BT Tech Stiffening plate

donee · Sep 29, 2007

<div class='quotetop'>QUOTE(Dr Malarkey @ Sep 28 2007, 02:31 AM) [snapback]518879[/snapback]</div>

Interesting concept Dave. 70% you say? I'd love see your math on that.
[/b]
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Well,

There are two ways to look at it.

One is a plate without machined features, of the same mass as the machined plate. It would be allot thinner, which would reduce the moment of ineritia of the plate section. This plate would twist and/or bend easier.

A plate the same thickness as the BT-Tech plate, without the machined features, would be stronger than the BT-Tech plate, but somewhat heavier.

A corrugated surface would increase stiffness for the same weight of material. So, a next generation BT Tech plate (if Toyota ever figured out they needed such a thing), might be made from extruded stock, with a corrugated surface. The production volume would have to be quite large to pay for the extruder die.

Aces · Sep 29, 2007

<div class='quotetop'>QUOTE(donee @ Sep 29 2007, 09:48 AM) [snapback]519008[/snapback]</div>

Well,

There are two ways to look at it.

One is a plate without machined features, of the same mass as the machined plate. It would be allot thinner, which would reduce the moment of ineritia of the plate section. This plate would twist and/or bend easier.

A plate the same thickness as the BT-Tech plate, without the machined features, would be stronger than the BT-Tech plate, but somewhat heavier.

A corrugated surface would increase stiffness for the same weight of material. So, a next generation BT Tech plate (if Toyota ever figured out they needed such a thing), might be made from extruded stock, with a corrugated surface. The production volume would have to be quite large to pay for the extruder die.
[/b]
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No, I think you are missing the point that Dr Malarkey was making. I work at a company that machine's steel to make parts (Gears). So what I see the question as is: to make the plate, BT-Tech buys a plate of a certain thickness and machines away aluminum, while leaving the "X" pattern. So what if you skip that machining step? The result is less machining time, thus cheaper to make. The stiffness should be slightly stiffer. But it would weigh more. It's all in your frame of reference when looking at the question.

Rae Vynn · Sep 29, 2007

Okay, Brian... I've ordered my plate

Finally talked myself into making that investment...
Maybe when it arrives, DH will install the mudflaps at the same time

donee · Sep 29, 2007

<div class='quotetop'>QUOTE(Aces @ Sep 29 2007, 12:36 PM) [snapback]519019[/snapback]</div>

No, I think you are missing the point that Dr Malarkey was making. I work at a company that machine's steel to make parts (Gears). So what I see the question as is: to make the plate, BT-Tech buys a plate of a certain thickness and machines away aluminum, while leaving the "X" pattern. So what if you skip that machining step? The result is less machining time, thus cheaper to make. The stiffness should be slightly stiffer. But it would weigh more. It's all in your frame of reference when looking at the question.
[/b]
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Hi Aces,

Yes, of course.

Stiffness and strength are two different things. Strength is when the material permanently yields. Stiffness is how much force it takes to deflect a unit amount.

If your designing a part to have the best stiffness/weight ratio, you machine it away like BT Tech did. Or your extrude it with lots of surface corrugations. With extrusion you can save allot of material as there is only post extrusion machining waste. A prismatic plate might very well work in this application, but it wont be as stiff for the mass of the plate.

There is no rule when you start designing something that its going to be so thick. You have to figure it out why it should be this thick, or that thin.

Is milling cheaper than drilling? To make the plate stiff, for its weight, you could just drill a bunch of holes. The extra surface area makes it more stiff than the equivalent mass thinner prismatic plate. This is kinda a takeoff on using tubing than solid bar, but in rectangular form, rather than cylindrical.

The other thing is the thin webs that the bolts squeeze the plate to the vehicle. I imagine they are thin to avoid damaging the car's frame, and to give the bolt heads a pocket to reside in. If you make the plate too stiff, those thin webs crack. If you do not put in the bolt hole pockets, the car frame cracks.

It could be the bolt heads that transfer the major forces to the plate, too.

Then again, Brian might have just designed it to look pretty. Hard to say. Whatever, it seems to work.

BT Tech · Oct 1, 2007

Congrats!! Please let us know how you like it once you get it installed.

