How to Construct Custom Axle for Scratch-Built Trailer Using Spindle # TRU37FR

Question:

We are building this trailer from scratch for a FFA project. If I want to make a standard 96inch wide face to face axle: how long do we cut the pipe? The deck of our trailer is 83. I was told to get a 3inch OD pipe with a .25 wall. Any advise would help. We intended on making 7000 axles.

asked by: Scotty M

Helpful Expert Reply:

First, I wish you good luck with your build project. No one eats without our farmers!

Do please note that DOT regulations limit trailers to a width of no more than 103-inches for on-road use. If your trailer will see only agro use and never go on road this is not a concern, but do please keep this in mind if there is any chance the trailer will need to be pulled on public roads. You could be fined for pulling an oversize trailer without first obtaining the required permits.

If your planned axle is to be 96-inches wide from hub face to hub face, once you add your tires/wheels on each side you will be over the maximum 103-inch overall width. I pulled a sample of the 3-inch EZ Lube Spindle you referenced, part # TRU37FR , and also of a compatible hub/drum assembly # 42866UC3-EZ to help you determine how long your axle tube can be with these spindles and hubs in place.

With this hub in place on the spindle the hub face (where the wheel mounting surface will contact it) will be 4-1/2-inches out from the rear side of the brake mounting flange. You need also to add the width of your planned wheels/tires and then double that total dimension to account for both ends of the axle. This will tell you how long your axle tube can be and still be legal.

For a 7000-lb axle it is recommended that you hub face to spring center dimension is between 13- and 18-inches. Also it is recommended to have at least a 1-inch gap between the inside tire wall and the closest part of the trailer when under a load.

Also note that neither you nor I have any way to be certain of the weight capacity of your scratch-built axle or of your entire trailer. Without the usual R&D and testing performed by axle and trailer manufacturers you will be in unknown territory as to the actual weight capacity of your project. This is an important safety concern and may make a locally store-bought axle a better option.