Suspension questions for ground up custom

[Powellbr]

I'm looking to build a two seat mid engine custom car and was wondering if anyone has an idea as to where I could learn more about the pushrod suspension concept. A big question I have is if it's possible to design a set up that eliminates the sway bar but still has very little body roll? My first idea would be to simply put the coilovers on a cantilever and have a rocker at the middle of the car that the inboard mount of the shocks mount to, so that when one side goes up it pushes the other down, and keeps the car planted. Am I off base and that's not how it'd work? This car is going to be run mainly in Drag and Drive events, closed course road races such as Silver State Classic Challenge, and top speed events, although that's not a firm limit as to what will be done with it. Sorry if this isn't the appropriate place for this thread, I'm new to this forum

Sent from my T773O using Tapatalk

[TimH]

I may be wrong but I think you're describing a pretty standard approach for formula cars and sports racers these days. Take a look at photos of suspensions to be found throughout this website (especially in the For Sale forums) and elsewhere - the only question in front is whether to use one or two shocks.

[Powellbr]

I may be wrong but I think you're describing a pretty standard approach for formula cars and sports racers these days. Take a look at photos of suspensions to be found throughout this website (especially in the For Sale forums) and elsewhere - the only question in front is whether to use one or two shocks.

Will do when I have some free time. What would be the reasoning behind using one shock up front? Easier tuning? Lighter weight? I'm thinking since the class I'd be competing in at Rocky Mountain Race Week has a minimum weight of 3,000 pounds I'd go with two shocks

Sent from my T773O using Tapatalk

[S Lathrop]

You might look at the cars that were built with a mono shock front suspension. Dallara used this setup on their first version of the Indy Lights cars.

Decades ago I saw a SAE Formula Car that had a totally unique front suspension setup that combined a leaf spring and a mono shock setup. I saw the car at the Indy Lights race at Three Rivers in Canada. That was close to 20 or more years ago.

I was able to get good performance from the Dallara system but that took a lot of work and might not have been legal if it had been protested.

I have raced setups in Indy Lights when I did not like the spec sway bar. The car was very fast. But my driver was able to adapt to the demands of the car. The setup did not have sway bars at either end.

[Vulnavia]

Depending on how well you want the car to handle. There are many books out there. You can learn a lot on the internet. I started with Race car vehicle dynamics by William F. Milliken and Douglas L. Milliken. (hope you are good at math).
Carroll Smiths series of books too. Or some of the CAD software out there, you can work through motion ratios and everything else that it takes for the suspension to work properly.
Anti-roll bars are important to the overall handling. Don't remember seeing a "modern" race car without them.
I think what you describe would be very difficult to drive. (Like a car with unbalanced front tires)
I learned about design/build by reading ( there are a few builders on here that are a wealth of knowledge ) and asking a lot of questions, and a lot of redoing what didn't work well. Worked/crewed on a few different types of race cars. I have no formal education in the design of anything, I really like building stuff, maybe as much as racing it.
Take your time, build it safe and good luck.

Will

[Powellbr]

Depending on how well you want the car to handle. There are many books out there. You can learn a lot on the internet. I started with Race car vehicle dynamics by William F. Milliken and Douglas L. Milliken. (hope you are good at math).
Carroll Smiths series of books too. Or some of the CAD software out there, you can work through motion ratios and everything else that it takes for the suspension to work properly.
Anti-roll bars are important to the overall handling. Don't remember seeing a "modern" race car without them.
I think what you describe would be very difficult to drive. (Like a car with unbalanced front tires)
I learned about design/build by reading ( there are a few builders on here that are a wealth of knowledge ) and asking a lot of questions, and a lot of redoing what didn't work well. Worked/crewed on a few different types of race cars. I have no formal education in the design of anything, I really like building stuff, maybe as much as racing it.
Take your time, build it safe and good luck.

Will

I haven't set any changes in stone right now, currently it's a traditional pushrod setup with a 43" wide, 1.25" diameter sway bar with a 0.25" tube wall and 48 spline arms front and rear. Coilovers are going to be a pair of 4" travel and 5" travel in front with quick ride height adjust because of a hydraulic cylinder built into the top mount

Sent from my T773O using Tapatalk

[Fred Michael]

Take a look at Stohr cars. No front ARB

[tlracer]

Monoshock setups don't have a 'conventional' ARB but they do have an amount of compliance built in, usually using belville washer stacks on the rocker pivot.

