Autorotation hub needs shim?

[J-B0t]

Hey folks,

Just got my 7HV this week. During assembly I noticed that my Autorotation hub has some play in it. The main gear can slide up and down on the Sleeve, about .5mm or the thickness of a fingernail. I noticed because it has an audible click when it slides up and down.

https://lh3.googleusercontent.com/-P8kL6leWuWA/Ts3GAuhLpWI/AAAAAAAABk8/tA6OR-YVUaE/s640/7hv%252520maingear%252520hub.jpg

When the gearhub is in place on the main-shaft with the belt on main pulley, this tiny slop on the sleeve brings the main gear very close to the belt. This doesn't seem right that it should have any play at all. Should it be shimmed between the pullyhub and the autorotation oneway bearing hub? Did I not get the shim?
I was wondering if anyone else has noticed this.

Thanks
-J-B0t

[Rob43]

I've not seen this sort of axial play in my assembly. Only thing I can think of is if, for some reason, that your pulley is not pushed up against the gear hub when the two set screws are tightened against the one way drive sleeve, which, in turn, fixes the gear and pulley together. The sleeve has flats 180 degrees apart, and are 90 degrees from the Jesus bolt holes. With the set screws in place, in the proper position, and with the Jesus bolt through the shaft and gear hub, there should be no such play. There are no shims in this assembly. It is a very snig assembly as it is. Do not overtighten the two set screws against the one way drive sleeve to avoid causing distortion. It's very robust, so it shouldn't be a problem.

The belt operates VERY close to the bottom of the main gear. No more than 1mm on mine.

Let us know if this does not clarify or help.

[J-B0t]

Hey folks,

thanks for the reply Rob43

I did check the alignment of the pulley hub, and the set screws, took it all apart, and re seated everything. As it turns out, the bottom Jesus-Bolt needs to be in to get correct alignment of the set screws and vice-versa. So I can get the slop out of the sleeve by adjusting the setscrews on the pully hub, but then the Jesus-Bolt won't lineup.

I also noticed that sometimes the Gap or slop in the sleeve is not noticeable because the bearing that sits on top of the oneway bearing will shift up and make it appear to be tight.

Should the bearings be loose? I figured it would be locktited in place. I only own 3 machines, and with my limited experience the main-gear and auto hub should have no slop or play.

Still wondering if anyone else has this on their Hub, perhaps it wen't unnoticed, as I mentioned I didn't notice it Visually I heard the click and then looked into it.

Thanks
-J-B0t

[snipealot]

Do you hear a clicking sound when rotating the autorotation gear? When spooling down I hear a clicking sound on every revolution and also by manually rotating the blades.

[J-B0t]

Hey Folks,

Snipealot, Mine is still on the bench, so I haven't gotten to maiden it yet. I can't say how it will sound under load, but I can share this, A guy at my flight field with His 7HV has/had the same clicking when spooling down, or when hand spinning the head, same location mysterious sound somewhere around the Hub. He tightened the collar for the main-shaft and it seemed to help...

But now I'm thinking that maybe it might be related. If my main-gear is at the top of the sleeve and I spin the head it clicks once back into the down position, maybe in your case the pinion is pushing it back up. IDK, but in my case, if I hold the air-frame and then slide the main gear and hub up and down it will make a slight click or pop. Try it out let me know if yours moves at all. I can only imagine what that might sound like at 2100rpm. That is why I want to see if other folks have this issue.

Thanks
-J-B0t

p.s.
I love this heli, everything else has been no-sweat and it went together with no hassle at all.

[aralan]

I hear a clicking on mine during spool down and when spinning the head by hand. The clicking is periodic and occurs at the same position in the main pulley's rotation every time. If I put my fingers on the main gear while spinning the head, I can feel the clicking through the main gear.

I haven't figured out the exact source yet but it sounds like you folks are hearing the same thing.

[snipealot]

I hear a clicking on mine during spool down and when spinning the head by hand. The clicking is periodic and occurs at the same position in the main pulley's rotation every time. If I put my fingers on the main gear while spinning the head, I can feel the clicking through the main gear.

I haven't figured out the exact source yet but it sounds like you folks are hearing the same thing.

Yup thats exactly whats going on with mine. I have two machines and only the older kit purchased about six weeks ago does this, the newer one thats about two weeks old does not make that sound.

[aralan]

I got a second kit this week. I swapped the hub from the new kit in to my existing machine and the clicking seems to be gone. I put the old hub in to the new gear stack and I can reproduce the play. Seems like the root cause could be the jesus bolt holes in the bottom of the hub drilled 1mm off?

[J-B0t]

Hey folks,

Aralan, that's Interesting I suppose the question is now, is it one of the Hubs or the sleeve that has the issue. In my case i think its the Sleeve.
Is it possible that you or Snipealot could do a control test, and check just the sleeve. It seems you have ruled out the Gears because you said you swapped out the gear stack. If not too much of a problem, try swapping only the Sleeve from the one that is clicking into the one that isn't, see if the problem follows the sleeve, or stays with the hubs.

I should be getting a new hub next week hopefully it will solve the problem.

Thanks
-J-B0t

[aralan]

I have to partially retract my last statement. The new hub isn't clicking, but it does have the same amount of play. I haven't flown the new hub yet though so I'll have to see how that goes. I have not swapped main gears yet, and while I didn't intend to swap the pulley either it's possible that I mixed up the pulleys while I was working on it earlier.

I'll do some more experimentation over the weekend. Some of it can be a little slow since swapping the hub takes twelve bolts and two grub screws.