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Just a nice experiment; comment in Russian is obvious
AI Thread Summary
The discussion highlights an experiment involving pull rolls for a paper napkin folder, where the goal was to avoid pinching the paper to preserve the emboss pattern. The initial proof of concept used larger rolls with tread tape, which functioned effectively. However, when the machine operated at high speeds of 1000 FPM, the smaller knurled steel rolls stopped pulling due to centrifugal force equaling the back tension. To resolve this, the gap between the pull rolls was adjusted to ensure proper nipping of the paper. Ultimately, while the design required an operator adjustment, the machine was able to function as intended.
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.Scott
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At highway speeds, steel belted radials are often heavy enough to stay round even after a blow out.
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jrmichler
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I once got tripped up by exactly that effect. The project was pull rolls for a paper napkin folder. We did not want to pinch the paper between a pair of rolls because that could squash the emboss pattern, so we tried a pair of S-wrapped rolls similar to the diagram below.
The input roll of the folder grabbed the paper using vacuum, so could only pull with about 0.3 lbs force. The necessary tension at that point was about 3 lbs in order to keep the web taut after the embosser, and pull it over the folding plows. The tension increase is provided by pull rolls. The proof of concept test used a pair of scrounged rolls about 12" diameter covered with tread tape. It worked perfectly. The actual rolls were about 4" diameter knurled steel. The measured coefficient of friction was 1.7 to 2.0 with the tread tape, and about 0.4 with the knurled steel.
When the machine got up to speed, about 1000 FPM, the pull rolls stopped pulling. It turned out that the centrifugal force was equal to the back tension at that speed with the smaller rolls. The design was locked in by that point, so we adjusted the gap between the pull rolls to nip the paper just enough to make it work. We had hoped to eliminate an operator adjustment, but at least the machine worked.
The input roll of the folder grabbed the paper using vacuum, so could only pull with about 0.3 lbs force. The necessary tension at that point was about 3 lbs in order to keep the web taut after the embosser, and pull it over the folding plows. The tension increase is provided by pull rolls. The proof of concept test used a pair of scrounged rolls about 12" diameter covered with tread tape. It worked perfectly. The actual rolls were about 4" diameter knurled steel. The measured coefficient of friction was 1.7 to 2.0 with the tread tape, and about 0.4 with the knurled steel.
When the machine got up to speed, about 1000 FPM, the pull rolls stopped pulling. It turned out that the centrifugal force was equal to the back tension at that speed with the smaller rolls. The design was locked in by that point, so we adjusted the gap between the pull rolls to nip the paper just enough to make it work. We had hoped to eliminate an operator adjustment, but at least the machine worked.
The rope is tied into the person (the load of 200 pounds) and the rope goes up from the person to a fixed pulley and back down to his hands. He hauls the rope to suspend himself in the air. What is the mechanical advantage of the system? The person will indeed only have to lift half of his body weight (roughly 100 pounds) because he now lessened the load by that same amount. This APPEARS to be a 2:1 because he can hold himself with half the force, but my question is: is that mechanical...
Some physics textbook writer told me that Newton's first law applies only on bodies that feel no interactions at all. He said that if a body is on rest or moves in constant velocity, there is no external force acting on it. But I have heard another form of the law that says the net force acting on a body must be zero. This means there is interactions involved after all. So which one is correct?
Hello!
I have a question regarding a beam on an inclined plane. I was considering a beam resting on two supports attached to an inclined plane. I was almost sure that the lower support must be more loaded. My imagination about this problem is shown in the picture below.
Here is how I wrote the condition of equilibrium forces:
$$
\begin{cases}
F_{g\parallel}=F_{t1}+F_{t2}, \\
F_{g\perp}=F_{r1}+F_{r2}
\end{cases}.
$$
On the other hand...
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