Xenon

[stevenoc]

Hi Greg.
Scary findings especially as you have given me time on her. About the old (red) main cut out switch. Back in 80's when I was involved in rallying, We used to install them right at the battery (shortest +cable length) . We then took a cable attached to key into the cabin and had a pull lever located easily reached by both people to kill power in event of prang. Some ppl even had a second cable to the outside, marked for the same reason.
Just an idea.
Would like to visit your workshop sometime.
Thread is great

Steven

[gyropilot]

That "neck" is a helluva lot thinner than the rest of the bolt and must compromise its strength no? So is there reason why the factory didn't cut a regular thread into the bolt and just use a bigger lock-nut? (As per the MTO teeter bolt example you show)

I'm enjoying following your rebuild Greg - thanks for sharing this with us.

Thanks Dave
Without protracted explanations on the calculations surrounding circles one needs to consider the distance around a circle is called its circumference. The distance across a circle through its center is called its diameter. Now the strength of the shaft is calculated in its area (think contact point on a rotating friction plate of the car clutch) The area of a circle is the number of square units inside that circle, calculated with the standard formula (the Standard 2 maths I refer too)
So some logic in your comment indeed considering the contact point where the RH assembly and teeter hinge contact the stationary mast construction, in this case both appear to be 8mm, the end stop (nut & bolt) is in fact only to prohibit the bolt coming out during rotation and offers no mechanical integrity, it does give us as Pilots of these craft comfort during a pre flight
In fact if we accept my lose description of area and its strength we would have to agree that the bolt could be exponentially stronger if we then drilled a hole directly through its length? because then you have increased is area, and that is in fact how the bolts in TC Helicopters are manufactured offering superior strength and reduced weight.

The Teeter bolt in the case of the Xenon is what is referred to as a precision bolt and its manufacture process is different from the extruded bolt seen in the MTO, possibly as gyro technology has evolved in the last few years with the MTO bolt seen above for a 2016 MTO versus say the Xenon that was conceived during 2007 the engineers have learnt that despite the RH bearing and teeter assembly holding us up in the air during flight these components in engineering terms really do not work that hard.

Without boring anyone to tears a further example that is easy to understand is the bolts holding the decorative engine covers onto a motor, are extruded, the one holding the cups that clamp the conrods to the crankshaft are precision engineered and hardened, as you can appreciate the forces they need to absorb during the up and down motion of the piston and crank rotation ...then consider that on every rotation of the engine that piston. conrod assembly actually stops momentarily as the piston hits TDC and its direction is reversed.

Scary stuff this engineering

we know them as "shoulder bolts" and are common in my industry - precision ground along the shank and the lengths are matched, so if you order 10 of - dia10 x 100mm it's guaranteed to be dia10.000 x 100.000mm long - call me next time you need one!

the thread on the end, in this application, is only there to stop it from sliding out due to rotational forces. we use them on our 35 - 1000 ton injection machines to limit the ejector plate movements, and that thread can take a beating before it's snaps off!


for those that want to read more on the fascinating world of bolts & screws

http://www.unbrako.com/docs/engguide.pdf

[greg vos]

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[Learjet]

Ha! Thanks for the bolt explanation Greg & Jacques. I'm learning something new on every page of this thread.

[greg vos]

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[Vertical Tango]

Greg, remember that you do all this hard work only for yourself. When you are going to take someone up and hope to brag about your workmanship, it will pass way over his head and he won't even appreciate all your efforts. In the end, seeing the threads of your switch will not give a nervous breakdown to your pax. Even when you think it is all done, you can start a new re-strip, criticise everything again, and start a new rebuild session, just for fun !

[greg vos]

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[gyropilot]

Greg, remember that you do all this hard work only for yourself. When you are going to take someone up and hope to brag about your workmanship, it will pass way over his head and he won't even appreciate all your efforts. In the end, seeing the threads of your switch will not give a nervous breakdown to your pax. Even when you think it is all done, you can start a new re-strip, criticise everything again, and start a new rebuild session, just for fun !

he's not just doing it for himself - he's doing it for us as well - so he better take his time and get it right the first time otherwise he will do it again

but seriously he's the only person I'd trust with a task like this, since our lives depend on it and given Greg's OCD attention to detail and the fact that he takes pride in his work, he is well suited for the task!

[Vertical Tango]

Hi Gregg,
I did not intend hurting your feelings with the word "brag". To the contrary, we all brag about what we do (only when it is a success !) and I am one of those.
Great pity that those who pm you do not share their experience with others. Keep the good work !

[greg vos]

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[gyropilot]

Over head panel looks good!

[Vertical Tango]

Greg, here are the mast attachments that I have done. Please note the spacers.
https://drive.google.com/open?id=0B6-Z_ ... nRCRmVjWmM
https://drive.google.com/open?id=0B6-Z_ ... W4zdWtLcVk

[greg vos]

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[gyropilot]

Things and techniques that we need to hand down form generation to generation but if the very people today who are responsible for training our artisan's have no pride we will see a decline in workmanship and something I have seen with many AP's who work on gyro copters.

too late there I'm afraid - today's "educated" artisans can barely clock up a vise! - they lack the basics - but yet expect top wages cause they have a certificate! and as far as pride goes - well they can barely spell that word - they just there to collect their wages at the end of the month!

[Vertical Tango]

Hi Greg,
The 3rd bolt in pic 2 was called for in the original drawing that I have and I did not even questioned that. The Polish removed it as your machine was not built in France but in Poland by Artur and Cellier. They thought that this was an improvement very much in the same line than your thoughts. I will not dispute that.
Yes, I agree that cosmetically, the cables should have gone through a rubber boot, and I did that at many places that I thought were necessary due to differences of movement between the cables and the material they go through. In this case, due to no movement, I deliberately omitted that.
My attitude to the project was not cosmetics within reasons but more practical. It took me 2.5 years to complete it as most fittings and accessories were missing from the kit . When you need a grommet, it is another 2 hours to get it and everything adds up in time. If I can do without, I also save weight as we know that Xenons tend to be heavier than the rest. I accept your remark.