At what slope does a car door no longer hold itself open?

[alykabob02]

my boss has asked me to find out at what driveway slope a car/truck/SUV door will close by itself onto the person getting out of the car
of course i know that this varies depending on the make and model and the condition of the mechanical components of the vehicle’s door
but i've gotta try to make my boss happy by getting him an answer for his meeting on thursday
tnx for your help!

 

[mloew]

alykabob02,

I would start by setting up a model of the system in a spreadsheet or engineering programming language (Matlab, MatCAD, etc.). All you really need to do is construct the FBD of the system and investigate the sensitivities to each variable (hinge friction, mass, CG position, slope, etc.). Good luck.
Best regards,

Matthew Ian Loew

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[ivymike]

The toughest part, in my opinion, will be accounting for the door detent strap (the thing that makes the door pause at a few locations), which will vary from vehicle to vehicle.

 

[NickB]

1) Rent a flatbed tow truck on wednsday.

2) Put everyones car in the parking lot on it one at a time, and measure the angle at which the door closes as the truck bed is tilted up. Do it a few times for each car, using all the doors.

3) Show your boss your results on thursday.

 

[evelrod]

I think Nick is being "cheeky" as Greg puts it but, in this instnce he is spot on. Considering the wide variety of automobiles out there, you have quite a project if you wish to meet you boss's request.
Two extremes---my 1963 Austin Cooper---door will not stay open unless the car is 'nose down'.
Wife's 2001 Lincoln LS---door will remain open on at least a 20+ degree driveway(son in law's place) Even on that slope it requires a definate pull to get it over the detent.

Rod

 

[patprimmer]

Even in one door on one car, it will vary depending on the level and quality of lubrication that may be on the detent strap. ie if there is dirt grease and oil on it, then you clean it, the result will change.

For a short term quick and dirty result, I tend to agree with Nick, only my idea was to park on a level surface and use a trolly jack and an angle finder, which is like a spirit level with a protractor built in.

More professional appearing plan would be to contact the technical service departments of all major car manufacturers and ask if they have specifications or standards for angle or closeing force, If they have one for angle, you are home and dry, however I suspect that they won't, and you will need to calculate the angle from closeing force and door geometry, provided you can collect that data, which I also doubt.

On reflection, quick and dirty looks good.

Test a lot, new and old, clean and dirty, give min, max, median and average values.

I find that when the raw data is poor, the next best course is to just give a lot of it. At least it then looks scientific. Regards
pat

 

[NickB]

I had a lot of really REALLY simple tech support questions this morning, and i guess that coloured my post a little

 

[evelrod]

"If you can't dazzle 'em with brilliance, baffle 'em with BS" Murphy


Rod

 

[GregLocock]

There are standards, but no one who knows what they are will be willing to tell you, I suspect. (For instance, I could find out what we'd use, but it would take me 1/4 hour, playing on a very dull database, and when I told you I'd expect to get sacked, quite rightly). There may be national regs on this so have a look for FMVSS on the web.

I think Nick is on the right track, a sexier experiment involving a force gauge and so on, on a level road, would still fail to answer the question accurately.

Cheers

Greg Locock

 

[ivymike]

by the way, welcome to the site, a'bob.

 

[dmarsh22]

I'm all for the pragmatic approach on this one and I think that Nick and Pat are spot on. I would perhaps, have gone one step further and suggested that you:-

a) Borrow you boss's car
b) Get hold of a high lift jack
c) Arm yourself with a can of WD40 - for lube experiments and, well - do I need to go on....!!

It's Thursday tomorrow - be sure to let us know the result - just I case one of my colleagues gets asked!

Regards,
Dave Marshall

 

[alykabob02]

thanks guys! i talked to my boss about the responses i've been getting from this forum and from the auto manufacturers and he and his clients seem to realize how crazy their question is
it turns out they want the information to determine whether to allow a developer to have steeper driveways that are allowed in the local ordinance

 

[NickB]

I think traction in the winter is more important than the doors closing from the slope. My driveway is pretty steep, and even though the doors stay open for the most part, there's days in the winter i can't park on it, or slide down it while walking to the car.

 

[alykabob02]

i thought that the ice factor was more important too, but they are looking for any information that might help.
sorry to burst your bubbles but i won't be able to run any of your experiments on company time, but my friends and i might have some fun with them! i'll let you know the results when i get them.