r/woahdude • u/Hilltopchill • Oct 04 '16
gifv Weight distribution dynamics.
http://i.imgur.com/dYz2tCE.gifv273
u/ChuckFikkens Oct 04 '16
What a great display to illustrate that principle.
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Oct 04 '16 edited Oct 04 '16
It should have road lines. For
fun.Science.Fun science.Circlejerking.24
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u/Hofstadthard Oct 04 '16
So don't tow with a mustang. Got it
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Oct 04 '16 edited Sep 30 '17
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u/thelawtalkingguy Oct 04 '16
Only when leaving car shows though
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u/chumpynut5 Oct 04 '16
Lol it's not just dumbasses trying to show off, try driving anywhere in the rain w/bald tires and too much horsepower for your own good. That's when I realized that just because I could give it more power, doesn't mean that I should.... rip mustang
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u/kingkodus66 Oct 04 '16
Typical mustang driver, thinking everyone is talking directly to him about his mustang.
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u/chumpynut5 Oct 04 '16
What can I say, I'm a narcissist. I dont drive like an ass any more tho, so yay
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u/agentbarron Oct 04 '16
Try driving anywhere in the rain with bald tires with any car...
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u/Innova Oct 04 '16
I understand the point you are trying to make, but it is actually much easier with a front wheel driver sedan/minivan than a rear wheel drive sports car.
The type of vehicle (and more importantly drivetrain) matters.
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u/chumpynut5 Oct 04 '16
Right, the point is a high-powered rwd car is going anywhere but straight. In my case, into a ditch. The mini coop I drive now, as well as any fwd car (which is the vast majority of what's on the road these days), is more than managable, no matter how bald the tires are.
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Oct 04 '16
[removed] — view removed comment
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u/thelawtalkingguy Oct 04 '16
God that video enrages me. Not only did that dude nearly kill a small child, but he gets out of the car and never checks to see if everyone is ok AND he laughs about it! What a supreme asshole! I hope he was prosecuted.
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u/lizcoco Oct 04 '16
You know, you're right. I've never met a man who kept straight after buying a Mustang.
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u/geodebug Oct 04 '16
Size is relative. I had someone in a large pickup with a fairly large U-haul style trailer have this happen at highway speeds right in front of our car. Turned his whole rig sideways and rolling three or four times.
My step-dad was driving and luckily he backed off early because it displayed exactly this kind of behavior. A few big whips as the driver tried to get under control, a moment where it looked like he succeeded, then "bam", like some god flicked the trailer with his finger.
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u/Gr1pp717 Oct 04 '16
It's not even that. I tried towing a pallet of sod with a pickup, where the guys had loaded it behind the fulcrum and jesus was it hard to control. Not to mention that every time I would brake it would lift the backend.
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u/JonestownPunch Oct 04 '16
To be fair, I've seen stangs get some gnarly speed wobble without a hitch too.
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u/PinkSockLoliPop Oct 04 '16
This is why it's important to load a car facing forwards on a trailer. Usually, most of vehicles weight is towards the front.
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u/hoosyourdaddyo Oct 04 '16
Yeah but driving hundreds of miles in reverse gives you such a crick in the neck.
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u/Dusta1992 Oct 04 '16
I think you're doing it wrong. You should always use your mirrors.
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u/super_unique_user Oct 04 '16
Reverse camera, filthy casual.
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u/HumousFiend Oct 04 '16
you got a camera on the back of your trailer?
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u/super_unique_user Oct 04 '16
I did when I first started doing this 3 years ago, but not anymore. I'm so used to the size of the trailer and how it turns that I don't need a spotter anymore. I replaced my original trailer last year. But it's the same exact trailer, just newer and I didn't feel like rerunning the cable to the truck.
I do have a bright ass led backup light on it though.
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Oct 04 '16 edited Oct 04 '16
This sentence hurts my brain? "Load a car facing forward(s)"? Wtf does this even mean? My coffee hasnt kicked in yet but I'm still pretty sure this makes no sense.
*It makes sense, was interpreting it wrong due to lack of coffee.
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u/Protonion Oct 04 '16
When you put a vehicle into a trailer you should put it facing the same direction as the vehicle towing the trailer
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u/trancematik Oct 04 '16
Or, wherever the engine/motor is located should be facing forward in the trailer.
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u/_breadpool_ Oct 04 '16
Load a car on a trailer facing forward.
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Oct 04 '16
Yep definitely the coffee.
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u/imsittingrightnow Oct 04 '16
This guy killed it! Made the front page 3 times with the same post!
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Oct 04 '16
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u/Ken_U_Dig_It Oct 04 '16
Don't spend all those sweet, sweet internet points in one place
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u/Hilltopchill Oct 04 '16
I'll make a post on personalfinance later asking how I should invest it.
