Internet sleuths take down the SSC Tuatara's 316-MPH speed record

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by speedgoose on Monday November 02, 2020 @01:49PM (#24971577)

I used Audacity (and YouTube-dl) a few days ago to have an estimation of the top speed using the SSC information such as the gearbox ratios and the size of the tires, and the sound of the engine in the YouTube video.

Because it's actually simple to listen how fast an engine rotates, I found that they went slower than what is advertised and that the engine didn't rotate as fast as they claim. I computed 7530rpm and they claim 8600rpm.

I posted it on HN and I hope it's ok to post it again as a comment : https://fungiboletus.github.io/ssc-rpm/

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by tgtweak on Monday November 02, 2020 @02:59PM (#24972463)

> in V8 there is a cylinder firing at every 90° rotation which means 2 cylinder fire in one crankshaft rotation.

Your method and math checks out even without the tachometer observations - in a split-plane v8 (such as that in the scc tuatara) you have two cylinder fires per rotation of the engine. You have measured 251 cylinder fires per second (251hz) thus 125.5 rotations per second OR 7530/minute (RPM).

Hard to refute that.

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by m4rtink on Monday November 02, 2020 @07:30PM (#24975064)

Apparently (according to a YouTube video I watched :P) this is how they tell combustion engine powered torpedos apart via passive sonar. Analyzing the sound gives you the number of cylinders and number of propeller blades, which can identify the given torpedo type quite reliably.

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by bootcampwhere on Tuesday November 03, 2020 @02:04AM (#24977166)

Sonar tech here, this was true 20+ years ago but new torpedo and sub blade configurations are not only highly classified but any nuclear powered subs no longer even use blades to counter this exact problem. Only old russian and N. Korean subs can be identified this way anymore. Even when I was active duty 10 years ago china and us subs were basically silent and torpedoes surround themselves with air bubbles so the acustics dont really escape. You know something is coming at you fast but that it

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by trevorishere on Tuesday November 03, 2020 @10:38AM (#24980579)

Classified and visible on mapping services!

https://i.stuff.co.nz/technology/47327/Maps-site-reveals-US-...

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by m4rtink on Tuesday November 03, 2020 @07:27AM (#24978999)

Interesting! :)

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by jml7c5 on Tuesday November 03, 2020 @12:42AM (#24976727)

One possible error in ground speed measurement: the tire likely grew in diameter as it spun faster. I don't know how large the effect is here, but it's worth checking or noting.

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by speedgoose on Tuesday November 03, 2020 @01:47AM (#24977065)

True, it could explain a small difference. But here the difference is huge, especially in terms of RPM.

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Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by jml7c5 on Tuesday November 03, 2020 @02:32AM (#24977303)

Yeah, it wouldn't be enough to make such a huge difference. Nor would it explain the different RPM. Just wanted to note it for the sake of completeness.

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by gameswithgo on Monday November 02, 2020 @02:15PM (#24971883)

when i first saw the video the rate of acceleration in the 300mph domain made no sense to me, given the power of the car. it didn’t creep up to 316! it should have.

[ Parent | on HN ]

Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by toxik on Monday November 02, 2020 @02:32PM (#24972088)

Interesting analysis! I’ve seen the 2x multiplier myself, when I looked at the spectrogram of an AC induced whine in a speaker IIRC

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Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by SomeHacker44 on Monday November 02, 2020 @02:00PM (#24971704)

Just curious, did you take into account any possible doppler shift of the frequencies?

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Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by speedgoose on Monday November 02, 2020 @02:03PM (#24971756)

No, should I have? The microphone was inside the car.

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Re:Internet sleuths take down the SSC Tuatara's 316-MPH spee... by Waterluvian on Monday November 02, 2020 @02:18PM (#24971908)

If sound source and sensor were at a fixed distance from each other then no.

[ Parent | on HN ]