SOLIDWORKS and the Tucker Torpedo Part 4

If you haven’t read the other Blog entries on the Torpedo please go here to get caught up on what’s happened to date:

Part One:
Part Two:
Part Three:

Blog #3 focused on the Torpedo body fabrication by Rob Ida. The following blog will focus on the chassis and drive-line and what’s been happening at Bob Cuneos’ shop.

The Holidays are over and the New Year is here and it’s the dead of winter. For me winter is the time to work on my hobby cars which is what I’m doing now with my hot rod “Violet”. Hot Rodders are always finding things to improve or change on their cars. My current project is dealing with a steering column that has too much rotational play which is very irritating when driving down a straight road. You’re constantly fiddling with the steering wheel to keep the car going straight. I’ve contacted the steering column manufacturer and we’re going back and forth to determine where the problem lies. I know I’ll be sending it back to the manufacturer in the near future and while the steering column is out of the car getting repaired it’ll give me time to improve a couple of things which have been bugging me.

Progress on the Torpedo slowed somewhat over the Holidays but is getting ramped back up. Rob Ida shifted his focus over the last couple of months to finishing up a 1940 Mercury hot rod that will be truly amazing! The Merc is a typical hot rod project that started out as one concept then blossomed into a much bigger project. A great deal of metal sculpting went into this car. I doubt there’s a piece on the body that’s not been massaged in some fashion. One of the unique features on the Merc is the front fender skirts. You typically see fender skirts on the rear wheel openings not the front, but Rob is always thinking outside the box. The front skirts are independent of the front suspension and are operated by a second steering rack driven off of the same pinion shaft which operates the steering of the front wheels. And the underside of the car is completely enclosed with a cool belly pan.

Here’s a picture of the Merc front end as of about a month ago. The very important task of block sanding the body to ensure it’s as smooth as possible is taking place now. Lots of sandpaper gets used up during this time and a get deal of dust is generated from this process. More updates to come on this project.Merc Cropped

Now back to Bob’s Shop! In blog #2 the Porsche 964 was introduced as the donor car which will be used as the starting point for the Torpedo chassis. Not all of the Porsche chassis will be used in the Torpedo- just the rear portion of it. The reason for doing this is so the engine, transmission and rear suspension can retain their stock mounting points. Thus using the rear portion of it will reduce the amount of design and engineering time required to fabricate this portion of the Torpedo chassis. The forward part of the chassis will have to be completely built from scratch and merge with the Porsche tub precisely. This chassis engineering is in Bob’s capable hands. Before we get into too many of the details a few things need definition first.

So what the heck is a chassis? A chassis is essentially the frame or underpinning of a car. It consists of a parallel set of rails with cross members in between to provide strength and rigidity. Here’s a picture of a chassis from a pickup truck.


You can see how the front and rear suspensions are mounted to the side rails. The “X” member between the side rails provides torsional rigidity in order to control how much the chassis and the body of the car twist when a bump or pot hole is hit on one side of the car and not the other. By design a car reacts to changes in road conditions by absorbing those changes through the suspension. The important component in the equation is a stiff chassis that does not flex and allows the suspension to work properly. My racing experience is coming out here.

Today’s modern cars employ the use of unibody construction for the chassis. This method of manufacturing cars started in the 1930’s with the French Citroen Traction Avant and progressed since then. Check out this 1960 ad from Chrysler which was a leader in the unibody movement in Detroit back in the day.


So, instead of a frame supporting the body, the unibody does everything a frame does and more!

2007 Ford Lincoln MKZ Unibody-3

In the 2 pictures above we see 2 different cars; a Lincoln and a Corolla in their basic unibody form. Without the rest of the parts and pieces that make up the cars they almost look the same. Looking closely we can see some similarities to the chassis of the pick-up truck shown earlier. The side frame rails are at the bottom of the door openings and also in the area where the engine and front suspension will mount. The floor pan and the roof act as the “X” member and provide torsional rigidity. The front of the unibody is designed as a crumple zone which absorbs energy during a head on crash so the passengers don’t. All this adds up to a safe, quality feeling ride. We’ll see how all this has to be considered for the Torpedo later.

