Lowering the gear ratio on a Spectra G

[dogg5306]

Hi guys,

It is said and agreed that the default 7.15 ratio that you get with a Spectra G kit is too high for 26cc Zenoah engine...
So can I swap to main gear (0865-93) with this one that is 0865-87... that does allow me to get a 1850rpm at the rotor level while the engine is running at less than 12500rpm...


Is that a good idea or am I just going into the wrong direction?
(Any other change needed for a higher rotor speed within the 26cc sweetspot?)

[carey shurley]

The original 1005 gas model used a 6.42:1 ratio which is friendlier with the G26. That is a 14 tooth pinion with a 90 tooth gear.

I'm not aware that the 14 tooth pinion is available in the right form to be used in this model though.

You can try just using the 87 tooth gear as well, you'll need to grind out the clutch mount holes on the 7.15 ratio plates and you may have to grind the mount holes on the bottom plate.

[dogg5306]

OK so things aren't that simple :-|

[rbort]

I know its not alot, but its a step in the right direction. I put in a 92 tooth main and its the exact same diameter as the 93 tooth so you don't have to grind or move anything, just replace the gear. It lowers the GR to 7.08 and I've been using a Hanson 3D Plus modified engine in the model for over 300 flights with no ill effects. I recently lowered the gear ratio after 393 flights, and now I have 415 flights to date and the motor seems to like the lower GR even though its a small change and not very obvious.

For the record I run 1650 head speed most of the time with normal mode at 1550 and idle up 2 at 1750 when I need it. This is 150 rpms lower than the recommended 1800 head speed which the Spectra-g was optimized for with 7.15GR and a G231 so I'm in the right ballpark again with this.

If you want to run 1800 head speed you will probably need to lower the GR further and do what Carey suggests.

-=>Raja.