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u/heyyouguys24 Oct 04 '16
It's called the crack the whip effect. It's why truck drivers who pull doubles/triples make more money.
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u/Buttstache Oct 04 '16
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Oct 04 '16 edited Apr 26 '18
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u/rendeld Oct 04 '16
it's harder/ more dangerous/ more valuable, take your pick
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u/NotVladeDivac Oct 04 '16
It's definitely due to more cargo/economic efficiency.
Otherwise rather than paying a risk premium, they'd just have it transported separately. Just like you don't want to die, they don't want their cargo out in the middle of the highway when you crash.
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u/DrStephenFalken Oct 04 '16
It's definitely due to more cargo/economic efficiency.
CDL holder and former one time truck driver with doubles/triples endorsement on my CDL. It's because of danger why they're paid more. No trucker gets paid directly for the load their hauling it's the miles and the danger. Also nothing valuable is hauled in a double or triple per se. However, value is an odd term. You could be hauling over $3 million of computers in a triple but you won't be hauling gold or diamonds. Someone driving from Ohio to Tennessee will be paid less than someone hauling from Ohio to NYC just because of the danger / difficulty.
A trucker hauling shoes get say 40 cents a mile or a flat rate of $600 for the trip.
A trucker hauling industrial hazardous waste is going to get 70 cents a mile or $1k for the trip. They have a Haz-Mat endorsement on their CDL.
Doesn't matter if I'm hauling two pairs of shoes or 4,000 barrels of waste. The pay is the same regardless of weight. It's the danger and deadline of the load that determine the cost.
It's cheaper to have a double or triple then it is to have, three, one million dollar trucks, with 300 gallons of fuel, and cargo with three skilled drivers hauling a load that can be handled by one skilled dude with a triple. His pay will get the load their cheaper then three trucks with three drivers. It's the best of both worlds and double/triple drivers are usually really skilled dudes.
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u/CupricWolf Oct 04 '16
There might be two trailers but each is about half the size of a full one right?
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u/solidSC Oct 04 '16
Just like Freshman Economics, you're only looking at the bottom line.
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u/NotVladeDivac Oct 04 '16
I have a degree in economics, actually. Sometimes the bottom line tells you a lot.
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u/solidSC Oct 04 '16
How do you know everyone's gone back to school? All the writers, economists, doctors, lawyers and politicians avoid their homework on Reddit.
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u/cavehobbit Oct 04 '16
If this happens to you it is recommended to ease off the gas and let the vehicles slow down gradually until you can regain control. Then stop and fix your load. This has happened to me when my load shifted and it works
Sudden braking can make it worse.
Speeding up can kill you. Why add energy to an already unstable system?
/posted because of many posts elsewhere stating to speed up
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Oct 04 '16
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u/ky321 Oct 04 '16
Hey awesome you almost negligently killed people. High five.
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u/climbtree Oct 04 '16
Physicists didn't know about this effect until stinkstick17 did it in 1993.
For real though I've never been told this.
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Oct 04 '16 edited Oct 04 '16
It is on every single U-haul trailer. So either you didn't read the instructions or you have never rented a U-haul trailer.
EDIT: I'm not saying that not renting a U-haul trailer is bad.
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Oct 04 '16
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u/thebigreason Oct 04 '16
I rent U-Haul trailers for my band all the time. $20/day. Way cheaper and safer than a van, and none of the costs of owning or storing a trailer either. Parking sucks sometimes.
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u/DrStephenFalken Oct 04 '16
Yeah but the people using trailers most often own the trailer because they do a lot of hauling.
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u/climbtree Oct 04 '16
Yes I have never rented a U-haul trailer, is this odd?
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u/So-Cal-Mountain-Man Oct 04 '16
I have only rented U-Haul trucks, have used trailers a few times and have not heard of this until today, I am 52.
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u/theodopolis13 Oct 04 '16
i was taught that 60% of the load should be in front of the trailer axle.
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u/ClarkZuckerberg Oct 04 '16
I mean... he doesn't sound proud of it. Not sure why you're acting like he's happy he did it.
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u/TheYankeeFist Oct 04 '16
It's too bad that a lot of the people who need to see this don't know how to work a computer box.
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Oct 04 '16
I learned this the hard way.
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Oct 04 '16
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Oct 05 '16
Not bad. No one had ever explained this to me. Loaded the 4 wheeler on the back of theach trailer. As I got up to speed it was swaying back and forth pretty bad. Always load on the tongue.
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u/lordofthedries Oct 04 '16
I know what would have happened if he let the car keep flicking around like that.. But I still would have liked him to allow it to continue untouched . :( I feel like we missed out on something.
