Objective
Research how a double wishbone suspension does it’s thing and how it can attach to frame
How would susp hardpoints change if we’re looking into external susp instead of internal?
How do we make the front of chassis around those hardpoints?
Considerations
Figure out how a double wishbone suspension works
Find out what makes up a suspension
bell crank tab, shock mounting tab, toe-rod, etc.
Look into “multilevel” frame arc - see notes over suspension conversation from today.
Design considerations for frame to accommodate front suspension geometry
Look at the old susp design, and what we could change about that so the new sys is the best it could be.
What loads are gonna be at these hardpoints, and how do we create geometry (cross brace) to counteract?
By the end of 10/19/2024, have the following done:
Project goals
Background research
Notes from discussion with suspension
Any design criteria and other considerations
Any sources used
Any visuals used
Double Wishbone Suspension - How does it work?
To first understand DWS, it’s important to understand camber.
What’s camber?
Angle of tire regarding vertical of car.
Positive - top leans out, bottom leans in.
Negative - Top leans in, bottom leans out.
In racing, negative to no camber is used.
For a wider stance and greater stability
Moving onto double wishbone
Utilizes two V-shaped “wishbones” which connect to the frame at the holes. Upright attaches to the wheel.
These are cool because they allow each suspension to act independently - if there is a bump on the road that affected only the front right wheel, it’s suspension system is the only one that would react. (Race Car Design by Derek Seward - 3.1: Introduction to Racing Car Suspensions)
The Bell Crank
Push Rod, Bell Crank, Shock
A push rod “pushes” so that the bell crank can transfer motion to the shock. (pull rods also exist)
A bell crank pretty much acts as a motion-transferring intermediary b/w shock and push rod.
Shocks make sure spring don’t compress/extend excessively, also springs do suspension essential func.
Multilevel Frame Architecture
Note how new front frame is hexagonal rather than rectangular.
Suspension wants their wishbones as close together as possible, but frame can’t get smaller b/c pedal box is fixed.
So, this new hexagonal system is great.
3 Hardpoints, more freedom.
This seems like a great system (it is) but one thing to consider is how would we cross-brace this?
I’m thinking it’ll be a lot of FEA (does an X shape work okay?)
Important note: External vs Internal suspension system hardpoints are the EXACT same.
10/26/2024 Meeting W/Suspension
Transcription so you can read:
Objectives:
Understand Bell Cranks
Hex vs Rect multilevel frame arc
Improve current front frame design
You don’t want a large mounting distance, one problem w/this is huge upright.
One problem w/Daybreak - pedal box
Ergo unhappy (small space)
Suspension unhappy (ctrl arms far apart)
Frame unhappy (prob bad load handling)
Overall, loss-loss-loss situation
Hexagon frame is better cuz smaller top control arm (facilitates negative camber for cornering)
Note: Recommendation for dY b/w ctrl arms is 9 in, sus currently tryna do 8 in.
Below are diagrams, ignore everything except for the bottom left hexagon. It’s a diagram of how suspension would look like on the front frame.
Taking a look at the Old Suspension and Frame Systems
Observations (suspension)
The wishbones are a lot smaller than i expected.
How does the shock/dampener/spring thing connect to the frame?
Is there an assembly of the suspension and frame together?
Observations (frame)
Should we use a diagonal pipe at the front? I notice some FSAE teams use that. What’re the pros and cons of each?
There is a TON of pipes.
Why are “X” shaped crosses used in some places, K shaped ones in other ones, and regular triangles in the rest?
Because you need different load paths for different types of load. Understand that X shape, single diagonal, K shape, they all have differing complexities of welding. Also, more pipes means more weight. Must consider ALL of this when designing a frame.