Gravity Driven Rolling Friction Calculation

A 1 degree slope isn't much, so I would think that the less surface contact, the better the pipe would roll; however, you would still have to use enough beams, and have them close enough together, to prevent the sched 40 from bowing or drooping.

Sounds like homework.

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Minimum surface area = minimum drag.

I can't believe how poorly you've been treated! I would certainly leave him off of next years Xmas list

For the rest of you guys to know, I am a 40 year old CAD designer and I supervise the production and manufacture of industrial furnaces. I am a 9th grade dropout with a GED. No college education, but let me tell you, I can build some nice stuff and my abilities have taken me to my current position. I am building some transfer racks and had a conversation with an engineer about the design question stated in the original post. That is why I made the post.To try to learn something either from one of you or to get linked to a site I could learn from. I am not in college nor have I ever been. If I get no answer to my question my work is still finished. We do things one way, and I just like to understand the principles behind the decisions that are made and why we do it that way, and if there could be a better way to do them. In order for me to continue to ponder this issue I was/ am in need of a little bit more information on the subject.

Thanks in advance to anyone who may try to help me understand the principles involved and how to calculate.

You would have gotten less grief if you had said that up front.

It DID sound like homework, with no explanation given.

Don't take offense, but this site offers free tutoring:

3 Types of Friction | Three Types of Friction | TutorVista.com

They may be able to give you some practical help with this problem.

1° is so little grade that things may not move at all.

Others here may be able to put it into perspective for you.

The tutoring link is good. I did not know it existed. Thanks again. Good info.

I think you are the perfect candidate for Engineering School...

In theory, friction is independent of contact area. However, if the cumulative length of the pipes actually supporting the load is small, the pipes may deform significantly.

Thanks Passingtongreen. I believe your explanation has told me what I was asking. I think if it was a perfect world and the pipe and the transfer racks were perfectly smooth and clean and strait it would not make much difference in the angle needed to roll the pipe on a solid platform or individual beams. If the materials were softer then it would be a whole different question. We would never make a transfer rack with a solid continuous surface as the pipe is never strait. I was just trying to understand the mechanics of the friction or drag between the pipe and the steel racks because of the way it was explained to me this morning. The statement you made at the end seems to be more what I was thinking with the materials we were using.

"The area of contact is not significant, it would only become significant if it was so small that it significantly strained the metal at the contact spot and made a hill to climb."

I think I can make this easier to answer, maybe. The thing I was wondering about is this:

If I roll the pipe down the 5 beams, the entire weight of the pipe is distributed on 5 support sections. That would make more force at the points of contact while rolling.

If I roll the pipe down a solid plate width = to the length of the pipe, then the weight is distributed across the entire plate. This way would seem to make less of the force in any one point of contact.

So I was looking for a method to prove which would work better or if there would even be a noticeable difference. Forgive any ignorance that present itself in my statements. I think I have a valid question and just want to understand this concept.

There should be no noticable difference, and theoretically there WILL be no difference.

The normal force is the variable here, created by the gravitational weight of the pipe.

If you use the same pipe in both cases, and both are rolling on the same specification steel, surface contact area will not affect results.

Think of it this way, the only point of contact between the round pipe and the flat flanges is the tangent line which is (theoretically) infinitely small, therefore there is no friction opposing the force of gravity, only the imperfections and/or condition of the surfaces would oppose the motion of the pipe.

In the limit if the surfaces were perfectly smooth and dirt free, it would make no difference if the flanges spanned the length of the pipe or were triangular like a knife edge (also presenting an infinitely small contact area), the pipe would roll at the same rate of acceleration due to gravity, which would be determined simply by the slope of the support.

Just think of marbles or ball bearings on a smooth surface, as soon as the surface is anything other than dead-level they roll off the edge.

Of course all this ignores the real world where imperfections, friction, dirt, and stiction come into play, but the real world results won't be much different than the theoretical world.

If you rolled on marble, the deformation of the marble would be so slight it would make little difference and the perfect pipe would probably roll irrespective of contact area.

If you roll on wood, it more readily distorts. The smaller the contact area the bigger the distortion. As noted, with large distortion of pipe OR SURFACE, the pipe will not roll readily.

Friction is the least of your worries. Distortion is a concern.

Thanks to all of you for taking the time to explain this concept. The guy I work with was telling me something opposite. And he couldn't explain it in a way that made sense to me, which started my search for the answer online and then here. I believe this one is done fellas. Thanks again. Now that I finally joined up, hopefully I can pay it forward with some answers for people within my scope of knowledge soon. *Handshakes all around.

Stick around. Maybe next time we may be asking you for help.

Try this, Texas:

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