450 pro whirring noise at high head speed?

[Delarado]

Hi guys


Just put a 14t pinion on my 450 and at high head speed (90% throttle as opposed to 75%) it makes a funny whirring noise?

It's generally only at a hover and goes away when pitch pumping of fast climbing...

Any ideas what it could be? It's belt driven by the way (450 hk jobby)

Cheers

[paulsouthport]

Without wishing to sound like a D[i]ck, err, helis do tend to whir..... it's what they do!
Sorry!
can you post a recording?

[scuba steve]

have you calculated your expected HS at 90% throttle with your new 14T pinion ? just to be sure that its not exceding that of your blades. it could just be normal and your not used to it or it could be a warning that something is being put under too much strain.....safety first

[tourerjim]

With 14 tooth you will get that sound, why did you need to put 14.???,

[Delarado]

Jim...for a laugh to be honest! Its on a heli that I "don't care" about. It has align blades so I thoght i'd stick a big pinion on it for fun. The 12 felt a bit low, so I bought a 13 to use and a 14 for a laugh.

Its not a simple whirring, it sounds more like a mechanical rubbing or something I'm not sure how to describe it! It only happens at 90% head speed though - anything lower and it stops.

Ill lube everything just now and see if it goes away... Is there anything that you guys can think of though?

Ill get a video when theres someone else around to film it!

[paulsouthport]

Maybe the motor bearings are getting a bit worn, harmonics making it audible at the right headspeed.

[Jez N]

Maybe the motor bearings are getting a bit worn, harmonics making it audible at the right headspeed.

What about 100% throttle?

What is the calculated headspeed, is it the 150 tooth main gear like with the TT version. I use a 14T pinion no probs and others are using 15t pinions.

[Lynx.1677]

Nowt wrong with a 14t pinion. The Align pro with 450Mx motor comes with a 15t as standard.

[Delarado]

I havent tried 100% throttle, I might give it a go for a laugh - Didnt want to go that high, headspeed calc shows 3800 hs with a 14t pinion and 3550kv motor!

its a 150t main gear HS1219-01

[Delarado]

also how do you deal with throttle % on head speed calcs?

NOne of them seem to have this feature? Im assuming they are all calculating for 100% head speed?

[paulsouthport]

Just multiply the headspeed by the throttle %age. Your calc of 3800 looks a bit high though, I make it nearer 3200 at 90% throttle assuming 85% efficiency

[Delarado]

So you mean like, calc says 3904 head speed with my settings

so 3904 * 0.9 = 3513 at start of flight?

[paulsouthport]

Yeah, that's it. But how are you getting to 3904?

I use 14/150 * 12.6 * 3550 * 0.85 * 0.9 = 3193rpm

[Delarado]

Fast Lad Performance

[paulsouthport]

Ah OK. Just tried it and get 3904 too. Interestingly changing the efficiency has no effect on the calculation