How to Determine Axle Spacing of Homemade Dump Bed Trailer

Question:

Hi, building a farm tipping trailer 14 foot by 8 foot, puting in a tandem axle with a rating of 3500kg at 60km/hr per braked stud axle 4 stubs on 500/50 by 17r 18ply tyres, what is the ideal spacing of these? Also puting in sprung draw with 7 by 3 inch channel seam welded, how far should the sprung drawbar extend back into the chaßis body?. Any help greatly appreciated, thanks.

asked by: James

Expert Reply:

So with twin 3500 lb axles, your trailer's GVWR will end up being about 7000 lbs. You'll want to place the axles to that the trailer tongue weight is no greater than 15% of the trailer's weight. You'll want to mock up the trailer so that the midpoint of the two axles sits about 1/3 of the way from the rear of the trailer to the center of the trailer ball. You'll want to install the tongue first, according to the sprung drawbar's manufacturer's recommendations. At that point, you'll weigh the trailer under both sets of wheels and at the tongue. If you find the tongue weight is greater than 15% or less than 10%, you'll work the formulas I've linked for you which will tell you how much you need to move the axle center point forward or rearward.

expert reply by: Mike L