Final Prototype & Testing

The Final Prototype

Our final prototype

Prototype Refinement

The final prototype includes some upgrades from the initial functional prototype. The improvements that are most obvious to the user are the improved ergonomic handle and grip. The handle is more streamlined and allows the user to easily grip and squeeze the handle without miscellaneous bolts and cables getting in the way.

Additionally, the final prototype has a slotted mechanism that allows for angle adjustment depending on the weight being held in the claws. This makes it easier for the user to grab the pot from down below and hang it up above because the angle position adjusts with the adding and removing of the pot.

The pulley system was removed from the final prototype and was replaced with simple loops for the cable to run through. This eliminates the risk of the cable becoming separated from the pulley and also reduces weight.

To reduce additional weight, the steel rod that connected the pole from the claws in the functional prototype was replaced with a lighter aluminum rod. This rod was welded to the stationary claw to reduce the weight added from fasteners. The claws were also reduced in width to save additional unnecessary weight.

Evaluation of Prototype

We chose to evaluate the prototype on two main metrics: weight lifting and lowering capacity and ergonomic safety.

Weight Capacity: lifting and lowering

To test the prototype’s capacity for lifting and lowering situations, we simulated a pick up location of 18″ from the floor and a hanging location of 87″. The target lifiting weight for the tool was 10 lbs, which is a typical pot with soil and flowering plant. The lifting functionality of the tool was successful up to 2.5 lbs. The lowering functionality of the tool was successful up to 5.5 lbs. We stopped testing at this point due to the lower failure limit for lifting. At this point, we identified the claw x spring mechanism as the weakness of the tool. The claw was unable to reach the necessary gripping force, therefore we could not pick-up the hanging pot.

Future iterations of the tool would improve upon this design. Possible improvements include: 1.) replacing the spring with one with more tensile force, and 2.) improving the design of the claws through material changes and hinge upgrade.

Ergonomic Safety

To assess the ergonomic safety of the tool, we performed a Rapid Entire Body Assessment (REBA). This ergonomic risk assessment tool analyzes the angles, postures, weights, and frequencies to provide a risk score for musculoskeletal injuries. The final score also provides criticality for intervention for the assessed task or job.

We looked at two tasks required in greenhouses related to hanging flower pots: picking up the pots (using an existing handmade tool, “Don’s Tool”) and hanging/lowering the pots manually.

The original pickup method, using “Don’s Tool” had a REBA score of 12, indicating a Very High Risk and to implement changes immediately. The main causes of the very high risk are the trunk position (greater than 60 degrees flexion), neck position (extension), leg position (greater than 60 degree bend), upper arm position (45 to 90 degrees with shoulder raised and upper arm abduction), and poor coupling (due to the small diameter). The new tool REBA score was 8, showing a reduction to the low end of high risk. The new tool significantly improved the upper arm positioning and coupling due to ergonomic grip, but still needs future improvements to reduce the trunk and neck bending.

The original hanging/lowering method had a REBA score of 10, indicating a High Risk and to investigate and implement changes.  The main causes of the high risk were due to neck extension, trunk extension, upper arm position (greater than 90 degrees with shoulder raised) and poor coupling (lack of handles). The original process also involved jumping and unstable base.  The new tool is a great improvement, REBA score of 2, or low risk. The neck and trunk positions were greatly improved to almost neutral positioning, the upper and lower arms with minimal movement, and good coupling due to ergonomic grip.

Overall, the tool improved in performance from the first functional prototype. The new tool allowed us to test new materials and functional mechanisms. Although it did not meet all of the targets for weight and full functionality, it is a great step in the right direction for a succesful design.