Please stay on the trail.

FAQ and threads for those just starting to hike the Colorado 14ers.
User avatar
cheeseburglar
Posts: 2734
Joined: 8/7/2006
14er Checklist (58)
14ers in Winter (2)
13er Checklist (73)

Re: Please stay on the trail.

Postby cheeseburglar » Mon Oct 01, 2012 7:39 pm

After 9 of us stormed Fortress Peak on Saturday, which is some obscure 13er hill somewhere in the wilderness, there should be a trail.
Please follow it.
The marmot said “Nobody is perfect and you are not nobody.”

Random FoTH Quotes
User avatar
ajkagy
Posts: 2661
Joined: 1/7/2007
14er Checklist Not Entered
Contact:

Re: Please stay on the trail.

Postby ajkagy » Mon Oct 01, 2012 8:43 pm

Dex wrote:
mtnfiend wrote:
Now that we've got that solved, we can go back to ridiculing people for not staying on the trail........or bean can keep posting topless photos of himself (I'd wouldn't post that kind of stuff on the interwebz if I were you, but that's your deal). [-(



The issue isn't about the PSI in the tire. It is about the PSI on the ground - bike tire vs a hiker's foot.

I know it is getting late but, let's try to focus.


weight (bike + rider + gear) / surface area in inches touching ground = ground PSI

pretty simple. Sorry, but just because you have 20 or 30 PSI of air in the tire doesn't mean there is that much PSI touching the ground. The PSI in the tire is the outward pressure force of the air pushing against the rubber in the tire. Think of it this way...if I have a high pressure air tank with 5000 PSI of air in the tank laying on the ground, it's not putting 5000 PSI against the ground, lol
User avatar
cheeseburglar
Posts: 2734
Joined: 8/7/2006
14er Checklist (58)
14ers in Winter (2)
13er Checklist (73)

Re: Please stay on the trail.

Postby cheeseburglar » Mon Oct 01, 2012 8:57 pm

I thought all hikers hate mountain bikers because of their scheme to make everyone leash their dogs.
The marmot said “Nobody is perfect and you are not nobody.”

Random FoTH Quotes
User avatar
MUni Rider
Posts: 953
Joined: 7/31/2007
14er Checklist (49)
Contact:

Re: Please stay on the trail.

Postby MUni Rider » Mon Oct 01, 2012 9:16 pm

mtnfiend wrote:Well, all is right with the world.....it seems Bean is correct. It's not intuitive or obvious at first, but I had to put pen to paper to convince myself or loose my sanity (I mean honestly, Bean can't be right, can he??).

90 kg person+bike (~200 lbs). I weight about 165lbs and my bike is roughly 35lbs (heavy I know, but it's old and I'd rather spend my money on ski gear).

Since Newton was the pimp-daddy of math and calculus: F=ma; so 90kg*9.8m/s^2. = 882N.

P=F/A, rearrange to solve for area; A=F/P. I measured the pressure in my rear tire at 18 psi (124,105 Pa).

Solving for area; A = 882N/124,105N/m^2 = .0071 m^2 (~11 in^2).

I'll admit, when I first ran the calc, 11 square inches seemed absurd especially since the width of my tire is roughly 2" (meaning the contact length would need to be about 5.5 in). I know tires deform, but that much seems ridiculous, right??

I sat on my bike with as much weight on the back tire as possible (the calc above assumes 1 tire is carrying all the weight) and had my wife mark the contact length on the garage floor (slid a straight edge under the front and back of the rear tire until it touched the tire, then marked the location with a sharpie).

Measuring the distance between the 2 marks yielded 5.75 in. - means good enough for government work.

Now that we've got that solved, we can go back to ridiculing people for not staying on the trail........or bean can keep posting topless photos of himself (I'd wouldn't post that kind of stuff on the interwebz if I were you, but that's your deal). [-(


I knew I remembered this whole argument somewhere else before. LOL!

"It's a simple question of weight ratios! A five ounce bird could not carry a one pound coconut."

