Align Engineering

[Gixxer]

I purchased some Align spares for a 700 DFC head and noticed, what I would consider, extremely dodgy engineering.








When those M3x6 bolts are inserted through the blade grip arms, I measured 2.5mm of thread protruding through the mating surface, which would be an effective thread length of about 2.2mm. Does anyone have one they can measure, as this seems way too little?

I did some calculations, and unless I'm mistaken, for a 10.6 steel bolt threaded into 6061 aluminium, the length of thread engagement, in a normal situation, should be around 4.5mm, and with the stresses and vibrations these joints are subjected to, I wouldn't use less than 2x the nominal diameter of the bolt, which would be 6mm in this case... but 2.5mm is way too short.

[HeliMonkey]

if they were longer would they not foul the outer case of the blade grip bearing? not saying that is an excuse for poor engineering but it may be a reason?

[Gixxer]

I've replaced the 6mm bolts with 8mm bolts and had no problems with them bottoming out. I've not tried anything longer.

[ghost2212]

While it might not seem right I've seen no problem with these bolts snapping Even in some pretty hard smashes that bent the top hub etc. Isn't there another locating pin on the blade grip?

[Geek]

Doesn't the arm go into a slot?
To help take the load.

It's almost 1 diameter.

[Gixxer]

The arm does fit into a slot but the linkage is connected about 20mm out from that.

It's the stripping force of the internal thread I'd be worried about.

[pgkevet]

2.2mm sounds too short. I don't have the engineer math to work it out but note than many brand heli frame bolts are 6mm through 2mm frame under a washer..so again about 3mm of thread into spaces/bearing holders etc. Yes, do realise not the ame forces/vibes there. Does threadlock affect the calcs and that there are twin bolts? Has anyone heard of a failure here?

[Chris Boughton]

Yes the stock bolts are way to short and as a result with prolonged use of these bolts we have seen many failures in flight resulting in the heli tearing itself apart!!! I have replaced mine with 8mm bolts they do not hit the radial bearings and will give a great peace of mind from these shearing!!! I highly recommend everyone to change these bolts!!!

[Chris Boughton]

I have seen 2 failures at charmouth

[pgkevet]

Bolt change today then.

[Chris Boughton]

Bolt change today then.

Jus make sure the bolts you decide on using don't foul on the radial bearing then all should be fine

[Geek]

I have seen 2 failures at charmouth

I saw helis crash first then bolts shear.
And that must of been all the crashes at this last Charmouth.

If 8mm fit why the hell didn't Align do it.
Nightmare

[Chris Boughton]

I saw helis crash first then bolts shear.
And that must of been all the crashes at this last Charmouth.

If 8mm fit why the hell didn't Align do it.
Nightmare

There was connor sloan at the last charmouth took of he rolled the heli and it jus self distruct and then there was alex hawtin at spring charmouth the video says it all!! I guess align jus didn't pay enough attention to this!!

[pgkevet]

I saw helis crash first then bolts shear.
And that must of been all the crashes at this last Charmouth.

If 8mm fit why the hell didn't Align do it.
Nightmare

"Here big bag six bol'."
"Six bol' too shor'. Nee' ate or bwake."
"Ah, so betta - sell mo' spair!"

[pgkevet]

There was connor sloan at the last charmouth took of he rolled the heli and it jus self distruct and then there was alex hawtin at spring charmouth the video says it all!! I guess align jus didn't pay enough attention to this!!

I find it difficult to analyse a crash from some of these vids. Clearly the tail box comes off..whether boom struck or not. A couple of frames earlier the boom stays appear to flex but whether that is a dual strike or first signs of the tail box failing is arguable. I don't see this as primarily the grips whch you could expect to fail secondarily to any of the above.