Fitting Teddy axles on the line

Scope

This guide covers fitting Teddy spring and torsion axles to a trailer frame. The trailer manufacturer is responsible for the frame, the choice of axle capacity and position, tire and wheel selection, clearances, the brake system as a whole, and compliance with the regulations that apply to the finished trailer.

Receiving and handling

• Check the count and look for shipping damage before signing for the load. Note any damage on the delivery receipt.
• Leave the wrap on the drums and the caps on the studs until the axle is at the line.
• Lift with slings around the beam or housing, close to each end. Do not lift by the hubs, the brakes, the torsion arms or the wiring.
• Store axles on racks or dunnage, off the floor and under cover, with nothing resting on the hubs or brake wiring.

Check the axle against the order

Each axle is built to the numbers on your order. Confirm them against the label before the axle goes under a frame.

Orientation

• Crown up. A cambered spring axle is bowed slightly so that it straightens under load. Fit it with the bow upward. Fitted upside down, the tires wear on their inside edges.
• Label to the rear. The label on the beam or housing faces the back of the trailer.
• Left and right brakes. Brakes are handed. With the axle the right way round, the brake wiring or hydraulic fitting exits toward the rear and, on electric brakes, the magnet arm sweeps in the direction the drum turns going forward.
• Torsion arms trail. The arms point toward the rear of the trailer, with the spindle behind the housing.

Installing a spring axle

1. Locate and weld the hangers to the frame, square to the trailer centerline and at the spacing for the springs being used. Hangers on both sides must be directly opposite each other. Weld to the trailer manufacturer's frame specification.
2. Hang the springs. Fit the front eye in the front hanger and the rear eye in the shackle (double-eye springs) or rest the rear end in the slipper hanger. On tandems and triples, fit the equalizers between the axles.
3. Set the axle on the springs. The spring center bolt head sits in the hole in the spring seat. Overslung: springs sit on top of the axle. Underslung: springs sit beneath it.
4. Fit the U-bolts and tie plates. Run the nuts down evenly, a little at a time on each leg, so the plate pulls down flat. Torque to the table at the end of this guide.
5. Tighten the pivot bolts. Shoulder bolts are torqued. Bolts without a shoulder are run up snug so the spring eye, shackle and equalizer can still pivot, and are held with a locking nut.
6. Check clearance. With the trailer at its rated load there should be at least 3 in between the top of the tire and the frame or fender, and room for the shackles and equalizers to swing through their travel.

Installing a torsion axle

1. Prepare the frame. The frame rails must be flat, parallel and strong enough where the brackets land. A torsion axle puts its load into the frame over the length of the bracket, so reinforce thin-wall rails as your frame design requires.
2. Position the axle with the arms trailing and the label to the rear. Clamp the brackets to the rails and measure for squareness (see Alignment) before drilling.
3. Bolt the brackets to the frame through every hole provided, with Grade 5 or better bolts, hardened washers and locking nuts. Torque to the table at the end of this guide.
4. Check clearance. The arm swings up as load comes on. Leave room above the tire for full travel, and keep wiring, lines and frame members out of the arm's path.

Start angle

The start angle is the position of the arm with no load on it, and it sets the ride height. An arm that starts below level raises the trailer; one that starts above level lowers it. All the axles on a trailer should use the same start angle so they share the load.

Alignment

An axle that is not square to the trailer scrubs the tires and makes the trailer track to one side.

1. Measure from the center of the coupler or king pin to the same point on each end of the front axle, for example the center of each spindle. The two measurements should agree within 1/16 in.
2. On tandems and triples, measure between the axles at each side, spindle center to spindle center. The two sides should agree within 1/8 in.
3. Correct by moving the hangers or brackets before final welding or drilling, never by forcing the axle.

Electric brake wiring

• Each brake has two leads. One goes to the brake feed from the controller, the other to ground. Either lead can be used for either job.
• Size the brake circuit wire for the number of brakes and the length of the run (table below). Undersized wire starves the magnets and the brakes feel weak.
• Run a ground wire back to the trailer connector. Do not depend on the frame as the return path.
• Join wires with sealed crimp or soldered connections, and protect them with loom where they cross the axle or pass through steel.
• Leave enough slack at each brake for the suspension to travel, and clip the wire so it cannot touch a tire, a drum or a moving suspension part.
• Fit a breakaway switch and battery sized for the number of brakes, with the cable able to reach the tow vehicle.

Hydraulic brake plumbing

• Use steel brake line along the frame and a flexible hose from the frame to the axle, long enough for full suspension travel.
• Clip the lines so they cannot rub, and keep them away from exhaust and moving parts.
• Match the actuator's output pressure to the brakes. Maximum operating pressure: 750 psi for 7 in drum brakes, 1,000 psi for 10 in and larger drum brakes.
• Bleed the system from the wheel farthest from the actuator, then check every fitting for leaks under pressure.
• Free-backing brakes are handed. Confirm the left brake is on the left.

Wheels

• Use wheels with the bolt pattern, center bore, offset and load rating for the hub and the axle capacity. Zero-offset wheels keep the load centered between the bearings.
• Use the nut style the wheel was made for.
• Tighten in the crisscross sequence in three stages, and tell the customer to re-torque at 10, 25 and 50 miles.

Pre-delivery check

• Axle label matches the build sheet; crown up; label to the rear
• Alignment measured and inside tolerance
• U-bolts, bracket bolts and pivot bolts torqued or set, with locking nuts fitted
• Wheel nuts torqued in sequence
• Tire clearance checked at rated load
• Hubs turn freely with no end play you can feel; grease caps or oil caps fitted; oil at the level line
• Every brake applies and releases; current draw checked on electric brakes; no leaks on hydraulic brakes
• Breakaway system holds the trailer
• Wiring and lines clipped clear of tires, drums and moving parts
• Owner's Manual in the trailer

Torque reference