Team Prowler

Overview

Hello reader, we are Team Prowler! We are a group of engineering students who have revolutionized the prowler exercise equipment. What is a prowler, you might be asking? A prowler is a type of exercise equipment that uses weights stacked on top of a sled to create resistance as the user pushes the sled across the ground. Shown below is what a traditional prowler looks like!

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Prowlers can be used for a variety of workout routines, from lightweight sprints (less weight, fast pushing speed) to heavyweight pushes (lots of weight, slow pushing speed). Some problems with the current prowlers include the need for an extensive and expensive weight set, and that the sleds tend to tear up the terrain that they are being used on. Team Prowler’s design, the Weightless Weight Sled (WWS), removes the need for weights and operates on wheels opposed to sleds, thus maintaining a user friendly interface without the damaging sleds. The design uses a closed loop fluid system (CLFS, see Proof of Concept) to apply a braking force to the axles, which simulates the effect of the weights on a traditional prowler. Team Prowler’s design can be used in sports programs, gyms, and for personal fitness, and can be used on concrete, track, turf, and more!

Concept Overview

Throughout the Fall semester, Team Prowler has designed a prowler frame which includes a CLFS to give the user a wide range of different resistances. The design consists of a square frame with four wheels, a closed loop fluid system, two handles, and a set of sprockets accompanied by a chain. The design changed a great deal throughout the year, but the team could not be more satisfied with the final outcome. To get a better sense of the variety of ways a user can use the WWS, check out the video below!

Proof of Concept

To test whether or not the design would work, Team Prowler constructed a mock up of the Closed Loop Fluid System (CLFS). The CLFS works by turning the pump to build up pressure between the pump and the needle valve. With an increase in pressure, the pump becomes increasingly harder to turn. In the final design, the pump is attached to the axles through a series of sprockets and a chain, thus when the pump becomes more difficult to turn, the wheels become more difficult to turn as well.

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The team determined that the CLFS was the most important aspect of the design, so testing it to make sure it met all the specifications that the team desired seemed appropriate. The system consists of a fluid pump, a needle valve, a bypass valve, a pressure gauge, and a reservoir for storing oil and bleeding the system of any air. With initial testing of the CLFS, the team determined that the design would work quite well for the final design and concluded that the Proof of Concept was a success.

 Design Overview

The Weightless Weight Sled design eliminates the need for weights while maintaining a user friendly experience. The design is intended for a wide array of users, including low resistance workouts, heavy resistance workouts, endurance workouts, and quick sprint workouts. The design incorporates the CLFS from Team Prowler’s Proof of Concept, which is attached to the frame and connected to the axles through a series of sprockets and a chain. The design was intended to be easily transportable and storable, with the weight under 100 lbs and the overall size within 4 cubic feet.

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When the user pushes on the handles, the CLFS builds up pressure between the pump and the needle valve. With an increase in pressure, the pump becomes increasingly more difficult to rotate. With the pump connected to the axles through the series of sprockets and a chain, the rotation of the wheels becomes more difficult, effectively creating resistance against the user without the need for expensive weights. The amount of resistance against the user can be easily adjusted by simply turning the needle valve, where tightening the needle valve increases the resistance and loosening the needle valve decreases the resistance. The CLFS also contains a bypass valve, which can be opened to create a free-rolling sled.

Fabrication

The fabrication of the Weightless Weight Sled included a wide range of different processes. Aside from the welding of the frame, all of these processes were carried out in the Machine Shop in the basement of Palmer Engineering. The construction of the WWS was split up into three major parts; the CLFS, the frame, and the axles.

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The CLFS required quite a bit of pipe cutting, soldering, and tightening of the components to complete. The team experience most of the construction problems with the CLFS, as certain sections decided to leak quite heavily at different stages of construction. After several attempts to fix the leak, the team was finally able to create a leak free CLFS.

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The frame was welded together from four separate pieces, which were cut to size by a local steel company. Once the basic square was assembled, the handle mounts were welded onto two of the corners to support the removable handles.

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After the welding was completed, several holes were drilled into the frame so that the axles and the CLFS could be attached. The axles simply required the attachment of the wheels, sprockets, and bearings before being mounted to the underside of the frame.

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Once the frame was completely welded and the axles attached to the frame, it was time to bust out the spray paint and make it look good!

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With everything painted and assembled, the team thought the (near) final product looked quite good!

Results

After the WWS was completed and assembled, the team proceeded with testing the design to get some solid numbers. Throughout three separate trials, the team compiled the data into the graph shown below.

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As shown in the graph, the team was able to inquire around 70 pounds of resistive force in the normal direction. Although this may not seem like a lot of resistance, it is actually quite difficult of a workout. When the coefficient of friction between a traditional prowler and the ground is taken, the team is very close to an equivalent of 160 pounds of weights.

The resistances shown in the graph seem to have both exponential and linear tendencies. From 1/8 of a turn to ½ of a turn, the team saw an exponential decrease in the resistance. After ½ of a turn the team witnessed a linear decrease in the force. This is due to the changing velocities of the different valve settings. This causes unusual shifts in the resistive forces. Overall, the team could not be more satisfied with the final outcome of the WWS!

Meet the Team

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Matthew Schulze, Timothy Smith, Austin Brown, Maxwell Smith, Alysun Beard

 Maxwell Smith – Team Leader

Maxwell Smith is a Senior Mechanical Engineering student who will be graduation in the Spring of 2015. While going to school, he enjoys skiing, hiking, and camping, as well as working at the local ski company. After graduation, he will be pursuing a career in either the snowsports or architectural industry.

Timothy Smith

Timothy Smith is a Senior Mechanical Engineering student who will be graduating in 2015. While going to school, he enjoys participating in UNR’s disc golf team, skiing, hiking, and biking. After graduation, he will be pursuing a career in the energy field or the automotive industry.

Austin Brown

Austin Brown is a Senior Mechanical Engineering student who will be graduation in the Spring of 2015. In his spare time, he enjoys building custom beer pong tables. He spent the past three summers (2012-14) working at a privately owned water treatment facility in Weimar, CA, and now has an internship at a water filtration company in Reno, NV. After graduation, he will be pursuing a career in water treatment.

Matthew Schulze

Matthew Schulze is a Senior Mechanical Engineering student who will be graduating in the Spring of 2015. While going to school, he enjoys shooting, dirt biking, backpacking, and snowboarding. After graduation, he will be pursuing a career at an aftermarket parts company.

Alysun Beard

Alysun Beard is a Senior Mechanical Engineering student who will be graduating in the Spring of 2015. While going to school, she enjoys camping, snowboarding, skating, and surfing. After graduation, she will be pursuing a career in outdoor equipment product design.