Angle of suspension brackets

[Ceboe]

Are you sure that's different for rotated brackets? FBD FTW

Our reasons for rotating the brackets are simpler than you may think.
As a hint for Ceboe, here are some pictures of DUT09 ('horizontal' brackets) and DUT11 (rotated brackets):

DUT09:
http://dutracing.tudelft.nl/wp-conte.../dut9_fsg3.jpg

DUT11:
http://dutracing.tudelft.nl/wp-conte...s-dut11-03.jpg
http://dutracing.tudelft.nl/wp-conte...n/img_9457.jpg (wheels are in droop here)

Thijs

The only difference I can see is a curved plane vs a straight plane

[Thijs]

The only difference I can see is a curved plane vs a straight plane

Alright then.

It's got nothing to do with anti dive, or axial loading of the rod ends, which should never occur either way, since the force should always be perfectly aligned with the rod. If there are any significant bending moments in your rods, you're doing something very wrong.

As you can see from the pictures, both setups do a fine job of keeping the angle of the rod ends close to zero despite the angle of the a-arms with the horizontal plane. This was the starting point in the design of the brackets.
The only difference is that the DUT11 brackets are smaller (lighter) and much easier to produce, their faces being perpendicular to the monocoque plane they bolt to. The DUT09 brackets angle up, and they had to be CNC'd, rather than milled by hand.

Tim, Markus, Georgy, have a second look. If you do it properly there are no unwanted force components and moments. In fact, since the bracket can be more compact, thereby moving the rod end as close as possible to the monocoque, if anything you'll be loading the bolts more evenly, and minimizing the moment arm in situations where the rod end is under a slight angle (bump, roll). But in either case, the force vector should be (close to) crossing the virtual line between the two bolts.
Rotating 90 degrees would of course introduce unwanted moments in most cases. If you want to use these simple brackets, the required angle of rotation is precisely determined: the bolt should be parallel to the intersection of the plane that is perpendicular to the rod, and the plane that the bracket bolts to.

Finally, I'd say a reason that you mostly see this on monocoque cars is that they're the only ones to use separate milled brackets, rather than welded on tabs, so the ease-of-production argument doesn't really apply for tubular frames, although there may still be marginal weight loss to be found.

[Adambomb]

Alright then.

It's got nothing to do with anti dive, or axial loading of the rod ends, which should never occur either way, since the force should always be perfectly aligned with the rod. If there are any significant bending moments in your rods, you're doing something very wrong.

As you can see from the pictures, both setups do a fine job of keeping the angle of the rod ends close to zero despite the angle of the a-arms with the horizontal plane. This was the starting point in the design of the brackets.
The only difference is that the DUT11 brackets are smaller (lighter) and much easier to produce, their faces being perpendicular to the monocoque plane they bolt to. The DUT09 brackets angle up, and they had to be CNC'd, rather than milled by hand.

Tim, Markus, Georgy, have a second look. If you do it properly there are no unwanted force components and moments. In fact, since the bracket can be more compact, thereby moving the rod end as close as possible to the monocoque, if anything you'll be loading the bolts more evenly, and minimizing the moment arm in situations where the rod end is under a slight angle (bump, roll). But in either case, the force vector should be (close to) crossing the virtual line between the two bolts.
Rotating 90 degrees would of course introduce unwanted moments in most cases. If you want to use these simple brackets, the required angle of rotation is precisely determined: the bolt should be parallel to the intersection of the plane that is perpendicular to the rod, and the plane that the bracket bolts to.

This. I like this. So many people talk about gew-gaws and trinkets when dealing with innovation in FSAE, but that's bunk. What I find brilliant about it is that you no longer hold the artificial constraint of placing them vertical or horizontal, but instead begin with a simple mounting geometry and place it so it finds a nice, cozy normal point based on kinematics and the shape of the monocoque where the inner node intersects.

Finally, I'd say a reason that you mostly see this on monocoque cars is that they're the only ones to use separate milled brackets, rather than welded on tabs, so the ease-of-production argument doesn't really apply for tubular frames, although there may still be marginal weight loss to be found.

ISU used this design for over a decade now on tubular frame cars, although the reasoning was more for a combination of ease of adjustment and structural efficiency. Although again the constraints are a bit different on a tube frame, where your anti's determine the angle of the tube connecting the nodes (hence the immediate assumption that the design shown had something to do with anti's), and the mounting points will run longitudinal to the tube (hence the now-shown-false assumption that the mountings should be horizontal). With a tube frame it's simple to get the mountings normal to the load path by simply rotating the mounting point on the tube itself, as there is no "envelope" it needs to conform to. This is a clever solution to doing the same with a monocoque.