Zero (0) Gram Datalogger Mount...

[StanleyM]

I've been doing some datalogging of rim brake and aero aspects lately. Found out some interesting things. One of the loggers used is a 25 hz GPS + 3 axis Accelerometer + 3 axis Gyro puck style device. One of the mounting positions I used is on the stem as follows.

I replaced the normal 4 gram alloy stem cap with a...4 gram plastic bayonet mount. 90 degree twist to mount the logger, sorta like adding a DSLR lens. So Net Zero for the win!

I'll be sharing some data as time permits. I've compared various rim brake calipers, pads, weight weenie calipers, aero positions, cornering lean and the like. You can see acceleration per pedal stroke, shift points, brake "bite", modulation, deceleration between pedal strokes and so forth.

[Andrew69]

Sounds interesting!

[StanleyM]

Have done many measurements of all sorts...but here's an example of how CF handlebars can really suck up the road vibes compared to "Alum-in-ium". Clamped to the drops, no bar tape. Hands on the hoods. Same road / path on the road as best I could. I chose an alloy 36/38cm (hoods/drops) compact bar and a CF traditional shaped bar @180 grams 40cm.

[rpowell]

can you do a fast fourier transform of the data. curious what it looks like in the freq domain. 25Hz is a little slow as it only will measure up to 12.5. It should be a bit easier to tell if your data is legit tho.

[StanleyM]

can you do a fast fourier transform of the data. curious what it looks like in the freq domain. 25Hz is a little slow as it only will measure up to 12.5. It should be a bit easier to tell if your data is legit tho.

I'd want to use a different logger for that, for access to clean raw data among other things. This one has three axis 2000Hz accel & gyros besides GPS. BUT since it can only bluetooth to a phone for storage, the data is processed and smoothed IN the device. And then output via BT at 25hz, which is what I plotted. It corresponds well to the subjective experience and expectations as the alloy bar w/o tape or gloves is quite buzzy. While the CF is flexy during cadence, but very very smooth in ride feel as this one aint for sprinters. You can flex it by hand. So, inherently a large difference would be expected.

Here is the alloy bar, an FSA Omega 38cm. Shown is how the logger was mounted to a drop, via gopro clamp (with no rubber) to a 1/4-20 stud into the device fwiw. I can easily log GoPro data at 200hz and will if I get a chance as that is raw. My other loggers are larger and not as easily handlebar mounted or powered.

Thing is this simple method easily shows bar differences, tire and tire psi differences and more. It came in handy as I screwed around with rim brake optimization too (all sorts of braking improvements are possible, using motorsports practices).

[C36]

Obviously super interesting on many different fronts if you can analyse the data properly. I used something similar 15 years ago but we had hard glued accelerometers and bunch of wires.
Who makes the nicely packaged accel-gyro that you use?

[StanleyM]

Obviously super interesting on many different fronts if you can analyse the data properly. I used something similar 15 years ago but we had hard glued accelerometers and bunch of wires.
Who makes the nicely packaged accel-gyro that you use?

www.racebox.pro, no affiliation.

There are also numerous nice phone apps which one can utilize to log accelerometers, gyros, vibration and more.

While spinning up from a lower speed, you can look at the net acceleration from each pedal stroke, & deceleration between strokes (from rolling resistance and aero etc), measure tire rolling resistance, bike lean angles, "hard" shifts into the next gear - you name it.
Analyze on your phone or laptop via app, or in Excel etc.

Heh note the shift points under pedal load:

[StanleyM]

Here's a quick look at tire pressure vertical Gs, from the stem cap.

Coastdown test...can later get watts and CRR that correlate closely with BRR...separate aero vs total rr:

Time needed to travel a short distance:

Logger starts and stops via geotags:

[Gary71]

This is interesting reading. Thank you for sharing....., I have some (probably dumb) questions. Would how you are holding onto the handlebars and body weight through those touch points affect the readings? More so for when the data logger is mounted to the bar end i guess?

[StanleyM]

This is interesting reading. Thank you for sharing....., I have some (probably dumb) questions. Would how you are holding onto the handlebars and body weight through those touch points affect the readings? More so for when the data logger is mounted to the bar end i guess?

Good question! Sure it would affect things, which is why I specified sensor and hand positions and kept things constant. So would which levers one uses, bar tape and more. Main takeaway is that the flex / damping can help comfort, which we already realized I guess. But it could help evaluate other changes and bar options.

[maxim809]

Really cool. Looking forward to the braking data.

[StanleyM]

Really cool. Looking forward to the braking data.

Some nice results so far. Stunningly it looks like the Laws of Physics were not violated, and basic Motorsports practices provide benefit.