Witch is stronger?

[coolice]

Hey.

Bear in mind also that how said bolt had been made plays a big part in how strong it is, for instance a rolled thread will be weaker than a machined one incorporating nice radius's in any corners over plain 90 degree corners.

If think its fair to say this topic has spawned from Aligns recent blade hold bolt upgrade and the new screw is being machined, so combined with the better material will be much better.
The other plus is the fact a portion of the plain shank will be taking side loads and not the area of a bolt where the threaded part meets the plain section.
.

[ChrisB]

But if this new bolt is loose as per the original reason for upgrade,won't it still snap.

[bolders]

But if this new bolt is loose as per the original reason for upgrade,won't it still snap.

I dont think the bolt being loose is the real reason for the bolt to snap in the first place - unless it results in greater loading on the bolt which as far as I can tell it doesn't. It probably failed simply because there was a large bending moment at the intersection between the bolt and the part it screws into.

The updated design reflects this too imo if you look at what has been done. A thread has stress raisers at the sharpest points which have now been moved away from where the highest bending moment (point of highest stress). Furthermore, by moving the thread inboard there is a gain in cross sectional area at the point with the highest bending moment (approx 30% gain in c.s.a at a guess) which also reduces the stress in this section as Stress = Force/Area

[Grant_beltcp]

The only snag is that for Align to do a recall it means there's a fairly major issue with stress being out on that bolt. This fix will only be putting a stronger joint in place to mask the issue rather than cure the problem that's actually causing the stress such as having no flex in the links.

[dillwhacker]

I always thought that Jesus bolts should be the toughest grade steel possible, until someone suggested that it is better if they shear in a crash rather than transferring all the force to the rest of the drive train.
Made me think.

[scallybert]

I always thought that Jesus bolts should be the toughest grade steel possible, until someone suggested that it is better if they shear in a crash rather than transferring all the force to the rest of the drive train.
Made me think.

It makes you think, but I reckon I'd rather have a main gear strip in a crash; than have a jesus bolt fail in flight, and cause a crash.

[Grant_beltcp]

Most feathering shaft bolts are good bolts and quite a large thread size for the shaft the go in.
I would rather a 90 sized blade stayed attatched when a hit the floor.
Also, in a crash 90% of the loading is bending the shaft rather than pulling the blade out so I think it would be very difficult to get the strength and size of the bolt enough so that it's safe in the air and beaks with impact.
Ideally the feathering shaft wants to be soft and bend on impact saving other pars, but if it's too bent you will never get it back out again, and can cause further damage to was block and grips.
It's a carefully balance that each manufacturer does differently. I would make titanium feathering shafts as they're lighter and also where a steel shaft would have a small bent the titanium would probably flex back.

[Grant_beltcp]

Sorry about the awefull spelling - my iPhone auto correct is utter useless!

[d a baker]

A rolled thread is stronger than a cut thread.
Bolts need to be in tension to attain maximum strength.
Loose bolts are considerably weaker.

[dillwhacker]

Been there, done that with a 450 - very little damage TBH, but it did only flop down onto its skids from a fifteen foot hover.
Reckon the Jesus bolt was weakened by the previous crash.
Thats why I'm surprised you can't buy Jesus bolts in a packet from Align - you can only get them in a bag with new gears or a new head...

It makes you think, but I reckon I'd rather have a main gear strip in a crash; than have a jesus bolt fail in flight, and cause a crash.

[scallybert]

Been there, done that with a 450 - very little damage TBH, but it did only flop down onto its skids from a fifteen foot hover.

I think it will depend a lot on what you were doing at the time...

[dani_r]

Been there, done that with a 450 - very little damage TBH, but it did only flop down onto its skids from a fifteen foot hover.
Reckon the Jesus bolt was weakened by the previous crash.
Thats why I'm surprised you can't buy Jesus bolts in a packet from Align - you can only get them in a bag with new gears or a new head...

They really need to start selling servo horns screws, Jesus bolts and blade grip screws in bags! Would save so much messing around if one goes AWOL!

[bolders]

A rolled thread is stronger than a cut thread.
Bolts need to be in tension to attain maximum strength.
Loose bolts are considerably weaker.

I dont think the bolt being loose is the real reason for the bolt to snap in the first place - unless it results in greater loading on the bolt which as far as I can tell it doesn't. It probably failed simply because there was a large bending moment at the intersection between the bolt and the part it screws into.

Yes I missed a glaringly obvious point here the loading on a loose bolt will be greater. A correctly torqued bolt will ensure some of the loading is carried by the friction faces - sorry about that had not had my coffee yet lol.

However, im sure you didn't mean it in this way but the statement that a "loose bolt is weaker" is a bit misleading. The material properties of a loose bolt are no different than a torqued bolt thus its strength is the same. It might be better to say a correctly torqued bolted provides a stronger joint than a loose bolt

[Grant_beltcp]

Machines threads are actually significantly weaker than rolled threads. Machines threads cut away all the material to make the thread, which also leaves machining marks and areas for stress fractures to occure.
Rolled threads use extra force to push in that extra material which ends up with a smoother, harder worked surface.

Also a turned bolt is the same, it leaves alot of chance for tiny machining marks to cause stress points, particularly where bending moments and fatigue are involved. A forged, work hardened bolt with rolled thread is my friend

Hey.

Bear in mind also that how said bolt had been made plays a big part in how strong it is, for instance a rolled thread will be weaker than a machined one incorporating nice radius's in any corners over plain 90 degree corners.

If think its fair to say this topic has spawned from Aligns recent blade hold bolt upgrade and the new screw is being machined, so combined with the better material will be much better.
The other plus is the fact a portion of the plain shank will be taking side loads and not the area of a bolt where the threaded part meets the plain section.
.

[d a baker]

(However, im sure you didn't mean it in this way but the statement that a "loose bolt is weaker" is a bit misleading. The material properties of a loose bolt are no different than a torqued bolt thus its strength is the same. It might be better to say a correctly torqued bolted provides a stronger joint than a loose bolt ) yes quite right bolders.