DMac's F1000 Build

Have you guys read Tony Pashley's book "How to Build Motorcycle-engined Racing Cars"?

http://www.amazon.com/Build-Motorcyc...5010971&sr=8-1

It offers a general approach to designing and building an FB-type car, rather than an overly technical engineering analysis.

The guy had made several bike-powered cars including one made with an alu honeycomb monocoque so he has a lot of practical experience.

I must say it is way over my capabilities, as running and learning how to drive my Stohr F1000 is about all I can handle, but the book helped me understand and appreciate some of the parameters involved in making an FB car.

Ivin

I will add a few items to consider along with what Gary posted.

1. Have the inboard rod ends aligned with the thrust loads. To make the brackets simple you can use the rod ends with a vertical or horizontal bolt.

2. I cheat and use rodends for the top ball joint but I also use shims to adjust camber without changing toe settings. This allows me to accommodate radial and bias ply tires as well as change KPI.

3. I gave up trying to have the lower ball joint in double shear. I use 5/8 spherical bearings for the lower ball joints. This has proven to give very good service. You can use a 7/16 or 1/2 inch stud with bearing inserts.

Your next step will be to figure out what you want for suspension and steering geometry.

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Originally Posted by S Lathrop

I will add a few items to consider along with what Gary posted.

1. Have the inboard rod ends aligned with the thrust loads. To make the brackets simple you can use the rod ends with a vertical or horizontal bolt.

2. I cheat and use rodends for the top ball joint but I also use shims to adjust camber without changing toe settings. This allows me to accommodate radial and bias ply tires as well as change KPI.

3. I gave up trying to have the lower ball joint in double shear. I use 5/8 spherical bearings for the lower ball joints. This has proven to give very good service. You can use a 7/16 or 1/2 inch stud with bearing inserts.

Your next step will be to figure out what you want for suspension and steering geometry.

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Currently, I am using parallel a-arms for this first few iterations and will move on from there as I perfect the geometry.

I have put thought into how to adjust the rod ends without changing toe. If you change the length on both the upper and lower control arms (to change camber) around the axis that the steering is on, the toe should not change. See low quality illustration. Is this reasonable?

On a side note, I own Tony Pashley's book. It has been a good resource, but it is less technical than I expected.

Interesting thought on camber adjustment. But you now run the risk of changing the motion ratio as you adjust camber.

You also need to consider the time that it takes to make any adjustment. Being able to change 4 springs and adjust ride height in less than 4 minutes will give a big competitive advantage on a race weekend.

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Originally Posted by S Lathrop

Interesting thought on camber adjustment. But you now run the risk of changing the motion ratio as you adjust camber.

You also need to consider the time that it takes to make any adjustment. Being able to change 4 springs and adjust ride height in less than 4 minutes will give a big competitive advantage on a race weekend.

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That is one thing that I have learned so far: there are always trade-offs in design. It certain is a big challenge to design independent adjustability of the alignment (camber, castor, motion ratio...) into the suspension.

Ease of use can be lost when designing digitally. For example, I can change the camber in a few clicks. Less easy IRL.

as you have shown, changing top and bottom arm lengths will not change the toe, but it will totaly screw up your bump steer. i believe that toe is easy to adjust at the track, but bump steer is a lot more work. my .02.

john f

I know this is an older thread, but it applies to a thought I had lingering in my brain from another thread... (sorry for hijacking)

Before I ask, please note that I am a former stock car team guy (non-professional) looking to get into open wheels...

My question is this... In a car that has fully independent suspension, particularly in the rear, is there a way to overcome/eliminate/minimize the effects of adding positive camber as the suspension travels? Or do you just compensate with the static camber setting? (This is how we always did it with "stock" cars, because our hands were tied and we couldn't really try to re-invent anything) Not sure if it is possible to eliminate this effect. Please enlighten me!

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Originally Posted by coletrickle

My question is this... In a car that has fully independent suspension, particularly in the rear, is there a way to overcome/eliminate/minimize the effects of adding positive camber as the suspension travels? Or do you just compensate with the static camber setting? (This is how we always did it with "stock" cars, because our hands were tied and we couldn't really try to re-invent anything) Not sure if it is possible to eliminate this effect. Please enlighten me!

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You can make the camber curve (camber angle vs suspension travel) change based on your particular suspension geometry (it's a simple 4 bar linkage in 2D, more complicated in 3D when you throw in the toe/steering link). There are two typical camber curves that people look at, deg/g which is camber change in chassis roll (ie cornering), and deg per distance of suspension travel (bump). If you "optimize" one, you typically screw up the other. It ends up being a compromise between the two.