On my way back from Boston recently I stopped by Bob Cuneo’s Chassis Dynamics shop in Oxford, CT to check on the progress of the Torpedo chassis. Just like Rob & Bob Ida’s shop in New Jersey, Bob Cuneo’s shop is a great place to be. Not only is there great creativity and engineering going on, but also great camaraderie. Being at Bob’s shop reminds me of when I was a 12 year old kid hanging out at Schneider’s Garage on Hudson Ave. in Rochester, NY. I would watch Paul Schneider build his 1963 Ford Falcon hot rod. To this day it would be considered a very wild street car. I still remember the blown Ford 429 engine, the straight tube front axle, the blue/green metal flake paint job, and the widest rear tires anyone had. Paul won a first place award at the annual AutoRama hot rod show in Rochester and it looked very much like the picture below.


That was my intro to hot rods and muscle cars back in 1967. Back at Bob’s shop all sorts of car guys come and go. So for me, I take it all in and feel lucky to be the fly on the wall.

Bob’s been working on the chassis for the last month and a half. The pictures below were taken a few weeks ago and Bob has continued to work on it since. There are a few challenges Bob has with the chassis. One is making it torsionally stiff or to put it another way; eliminating the amount the frame can twist longitudinally. Another is longitudinal stiffness or eliminating the amount the frame can bend. Both of those deformations in the frame would be transferred into the body and that’s not a good thing. If the body flexes, sooner or later cracks will appear in the aluminum skin. If you go back and look at the pictures of the unibody cars above you’ll see another structure inside the outer skin. This structure coupled with the outer skin provides the torsional and longitudinal stiffness for modern unibody cars. For the Torpedo those structural qualities will have to be designed into the chassis. But, the chassis can’t do it all. Other ideas to increase rigidity are being considered such as a carbon fiber inner structure to mimic the inner structure of the unibody cars. More to come on that in a later blog.

Mounting the turntable for the interior seats will pose a bit of a challenge also. The turntable will sit between the frame rails and be supported by them but it will take up a lot of the area between the frame rails. Depending on the final design for the turntable it may provide an opportunity to add cross members which will support the turntable and add stiffness to the chassis. That’s a double bonus we look for.

Torpedo Chassis

In the picture above we’re looking at the back of the chassis. You can see the original Porsche tub, the curved side rails and the pieces that will make up the support structure for the front suspension.

All the chassis parts had to be designed properly and that’s where Bob’s right-hand man comes in, Jim Gleason. Jim has been working with Bob for the last 20 years on everything from the US Olympic Night Train Bobsled, NASCAR race cars, hot rods and now the Torpedo. Jim has 30+ years of design engineering experience so he brings a lot to the table. He’s been using SOLIDWORKS for a long time now in both his day job and of course working with Bob. You can see Jim’s works here on the chassis design. Without these 3D assemblies Jim designed it would be a best guess method of building the Torpedo and we can’t do that.

Torpedo Chassis-2

In this picture we can see the turntable and how it’s positioned relative to the frame rails.

Torpedo Chassis-3

As you can see work is coming along nicely. The Torpedo chassis should be about finished by the next blog. Some of the next milestones are scanning the body so we will have an accurate representation of exactly what Rob has built. Also, it will give Andre’ Clemons a very accurate point cloud he can use to start the final class “A” surface model he’s been itching to start. This will be used to help design the inner structure for the frame and body once we get to that point. See you next blog!

Mike Sabocheck
Mike Sabocheck is a Technical Sales Director with Dassault Systemes SOLIDWORKS. Mike has been with DS SOLIDWORKS for 21 years. Prior to SOLIDWORKS he worked for Xerox for 17 years and then for Intergraph. His specialties are applying SOLIDWORKS to different design and manufacturing processes.