abve 2.0 you should not do more than 2 linked turns.

[Surf Quebec]

From alpinecarving/technique:

Styles that transform the energy of the board into G-force. They tend to have a lower center of mass and use a more closed stance (knees together, facing more toward the nose). These styles tilt the board high on edge, so you have to worry about boot-out. They are less stable, and cannot absorb bumps well on varied terrain. These styles are used for carving complete half circles, allowing you to experience up to about 3 Gs of centripetal force.

[pogokoenig]

I am searching for this part of text in your quote, that makes only a little sense to me. I cannot find it. Have you got an idea who tha author is?

[nekdut]

Here:

http://alpinecarving.com/technique.html

:)

[Surf Quebec]

If you do not know this site (www.alpinecarving.com), I encourage you to browse the different sections.

It's a gold mine on carving information.

[r_starr]

carvediem, I cobbled together an Excel spreadsheet some years back (2003 I think) that calculates the theoretical G force using speed and sidecut radius as the input variables. I tried to upload it but got the message "invalid file." Drop me an email if you'd like a copy. FWIW, an example of the results per the spreadsheet: carving a board with a sidecut radius of 13 meters at 24.6 MPH results in 3 Gs with an edge angle of 71.4°. Always possible, probably even likely, that the SS contains errors! :) Rob

[NateW]

http://www.sparkfun.com/commerce/product_info.php?products_id=254

Put it in a box with a battery.

It would be pretty straightforward to write software for a bluetooth-enabled Windows Smartphone that would log the output. You could put it into Excel at the end of the day and plot pretty curves and stuff.

[pogokoenig]

If you do not know this site (www.alpinecarving.com), I encourage you to browse the different sections.

It's a gold mine on carving information.

Maybe it is. I know this site. But your quote - standing alone - contains at least 3 messages that are nonsense.

[Ironduck]

A number of approaches to measuring lateral acceleration have been suggested. Accelerometers are tricky to use properly in an application like ours with the vibration/chatter and changing body angles. Trying to get a reasonable estimate from speeds, side-cut radii, body angles, etc. is pretty hopeless. You have to combine too many assumptions and estimates. As an overall constraint, ‘Thumper’ makes a good point: we are only so strong. That certainly limits us to less than 3 g.

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These days, automotive performance is commonly measured with fast GPSs. The Race Technology DL1 that ‘cory_dyck’ mentioned is a good example of this. I have a similar unit: a Performance Box from Race Logic. It records data at 10 hz (10 times/sec). Its software calculates lateral acceleration. In January I got a bunch of data at Buttermilk. A typical example is shown in the following jpegs. The first is the track of the GPS antenna. Compensating for the antenna being on the helmet rather than at the center of gravity or ‘center of muscle effort’ adds about 0.1g. The second picture is of the speed (red) and lateral acceleration. The zaggy character of the graphs should be smoothed by eye to get a reasonable estimate of the peak acceleration. In this example the toe sides are about 1.3g (before adding 0.1 for the antenna position). Positive acceleration numbers are for clockwise turns (regular-toe side). The heel sides are about 1.0 g over the four turns. I also have examples of heel sides in the 1.3 range. I am not the most powerful carver around so I expect some people may be able to approach 2 g.

Overall for the hundreds of turns I measured, typical hard turns are about 1g. Speeds in the turns ranged from 20-28 mph. Turning radii were 25-40 ft. On a related note, when I let the board run, I rarely exceeded 32 mph.

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Simple and fairly accurate measurements can be made with a logging GPS and a tape measure. Email me for details if you are interested in trying this. It is not hard to do but to be reasonably accurate, it needs to be done right. Alternatively, I ride at Sugarbush North (Vt). If you are in the area, get in touch. I have plenty of duct tape for antenna mounting.

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<!--[if !supportEmptyParas]--><!--[endif]--><o></o> Bob

[Thumper]

Very cool Ironduck. In an airplane, G is measured purely in the Pitch Axis -perpindicular to the wings, force driving you straight down into the seat. In cars, cornering G is measured along the yaw axis, force pulling your head /body sideways towards the outside of the turn. For measuring carving Gs, I had been thinking in terms of force generated from our center of mass straight through our feet, like an airplane. After further thought, however, the closest analogy would be a sport bike. Specifically, the increase in sprung weight a sport bike feels in a hard corner. Kind of a combination of the two approaches.

[carvediem]

wow that is impressive data collection so I guess there are two ways to go then a suitable multi purpose GPS and tailored software for convenient data interpretation or some other from scratch hardware and software solution which seems to be hard to achieve for a double digit price ...

GPS is what some already have and can use also when it can log the course over the hill that sounds quite nice I might get one so far just wanting to know the coordinates of the flat and the nearest bar never seemed to justify that investement :D

and yeah right a lot of Gs would be too much although the thought of passing out on a turn would be sort of funny

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[bobble]

saw this web page on measuring g-forces with an accelerometer on a snowboard. kinda kool.

http://www.vernier.com/innovate/innovativeuse22.html

looks like the author is on a freeride setup. thinking that the g-forces are much more than 2.5 g's on an alpine.

[bobdea]

http://www.modmyifone.com/forums/native-iphone-ipod-touch-app-launches/127841-just-fun-gforce-meter-iphone.html

iphone solution for this

[Ironduck]

This looks like an interesting method but there appear to be a couple of differences for what we are doing. In particular the turn rate is quite high (roughly 1.6 turns per second). Presumably this is in soft snow and the turns are quite short radius. 2+Gs seems pretty high to me for a sustainted turn (but perhaps not so high for a brief inpulse).

I will see if I can get more details from the author of the article.

Bob