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#11
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Which Tow Vehicle
On Oct 8, 11:43 pm, Bob C
wrote: Which vehicle to tow a glider trailer has been debated ad nauseum on RAS. I have always been a staunch supporter of towing with a full-size truck. After the events of last Thursday, I feel my position is vindicated. I was towing my sailplane westbound on Interstate 40 near Gallup, NM. I had just come through a nasty rain & hail storm bad enough that traffic had been stopped completely for several minutes. The worst part of the storm passed quickly, but there was still moderate rain as traffic began moving again. I was up to about 40 MPH when an eastbound GMC Yukon lost control and spun into my westbound lane. I managed to get nearly stopped before he spun head-on into me. Despite major damage to both vehicles, all 7 occupants (me + 6 in the Yukon) walked away completely unhurt! My sailplane and trailer suffered absolutely no damage. My wife arrived about 2 hours later with the backup truck and I was able to continue to the airshow in Kingman, AZ. A very thorough inspection of the sailplane before assembly showed no indication at all of the crash. The items in the seat pan were undisturbed, the G-meter still showed the levels from my last aerobatic flight and there wer no indications of any bumping or scuffing anywhere on the wings or fuselage. It was an emergency stop, downhill on very wet pavement. About the worst possible scenario for a controlled stop with a trailer. I hate to think what would have happened if I'd been towing with a VW or Z3. Here's the link to a photo of the crash (Mine is the white Dodge, the trailer isn't visible in the photo). http://www.silentwingsairshows.com/images/wreck.jpg Despite the fact that he was driving a $40,000 Yukon, the other driver had no insurance (or job, or phone number, ...), so my uninsured motorist coverage will cover the damages, while Mr. Ortega and family walk away with nothing but a pair of citations for driving too fast for conditions, and no insurance. I'm already looking for another truck. Bob C. Bob, Glad you're okay. That must have been pretty scary. (in any vehicle) Bob |
#12
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Which Tow Vehicle
On Oct 9, 11:00 pm, tommytoyz wrote:
Bob, You have to remember that your vehicle was badly damaged BECAUSE it weighs so much. The frame of your vehicle had to absorb your weight. A lighter vehicle would not have to absorb as much energy to come to s stop, as it weighs less. And absorbing energy the principal reason why, in a crash, it is better to be in a steel vehicle than aluminium, and GRP or composites are worst of all. After all, we sit on energy absorbing cushions for a very good reason. It doesn't matter if the vehicle hits an immovable object or if you get hit by a moving object from the front. The calculation is the same for your vehicle to come to s stop or decelerate. The mass your vehicle plays a very important role and the heavier it is the more energy needs to be absorbed and the more damage there will be. While true, that's only half the story. If you remember you schoolboy/ girl physics, you will realise that in a collision kinetic energy is *not* conserved whereas momentum *is* conserved. (The "missing" energy appears as heat and sound So what? Well, if you think through what happens in a collision between vehicles with different mass, and use conservation of momentum, then the lighter vehicle will experience a greater delta-v than a heavier vehicle. And consequently the lighter vehicle will also experience a larger acceleration than the heavier vehicle. That's rather important to the occupants, since it is principally the acceleration that determines how much brain damage they sustain. So to compare the damage to your truck and say that this would happen to a lighter vehicle is just plain wrong. A lighter vehicle would sustain less damage is constructed the same as the truck. Yes, but what about the occupants? The fact of the matter is though, that lighter newer vehicles can absorb more energy per pound than heavier vehicles and thus would sustain far less damage than a heavier vehicle. Why is that? I've no reason to doubt you, but why? I've seen a crash test of a smaller Renault against a Land Rover and the Land Rover was in worse shape after the head on collision test - especially the occupants. So safety design and weight are the biggest factors in survivability. All things being equal, it's safer to be in a lighter vehicle in a crash as there is less energy for the frame to absorb. That's the first time I have seen that statement. The Ford F-150 is one example. And can your truck's roof even hold the weight of the truck should it over turn? Light vehicles don't have this problem and have a lower CG as well. Probably true, and important in some cases. Your breaking power is also less than a lighter vehicle's - contrary to what many may think, again because of the heavier weights. Stopping distances are less in a lighter vehicle - always. If the lighter tow vehicle has good breaks, Highly ambiguous in this context I think you mean "brakes"! like most modern smaller cars do and good tires, that are not that much smaller than your truck tires, say 15-17 inches , then a lighter car will stop much shorter than your truck. Maybe true, but the car's stopping distance isn't the only consideration. |
#13
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Which Tow Vehicle