The other big thing to look at is minimizing compliance in the suspension. You want the suspension travel to come from the shocks, not from flexing in the various components and brackets that make up the suspension system.

Awesome reply, thanks. That explains it quite well.

It is pretty easy, at least in my opinion, to create a geometry with small comprimise between ride camber(straight up and down) and camber compensation (in roll).
Just look at where your instant center moves during roll and you'll start to notice a trend.
But then you have to look out for kinematic roll center migration.

Wright is right...Wright is correct :rolleyes: ...a compromise indeed. The decision is easier if you know what your tire wants...

Ill add some advice for the OP...

Regarding your kinematics/moving in Solidworks, its really easy if your suspension is derived from a sketch instead of parts. That way you can visualize the motion without worrying about mates. Then when your kinematics are finalized, flesh-out the components and check clearances.

or you could fork out the dough for a kinematics program like WinGeo or OptimumK. Get in touch with either local A-mod guys or an FSAE team if your uni doesnt have one and get some advice.

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Originally Posted by rmstringham

Ill add some advice for the OP...

Regarding your kinematics/moving in Solidworks, its really easy if your suspension is derived from a sketch instead of parts. That way you can visualize the motion without worrying about mates. Then when your kinematics are finalized, flesh-out the components and check clearances.

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SolidWorks has this concept called blocks that makes linkage design easy. You take a sketch, that can be as simple as a line, and click tools>blocks>make. You would do this again for each control arm and the upright, then define mates between the appropriate points. When you're done, you can just click and drag a point on the suspension to watch it work. Click Help>SolidWorks Tutorial>Special Types of Models>Blocks for a better explanation.

Coming soon on my agenda is to get this to show me the instant centers and the roll center.

-Jim

Last week, I sketched up a concept for the bodywork. Here is the silhouette of the body inserted into my suspension design file. More updates to come in the next week or so.

Jim...thanks for the SW tip, if you get it to tell you roll and instance center would you mind sharing that with us SW users?

David....profile looks great! Keep the progress moving. If you need any machining done let me know. I also have a knowledge base of UPRIGHT and UPRIGHT INTERNALS going all the way back to the original Swfit D1. The upright internals I used came from my past work on the DB6 so I used all DB6 internals....I also have all the drawings for several iterations of VD upright internals going back a few decades to present.

Also if you need 3 pc. wheels we soon will be offering them for sale. We will have a special deal on first orders.

Regards
Gary @ Edge Engineering Inc.
SoCal CNC

If I were doing a clean sheet F1000 design I cannot imagine wanting to do an overhead air intake. Other than presenting a lot more frontal area and keeping air off of the rear wing, what advantage does it give you?

The stock airboxes on these cars are begging for a better solution. I think Jeremy hill and schweitz are much closer than everyone else.

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Originally Posted by Wren

If I were doing a clean sheet F1000 design I cannot imagine wanting to do an overhead air intake. Other than presenting a lot more frontal area and keeping air off of the rear wing, what advantage does it give you?

The stock airboxes on these cars are begging for a better solution. I think Jeremy hill and schweitz are much closer than everyone else.

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I completely agree. I think the benefit of reduced frontal area and clean air to the wings far outweigh any benefit of slightly cooler and slightly higher air pressure to the engine. It wouldn't take too much to chech with an existing car either, just a different engine cover and some track time could tell which direction to pursue.

We have tested both, and I like the ram air box.

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Originally Posted by DMac

Accepted. I will be using Fluent for my CFD analysis.

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Whether you are a CFD expert or not, push the guys running your analysis to justify the way they've done it, particularly meshing. The use of expensive software or hardware does not automatically lead to its proper use, and even getting experienced people isn't enough. They may have 10 years of CFD experience simply doing it the wrong way! The big boys routinely publish poorly done CFD. IMO there are a very select few who really know how to do it properly. On top of that they NEED to understand formula car aero as the meshing MUST be tailored to the specific Formula car phenomena that are important and difficult to capture. What is important to an aircraft or a road car can be meaningless to a formula car!!

A basic design simply drawn up by a good aerodynamicist based on aero principles can be less risky than a design that's "optimized" (hate that word!!) with mediocre CFD. If you've found a good formula car aerodynamicist who does proper CFD you're in luck and the aero aspect of the car will be excellent.

I'm not trying to scare or discourage you. In fact I'm actually happy to see someone making the effort; just giving some unsolicited advice from a CFD n00b ;) Hopefully it will help make the CFD of more use to you.

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Originally Posted by Wren

Other than presenting a lot more frontal area and keeping air off of the rear wing, what advantage does it give you?

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Be careful with statements like those; aero works in very mysterious ways, and things aren't always as bad or straightforward as they seem :o