Stratus Gap 0.015" too small?

[Aviation addict]

Guys,

When I completed my Stratus build I had a clutch to fan gap of 0.024" but after 9 flights it has reduced and settled (I think) at 0.015".

I understand from previous discussions that anywhere between 0.020" to 0.030" is ideal with a 0.035" max.

Is 0.015" too small a gap, and if so how do I increase it?

The manual says "there should be a small gap between the engine fan and the clutch driver" by the way. Why is it so critical to have a gap in the range quoted above, and why aren't they stated in the manual?

[Zilly]

0.015 is a little on the small side, what engine John?

z

[Aviation addict]

It's the OS91SZ H (p/p'd) my friend.

Seems to have settled there. Just measured it again and got 0.016" (not much of an improvement on 0.015").

If the gap closes completely in flight does this equal and 'accident' with metal to metal noise affecting the Rx?

[DavidH]

I personally think you don't have anything to be concerned about. The heat from running the model will cause the fan hub and clutch driver to heat up and expand. I don't see .008 to .009 less a problem.
The gap will increase as the model cools off. Take it in an air conditioned house and let it set a few hours and it will be close to .024 again.
David

[Aviation addict]

Hi David,

Yep I measured the 0.015" at the field (after doing very sedate flying with a cool running rich engine) and thought that expansion in the clutch/fan components could possibly be the cause for the reduction but sadly I've just measured it at home and its still 0.015/0.016". I'll just keep an eye on the gap after flights and see if it stays put.

Should I be concerned having 0.015" with a cool engine? Once I lean the engine off and boost the headspeed expansion might take affect I'd guess.

[christoffer]

I got a very tight gap on one of my stratus, so i went to my Local Kwik-E-Mart and
got some 0.5mm aluminum sheeting and made some shims that i put betwen
the A-frames and the bottom carbonplate.
Thats an easy way to get more gap if you are afraid of lock-outs(i am).
I dont know if thats neccesary with a 0.015gap but i feel more confident.
//Christoffer

[chrisvau]

I had to do exact same thing with some brass sheeting on my stratus to get gap right with same engine

[Aviation addict]

I am obviously a little concerned that the gap will reduce futher at some point without my noticing (even due to expansion of components while in use). Adding A Frame shims would make me sleep easier for sure. Its interesting to note that you guys have already done this mod.

[Aviation addict]

Went out this morning and bought some Brass Thickness Gauges and made some shims out of them. Shimmed the A Frames up another 0.010 " so its now 0.025" (cold).

I feel much happier with the gap now. Cutting up some perfectly good Feeler Gauges feels a little wrong - but it's ultimately much cheaper than the result of a lock out. Thanks for everyones help!

[MAJEFF]

A thinner washer on your motor will help the gap too.

[Aviation addict]

True - but would have taken hours to strip, re-balance the fan and re-build. This fix took about one hour and a half to complete - and I could accurately control the gap with the feeler gauge shims...