These allow for some upward movement of one wheel before the linkage goes 'solid' and moves the opposite wheel.

By varying the number, thickness and orientation of the belville washers, the roll stiffness can be adjusted.

[S Lathrop]

Powellbr ,

How are your skills with drawing programs like Solid Works? Especially 3D drawing.

I started doing race car design work in the early 1970's when it was all done on paper. It was not until the mid 1980's that we were able to model our suspension systems in 3D and what a brake through that was.

I have used Bill Mitchell's WinGeo software as a design tool and especially when my cars got to bell crank and push rod suspension systems..

I actually do a lot of drawing with AutoCad in 3D mode, as well as Solid Works. Old habits I think. One thing that is very important is how the motion ratio between the shock and the wheel change with changes in ride height. It is not a constant, and that can work for you or against you.

[problemchild]

if i was undertaking the major task of building a custom car, within a timeline that would see me at specific events, I would copy a known suspension design and get the car complete. Once successful at the initial task, then I would look at mods and updates.

FWIW, I don't know why you would want to eliminate ARBs from a generic car design. At some point in development, you can eliminate them with super high-rate springs and rounds of preload, or other roll stiffness tools, but they sure are an easy way to balance a new car.

[Powellbr]

Powellbr ,

How are your skills with drawing programs like Solid Works? Especially 3D drawing.

I started doing race car design work in the early 1970's when it was all done on paper. It was not until the mid 1980's that we were able to model our suspension systems in 3D and what a brake through that was.

I have used Bill Mitchell's WinGeo software as a design tool and especially when my cars got to bell crank and push rod suspension systems..

I actually do a lot of drawing with AutoCad in 3D mode, as well as Solid Works. Old habits I think. One thing that is very important is how the motion ratio between the shock and the wheel change with changes in ride height. It is not a constant, and that can work for you or against you.

I don't have any experience with computer Sim tech because all I have right now is a smart phone, I've mainly been working on the BOM for this car because I can imagine how much of a PIATA hand drawn design can be. That being said, I do have an idea of what I want the car to look like, and an idea of where and how things will be ducted. For example, in the front I'm going be using a composite air dam, more than likely dry carbon fiber, to direct the air from the grill to the auxiliary radiators for the intercooler and drivetrain heat exchanger. In the rear I'm thinking I'm going to have the air filter boxes mounted on the sides of the engine bay such that air is forced into them when going down the track, I'm gonna have a scoop up top that forces air down into the engine bay and out the rear to help keep underhood temps down so as to help keep fluids from picking up ambient heat, and as such forcing the heat exchangers and radiators to work harder or to stabilize at a higher temp. The chassis and suspension design is gonna be done when I get a powerful laptop or a decent desktop computer

Sent from my T773O using Tapatalk

[Powellbr]

if i was undertaking the major task of building a custom car, within a timeline that would see me at specific events, I would copy a known suspension design and get the car complete. Once successful at the initial task, then I would look at mods and updates.

FWIW, I don't know why you would want to eliminate ARBs from a generic car design. At some point in development, you can eliminate them with super high-rate springs and rounds of preload, or other roll stiffness tools, but they sure are an easy way to balance a new car.

I'm not aiming to be at specific events like Rocky Mountain Race Week this year or next, it's something I'm wanting to compete in once it's done. Once I'm able to build this I'm dedicating as much time as I can to get this built, with the chassis fab being done by a professional shop since, while I have confidence in my abilities, I don't want to run the risk of a weld I made breaking when I deploy the chutes at the shutdown section of a drag strip, I don't wanna end up in the sand pits

Sent from my T773O using Tapatalk

[Powellbr]

if i was undertaking the major task of building a custom car, within a timeline that would see me at specific events, I would copy a known suspension design and get the car complete. Once successful at the initial task, then I would look at mods and updates.

