BT Tech Stiffening plate

<div class='quotetop'>QUOTE(danatt @ Apr 14 2007, 09:41 PM) [snapback]423458[/snapback]</div>

Missed that one, I've been loosely scanning through this thread...

I took a look at the gauge that you cited above and I like the idea, but I'm not sure that it will work well. I'm guessing that that device is a spring with some kind of displacement sensor attached to it. I'm not sure how well the unit will survive or even work in an automotive environment (vibrations, moisture, etc). I think your best bet is to remove the stock plate and measure the motion of the mount points with respect to each other using that device.

The way that unit probably works is that a spring is used to measure the force. The spring constant is know so one measures the displacement and you calculate the force. The point is that the tool is measuring strain and converting it to a Force. One issue in this measurement is that you will be measuring strain in a single direction which will not tell the whole story. Another issue is the resolution of the sensor. It simply may not be sensitive enough.

Now if you have one of these handy go ahead and try it. The data logging will make life real easy and it may actually work. I would build a fixture that has the unit loaded half-way so you'll be able to tell when the plate is in compression or tension.

The reason I like the strain gauge idea is because it's a direct measure of what we care about, that is, we want to know how much the stock plate deforms while driving and how much that compares to the BT plate. The other advantage is that we can attach as many of them to the surface of the plate and stock unit as needed. Depending on where they're attached and how they are oriented you can get info about how the plate is deforming in different directions. The electronics pose a bit of a challenge, but I've read analog signals and sent them to a PC before using a PIC microcontroller. I need to do a bit of reading on signal conditioning though. The down side is that each strain gauge can only be attached to a surface once, not a huge deal, but at $50 for a pack of 10 this could add up before I'm satisfied that I've gotten things right.

Unfortunately I don't have a whole lot of time right now to work on this (i've got a newborn in the house), but I'm happy to offer feedback and I'm interested enough in this that I'll work on it as I have time.

-momanz

 

<div class='quotetop'>QUOTE(efusco @ Apr 15 2007, 02:03 PM) [snapback]423664[/snapback]</div>

Also if this report turns-out to be positive and demonstrate with tangible numbers that the BT plate out performs the OEM for the car's stability performance, we can raise this results to Toyota's mechanical engineering department for a massive TSB recall on the Prius line for improvement, granting all the sweat, blood and tears to Brian's enterprise and merit. My 2 cents.

 

<div class='quotetop'>QUOTE(efusco @ Apr 15 2007, 11:03 AM) [snapback]423664[/snapback]</div>

I didn't see what sensor was being discussed until just now. Since it's from Pasco, and is 50 N (I'd question that being sufficiently strong), it sounds like the force sensor we use in our student mechanics labs. It requires a computer interface (the Pasco Workstation 750, or perhaps a less expensive unit). It's a sealed unit and I don't really remember (if I ever knew), what's inside. I suspect something like a piezoelectric device though.

What kind of forces are you expecting to obtain. Remember, 50 N is only about 11 lb. Is that enough for what you have in mind?

An image of the sensor is shown below.

[attachmentid=7491]

Dave M.

 

<div class='quotetop'>QUOTE(efusco @ Apr 15 2007, 01:03 PM) [snapback]423664[/snapback]</div>

I'm not sure that danatt's load cell idea will work with the device he cited, but if he has one available he definitely should give it a try. As for the strain gage, the gauges themselves are not too expensive. The electronics can run $100 for a simple unit that is single channel and provides a display, to $1k or more for multichannel datalogger that can dump measurements in real time to a PC.

Here are a couple of moderately priced units.

Are they easy to use? Each gage needs to be epoxied to the plate in question and one would want to attach at least 2 or 4 of these things. The attachment points and orientation of the gage is important so some thought will need to go into this before attaching the gage to either plate. Then designing the experiment and interpreting the results will also require a bit of effort...

So no, it's not as easy as clipping on a sensor and going for a ride, but it's not that difficult either. Judging by the amount of discussion this topic has stimulated this sounds like an experiment well work pursuing.

