PETER NOH     MET     CWU

This project was motivated by a need for a device that would securely support the weight of late model vehicles without the use of traditional jack stands. Unlike vehicles of the past, the underbodies of modern vehicles are covered in various plastic covers and skid plates. These plastic covers and skid plates are in place to protect the chassis as well as every major component under the vehicle from debris and corrosion. The downside to the integration of these protective covers on modern vehicles is that it creates a problem for the average DIY’er. The covers obstruct the access to traditional points where a floor jack would be used to lift the vehicle. These lift points are control arms, frame or rear differential. Modern vehicles have specific jack points that usually run along the sides of the vehicle, directly behind the front wheels and in front of the rear wheels. The problem with these jack points is that they are too small of an area. There is not enough room on the jack point to use a jack to lift the vehicle and also place a jack stand to securely support the weight of the vehicle when servicing. Modern vehicles inhibit the DIY weekend mechanic the ability to utilize traditional jack stands. This poses a serious safety risk as one should never work under or around a vehicle that is not securely supported.

A hub stand would eliminate the need for traditional jack stands to support the vehicle as well as the risk of servicing a vehicle only supported by a hydraulic jack. The vehicle needing service would be raised up using a normal floor jack at the factory designated jack points as intended. The hub stand would then attach directly to the hub of the vehicle (with the wheels off) using the factory lug bolts or nuts, depending on application. The floor jack could then be lowered and removed and the hub stand would securely support the weight of the vehicle. Other applications of hub stands include long-term storage and more precise wheel alignments. During long-term vehicle storage, the vehicle is raised off the ground so that the tires will not form a flat spot. However, raising the vehicle and letting the suspension components suspend freely for an extended time creates wear and tear. Hub stands would solve these issues. As for more precise wheel alignments, the absence of tires on the vehicle inevitably creates a better setting for alignments due to the elimination of tire deflection. Camber, caster, toe, corner weight balancing and ride height adjustability can all be completed more efficiently and effectively using hub stands. The hub stand solves the problem of not being able to use traditional jack stands on modern vehicles and provides improved long-term vehicle storage and suspension adjustment solutions. 

The hub stand will meet the following requirements.

• The hub stand must weigh less than 21 lbs.

• The hub stand must support 1.5 tons (3000 lbs.)

• The hub stand must accept 5x112 and 5x100 bolt patterns.

• The hub stand must have a center bore size of 77 mm.

• The hub stand must have a minimum height of 18 in.

• The hub stand must have a maximum height of 22 in.

• The hub stand must have a maximum width of 11 in.

• The hub stand must be height adjustable at increments of 1 in.

• The hub stand must pivot up to 3 degrees in all axes for suspension alignment adjustments (caster, camber and toe).

• The hub stand must cost less than $150.

• The hub stand must be made of non-corrosive material.

• The hub stand must be able to perform at a minimum temperature of 20 degrees F.

• The hub stand must meet all government and industry safety standards.

PROJECT SCOPE

 The goal of this project will be due to design and manufacture a set of four hub stands. The hub stand will be designed using SolidWorks and manufactured using various machines available at Central Washington University’s machine shop. 

DESIGN AND ANALYSIS

Appendix A3 shows the material properties of 6061-T6 Aluminum. This material was chosen because of its high yield strength of 40 ksi and a suitable ductility of 17%. 6061-T6 Aluminum is known for its excellent joining characteristics and good acceptance of coatings. It possesses high strength, good workability and high resistance to corrosion. Most importantly, it is widely available.

As referenced in Appendix A1, the allowable load of a 6061-T6 aluminum square tube was calculated. A column analysis was done using the J.B. Johnson Formula [1]. The dimension of the square tubing in question was 2.5” x 0.25” and length of 8”. The slenderness ratio was calculated as 5.63 and column constant was 70.3. Because the slenderness ratio was less than the column constant, the short column analysis was completed. The critical load was calculated as 89,711 lbs. and with a safety factor of 1.5; the allowable load was 59,807 lbs. This calculation demonstrates that the above dimensioned aluminum square tubing will support the 3,000 lb. design requirement.

