P16006: Tub Lift 2

Preliminary Detailed Design

Table of Contents

Team Vision for Preliminary Detailed Design Phase

Our team performed the second iteration of our design and engineering analysis to assess the feasibility of the designs we had proposed. Large amounts of progress has been made in the regards to developing the swivel and main lift system. Stress analysis was performed on the lift system using ANSYS.

Simulated Design Concept

The following animation displays the motion of a three-arm linkage design, which we will be utilizing as our lifting mechanism.


Source Video:


Engineering Analysis


In a typical cylindrical piston, the parameters for consideration are the bore size as well as the stroke length. The bore corresponds to the piston's diameter, while the stroke length pertains to how far the piston can extend. For clarity, these concepts are depicted below.




To download the piston analysis, please click the following:

Piston Analysis

ANSYS Stress Analysis

An ANSYS stress analysis was conducted in order to evaluate the impact of the forces on the lift on its structural integrity. The visual depictions can be seen below. As you can see from the graphics we're experiencing max stress at the pin connections beneath the chair plate which is expected. Originally the chair plate was going to be made of aluminum, similar to the gross majority of the structure, but the system failed in the back corners causing it to become warped and drastically deformed inwards at the center. Therefore we opted to simulate the system with a stronger material for the chair plate, steel. With a steel plate the max stress experienced at the bolts are 71428 psi, and the ultimate yield of steel is 84800 leaving us with a FOS of 1.2.



To download the relevant file for the ANSYS analysis, please click the following:

ANSYS Analysis

Design Drawings & Documentation

Tub Lift Assembly

The tub lift assembly is responsible for both the lowering and raising of a user into and out of the tub and incorporates a seat that is capable of swiveling. Under normal circumstances, the swivel can be operated manually. However, we have also made a swivel assist that can be used to aid the user. The lifting mechanism itself is powered hydraulically and utilizes pistons to guide the lift up and down.


To view or download the relevant design drawings, please click the following:


To download the relevant CAD files, please click the following:

Final Lift Assembly

Swivel Assist Assembly

The swivel assist assembly is a separate entity whose purpose is to assist the user with the rotation of the tub lift seat (such that it does not have to be manual). It clamps onto the side of the bathtub and is powered via battery. The assembly attaches itself at a point on the tub lift via a drop pin.



To view or download the relevant design drawings, please click the following:


To download the relevant CAD files, please click the following:

Swivel Assist

Bill of Material (BOM)



To download the tenative bill of materials, click the following:

Tentative Bill of Materials

Test Plans


To download the test plan file, please click the following:

Test Plans

Risk Assessment


Please click the following link to download:

Risk management Assessment

Vendor Information


Please click the following link to download:

Vendor Information

Plans for next phase


Please refer to the following attachments to view individual plans for the next phase of the project:

Branch - Detailed Design Plan
Hall - Detailed Design Plan
Krall - Detailed Design Plan
Swearingen - Detailed Design Plan

Template: Individual 3-week Plan Template

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