Pretty new to helis and both my 450s were purchased from others. In going over one of them, I noticed the head is not snug on the main shaft. It has a tiny (and I really mean minute) bit of wobble around the axis of the Jesus bolt. I checked that and it is snug.

So my question is... at what point do you replace this? As soon as it is not 100% snug, or what. Heli hovers fine and feels prety locked in. As a general comment, I can't believe that those tiny 2mm bolts are used to secure the head and the grips. That's a lot of force acting on those components.

I'm just hovering and figure 8s right now. No 3D and I would definitely replace before anything like that.

Originally Posted by TTRotary

Pretty new to helis and both my 450s were purchased from others. In going over one of them, I noticed the head is not snug on the main shaft. It has a tiny (and I really mean minute) bit of wobble around the axis of the Jesus bolt. I checked that and it is snug.

So my question is... at what point do you replace this? As soon as it is not 100% snug, or what. Heli hovers fine and feels prety locked in. As a general comment, I can't believe that those tiny 2mm bolts are used to secure the head and the grips. That's a lot of force acting on those components.

I'm just hovering and figure 8s right now. No 3D and I would definitely replace before anything like that.

I personally wouldn't fly with a head that isn't solid, that's just asking for trouble in my opinion.

Is this flybarred or flybarless?

And yeah, those little bolts do seem a bit small for the 50+ lbs of force pulling on them, don't they? Works just fine though, or people would have heads flying apart left and right with them.

-Ken

Flybarred.

Originally Posted by codepoet82

And yeah, those little bolts do seem a bit small for the 50+ lbs of force pulling on them, don't they?

Not really. The force is all linear. The force isn't trying to bend/snap the bolt in two. You could screw a good quality 2mm bolt into the ceiling and hang your entire body weight off it. Bounce up and down, too... It still wouldn't break/pull apart. That said, what people really have to worry about is properly using thread locking compound.

Originally Posted by RLundtz

Not really. The force is all linear. The force isn't trying to bend/snap the bolt in two. You could screw a good quality 2mm bolt into the ceiling and hang your entire body weight off it. Bounce up and down, too... It still wouldn't break/pull apart. That said, what people really have to worry about is properly using thread locking compound.

+1

If your noticing extra slop in the head , it might be time for a tear down , and rebuild .

Replace any parts that overly worn ( hardly ) , but generally just re-thread lock , and adjust play in components , to get a nice smooth and as slop free assembly as possible .. And you might be good for another 6 months or more ...

My first heli was flown so much , I had to do this ...

Butt ! Maintenance is part of the hobby dont forget .

Thanks, I'll just go ahead and replace with a new head block. It occurred to me yesterday that the more play it gets, the faster the wear will accelerate. Already tried the re-tightening route and it's not that.

The Jesus bolts actually are under shear and not just tension; I've pulled bolts with damaged threads and Z-shaped ones out of a head (and out of the tail drive gear too) on occasion. My guess would be that normally they're just holding the head to the shaft and friction is doing most of the work of turning the head, but if the bolt becomes slightly loose the head is free to move and the only thing turning it is the J-bolt.

From experience, if the head moves on the shaft with the J-bolt tight, you'll get vibration.

I had the same slop on my head
At first I wound a layer of tape on the main to prevent movement.
It worked but it bugged me and I was always checking it.
but
Very shortly after that I installed a Align DFC head and a ZYXs. It just was not cost effective replacing Align parts.
Why I went to Align DFC is the head came with a new main has a lot fewer parts and was a lot easier to setup (2 link adjustments)
I dropped about 100$
I guess you could go with HK DFC head for 15$ but the ZYXs will still set you back 56$
You see what I mean.
I just couldn't rebuild or replace parts for 15$

I see your point. However, in my case I have a fresh head that came with a "used" heli (it is new and partially built). The rest of that heli will become a MD500 scale conversion with fbl 5-blade main rotor, so I'll go ahead and replace.