Appendix A2 shows the calculation for critical stress that the hub stand central frame can withstand. The formula for critical stress is: σ_cr=P_cr/Area. The critical stress was calculated to be 39,872 psi. This figure was below the yield stress of 6061-T6 Aluminum (40 ksi) so the material was deemed suitable.

Appendix A4 shows the calculation for the maximum vertical shearing stress on the hub stand central frame. Again, the hub stand central frame is made up of a square tube that is 8” in length and width of 2.5”. The formula for maximum vertical shear stress is: τ=V/I  Q/t, where I is the moment of inertia, t is the width, V is the load and Q is the first moment. The maximum vertical shearing stress was calculated as 12.5 ksi. Dividing the maximum vertical shearing stress by the design factor of 1.5, the allowable vertical shearing stress was calculated as 8.3 ksi. 8.3 ksi is less than the yield strength of 6061-T6 Aluminum (40 ksi) and thus is appropriate.

Appendix A5 shows the calculation for choosing the appropriate pin diameter to hold the 3000 lb. load. The formula used was τ_allow=F/A, where A=π/4 d^2. Solving for d, the minimum diameter to withstand 3000 lbs. of force and 8.3 ksi shear stress was 0.678 in. The pin diameter was rounded up to ¾” because they are commercially available.

Appendix A6 shows the calculation for the maximum compressive stress on the hub plate. The hub plate is 6” in diameter and 1” thick. It possesses 5 bolt holes, evenly spaced on a 112 mm diameter circle. The diameter of each bolt hole is 5/8”. The center bore diameter is 77 mm. Using stress concentration factor curves [1] (Figure 3-26 Pg. 115 Mott, 2014) the maximum stress of the hub plate was calculated as 6,985 psi.

As seen in appendix A7, the maximum bending stress on the base plate was calculated using the formula σ_max=MC/I. The base plate is rectangular with a 10” length and 7” width and 0.75” thickness. The base plate will encounter a bending stress due to the 3 degrees of pivot that the hub stand will be capable of. The max bending stress of the base plate was calculated as 11.2 ksi, which is less than the yield stress of 6061-T6 (40 ksi).

Appendix A8 shows the calculation of the maximum bending stress on the hub stand frame. The dimensions of the square tube that makes up the hub stand frame is 2.5” x 2.0” x 8”. The load that it will encounter is 3000 lbs. The formula used to calculate the maximum bending stress in the frame was σ_max=MC/I which came out to be 7,813 psi.  

Appendix A9 details the required minimum leg size for the weldments needed to join the hub stand central frame to the base plate and the hub plate to the hub stand member. According to Mott, 2014 [1] a 3/8” fillet weld is necessary for plates greater than 1 ½” to 2 ¼” inches thick. The weldment will go all the way around.

Device Assembly, Attachments:

The hub stand will be manufactured from 6061-T6 Aluminum and consists of the following parts.

Part 1: Hub Plate

Part 2: Hub Plate Member

Part 3: Hub Stand Central Frame

Part 4: Base Plate

Part 5: Hitch Pin/Cotter Pin

Part 6: Spring loaded roller balls

Part 7: Screw Bolts

Part 8: Locknut

COST AND BUDGET

The total material cost for 4 hub stands is $576.22. The materials and parts necessary for this project came from OnlineMetals.com and McMASTER-CARR. All materials were ordered online.There will be no labor costs associated with manufacturing the hub stand. All machining and welding operations was done with the resources available at CWU. The project came out under budget due to the fact that only one hub stand was manufactured. The total cost came out to be less than $220.

SCHEDULE

The estimated total hours for this project was 137 hours. I completed the project on schedule and spent a total of 97 hours. See Gantt Chart.