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MAX Update No. 27: The 5,000 Mile Inspection

4/9/2009 12:22:26 PM

Tags: MAX, 100 mpg, engine, Kubota, maintenance, Auto X Prize

Thanks to y'all for the great response to my horsepower question in Update No. 26. We'll be trying several of your suggestions and reporting back here with the results. But first, MAX is getting a major examination.

In these modern times when some cars get their first service at 100,000 miles, it may seem odd that we're tearing MAX down for a look-see with a modest 5,160 miles on the clock. But I've got my reasons.

For one, I cut my teeth on aircraft, and a 100 hour/annual (whichever comes first) inspection is par for the course in the aviation biz. Mind you, if your car starts making a funny noise you can pull over and call for a tow truck — but that’s not an option for pilots. So they want to know if something has funny noise potential before the actual noises announce themselves.


Kubota engine 
Photo by Jack McCornack

It's a habit I've carried over to the road: My cars tend to be what the used car salespeople describe as fully depreciated, or beaters, or experimental ... Well, if I knew exactly what they were going to do, there'd be no point in building them, would there? Anyway, giving my cars an “annual” keeps me from wearing out my AAA card.

For another reason, 5,000 miles is long enough that gross design errors are likely to have left their mark. My biggest concern was that the transmission adapter might have a design flaw. Otherwise, believe me, I wouldn't have bothered pulling MAX's engine out of the chassis at a mileage mark where other people are thinking about changing their oil.

What defects was I expecting? Well, if I knew that, I wouldn't have to look, but one possibility was fatigue cracks. Every engine revolution vibrates the connection between the engine and transmission by one cycle. I could do the math and calculate how many vibration cycles there are in a mile, but it's easier to do a horseback guess based on hours. Let's see ... 5,000 miles is about 100 hours, figuring an average speed of 50 mph. Figuring an average RPM of about 2,000, 2,400 or so, times 60 miles per hour, that's 120,000 to 144,000. We'll be conservative and go with 120,000 cycles. That times 100 hours is 12 million vibration cycles — enough time for cracks to develop and grow if they're going to happen. They didn't.

It's also long enough for misalignment to show itself by unusual clutch or bearing wear. But it all looked good in there and appears ready to go another 50,000 miles before it gets another peek, and another 100,000 miles before the clutch disk wears out.

The only thing I didn't like is it's a bit dirtier inside than I'd prefer. But that’s all my fault; I left a big gap when I notched the bottom of the transmission bell housing so I could fit this powerplant in the Corrode Warrior (see MAX Update No. 7). I'm very happy with how this adapter is holding up, happy enough to make one for you if you want to make your own MAX, or for whatever Kubota/Toyota project strikes your fancy.


Browse previous MAX Updates.
Read the introductory MAX article, Here Comes the 100-mpg Car.
Visit the Kinetic Vehicles website for more technical details on MAX.

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