Thread: Murphy's Law, catastrophic failure in a very bad place

Originally Posted by Dougal

As pointed out several times already. "Heavy Duty" means nothing. If you drive in a way to prevent shocks overheating then they'll last a very long time.
If you drive at the worst speeds on rough tracks then you'll overheat any shock. The worst speed isn't fast. It's the speed with the least air-movement and most frequent shock movement.

Driving on rough roads doesn't overheat shocks. Driving at slow-moderate speeds without cooling air while regularly using most of the stroke does.

I very much appreciate your point Dougal. But on roads as bad as the Kalumburu or Mitchell Falls tracks, it's a toss-up - drive too slowly and risk overheating the shocks, or drive fast enough to provide them with cooling air, and risk serious damage or a life-threatening crash by hitting a washout, or a tree. I'd always been taught to air down and go slow. Seems everything is a risk.

Originally Posted by GregMilner

I very much appreciate your point Dougal. But on roads as bad as the Kalumburu or Mitchell Falls tracks, it's a toss-up - drive too slowly and risk overheating the shocks, or drive fast enough to provide them with cooling air, and risk serious damage or a life-threatening crash by hitting a washout, or a tree. I'd always been taught to air down and go slow. Seems everything is a risk.

No.

You stop, check them, if necessary let them cool down. Then proceed.

ECU control of shock valving has the opportunity to be inappropriate for some conditions if the algorithms obtained from computer modelling haven't been sufficiently field tested. The bypass valve is normally closed and only opened to the degree considered appropriate for the current wheel height change and change frequency as determined from height sensor value changes and body movement as detected by 3 G-sensors. If insufficient real situation trialing hasn't been done then the shocks could be operating on too firm a setting so that with extended severe use the oil could prematurely overheat. I will be evaluating various manual open settings of the bypass valves to determine whether it could be a useful addition to my LLAMS module for the new generation combined height and CVD (dynamic suspension) ecu. LR might eventually revise the s/w parameters to prevent overheating, if overheating was indeed the cause of the failure.

Originally Posted by Graeme

ECU control of shock valving has the opportunity to be inappropriate for some conditions if the algorithms obtained from computer modelling haven't been sufficiently field tested. The bypass valve is normally closed and only opened to the degree considered appropriate for the current wheel height change and change frequency as determined from height sensor value changes and body movement as detected by 3 G-sensors. If insufficient real situation trialing hasn't been done then the shocks could be operating on too firm a setting so that with extended severe use the oil could prematurely overheat. I will be evaluating various manual open settings of the bypass valves to determine whether it could be a useful addition to my LLAMS module for the new generation combined height and CVD (dynamic suspension) ecu. LR might eventually revise the s/w parameters to prevent overheating, if overheating was indeed the cause of the failure.

Strewth Graeme! That's one helluva explanation:-) But I get it. Overheating seems certainly to be the cause of the problem in this case, if the smoke wafting out from the dripping oil is any indication. Perhaps prior to embarking on the expedition I should have asked the relevant questions here on the forum...er, had I known in advance that shocks could have been a problem, of course!

It may have been a faulty shock rather than any sort of design shortcoming.

I suspect a faulty driving style more than a design fault, given what I now know:-)

Originally Posted by Graeme

ECU control of shock valving has the opportunity to be inappropriate for some conditions if the algorithms obtained from computer modelling haven't been sufficiently field tested. The bypass valve is normally closed and only opened to the degree considered appropriate for the current wheel height change and change frequency as determined from height sensor value changes and body movement as detected by 3 G-sensors. If insufficient real situation trialing hasn't been done then the shocks could be operating on too firm a setting so that with extended severe use the oil could prematurely overheat. I will be evaluating various manual open settings of the bypass valves to determine whether it could be a useful addition to my LLAMS module for the new generation combined height and CVD (dynamic suspension) ecu. LR might eventually revise the s/w parameters to prevent overheating, if overheating was indeed the cause of the failure.

I'm not convinced that less damping will create less heat. It will however create a wallowng situation where the driver may be forced to drive even slower.

The extreme situations at either of of overdamped and underdamped both result in less work done by the damper. But the underdamped condition results in a lot more motion both during and after the impact. The integral of damping force x distance travelled is the energy input to the damper.
Half the force and twice the movement is the same energy.

You'd have to be a brave and highly insured to sell over-rides for active suspension.
In an avoidance situation you can put the vehicle on it's roof far more easily.

Originally Posted by GregMilner

I suspect a faulty driving style more than a design fault, given what I now know:-)

Maybe LR have looked after driver comfort too well. If there's no feedback from the ride that the components are being over-worked then how does the driver know when to ease off?