Rear Shakle Position Theory, Trailer Axles

[andyfletcher]

Spiker:

"rear srpinf front mount actually moves UP farther than it does BACK. ...."

I haven't thought of that.

"can actually cause a bit more damage to a front spring than the back spring as once the center pivioting section bottoms out rearward there is no where for the front springs extra mass to GO, under this senerio the max back and spring have to be dead level so if the spring wants to "Reverse bend" some it can. if the bottom out spot still has an arch in the front spring then that spring load is transfered right into the springs eye and a spring can then break the eyelet or the mount."

Yeah, I realized about the reverse bend and didn't consider it in my theory because I figured by this time when the guy has reached his max load, he'd might consider lightening up a bit, rather than hitting a pot hole adding shock loads to the math. (by this time the spindle is cussin pretty bad too). /forums/images/graemlins/smile.gif

A guy I know had a good idea to lessen excessive load on rear axle when rear loading. He took 2 galvanized boat dock screw jacks with the square threads, cut out the nut section and attaches them hook fashion to each rear corner of the trailer frame. He can take the nuts off by unhooking them and stores them in a box on the trailer.

"flatten out the arch and if the shackel is over 45 degrees then it is over stressing the rear spring by again"

Agree, but I'd feel safer with no more than 20 or even 30.

"front of the tires should face the inside by 2~3 degrees"

I always understood toe in is partially to offset negative factors caused by steering. Anyway never used it on trailers and never had a problem. I set em dead straight.

Andy

 

[andyfletcher]

Nat:

I didn't show that in my original drawing. I make mine out of 1/4in plate. The spring attaches between them. They have female eye connectors and I don't use shakles there, just a standard bolt. I do it this way to save shakles, plus I like doing metal work.

Your right, I'm not using the conventional method. The factory equalizer has a male eyelet too because you need hanging shakles to attach to the spring eyelets.

Andy

 

[SPIKER]

andy: the 2~3 degrees IN (tow in) is more to compensate for the rolling resistance of the tire it's self. as the resistance to movement actually PULLS the tire backwards while traveling forwards. that 2~3 degrees simply makes the tread wear patern more even... (least that was explination I got many many many years back...) thinking about a SOLID tire that is not needed as the tire does not FLEX on the side to side wall.

caster & camber & toe-in is terms mostly assoiated with steerable front wheels.
Camber in is used for most anything that HAS wheels. but usually is not concerned with on MOST situations that are not shigh speed long distance devices. Camber & toe in also can help make the trailer PULL better other wise the thing can actually want to WIGGLE or TAIL WAG if it is off very much.

(I may have my camber & caster terms messed up as I'm a bit old & rusty.) acmber top tilt in/out, caster is the angle back & forth AROUND the wheel bearing load and usually tilted BACK so the steering will "Self Center or Self Correct back to 0 input" on a car. ) I belive. /forums/images/graemlins/tongue.gif /forums/images/graemlins/confused.gif /forums/images/graemlins/crazy.gif

Mark M

 

[mrcaptainbob]

You're right on all those counts, Spiker. Interesting thread that's going here. Am working with my son on his two axle and I mentioned about this TBN thread. He launched into a pretty good explanation of the same thing that's been said here. The forward eye of the front spring, rear eye of the rear spring are 'hard' mounted to the frame to maintain axle attitude. Shackles go on the equalizer. He also brought up another good point about camber on trailers being as important and just about for the same reason as the toe angles. Was another fun topic for me with my son.