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The Effect of Lubricants on Mechanical Advantage

2.5 based on 6 ratings

Updated on Mar 16, 2010

Abstract

In this project I wanted to find out how lubricants affected the mechanical advantage of a pulley. To find this out I first gathered all of the needed material. Then I rigged a five-pulley system with a twelve-pound weight on the bottom. I used a spring scale to pull up the weight on the five-pulley system. I read the spring scale and recorded the ounces of weight required to lift a 12-lb. weight from the ground and recorded the number in my notebook. Then I took that number and divided it by the actual weight and got the mechanical advantage for the pulleys. Then I washed off the pulleys and added a lubricant to the axles and repeated the process.

The data shows a very small difference between each lubricant but that difference could mean the entire world if you were using a hundred pulley crane. It shows that lubricants increase the amount of mechanical advantage because they reduce friction. It also shows that the WD-40 is the best lubricant that I tested. It did the best job in reducing friction and it got the closest to the calculated mechanical advantage. By doing this it proved my hypothesis correct. It also decided the next lubricant I am going to use on my bike axle or my roller blades.

This project was a good success! It proved that WD-40 was the best lubricant that I tested and it came the closest to the calculated mechanical advantage. I chose this project because I have always been interested in pulleys and lubricants. When I started I didn't know that it would get this complex, but I rose to the challenge. It proved to be a good project and important too.

Problem

What lubricant has the most effect on the mechanical advantage of a pulley? Which one comes closest to the calculated mechanical advantage? Does friction have an effect on the mechanical advantage?

Hypothesis

I predict that in my tests I will find that the actual mechanical advantage of the pulleys will not be the same as the calculated mechanical advantage because of the friction on the pulleys. I know that the calculated mechanical advantage will be eight but I predict it will be lower for the actual test. I also predict that the best lubricant will be WD-40 because it is the slipperiest. Also WD-40 will come the closest to the calculated mechanical advantage.

Research

I learned about friction in my background reading. Friction is the heat and resistance caused when one object meets another object. Friction slows down movement. I also learned about lubricants. A lubricant is a friction reducer. The very best lubricant is the cartilage in the human body. It reduces friction 100%. How it does this is a total mystery because cartilage only works when the body is pumping blood. We have found other friction reducers. They're things that we use in our every day life, like WD-40, wax, motor oil, and soap.

In the reading I found out that a pulley has a wheel with rope or a belt passing through it. Pulleys are useful because they make pulling things easier or change the direction of the pulling. A pulley's advantage is called mechanical advantage. A pulley can be rigged in different ways, which will effect its mechanical advantage. If a pulley is hung vertically and it has more than one wheel it is called a block and tackle. If there is only one pulley and you are pulling down it is called a fixed pulley. A fixed pulley does not create mechanical advantage. It only changes the pulling direction. Another rig is a single pulley attached to the load. This pulley rig only has one pulley and you are pulling up.

Mechanical advantage is the sacrificing of distance for effort. The pulley is making you pull farther but dividing the force equally throughout the longer distance. You end up pulling further but less force is needed to pull. For example, if you have two pulleys and you lift a weight one-foot off the ground you will have to pull back two feet. Therefore you will use half the effort and the mechanical advantage is two.

Materials

One wooden frame,

Two metal hooks

Four three wheeled pulleys that have the same design

Four two wheeled pulleys that have the same design

30 feet of non-stretch rope

12 pound weight

Acme vegetable oil

WD-40

Dawn dish soap

Water supply

Spring scale with a maximum weight of 15 pounds measuring in one-ounce increments

Procedure

  1. Wash pulleys to remove any dirt or lubricants.
  2. Take the pulleys and mount them on a wood frame about two feet tall and one foot wide. Screw the hooks into the top of the wooden frame.
  3. Hang the pulley that has three wheels on the hook, putting the ring on the hook.
  4. Attach the weight to the bottom pulley that has two wheels.
  5. String rope between the hanging pulleys and the bottom pulleys starting at the bottom.
  6. Attach spring scale to the loose end of the rope and pull until the weight is off the ground.
  7. Read the number on the spring scale and record the data.
  8. Repeat steps six and seven five times.
  9. Repeat step 1 then lubricate pulleys with one of the lubricants.
  10. Repeat steps 3-7 for each lubricant.

Data

See http://www.qacps.k12.md.us/cms/sci/PROJALE1.HTM#Data

Graphs

See http://www.qacps.k12.md.us/cms/sci/PROJALE1.HTM#Graphs

Data Discussion

The data of friction table shows that WD-40 is the best lubricant with an average of 23.2 oz of effort to lift the weight. It did the very best job at reducing friction causing less drag to slow down the wheel on the pulley and making it easiest to pull. The second best lubricant was the soap with an average of 26.8 oz. of effort. This shows that it can make a good lubricant but might not be the best thing to use when lubricating important equipment like mass-producing machines. Third best lubricant that I tested was the veggie oil. That had an average of 28.6 oz. of effort. Last, the control group had average of 29 oz. of effort. These numbers show us the effect of friction on surfaces and what lubricants can do when it comes to reducing friction. This is an indicator of the lubricants reducing friction. This data also says that the WD-40 helps the pulleys come the closest to the calculated mechanical advantage if not surpass it.

The chart of mechanical advantage shows the same outcome that the friction chart does. It has WD-40 closest to the calculated advantage. This is a good result considering that there is no lubricant that completely eliminates friction. This may not seem that important because there is such a small difference, but if you were using a thousand pulleys like on a crane it would mean the world to you because that small gain in mechanical advantage would build up to be big.

Overall my hypothesis was correct because it stated that the WD-40 would lubricate the pulleys best causing them to perform closest to the calculated mechanical advantage. WD-40 was the best friction reducer. This data shows that my project was a success. It also proved my hypothesis to be a correct.

Conclusion

In this project I wanted to find out how lubricants affected the mechanical advantage of a bunch of pulleys. I set up a five-pulley system that I calculated the mechanical advantage of to be eight. I got the calculated mechanical advantage by pretending that I pulled back ten feet then divided it by how far it went off the ground. Then I actually did the tests. I had four groups, control, WD-40, Veggie oil and soap. When I got my data it showed that friction had affected the mechanical advantage of the pulleys. The WD-40 was the best lubricant because it only took an average of 23.2 oz of pulling force. The hardest group to pull was the control group that had no lubricant at all. It had an average of 29 oz of pulling force.

After I had collected all of the data I divided the ounces of pulling force it took my to pull up the 12 pound weight into 12 pounds. This calculated the mechanical advantage for each lubricant. Then I compared the calculated to the actual mechanical advantage. I found that my hypothesis was correct because the WD-40 did do the best, beating the calculated by 3 tenths. This was probably because my spring scale was only accurate to whole ounces. The WD-40 did have the most effect on the mechanical advantage. The friction affected the mechanical advantage because as my graph states the control group has the very worst mechanical advantage because the friction wasn't reduced in any way and it was most affected by friction. This just goes to show that friction does have a large affect on the mechanical advantage.

I chose this project because I have always been interested in pulleys and have wondered how they work. The information that I have gathered would be important to many people. Like a bridge engineer that has to keep his suspension cables taut with 500 pound pulling force. If he only has one man to pull the cable he wouldn't be able to create enough pull. So he has to rig up a pulley system that will increase the man's pulling force. Many jobs would need to know this information to be successful in their line of work.

Overall I think that my project was a good success and it should be further looked into. Next time that I do this kind of a project I think that I should get some more accurate equipment. Also I would do some more tests with more lubricants. From this and the data I conclude that my hypothesis was correct.

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