Clutch bolt inspection
Moderator: Paul Sehorne
Clutch bolt inspection
Has anyone seen this? Not on my ship but someone sent me these photos of the clutch bolts. I think I remember seeing a service letter/bulletin to actually inspect these thru the access hole in the top of the clutch. Can this be done satisfactorily? Looks like a botched start could cause this. Anyone have any comments feel free to speculate.
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Ron Spiker
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Re: Clutch bolt inspection
I haven't seen the bolt get damaged like that, but have seen the metal straps break. With the formsprag still connected to the clutch displayed, if you see the strap bolts off centered in their holes, it's probably a good idea to disassemble and check the straps. One or more is likely broken. Could be too fast of a startup or rolling on throttle too quickly during a power recovery at the end of an auto, among others. If you have the starter shut-off switch properly set to 10% of throttle and your brake works, the fast engine startup shouldn't be an issue.
Re: Clutch bolt inspection
For a botched start to have caused it, I can promise you the short verticle T/R drive shaft would have twisted into!!
The tensile strength of those "banjo" straps is so astronomical, the bolt shank would pull the holes into first.
My bet would be that the bolts were "rocking" back and forth and flexing the banjos thousands of times per minute, fatiguing the straps. They then snapped into and elongated the holes in the plate.
The clutch drum looks old. The plate and the banjos look new. I'll bet the parts were either installed wrong, or whoever installed them recently, forgot to tighten them. If the correct nuts (NOT Nylon Lockers) are used here, this is a pretty trouble-free area. I don't remember anyone having trouble at the rag coupling since 2000 when I got involved with Brantlys.
I don't have my books any more but if I remember right, the banjos go between the rag and the Formsprag, NOT between the plate and the rag!
Whoever was flying it could have had a bad day!
The tensile strength of those "banjo" straps is so astronomical, the bolt shank would pull the holes into first.
My bet would be that the bolts were "rocking" back and forth and flexing the banjos thousands of times per minute, fatiguing the straps. They then snapped into and elongated the holes in the plate.
The clutch drum looks old. The plate and the banjos look new. I'll bet the parts were either installed wrong, or whoever installed them recently, forgot to tighten them. If the correct nuts (NOT Nylon Lockers) are used here, this is a pretty trouble-free area. I don't remember anyone having trouble at the rag coupling since 2000 when I got involved with Brantlys.
I don't have my books any more but if I remember right, the banjos go between the rag and the Formsprag, NOT between the plate and the rag!
Whoever was flying it could have had a bad day!
YHO-3BR Pilots International
Re: Clutch bolt inspection
I believe the banjos do go between the "rag" coupling and the plate. You can see the top of the spragg clutch thru the greasing/inspection hole in the clutch dust cover and see that they are NOT visible. It's a good idea to put a wrench on the bolts to make sure they're not loose!