-momanz

 

Installation is 4 bolts.. i did mine without even jacking it up and had the old one off and the new one installed in like 15 minutes....So easy!!!!

 

I was out for a couple of days. - Had to finish the taxes.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

These things were designed to be used by high-school students . In my experience, the average high-school student h34r: can dish out more abuse than the average Prius.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Yep. That would be condition "A" (see post# 353)

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

It's actually got a strain gauge in it. Likely piezoelectric like dmckinstry suggested.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Agreed. It would be a good start though.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Resolution is 0.03 N. That's pretty sensitive.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Yep.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Yes. In other words, the "at-rest" position in the fixture should not be putting any force on the sensor. Pulling on the sensor (tension) is registered as negative force. Pushing on it (compression) is measured as positive force.

<div class='quotetop'>QUOTE(momanz @ Apr 15 2007, 01:52 PM) [snapback]423661[/snapback]</div>

Thanks for all the input/feedback. Hopefully we can execute some of these experiments.

<div class='quotetop'>QUOTE(dmckinstry @ Apr 16 2007, 09:32 AM) [snapback]423928[/snapback]</div>

Actually, I was talking about the CI-6537. Your picture showed the lower cost one.

CI-6537

The CI-6537 has mechanical force overload protection. The thing is pretty robust. I'm not worried about it being damaged. If we were to exceed 50N, think about it - the worst that would happen is we'd top-out during the measurement. If that were to happen, you'd expect it for condition "A" (no plate), and certainly not for condition "C" (BT plate). If that were to happen, it would be pretty conclusive that the plate is indeed doing something measurable. The experiment would be a success, and Brian would hire us to make a 30 minute info-mercial that would play on channel cable channel 318 at 2:30-3AM every morning.

 

<div class='quotetop'>QUOTE(BethlehemPrius @ Feb 4 2007, 07:37 PM) [snapback]385336[/snapback]</div>

This is my first post. Is the BT Plate the same thing (basically) as Tom's Prius Florr Strengthening Brace available for $280 elsewhere? Do both products accomplish the same thing and fit in the same spot? Does one work better than the other?

 

<div class='quotetop'>QUOTE(UNWIRED @ Apr 17 2007, 09:10 PM) [snapback]425084[/snapback]</div>

Welcome to PriusChat, UNWIRED. Such a wired car for an UNWIRED driver...

They are NOT the same thing. Look back through this thread for pics of the BT Tech brace. As for better, that is an argument I will avoid. Some think the factory plate is just fine, if you read this thread. Others, myself included, detected an immediate improvement in handling upon installation. Too many opinions, choose whom to believe, yourself included.

 

Just a heads-up everyone. Danny has put our BT Tech stiffening plate ON SALE @ 20 dollars off the regular price. I have had a bunch of PM's asking about any sales that might be happening and it is going on now!!

Click at the link at the bottom to go directly to the PC store.

 

For those who are not inclined to read the whole report, you can skip down to “THE RESULT†(This appears two times).


Report:

It is good to see the discussion turning to real world testing.

The BT plate finally arrived after the slowest trip across the land that I have ever witnessed. It, however was FREE. I immediately installed it according to instructions and left on a 1200 mile trip which included curvy mountain roads, freeways, and high speed driving which I did as vigorously as I dared. I came home and repeated the chassis stiffness test which had given strange results (it appeared that the BT plate had weakened the chassis which did not seem possible) so I knew that I must be even more careful.

To those who decide to repeat this test, I can’t emphasize too much the need to be VERY sure that the jack stands do not change height OR location AT ALL during the test or the results will not be accurate. The best way to do that is to do the test all at once. It is a good idea to mark the location of jack stands with tape so their location can be corrected if they are accidentally moved, even a tiny bit.

Central to the claims about the BT Chassis Stiffening plate is that it stiffens the chassis of the Prius. Chassis stiffness can be measured. Unlike the double blind driver test which (if positive) only establishes that the presence of the BT plate can be detected, the measurement of chassis stiffness produces a result which can demonstrate a range of possible performance effect.

If the BT plate does not stiffen the chassis, it remains a mystery how it performs any beneficial results.

