TWR Maneuverability Requirements
Here is the datasheet for the contrarotating motor I'm using.
- Since it is a TVC/VTOL platform, I need more than just a 1:1 TWR to fly
- Because of cosine thrust losses, when the motor pivots, we will lose a component of the vertical thrust produced
- If the motor pivots 10deg, assuming a starting thrust of 1400g, the resulting vertical thrust will only be 1157g.
- In order to maintain altitude during TVC actuation the thrust to weight ratio needs to be a good margin above 1:1.
- For this application, I'll be targeting a 1.5:1 TWR, to allow for a margin to maintain/increase altitude during TVC actuation
- Don't want to stop gaining altitude (or worse, lose altitude) every time the motor pivots
- This results in a max vehicle weight of 934 g.
- For this application, I'll be targeting a 1.5:1 TWR, to allow for a margin to maintain/increase altitude during TVC actuation
- A vehicle weight of 934g, with a max deflection thrust of 1157g yields a TWR of 1.24 during maximum motor deflection. Since 1.24 > 1, this is sufficient to maintain altitude and, albeit more sluggishly, increase altitude! Additionally, this slight thrust excess allows for a small amount of weight margin should the need arise.