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Discussion Starter #1
I'm hoping this won't come up dry as usually happens but here goes: there are some smart phone accelerometer aps available for free. I'm hoping that several people will download and do some panic braking in order to share the data. I asked on another group also but no dice as yet, excepting that one person observed that he questioned how valid would be the data, given different mounting, etc.

So, there are two things:
1) Can anyone speak to the technical problems in using these aps on various phones to gather comparative data?

2) Will some of you please do some hard braking (hard as possible) from 45 mph to stopped and report the graphs?

It would be most interesting and potentially useful if we had some average numbers with which to compare. When someone is questioning the effectiveness of their brakes, information as to braking performance could point to whether their brakes are typical or less effective.

We plan to do a series of tests when Mike has time to bring his stock Gen1 and hope to have data for comparison as follows:

1) Stock Gen1 with standard pads.
2) Gen1 with 250 Ninja master cylinder
3) Gen1 with 320 EBC rotor and 250 Ninja master
4) Gen1 with 320 EBC rotor and stock master
5) Gen1 with Gen2 front rotor and SV650 caliper
6) Gen1 with Gen2 front rotor, SV650 caliper and 250 Ninja master (same as my bike)

I would like to compare to a stock Gen2 and to try a Gen2 front caliper on the Gen1 but am dissuaded by the need to fabricate the adapter when will definitely not be running the Gen2 caliper. It would also be interesting to try the SV caliper with the 320 EBC rotor but, again, the adapter plate fabrication is too much for simple curiosity since won't be running that combination either.

I do recall that some were running the SV+ 320 so maybe someone will offer data?
 

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Why not perform stopping distance tests from known speeds?

Just askin'!

Otherwise, how do the smart phone accelerometers work? Integrated/differentiated GPS position readings vs. time? Bolt-on accelerometers?

Just wonderin'!

;)
 

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Discussion Starter #3
Stopping distances from various speeds is the back up plan but the little I did with an accelerometer on my phone showed a graph which offered more information since it accurately displayed the deceleration profile and allowed one to identify the deceleration rate between speeds. That should remove some of the problems with speedo variations (mine & Mikes have been corrected for speed while most have not).

I'm also interested in the use of the technology since is seems to offer more information and simpler as not requiring measuring, etc. When doing simple comparisons, we'd put some objects in the tank bag, then run up to speed and nail the brakes at a predetermined point. When stopped an object would be dropped to the roadside level with the foot peg, then repeat.

I'm not much better informed regarding the phone ap but as recall I had to have GPS on and that they use the phone's built in accelerometers. I tend to expect that the younger types will be more aware of this tech and hope that we can work out whether the use is reliable.

I need to get my ap out and play with it to get up to speed again but not now as Rupert the house rabbit is bugging me for treats so will get no peace. :)

Have a look and let me know what you think of the aps.
 

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I'm not much better informed regarding the phone ap but as recall I had to have GPS on and that they use the phone's built in accelerometers. I tend to expect that the younger types will be more aware of this tech and hope that we can work out whether the use is reliable.

I need to get my ap out and play with it to get up to speed again but not now as Rupert the house rabbit is bugging me for treats so will get no peace. :)

Have a look and let me know what you think of the aps.
No speaka "aps," Normk!

Did not realize cell phones (all?) are equipped with accelerometers.

Differentiating distance vs. time gives speed (as our GPS receivers do); the second derivative, the rate speed changes, should yield acceleration. Reckon that's a doable do with a GPS receiver, but . . . unsure whether all cell phones have GPS receivers.

Regardless, intriguing possibilities and interesting subject Normk; thanks for raising it.

--------------------------------

Back to measuring stopping distances, looks like using a GPS receiver to set the approach speed might be more accurate/convenient than using even a calibrated speedometer. While measuring distances is a drag, if distinguishable markers could be laid down and left in place for each trial, only one measurement from the starting point of the tests would be required.

The motorcycle magazines still use stopping distances when testing motorcycles, perhaps because this measurment has become a "convention," even though more precise and accurate measurement techniques and instrumentation are available.

=============================

Way leads onto way!

At least, SOME cell phones, apparently, have built-in accelerometers:

http://www.engadget.com/2012/05/22/the-engineer-guy-shows-how-a-smartphone-accelerometer-works/

:)

---------------------------------------
======================

Just speculating; an on-board accelerometer (piece of hardware) may be more useful than GPS location-vs.-time differentiation to determine acceleration, because . . . the "Z," or vertical, component is the most difficult and least accurate of the axes determinable from navigation satellite ephemera; a geometric fact-of-life. Z-axis uncertainties may degrade acceleration data synthesized from GPS positioning information . . . DISCLAIMER: Speculation only, I have no evidentiary basis for the concept.
 