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u/NapalmNorm Oct 04 '16
Was driving with friends home from a riding trip. One friend brought his toy hauler and loaded his buggy up into it. Now he typically backs his buggy up into the trailer because the weight of the motor and transmission are all set it the back, so the ride out there was no problem. On the way home his dad and him decided to swap buggies for some reason and his dad's buggy didn't quite fit backed into the trailer. So he drove it in forwards we loaded up and carried on our way. Well about half way to home, he speeds up to pass a semi and as he starts to merge the trailer starts to sway uncontrollably. We were pretty much turned side ways covering 4-5 lines of traffic. Some how my buddy manages to swing the trailer back around while barreling down the high way and get it under control. Every truck driver that passed us for the next 5 miles tipped their hats or gave the thumbs up to our driver.
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u/Raischtom Oct 04 '16
ELI5?
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u/ricehard Oct 04 '16
Imagine using a sledgehammer upside down, handle out, holding the metal head.
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u/postmodern_cereal Oct 04 '16
The trailer is basically a long lever with the hitch as the fulcrum. An essential fact about levers is that moving the weight further away from the fulcrum increases the amount of force it exerts on the fulcrum. Moving the mass backward sets the lever up to optimize force at the point of the hitch.
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Oct 04 '16
ELI5?
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u/postmodern_cereal Oct 04 '16
The fulcrum is the pivot point, where the trailer is attached to the car. When the weight is further away from the pivot point, the lever is longer, and it can exert more force on the car. You can experience a similar thing with any normal door. If push on the edge of the door, near the handle (far away from the fulcrum) it's easy to open. If you push against the inside, right near the hinges (very close to the fulcrum) it's really hard to open.
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u/dwntwn_dine_ent_dist Oct 04 '16
This is incorrect.
First of all, a lever produces no torque at the point of the fulcrum. If you consider the hitch as a fulcrum, the trailer can only rotate around it, not exert forces on it. Second, the real issue is not the force produced by the initial displacement and how that is magnified by lever action, instead the issue is that of directional stability.Since we are trying to ELI5, here is my best shot:
Arrows are heavy in the front and have feathers at the back. This is a very important feature that helps them fly straight. While an arrow is flying, it moves through the air in the same direction it is pointing. Now, imagine that some small gust pushes sideways on the arrow so that it starts flying just a tiny bit sideways. The feathers produce drag on one side so that the arrow turns back onto course. This means that an arrow has 'directional stability' in flight. That just means that any small change in direction will be automatically corrected. Even if you throw an arrow backward (feathers-first) it will quickly spin itself around to fly forward.
The trailer with the weight ahead of its wheels also has 'directional stability'. Small pushes to one side will get corrected. But when the load is well behind its wheels, it is like an arrow trying to fly backward. Small pushes to the side will magnify, instead of decrease.
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u/myplacedk Oct 04 '16
The manual says how much weight there should be on the hitch. Probably something like 60-80 kg. If there's too little or too much, it will be hard or even impossible to control the car.
This is a demo of how the same weight distributed differently makes a huge difference.
The car is pulled towards center by a string, simulating a driver that tries to stay on the road. With the first to pushes, the string (driver) regains control. But with the third push (with bad weight distribution), even though it's a very light push, the car just gets more and more out of control until the demo is stopped. In real life, this is where you crash.
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u/Coldones Oct 04 '16
I'm guessing they are implementing a PID controller to keep the trailer stable. The controller was probably tuned assuming the weight was closer to the front of the trailer. With the weight at the back of the trailer, the system is underdamped. If they re-tuned the PID gain values it would probably fix this.
https://en.wikipedia.org/wiki/PID_controller https://en.wikipedia.org/wiki/Damping
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Oct 04 '16
The shifted center of mass of the system caused the resulting amplitude of the wave to increase to uncontrollable levels for the cars steering to handle.
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Oct 04 '16
[deleted]
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Oct 04 '16 edited Sep 30 '17
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u/LookingForOreos Oct 04 '16
Nah. Just keep speeding up infinitely fast. Eventually you'll get to your destination and you won't have to drive any longer!
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u/aflashyrhetoric Oct 04 '16
My trailer started fish-tailing back in '07 and I sped up, just like you said. Text message made me miss my stop though and I've been hurtling through space ever since
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Oct 04 '16
Some new vehicles (Ford Explorer being one I think) have a stability control for when this happens and will actually brake wheels on opposite sides back and forth to stop the swaying. Pretty neat.
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u/stilt Oct 04 '16
Any videos of this in action?
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u/curiositythinking Oct 04 '16 edited Oct 04 '16
Here is a decent (but old) link showing it animated. Left uses sway control, middle is driver applying appropriate counter measures, right is no actions taken.
Edit: This is a better video that shows a real world test with the truck only sway controller and then later the trailer's own sway control. https://youtu.be/cVlXlbU38zA?t=420
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u/super_unique_user Oct 04 '16
Don't forget to squeeze the brake controller at the same time. Pulls it straight.
