New Spring Purches

admin

I ordered these axles from a parts shop and they assemble them, but I discovered they don't weld, so the spring purches came tied but not welded on. That's not a problem with me, but the question is do I weld them on parallel to the camber, or horizontal to ground.?   If i weld them on relative to the camber then the springs will be torquing to the outside on compression. If I weld them on horizontal the camber will cause them to torque to the inside.   First time I had to deal with unmounted purches.  Thanks
Reply:What I do is set the axle on the perches in the springs, get the angles right for pinion and caster and snug up the U-bolts a little to hold everything. Then I tack the perches on, take the axle out and weld the perches.
Reply:Originally Posted by ironmangqWhat I do is set the axle on the perches in the springs, get the angles right for pinion and caster and snug up the U-bolts a little to hold everything. Then I tack the perches on, take the axle out and weld the perches.
Reply:Might be missing something here, but is the op talking about a motor driven vehicle or a trailer axle?
Reply:Originally Posted by BrianCMight be missing something here, but is the op talking about a motor driven vehicle or a trailer axle?
Reply:Originally Posted by BrianCMight be missing something here, but is the op talking about a motor driven vehicle or a trailer axle?
Reply:Caster will not apply to a trailer axle as it's an angular function to help steering wheels return to center after completion of a turn. All cambered trailer axles I've worked with have been set at the neutral plane meaning perpendicular to the ground or horizontal plane. Cambered axles tend to flatten or straighten to a camber value nearing zero at full load capacity. If the original poster does mean a powered drive axle I hope they understand driveline angles and how to properly set them before mounting those perches arbitrarily and the resulting damage getting expensive very quickly.SlobPurveyor of intimate unparalleled knowledge of nothing about everything.Oh yeah, also an unabashed internet "Troll" too.....
Reply:Originally Posted by mike837goDoesn't matter, the process is still pretty much the same. Locate the axle perfectly, use the mounting hardware to hold things for tacking. Disassemble. Weld everthing up properly. Assemble for use!
Reply:Sorry for the delay on responses.What I'm saying is that from an engineering standpoint, either welding the perches relative to the camber(welding 'on' the camber), or, the other option of welding the perches on the camber, but relative to ground and horizontal to it, will cause tangent torque problems on the spring leaves. In order to get them horizontal in the second example, the outboard flanges of the perch need to be raised 1/16 or so to level out the top of the perches. Either way you do it, the problem is still there. A simpler analogy would be if you had a hill. Now you have two posts with flat plates on the bottom set at 90Degrees to the vertical post. Set flat on a horizontal surface the post would of course be vertical. Put the other post 50 ft away from the first, and the distance from the bottoms would be the same as the distance from the tops, ie: 50 ft.Now do the same but put one post on one side of the hill and another on the other. Measure the distance at the top and it is wider than at the bottom.The camber is the hill. The tops of the posts are the point where the frame is attached to the springs. Now if you press the camber down flat, the springs want to move inward at the top but can't because they're welded to that distance.Welding the perches by horizontal reference to the ground creates the same problem, just that initially, the eyes at the top of the springs are closer together. Press down on the camber and the springs still want to move inwards at the top.My question is what do you guys use that works without metal fatigue?My guess is that typically, horizontal movement of the top spring eyes would be minimal although some stress is still there. So I'm going for the 'weld horizontal to the ground, rather than relative to the camber' method. Like I said, it means that I'll need to lift the outboard legs of the perch a fraction of an inch to accomplish this.It would still be interesting to hear what the engineers say about it.Last edited by Rosebud; 03-28-2015 at 08:42 PM.
Reply:The last rear axle I did I used 5 degrees down on the pinion in relation to the drive shaft. Had to use shims as the axle had the perches welded on, I would have rather had the perches as you have, just weld in place.RegardsDave