How The Ford Model T’s Suspension Made It Perfect For Terrible Roads: Suspension Secrets

My fellow Autopians. Welcome to a new series we are calling Suspension Secrets. In this series, we’ll look at some of the most iconic and influential suspension designs of all time, diving deep into each to show how it works. We’ll start with what is arguably the most influential car ever been produced, the Ford Model T, a spindly-little vehicle that somehow had a suspension known for tackling the harshest of terrains. Here’s how it worked.

Commonly known at the time as the “Flivver” and “Tin Lizzie,” the first Model T was delivered on October 1, 1908, and production continued until May 1927. During that time, over 15 million were built — a production record that stood until the VW Beetle took the title in 1972.

[Ed Note: This is a bit of a dream series for us, and there’s no better person in the world to write it than Huibert Mees, the suspension designer who led the design of the original Tesla Model S, the 2005 Ford GT, and other great cars. He’s written a lot about suspensions for us and will be leading this series. He’s also just a cool guy. – DT]

Here’s Us Breaking Down The Suspension:

Above is the video we made walking through the entire Model T suspension. Please enjoy it, like it, share with it friends, embed it on your websites, comment, et cetera.

Some Background On The Model T Before We Get Nerdy

What made the Model T so successful was a combination of low cost, durability, and simple maintenance. Henry Ford grew up on a farm, and spent much of his time repairing equipment. He valued simplicity, durability and ease of repair, so he wanted to make sure his products embodied those principles. You see this in every aspect of the T, from the design of the engine and transmission to the suspension.

The first Model Ts were built in the Piquet Avenue Plant in Detroit MI. This facility was not capable of building many cars per day, so after producing around 12,000 cars by 1910, production moved to the much larger Highland Park plant where Ford introduced the moving assembly line. While not the first to use this innovation (that distinction belongs to Ransom E. Olds of Oldsmobile fame), Ford refined the system, which led to a steady decline in manufacturing costs, which resulted in a lower price for consumers. At the car’s introduction in 1908, the Roadster cost $825 (equivalent to about $27,000 today). By 1925, the price had dropped to $260 (less than $4,500 today), and Ford was producing around 2 million cars per year.

There is a famous saying attributed to Henry Ford that you could get a Model T in any color you like as long as it is black. While black was indeed the only color you get for a Model T for the majority of production, this wasn’t true for the first few years. In fact, from 1908 through 1913, black wasn’t even a choice! However, to help keep costs down, from 1914 through 1925, all Model T’s were produced in black. Ford bowed to market pressures and began offering other colors again in 1925, although your choice was limited to blue, red, green, or grey.

All of this is to say: The Model T was a no-frills machine that just had to work, even when things got rough.

Two Huge Rigid Triangles Pivot Around A Ball Joint, Let The Model T Flex Like An Off-Roader

 

So simplicity was the name of the game for the Model T, and this is no more evident than in the design of the suspension. The front and rear suspensions are identical in their concept, and only differ in the fact that the rear has to include a driven axle and driveshaft. (The Model T is rear-wheel drive).

Both suspensions consist of a single triangular-shaped assembly made up of several parts bolted together. The stick axle that the wheels bolt to make up one side of each triangle, while two big metal “radius rods” spanning from the outside of each stick axle inwards make up the other two sides, and meet at a pivoting joint.

There are no upper or lower control arms. No toe links or anti-roll bars. In fact, if you don’t count the springs, that pivoting joint where the two non-axle-sides of the triangle meet is the only place where each suspension attaches to the frame. For the front suspension, this pivot point is a ball and socket, and is located under the oil pan right in front of the transmission:

In the rear, that pivoting point is a spherical housing surrounding the transmission output U-joint.

The stick axles on each suspension are held in place by transverse (i.e. going from right to left) leaf springs that are bolted to the frame and held to each axle with a small shackles at each end:

To help understand how this works, I’ve built a computer model of the rear suspension so we see how it moves up and down and rolls.

Notice how the whole suspension pivots around the ball and socket which is located at the rear of the transmission. This is the only connection to the car. Everything else is controlled by the two shackles linking the axle to the spring (not shown).

Connection to The Car

As with any suspension, how it connects to the rest of the car is critical in the way it functions. As we saw before, in the Model T, this is accomplished with a single attachment in the front and the rear. To give you an idea, here’s a look at a “1940 Ford Axle Set” for sale in eBay, a suspension that’s basically the same as the Model T’s. Here’s the whole front suspension:

And here’s the whole rear suspension:

If you prefer patent drawings, here’s the rear again:

The front attachment is a fairly straightforward ball and socket system with the ball being part of the suspension arms (the two rods) and the socket being a two-piece assembly connected to the bottom of the oilpan. The two pieces are clamped together with a set of springs to keep tension on the ball and take up wear as the car ages (as you can imagine, this ball and socket has lots of grease in it):

Here is what that cap looks like from an early Ford illustration:

And here is what the end of the front suspension arm looks like:

Image via Jalopy Journal

In the rear, however, we have the added complication that not only does the attachment need to connect the suspension to the car, it also has to allow power to pass through to the wheels. It can’t be a simple ball and socket like up front.

The Rear Driveshaft Is In A Rigid Tube

Since the rear suspension has to power the wheels, it needs to include a driveshaft between the engine/transmission and the differential on the rear axle (the back side of the triangle). In the Model T, this driveshaft is housed inside a tube, called a pinion drive shaft housing, which is rigidly connected to the axle:

The rigid connection between the shaft housing and the axle means that i,  along with the driveshaft inside the housing, move up and down with the suspension. This means we need to provide some means for the driveshaft to move relative to the transmission. The way this is done on the Model T is with a universal joint inside the ball socket:

This allows the suspension to move up and down and roll while still allowing power to pass to the wheels through the pivot point. Of course, this means the pivot is much larger than the one for the front suspension, but it is a small price to pay to keep such a simple suspension design.

The Steering Gear Was Built Right Into The Top Of The Steering Column

The steering system of the Model T is another area where simplicity ruled the day. Most cars then and now have some sort of a steering box or steering gear, whether it is a rack and pinion or a ball/nut type, but the Model T did not. Instead, what it had was a planetary gear set housed inside a brass canister at the top of the steering column right below the steering wheel:

Inside this canister is a small planetary gearset that provides the gear reduction normally found in a steering box located at the bottom of the steering column:

Image via: Technical – Model T steering question | The H.A.M.B. (jalopyjournal.com)

At the bottom of the steering column is a simple pitman arm (which turns the rotation of the steering shaft into a swinging arc), which is connected to a drag link, which pushes and pulls the right-side suspension knuckle that steers the wheels. A tie rod then connects the right-side knuckle to the left so that when one wheel turns, so does the other.

Let’s see how this system works:

If we open up the steering box, we can see how the planetary gear set works:

Looking at the system from underneath, we can easily see how the motion of the pitman arm is translated into steering of the left and right wheels:

via GIPHY

Since the Model T came out, car suspensions have gotten increasingly more complex, and we will be taking a look at some of the most consequential and influential throughout this series. But, sometimes it is refreshing to go back and look at how it all started and how simple things used to be.

Simple, but effective. The Model T put America, and perhaps the entire world, on wheels. It was durable, easy to repair, and could go almost anywhere.