5 ms·

Interesting. It is surprising to me (but probably it is some aeronautics specification/need) that its 2-stroke engine uses 95 octane+4% oil mix, it is years th

by jaclaz 6y ago

Interesting. It is surprising to me (but probably it is some aeronautics specification/need) that its 2-stroke engine uses 95 octane+4% oil mix, it is years that using synthetic oil you can use 2% or even 1% oil.

giuliomagnifico 6y ago
I think it’s something like the engine of a chainsaw, or similar “gardening engine”, that can use up to 4/5% of oil
- jaclaz 6y ago
  Sure, but the whole point of reducing the oil percentage in two stroke engines has been (since like 40 years) to reduce the formation of carbon in the combustion chamber and - particularly - to have cleaner spark plugs (which imply better ignition) besides better combustion. Less oil in the mix (as long as lubricating is sufficient) is better. The traditional 4-5% is for mineral oils. Synthetic (totally or partially) oils can usually go on 2% (or 50:1) and in some cases as low as 1% (or 100:1). Modern chainsaws and similar are already at 2%, see (examples): https://www.stihlusa.com/information/how-to-guides/mixing-oil-and-gasoline/ https://www.stihlusa.com/information/how-to-guides/mixing-oi... https://www.husqvarna.com/au/forest/when-working/usage/how-to-mix-2-stroke-fuel/ https://www.husqvarna.com/au/forest/when-working/usage/how-t... https://www.amsoil.com/p/outboard-100-1-pre-mix-synthetic-2-stroke-oil-ato/ https://www.amsoil.com/p/outboard-100-1-pre-mix-synthetic-2-... Ignition in an engine for airplanes/drones/etc. is - obviously - much more important than in a common 2 stroke engine (chainsaw or similar), a "common" 2-stroke engine used in ultralights is the Rotax 582 (an earlier model was the 532) check its "limitations": https://en.wikipedia.org/wiki/Rotax_582 https://en.wikipedia.org/wiki/Rotax_582 The 582 has twin sparks (two spark plugs per cylinder) and runs on 50:1 mix: https://www.flyrotax.com/produkte/detail/rotax-582-ul.html https://www.flyrotax.com/produkte/detail/rotax-582-ul.html
  - CoolGuySteve 6y ago
    Might be for safety reasons, an engine seize in a flying drone would be catastrophic and dangerous compared to merely inconvenient as in most small engine applications. OTOH, piston scoring from burning oil will probably increase the chance of a lock up over time.
    - adrianpike 6y ago
      Except the onboard combustion engine is just to generate electricity, no? An engine sieze means you just have to land quickly.
      - jlcortex 6y ago
        That is true for HYBRiX, but there are other hybrid multirotors, which do not have a design well-balanced enough to being able to stay aloft on just batteries (batteries to lift a 25kg MTOW drone are heavy, so the drone needs to be very light, while still robust, to work properly.. it is tricky ;)
- sytse 6y ago
  For reference, the Stihl chainsaw I just purchased had a 50:1 gasoline to oil mix. That is 2%, of course there are probably 25:1 or 20:1 engines out there as well.
stickfigure 6y ago
Wild guess: The engine is an off-the-shelf part and that just happened to be the specs for whatever fit the size/weight/power/cost requirements.
SigmundA 6y ago
Could be duty cycle or cost of synthetic, either way 2-strokes are extremely dirty emission wise due to unburnt fuel in the exhaust.
FreedomToCreate 6y ago
https://www.pegasusaero.ca/ https://www.pegasusaero.ca/ This company designed hybrid engines for retrofitting onto drones
- jaclaz 6y ago
  Nice. Their generators are amazing, 1-1.5 KW generator in less than 3 kg, or 3 KW in less than 4 kg, really packed power. (BTW they use 2.5% or 40:1 mix)
jlcortex 6y ago
It's because of the duty cycle of the engine, we put it at a constant rate of 12000 RPM for hours. It is not the standard setting for that engine.

by jaclaz 6y ago

giuliomagnifico 6y ago

I think it’s something like the engine of a chainsaw, or similar “gardening engine”, that can use up to 4/5% of oil

jaclaz 6y ago
Sure, but the whole point of reducing the oil percentage in two stroke engines has been (since like 40 years) to reduce the formation of carbon in the combustion chamber and - particularly - to have cleaner spark plugs (which imply better ignition) besides better combustion. Less oil in the mix (as long as lubricating is sufficient) is better. The traditional 4-5% is for mineral oils. Synthetic (totally or partially) oils can usually go on 2% (or 50:1) and in some cases as low as 1% (or 100:1). Modern chainsaws and similar are already at 2%, see (examples): https://www.stihlusa.com/information/how-to-guides/mixing-oil-and-gasoline/ https://www.stihlusa.com/information/how-to-guides/mixing-oi... https://www.husqvarna.com/au/forest/when-working/usage/how-to-mix-2-stroke-fuel/ https://www.husqvarna.com/au/forest/when-working/usage/how-t... https://www.amsoil.com/p/outboard-100-1-pre-mix-synthetic-2-stroke-oil-ato/ https://www.amsoil.com/p/outboard-100-1-pre-mix-synthetic-2-... Ignition in an engine for airplanes/drones/etc. is - obviously - much more important than in a common 2 stroke engine (chainsaw or similar), a "common" 2-stroke engine used in ultralights is the Rotax 582 (an earlier model was the 532) check its "limitations": https://en.wikipedia.org/wiki/Rotax_582 https://en.wikipedia.org/wiki/Rotax_582 The 582 has twin sparks (two spark plugs per cylinder) and runs on 50:1 mix: https://www.flyrotax.com/produkte/detail/rotax-582-ul.html https://www.flyrotax.com/produkte/detail/rotax-582-ul.html
- CoolGuySteve 6y ago
  Might be for safety reasons, an engine seize in a flying drone would be catastrophic and dangerous compared to merely inconvenient as in most small engine applications. OTOH, piston scoring from burning oil will probably increase the chance of a lock up over time.
  - adrianpike 6y ago
    Except the onboard combustion engine is just to generate electricity, no? An engine sieze means you just have to land quickly.
    - jlcortex 6y ago
      That is true for HYBRiX, but there are other hybrid multirotors, which do not have a design well-balanced enough to being able to stay aloft on just batteries (batteries to lift a 25kg MTOW drone are heavy, so the drone needs to be very light, while still robust, to work properly.. it is tricky ;)
sytse 6y ago
For reference, the Stihl chainsaw I just purchased had a 50:1 gasoline to oil mix. That is 2%, of course there are probably 25:1 or 20:1 engines out there as well.

stickfigure 6y ago

Wild guess: The engine is an off-the-shelf part and that just happened to be the specs for whatever fit the size/weight/power/cost requirements.

SigmundA 6y ago

Could be duty cycle or cost of synthetic, either way 2-strokes are extremely dirty emission wise due to unburnt fuel in the exhaust.

FreedomToCreate 6y ago

https://www.pegasusaero.ca/ https://www.pegasusaero.ca/ This company designed hybrid engines for retrofitting onto drones

jaclaz 6y ago
Nice. Their generators are amazing, 1-1.5 KW generator in less than 3 kg, or 3 KW in less than 4 kg, really packed power. (BTW they use 2.5% or 40:1 mix)

jlcortex 6y ago

It's because of the duty cycle of the engine, we put it at a constant rate of 12000 RPM for hours. It is not the standard setting for that engine.