FWIW, I don't know why you would want to eliminate ARBs from a generic car design. At some point in development, you can eliminate them with super high-rate springs and rounds of preload, or other roll stiffness tools, but they sure are an easy way to balance a new car.

Eliminating the ARBs aren't something I'm seriously considering, it's something I mentioned in passing

Sent from my T773O using Tapatalk

[S Lathrop]

I am going to suggest that you go to the next SCCA (Sports Car Club of America) race in you area and take a close look at the P2, and other sports car classes racing there. You may find something that will help you turn you dreaming into something that you can actually build.

The S2 class, Sports 2000 cars, may be a good jumping off point. As suggested previously, start with an existing car and turn it into what you want. I can guarantee you that buying something and modifying that package will be a fraction of the cost of starting from scratch.

[TimH]

I am going to suggest that you go to the next SCCA (Sports Car Club of America) race in you area and take a close look at the P2, and other sports car classes racing there. You may find something that will help you turn you dreaming into something that you can actually build.

The S2 class, Sports 2000 cars, may be a good jumping off point. As suggested previously, start with an existing car and turn it into what you want. I can guarantee you that buying something and modifying that package will be a fraction of the cost of starting from scratch.

Excellent advice from somebody who's not just been there, but done that and a whole lot more.

NASA and SVRA will also have a selection of sports racers to examine.

[DaveW]

...I can guarantee you that buying something and modifying that package will be a fraction of the cost of starting from scratch.

I don't want to be a wet blanket, but...

Steve is absolutely right. Designing and building a racecar from scratch is a black hole for time and $. And because of that, I'd bet that >75% of those projects never reach completion.

There are a LOT of good used racecars available for pennies on the dollar of their original cost. And modifying one of those would still give you most of the satisfaction w/o many of the headaches of doing it from scratch.

If I were trying to do what you say you want, I would start there.

[Vulnavia]

I have looked at some different Stohr race cars at the track, but did not notice the absence of arb's on the cars ( an FF and P1 ) I thought they were needed to help adjust the cars handling, especially as the race track changes. If you have some pictures or drawings I would really like to see them and learn how to do with out them. Or I could wait till the start of the season, 4-5 months.

Thanks,

Will

[TimH]

Here's a start. Obviously not as helpful as a 3-D up-close look, but a start:

https://www.apexspeed.com/forums/sho...ionship-Winner

https://www.apexspeed.com/forums/sho...6-Sports-Racer

https://www.apexspeed.com/forums/sho...1998-KokoPelli

https://www.apexspeed.com/forums/sho...3231-Stohr-WF1

[tlracer]

I would agree completely with DaveW and Steve Lathrop on this - start with the basics already done. Otherwise you will spend time, money and energy on stuff like driver position and engine location before you can even consider the 'interesting' bits like suspension, aero, etc.

Indeed, for maximum creative input vs. minimum dull stuff, you might want to go further than these two eminent guys have suggested - buy an incomplete car, maybe one of those parted-out 'chassis + stuff' offers and go from there. That gets you the basics in place without the need to design, analyse and build. Yes, it will come with certain restraints but those can be offset against the ability to look at some one else's design and try to understand why/how they did stuff like it is.

Don't go down the route of thinking CAD is the only path - for real understanding of this 'why/how' element, a drawing board and paper or something simple like 'Paint' is remarkably good!

Having to physically lay out suspension pivots from an existing chassis, then figure the best way to connect those to the wheels, analyse geometry changes is a great learning exercise. The same goes for 'reverse engineering' and 'fast prototyping' too...they're just phrases that don't need oodles of CAD processing power, just a human brain and some simple tools:

Reverse engineering - take it apart, figure why/how and then look at if it can be improved

Rapid prototyping - so you want a front crashbox, say? Look at where it can be mounted, what it's got to avoid and how it needs to fit with other components. Draw it up, make a cardboard version and check it out! That way you don't have to spend hours poring over a CAD screen, shuffling things about - all you need is the Mk1 eyeball, a ruler, a sharp knife and some adhesive tape

And, after all that, if you get stuck - ask on here! Apexspeed is a mine of valuable information from guys who have been there, done it and are almost always happy to pass on that experience.