There are many crash instances where a light lower vehicle will be
fatal where a higher sitting one wouldn't. But there are also situations where a large top heavy one weighing a lot will be worse. It all just depends on the crash situation. Bill, your experiences are with much older vehicles and not with modern compact tow cars. I'd much rather hit a wall, tree, ditch or whatever in a smaller tow vehicle than in a big SUV. As to engine cooling capacity, I've towed for thousands of miles including in the desert in summer and up grades in NM in summer with a Honda Accord 5 speed and have never had to even shut the AC off. It's relative colling capacity that matters. Smaller engines just don't need huge V-8 radiators to cool just as well. Maybe better as they pull a lot less weight. The crash test comparison between a Mini Cooper and an F-150 pretty well says it all for me. I especially feel safer on tight downhill grades in a smaller vehicle as it is easier to control. Though I wouldn't want an SUV or Semi to fall over on top of me. That would be bad and make me wish for the SUV in that scenario. |
#14
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Which Tow Vehicle
I had a Ford Ranger 4L V6 auto, ext cab, it was marginal for a heavy factory
Grob trailer My new 07 Toyota Tundra 5.7L Double Cab does not even notice the LS-4 in the trailer BT "Mike the Strike" wrote in message oups.com... Bob: As a physicist, I am also a great believer in Newton's laws. I once towed a trailer containing my Jantar-1 (19 meters) with a VW bug, or rather I should say the trailer propelled my bug down the road only marginally under control. I terminated that experiment very quickly! Since that attempt, I have used larger vehicles (station wagons in the old days) or SUVs more recently. I now use the moderately-sized Toyota 4Runner (Prado Land Cruiser to the rest of the world), which has a V8 gasoline engine as an option here in the USA. It's the perfect size, weight and power for towing a single-place sailplane ( I tow a Discus 2). The standard gasoline engine here or the diesel available in much of the rest of the world would be OK at sea level, but in my view you need both sufficient mass and power in the tow vehicle to maintain control and stability. Yes, I know we'll get posts from the guys who'll tell us they towed their Duo Discus over the alps using a Fiat 500. That doesn't meant that it is necessarily a good idea! Mike |
#15
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Which Tow Vehicle
Tom,
You are correct about the higher deceleration forces of a lighter vehicle when it crashes head on with a heavier vehicle, due to the larger inertia of the heavier one. But it does not mean that the occupants of the heavier are safer, as their structure may experience more damage, so it's hard to really tell what would happen and I would say one would have to examine the overall safety and design of each vehicle, like we compare the sink measurements of each glider. An ASW 17 for instance is not necessarily better than an 18 Meter ship, etc....or even perhaps a 15m Diana -2 at certain speeds. http://www.bridger.us/2002/12/16/Cra...operVsFordF150 Size is not all that matters but design. And yes, I meant brakes.........my bad...... |
#16
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Which Tow Vehicle
tommytoyz wrote in
ups.com: You are correct about the higher deceleration forces of a lighter vehicle when it crashes head on with a heavier vehicle, due to the larger inertia of the heavier one. The deceleration forces are an extremely important factor in the survivability of any accident. Consider that the brain has the consistency of blancmange, and imagine how easy it is to disrupt internal connections. Or get an animal's brain from the butchers (if that's possible any more , and just play around with it. But it does not mean that the occupants of the heavier are safer, as their structure may experience more damage, To some extent more damage to the structure leads to less damage to the occupants: energy is required to deform the structure, and that energy then can't be dissipated in the occupants. That's one essential reason why car's "crumple zones" are so important. The worst case would be a light vehicle that didn't crumple or otherwise absorb energy in a smooth fashion. so it's hard to really tell what would happen and I would say one would have to examine the overall safety and design of each vehicle, I certainly agree with that, and I'm sure we both acknowledge that it is a very difficult topic. like we compare the sink measurements of each glider. An ASW 17 for instance is not necessarily better than an 18 Meter ship, etc....or even perhaps a 15m Diana -2 at certain speeds. http://www.bridger.us/2002/12/16/Cra...operVsFordF150 Interesting article. Shows the crumple zone quite nicely. I'd still looks like that, on balance, smaller cars fare worse. But there are notable exceptions - see you next statement. Size is not all that matters but design. When size is constant, design matters. When design is constant, size matters. Which is more important? I wouldn't like to say. But all other things being equal (ha!), I'd rather be in a larger vehicle than a smaller one (so long as it doesn't roll Having said that, I drive a "subcompact" car And yes, I meant brakes.........my bad...... I've never made such a mistake. Never. Oh no. |
#17
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Which Tow Vehicle
