Measuring power on the fly.

[jellyrug]

Anyone tried doing this with an Iphone and "Performance Meter Pro"?

Second question (secret project maybe): If you can buy a powermeter that gives you power at the back wheel live (+1.5 - 1.5% accuracy), all the time while you ride, with logging ability for around $1,500 do you think it would sell? Or, if you could buy it for around $2,500 with air/fuel, rpm, gear, gps route, slope/altitude, speed, temperature and power display as well as logging, do you think it would sell?

We can also add acceleration, 0-60, 1/4 mile times etc, as well as stopping time and distance.

Means being on a dyno for every ride.

 

[IG.]

I think there was a product which appeared a few yeas ago which would measure whatever was possible to measure utilizing accelerometer sensors. Forgot the name. IIRC it was a few hundred dollars. I don't think it would fly for the pricing you have in mind. The more advanced product could be a few hundred more, but more than that would be hard to justify.

I think many would love to have a toy like that, but for the right price. If you could get the pricing down...

 

[Twobrothersbusa]

They've been around a long time....all you need to know is the weight of the vehicle. It does the rest.

G-TECH/Pro Homepage

 

[jellyrug]

They've been around a long time....all you need to know is the weight of the vehicle. It does the rest.

G-TECH/Pro Homepage

The problem with that is accuracy, they do not account for barometric pressure, wind, rider position on the bike, etc. Also, when not accelerating, they use Google Earth data for slope which could be way off. If you accelerate up a slope, the data is also questionable. The only thing they do well is reasonable repeatability under similar climatic conditions.

The Iphone program above attempts to do the same, but there are no reviews, so it may be $4 lost.

Most competitive cyclists already do this, we either measure power at the back wheel with a strain gauge, or at the cranks, then use sensors and GPS data to do the rest. A good setup will cost us anywhere from $1,500 to $4000.

https://shop.srm.de/store_usa/index....html&XTCsid=5d367af6f2eecaffdc528bc18a9f8a2c

Here is the Motorcycle/Car Iphone App

http://appcrawlr.com/ios/not-only-car-performance-meter

https://www.facebook.com/performancemeter

 

[fallenarch]

I have been playing with accelorometers and gyros for awhile. It's pretty easy to calculate slope using 6 degrees of freedom type divices. If you measure how long it takes your bike to move it's weight combined with your weight a certain distance you can easily calculate the work done and that is the effective HP. This is actually a good measure of power because it is real world - dyno results are weighted. However it is not consistent because it includes things like wheel slip. If you rigged up a device to measure these things and then had it remember the values like a data logger it could average them and tell you what your HP is pretty accurately.

A more useful use for a 6DoF device is to do things like cancel a signal light automatically when you get the bike back upright or pass through 0 degrees. Or flash a warning light when you hit a certain G force or lean angle. I know the Ducati and BMW TC units know the lean angle of the bike and adjust the TC by it. I got into it because i wanted to make a gyro cam like Rossi had. Now you can buy a gyro stabilized gimbal for a GoPro for $150!

 

[fallenarch]

The truth is on the street there is very little you need to know as far as instrumentation. You can even shift by feel, as i rarely even look at the tech. On the street you need to be focused on the road surface, judging speed for conditions, and watching cagers trying to kill you. The engine rpms should be by feel. I even judge speed by feel most of the time. Beyond that, any other information is clutter. I even think bike GPS units should be sound only.

 

[jellyrug]

It's pretty easy to calculate slope using 6 degrees of freedom type divices. If you measure how long it takes your bike to move it's weight combined with your weight a certain distance you can easily calculate the work done and that is the effective HP. This is actually a good measure of power because it is real world - dyno results are weighted.

The challenge is wind resistance, which is an assumption in the math. Depending on rider size and position, as well as wind speed and direction that can make a big difference.

I'm tempted to install the Iphone program, it's not the $4 that bothers me, I just don't like being scammed if it is a POS.

 

[sixpack577]

I have a G-Tech, never could get it work right on any bikes(don't know why).
The 1/4 mile times where dead on in cars, but the hp numbers were all over the place.
400whp one time 123 the next, 240, ect. crazy number variations every time.

 

[Twobrothersbusa]

I always ran two or three as required to get a couple that matched. Mine worked fine for what I was expecting for the price.

I have a G-Tech, never could get it work right on any bikes(don't know why).
The 1/4 mile times where dead on in cars, but the hp numbers were all over the place.
400whp one time 123 the next, 240, ect. crazy number variations every time.

 

[RedBusarider]

The challenge is wind resistance, which is an assumption in the math. Depending on rider size and position, as well as wind speed and direction that can make a big difference.

I'm tempted to install the Iphone program, it's not the $4 that bothers me, I just don't like being scammed if it is a POS.

Remember you get what you pay for.

 

[jellyrug]

Why would you need / want to have a device with that kind of accuracy? What use would having that precision of information provide? How could you turn around and apply it to anything on the vehicle that you couldn't do with +/- 5%?

I'm just curious on your line of thinking here. I put a Magnacharger blower on my Mustang years back and used a GTech (2005 ish) to get a baseline and see what gains I had after the install. Not sure how knowing within a HP or two would change that?

Resistance from air is proportional to the square of air velocity. So if you do a run at 175 hp as an example today and a few days later after major mods you do the same run but there is a slight head wind, you will be way off. Much more than 5%.

 

[Twobrothersbusa]

Now my head hurts...

 

[fallenarch]

The only good that sort of thing is, is to show trends. Too many variables that can't be accounted for. But many of those variables are present in a dyno too. No 2 dynos are the same, air pressure and temp change performance, ram air doesn't contribute as it does in real life, engine runs hotter due to air flow, etc. All of these things really give you a baseline not an absolute measurement. Still like 2BroBusa says who cares?

 

[jellyrug]

The only good that sort of thing is, is to show trends. Too many variables that can't be accounted for. But many of those variables are present in a dyno too. No 2 dynos are the same, air pressure and temp change performance, ram air doesn't contribute as it does in real life, engine runs hotter due to air flow, etc. All of these things really give you a baseline not an absolute measurement. Still like 2BroBusa says who cares?

This time we agree.

The same technology used in professional cycling, available to any consumer from about $1500 upwards, built as a strain gauge with a gyro counter and ANT+ comms, all into the rear sprocket would be a lot more precise than any dyno. After in production also a whole lot less expensive.

 

[jellyrug]

Now my head hurts...

The reason you need so much horse power to push past 200mph is because you are fighting mainly one enemy. Wind resistance. For every mile per hour your bike speed increases, the wind resistance holding you back increase squared. So an increase in 10 miles per hour on the bike, increases the resistance holding you back 10 square or 100 times more. The device you used, uses a math calculation based on programmed conditions, which may be very different to reality. Temperature, barometric pressure and wind blowing in any direction cannot be accounted for and makes a big difference.

To give you an idea, if I am cycling in a peleton and I go to the front of the riders to pull, I would be putting out about 320 watts to the back wheel. (Lance Armstrong = 480 watts at lactate threshold) Once the other riders take over and I get back into the peleton where I can slipstream, that power falls back to around 200 watts. I do this every Saturday by the way, so there is no guessing here. It is just wind resistance that changes. If I had to use a device that does this by math only, it would not know the difference.