<div class='quotetop'>QUOTE(Rae Vynn @ Sep 29 2007, 02:18 PM) [snapback]519113[/snapback]</div>

Okay, Brian... I've ordered my plate

Finally talked myself into making that investment...
Maybe when it arrives, DH will install the mudflaps at the same time
[/b]
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We went through several iterations until we settled on the current design. FEA (Finite Element Analysis) was done on our BT Tech plate and further changes were made to increase its strength and stiffness with a minimal weight penalty.

The fact that it looks cool is just frosting on the cake!!

<div class='quotetop'>QUOTE(donee @ Sep 29 2007, 03:46 PM) [snapback]519142[/snapback]</div>

Hi Aces,

Yes, of course.

Stiffness and strength are two different things. Strength is when the material permanently yields. Stiffness is how much force it takes to deflect a unit amount.

If your designing a part to have the best stiffness/weight ratio, you machine it away like BT Tech did. Or your extrude it with lots of surface corrugations. With extrusion you can save allot of material as there is only post extrusion machining waste. A prismatic plate might very well work in this application, but it wont be as stiff for the mass of the plate.

There is no rule when you start designing something that its going to be so thick. You have to figure it out why it should be this thick, or that thin.

Is milling cheaper than drilling? To make the plate stiff, for its weight, you could just drill a bunch of holes. The extra surface area makes it more stiff than the equivalent mass thinner prismatic plate. This is kinda a takeoff on using tubing than solid bar, but in rectangular form, rather than cylindrical.

The other thing is the thin webs that the bolts squeeze the plate to the vehicle. I imagine they are thin to avoid damaging the car's frame, and to give the bolt heads a pocket to reside in. If you make the plate too stiff, those thin webs crack. If you do not put in the bolt hole pockets, the car frame cracks.

It could be the bolt heads that transfer the major forces to the plate, too.

Then again, Brian might have just designed it to look pretty. Hard to say. Whatever, it seems to work.
[/b]
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JimboJones · Oct 1, 2007

Seems to me that there is a way of measuring whether the BT plate makes any difference at all to the car's chassis stiffness, but I need volunteers both with and without BT plates...

First of all, I'll assume that the increased stiffness that the BT plate is addressing is in the torsional direction along the length of the car, i.e. "twisting" the chassis between front and back. The position and geometry of the BT plate can only address this torsional stiffness. This "twisting" should be what people feel when going along rough roads, turning corners or experiencing cross winds.

So, for those wanting to volunteer, the experiment is pretty simple. To ensure as much similarity between all Prius test cars as possible,
1. Make sure that your car is empty of cargo and other heavy stuff
2. Do the experiment with a full tank of gasoline
3. Use the lifting jack supplied with your car
4. Make sure all your tires are pumped between 35-40 psi

The experiment:
1. Use the lifting jack to raise the driver side rear wheel, until it just clears the ground. Position the jack where the manual indicates it should go.
2. Measure the distance between the bottom of the car below the rear door, at the point between the jack and the rear wheel well, and the ground (call this A), see picture
3. Measure the distance between the bottom of the car below the front door, just next to the front wheel well and the ground (call this B ), see picture
4. Calculate the difference
5. Do the same on the passenger side, jack up the passenger side rear wheel and do the same measurements on that side.

The theory is that with the BT plate on, the increased torsional stiffness of the car should mean that the difference between distances A and B will be less (because the chassis will twist less), than for those cars without the BT plate.

I'll do the experiment myself and post numbers here for the OEM plate. Any volunteers, please do likewise - even if only out of curiosity!

IsrAmeriPrius · Oct 1, 2007

<div class='quotetop'>QUOTE(JimboJones @ Oct 1 2007, 06:26 PM) [snapback]520091[/snapback]</div>

Seems to me that there is a way of measuring whether the BT plate makes any difference at all to the car's chassis stiffness, but I need volunteers both with and without BT plates...

First of all, I'll assume that the increased stiffness that the BT plate is addressing is in the torsional direction along the length of the car, i.e. "twisting" the chassis between front and back. The position and geometry of the BT plate can only address this torsional stiffness. This "twisting" should be what people feel when going along rough roads, turning corners or experiencing cross winds.[/b]
Click to expand...

