Hit by a truck... the iBike file

[rruff]

Yep... truck traveling at 45mph (he says) smacked into me pretty solidly from behind. Somehow he failed to notice that I was there. Anyway instead of being dead like I thought I was at the moment of impact, my injuries are fairly minor. So... thought I'd check out the iBike file just for fun, and see what it showed.

I expected a large spike in power when I was hit, but the opposite occurred. I was surprised that a sudden speed spike showed up, because the rear wheel (where the speed sensor was located) was pretty solidly jammed in the frame from the initial impact. The iBike surely experienced a sudden large increase in acceleration, but there was no corresponding power boost... the power instead tailed off at the moment of impact. I'm guessing that the iBike filtered out this acceleration entirely, determining that it was too large to be real. I know there is some filter to account for vibration. What do you think?

[minus10]

I'm just glad you can still post. Even if the injuries are minor, hope you are back on the bike soon.

[Velocomp]

We're glad you're OK! This sounds nasty...

The thing to look at is your slope reading. That should show the force of your impact.

[rruff]

The thing to look at is your slope reading. That should show the force of your impact.

The slope reading is on the graph... it just declines after the impact.

IIRC, Travis once said that power is computed directly from the accelerometer (along with the dynamic pressure measurement), and that slope is then determined using the velocity readings. So I think there is something funny with the data... ie it is filtering out the acceleration because it changed too abruptly. Heck, acceleration was probably way outside the sensor's range. The actual speed would have gone from ~13 to 45mph in a very short time. There could be different time constants for the various sensors as well.

[Velocomp]

Oops, sorry: I did not look at the entire graph.

I've seen other ride files with crashes in them, and slope definitely moved.

It looks like you were going uphill when you were hit; there's a 5% grade.

If, when you were hit, you were knocked to the side of the road abruptly, then the handlebars would point off center, causing slope to drop, and power might decrease, even though you were accelerating.

Just a theory.

[rruff]

It's hard to say which direction it was pointed later on, but since acceleration would have been >1g (probably >20g?) initially, it wouldn't have mattered if it was tilted a bit then. But that would have been a small fraction of second also. The rear wheel of the bike was hit first and it was buckled a little, but not enough to have acted as much of a shock absorber.

I'm damn lucky that I wasn't just a little farther to the center of the lane, in which case I would have ended up under the truck. I was also fortunate to land in grass on the side of the road.

[lorduintah]

I really do not think John envisioned using the iBike as a crash dummy meter

Glad you are OK - by any chance were you riding with a tail light flashing? If you were then the guy that hit you has even less to use as an excuse.

Tom

[rruff]

I didn't have a flashing tail-light, but there is really no reason why he shouldn't have been able to see me... unless it was a case of anything smaller than a car just not registering. He is 82, but at least he wasn't texting or talking on the phone at the time.

I was a little confused about exactly where I was hit, but noticed yesterday that a nearby intersection was at the top of a small rise. So I used that info and the slope data from the iBike file to determine that I was hit ~.13 miles (+-.01 miles) east of this intersection. Pretty cool.