Re: [MV] Vehicle Gradeability

Alan Bowes (Alan_Bowes@phast.com)
Tue, 17 Mar 1998 14:35:26 -0700

>>> "ROBERT GALLAGHER" <hooterdog@worldnet.att.net> 03/16/98 08:22PM >>>
> Q: How is Maximum Gradability of a vehicle computed?
**********************************************

Well, I don't know how it was done back then, but the SAE (Society of =
Automotive Engineers) has devised several different standard methods for =
determining gradeability. I don't know which, if any, military organization=
s are using these standards, but apparently a lot of manufacturers and =
other organizations are complying with them.

Depending on what type of vehicle is involved, you would have to follow a =
different standard. For example:

- Electric Vehicle Acceleration, Gradeability, and Deceleration test =
procedure, SAE J 1666, 01-May-93, $42.00,=20
- Construction and industrial equipment--Gradeability, SAE J 950, =
01-Oct-85, $24.00
- Trucks and Buses - Gradeability, SAE J 2188, 01-Mar-96, $42.00

It wouldn't surprise me at all if the gradeability ratings are now =
produced mathematically, instead of by direct testing on slopes.

Some other practical aspects that might be considered when determining =
gradeability could include:
- Visibility factors (could be very important).
- Ability to restart on a hill at gross weight.
- Ability to stop on a hill at gross weight.
- Maximum climbable grade at gross weight on different surfaces and with =
different tires.
- Oil pickup angle limitations.
- Fuel pickup angle limitations.
- Carb bowl fuel level limitations.
- Braking ability at gross weight for sustained downgrades.
- Cargo types.
- Driver and passenger ergonomics.
- etc.

It would be interesting if someone could locate the original testing =
methodology used for MVs over the years.

Alan

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