Senator ask NHTSA to revisit allegations of Toyota Safety concerns

Gilbert made a hypthesis and tested it with a resistance box. What he didn't know at the time (or document in in his paper) is a mechanism that can introduce random, variable resistances. The NASA papers on 'tin whiskers' document mechanism which is both random and variable and found in a Camry encoder. What is missing is a survey of tin whisker populations in Toyota encoders.

I had a small sample set, four, but poor tools. So I used a wall wart to test the tin whisker hypothesis. Pre and post testing indicted the wall wart burned out the tin whiskers. These were encoders from accelerator assemblies that had been sent for replacement by a refurbished unit.

Like the old story of the chicken and pig who had shared a breakfast of eggs and ham, the chicken was interested but the pig committed. I'm interested in a survey of a larger set of encoders but I'm not committed to a further investigation. So I can agree with Sen. Grassley on this one issue but not enough to contact his office. Grassley has shown himself to be untrustable in his dealings and not terribly bright.

Bob Wilson

 

NHTSA responds:

Source: Government’s auto safety chief says Toyota acceleration troubles were investigated properly - The Washington Post

Hummm, there is some careful word-smithing going on here.

Bob Wilson

 

there is nothing careful about it, it tells you exactly what they did and what they found out... dont be a tool.

 

Sorry, I should have been more specific and identified the weasel words:

• "several electrical shorts" - the number is two per the Gilbert protocol
• "“tin whiskers” might cause a small throttle opening" - this is not a technical answer. Tin whiskers have specific electrical characteristics, ~200 mv will burn them out. However, they generate random, resistances and often exhibit non-linear effects. A technical answer would be something along the lines of all throttle position voltages exceed 200 mv and would burn out any tin whisker.
• "NHTSA is not aware . . . " - but NASA may have a clue and example.

NHTSA has ceased to look for tin whiskered accelerators which ensures they remain "not aware."

The NHTSA needs to gather every failed, dual-pot, accelerator replaced by Toyota and open each encoder to characterize the tin whisker population. In parallel, they need a technical report from Toyota showing the expected voltage and Thevanized/Nortonized drive circuit. Then using a Monte Carlo model, run enough cycles to quantify the risk.

The model and study should report:

1. population density of 'tin whiskers' found in the population of encoders
2. estimated growth rate - based upon manufacture and observation dates
3. Active areas that can grow tin whiskers
4. percentage of areas between conductors that could form a Gilbert bridge
5. percentage of areas where the circuit would vaporize a tin whisker - compare theory to observed

I suspect the probability of tin whisker induced, run-away acceleration is very small but not zero. But you don't know unless the NHTSA:

• quantifies statistically valid populations of whisker at-risk encoders
• matches whisker characteristics to electrical characteristics
• models the problem and runs enough simulations to give quantifiable results

The weasel words say he has given up without providing details to show the NHTSA has done an adequate job. Given the malarky they used to justify adding noise makers to our Prius, I'm not surprised. Those who would use 'junk science' for you will also use it against you.

Bob Wilson

 

No, it specifically says that they investigated it and found it not to be a problem.

Why do you assume that they didnt? It is pretty funny. I would think their investigation to be very thural, but you dont give a technical explanation to the Senator, thats just silly.

Their PR clearly states that they investigated it, and they found it not to be possible in real life situations. They also said that when they reproduced the issue, it didnt cause open throttle scenario. And that every incident that happened was investigated and found nothing to have to do with tin whiskers.

What are you doing here is gasping for straws, just like that idiot Gilbert, who is not an idiot, since he gets paid handsomly by ambulance chasers for his work.

Why would NTHSA head honcho who said that every Toyota owner should park their car and not drive it, help Toyota. He built his career on being hard on Toyota.

To me it is pretty obvious that tin whiskers are well know and investigated in the automotive world, and that there doesnt seem nothing unknown about it.

But lets invent something and lets make Toyota prove a negative - something thats not possible to do. Since they cant prove that there is an problem. How ridicilous is that?

If i was Toyota, I would start suing all these people. Gilbert's stunt on ABC had nothing to do with engineering or professionalism, he seems like a witch doctor and not engineer. Presenting himself as automotive safety expert/group is a sham that can easily be proven.

 

It suggests they are no longer looking at the tin whisker hypothesis. One way not to see a problem is to stop looking.

If the NHTSA has a more complete and through report on the tin whisker investigation, I'm more than willing to read it. I've simply outlined the type of investigation that would satisfy my engineering curiosity.

I've read the Gilbert report and the Toyota funded independent report on Gilbert's work. What was missing from both was a through analysis of the tin whisker hypothesis. It wasn't until I read the GSFC tin whisker team analysis of the Camry encoder that I realized it had not been throughly vetted. I have unique experience in this area having rebuilt about a dozen accelerator encoders.

Earlier this year after reading the GSFC tin whisker reports, I used a 12V wall-wart on four of the encoders to see if I could 'burn out,' change the characteristics. Sure enough, three of four no longer exhibited the symptom of a failed accelerator. This change is consistent with the tin whisker hypothesis.

As Gilbert and the Toyota reports showed, a single fault is most likely to result in the vehicle going into a 'safe home' mode ... we call it "the big hand syndrome." The single fault can be temporarily 'cured' by parking the car and rapidly cycling the accelerator but it comes back. This is something identified in the GSFC tin whisker report.

The only known accelerator fix is to disassemble the encoder, clean it throughly, and reassemble it. But I've never seen the whiskers because I never used a microscope to look for them. It sounds like the NHTSA has stopped looking.

Gilbert showed one of the two faults can be induced without triggering the 'safe home' mode. A second fault then leads to the acceleration. What no one has reported, yet, is a circuit and probability analysis of the tin whisker hypothesis. Tin whiskers can be burned out with 200 mv if the circuit has a low enough impedance.

I suspect the probability of tin whisker acceleration is a vanishingly small number that for 100,000 vehicles would be measured in centuries with the rate increasing over time with the growing population of whiskers. But no one has done the experiment or analysis to quantify the effect. It would be a fascinating paper especially if submitted to the SAE or other professional societies.

Bob Wilson

 

We already know it's because of driver error, I'm satisfied with the conclusions indicating it as such.

 

I do believe that the great majority of them are driver error, but it is not reasonable to declare that we know all of them to be such.

Today, Mazda joins Ford in a recall concerning a stuck throttle / uncontrolled acceleration problem the really does have a mechanical cause:

Mazda joins Ford with throttle recall