4 ms·

That won’t handle the number of degrees of freedom a bobsled uses.

EthanHeilman 6y ago
Just thinking this through, wouldn't three weights on springs get you all the data? Or some sort of membrane containing a liquid than ruptures when a particular amount of force is felt in any direction?
- amelius 6y ago
  The problem with three axes is that the registration of the largest deviation by the pen happens for the axes independently.
  - VLM 6y ago
    Yet its still valid data in that its trivial to calculate the theoretical maximum peak accel based on the possibly independent peak accels of the individual axes. If in theory the max peak acceleration could never exceed 2 G then there's no point in continuing the study. If the theoretical max peak accel could be 57 G then there's a point in continuing the study. The whole problem is irrelevant anyway. The problem isn't one individual sled journey, the problem is thousands of competitors taking thousands of rides over many years, so "tens of millions". They are competitive with each other having small std deviations in performance so each sled ride is roughly the same. Tiny reliable cameras have been a thing for a century as have mechanical timers. Simply bolt a half pound telemetry package to every sled that snaps a single random point of data via camera or some weird linkage to clutches and springs. Then run a data analysis and make statistical predictions. You wouldn't even need a 1960s mainframe to run the statistical analysis. This would have been something near BAU for mid-century aeronautical engineers, for example. I'm sure something similar was implemented during the test program for the F-86 or maybe P-51.
- ChrisLomont 6y ago
  Peak is not enough - you need to know time impulse. A 10G accel over 1 sec has much different effect than a 10G over a nanosecond. And the measuring devices must also handle this nuance. A liquid has inertia, so won't register quick impulses, and the things it measures might not be relevant to what bio systems are interested in.
amelius 6y ago
True. How about suspending a little metal bullet in a gel, chosen such that the bullet will break through the gel if the G-force is more than a certain threshold. This will give a good indication if the forces are within an acceptable range.
- m463 6y ago
  Reminds me of shockwatch for packages.
- ChrisLomont 6y ago
  This kid of stuff is incredibly hard to use for accurate results. Gels (and all materials) are not perfect in any sense, and you'd need significant effort modeling any material you used - viscosity under all sorts of motions (since nothing is nicely linear), the gel itself is sloshing, compressing, has different lag times... It's possible in theory, but in practice would not be useful. Look at what planes (Air Force has lots of R&D) did for the past century to see the state of the art at each point and the methods used.

Just thinking this through, wouldn't three weights on springs get you all the data? Or some sort of membrane containing a liquid than ruptures when a particular amount of force is felt in any direction?

amelius 6y ago
The problem with three axes is that the registration of the largest deviation by the pen happens for the axes independently.
- VLM 6y ago
  Yet its still valid data in that its trivial to calculate the theoretical maximum peak accel based on the possibly independent peak accels of the individual axes. If in theory the max peak acceleration could never exceed 2 G then there's no point in continuing the study. If the theoretical max peak accel could be 57 G then there's a point in continuing the study. The whole problem is irrelevant anyway. The problem isn't one individual sled journey, the problem is thousands of competitors taking thousands of rides over many years, so "tens of millions". They are competitive with each other having small std deviations in performance so each sled ride is roughly the same. Tiny reliable cameras have been a thing for a century as have mechanical timers. Simply bolt a half pound telemetry package to every sled that snaps a single random point of data via camera or some weird linkage to clutches and springs. Then run a data analysis and make statistical predictions. You wouldn't even need a 1960s mainframe to run the statistical analysis. This would have been something near BAU for mid-century aeronautical engineers, for example. I'm sure something similar was implemented during the test program for the F-86 or maybe P-51.
ChrisLomont 6y ago
Peak is not enough - you need to know time impulse. A 10G accel over 1 sec has much different effect than a 10G over a nanosecond. And the measuring devices must also handle this nuance. A liquid has inertia, so won't register quick impulses, and the things it measures might not be relevant to what bio systems are interested in.

amelius 6y ago

True. How about suspending a little metal bullet in a gel, chosen such that the bullet will break through the gel if the G-force is more than a certain threshold. This will give a good indication if the forces are within an acceptable range.

m463 6y ago
Reminds me of shockwatch for packages.
ChrisLomont 6y ago
This kid of stuff is incredibly hard to use for accurate results. Gels (and all materials) are not perfect in any sense, and you'd need significant effort modeling any material you used - viscosity under all sorts of motions (since nothing is nicely linear), the gel itself is sloshing, compressing, has different lag times... It's possible in theory, but in practice would not be useful. Look at what planes (Air Force has lots of R&D) did for the past century to see the state of the art at each point and the methods used.