handy1882 Posted June 23, 2012 Share Posted June 23, 2012 Hi Everyone, This might have been better in the 'i may be stupid, but..' section, but I was just wondering if anyone has seen leaf springs like this before? Seems quite unusual, is there a name for this type? I thought the main leaf was quite badly broken, but then noticed that the "breaks" were all 3" apart. When i took it all to bits, it was made up of jigsaw type pieces which seem to act as packers with the cast spring eyes slotted on the end. I thought it might be for ease of maintenance if you needed to change the spring bushes by just throwing away the ends and putting new ones in, but i can really see any advantage to this as you would still need to take most of the spring to bits. All four rear springs are the same. Could it be for down rating the capacity of the truck for taxation purposes? Or is this original? Any thoughts out there? Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted June 23, 2012 Share Posted June 23, 2012 How amazing. Are the axles restrained by tie rods or something? Because these springs would be no good for lateral restraint of axles. In fact I wonder if they are like this to allow a bit of side play so that main leaf does not take the lateral loading ?? Quote Link to comment Share on other sites More sharing options...
handy1882 Posted June 23, 2012 Author Share Posted June 23, 2012 (edited) Thanks NOS, Lateral loading is a possibility, as the whole rear bogie is designed to be as flexible as possible and is quite a complicated setup, not sure i understand quite how it all works yet. There are no tie rods to keep them in place just bumpstops and check straps to stop them going up or down too far. the diffs are kept in the correct arc by some swinging arms which bolt onto the top of the chassis between the axles and mounted to each diff. The axles themselves are mounted in the assembley by 4" dia bronze balls which fit in the clamps shown in the first picture in the first post. The assembley is mounted to the chassis via a central main pivot. That probably wasn't a very good explanation so i'll let some pictures do the talking! Two pictures showing the swinging arms bolted to the top of the chassis and diffs This is one of the chassis mounts onto the central pivot, the swinging arm centre section bolts on the top flat. There is also a combined bumpstop/checkstrap still round the axle. Chassis mount removed showing how the springs are mounted to the central pivot. This shows the axle mounts and spring pins. One of the bronze axle mounting balls. All of that is so the truck can do this sort of thing! This shows some tracks around the rear wheels, so the axles need to pivot and move all around but keep the same wheel centres so the tracks stay on. clever bit of design really! Edited June 23, 2012 by handy1882 Missed a bit out Quote Link to comment Share on other sites More sharing options...
Mk3iain Posted June 23, 2012 Share Posted June 23, 2012 Very strange, its looks as if the main leaf is like flat chain, not taking part in the spring effort but flexing up and down but fixed fore and aft. Why?...:confused: Quote Link to comment Share on other sites More sharing options...
N.O.S. Posted June 23, 2012 Share Posted June 23, 2012 Very strange, its looks as if the main leaf is like flat chain, not taking part in the spring effort but flexing up and down but fixed fore and aft. Why?...:confused: I think you've got it - it's done so that the thick leave acts only as a strong locator fore and aft for the axles, and to make sure it does not contribute to supporting the load, therefore the spring is relatively soft for improved flexibility. If that big leave was one piece the spring would be too strong? Or something like that - remember single or 2 / 3 leaf springs were not considered 'the done thing' back then :-D Quote Link to comment Share on other sites More sharing options...
handy1882 Posted June 23, 2012 Author Share Posted June 23, 2012 Thanks N.O.S, that sounds pretty good to me! The axles are off a 3ton truck, so even fully loaded there would be 1 1/2 ton on each set of springs so 3/4ton taken by each spring? I guess full spring with a solid main leaf probably would be a bit over the top? Quote Link to comment Share on other sites More sharing options...
Runflat Posted June 23, 2012 Share Posted June 23, 2012 ...the whole rear bogie is designed to be as flexible as possible and is quite a complicated setup, not sure i understand quite how it all works yet. As I understand things, the intention is that the springs are only subjected to load carrying forces. Torque reaction is not taken from axle to axle but from each axle to the chassis frame by the short rods between the worm casings of each axle and the cross-member midway between them. Thus the torque produces no vertical load components. When torque reactions are not balanced like this, the leading driving axle tends to lift and the trailing driving wheels to dig in the ground. The worm shafts also remain parallel and thus the angular velocity of them and their wheels remains unaffected. With regard to the laced spring, I wonder if it is to ease the twisting that ocurrs when travelling over rough ground - if say, on one side, the leading wheel were raised and the trailing lowered, the wheels would be leaning in opposite directions from the vertical position, causing the springs to twist? Quote Link to comment Share on other sites More sharing options...
handy1882 Posted June 23, 2012 Author Share Posted June 23, 2012 Thank you Runflat, that all makes a lot of sense! Quote Link to comment Share on other sites More sharing options...
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