"In order to maintain airspeed velocity, a swallow needs to beat its wings forty-three times every second, right?"

http://www.youtube.com/watch?v=rzcLQRXW6B0
"It is not the critic who counts, not the man who points out how the strong man stumbled, or where the doer of deeds could have done better. The credit belongs to the man who is actually in the arena; whose face is marred by the dust and sweat and blood; who strives valiantly; who errs and comes short again and again; who knows the great enthusiasms, the great devotions and spends himself in a worthy course; who at the best, knows in the end the triumph of high achievement, and who, at worst, if he fails, at least fails while daring greatly; so that his place shall never be with those cold and timid souls who know neither victory or defeat." (Theodore Roosevelt)

"Wilderness is not a luxury but a necessity of the human spirit." (Edward Abbey)
User avatar
mtnfiend
Posts: 276
Joined: 2/13/2010
14er Checklist (31)
14ers Skied (9)
14ers in Winter (2)
13er Checklist (129)
Contact:

Re: Please stay on the trail.

Postby mtnfiend » Mon Oct 01, 2012 9:37 pm

I can't believe I'm doing this....

Dex wrote:The issue isn't about the PSI in the tire. It is about the PSI on the ground - bike tire vs a hiker's foot.


Yes, that was one of my immediate thoughts as well. I know the math I posted above is simplified, but please, please, post a mathematical solution that contradicts my above. Please!!

ajkagy wrote:weight (bike + rider + gear) / surface area in inches touching ground = ground PSI

pretty simple. Sorry, but just because you have 20 or 30 PSI of air in the tire doesn't mean there is that much PSI touching the ground. The PSI in the tire is the outward pressure force of the air pushing against the rubber in the tire. Think of it this way...if I have a high pressure air tank with 5000 PSI of air in the tank laying on the ground, it's not putting 5000 PSI against the ground, lol


I like your thought process ajkagy, and it is that simple. Although the high pressure gas cylinder is not a straight apples to apples comparison. A high pressure gas cylinder is a rigid structure, quite unlike a tire, and that is exactly why I set out to measure the contact area of my bike while it had a known force on it. To determine the pressure I exert on the ground, I have to know my force (not weight - although they are sometimes the same quantity) and the contact area. Perhaps the experiment was overly simplified and there was certainly some error in the measurements, but please put pen to paper and explain why the math above is incorrect. It would be a very strange coincidence that the measured pressure and contact area would be so close to the calculated values - I'm not talking about just being in the ball park here, I'm talking about being in the same section of the ball park!!

But actually isn't this discussion a little contrived?? We are talking about the pressure on dirt here. Does dirt get offended or hurt when it gets stepped on?? Are we engineering some sky scraper, road, or bridge??
Didn't I ever tell you.....Bumble's bounce!!!

http://exploringtherockies.com/
http://www.berthoudpass.org
@snow_nerd
User avatar
DeucesWild
Posts: 624
Joined: 9/12/2011
14er Checklist (58)
14ers in Winter (1)
13er Checklist (1)

Re: Please stay on the trail.

Postby DeucesWild » Mon Oct 01, 2012 9:47 pm

Although I haven't read every post, I don't recall any mention made of: weight = mass x acceleration

The bike isn't sitting still.
Snowflakes, Uber Alles!

www.deuceIRA.com. Put the Douche in your FiDeuceiary needs today!!
HikerGuy
Posts: 456
Joined: 5/25/2006
14er Checklist (58)
13er Checklist (17)

Re: Please stay on the trail.

Postby HikerGuy » Mon Oct 01, 2012 9:57 pm

I think the more serious concern is not some braided trail on a mountain, but the lack of science education in this country.
User avatar
wildlobo71
Posts: 2173
Joined: 4/1/2008
14er Checklist (58)
14ers in Winter (6)
13er Checklist (40)

Re: Please stay on the trail.

Postby wildlobo71 » Mon Oct 01, 2012 10:22 pm

HikerGuy wrote:I think the more serious concern is not some braided trail on a mountain, but the lack of science education in this country.


:lol: May the FORCE be with you, Deuce.
You've never really stopped even if you feel like you have.
User avatar
crossfitter
Posts: 893
Joined: 7/7/2009
14er Checklist Not Entered

Re: Please stay on the trail.

Postby crossfitter » Mon Oct 01, 2012 10:38 pm

ajkagy wrote:Think of it this way...if I have a high pressure air tank with 5000 PSI of air in the tank laying on the ground, it's not putting 5000 PSI against the ground, lol


And you've found the real key here. Pressures do not necessarily need to be balanced but forces do. I'll leave the math up as an exercise to the reader, but the total force exerted on the ground is a combination of the internal pressure*contact area and the load carried by the structure. In the air tank example, the steel structure carries nearly the entire load whereas in a balloon almost none of the load is carried by the walls. In a bike tire that distribution will fall somewhere in between but I would hazard a guess that not much load is carried by the tire walls.