tommytoyz wrote:
I've seen a crash test of a smaller Renault against a Land Rover and the Land Rover was in worse shape after the head on collision test - especially the occupants. If that was a series 1,2 or 3 Landrover its not at all surprising because these models had almost no energy absorbing capability: that beam across the rear is the rear chassis member and the front bumper may look strong, but its bolted directly onto the main chassis box members. I owned a series 2a long wheelbase model and was told that, if I had to hit anything, to make sure I hit it square on because anything else would twist the chassis. As a result, Landrovers are not as tough as they look. The same would apply to all vehicles with similar construction, i.e. it probably applies to most of the earlier jeeps too. I don't know how the later Landrover chassis is built, but wouldn't be surprised if this also applied to the series 4 and Defender models. I think Rangies and Freeloaders have enough additional fancy stuff round the front end to absorb at least some energy. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
#18
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Which Tow Vehicle
On Oct 10, 9:47 pm, Martin Gregorie
wrote: tommytoyz wrote: I've seen a crash test of a smaller Renault against a Land Rover and the Land Rover was in worse shape after the head on collision test - especially the occupants. If that was a series 1,2 or 3 Landrover its not at all surprising because these models had almost no energy absorbing capability: that beam across the rear is the rear chassis member and the front bumper may look strong, but its bolted directly onto the main chassis box members. They had a neat simple and foolproof design principle for minimising the damage to the car when travelling over rough terrain. The stiff suspension caused the occupants to bounce around so much that they would voluntarily keep the speed below that at which the car would be damaged. Well, I'm sure there's an element of truth to that anyway, particularly without seatbelts. The Land Rover's crumple zone was built into the other vehicle, of course. I owned a series 2a long wheelbase model and was told that, if I had to hit anything, to make sure I hit it square on because anything else would twist the chassis. As a result, Landrovers are not as tough as they look. Yes, but they would still get you home even with a twisted chassis. And the chassis could be repaired by the local blacksmith. |
#19
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Which Tow Vehicle
On Oct 10, 9:47 pm, Martin Gregorie
wrote: tommytoyz wrote: I've seen a crash test of a smaller Renault against a Land Rover and the Land Rover was in worse shape after the head on collision test - especially the occupants. If that was a series 1,2 or 3 Landrover its not at all surprising because these models had almost no energy absorbing capability: that beam across the rear is the rear chassis member and the front bumper may look strong, but its bolted directly onto the main chassis box members. They used a simple design principle to limit damage to the vehicle when travelling over rough terrain. A stiff suspension ensured the occupants realised they were more fragile than the vehicle, so they instinctively kept the speed down. It is especially effective if the driver is tall and there aren't any seatbelts. Of course the Land Rover's crumple zone was built into the other vehicle. I owned a series 2a long wheelbase model and was told that, if I had to hit anything, to make sure I hit it square on because anything else would twist the chassis. As a result, Landrovers are not as tough as they look. Yes, but they would get you home even with a twisted chassis, and the local blacksmith could bend it back into shape. There was quite a lot of controversy, IIRC, about the decision for the later models to have coil springs instead of leaf springs. It is much easier to repair/replace a leaf spring after it has broken. |
#20
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Which Tow Vehicle
Tom Gardner wrote:
They had a neat simple and foolproof design principle for minimising the damage to the car when travelling over rough terrain. The stiff suspension caused the occupants to bounce around so much that they would voluntarily keep the speed below that at which the car would be damaged. Well, I'm sure there's an element of truth to that anyway, particularly without seatbelts. My Rover xc manual advised always wearing a seat belt when going off road "because it stops your head from hitting the roof so often". In any case, any one thinking of serious off-road in a long wheel-base machine replaced the rear springs with the HD units. The Land Rover's crumple zone was built into the other vehicle, of course. Too true. Yes, but they would still get you home even with a twisted chassis. And the chassis could be repaired by the local blacksmith. I'd never knock the series II or III. Mine did a London-India out and return in 10 months without any problems apart from a tendency to consume speedometers that I never got to the bottom of, a clutch change in Mysore and a clutch slave cylinder replacement in Turkey. It was a simple machine and easy to maintain with relatively few tools: almost everything could be removed and reinstalled with only 3 or 4 different ring spanners and a screwdriver. -- martin@ | Martin Gregorie gregorie. | Essex, UK org | |
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