ORIGINAL: airjawed
Finding the source of a vibration is a step by step process. Something either in the head assembly or tail assembly usually is the cause. You can break it down by spinning it up slow and fixing the heli down. I wouldn't tell you to hold it in your hands for safety reasons though that is what I do. Take your pick as to which way you want to go. But you can take of blades first. If still vibrating take off head assembly, then take off tail assembly, then take off belt...and so forth till you narrow it down. Check out every single piece! I had a vibration caused by dirt in the belt drive gears. Be thorough!!!
The reason people are asking about the pinion is that if you have too much headspeed then the tail will be spinning very very fast with a 4s configuration! A 3000 rpm headspeed has a tailspeed of around 13,000rpm. Overspin the tail and you will either explode the tail or have a vibration that no matter your best efforts of balancing just may be impossible to eliminate.
So get yourself a tach that can actually read your headspeed. Not one that stops at 1500!! or whatever!
On a side note the esc may be putting out correct voltage but with 4s the amps it can handle is LESS! That is because there is more voltage that needs to be dropped and in the ESC it is converted to heat! Long story short a BEC is very much advisable in a 4s configuration.
Thank you for the info and if you read some of my above posts the vibration was there before I switched to a 4s pack, and as I think I said this was an experiment that I have not had much time to try since I asked about it sometime ago. My model avionics tach goes to 2800 not 1500. I have been trying to do a step by step elimination of the vibrations I am at a point where I have checked and rechecked many things and was looking for ideas on what to check next. I don't like the idea of spinning up the heli with out blades I read in a book that it was not safe so sorry if I disagreed with the other posts on this matter from now on I will do things that the experts on RCU tell me to do.
I realize why people were asking about the pinion but I was trying eliminate one problem at a time and since I had already switched to a 11t pinion my next move was a different motor which I wanted to wait because I wanted to get rid of the vibration, I could hardly hover because the vibration was so bad or at least I didn't want to hover for long.
once again thanks for the advice about the BEC but I don't think I'll have to worry about it since I will probably be using the 4s pack in my L-39 EDF the pack was bought to try in the heli and use in my EDF jet since I spent over a $100 on a different motor and BEC and ESC specifically for that plane.