Ironton (NT) Spring Binder Bolt Reversal (spring over axle)

Ask questions about Harbor Freight trailers, or questions about building your own...

Re: Ironton (NT) Spring Binder Bolt Reversal (spring over ax

Postby Socal Tom » Mon Mar 06, 2017 10:22 pm

working on it wrote:
Socal Tom wrote:I did a spring over on mine a couple of years back, then I pulled it across the Mojave desert ( Mojave Rd), 109 miles of dirt road. According to the guys following me, the trailer was catching air on a regular basis over one stretch. ( I ended up eating a rim). The u bolts were fine. In a spring under config, the u bolts hold up the trailer weight, in spring over, the u bolts hold up the axle weight.
Looks like your raising the height of the trailer, pretty much matching the roofline and floor height of your Jeep, allowed you to allow a higher volume of air pass virtually straight thru, unimpeded. The shape of your trailer, is not unlike a wing, truncated at the tail. If you had enough groundspeed over the (presumably) flat Mojave desert, and if you got just a small bounce were towing a sailplane.
how-airfoil-wing-makes-A TRAILER-lift.png

It wasn't the shape that made it fly, it was more likely lack of shock absorbers. The springs would compress on a bump and send it flying. If your theory was correct it would fly on the freeway.

Sent from my Lenovo A7600-F using Tapatalk
Socal Tom
Donating Member
Posts: 1049
Images: 9
Joined: Sun Jun 29, 2008 9:21 am
Location: San Diego Ca

Re: Ironton (NT) Spring Binder Bolt Reversal (spring over ax

Postby dancam » Tue Mar 07, 2017 2:18 pm

QueticoBill wrote:So I've been studying parts and come to the conclusion that the top of the axle is 5 1/2" from frame when mounted under leaf springs and 3 1/4" when mounted over leaf springs. Somewhere, likely a boat trailer site, I read that trailers are designed so the vertical "travel" of the spring/axle should not exceed 1 1/2-2". E-trailer suggests 2-2 1/2", and to allow 3" for tire to fender/wheel well clearance. So - 3 1/4" is snug but should be OK especially not at maximum design load. I'm predicting around 1250 loaded for towing.

This begs the other question, are the u-bolts strong enough to "hang" the trailer from the axle, as opposed to just keeping it on top of the axle? On one side, steel is really strong in tension. On the other hand, no idea of the quality of the plates and bolts. Unfortunately, these seem to be an uncommon size - 2" springs and 1 3/4" square axle.

FWIW I'm thinking I will drill "bottom" of axle for the leaf spring bolt head rather than installing the channel upside down.

What you found in spring travel is what i found as well.
I am also flipping my axle but never even thought about the u-bolts taking all the weight :/
However i started with a 2000pound trailer and axle, bought a 3500 pound axle with brakes and the u-bolts for it are huge compared with the ones for a 2000 pound axle.
So you have a few options if your worried.
Buy a bigger axle.
Go to a nut and bolt place and ask them if they have stronger u-bolts than what you have.
Buy u-bolts for the next size up axle and machine a metal shim so it holds your axle.

Sent from my SM-G920W8 using Tapatalk
500 Club
Posts: 534
Joined: Wed Jun 01, 2016 3:27 am
Location: Edmonton Alberta Canada


Return to Trailer and Chassis Secrets

Who is online

Users browsing this forum: No registered users and 1 guest