Keeps Snapping Off.

[tourerjim]

Help needed 600n to why the right hand boom support keeps snapping off on rear end 'alloy part' of the rod.
Gone through 3 in the last month seems to happen I think when doing piro's.
I've been flying with just the left one on to see if that one snaps but its fine very strange unless someone can help solve.

[moonmanflyer]

Sounds like it could be a vibration issue, check your torque tube to make sure the bearing hasn't moved on the shaft, thats quite common.

[daren]

As stated, normally vibration that snaps them off, could be fan/clutch balance

[tourerjim]

Checked TT bearing & centre of tube.

[tourerjim]

Just odered from Matt at Midland heli's he also mentioned knowing of this & seems to be happening on the 6 & 700's so he's sending me some different supports.
If the samething happens again then I will have to find a fault with the heli but I have gone through already with a fine tooth combe.

[barney]

It seems to be a resonance thing Jim , I popped 4 or 5 myself but none for about a year now. You can put a fibre washer between the end and mounting point to isolate them and help with alignment.

Brian

[SRH990]

The 700 tends to vibrate the bolts out of the boom clamp, as the ends are plastic they don't shear. I got around it by using some green locktite.

Since then I've also added a boom brace to the 700 and this seems to have helped the vibes too.

[tourerjim]

It seems to be a resonance thing Jim , I popped 4 or 5 myself but none for about a year now. You can put a fibre washer between the end and mounting point to isolate them and help with alignment.

Brian

Yep sounds good idea you have there also as Steve mentioned with his 700 bracing the supports so doing both will certainly cure the problem.

[barney]

On the 600 and 700 I would try to avoid a boom brace as the stays flex a fair amount and it will literally saw its way through the stays. More on the 700 in a mo.

The trouble with the 600 boom ends is they are bolted to both the frame and boom clamp at a slight angle which is pre-stressing the ends. Then add in the 600 generally have flexi 1.6mm frames that allows a fair bit of movement around the tank area when subjected to any collective and piro forces. So its constantly flexing the boom ends as the boom moves side to side.

Using the fibre washers will help with vibes and alignment but is only an improvement. QUK boom supports are beefier and cope better but make it more tail heavy. 2mm frames or better still G10 aftermarket frames flex considerably less. If you could source plastic ended stays that would be the best option.

OK Trexy 700 stays..again they flex but this seems to be mostly boom flex related.
The reason your stays are coming loose is the plastic ends compress after a short time under the washer. The bolt hole is also a little oversize allowing them to move a little in flight hence even loctited they work loose.

If you re-loctite them and torque them very firmy after they have settled they will stay put as the plastic end kinda moulds round the washer/frame/clamp. If you pull a stay thats been on a while you can clearly see where its compressed..
BTW you might as well remove the Allen screw little pins and replace them with something thicker (drill the hole to fit an old pushrod or similiar) Saves a lot of messing around later on. Dont ask how I know...LOL its happened on 3 occasions without a backup plan at the field.

Brian

[SRH990]

The boom brace I have is aluminium and made in 4 pieces, one top & bottom clamped around each boom stay and a bolt in a slotted hole in the middle. The brace is a larger ID than the brace's OD and I've put pads made of fuel tube inside so the stays and braces are isolated from each other, wear isn't a problem

[barney]

pads made of fuel tube

Your like me Steve and try to anticipate the little problems before they occur.