Re: General 5-Star Build - Fast 50cc Single-speed

Mikey Antonakakis /
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For those that want to nerd out, here's how I've come up with that 5hp number.

First, I applied a simple Kalman filter to each axis of accelerometer data - I suppose it's a 1-D filter, with an adjustable parameter for sensitivity. There's still some noise in the data, but smoothing it out much more led to inaccuracy. Here's what the raw data for all three axes looks like, for reference:

RawAccelData-2019-09-03.png

After filtering the raw accel data, I subtracted out Z-axis (vertical) and Y-axis (longitudinal) steady-state readings. I got these by averaging about 20 seconds of the top-speed portion of the run. The camera was mostly upright, but tilted forward enough that the Y readings were about 4m/s/s steady-state. Also, this means that my acceleration (from going WOT) was registering on both Z and Y axes. I then combined the Z and Y axis data, where total = sqrt(z^2 + y^2). This gave a pretty reasonable approximation of the acceleration.

From there, I did a wild guess on total weight, I said 127kg. I'm 180lb, I assume the bike is a bit more than 100lb. Anyway, close enough for mopeds. Since F=ma, I can then calculate the force for the acceleration. Since Power = Force * velocity, and I have the GPS speed data, I can calculate the power required to give that acceleration. Note that this is actual power to the wheel - even though the engine is at 10,000rpm at launch and probably making ~4hp, NONE of the power gets to the wheel when you're not moving (since velocity is zero!). It all is going to heating the clutch. The torque, however, is easily calculated from the acceleration-derived force, using tire radius, sprocket sizes, and primary reduction (total gear ratio is about 21:1 right now).

I'm not going super fast, but there is a bit of aerodynamic drag involved, too. Using some rough empirical numbers, I used 0.675m^2 for frontal area, and 0.65 for Cd, giving a 0.44CdA value. Used the conditions of the day to estimate about 0.7kg/m^3 air density, and Drag = 1/2 * density * velocity^2 * CdA. Multiply by velocity again to get power. Add drag power to the acceleration power to get total power to the wheel.

All calculations are summarized in this plot:

1DKalman-2019-09-03.png
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Subject Written By Posted
  General 5-Star Build - Fast 50cc Single-speedTopic by: Mikey Antonakakis Mikey Antonakakis 09/03/19 03:20PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 03:32PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 04:14PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 04:21PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 04:46PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Overpriced Parts Overpriced Parts 09/03/19 05:10PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 05:19PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:08PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:22PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:32PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:41PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:49PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:55PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 06:59PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 07:05PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 07:13PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/03/19 07:43PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Aaron Blair Aaron Blair 09/03/19 09:23PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Johnnie Distefano Johnnie Distefano 09/04/19 12:39PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/04/19 03:44PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Chris Squid Chris Squid 09/04/19 08:25PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: ken gilbert ken gilbert 09/05/19 05:32AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 11:03AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 11:23AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 11:39AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 11:47AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:07PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:19PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:25PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:32PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:37PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 12:43PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Brandon Weiss (Detective brandon to you) Brandon Weiss (Detective brandon to you) 09/05/19 12:44PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 02:17PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: alex . alex . 09/05/19 02:03PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 02:20PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 02:26PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: ken gilbert ken gilbert 09/05/19 02:22PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 02:33PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 02:41PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 03:09PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 03:15PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/05/19 03:47PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/06/19 01:18AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/06/19 01:46AM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/12/19 11:03PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/14/19 10:21PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Born to be WillD Born to be WillD 09/18/19 07:33PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/18/19 07:49PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Alex Hedrick Alex Hedrick 09/21/19 02:30PM
  Re: General 5-Star Build - Fast 50cc Single-speedRe: Mikey Antonakakis Mikey Antonakakis 09/21/19 10:16PM

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