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Discussion Starter #5
You have very proficiently outlined the picture. The last several models of smart phones which we have had have accelerometers. I understand that they are used for many phone functions. I do have to get back to playing with the one I tried a year or so ago because not certain that it also uses GPS. My dad has dementia and we are looking at various changes to their house to distracted from this somewhat so please excuse the increased level of confusion on my part. :)

If you have time, try one of the phone aps and see what you take from the experience. I would be appreciative of the perspective.



No speaka "aps," Normk!

Did not realize cell phones (all?) are equipped with accelerometers.

Differentiating distance vs. time gives speed (as our GPS receivers do); the second derivative, the rate speed changes, should yield acceleration. Reckon that's a doable do with a GPS receiver, but . . . unsure whether all cell phones have GPS receivers.

Regardless, intriguing possibilities and interesting subject Normk; thanks for raising it.

--------------------------------

Back to measuring stopping distances, looks like using a GPS receiver to set the approach speed might be more accurate/convenient than using even a calibrated speedometer. While measuring distances is a drag, if distinguishable markers could be laid down and left in place for each trial, only one measurement from the starting point of the tests would be required.

The motorcycle magazines still use stopping distances when testing motorcycles, perhaps because this measurment has become a "convention," even though more precise and accurate measurement techniques and instrumentation are available.

=============================

Way leads onto way!

At least, SOME cell phones, apparently, have built-in accelerometers:

http://www.engadget.com/2012/05/22/the-engineer-guy-shows-how-a-smartphone-accelerometer-works/

:)

---------------------------------------
======================

Just speculating; an on-board accelerometer (piece of hardware) may be more useful than GPS location-vs.-time differentiation to determine acceleration, because . . . the "Z," or vertical, component is the most difficult and least accurate of the axes determinable from navigation satellite ephemera; a geometric fact-of-life. Z-axis uncertainties may degrade acceleration data synthesized from GPS positioning information . . . DISCLAIMER: Speculation only, I have no evidentiary basis for the concept.
 

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My farting about with GPS has shown that the lag time that the unit has with respect to changes n speed would make it less than optimal for trying to measure rapid changes in acceleration or speed.

I take great pride in my insistence in sticking with a dumb phone, but I do have a 7" Galaxy tablet that has accelerometers in it. I'll see if there is an app for it that might be useful and fiddle a bit.

My front brake is not working optimally at the moment and I need to do a rebuild. If feels a bit crunchy and I suspect things are a bit grungy down in the caliper. I could combine the rebuild with some data gathering.

"It'll help keep me off of the bar stool," Tom said experimentally...

Tom
 

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Discussion Starter #8
Please, please do a before and after for your brakes. That will serve both you and us in separate ways: we will benefit from the contrast and you will benefit from being able to delay getting off the stool a bit longer. :stickpoke:



My farting about with GPS has shown that the lag time that the unit has with respect to changes n speed would make it less than optimal for trying to measure rapid changes in acceleration or speed.

I take great pride in my insistence in sticking with a dumb phone, but I do have a 7" Galaxy tablet that has accelerometers in it. I'll see if there is an app for it that might be useful and fiddle a bit.

My front brake is not working optimally at the moment and I need to do a rebuild. If feels a bit crunchy and I suspect things are a bit grungy down in the caliper. I could combine the rebuild with some data gathering.

"It'll help keep me off of the bar stool," Tom said experimentally...

Tom
 

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Physics Toolbox Accelerometer



This accelerometer app measures and displays a graph of G-Force vs. Time(s) that can be exported in an e-mail as a .txt attachment with comma separated values (csv). G-Force and acceleration measured in the x, y, and z dimensions are displayed separately on the graph, and the total vector sum is displayed digitally.
Who could ask for anything more? :)

Just a guess, but . . . I imagine precise orientation of the accelerometer platform (the cellphone, tablet, whatever) with respect to the bike's axes, especially the axis of forward motion, will simplify data collection and analysis.

Disclaimer: I have a dumb phone.

Great marketing idea: Offer for sale a GPS receiver with accelerometer and app built-in.

WAIT! It's been done already! (At least, it WAS done, at one time.):

https://www.sparkfun.com/products/retired/9838
 

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Damocles -

I'm still learning about this but orientation is critical, it would seem.

There are two programs I have tired so far. The first would display X, Y, Z, pitch, roll, and yaw. It seemed overly complicated and, as far as I could tell, couldn't record data and save it to a file.