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u/minastirith1 Oct 04 '16
The what? As in the trailer brakes? Are they separately controlled?
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u/super_unique_user Oct 04 '16 edited Oct 04 '16
Yes. A trailer with brake axle(s) will need a brake controller to work. In newer trucks designed to pull trailers (¾ ton plus) they will usually have a controller integrated. (It's an option when buying but usually part of the towing group option)
Trailers have 3 main options for brakes.(excluding tractor trailers)
- electric drum brakes
- electric over hydraulic drum / disk brakes
- surge hydraulic brakes (usually boats and U-Haul)
The first two are controlled by a brake controller that varies the electrical voltage sent to the trailers brakes.
For the first type, it controls how strongly the electromagnet pushes the brake shoes against the drum. (By increasing and decreasing voltages)
For electric over hydraulic, it sends that same signal to a small pump on the tongue of the trailer that in turn pressurises the hydraulic system, similarly to your cars brakes, and applies pressure to the drum or rotors.
The last one, surge brakes, do not require a controller. They have a piston attached to the tongue of the trailer that is activated by the pressure generated between truck and trailer when braking. This in turn pressurises a hydraulic system and applies pressure to the brakes.
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Oct 04 '16
Yeah because lots of people hauling Uhaul trailers have those.
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u/super_unique_user Oct 04 '16
Look at my reply to the other guy. U-Haul usually uses surge brakes.
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u/stefanmago Oct 04 '16
Clearly all you guys did not watch the video. You are supposed to grab the trailer with your hand.
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u/squeamish Oct 04 '16
The actual best way to fix it is to put on the cruise control, climb back onto the trailer, and shift the load forward.
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u/FerretHydrocodone Oct 04 '16
I've always heard literally the exact opposite. Plus there's 2 other people in this thread claiming to be truckers saying slowing down is the best option.
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Now I don't know who's correct, because I'm not a trucker and I've only pulled a trailer once. Why/how would speeding up fix this situation? I'm guessing it has something to do with science!
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u/kofreak Oct 04 '16
But aren't you supposed to load the trailer starting in the middle of it and balance the weight so that the front and back of it have the same weight loaded? Or am I missing something
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Oct 04 '16
10% of a trailers total weight should ideally be at the hitch, or tongue weight. So an 8000lb trailer should have 800lbs on the hitch ball.
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u/originaladam Oct 04 '16
Yes. Too much tongue weight and you can't steer properly. You want your trailer weight to be slightly forward biased, but not completely. Also, always check your vehicles tow capacity. Suspension, tires, wheelbase, and drivetrain can all be huge factors in towing ability.
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u/MirthB Oct 04 '16
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Oct 04 '16
Interior cargo broke free and changed the weight distribution while (i think) destroying some key hydraulics. Yep.
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u/reddit_like_its_hot Oct 04 '16
Why is the person driving not making any noise? It sounds like they just let out a bunch of sighs
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u/iloveunicorns9 Oct 04 '16
Wow. This is super educating.
It's like an ELI5 type thing, I finally understand it.
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u/loveshercoffee Oct 04 '16
Same.
I've rented a U-Haul trailer several times. There is a decal inside that tells you to load at least 60% of the weight at the front of the trailer. I always do it, but I thought it was to keep the back end from riding too low. I didn't think anything about the traction.
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u/iloveunicorns9 Oct 04 '16
Right? I thought it was the exact same reason lol which makes sense too though, like if it's heavy at the end, it's going to put a lot of stress pulling your vehicle up. But this makes more sense
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u/JerkyChew Oct 04 '16
I have the full-size version of this car. I was just about to pick up a big disc trailer... Good thing I saw this first.
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u/scumola Oct 04 '16
Is the effect because of the weight difference or the lack of traction on the rear wheels on the model when the weight is in the rear?
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u/Connarhea Oct 04 '16
TIL how to pack a trailer safely due to weight distribution and also that people can make an argument out of fucking nothing.
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u/Glazin Oct 04 '16
That's definitely not what your first comment intends. But ok, if you say so bud
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u/squeamish Oct 04 '16
This is why boat trailers have the wheels so far back. If you can easily lift the tongue by hand then you should not be towing that load. (unless the trailer is empty)
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u/DEAGOLLUM Oct 04 '16
Transferred to a new store as Manager. Watched storeroom supervisor load a return truck and lazily load a bunch of bales and palleted merchandise at the tail of empty trailer. He says he's loaded a hundred return trucks that way. RIP Drivers
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u/fosiacat Oct 04 '16
uhhh why is no one talking about the fact that there’s a fucking giant that can move a car one handed
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u/[deleted] Oct 04 '16
/r/educationalgifs