Help with Gravity

[Jason]

Hi everyone

This is a request for help solving a bocking problem

A few people have asked me how much force is applied to the body/legs/knees when we bounce on bocks

I think I have found a way to find this out but need a few people to aid in a mass experiment so I can average the results to eliminate faulty phones and extreme bockers

First do you have an android/I-phone

If the answer is yes have a look on the free apps market and see if you can find a G-Force meter (HTC android market has one called Gforce Meter)

Next time you go bocking try and get a reading and post it here

Apart from getting an answer we coud also find out if tricks generate high G-forces (like flips)

And who will get the highest reading (might need screenshots if it gets really competitive  )

Oh and dropping your phone from a building is cheating 

Jason 

[Locky]

Since I dont have one of these phones, could you just clarify this for me.

Do you jump on your phone?

If anyone tries this could they video it for me

[Squeeker]

Will do, and lol, no locky :L

[JCDenton]

Tbh your not going to get any decent/real reading, if i held it in my hand while bocking and swung my arms SUPER HIGH G!!! Put it in my skinny jeans pocket low g, put it in my loose shorts SUPER SHOCK G!!!

Unless there is a agreed mounting point? Taped the stilts?

I have an android and am willing to tape it to my stilts FOR SCIENCE!!

[Locky]

I think taping it to the stilts is best as well.

Under the footplate?

[Jason]

  Yep thats the idea Locky (If I worked for a phone company that would be a good idea to up sales)

I am not looking for the shock to the stilts as I think this will be high JC

I am looking for the shock to the body and what effect it will have on Knees/back etc and how it compares to say trampolining (If you have a trampoline try that as well for me please)

Now as most people land with straight legs and take off in the same way a fairly secure pocket should do

Lets say jeans pocket or normal shorts ect (not to loose or tight) or even a belt mounted phone holder and tell me which so I can get an idea if it affects the results

If it stays in your pocket while bouncing it will do as when I average the results it should be fairly good

I have waved my arms franticaly with my phone and can't get it above 2.4 G so I am not expecting high figures

So thanks Squeeker and JC I will wait you numbers

Need lots more

Jason  

[JCDenton]

Soo in the pocket, but make sure it not shaking about otherwise you will get false reading... This sounds like fun 

[Squeeker]

You have encountered a problem here then Jason, different phone models must have different accelerometers and so on, because when I as waving my arms frantically, with the same app you mentioned, I got 10.7 Gs.

Also, I was planning on putting my phone in my sock as I believe it was the most secure place (for me as usually have loose shorts this time of year) and would think it would get a better measurement. Also, I found another app called AcMeter and it will give a graph, also it measures all 3D components for the G direction (x,y,z) So you would be able to tell the G's through a jump and read across to see a average, I will try and extract this graph when I come to it and post pics, If I find this difficult I may just post my analysis of the graph.

[Jason]

Right this could be a problem 

I have tried 3 apps and got 3 diferent answers for frantic waving from 2.4g to 3g max

I also got an app that tests your sensors by checking against gravity (eg it should give around 9.4 on all sides)

Mine came very close to this all between 9 and 10 and most around 9.4/5

I am working on 2g would double your weight so I think while jumping 2g--3g would be a max as if I weigh 18st I know I would buckle under 56st so the g-force can't be to high or we couldn't bock

I expect some phones to be out by quite a lot as you always get some varience but hopefully most will be around the same amount

Jason 

[JCDenton]

i got 2.42g when swinging it about..

[Jason]

That tallies with mine JC what phone were you using

The one that read over 3 g was starting with a 1g base line so it was actually showing 2.4 same as yours

I ran across an interesting article about NASA testing trampolines and they found that you could hit a max of 8g on a pro trampoline

http://www.freedomspring.com/article_nasa_studies_rebounding.html

And around 4g on those little trampette things so I will test mine on the trampoline on the weekend

But one thing that came from it was about the g-force being a lot lower for ankles/shins than running

Jason 

[Spud]

Hi,
I don't have huge amounts of experience with these apps but there was a bit of a trend in using apps like this in the air. It didn't last! Compared to the old mechanical accelerometers and artificial horizons they proved to be fairly unreliable and inaccurate. That's not to say don't bother with them. They are a very easy way of getting a ball park figure. There is an app right now which tells you wind speed. God knows how it works but it is pretty accurate!

[Jason]

Yep I thought they might be a bit out but was working on some being high and some low so an average may be fairly close

Jason 

[JCDenton]

i got 2.4g.. Maybe thats as high as my phone goes..

[Jason]

That does sound a bit like that as mine did the same 

What phone are you using mate (HTC by any chance )

Right back to the drawing board we need to find people with phones that go higher than 2.4g

Jason 

[JCDenton]

htc desire lol, getting a galaxy s II soon tho.

[Squeeker]

My phone is a Motorola Defy, and it read 8g on the ap you told me to use, and 5.5g on the other one i mentioned. However I think this is far too high because I cant see myself holding up with 5.5g's each time I stilt :L

[Jason]

Right on Squeeker

I think the 5 ish G might be closer to the truth than you think as trampolines hit up to 8g

Has either of you got access to a trampoline as it would help if you can try on that too

And is there anyone else out there willing to try

Jason 

[Squeeker]

I do not sadly

[Jason]

Well Thats just not good enough 

Go and buy one this instant 

Jason 

[Bill C.]

Hi Guys!  I am very much interested in the results of this experiment as I will be going bionic in the Fall, having both knees replaced on September 14th.  (Yes, both at the same time.)  So it is important for me to know what G-Forces the bone cement used to connect my artificial knees will have to withstand in order for me to know if I can continue bocking.  My knee surgeon's initial opinion is he sees no problem with me continuing with the sport, but frankly I would like to be sure and see some numbers.  I understand the different accelerometer apps vary in sensitivity, so I think a relative comparison of activities using each individual phone would be very helpful to me.  I would appreciate seeing the following G-forces numbers that all participants in this experiment generate in the following categories:

1) Walking down stairs without bocks
2) Jogging on hard pavement without bocks
3) Jumping up and down on hard pavement without bocks

4) Jogging with bocks
5) Jumping with bocks

Tightly wrapping the phone to the front of one's shin below the knee bar or cuff using an ace bandage or other binding would probably be the best data point location and also be safest for the phone.

Much thanks to those participating in this experiment.

Bill C.