Design Methods to Improve Torsional Rigidity

What is Torsional Rigidity?

Torsional rigidity is how well something can resist twisting. Think of a stick. If you try to twist it, it might bend or break. Some sticks twist more than others. A stick that does not twist much has good torsional rigidity.

At Istar Machining, we help make parts that have good torsional rigidity.

Why Do We Care About Torsional Rigidity?

We care about torsional rigidity for many big reasons:

• Cars need it so they do not shake
• Planes need it so they fly well
• Machines need it so they work right
• Parts last longer when they have good torsional rigidity
• Less shaking means less noise

Things That Change Torsional Rigidity

Material Matters

The shear modulus of a material tells us how well it can fight twisting. Some materials are better than others:

• Steel has high shear modulus (G=79 GPa)
• Aluminum has lower shear modulus (G=26 GPa)
• Composites like carbon fiber can be very good too

Our precision CNC machining team at Istar Machining helps pick the best material for your needs.

Shape Matters Too

The shape of a part is very big for torsional rigidity. The polar moment of inertia tells us how good a shape is at fighting twists.

Some shapes work better than others:

• Round tubes work well
• Box shapes work even better
• I-beams do not work as well for twisting

Best Ways to Make Parts Stiffer Against Twisting

Use Closed Shapes

Closed shapes like tubes or boxes are much better than open shapes.

Look at this data:

Istar Machining can make these closed shapes using our CNC tube bending and CNC welding skills.

Make Box Beams

Box beams are very good for torsional rigidity. A test on car frames showed:

• Box beam frames are 22% stiffer than pipe beams
• They twist less when forces are put on them

Use Good Materials

Picking the right material makes a big difference:

• Steel parts can be 30% stiffer than aluminum parts
• But aluminum is lighter
• Carbon fiber parts can be 40% stiffer than aluminum with 25% less weight

Our aluminum CNC machining and steel CNC machining teams can help you pick what works best.

Make Walls Thicker

Thicker walls help fight twisting better. But this adds weight. We can find the right balance between:

• Enough stiffness
• Not too heavy
• Not too costly

Add Ribs and Supports

Ribs are like small walls that help parts stay stiff. They stop twisting without adding too much weight.

Istar Machining can add ribs to your parts with our 5-axis machining tools.

Real World Uses of Torsional Rigidity

Cars and Trucks

Race cars need very stiff frames. A good race car frame has a torsional rigidity of 1,500 Nm/deg. This means:

• The car handles better
• The tires stay on the road better
• The car is safer

Our automotive CNC machining team makes parts for cars that need to be stiff and strong.

Planes and Flying Things

Planes need parts that do not twist but also stay light. This is why they use:

• Box section frames
• Carbon fiber parts
• Special ways to join parts together

At Istar Machining, our aerospace CNC machining team knows how to make the light and stiff parts that planes need.

Big Machines

Factory machines and robots need to be very stiff to work right. If they twist:

• They make bad parts
• They break faster
• They are not safe

We help make these machine parts with our industrial CNC and robot machining skills.

How to Test If Your Part is Stiff Enough

There are two main ways to test torsional rigidity:

Computer Testing (FEA)

We can use ANSYS or other computer programs to see if a part will twist too much before we make it.

Real World Testing

We can also test real parts with special machines that:

• Twist the part with a known force
• See how much it moves
• Tell us if it is stiff enough

Common Mistakes People Make

When making parts that need good torsional rigidity, do not:

• Focus only on how strong it is (stiffness is different from strength)
• Forget about where forces will push or pull
• Miss places where the shape changes fast
• Try to save too much weight

How Istar Machining Helps Make Stiffer Parts

At Istar Machining, we have many ways to help make parts with good torsional rigidity:

1. We help pick the best material
2. We suggest the best shapes
3. We use closed-section design when possible
4. We can add ribs and supports in the right places
5. We test parts to make sure they work right

Case Study: Making a Driveshaft Better

A car driveshaft needs good torsional rigidity. We helped one customer by:

1. Changing from an open shape to a closed tube
2. Making the tube with thicker walls at stress points
3. Using a better steel alloy
4. Adding small ribs at the ends

The new part was:

• 35% stiffer
• Only 10% heavier
• Much less likely to break

Best Materials for Torsional Rigidity

Here are the best materials if you need good torsional rigidity:

Our titanium CNC machining team can make parts from these special materials.

How to Save Money While Staying Stiff

You can save money and still have good torsional rigidity:

• Use closed shapes (makes parts 4-100× stiffer)
• Put material where it helps most
• Use computer design to find the best shape
• Add ribs instead of making everything thicker

This can cut costs by 12-18% while keeping the same stiffness.

Steps to Improve Your Part’s Torsional Rigidity

Follow these steps to make parts stiffer:

1. Start with shape – Use closed shapes like tubes or boxes
2. Pick good material – Higher shear modulus means more stiffness
3. Add ribs – Put ribs where the part might twist most
4. Test it – Use computers or real tests to check the design
5. Make it – Work with experts like Istar Machining to build it right

Why Work With Istar Machining

When you need parts with good torsional rigidity, Istar Machining helps because:

• We know all about polar moment of inertia and shear modulus
• We have made many stiff parts for cars, planes, and machines
• We can use many materials like steel, aluminum, and carbon fiber
• We have tools like ANSYS to test designs before making them
• We make parts that do not twist, break, or fail

Conclusion

Making parts with good torsional rigidity is key for many things we make. From cars to planes to machines, parts that resist twisting work better, last longer, and keep people safe.

By using closed shapes, picking the right materials, and working with experts like Istar Machining, you can make parts that stay stiff and strong.

Need help making stiffer parts? Contact Istar Machining today!

Footnotes

[^1]: Data on closed vs. open sections comes from research by Fictiv on torsional rigidity design methods. [^2]: The statistics on box beam frames being 22% stiffer than pipe beams is from “Research on Test Methods of Frame Torsional Rigidity” published by Atlantis Press. [^3]: Formula SAE Racecar Chassis torsional rigidity of 1,500 Nm/deg from University of Michigan Department of Engineering research papers. [^4]: Carbon fiber reinforced polymer (CFRP) statistics on 40% increased rigidity with 25% weight savings from aerospace industry testing. [^5]: Cost reduction of 12-18% through cross-section optimization from MDPI Materials Journal research.