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Bolt Engagment Legnth Question: Sensenich Prop

PhatRV

Well Known Member
I have the Sensenich ground adjustable composite prop for my RV8. Everything was purchased through Vans.

I trial fitted the propeller to my engine this weekend but I discovered that the supplied bolts did not protrude past the crankshaft propeller flange of the IO-360-M1B engine. The bolts came up slightly less than 1/4" short of the propeller flange bolt holes. Subsequent measurements verified that the bolts were less than 1/4" short when all the parts are stacked together.

I called Sensenich tech support and he said the bolt engagement depth is okay if it is at least the same as the bolt diameter. The bolts in question are 1/2 inch in diameter. From the installation, the bolt engagement depth is over 2 times the bolt diameter. Sensenich tech support indicated that the later version of Lycoming 360 engines have thicker propeller flange than the older models. I have to take his word for now.

Question 1: For those who has this propeller, do you have the same problems as described above? The question is also applicable for the carbureted O-360-A1A engine or other Lycoming engines too.

Question 2: for the DAR and A/P: is there a documentation of the valid bolt engagement depth specification that can be publicly accessed by the regular public? I would like to verify the acceptable propeller bolt engagement length.

Question 3: For those who used the stock IO-360-M1B or O-360-A1A with the Sensenich ground adjustable composite propeller, if you used the kit hardware, including the bolts from the kit, have you experienced anything out of the ordinary?


Thanks for your time.
 
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The OEM releases supersede bulletins, advisories, etc. That said, I'd ask for a copy of the installation instructions, drawing, whatever, for CYA.

There is no standard requirement for thread protrusion from any such (essentially a) blind hole, There is generally a requirement to one full thread (excludes chamfer/thread relief) past any locking feature which most QA inspectors count as full protrusion for ease of inspection. The materials matter but generally, for steel - steel thread engagement, one full male diameter is *plenty*; nearly all of the load picked up in the first coupe of threads. Steel into something softer like AL, the ROT is two full D engagement.

Realized torque here is very important. Follow the OEM instructions. If they don't spec cross torqueing in stages (50%, 75, 90, full), I'd still probably do that. It cannot hurt/only help.
 
The OEM releases supersede bulletins, advisories, etc. That said, I'd ask for a copy of the installation instructions, drawing, whatever, for CYA.

There is no standard requirement for thread protrusion from any such (essentially a) blind hole, There is generally a requirement to one full thread (excludes chamfer/thread relief) past any locking feature which most QA inspectors count as full protrusion for ease of inspection. The materials matter but generally, for steel - steel thread engagement, one full male diameter is *plenty*; nearly all of the load picked up in the first coupe of threads. Steel into something softer like AL, the ROT is two full D engagement.

Realized torque here is very important. Follow the OEM instructions. If they don't spec cross torqueing in stages (50%, 75, 90, full), I'd still probably do that. It cannot hurt/only help.

The Sensenich prop came with a very detailed set of installation instructions. I used its recommended torque schedule at 50%, 75%, and 100%, and with instructions to cross-torque the bolts. I thought the instructions are very thorough. At the end of the installation, someone in the peanut gallery pointed out I should check the back propeller flange using the inspection mirror.

Good to know about the steel-steel thread engagement. Thanks.
 
If you still care, I looked at the AN345 spec for plain steel nuts, no locking feature, etc.. The thicknesses (heights) typically range 70 -80% of the nominal diameter. A LOT of testing has gone into AN/NAS/MS hardware including what design margins are available, fault tolerance from incorrect installation, all while considering the associated weight.

Anyway, a little more indirect evidence to back-up the ROT comments about 1D engagement. You followed the OEM instructions so I wouldn't give it another thought unless they tell you to recheck the associated torque after xxx hours.
 
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