Such a test has already been conducted. You can find the discussion on the BT Tech Stiffening plate thread. Specifically, post #412.

I do suggest that you read the rest of the discussion, especially these posts by a mechanical engineer experienced in automotive frame strength tests:

<div class='quotetop'>QUOTE(Ken Stewart @ Apr 24 2007, 09:53 AM) [snapback]429069[/snapback]</div>

I have been reading these BT plate discussions for close to a year now and although I have responded to a number of posts I feel it is time that I put my mechanical engineering degree that I earned back in the 60's to good use.

I worked for a company in Michigan that specialized in designing high strength steel and structural components for all of the big 3 automakers (back then at least) One of our jobs at the time was to measure the strength of the frame of a certain Ford vehicle, (which one I don't remember.) The methodology used at that time was for us to take this frame to a company that specialized in taking these measurements and that is all they did. This company had a special fixture for attaching the frame to a Rota table concrete structure and then measuring the deflection of the frame at over 240 points along the frame. We would then make our modifications and the test would repeat, often taking 6-8 hrs per test In this time, the frame would be rotated at different angles to simulate loading. It was imperative that the frame was mounted in this fashion. At all of the measuring points, we were able to measure the results in .0001"! These tests were often very expensive and even the auto manufacturers often balked at the bills they got for executing these tests.

I have read Alan's data and although I give him a lot of credit for going through all of this to conduct his own tests, I am sorry to have to say but the methodology is completely wrong and subject to many errors and inconsistent results. When you are measuring a chassis, frame or a uni-body structure, you can not have the wheels or any other compression type devices coming in contact with the ground to achieve accurate results. This is why when we tested the frames we had to bring the car to the facility and the cars actual frame/body was bolted to the concrete barriers. This was done so that there were no outside forces like the tires, springs, shocks and struts that compress and expand making any measurements suspect at best. In addition, the testing should be done on 3 axis that can induce loads to the structure, none of this was done in Alans test.

It is my opinion that Toyota added the brace in that location because they knew there was significant flex occurring in the latter portion of the vehicle's structure. To say it was there because there was a battery sitting on top of it is horse manure.

The company I worked for later went on to do testing for race car sponsors and it was imperative that they had the best/stiffest chassis so that the cars of that day could withstand the 1+ G turns of that era. In order to test these chassis' with a degree of precision, we built a device that we called a twist fixture and would attach this to the chassis but again we would attach the fixture to concrete and the actual fixture would suspend the chassis in order to get accurate measurements. What was great about this fixture is that we could simply lower one side using a type of tie-rod end to lower or raise the chassis with great precision and measure the deflection at number of points along the chassis. The fixture was also able to be rotated so that additional forces could be placed during the measurement process and documented.

To sum all of what I have just written here are my findings:

The test by Allan although well meaning was conducted incorrectly and the results in his own admission showed inconsistencies. He also conducted no tests of the effect of compression while measuring the amount of deflection anywhere on the body under amy type of load. The methods used for measuring were not proven to be scienfiically accurate and the person (Alan) in this case is not known to be proficient in using scientific meausring tools (un-calibrated) with an unknown degree of accuracy.

A vehicle in motion is also affected by outside forces such as road surfaces, gravitational loads (g-forces) and aerodynamic forces which put additional loads, (sometime great amounts) on the vehicles body. Having a part that stiffens the body would counteract these effects to an extent. The more stiffening the part provides, the greater the result will enhance the differences the driver feels.

I never claimed to be a race car driver but there is no doubt in my scientific mind that the BT plate is providing a stiffening effect on the body of the car. This would explain why the car feels more stable to me when driving it. What is in question is the amount of stiffening that the BT plate provides and I personally do not have the inclination or financial ability to dive into that.

Best,

Ken Stewart [/b]
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<div class='quotetop'>QUOTE(Ken Stewart @ Apr 24 2007, 05:33 PM) [snapback]429398[/snapback]</div>

I earned my M.E. degree in 1966 and went on to work for more companies than I care to remember. The company where I designed strucural reinforcements was the same one where we did the tests on vehicle structures. I worked there from 1978-1989 so we worked on everything from full frames to unibody structured automobiles. While at this company we had many major corporate customers includng the Big 3, Honda, Nissan and Porsche to name a few.

