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Caleb James DeLisle

Apropos to nothing: Compact 2 stroke engine exhaust expander ("resonator")

1. Exhaust from the engine
2. Expands in cone
3. Reverses direction and continues expanding around the cone
4. Contracts around the second cone
5. Reverses direction and contracts more inside of the cone
6. Exhaust exits

Picture 2: A normal expander.

Replying to @cjd@pkteerium.xyz

𝔭𝔶𝔯𝔞𝔱𝔢

@pyrate@nicecrew.digital remote

I'd have a low resistance mesh to complete your catalytic process if that's the intent.

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Replying to @pyrate@nicecrew.digital

Caleb James DeLisle

@cjd@pkteerium.xyz remote

No catalyst, the 2 stroke expander is just a hollow tube, but the resonance of that shape is a big part of what makes the 2 stroke engine make power.

Replying to @cjd@pkteerium.xyz

Phobos

@Phobos@eientei.org remote

@cjd @pyrate But one gotta be mindful of the environment, so strap a catalytic to it as well.

Replying to @Phobos@eientei.org

Caleb James DeLisle

@cjd@pkteerium.xyz remote

Catalytic converters on 2 stroke engines are pretty rare because there's oil mixed with the fuel which is pretty bad for the catalyst.

That's also why you don't see 2 stroke engines on cars, they could never pass emissions regulations.

Replying to @cjd@pkteerium.xyz

𝔭𝔶𝔯𝔞𝔱𝔢

@pyrate@nicecrew.digital remote

This seems like your exhaust cycle is going to be partially rich with fuel.

Replying to @pyrate@nicecrew.digital

Caleb James DeLisle

@cjd@pkteerium.xyz remote

Yup, that's why they have worse thermal efficiency than 4 stroke engines, they absolutely dump fuel out the exhaust - and unless you're gonna do direct injection, it's basically unavoidable.

Replying to @cjd@pkteerium.xyz

𝔭𝔶𝔯𝔞𝔱𝔢

@pyrate@nicecrew.digital remote

Are you building your own model RC plane of peace with this?

Replying to @pyrate@nicecrew.digital

Caleb James DeLisle

@cjd@pkteerium.xyz remote

Haha, no.. Maybe some day, for now just playing with ideas.

In aircraft, 2 stroke engines are very attractive for their power/weight, and they're typically connected to the prop via a belt (as in pic).

Well, I'm tempted to use 2 full engines, one behind the other, and put a one-way clutch in each pulley so even if one engine completely disintegrates, you can fly single engine.

But I'd like to develop a separate oil system so I don't need to run mixed gas. May post a drawing when I come up with something I don't hate...

Replying to @cjd@pkteerium.xyz

Caleb James DeLisle

@cjd@pkteerium.xyz remote

Reliability is expensive, redundancy is cheap...