Monthly Archives: October 2016

FOUR into ONE: Quad Shock absorbers for off-road caravans

Quad shock absorber

1 Quad shock absorber equals 4 twin tube shock per side

At it’s worst, the famous Kalumburu road can have the toughest corrugations that will test any set of shock absorbers. It is 187km to Mitchell Falls from Drysdale station and it may take you 8 hours. The grading of this road is hard to predict. It is done by a different local authority to the Gibb River road. However, Mitchell falls will leave you in awe, so if you have travelled all the way to the Kimberley, it is recommended to do this last 180kms.

Kimberley Kampers have nearly 7,000 units in off road travel and we estimate several hundred or even a thousand are in the Kimberley region in any one year. It is where we take our name from after all. With several years of statistics, we also understand what works best in shock absorbers. In the 1990’s we exclusively used Old Man Emu shock absorbers but found they would not hold up in the corrugations. The urethane bushes would “melt” and then the shock collapse.  Before changing to large 50mm Mono-tube shocks, we tested each of the major brands of twin tube shock absorbers. The root cause of the majority of failures is the heat energy generated in the shock absorber.

Our testing involved sophisticated heat energy monitoring by a desert racing team from USA.
What we discovered shocked the team as well as ourselves. Over the corrugations, the shock absorbers were only moving 10-20mm. This little movement did not move the oil around. As the oil is not pulsating up and down the shock, the buildup in oil temperature is immediately around the seals. Unless the shock can radiate this heat faster than the rate of build up , the seals were over heat and the shock is guaranteed to fail. This also explained why the urethane bushes “melted” in the Old Man Emu shock absorbers.

We saw 4.5kw of heat energy per side when the tire pressures were 50 PSI. When the tire pressures were 20 PSI we saw only 1.2kW of heat energy. Tire pressure is one of the major factors as well as speed to keeping this heat energy within specification. Doubling the number of shocks would not improve the situation as one will always work harder and be the first to fail.twin-tube-and-monotube-shock-piston-size

The test shocks with remote reservoirs did not give a better result. In fact they were slightly poorer as the heat radiating from the remote reservoir was absorbed by the main shock.

For our larger camper trailers and off-road caravans, Kimberley decided on the 50mm Mono-tube because it has double the outside area to radiate the heat compared to twin tube shocks as well as a lower velocity of oil passing through the dampening disc. The image below is a twin tube disc from inside a shock absorber compared to a large Mono-tube on the right. You can see the considerable difference.

The rally industry uses sophisticated bypass and remote reservoir shocks for improved performance. However, these are of no use for off-road caravans because of the reasons above. They would be destroyed in short time. We have been searching for an even larger diameter mono-tube that can perform even better. The larger the diameter mono-tube shock absorbers radiate more heat. They also reduce the heat generated by the passing oil because of a much larger diameter piston/disc inside

Now we have one. The new QUAD mono-tube model is 66mm diameter and the equivalent to 4 twin tube shock absorbers per side. There is no urethane bush as we are sticking to the steel spherical bushes for durability. This single Monotube shock is the equivalent to FOUR twin tube shocks.

This range will be fitted to the new Kruiser E Class off road caravan to start with and then progressively introduced to the rest of the range.

As background:

Mono-tube vs twin tube shock absorbers

Mono-tube vs twin tube shock absorbers

Twin-tube shocks have an inner tube where the dampening piston moves up and down. Outside of this tube is an outer tube, which is the reservoir for the oil. As a result, In this design the actual “dampening area” is much smaller than the shock diameter. The term “gas shock” usually refers to this same twin tube design with low pressure nitrogen gas added to replace any air. This assists in keeping the oil moving through the dampening valve with lower performance fade.

Mono-tube shocks simplify the damping process. The outer tube is eliminated, allowing the pressure tube to be the same as a twin-tube shock in the same overall package size. A piston with specific valving is mounted to a rod that controls both the compression and rebound of the cycle. High pressure nitrogen is added to reduce fade and improve performance.

66mm-monotube-shocks-on-test-with-remote-reservoirThe photo on the right shows our testing setup with a remote reservoir and 8 stage remote adjustable dampening settings.

The remote reservoir is used for testing purposes only and is not part of the standard setup.

The results were excellent. These new shocks are shipping from December 2016 on E Class Models.

Ballina October 20th 2016