Angles for Automotive Design - Guidelines
 

SAE practices
https://www.researchgate.net/figure/...fig1_255700982
http://forums.pelicanparts.com/uploa...1613165083.jpg

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

angles
 

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 )

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

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.

3.9 out of 30? First approximation strikes again. :)

Remember People are differing heights
 

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.

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.

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
https://ecomodder.com/forum/attachme...5&d=1613408337
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.

SAE angles
 

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.:)

Anyone know why supercars always have hydraulic nose lifts for speed bumps? But air suspension is all that is available for consumers to fit to their own cars?

The illustration doesn't support the claim. The door cut-lines and steering wheel align. The wheelbase has been extended. Only the base of the windshield moved forward.

I can't find a reference but IIRC the Chrysler Airflow was the original cab forward design. The rear seat moved forward so you weren't sitting on top of the rear axle.

I can't find the source, but doing one of the more recient Chrysler minivan redesigns they built a full adjustable "cabin" for the front seats. They could move everything around and then brought in 100s of regular drivers to position it where they thought it was most comfortable to both drive and ingress/egress. Supposedly the average was within a few centimeters of the original 1984 van. So either that's what people got used to, or they just nailed it in 1984.

Airflow axle
 

I believe they also moved the engine over the front axle as well, as part of the 'Boulevard Ride.'

My Dasher/Audi 80 scoffs at engine over axle. :)

Interesting, never heard that before.

I did find this.

What could have been: Chrysler originally intended the LH platform as front-, rear-, and all-wheel drive
https://www.hemmings.com/stories/202...ll-wheel-drive
https://img.hmn.com/stories/2020/05/...S993_008DG.jpg

SAE eyellipse and sightlines
 

My Handbook's section on driver vision was from 1985 and under revision as of 1986 publication.
All they provided was the side elevation and plan-view eyellipse centroids from the human factors statistical values. Class-A & B vehicles.
With seat-slide, torso, and neck articulation range of motion, those centroids were supposed to give the designer enough data from which to create viable, critical sightlines to all targets.
No additional insights.:(

Okay, now I'm a little miffed.

I've done my redesign with the suggested angles in mind and preserved much of the look of my design, but it's started to look conventional as it follows conventional guidelines.

Then today I see this vehicle that completely breaks these guidelines, and looks gloriously cab-forward but also dangerous.

I say dangerous because I once saw an old lady flip her Pontiac Trans-Van upside down after running into a medium separating on coming traffic. She took the turn too wide and too fast and hit the barrier, and I am convinced this was a result of the unusual distance of driver's head to windshield - giving the vehicle a driving from the rear seat feeling.

Here is the vehicle in question.

Canoo Opens Waitlist for World’s First Membership-Only Vehicle
https://www.press.canoo.com/press-re...p-only-vehicle
http://forums.pelicanparts.com/uploa...1615501409.jpg


https://techcrunch.com/2019/09/24/ca...ctric-vehicle/
http://forums.pelicanparts.com/uploa...1615501409.jpg

https://observer.com/2020/08/electri...e-merger-spac/
http://forums.pelicanparts.com/uploa...1615501526.jpg

Did they get around the 26-27 degree upper cone of vision rule because they made the roof transparent?

Did they not worry about the driving from the rear seat feeling and possible driver disorientation because it's most likely to be self-driving autonomous?

I like where I've taken my own design and think it's the better for it with the small changes I've made.

However when these "tech" companies say they want a vehicle that looks like it's been designed by a cell phone or watch company and not a car company, just what are the consequences?

Will the result be so impracticable as to be not allowed on public roads?

Did they simply just fired anyone who rocked the boat and said; hey wait a minute that isn't going to work because the driver has to be able to see traffic lights change colors?

What do you guys think?

Somebody else's problem, ignore the idiocy?

Mind you I might be more forgiving if the roof line at least tapered a little for aerodynamics.

Don't get me started on the leg room and operation of floor pedals, not going to matter as I don't think they put a suspension in it, just too car-like.

To quote the Beatles "We'd all love to see the plan."

Did you talk to the old lady? Was she even looking outside the car?

The problem with the distance to screen is the ever-widening A-pillar as they recede. Kanoo solve it with their transparent A-pillar.

I had actual eye contact with her as it unfolded.

She was making a right hand turn onto Orchard Lake Road, I was in the long line of cars waiting for the light to change and in the left lane, two lanes of traffic each side of the road.

If the concrete curb barrier wasn't there she would have T-boned one of the cars in the line but at an angle, about two cars up from me contact was made.

The look on her face was;

1. I gotta get there yesterday

2. Oh shat I'm going fast......... where am I?

3. I didn't just hit the curb, what was that?

4. How come the van is on two wheels?

5. I cannot be at 45 degrees..........no way in heck

6. How come I'm upside down sliding down the road?

All in a matter of seconds, like a movie in slow motion, I still remember it 35 years later.

.................................................. .............


One of the intimate driver to car relationships in my old Porsche 911 is that one can reach out and touch most of the windshield, it's closer than most to the driver's eyes/head.

People talk about getting in the car, buckling in, putting their hands on the steering wheel and feeling the cockpit enclose upon them, and becoming one with the machine.

It's like one of those far-field and near-field zoom movie lenses in action.

Counter to this is a nightmare I once had of attempting to drive a car from the back seat, I'm pretty sure that I was naked too. :D

Well, I have two flat-screen Beetles. I suspect the problem with the Transit/Previa layout is either refraction/distortion in the glass, or driver position relative to the front axle.

What's the big deal with urban stoplight visibility? Everywhere I've been there's a light over the crosswalk attached to the standard holding the overheads.

So about the Canoo and it's quarter windows (and sight-lines), JACG posted this today:

https://1.bp.blogspot.com/-4Psk2r7LX...bfa89-t7hZ.jpg
justacarguy.blogspot.com/2021/03/sold-for-103000.html

There's also this:

A Full-Size Pickup With Compact Dimensions?


It has an interesting expanding pickup bed (half-way to a retractable boat tail). And at t=381 there is a frunk that opens into a workbench with four 110V outlets.

The operator is basically standing upright tugboat style and leaning back on a stool from what I can tell. This drafting board position isn't good on the lower back long term, and forget about passive restraints/seat-belts.

However that said, a nice alternate to VW Transporter van seating and Cab Over Engine (COE) layouts.

I think the post below was partly in response to the Canoo I posted in another forum.

Random TRANSPORTATION pictures - Page 2454 - Pelican Parts Forums
The rear bench layout is eerily similar.

In suburban areas where country meets city, a redundancy of stops lights at multiple heights is often omitted (no sidewalks or cross walks).

FYI: click the link to see more photos, explanation found in Post #49164

Random TRANSPORTATION pictures - Page 2459 - Pelican Parts Forums
http://uploads.bmxmuseum.com/user-im...605f3744a8.jpg

http://uploads.bmxmuseum.com/user-im...605f374522.jpg

Post #49164