Hello,

I have been doing research over the last week or so into how you could build a UAV that could replicate what can be done by MQ-1s (Reapers) and other high-cost military vehicles. One thing that seems to be concurrent across most medium ~ large platform UAVs is that they all use engines.

The thing is I have never seen a UAV on here that uses an engine. Now I know that this is because platforms used by 90%+ of the community are foamies but what if you were to use say a platform like the Hugin or the UAV 3000 which can accommodate these sorts of engines.

So my question to the community is why aren't gas engines used by us today? One reason I would look to use an engine is because I would love to have flight times >4 hours. I don't know if this is possible but if you were to use a single cylinder engine that you get from HobbyKing for <$200 could you get it to run for a while?

I ask this as I would love to be able to create a platform that could fly for long duration flights that would fly along the coastline, over the sea, that has an APM and gimballed zoom camera that could fly for miles providing telemetry via a 3G link.

If anyone knows the performance and fuel efficiency of these sorts of engines it would help greatly.

Regards,

Harrison

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Thanks to the miniaturization trend for PCs and laptops, there has been a revolution in efficiency for electric motors (originally used in hard drives and disc drives) and breakthroughs in batteries which have led to huge improvements in power to weight ratios, making it hard for fuelled engines to match.
Currently lithium and lithium-ion, etc. batteries, together with brushless electric motors are taking over from gas or nitro engines.

When you research long loiter gas engine projects, consider the large amount of fuel such an engine would need as well.

alot of guy enjoy not having to use a landing strip for takeoff either... gas could hand launch too but if you want a long flight you would want a gasoline engine...something like a g23 on about 38 ounces can go for 30 minutes easily... in the air and throttled back on the right prop, you would get some serious flight time..

there are smaller gas engines now like the gt8 ...its a 40-50 size engine...that thing on 38 ounces, i hesitate to think how long it could go..the disadvantage is you have to land on something that wont rip the gear out i would think..maybe gas powered with skids on the bottom like skis instead of wheels. or mount the motor in high pusher configuration for no landing gear to save weight and belly landings.

theres even a gt17 i think... the down side is that petrol engines vibrate...alot...with all the vibration sensitive equipment on board, it may be hard to get the stuff to autopilot with all the vibes...i flew gasser helis for years so i know the hardships of viibration from gassers. if you could overcome the vibration produced, then theres no reason a small petrol engine with a liter of unleaded couldnt easily oulast battery packs....i know you can build a huge capacity pack that prove me wrong here but at what cost ....

 

50,000 mah pack ...at 40 bucks a pack...on the low side 400.00 bucks.... 1.5 liters unleaded ...you get the idea.

 

i started with gassers...planes and helis and boats....but the above is just my humble opinion

There are plenty of us here that use gas engines with APMs. Like you, I am interested in long endurance flights, so I see gas as the only way to go for my build. (Im building a 3.5 metre plane with 6 litre fuel tank). But there are many more people that see the convenience factor of batteries, and quad copters. I like both options, but it depends on what interests you more. Yes vibrations are an issue, but there are ways around these problems.

Nice question! For research reason I need a multicopter with long autonomy. I'm asking to my self why not a hybrid multicopter. But I have no experience at all.  How big it have to be so it can overlap problems with benefits?

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