Bump steer in beam axles
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- čas přidán 31. 01. 2021
- In this video we examine the phenomenon of bump steer in beam axles. I'll explain what bump steer is, what causes bump steer and most importantly how you can eliminate or at least control it.
I'll explain how the motion of the steering drag link interacts with the motion of the axle to cause bump steer. I'll also explain that some designs of suspension, like four link, leaf springs and A-frame are more susceptible to bump steer than suspension that uses a Panhard rod. I'll also show how you can make bump steer really bad by mounting the Panhard rod incorrectly.
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! - Auta a dopravní prostředky
Great video. Super easy to understand without being patronising. I think I have a pretty good understanding of the subject but this video has helped me understand a flaw in my planned suspension set up. Thank you.
Thanks for this video, great illustrations and no nonsense 👏
Helped me a lot. Clear and visual
underated
تستحق مليون لايك، شكراً جزيلاً
Subscribed from reddit. Good video. I'll watch the rest of them. Hopefully one of them goes over "death wobble"
Subscribed.
Thank you for making such clear videos! May I know your name please?
ارجو منك المساعده،اذا اضفت علبه توجيه ورابط سحب في الجهه اليمين ،هل هناك احتمالات جيده أم سيئه
The original question translated - “Please help. If I add a steering box and a pull link on the right side, are there good or bad possibilities?”
Answer - I’m not entirely sure I understand the question (even after translation). If you’re asking about having the steering box on the opposite side of the vehicle from the steering wheel, then that would certainly create some complications in getting the linkage from the steering wheel to the steering box. It’s not impossible though.
I really need more information from you to answer your question properly.
I don't like panhard rod. I much prefer symmetrical action of the suspension. How can you get zero bump steer on a beam axle with a 0 lateral movement suspension geometry while also still retaining steering feedback and correct return-to-center alignment? Would a 90-degree pitman arm in the center of the axle do it? is there some kind of fancy "watts-linkage" esque setup that you can do to your steering that would do it?
I agree that having your axle move sideways in bump doesn’t sound like a great idea, although it seems to work ok in practice. I can’t think of any production examples of zero-bump steering linkages like you describe. To make it work you’d need to work out which axis your axle couldn’t move around and then send a steering shaft down that axis. So let’s suppose you built a suspension linkage that completely eliminated roll steer, so it moved up and down along a completely straight path (imagine a Watts linkage turned 90 degrees at both ends of the axle). You could then have a vertical steering shaft going down onto the centre of the axle. You’d need a way of compensating for the vertical movement, but that’s not that difficult. The question you’d have to ask yourself is whether all that complexity was really worth it for the handling improvement you’d get - it would still be a beam axle after all.
Can a ifs 4x4 get bump steer? Or is this just for solid axle ?
Independent setups also suffer from bump steer, but it tends to happen symmetrically - so when both wheels on an independent axle go into bump they toe in or toe out together. Lots of designs actually take advantage of this behaviour to change the way the vehicle corners, so as the vehicle leans over in a corner you can use bump steer to introduce some passive steering to create understeer, but that probably needs another video to explain properly.
Is it a bigger problem when the rear axle is stiffer or softer, if you have bump oversteer?
If the suspension is stiffer in roll then you will experience less bump steer, because the amount of steering effect you get is directly related to the amount of roll travel you get. The slight complication here is that making the rear axle stiffer in roll makes it more prone to oversteer due to weight transferring from the inside wheel to the outside, so you might improve the bump steer situation, but still get oversteer - life can be terribly unfair 🤷♂️
@@Offroadvehicleengineering is it the same with the springs? Or is it different there?
The springs contribute to roll stiffness, indeed unless you have an anti roll bar then all of your roll stiffness comes from the springs. If you do have an anti roll bar then you can play tunes on the suspension to give you the combination of roll and vertical stiffness that you want.
@@Offroadvehicleengineering and if you make your front axle (arb and springs) stiff, would you also make the dampers softer on the front axle?
do you have a discord account?