Engine fan keeps coming loose

[bgymr]

I fuliflled my goal this weekend, a gallon through the NX4 in two days. Her and I know each other pretty well right now. But on the last flight, the fan came loose mid flight. When I installed it i tightened the nut but with zipties through the exhaust port. And then I tightened down the two screws on the fan itself. Lasted a gallon, but it shouldn't let loose at all.

Any suggestions?

[u8at711]

Get a crank shaft locking tool,
OS part # 71530400

[LegndarySaiyan]

The fan is loosening from the hub or the hub from the engine? Mine did the later when it was new. I had to replace the hub to solve the problem.

[bgymr]

I run a governor, and in flight it got a lot quieter and then then it started oscillating from max throttle to min throttle until I could flip into normal mode. The motor was still running when I landed. I shut it off went back to the bench and tried to start it again. But the motor does not engage. I can see the fan spinning, but the motor is not turning over. My guess is that this let loose:

[LegndarySaiyan]

Around my 5th flight that's what loosened on mine. I used sleeve retainer, blue loctite and ham fisted the nut on. Next time I tried to start it the hub came right back off. I ordered a replacement and it's been fine since with many flights on it.

[Matt Nasca]

I remove the back plate from the engine and wedge part of a towel between the connecting rod and the case. Then crank down the nut. It's never come loose in any nitro model I've had.

Piston locking tool would be best. YYMV

[rob221]

Fist off all what fan are you using stock plastic or after market metal ?
This has a bearing on whot might be your issue

If using the stock plastic fan these are notoriasly out off balance and can cause the hub nut to come loose over time .

If using alloy fan and have used gov magnets check to make sure both are still there as again can lead to unbalance in fan leading to hub nut loosening off

When you originaly mounted the hub to the engine did you use locktight if so did you clean the nut and thread first .

If you didnt use locktight why not
when you reassemble clean threads on both nut and shaft use a drop off blue locktight on the thread and secure as normal

[Blade3d]

I don't know if you guys have much nitro experience but you never tighten the nut by putting something through the exhaust port ,, you use a crank lock after you take the back plate off with some loctite ofcourse

[rob221]

i agree with the above statement whenever i buy a new engine i make sure i have the correct tool to lock the crank a case in point i have just ordered an os 105 for my 90 and at the same time ordered the locking tool so when it arrives i can mount the fan and hub correctly
In all the time i have been flying nitros i have never had a problem off the hub loosining if anything the problem has been when i wanted to remove it needed to use torcj to heat up nut
i fly nx4 velocity 50 n2 and elyq 90 nitro at moment have previously flown align 600 n and all have been assembled using the correct locking tool

[LegndarySaiyan]

I have and use the crank lock tool, installed an align metal fan when new, cleaned and thread locked the nut. This o.s. 37 is my 6th nitro heli engine. Previously I had never had a fan hub come off either. The one in my kit would not stay on, it was clearly out of tolerance. The new one has not been a problem. I'm just posting this so the OP knows someone else had a problem with that part. Not bashing the heli, I love mine, but bad parts happen.

[bgymr]

OK, took it apart last night, I was wrong. Somehow my clutch came off the hub. The two screws backed out on me.. I'm picking up a new hub today. But good discussion on how to mount the hub anyway.

Thanks guys.