Problem of a Gear

Problem & Solution

1 ) Noisy gear trains

Noisy gear trains have been a common problem for gear designers for a long time. And the demands for smaller gearboxes transmitting more power at higher speed and greater efficiency continue. Some popular solutions to the noisy gear problem include enlarging the pinion to reduce undercut, using Phenolic, Delrin or other noise-absorbing products where possible, or changing to a helical gear train. Other methods include tightening specifications to insure greater gear quality or redesigning the acoustical absorption characteristics of the gearbox. 

Occasionally, experimentation with gear ratios can limit harmonic frequency amplification, which otherwise can cause a gearbox to amplify noise like a finely tuned stereo system. You can also study material and hardness requirements so that modifications may minimize heat treatment distortion or possibly eliminate the need for heat treatment entirely.

Also, pay particular attention to gear geometry to insure maximum contact. 

Another approach to the gear noise problem that yields good results is crowning or barreling of the teeth. This technique involves changing the chordal thickness of the tooth along its axis. This modification eliminates end bearing by offering a contact bearing in the center of the gear.

Another benefit of crowning is the reduction of misalignment problems caused by inaccurate machining of the casting, housing, shafting, gearboxes or bearing journals. Crowning can also reduce lead problems in the gears themselves, which causes the gears to wear unevenly and bind because of eccentricities and position errors. Obviously, a gear with a center contact is less affected by discrepant manufacturing or design; furthermore, you can reduce the backlash requirements and allow the gears to wear in rather than wear out.

2 ) Steering Gear Problem


Recently Adam removed a steering gear from Dave Bemis 64 Thunderbird as it was pouring fluid out of the uper steering shaft seal justbelow the coupler, or rag joint in the steering column. The unit was leaking so badly, the vehicle had to be towed. The downer is that he paid a shop in Manchester N.H. somewhere in the neighbourhood of $700.00 to do the job. Naturally, he wasn't happy about that, and I don't blame him.

 Upon close inspection, he found that the upper steering shaft seal had popped right out of the bore and was just flapping in the breeze. The steering gear, although heavy, was not hard to remove as the engine and transmission had been removed from the car. Once on the bench, the gear was completely disassembled. he found that the gear assembly had never been rebuilt as all the original bearings and bushings were original Ford Units. The gear was found to be in good shape exceptfor thr seals , so the gear was resealed and then the customer was charged for a complete rebuild! It happens all time.

  Upon further inspection , he found that the snap ring that holds that seal in place was never installed which is why the seal poped out. The steering gear was reassembledand a new snap ring and seal was installed at the upper steering shaft. The unit was then refinished in a natural cast colour , and now awaits reinstallation in the car . Although this particular unit was removed from a Thunderbird, the repair process and the circumstances surrounding it pertain to all classic car!

3) Gear Failure

Tooth Interior Fatigue Fracture, (TIFF), is a type of gear failure. The failure is characterized by a fracture at approximately mid-height on the tooth of the gear. This distinguishes it from a tooth root fatigue failure. The crack for a TIFF is initiated in the interior of the tooth. This distinguishes TIFF from other fatigue failures of gears