The following two cites are provided as authority for the method used for measurement of chassis stiffness. This test follows the procedure used by the first cite almost exactly. The second cite is included to demonstrate that even a more elaborate test is STATIC, rather than a dynamic test.

http://www.flyinmiata.com/tech/twisting.php
http://www.ces.clemson.edu/~lonny/pubs/con...e/sae983054.pdf

First the stock plate is removed and then the car is supported leaving the right rear unsupported. The unsupported weight causes the chassis to twist. The elevation of the top of the opening of the right rear fender in this state is a base line indication of chassis stiffness without the benefit of any plate.

Next, the chassis twist is removed (the car is made level) and the BT plate is installed. Finally, the support at the right rear of the car is removed and the base line measurement of chassis stiffness is compared to the one found with the BT plate installed. If the BT plate has increased the chassis stiffness, the right rear of the car WILL NOW BE HIGHER. The amount which it is higher (if any) is an indication of the increase in chassis stiffness. Please note the range of increase in chassis stiffness in the Miata test (the first cite) for what is a significant change.

This measurement was repeated five times, first without any plate and then five times with the BT plate installed with the chassis being returned to no flex between each measurement.

THE RESULT is:

Each measurement was the distance from a fixed reference point on the carpenter’s square to the bottom of the moveable smaller square (see photograph).

A larger number means less chassis flex or more chassis stiffness. But these numbers are most useful in simply comparing them for divergence. If the groups of numbers overlap, they are statistically the same. If the groups do not overlap it is the extent that they do not overlap which expresses the difference made by the presence of the BT plate.

No plate: 1.35†1.31†1.30†1.30†1.26†Average = 1.30†Var. = .09â€

BT Plate: 1.34†1.26†1.30†1.29†1.26†Average = 1.29 Var. = .08

Third, this test is for perspective. It is the measurement of the amount of chassis flex at maximum flex (which only occurs in very violent maneuvers of the car). It is simply the difference of the height of the top of the opening of the right rear fender between no flex (the right rear is supported at level) and maximum flex (the right rear is not supported and no plate is mounted).

The significance of this is that it gives a “whole†of which any increased stiffness would be the part (expressed as a % of the whole)

THE RESULT is 4.10â€. (Note: this is following the method of cite#1 which is slightly different than that reported earlier in the thread.)
The result with the BT plate installed was an average change of .01†But since this one part in 400 of the total measured chassis flex is located right in the middle of the range of variation of the measurements without any plate installed, the chances are EXTREMELY HIGH that they represent NO CHANGE in chassis stiffness caused by the installation of the BT Chassis Stiffening plate.

Oh, by the way, the car handled fine with the BT plate installed. It handled fine before, too. There was no noticeable change.

I suggest an interesting experiment. Let a couple of those who report especially positive results with the BT plate have theirs removed WHEN THEY DO NOT KNOW ABOUT IT and see if they notice. My bet is that they will not notice, IF THEY TRULY DO NOT KNOW WHEN THE REMOVAL TAKES PLACE.

I was very careful doing this test and my level of confidence in the result is high as a result. The realization that someone will repeat the test and show where you messed up is what keeps you honest and careful when you do tests like this. I really want others to do it. But you must be careful, as well.


Now someone show me that this report is invalid with EVIDENCE.


Photographs follow which support the above text.

 

Well, if the plate does work, it does not appear ^^^ that it works by stiffening the chassis.

I suggested this many pages ago, as did someone else, but they seem to have gotten lost in all the tit-for-tat arguments.

HAS ANYONE TRIED REMOVING THE PLATE (either one) AND SEEING WHAT HAPPENS TO THE PERCEIVED HANDLING?

If the BT plate "improves" the handling so much over stock, SURELY one will notice the difference when there is NO PLATE AT ALL? Isn't anyone with the BT plate the least bit curious to try this?

 

<div class='quotetop'>QUOTE(Les Gas @ Apr 21 2007, 06:51 PM) [snapback]427531[/snapback]</div>

Hmmm. They call it a Chassis Stiffening Plate. Seems kind of odd that nobody until now thought of actually measuring the stiffness of the chassis with and without the plate.

