Why:

mechanical pistons flying machines are really underrated feature in the mod, and not a lot of people use it for their contraptions because is really hard to power the moving pistons especially if you want the contraption to move fast and need alot SU. this is a missed opportunity for the mod because is a great feature that isn't getting almost any use.

For example we can use minecart flying machine for a lot of thing and it's a very useful feature but the problem with it is that contraption on the cart counts as an entity until we put it back in a cart assembler. If we are using a piston flying Machine the contraption counts as an entity only between the pushes, and it's something that is very useful for a lot of thing.

Currently we can only use magma blocks with fans on top, furnace engines, and moving water for waterwheels with vanilla pistons for powering moving pistons. The problem is that furnace engines need a non stop supply of coal and magma-fan setup is a problem when you need a lot of SU and I'm not even going to mention using vanilla pistons. All those options are not optimal and as I mentioned make pistons flying machine a missed feature.

So the obvious solution that would really benefit create would be to enable pistons to move windmills And water logged blocks or water source blocks (Adding the option to move water would be also great for many other things and should be done non the less).

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Screenshots:

Quarry with a big blob of magma and fan blocks and a furnace engine:

u/Tid_03 quarry on reddit why should we use regular pistons?:

Additional Context:

Sorry for the bad English I am not a native speaker.
Also pls add this.