For senior design for my Mechanical Engineering Technology degree, a group of friends and I built a portable car lift.
My father has a home shop and frequently works on many vehicles of all sizes for family and friends in his garage. One tool almost every home mechanic wants, but cannot have for various reasons, is a car lift. These reasons frequently include; cost, lack of space in the garage for storage, and ceiling height. For this project, we set out to design and build a car lift that would address these issues.
Required Specifications
We decided on individual lift platforms for each tire to be able to gain extra lift height by using the vehicle’s suspension to our advantage. We also decided on a scissor lift design to be out of the way of major drivetrain part removal and the user on a creeper when in use, and allow for a smaller footprint for storage when not in use.
Based on this, the initial design specifications were:
- Each lift platform will be rated to lift 1500 lb., with a safety factor of 2
- Each lift platform must be sized to accommodate 35″ diameter tires to be used with a Jeep Wrangler with the Rubicon off-road package
- Must be able to lift underside of the vehicle at least 24″ off of the ground
- Budget of $1500
Design Work
We spent about a month and a half working on design using 3D modeling and simulation software. It was decided that a scissor lift with hydraulics would be the easiest and strongest method to meet our design goals. We configured the cylinder in a pulling configuration rather than the more typical pushing configuration to shorten the overall design, resulting significant storage space and weight savings.
We also chose an air-over-hydraulic pump as a power source as it is easy to operate with a foot pedal, and can be powered by an air compressor commonly owned by home mechanics.
Fabrication
Fabrication occurred over several weekends. 10′ and 20′ sticks of angle iron and tubing were cut to length, and then holes for the attachment points and hydraulic line pass-throughs were drilled according to the design prints.
The upper and lower frames were then welded together using jigs to ensure consistency.
The mounts for the base of the hydraulic cylinders consisted of 2″ x 2″ x 1/4″ square tubing, with 2 brackets welded to the tubes. Each of these brackets were cut out on a CNC plasma table by a family friend. This mounting subassembly was then welded into the bottom frame. Another copy of this subassembly was welded between the scissor arms to form the upper cylinder mounting point.
Custom Wheel Fabrication
Each lift platform requires 4 wheels that allow the scissor arms to move. Upon research, we found that the type of wheels we needed, solid steel for strength and 1 inch wide, were not readily available for purchase. The wheels found were all of the cast variety, which did not have the weight capacity required. The decision was then made to fabricate the wheels ourselves from A36 round bar.
First, the round bar was rounded off by a few passes on the lathe and taken down to its final diameter of 1.75”. Once the bar was verified as the proper diameter, it was taken to the band saw where it was cut into 1 1/8” wide blanks. These blanks were then milled down to the final 1” thickness. Then the blanks were put back on the lathe, center-drilled, and had small chamfers added to each side. The blanks were then moved to the drill press for the final steps. The center axle hole was drilled, and then a countersink tool was used to add chamfers to either side of the center hole.
Testing
After fabrication was complete, we performed a series of tests that were of escalating difficulty. Starting with basic functionality testing using concrete blocks as a small load. This was to ensure proper assembly and that nothing was bound up during movement.
This then escalated to a small compact car to verify the design maximum lift height, later followed by a large SUV to verify weight capacity.
Conclusion
As a one semester senior design project, this was an extremely challenging yet rewarding experience. Most of the challenge was due to the short timeframe. However, we were able to meet nearly every design metric we set for ourselves, and came in roughly 30% under budget.
We built this lifting system originally in 2016, and it is holding up well to long term use. It is still used regularly to assist in repairs of a wide array of vehicles.
