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Goldberg Tiger 2 Conversion

Old 06-07-2019, 04:57 PM
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Default Goldberg Tiger 2 Conversion

I have a Goldberg Tiger 2 40 powered by an OS 46 Max AX glow engine that I want to convert to electric.

I was looking on YouTube and someone had a Tiger 3 that they were recommending a brushless motor 1000-1400 watt. I was all set to buy a Turnigy Aerodrive SK3 4250 motor with a 1350 watt output, 500 kv, when a flying club member told me that this motor is more for 60 size aircraft. He recommended a Turnigy Aerodrive SK3 3548 840kv motor.

I would like to get another opinion before purchasing a motor. What do you think for this conversion? Which of the above motors would you use?


Old 06-08-2019, 03:39 AM
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Forget all the nonsense about can sizes and kv. Go to and buy a Talon Bigfoot 46. IT'S A 46 SIZE MOTOR. Any time you are doing a conversion and the manufacturer, not some jaywhacko on youtube, doesn't tell you what size electric to use always get a Bigfoot equivalent. In fact, get one even if the manufacturer gives you the info. They are great motors and cheap.
Old 06-09-2019, 06:56 PM
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Welcome to the witch craft of E power. I have 3 of the Tacon .46's, I also have the .10, .15, .25, .60, all work very very well. I run a 12x6, 12x7, 12x8, 13x6, 13x7 props with a 5s battery. Not sure how much ground clearance you have on the Tiger? 11x7, 10x8 3 bladed prop might fit, but would need to use a watt meter to make sure you are not pulling to many amps. If all else fails, just build taller landing gear. New nose wheel would be around 8 bucks, some piano wire 3 bucks?

Here is a nice online motor calc program. The free version the Tacon is greyed out so I could not try the 11x8 3 bladed prop. I let my script expire.

Old 06-18-2019, 01:26 PM
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Below an excellent quote about motor selection.
Better forget glow engine equivalences, too restrictve. Only for lazy sellers.

brushless motors Kv?.
Originally Posted by scirocco View Post
While an absolutely critical part of the system ...
... Kv is actually the item one should choose last.
  1. Decide your peak power requirement based on the weight of the model and how you want to fly it.
  2. Pick a preferred cell count (voltage) and pack capacity for how to deliver the power.
  3. Pick a prop that will a) fit on the model and b) fly the model how you want - often as big as will fit is a good choice, but if high speed is the goal, a smaller diameter higher pitch prop will be more appropriate.
  4. Look for a size class of motors that will handle the peak power - a very conservative guide is to allow 1 gram motor weight for every 3 watts peak power.
  5. Then, look for a motor in that weight range that has the Kv to achieve the power desired with the props you can use - a calculator such as eCalc allows very quick trial and error zooming in on a decent choice. For a desired power and prop, you'd need higher Kv if using a 3 cell pack compared to a 4 cell pack. Or for a desired power and cell count, you'd need higher Kv if driving a smaller diameter high speed prop compared to a larger prop for a slow model.
The reason I suggest picking Kv last, is that prop choices have bounds - the diameter that will physically fit and the minimum size that can absorb the power you want. On the other hand, combinations of voltage and Kv are much less constrained - at least before you purchase the components.

So Kv is not a figure of merit, in that higher or lower is better, it is simply a motor characteristic that you exploit to make your power system do what you want, within the constraints you have, e.g. limited prop diameter, if it's a pusher configuration, or if you already have a bunch of 3S packs and don't want to buy more, and so on.

Minor lay-out changes by RvS
Vriendelijke groeten Ron
• Without a watt-meter you are in the dark ... until something starts to glow •
e-flight calculatorswatt-metersdiy motor tips&tricksCumulus MFC

Last edited by ron_van_sommeren; 06-18-2019 at 01:29 PM.

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