Selection of suitable Gas Engine

Hello DIY Drones,

I am new to this forum. I am planning a build an UAV (Helicopter) that can carry a payload of 20 Kg. The UAV with this payload might weigh between 30 to 40 Kg (of course with very good Engg.). Also, the UAV has to travel at least to 20 or 30 km distance in one recharge. Hence I believe, gasoline powered UAV is cheapest option. However, I have tried various Engine options like Zenoah, DLE. Not able to find a suitable engine. Could someone suggest me a suitable engine or some other suitable option to fly the UAV?


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  • Ups. I forgot to mention mention my first couple of questions

    How to find the required engine capacity (in CC) or the power (in KW) to lift an helicopter of x kg mass? any basic equations available? I am still working on it.

    Secondly, whats the difference between a helicopter engine and a plane engine. If there are no major diff. why can't I employ the DLE engines to the propeller through a bevel gear mechanism?

    Also, I just want to (atleast try to build) build this copter within a budget of 5k $


  • Sikorshy solved this problem about 20 years ago, with special designed wankle engine, should be stuff on the WEB about it.



  • Ok, so here's another question, do you want to go direct drive, meaning basically one of the large traditional RC gas helicopters or my though is an engine/generator and some of the current large quadrocopters with a battery buffer?

    4strokes are heavier, less power to weight ratio but far longer lived and tons more efficient. That said a Honda EU1000i is a 4 stroke 50cc weedeater engine and a dc alternator. Strip out the inverter and all the stuff you don't need-and there is a really nice DC power source. You would be very hard pressed to build your own equivalent coupling of an engine and generator thus the cost is fully justified and you could sell the parts like the inverter board which you don't need.

    Again, it's 13KG but's that's with all the housing, electronics and stuff you don't need. For example, you can browse the parts diagrams and see what I mean here:


    Once you strip it down, it's this

    16pounds plus whatever the generator weighs. (the EU1000I complete was 28.66 pounds)

    Or this much smaller 35cc engine

    Otherwise, your into regular gas RC helis like this (note that price is for the kit, minus engine, servos and everything else)

    Which takes up to the 26cc 2 stroke.


    Not sure of payload but barring some really expensive options like a much bigger Yamaha


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