Protech ZOOM 425 ccpm Specifications download pdf (Page 225)

30.10.12. ECO 8/16 specific maintenance

• The one-way bearing in both plastic and aluminum autorotation hubs has been known to

become loose. Usually when this happens, the one-way bearing can be pushed out of the

hub with firm finger pressure.

This can be easily fixed by roughing up the bearing and autorotation hub mating surfaces

with 200 grit sandpaper and using thick CA to reassemble the unit.

• The tail blade grips (67542) should be checked periodically to make sure they are not too

loose. If they are, be sure to unscrew them from the tail rotor hub and apply fresh loctite to

the screw before reassembling.

• The main rotor shaft bolt (67599) is rather soft and can become bent in a hard crash. Be

sure to check this bolt if the main rotor blades have hit anything. If the bolt is bent, be sure

to replace it and do not fly with it.

• The battery holder O-rings (67587) will need to be replaced about once a year because

they will start to crack. These can be replaced with the stock Ikarus parts or you may be

able to find the O-rings(30mm ID x 3mm thick) cheaper elsewhere.

30.11. Useful equations

This is a section with various bits of math which are useful for calculating various parameters

of helicopters.

30.11.1. Calculating headspeed

There are three steps to calculating the headspeed:

1. Calculate the motor rpm

2. Check the motor's maximum rated RPM.

3. Calculate the gear ratio

In order to calculate the motor RPM, you need to know two things: the motor Kv constant, and

the battery voltage.

The Kv constant is the no-load RPM/V, or basically the RPM of the motor at a given voltage

with no load. If you multiply this value by the voltage, then the result is the motor speed at the

voltage with no load.

As the helicopter takes off, the load on the motor will increase, so the motor RPM will drop by

about 15%. So this unloaded RPM should be multiplied by about 0.85 to calculate the loaded

motor RPM.

For example, a Hacker B50-18S has a Kv of 2006, so the no-load motor speed on 8 cells (9.6

volts) is: 2006 * 9.6 = 19257.6 RPM. Under load the motor RPM will drop to about 19257.6 *

0.85 = 16369 RPM.

The second step is to check the motor's maximum rated RPM. For the Hackers this is about

60,000 rpm, so 19257.6 RPM is well below the motor's maximum rated RPM.

The third step is to calculate the gear ratio. The ECO 8 has a 180 tooth main gear and if the

Technical Appendix

212

1 2 ... 220 221 222 223 224 225 226 227 228 229 230 ... 239 240

No comments

Protech ZOOM 425 ccpm Specifications Page 225