Suspension – Attachment Hardware

Springs are useless without a way to attach them to the frame and the axle. The hardware shown in Figures 3.15 through 3.17 are typical of the variety of parts needed to accomplish this task. Figure 3.17 will help you identify and name each of the individual parts. Figure 3.18 through 3.20 illustrate the standard assembly order and dimensions for the three most common leaf spring configurations-single axle slipper, single axle two-eye, tandem axle two-eye springs. Notice that only a few parts are welded to the trailer frame while the rest are bolted in place. Springs themselves are always bolted, never welded. Springs are a highly heat treated special formula steel whose properties remain intact unless embrittled with heat from a weld. Welded spring steel will fatigue and crack from only a small number of load cycles-probably your first trip out. So please don’t weld springs. (Sorry about the lecture, but I have seen springs welded.)

Of the welded parts-hangers, spring eyes and slipper tubes- specified dimensions can certainly simplify the installation process. Figure 3.18 through 3.20 give dimensions recommended for these installations. It is possible that your spring dimensions are slightly different than the ones shown here, so be sure to ask your supplier for installation instructions. Additional fitting gussets and diamond doublers to reinforce these parts are also an inexpensive way to gain extra strength. Calculations indicate the need for more weld on these parts and a knowledge of stress concentration and experience from farm equipment reinforce that assessment. Hanger manufacturers never seemed to want to make hangers with longer bases; hence these solutions were sought. Patterns for these simple, highly effective weld-on parts are soon to be available from Techni-Visions.

Bolted parts include rockers, link plates and springs. Grade 5 serrated bolts, 9/16-inch diameter by 3-inch length are used for this purpose. If these bolts are installed with the lock nuts to the outside, loosening is much more easily detectable during periodic inspection. Any necessary repairs or replacements can then be performed. If the lock nuts which are used on these 3-inch bolts are removed, their locking ability should be rechecked before being re-used. We found many that could not be used more than once. The expense to replace used nuts with new lock nuts is minimal and well worth the trouble to order a few extra pieces. If you cannot obtain more of these mechanical style lock nuts, Loctite can be used temporarily but the surfaces have to be extremely clean for this method to be effective. Given the environment and the non plated bolts, this cleanliness may be difficult to achieve. Thus, a new lock nut should be installed as soon as possible. With the nut to the outside, this replacement is relatively easy.

The axle is attached to the spring with five hole plates and U-bolts of a size to fit the axle width and shape. Five-hole plates come with various hole spacings to accommodate different axle sizes-1-1/2-in, 1-3/4-in, 2-in, 2-1/4-in, 2-1/2-in, 2-3/8-in round, 3-in round. U-bolts selected with these plates must be long enough to extend past the spring height and the axle height, yet short enough not to extend past the bottom of the wheel. U- bolts that extend past the wheel rim are illegal in most states, since a flat tire will permit them to gouge the pavement—a disagreeable occurrence. Non-locking nuts and spring washers are used on the bottom side to hold the spring, axle and five-hole plate together. These require a good amount of tightening-enough to flatten the lock washers. Hardware for springs and axle assembly can usually be ordered as a set, which greatly simplifies this myriad of dimensions and parts. Even simpler are the new torsion suspensions, our next topic.

• A. Tall hanger, for tandem springs;
• B. Fitting gusset;
• C. Short hanger;
• D. Spring eye, for two-eye springs;
• E. Slipper tube;
• F. Tandem rocker;
• G. Diamond doubler;
• H. Link plate;
• I. Five-hole plate;
• J. Ubolts of various lengths and widths to accommodate many different axle shapes and sizes:
  • 1-3/4square, 1-1/2″square;
  • 2-3/8″ square;
  • 3″ round, 2-3/8″ round;
  • 2″ square;
• K. Hex nuts with lock washers, 9/16″;
• L. 3-inch serrated capscrew, 9/16″;
• M. Lock nut, 9/16″.