The older style Part No : 1757-10-451B retail $12.05 and the 2nd gen Part No : N350-10-E51B are $22.74. Are the 2nd gen style really worth almost twice as much $$? They have some rolled rib in the middle that is supposed to dampen vibration but that doesn't really work.

This guy used them in his airplane and broke one tension bolt
http://www.rotaryaviation.com/Squawk_Tension_bolts.htm

And do you think using heat shrink tubing on the middle of the bolt would be a good ideaer? I'm thinking of buying the older bolts and heat shrink wrapping them. Do you think it'll survive the hot coolant?

 

I can't imagine anyone would put a rotary engine into an airplane and NOT fabricate a broken bolt retention plate, to keep sheared bolts from backing out, encountering the counterweight, and stalling the damn engine, or worse.

The fact that the guy in the story was able to back the broken bolt out just by pressing the broken end back against the threaded part suggests to me that somebody didn't properly torque their tension bolts. Final torque on a tension bolt is on the order of 25-30 ft-lb IIRC. Unlikely he would have been able to apply that much torque to the broken part just based on irregularities in the broken face.

Regular heat shrink tubing is normally irradiated polyolefin; max. working temp is around 155 deg Celsius. Other types like polyester are available with higher working temps, but are harder to find.

 

i think either solution is fine. i like the 89+ bolts, but putting some kind of damping in the middle of the old style ones seems to work just as well.

i did the RB silicon the bolt thing. its not too messy going together.

 

Ordered the S5 tension bolts.

 

It is quite probable that he was able to back out the bolt end that easily. Torque is a measure of tension placed on the threads. Once that tension is released the only thing holding it in there is friction between the threads, thread sealer or corrosion. I wouldn't believe this either but something similar happened to me.

I was replacing the timing chain on my 87 Riviera and and couldn't break the crankshaft bolt loose that held the timing pulley. The bolt snapped in half. This bolt is similar in size to our e-shaft bolt. Called a mechanic friend for advice, expecting him to tell me to drill and use an easy out. He said the tension was gone and I should be able to take it out with my fingers. I thought he was nuts but it was that simple.