In response to your post, you are never going to see a deflection of 1/2-1"! A 1" deflection is huge and would be indicitive of either a very poorly designed body or something that was in the process of structural fatique/failure.

Often at times when we made changes to a cars frame/body the associated change would show a deflection differential of less than .02" which sounds like a very minor amount but when measured at the contact patch of where the tire meets, this improvement can translate to a tremdous increase in overall TR! This is why I mentioned earlier that not only does the structure have to be secured in such a way but the accuracy of the measurements must be calibrated to a known standard and the person taking such measurements must be qualified to do so.

Things have changed drastically in the automotive world and manufacturers typically rely upon resonant frequency measurements where the vehicle structure is placed in anechoic chamber and the point at which the structure begins to resonate is a definitive test to know the actual stiffness of the product they are testing. The higher the resonant frequency the stiffer the body and vice versa. These tests can also be conducted on high speed computers using complex software where it can detect to a great deal of precision what the resonant frequency of the structure will be. Often times the manufacturers will still test the structure for confirmation but computers have saved engineers a vast amount of time and at the same time money.

As I mentioned previously I think it is great that someone went through the effort to conduct this test however I feel it is my duty as a M.E. to point out the flaws on how the test was performed and that the results whether they were positive for the BT plate or negative against it serves no real purpose other than to say that someone actually did a test.

What I can appreciate about the plate is its simplicity and overall quality. The machining of this part is first rate and I am honestly suprised that they are able to offer it as inexpensively as they do.

In response to Allans post inviting me to do further testing, I will leave that to you younger guys. I really do not feel the need to test something that I already know works as I have a lot more important things to do like relaxing out by my pool.

Best

Ken Stewart[/b]
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Presto · Oct 2, 2007

Jimbo, if you are interested in the plate, i'll sell you my used one for $120 plus shipping. It's been sitting on my dinner table for awhile, and although it looks nice, it's definitely not having any noticeable effect on the table.

windstrings · Oct 2, 2007

I always find it comical anymore to see when someone decides the plate needs to be "proven" as if its in question any more!......

There is so much history on this plate of totally impressed customers and totally squashed skeptics, I can't believe anyone has the guts to try and do what no-one else has been able to do before.... and thats to "disprove" the plate works!

I know some folks will say they are not trying to "disprove" it, but rather "prove" it works.... but the proof is the long long history of converted skeptics and satisfied customers!.....

I've come to the conclusion that all those who will not believe such a great number of witnesses, also will not believe any test from any other "witness".... they have to prove it to themselves, but usually those people are paralyzed by fear and cannot or "will not" buy the plate so they can "prove or disprove" it to themselves..... LOL!

So here we go with the same issue, figuring out a way to prove it works "before" buying it...... how many times do we have to play this game before its "proven"?

Again... this is quite comical!

JimboJones · Oct 2, 2007

<div class='quotetop'>QUOTE(IsrAmeriPrius @ Oct 1 2007, 11:56 PM) [snapback]520142[/snapback]</div>

Such a test has already been conducted. You can find the discussion on the BT Tech Stiffening plate thread. Specifically, post #412.

I do suggest that you read the rest of the discussion, especially these posts by a mechanical engineer experienced in automotive frame strength tests:
[/b]
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Ah, finally - done and done.

Cheers!

By the way, what happened to the suggestion of changing the topic to nitrogen in tires?

BT Tech · Oct 4, 2007

Some Excellent information there..... Thanks for the post IsrAmeriPrius!!

<div class='quotetop'>QUOTE(IsrAmeriPrius @ Oct 1 2007, 11:56 PM) [snapback]520142[/snapback]</div>

Such a test has already been conducted. You can find the discussion on the BT Tech Stiffening plate thread. Specifically, post #412.

I do suggest that you read the rest of the discussion, especially these posts by a mechanical engineer experienced in automotive frame strength tests:
[/b]
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Boo · Oct 4, 2007

<div class='quotetop'>QUOTE(BT Tech @ Oct 4 2007, 12:59 PM) [snapback]521235[/snapback]</div>

Some Excellent information there..... Thanks for the post IsrAmeriPrius!!
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I second that. Thanks.