The one I chose will show X, Y, and Z and total G force, where X is to the right and left, Y is up and down, and Z is forward and backward IF you are holding the table facing you and oriented vertically. The definitions change with respect to the earth if you change the tablet's orientation, of course.

The app can display none or all of the axes and can record at command. Once the recording is stopped it will prompt for a file name, which it saves in CSV format. Irrespective of what is displayed it records all data.

The bugaboo is that I have to figure out some way to mount it to rigidly mount it to the bike in a vertical position. That would be best, but I suppose most any other way could be made to work. I'll have to look and see what RAM offers by way of a mount.

Tom
 

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Damocles -

I'm still learning about this but orientation is critical, it would seem.

There are two programs I have tired so far. The first would display X, Y, Z, pitch, roll, and yaw. It seemed overly complicated and, as far as I could tell, couldn't record data and save it to a file.

The one I chose will show X, Y, and Z and total G force, where X is to the right and left, Y is up and down, and Z is forward and backward IF you are holding the table facing you and oriented vertically. The definitions change with respect to the earth if you change the tablet's orientation, of course.

The app can display none or all of the axes and can record at command. Once the recording is stopped it will prompt for a file name, which it saves in CSV format. Irrespective of what is displayed it records all data.

The bugaboo is that I have to figure out some way to mount it to rigidly mount it to the bike in a vertical position. That would be best, but I suppose most any other way could be made to work. I'll have to look and see what RAM offers by way of a mount.

Tom
It's a KLR - throw something together - the below could easily be rotated to vertical. My previous version was an iphone with a $5 rubber case attached to a plank via velcro (with rubber band around top and bottom to make sure velcro didn't come loose). Phones are easier to deal with than we like to pretend..



 

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Just thinking further about measuring the G-force of braking deceleration . . .

Typically, motorcycle tests in magazines disclose stopping distance at a given speed; say, 60 mph.

A G-force deceleration impulse over a braking interval can be related to, well, STOPPING DISTANCE.

Thus, I propose: Upon capture of braking G-force deceleration data, TRANSLATE this data into stopping distance.

Then, as a validation of the methodology and calculation, actually MEASURE the stopping distance.

With reasonable corroboration between stopping distance and accelerometer measurement, the G-force deceleration data can then be translated into equivalent stopping distances, for clarity of understanding the significance of the numbers, and for comparative purposes.
 

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You Guys and your electronic 'tools' are at least 10 feet 'over my head'.
But keep going, please. I like to stop, quickly! :)
 

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One BIG variable has not been addressed or even mentioned yet in this project....tires. Good brakes on poor tires or bad brakes on good tires could yield the same performance data. Obviously a street tire is going to be able to stop quicker than a knobbie to simplify the illustration. To get accurate braking performance data tire adhesion must be eliminated as a variable. I have no idea how that could be done.
Weight is another big variable. Total weight including a heavy or light rider or cargo and fuel load needs to be accounted for. Oh! Of course the road surface and temp as well!
Just a couple of thoughts I had....:t1204:
Regards....justjeff
 

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One BIG variable has not been addressed or even mentioned yet in this project....tires. Good brakes on poor tires or bad brakes on good tires could yield the same performance data. Obviously a street tire is going to be able to stop quicker than a knobbie to simplify the illustration. To get accurate braking performance data tire adhesion must be eliminated as a variable. I have no idea how that could be done.
Weight is another big variable. Total weight including a heavy or light rider or cargo and fuel load needs to be accounted for. Oh! Of course the road surface and temp as well!
Just a couple of thoughts I had....:t1204:
Regards....justjeff
Good points; I somehow had assumed tests would be performed with the same tires, inflation, temperature, humidity, road surface, bike loading, etc.; in other words, with as few variables as possible.

Then, some differences in brake system performance might be observed, relative to brake pads, hydraulic cylinders, etc.; whatever configuration changes made to the braking system.

Yet, the Heisenberg Uncertainty we shall always have among us! (Overly-simplified and probably inaccurate summary of the Heisenberg Uncertainty: MEASURING a process itself ALTERS the process being measured . . . )

:)
 

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Me, my abilities, and my brakes are like Schrödinger's cat. Add to that the Heisenberg and you're gonna get what you're gonna get.

I agree wholeheartedly with Jeff and Damocles. The only way to get good data on different brake set ups is with the same bike, rider, tires, course, and day, inflation, humidity, wind ad infinitum. And the way to do it is with stopping distances.

But we don't have that. Heck, I don't even have a partner to help measure stopping distance nor a place to do it without involuntarily gaining a partner from the Redondo Beach Police Department.

So, we do what we do, report what we can, and ponder the results and say "That was fun" and try and discern if we learned anything.

Tom
 
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