I notice in your pic of broken parts that there is no friction ring present.
It goes between the dampener and dampener back plate.
You do have one right?
The quill shaft is driven from the back of the generator and the torque loading spike is dampened by the twist of the quill shaft and the dampener friction ring.
If you do not have the friction ring and it is metal to metal it will most likely snap as there is no dampening.
50 Amps isn't much. 1.6 HP?
I'm not sure I've ever seen a friction ring. We have 3 58s and none of them have friction rings that I know of. Do you have a picture of one?
I must say I have never heard of a shaft shearing and no gen warning, My first thought would be shearing on start, rubbing compressor???
Hope this help.
It was strange for sure. It sheared at about a 45 degree angle and it was able to still drive itself.
In addition to all of the very relevant and detailed replies above, I'd like to add the following:
1. You said "...We tend to buy a handful of shafts when we run low". Where do you buy them from? Are they genuine Lear Siegler parts or PMA items? Do they come with the correct paper-work?
2. Do you use external power (GPU) for engine start, particularly the first start of the day? If you do and it's not by using a bank of large batteries what is the starting current limiter set to? If the limiter is set too high it will result in excessive 'wrenching' torque when you initially press the starter. GPU's with a 'soft-start' function whereby there is a quick but gradual build-up of starting current when the starter is pressed are ideal.
I'm not sure of the brand of shaft. We purchased them from Duncan Aviation. Unsure about the paperwork. I'd have to ask our mechanic about that.
We don't use a GPU very often. A few times a year maybe. Normally we start off the aircraft battery. When we do use a GPU is just a battery cart with a couple of 12v batteries wired in series.
are you running a Ni Cad, and waiting a min for it to take the charge? or a passable Gill (yuch) or Concorde battery? I havent seen a sheared shaft in decades, is it on the same starter? same repair shop ?I've seen back yard overalls, with the nut have tightened..
We have a mix of Concordes and Gills. We are phasing out the Gills. In fact we just got rid of the last one. Complete crap. We tend to blow at least one shaft every season. The first two were on the same generator, then we swapped generators and it popped again. Same mechanic. He worked on 58s in the army for quite a long time. He is local. We don't have a repair shop so to speak, we are a small ag outfit.