Originally Posted by 1Pilgrim

I lied - the "new" main shaft was cracked at the top. I may have overtightened the rotor hub retainer screw when I put it together the first time. After allowing a drop of ca to seep into the crack (taking care to blot off the excess and let it cure) I put the heli back together.

Et voila! No tbe. All is well with the world !

EDIT: Before attaching all the other "goodies" I pushed the main gear onto the shaft, fastened it with the retainer screw, ran the shaft up into the frame and gave it a spin. Huh. The shaft came to a stop with the head of the retainer screw pointing straight down.

After a few more trials I could see that the screw definitely threw the shaft out of balance so I tossed it - the main gear is keyed onto the shaft and is a very secure press fit so imho the screw is redundant. The shaft spins true without it, so we shall see what we shall see...

Way to keep after it Pilgrim, mighty good job. I wouldn't hesitate to get in a heli with you!

BD

A quick question about the canopy grommets:

Is there an easy way of getting them fixed onto the canopy or is it purely a juggling activity until it pops in?

I find the little devils very fiddly to get into place without dropping/losing them!!!

Originally Posted by iancraig10

A quick question about the canopy grommets:

Is there an easy way of getting them fixed onto the canopy or is it purely a juggling activity until it pops in?

I find the little devils very fiddly to get into place without dropping/losing them!!!

I start one side in, and then use a toothpick to "poke" the remaining side in.

BD

@Pilgrim I attempted to fix a main CF shaft to no avail using Gorilla Glue. I let it set for about 48 hours and it quickly split with an easy stress test. I wonder if a different type of CA would hold better? But, then again, you'd only have to break it down again if it didn't hold. Anyway, glad you got it sorted out...way to go

Mike.

Originally Posted by iancraig10

A quick question about the canopy grommets:

Is there an easy way of getting them fixed onto the canopy or is it purely a juggling activity until it pops in?

I find the little devils very fiddly to get into place without dropping/losing them!!!

I use a little bit of spit..slides right in....

Thanks BD and Jake. There was me thinking there's some really smart way to get the grommets in .......

I even tried collapsing it and poking it in and then trying to turn it. One of them decided to flip off so I thought, 'it's got to be easier than this!!'.

Originally Posted by Chap1012

@Pilgrim I attempted to fix a main CF shaft to no avail using Gorilla Glue. I let it set for about 48 hours and it quickly split with an easy stress test. I wonder if a different type of CA would hold better? But, then again, you'd only have to break it down again if it didn't hold. Anyway, glad you got it sorted out...way to go

Mike.

According to Wiki, Gorilla Glue is a polyurethane used primarily for bonding flat, smooth surfaces; when exposed to moisture it reacts and creates a foaming action that fills voids as it cures. The expanded glue contains entrapped air bubbles so I'm not sure how well it would work on the type of crack I'm seeing in the main shaft. Also, isn't it pretty thick?

CA stands for cyanoacrylate, a completely different kind of adhesive. I'm actually not sure whether ca bonds that well to cf - I've read that epoxy is the adhesive of choice for cf - but I was looking for something that would flow into the crack in my main shaft and then cure without expanding or shrinking.

I won't know how well it works until I can fly outside which unfortunately won't be today.

CA is an excellent choice to bond cf.

The cracks in all my shafts seemed to be parallel to the hole where the rotor hub screw goes through, i.e. the cracks may propagate from the hole upward rather than from the top down.

If we have a pretty good idea where the crack starts, I wonder whether there is a way to prevent the shaft from cracking rather than trying to fix the crack after the fact.

Originally Posted by iancraig10

...
I even tried collapsing it and poking it in and then trying to turn it. ..

That's always worked for me.

Originally Posted by 1Pilgrim

The cracks in all my shafts seemed to be parallel to the hole where the rotor hub screw goes through, i.e. the cracks may propagate from the hole upward rather than from the top down.

If we have a pretty good idea where the crack starts, I wonder whether there is a way to prevent the shaft from cracking rather than trying to fix the crack after the fact.

Just buy a new one or two.

There is a dude selling solid main shafts on ebay. I would not recommend them. The one I bought split after 4 flights and I did not have a blade strike.

Originally Posted by 1Pilgrim

The cracks in all my shafts seemed to be parallel to the hole where the rotor hub screw goes through, i.e. the cracks may propagate from the hole upward rather than from the top down.

If we have a pretty good idea where the crack starts, I wonder whether there is a way to prevent the shaft from cracking rather than trying to fix the crack after the fact.

I have seen some shafts that the holes were NOT drilled in the center. The hole in the head was centered so when you put the screw in it causes a lot of stress to shaft on one side of the hole and can and will crack the shaft. If you get a new shaft or remove the old one look closely at the holes and you will see that not all of them are centered as well as they should be. Also, if it cracks it will most likely be from the hole toward the end of the shaft, or upward as Pilgrim stated.WS

[QUOTE=1Pilgrim;

If we have a pretty good idea where the crack starts, I wonder whether there is a way to prevent the shaft from cracking rather than trying to fix the crack after the fact.[/QUOTE]

You could use a syringe and fill the hollow CF rod with epoxy and then clean out the screw/bolt holes. It would make it alot stronger and help to prevent cracks.WS

Well Black had already reported that solid CF is not the way to go. But, the hollow filled with expoxy as WS suggests. Interesting. I see the stock CF main shafts are back in stock at Helidirect

Mike.