bill van snorkle Posted August 22, 2006 Share Posted August 22, 2006 It has been several years now since I converted my series 2A to coil front suspension, but before that I had always meant to have a go at doing a front spring shackle reversal. About 30 years ago I owned two almost identical series 1 80 inch Land Rovers .One was a 1948 with front shackles, the other was a 1950 with rear shackles.Both vehicles were in good condition with near new springs and dampers. In various cross country comparison tests, ie steep rocky hill climbs and surmounting short vertical obstacles etc the 1948 was always superior and just got on with it ,whereas the 1951 model would hop up and down or the front end would rear up causing the truck to slew sideways to the slope in a single bound, which can be pretty scarey on any vehicle let alone one with such a short wheelbase and narrow wheel track. Anyway, many years of offroad travelling in my series 2A in company with Toyota LandCruisers, Nissan Patrols, Jeeps etc has convinced me that for mountain goat type offroading, Landeys have got their front shackles at the wrong end of the spring. I'll give an example of what I have observed happens on a steep climb. When a leaf spring LandRover is climbing a steep difficult slope some of the front end weight is transferred to the rear axle by gravity so the front springs are unloaded slightly and the front of the vehicle sits higher on its springs. Due to torque reaction, the front diff pinion wants to rotate downwards causing the shackles to swing forward, lifting the front of the vehicle even higher. The spring now has alot of camber (arch) both for and aft of the axle assembly, so now the front axle is even less positively located to the chassis. Any forward thrust that the front axle assembly can develop merely cambers up the spring even more until the stored energy in the spring is greater than the thrust of the axle, then it releases this energy, sometimes so violently that the front end can leap into the air. I have witnessed a Stage one V8 front end literally leap sideways 6 feet due to the release of this pent up energy resuting in two broken springs, snapped propshaft and both expensive Koni dampers destroyed. Now let me attempt to explain what happens when a Toyota Landcruiser with front shackles attempts the same climb. Gravity is gravity so weight transfer to the rear still occurs, so the tendency of the front end to sit higher is still the same,The front diff pinion due to torque reaction still wants to rotate downwards, but because the shackles are at the front of the spring, they swing forward and actually pull the sprung mass down, counteracting weight transfer. Because the spring is compressed, the spring is also relatively flat and straight giving the axle a more positive location to the frame to transmit forward thrust thus increasing traction, The more forward thrust the front axle can develop, the more the front end pulls down compared to vice versa with the LandRover setup. This makes the vehicle both more capable and safer to operate in steep and offcamber terrain. Another advantage which I won't go into much detail about is that the front propshaft slip joints last a heck of alot longer. Is anyone reading this convinced enough by my argument to give shackle reversal serious consideration ? By fabricating a few simple parts you can experiment with the principal without disturbing your chassis . If anyone is interested I will explain how in a later post. Bill. Quote Link to comment Share on other sites More sharing options...
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