The 340 Prop failure thread
Posted: 21 Dec 2012 12:17 am
There has been a number of failed props recently and some of them have even taken out the bellhousing. With the declining numbers of 340's out there I don't think we can afford these breakages.
Now I am certain that the bulk of failure we have seen recently are due to misalignment of the engine/gearbox. This is most likely due to saggy mounts either on the engine or beabox. The other possible is rusted out gearbox support brackets and does need to be considered.
I've made a start on a laser alignment tool for setting up PU engine mounts (thank Chris C for the details on how you made yours) and will be competing it over the holidays. I'm going to make a couple and offer them out on loan. What I did notice with the dead doner prop is that the one end that had failed with the rubber had ripped apart is that the other end was displaying signs of breaking up. The failed end was the engine end.
Years gone by the more common issue was with either the splines shreading or the bond between the rubber cusion part and the alloy tube giving out. The rubbber shreading was quite rare back then.
I'm interested in everyones experiance of failed props we can come up with a long term solution.
Here are some photos of the donor prop of teh end that has signs of slight cracking
Now I am certain that the bulk of failure we have seen recently are due to misalignment of the engine/gearbox. This is most likely due to saggy mounts either on the engine or beabox. The other possible is rusted out gearbox support brackets and does need to be considered.
I've made a start on a laser alignment tool for setting up PU engine mounts (thank Chris C for the details on how you made yours) and will be competing it over the holidays. I'm going to make a couple and offer them out on loan. What I did notice with the dead doner prop is that the one end that had failed with the rubber had ripped apart is that the other end was displaying signs of breaking up. The failed end was the engine end.
Years gone by the more common issue was with either the splines shreading or the bond between the rubber cusion part and the alloy tube giving out. The rubbber shreading was quite rare back then.
I'm interested in everyones experiance of failed props we can come up with a long term solution.
Here are some photos of the donor prop of teh end that has signs of slight cracking