 

Allannde, is there any way to measure vehicle flex evenly from left to right at the center where the plate is instead of just corner to corner? If the factory plate is there to improve handling, perhaps it's function is more subtle than trying to stiffen flex along the entire length of the vehicle. Due to the small size of the plate, wouldn't that be logical to assume (again assuming the factory plate is designed for that purpose)? In other words, could the plate be to reduce flex only in a small area?

What I'm visualizing is - would the plate help reduce flex if you were able to put say 700 pounds vertically on the center console? Or, say press upward on the plate area with a great force? Are the plates strong enough to *very carefully* jack up the entire vehicle from the center and measure any changes at the edge between the doors? I'm going to assume this would be a bad idea. However, it may illustrate how difficult it is to prove whether the product works or not. Perhaps the results of the factory plate were witnessed in the computer modeling of the vehicle design, or maybe it was put there as a last minute solution to a problem that arose during wind tunnel testing.

Just thinking out loud here.

 

Thanks, Allannde. You spent a lot of time and money on this.

Since there's still the possibility that the plate works in some other way, I'd still like to see a double-blind driving test, like some of the LIPOG guys were discussing.

During this whole long discussion, I've been taking my Prius through what I consider some tough handling maneuvers (I'm not super aggressive), and am still pretty happy with the stock plate handling. I've never been out of control in the wind, on a turn, etc. I don't think I need the BT Plate, although the discussion has been fun! But I wish well to those who buy and enjoy their plate. I hope it truly does work for you.

 

<div class='quotetop'>QUOTE(Tyrin @ Apr 21 2007, 10:21 PM) [snapback]427558[/snapback]</div>

I second that!

 

<div class='quotetop'>QUOTE(Les Gas @ Apr 21 2007, 06:51 PM) [snapback]427531[/snapback]</div>

Not me. The improvement with the BT plate seemed real to me. But it also seemed somewhat subtle. I probably couldn't tell one way or another if removing it altogether made a real difference. The plate is on my car, and I'm not going to bother removing it.

I visited Allan this morning, just as he had finished his testing. As he pointed out, he was being very careful, and I have no reason to doubt his results, although I'm sure there will be those here that do. As someone else mentioned, if the plate does actually do something positive, it doesn't seem to be associated with chassis stiffness. Unless there's some other point where it limits flex rather than at the points where Allan has done his testing. He said he's done enough testing though. And, I don't blame him. It has been a fair amount of work.

Dave M.

 

You obbiously have taken a great deal of time to do your testing and I must commend you on that. These measurements that you have taken on your Prius reminds me of when we first came out with our Corvette Chassis stiffening plate. Since then practically every SCCA race car has one of our plates installed on it along with your average Corvette enthusiast!!

Back to the Prius, when we first came out with the plate many similar tests were done and what should be noted is that it is practically impossible to get repeatable measurments due to the settling of the shocks, springs and suspension. Also, as you have already mentioned, what you are trying to measure is the vehicle at rest and not in a dynamic "real world" environment. Simply driving down a road with an average number of ripples in the road surface induces more flex on the body much more than simply jacking it up in ones garage.

We designed the plate to enhance the stability/handling of the Prius in real world driving conditions as many have previously commented on.


<div class='quotetop'>QUOTE(Allannde @ Apr 21 2007, 08:38 PM) [snapback]427502[/snapback]</div>

 

<div class='quotetop'>QUOTE(BT Tech @ Apr 21 2007, 07:07 PM) [snapback]427588[/snapback]</div>

Please read my references, especially the second one. They explain why a static test is valid for this measurement. In fact a dynamic test is not even possible to do with accuracy or in a controlled way. This test is exploring the LIMITS of performance. Actual performance is WITHIN those limits not different from them.

EDIT: This test purposely isolates the suspension and focuses on the stiffness of the chassis since that is the focus of the description of the BT Chassis Stiffening plate. The chassis, of course, is the foundation for the suspension just like a house has a foundation.