Angles for Automotive Design - Guidelines

[kach22i]

SAE practices
https://www.researchgate.net/figure/...fig1_255700982


I know it's out there, but I cannot find it right now.

What are the recommend upvision and downvision angles (see image above)?

Aerohead has listed vehicle approach and departure angles along with the inside angles between the front and rear wheels - see below (forgive me if I wrote them down wrong).

Front: 10 degrees min.

Rear: 16 degrees min.

In-between wheelbase: 10 degrees min.

I'm doing a few sketches and the upvision angle (so driver can see traffic signals) seems a bit low on my design. Just want to check with some standards.

H124 in this link:
https://law.resource.org/pub/us/cfr/...1100.2001.html

The math on this PDF is daunting.
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAD

Nice PDF paper on ergonomics:
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAV

[aerohead]

Originally Posted by kach22i

SAE practices
https://www.researchgate.net/figure/...fig1_255700982


I know it's out there, but I cannot find it right now.

What are the recommend upvision and downvision angles (see image above)?

Aerohead has listed vehicle approach and departure angles along with the inside angles between the front and rear wheels - see below (forgive me if I wrote them down wrong).

Front: 10 degrees min.

Rear: 16 degrees min.

In-between wheelbase: 10 degrees min.

I'm doing a few sketches and the upvision angle (so driver can see traffic signals) seems a bit low on my design. Just want to check with some standards.

H124 in this link:
https://law.resource.org/pub/us/cfr/...1100.2001.html

The math on this PDF is daunting.
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAD

Nice PDF paper on ergonomics:
https://www.google.com/url?sa=i&url=...AAAAAdAAAAABAV

The SAE Handbook probably has the vision material. I'll look.
I think the approach, break-over, and departure angles are 16,10,10,and 10. I'll check.
The 'daunting' stuff is statistics. You might rearrange all the symbols and definitions.
Root Mean Square Error would be figured, then plugged in.
Go slow. Watch the brackets ( parentheses )

[freebeard]

Off by one minute!

As a first approximation, measure the angle off the drawing. Estimating by eye-ball, it's ~30 degrees. Tell me how I did.

It's not like nobody's had the problem before: duckduckgo.com/?q=traffic+light+prism

[Gasoline Fumes]

[kach22i]

I love it, thank you gentlemen.

My trusty green 30/60 triangle that I've had for +40 years will come in handy once again.

I've got several adjustable triangles as well, and the drawing is in AutoCad already for when I have to get precise.

[freebeard]

3.9 out of 30? First approximation strikes again.

[AeroMcAeroFace]

If you are designing a car, remember that people are different heights and some people like/need to be more reclined than others. The worst cars are the ones where the roof line is so low that you need to recline the seat just to fit. And then you are even further back, talking from experience from when I drove a Triumph Spitfire.

The opposite is true though sometimes you may not be able to see the hood at all due to sitting further back and lower down to get around the dashboard and wheel. Some cars are terrible for both taller and shorter people and some are good for both.

[freebeard]

In the SAE practices picture at the center of the seat adjustment range the bull's eye is called the H-point, or hip point. That's the thing every driver [probably] has in common.

[kach22i]

I'm not posting my design yet, as it's just for fun and is a work in progress.

However, my attempts to best the old Cab-Forward rules have had some disappointments.

When I draw a Le Mans Prototype style canopy it keeps getting pushed reward because of rules of thumb for vision angles, distance of driver's head to windshield (typically too much) and foot room better than that of a 1960's VW Beetle.

Measuring from front axle to head horizontal distance looks great at 3 feet, but needs to be 4-5 feet for foot room around the front wheel wells. This pushed the driver to the center area between the wheelbase and further back than I want.

Interesting article below that supports the study diagrams that I've been doing since the 1970's when I was but a child and teaching myself.

Cab-forward Design Saved Chrysler and Reshaped Urban Cars
https://medium.com/cardesignchronicl...s-e1a5620642dc

In short, Chrysler managed to enlarge the cabin by making it move toward the car’s two other compartments, mostly the engine’s.

NOTE: My concept design has an electric motor at each wheel (inboard not hub-motor), and a rear mounted gas generator, the old center-line battery tray of former designs being replaced by a battery skateboard and or other low center of gravity and center of mass locations.

Where I'm at has gone full circle, two distinct paths.

Back to the clay car (fastback dune-buggy) I made with light blue pool noodle wheels - fits the aero-template and as posted over a decade ago in this forum.

And another path truer to the Le Mans Prototype inspiration that only fits a scaled down aero-template over the upper greenhouse teardrop canopy.

Circles within circles, I will probably put this down for a few weeks and go back the the Cab Over Engine (in look only) inspired concept that is in the spirit of the old Ford Model-T and Model-A, platforms that spawned; roadster, coupe, convertible, pickup truck and cargo van variants.

These head of a fish and body of a cheetah or bear designs are dear to my heart.

[aerohead]

My dated SAE Handbook recommended :
* 16-degree approach
* 10-degree breakover
* 10-degree departure
If you 'slide' any of these angles along the ground plane until they contact the tire face, and they strike any part of the body when loaded to SAE test weight, you run the risk of a ground strike in daily operation.
Active air suspension can easily mitigate these issues. Best of both worlds.