Strange throttle servo activity!

[davew]

Hi, anyone got any ideas on this one?

I crashed my 600NSP a few weeks ago and have only just got it back together. Skids, canopy, blades and that was it.

Whilst down I decided to fit new engine bearings and clutch liner, so engine has been out and back in.

Started it this afternoon. Engine runs sweet but when I raise the revs with the tx, the throttle servo suddenly and steadily starts to open up the throttle, working independant of the tx, ie all on its own! With the stick pulled back down the throttle servo is operating alone. Hit throttle hold and it drops straight back into tick over. Throttle hold off, increase revs slightly and off it goes again revving its nuts off!

The throttle servo (Spektrum DS821) works fine when the engine isn't running and responds immediately to "throttle hold".

Could there be some backfeed from the governor (Align)? I'm thinking that the magnets on the clutch bell spinning at several thousand rpm are generating some sort of electrical current?

Any ideas?

[jwatts007]

Sounds like your guvnor is working in normal mode if you want too turn it off you need too set it to a _ setting in your TX....

Or could be your throttle curve is not set up right.....

And that servo is not very good either it is bound too fail sooner or later.....

[davew]

Nothing wrong with throttle curve. Throttle curve only comes into play when you move the stick. This engine is picking up revs on its own.

I'm sure myself its a governor issue but was hoping someone more knowledgeable than I could explain what's happening.

Why would you say the servo is not very good either? It's got that servo on cos Jason Platts told me it was a good servo for throttle. It will fail one day I suppose but then they all will, won't they?

[jimmyhorns]

I suspect that your govenor is working when you dont want it to.

When the engine isnt running, the gov wont be getting a sensor input, so will default to the throttle curve that you are using. As soon as it gets an input it sounds like it is trying to govern your engine. This will make things look fine on the ground, but cause issues when you try to spool up and the conditions for the governor are met (usually something like receiving sensor signal, throttle over 20% and a few others depending on the gov)

Make sure that your govenor is off, and then work from there. You can do this by checking the govenors manual, on the align its usually indicated by a coloured led.

The magnets do create an electrical current, thats how they work, by inducing a current in the sensor, so this wont be an issue.