Slope Climbing - Off-road vehicle fundamentals
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- čas přidán 8. 09. 2024
- In this video I explain the fundamental theory that determines whether or not an off-road vehicle can climb a slope or not.
The approach taken is very simplified and is based on simple trigonometry and coefficients of friction. It is assumed that the vehicle is four-wheel drive, because that allows all of the weight of the vehicle to be used to produce traction. In a two-wheel drive vehicle, only a proportion of the vehicle's weight can be used to produce traction. It is also necessary to determine weight distribution and the effect of weight shift when calculating for a two-wheel drive vehicle.
I mention that 5,000Nm would be a typical value for wheel torque in a SUV, which is true, but I discreetly ignore the fact that the vehicle has four wheels, each of which might have 5,000Nm of torque available, so in total this vehicle could have 40,000N of thrust, although it couldn't actually apply all that thrust to the surface because it only weighs 20,000N.
When talking about vehicle weight I use Newtons as the unit of measurement. To calculate the weight in Newtons from the mass of the vehicle you should multiple by 9.81 - the value for acceleration due to gravity (on Earth at least). In this case the vehicle has a mass of about 2,000kg, which is fairly typical for SUV type vehicles.
Reading List
Books
Please ensure you use the correct UK or USA link as they take you to different Amazon sites.
Theory of Ground Vehicles
This is probably the most significant book still in print on the subject of off-road vehicles, although it also covers quite a lot of on-road content and has a chapter on hover craft. It isn't an especially user friendly book, but is probably the most detailed book on the science of off-road vehicle engineering available.
UK Link amzn.to/2SBLzat
USA Link amzn.to/3be6HtF
Chassis Design Principles and Analysis
This book was prepared from the notes of Maurice Olley who was one of the great vehicle designers of the 20th century. This is a very technical book and certainly not for the feint-hearted, but if you are serious about understanding suspension design then this is the most comprehensive book ever written on the subject.
UK Link amzn.to/2RzNPP4
USA Link amzn.to/3xQgm3k
Car Suspension and Handling
This is a very good and easily accessible book on the topic of car suspension and handling. It doesn't specifically cover off-road vehicles, but has a great deal of theory that is relevant to off-road vehicle engineers. It is also the cheapest book on my list!
UK Link amzn.to/3vQiKVT
USA Link amzn.to/3hc60ot
Tires, Suspension and Handling
This is also a very comprehensive and relatively easily accessible book on the subject of car suspension and handling. Again it doesn't have any specific off-road vehicle content, but is a very useful book for off-road vehicle engineers all the same.
UK Link amzn.to/3xXH22b
USA Link amzn.to/3uxXfcq
The links below each of these books will take you to Amazon, where you may purchase them. The links are what are known as Affiliate Links, which means that by clicking on the link Amazon will pay me a small commission on any purchase you make on the Amazon site within 24 hours of clicking the link. This applies to any qualifying purchase you make, so it doesn't matter if you click on one of my links and then by a different book. You will not be charged extra for using my links, in effect Amazon will pay me a referral fee. Amazon's official wording is "As an Amazon Associate I earn from qualifying purchases." By using these links you will be making a small contribution to support the production of the videos on this channel. Thanks for your support!
The jeep icon used in this video was adapted from pixabay.com/us...
This is no doubt the best off roading channel ❤
Thanks
I'm sending every offroad noob to your channel. AWESOME CONTENT!!!!! Put theory into practice at my offroad park.
That’s good to hear, thank you! Are there any other topics you’d like to see?
@@Offroadvehicleengineering Staying with the theme of slope climbing, include additional information on tire pressure effects and optimal tire tread type for terrain type (rock/dirt/sand). These factors effect traction but the numbers from calculations are better than "seat of the pants" assessments. Also "sticky" tire vs. regular tire would be interesting. Tires are one of the easiest things to alter on a vehicle so I think having a technical resource to inform the process would be great, from selecting the tire type to air pressure for the terrain :)
Great content!
I appreciate the engineering approach to understanding the practical forces at work when offroading. One of the basics to stay out of trouble is to avoid driving across hills, however the situation arises and my consternation might be assuaged if you examine it.
Thanks for the comment. Vehicle stability is on my list of videos for the near future
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N00b question: If I understood the early bit correctly, coefficient of friction and co-ef of rolling resistance are not the same thing...? With the latter, it's used to calculate the amount of force required to push it forward?
Hi Adil, that’s not a noob question at all! Yes you’re right, coefficient of friction determines how much grip you have available, whereas coefficient of rolling resistance determines how hard it is to move the vehicle forwards. I’m planning a video on this very topic soon, so watch this space.
@@Offroadvehicleengineering understood, thanks.
@@Offroadvehicleengineering Off-topic but are you open to taking questions via content requests? Maybe a Google form link? I wanted to ask why vehicles automatically switch off traction control when 4L is brought on. Thanks.