However, analyzing static forces isn't particularly useful or accurate. Shear forces which easily redistribute soil and rock contribute far more to erosion than simple compression, and that analysis gets harder to do on the back of an envelope. A bike may not be any worse than a person if it is rolling, but what about when the rider slams on the brakes? The easiest way to settle this is to look at erosion on bike paths vs. hiking trails while normalizing for usage.

Then again, Elbert is already a cattle trail so....eh, whatever.
- A mountain is not a checkbox to be ticked
- Alpinism and mountaineering are not restricted to 14,000 foot mountains
- Judgment and experience are the two most important pieces of gear you own
- Being honest to yourself and others about your abilities is a characteristic of experienced climbers
- Courage cannot be bought at REI or carried with you in your rucksack

User avatar
Bean
Posts: 2742
Joined: 11/2/2005
14er Checklist (29)
14ers Skied (28)
14ers in Winter (8)
13er Checklist (7)
Contact:

Re: Please stay on the trail.

Postby Bean » Tue Oct 02, 2012 6:22 am

Dex wrote:
mtnfiend wrote:I can't believe I'm doing this....

Dex wrote:The issue isn't about the PSI in the tire. It is about the PSI on the ground - bike tire vs a hiker's foot.


Yes, that was one of my immediate thoughts as well. I know the math I posted above is simplified, but please, please, post a mathematical solution that contradicts my above. Please!!



Of course I could write a formula, and it would properly take into account, mass, speed, footprint, and tire construction (an important factor not mentioned so far). Then I would compare that with a hiker with the same variables - except switch out tires for boots.

But, if I did that; what would you do today?

I'm pretty sure people have done thesis-level papers on this subject. We are but amateurs (at best) touching only the surface of the issue.
"There are no hard 14ers, but some are easier than others." - Scott P
http://throughpolarizedeyes.com
User avatar
ajkagy
Posts: 2661
Joined: 1/7/2007
14er Checklist Not Entered
Contact:

Re: Please stay on the trail.

Postby ajkagy » Tue Oct 02, 2012 6:34 am

mtnfiend wrote:I like your thought process ajkagy, and it is that simple. Although the high pressure gas cylinder is not a straight apples to apples comparison. A high pressure gas cylinder is a rigid structure, quite unlike a tire, and that is exactly why I set out to measure the contact area of my bike while it had a known force on it. To determine the pressure I exert on the ground, I have to know my force (not weight - although they are sometimes the same quantity) and the contact area.


yea the gas cylinder was a bad comparison since the strength of the steel/carbon is pushing bad equally on the gas in the cylinder. Same with the tire walls in the bike tire and i imagine the PSI inside the tire is a bit more once it's bearing weight and compressing the overall volume inside the tire :)

regardless, people need to quit picking on bikers :-D
User avatar
tlongpine
Posts: 814
Joined: 1/10/2011
14er Checklist (26)
14ers Skied (1)
14ers in Winter (2)
13er Checklist (4)

Re: Please stay on the trail.

Postby tlongpine » Tue Oct 02, 2012 7:18 am

TallGrass wrote:
tlongpine wrote:The discussion isn't a question about what is causing the erosion, the question is how to mitigate it.

So we have to mitigate erosion without understanding the cause(s)? How does that process go?


No, sophist. The causes are understand: poor trail engineering that is ill suited for any user type.

The science is in. You can't presume the rest of this forum is as clueless as you are (or stuck at the same step of the process of inquiry) because you haven't read it. Please, before posting more condescending rhetorical questions, read it: http://www.imba.com/resources/research/trail-science
I am unable to walk away from the mountain without climbing it. An unclimbed mountain tugs at my consciousness with the eternal weight of time itself. Until I've pressed my face into it's alpine winds, hugged it's ancient granite walls, and put it's weathered summit beneath my heal I'm unable to resist it's attraction.Knowing nature gives the mountain more time than she gives us adds urgency to the obsession. As has been said before; the mountain doesn't care.

It can wait forever. I cannot.

Return to “Just Starting? Info for 14er Beginners”

Who is online

Users browsing this forum: No registered users and 4 guests