Wish someone would go through the 970+ posts on this thread, and pull out the 10 most useful and informative ones ... sorta like a Greatest Hits compilation for the holidays.

apriusfan · Oct 4, 2007

<div class='quotetop'>QUOTE(Boo @ Oct 4 2007, 10:12 AM) [snapback]521241[/snapback]</div>

...Wish someone would go through the 970+ posts on this thread, and pull out the 10 most useful and informative ones ... sorta like a Greatest Hits compilation for the holidays.[/b]
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Kind of like a thread-specific FAQ?

Rae Vynn · Oct 4, 2007

<div class='quotetop'>QUOTE(Presto @ Oct 1 2007, 09:04 PM) [snapback]520145[/snapback]</div>

Jimbo, if you are interested in the plate, i'll sell you my used one for $120 plus shipping. It's been sitting on my dinner table for awhile, and although it looks nice, it's definitely not having any noticeable effect on the table.
[/b]
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Oh, sure... NOW you say that, AFTER I paid full price for one!!!

Presto · Oct 5, 2007

^^^
Sorry! My cousin just told me, recently, that he didn't want it.

apriusfan · Oct 5, 2007

Brian, you have been too quiet.... What is the update on the new products? Christmas is fast approaching....

BT Tech · Oct 7, 2007

Trying my best to get our next 2 products ready in time for the upcoming holidays. Like I mentioned in the past, manufacturing quality machined products is not an easy task!!

The peformance results and quality will be well worth it.... NO Made in China here!!

<div class='quotetop'>QUOTE(apriusfan @ Oct 5 2007, 12:41 PM) [snapback]521818[/snapback]</div>

Brian, you have been too quiet.... What is the update on the new products? Christmas is fast approaching....
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efusco · Oct 7, 2007

Have you mentioned what the new products will be? I'd like to review the 972 prior posts...maybe I'll take some vacation time!

apriusfan · Oct 7, 2007

<div class='quotetop'>QUOTE(efusco @ Oct 7 2007, 10:11 AM) [snapback]522458[/snapback]</div>

Have you mentioned what the new products will be? I'd like to review the 972 prior posts...maybe I'll take some vacation time![/b]
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I don't remember at what post count the cat snuck out of the bag, but.... One product was confirmed to be a skid plate to protect the underside of the HSD bits. The other hasn't quite been fessed up to but is something that complements the BT plate.... Whether the complementing happens on the rear or the front is unanswered; but it would seem to be a stiffener of some sort for the front or an additional stiffener for the rear.

patsparks · Oct 7, 2007

<div class='quotetop'>QUOTE(Presto @ Sep 20 2007, 03:50 AM) [snapback]514875[/snapback]</div>

Hey Pat,

How's your experience with the BT plate, so far?
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Sorry about the slow reply, I was away for a week when this was posted I think and missed it.
I haven't noticed a big difference in the feel or handing of the car but I never had much of a problem in the first place. I have a feeling the Australian Prius has stiffer suspension than the US version but having never driven a US one I'm only going on anacdotal evidence. I drive in metropolitan Adelaide which doesn't have expressways or freeways everywhere although I have a 6km section of expressway each way to and from work except on weekends (it is a reversable one way road). Total journey is 35km each way. I hate slowing for corners so avoid it by cornering much to fast. all but the tightest left hand corners are taken at about 40 or 50km/h.
There may have been a slight improvement in cross winds, I have driven in a couple of bad storm winds and the car was easy to keep straight.(hey! maybe that is my sharkfin?)
I might brace the front strut towers next, not sure. Currently trying to find a supplier of racing dome wheel covers here in Australia.

I might join the DLRA (Dry Lake Racers of Australia) and try out the prius on the salt lake about 600km north of Adelaide. The club meets once a year on lake Gairdner with competitors from around the world, well Australia and USA. I'd love to run the Prius through the traps and get an official top speed for a dead stock drivetrain, maybe with taller tyres fitted. I bet that will bugger up my average L/100km!

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