I’m somewhat new drone building etc, however I’ve joined an engineering project at university and have been tasked with selecting the motors/props.
The layout is similar to the one pictured below, however the pusher props are also located along the wing. (not my design, imo the one pictured below is much better)
The maximum total weight is 15kg, wingspan of 2 to 3m. Based on the standard quadcopter thrust/weight ratio of 2:1, we would require 4 motors producing up to 30kg total, of which I’ve found a couple on t-motors under the V-TYPE section.
However I’m not sure if this ratio is correct - there’s two avenues of thought that occur to me:
the 2:1 ratio is so that a quadcopter is able to comfortably move in an agile manner, however as we are only using the VTOL props for a brief period of time to reach a desired height, manoeuvrability is not so much of a concern, as such we can get away with a lower ratio. This seems to be supported by this paper (bottom of page 2/12), which suggests 1.2-1.5 however I’m not sure if that only applies to tail sitter UAVs.
due to the large wingspan of the VTOL plane, the wings create a lot of drag, which means the motors need to produce even more thrust than they would on a quad, as such a greater ratio is required.
What thrust to weight ratio would you guys recommend? I understand that is hard to say for sure given the lack of specifications however a ballpark figure or even just pointing me to somewhere I can find out more would be a great help.
In addition the structures team have told me that the VTOL propellers should be less than 13 inches in diameter. The configuration I was previously looking to use was MN505-S KV320 with MF2211 props producing ~6.7kg each. I mainly chose these because they are rated for 6S as opposed to the 12S that a lot of the V-TYPE motors are rated, and it seems to be quite hard to find 12S batteries. Unfortunately they use 22 inch props, so they’ve asked me to shop around for a different configuration. Looking through the T-Motors store, I have a hard time finding any motors that are spec’d for 13 inch props that provide even 4kg of thrust. Is this an impossible task?
Any and all help would be greatly appreciated!