Designer Times
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32. Autopia MK VII
In 1967 Disneyland faced a severe problem with the Autopia attraction. The center guide track had made the ride a lot safer, the new MAPO clutch had eliminated the infernal clutch failures, but the Autopia car itself was in dire need of help.
In 1963 the overweight MK V Autopia cars had been replaced by a lightweight MK VI car designed and built by Arrow Development. The MK VI was the first Autopia car which used the center guide type track eliminating the need for wrap around side bumpers, thus saving a lot of weight. But the MK VI had a very basic problem; it was lighter than my old MK V alright, but maybe it was too light to survive more than just a couple of years of kid-bashing service.
Arnold Lindberg, Maintenance Manager, was growing tired of the increasing cost of repairs to these MK VI Autopia cars. Not just replacement of worn parts, but constant welding repairs to the car's basic structure. The Autopia cars are subject to virtually millions of bumper hits over the years. Thus the cars were suffering from fatigue cracks. This happens to many materials that accumulate a number of high-stress impacts or loads over time. Some materials have unlimited fatigue life, other materials have shorter fatigue life, depending on the loads applied.
Explain it this way: If you bend a paper clip back and forth enough times it will break. That's the fatigue limit for that mild steel material at the amount of bending you have been giving it. Take a fiberglass fishing pole. You can bend the dickens out of it for a lifetime and it won't break. That's the nature of some composite materials. But back to the paper clip. If you bend it ever so slightly, it may take months for it to break. See, fatigue life is related to the level of stress AND the number of load cycles.
The real sharp designers know all this and select materials, loads, and design details such that they can predict the life of a product. It's OK for an aerospace missile to be as light as possible because it gets very few, but awfully high loads, then it's life is done. In contrast you'd like commercial aircraft to last a long time, but be as light as possible in order to fly. Other products where weight is not so important can be heavy enough to have unlimited fatigue life. But the Autopia cars must be light enough to be practical, but last a real long time. So what to do?
Arnold Lindberg told me to go take a thorough look at the MK VI problem and fix it NOW. The day I started my inquiry was the day one car just broke it's back and plopped onto the track after getting banged between two other cars. It was bent into a "V" shape. I could see that the welding guys had been welding up the cracks in the steel frame over and over. Then they began to add gussets to reinforce the cracked areas. But this created even more cracks as the impact stress loads were shifted to new places on the frames. Fixing cracks was just a hopeless tail chase with no end in sight. Oh man......NOW what to do?
Disneyland was (12) years old by now, we were on our 6th Autopia car model and the cars still had problems. We started with the MK I first attempt, then the MK V committee car, now we had the purchased MK VI. But still no long term answer for Autopia. I told Arnold that it's time to start over from scratch and I'd like to think about it.
I learned as much as I could about material selection and designing for fatigue life, but the ultimate Autopia car was going to need something very different. I concluded that you can't just figure on the weight of one car hitting the next. What happened on Autopia sometimes is that a pack of (5) moving cars whams into a pack of (5) stopped cars. And that the cars in the middle really take a much bigger hit. And that they get the hit diagonally across the chassis. This means that the chassis is getting a whack in a sheared manner. No wonder that a conventional auto structure has a short life.
No way are we gonna get a light weight long life car in this situation with a regular design. Why not make the chassis flex a bit with each hit? Why not clamp the frame parts together with a flexible element between the hard elements? Why use rigid frame rails when we could use flexible frame rails? That would be easy if I made the frame rails bent into a curvy "cow belly" shape. And since most weld failures occur at what is called "cantilever" joints, why not eliminate cantilever joints?
Ask a material what it would like. It will tell you.....pull me, maybe push me, but don't bend me. Try that with a paper straw. Bending behaves OK if the bending load is distributed around a bit. But a cantilever joint gets big loads all concentrated at one place.....not good for unlimited fatigue life. You can't eliminate all cantilever joints, but I could get rid of all but a few in a new clamped flexy frame arrangement. I also wanted to return to the concept of a quick change drive unit incorporating the engine, clutch, drive belts, and drive axle. Only this time we would bite the bullet and make the drive unit structural parts from cast aluminum. We could integrate a lot of assembly details into a real slick (but expensive) deal.
With this basic philosophy adopted, the rest of the detail production design progressed rapidly. I assigned a young new engineer, Tim Kelley, to take charge of all the engineering drawings and follow up construction of one prototype new Autopia MK VII car. Meantime I designed a sports car styled body to fit on the chassis. (designed in mid 1967, it looked like the 1968
Corvette) Rather than bolt the body on, why not just let it sit on some indexing features on the chassis and hold it down with (4) flexible hood latches? Now the body would never take a hit and you could quickly lift it off for chassis service. We added a number of nice features such as a flex mounted front axle, enclosed rack and pinion steering, and a large custom molded plastic fuel tank.
The prototype Autopia MK VII was built and tested for a few months. Everyone approved the car for production, but then a funny thing happened. The car would cost WAY TOO MUCH. Not just to build it, but when the "development expense" was amortized over the first production run, the price was not approved. Seems there was some "inaccuracies" in job cost accounts accumulated to the MK VII that ballooned the cost. Since the fiscal year accounting had already been reported, the cost structure could not be changed. Roy Disney personally solved the problem when he visited the MAPO shop and listened to the pleas from Disneyland management as to how badly they needed this new car so as to reduce the high maintenance costs. "Build it" he said.
MAPO built around (80) cars for the first production run, then a bunch more for Disneyland and Walt Disney World were built by Arrow Development. Thirty five years later Arrow Development's Ed Morgan admitted that the cheapest Autopia car turned out to be the one that was so expensive to build originally that he thought Disney was nuts. This was the second chapter in the economic reality of spend a lot up front rightly, save a bundle later.
Had someone told me than that the basic Autopia MK VII would still be running (35) years later, I would probably have flinched. In 2000 as Disneyland re-dedicated an all-new Autopia attraction complete with a fleet of cute "all-new" Autopia cars, few guests knew they were still driving the ancient MK VII chassis, but with a more modern engine and slick electrical starting system. I was invited to take the "first official spin" on dedication day. The body was new, but the bones were the same. Only I could appreciate the change of design thinking that we went through way back in 1967.
oOo
Next month: WDW MK IV MONORAIL
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-- Bob Gurr
Bob Gurr began working with Disney in 1954. He retired in 1981 but occassionally consults for the Company. Since Disney he's worked on the sinking ship at Las Vegas' Treasure Island, Universal Studios' King Kong, Godzilla for the film by the same name and much more. Among his proudest accomplishments he lists "making Walt tickled pink that some of the things he wanted to build actually worked. You could tell how proud he was when he would show off things to his friends and the press. Lincoln and the Monorail were two big ones for him."
Designer Times is normally posted the second Wednesday of each month.
The opinions expressed by Bob Gurr, and all of our columnists, do not necessarily represent the feelings of LaughingPlace.com or any of its employees or advertisers. All speculation and rumors about the future of Disneyland and the Walt Disney Company are just that - speculation and rumors - and should be treated as such.
-- Posted December 11, 2002
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