Gear ratio for TRM?

[nicco]

I plan to use a Toxic in my Predator Gasser.

What is the best gear ratio? I plan to have a headspeed around 1850.

Regards
Niklas

[bigrcr]

7.15 is what I am running in my Spectra-G and this work the motor at about 13250 RPM. The motor loves 12750-13500 RPM. I would stay in the lower end of this range without a tuned exhaust system so a 6.91ish would be a good ratio as well.

Just keep it fed with fuel, the more the better! :wink:

Hope this helps!

[asong26]

Nicco,

Did you end up getting the TRM on your Predator? What gear ratio are you currently using?

[nicco]

No, I use a PUH 231 modded by Ian Oddie. I'm using 6.92 as gear ratio.

/N

[asong26]

7.15 is what I am running in my Spectra-G and this work the motor at about 13250 RPM. The motor loves 12750-13500 RPM. I would stay in the lower end of this range without a tuned exhaust system so a 6.91ish would be a good ratio as well.

Just keep it fed with fuel, the more the better! :wink:

Hope this helps!

Hi John,

I need your advice on the optimal setup of my Heli. I Predator Carbon Gasser SE w/ Full Metal Heads upgrade, metal tail rotorbox setup.

Pinion: 13T
Main: 88T
Gear Ratio: 6.769
TRM modded G231 PUH

Main Blade: Carbon Fiber angled 720mm (Rotortech)
Tail Blade: Carbon Fiber 120mm (Rotortech)

Based on optimum head speed (2000?), should I be using a different pinion. Also, I believe my current muffler is Century V2. If I upgrade to either V3, or the Hatori, would that have an effect on what my optimum configuration should be?

I guess the answer(s) that I am looking for are the following:

1. At the current set up, should I change the gear ratio?
2. If I upgrade the pipe to either V3 or Hatori, do I need to change the gear ratio?

Assuming TRM runs at it's happiest @ 12750 RPM, or should I consider a different motor speed?


Thanks.

[bigrcr]

Sorry for the delay in answering your post....

You should be just fine with the ratio and exhaust choice.

My statement that the TRM runs happiest @ 12750 RPM is somewhat ratio dependant. On the 6.77 ratio the motor should like 12200 to 12500 the best from may past testing results. Of course the motor will not complain if you go above that, but your head speed will be nearing 2000 RPM.

Later,

[asong26]

Sorry for the delay in answering your post....

You should be just fine with the ratio and exhaust choice.

My statement that the TRM runs happiest @ 12750 RPM is somewhat ratio dependant. On the 6.77 ratio the motor should like 12200 to 12500 the best from may past testing results. Of course the motor will not complain if you go above that, but your head speed will be nearing 2000 RPM.

Later,


John,

Is it true that for Zenoah 231, the torque cuve begins to drop off at 10,000 RPM? First of all, is this true, and secondly, does the torque curve change after the TRM mod? Based on your statement, around 12200. Is this the max torque / gear ratio combo that I should be using?

I want to make sure that I am running the engine at max power / torque, without over-revving.

6.77 w/ 12200 RPM gives me 1846 head speed. Is this good enough for 3D?

I appreciat your help and input.

Thanks

[asong26]

John,

I've just found out that with the heavy duty clutch on the predator gasser, they have an issue of fitting smaller pinion gears. This is probably why they are shipping 14T / 88T. If I stay with the 13T, which I have now, and try to fit the new clutch, I will have to machine / grind the lower bearing block. If I avoid this, and go with the 14T, this gives the the gear ratio of 6.286. And at 12200 RPM, this brings the head speed at 1940. Is this ok? Based on your experience, what would be the 'happy' engine RPM for this gear ratio? Is this pushing it?

[bigrcr]

That ratio will work OK, but not optimal for 3D. That ratio will be more of a sport ratio but the motor should still be happy. The 12,200 RPM will be fine as well as the head speed that you state.

The motor mods do up the curves for both HP and torque a bit for sure. The G-231 loves to operate stock at 11,750-12,500 RPM. Modifying the motor lets it be happy above there (12,250-13,250 optimal). Once fully broken-in, you can go for more.... a bit at a time!

Don't try for that RPM when you first start out. Keep the motor happy at a lower RPM and rich until broken in a bit. You will be able to tell that the motor is breaking-in as it will actually require more fuel to keep it happy and keep the RPM under control. Just keep trying to make it as rich as possible each time you fly and you won't go wrong. As the RPM picks up again, rich-en it up some more. Once broken-in the need to continue to rich-en it will stop.

Many think that as the motor breaks-in, the motor will require leaning from the previous rich setting, this is usually incorrect. Actually you will most likely find that the last setting is now not rich enough. The reason behind this: as the motor breaks-in, things seat and the motor makes more power. Since the motor is now making more power, it needs to be fed....and so on.

One more thing...let the motor cool for 30 -45 minutes initially between flights, or a least until it feels only slightly warm to the touch. This helps to prevent heat related leaning and scoring and aids in the break-in process.

Hope this helps!!

[asong26]

Great advice and feedback John!

Thank you, that answers my question.