Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
AKA How we stopped worrying and followed Tesla's lead.
AKA Actually how this prototype will somehow become eventually become a real mass-produced vehicle once we actually secure enough batteries at a cheap enough cost, but more likely after we lose market share to Tesla and Rivian pickups.
I wonder what the batteries were depleted to after that short run? They always talk about how much torque an EV makes, but fail to mention how fast the batteries lose charge if you actually use it.
Can someone calculate a simple thing:
F150 weight and tire print are known. Then, how much friction force will there be between asphalt and F150? I am most curious, how that force was enough to prevent tires from slipping, when pulling such weight. I will NEVER believe that friction force was more than weight of all the carriages. Unless they loaded that truck bed with led, what did not look like it.
I simply do not believe that commercial. Physics are stubborn. You got to have friction higher than what you pulling. Or, wheels WILL spin and then you loose that friction and go nowhere.
So it's F=mR, with F being break away friction at which slippage occurs. m being coefficient of friction between asphalt and tire. That is 0.9 in the best road condition. R is weight of the vehicle.
So, say, that truck weighs 10 tons. Just for the heck of having very heavy battery. Normally, its around 2.5-3 tons.
Then break away friction will be 10x0.9=9 tons.
Nine tons. I'll be very generous and say that under some magic super grip tire and asphalt additionally waxed with rosen, for higher friction, that truck can pull 5 times it's weight, without losing traction. I am super generous. 45 tons. Or, 100 000 lb.
How much do all the carriages weigh?
It's not fake. And frankly most any truck with an automatic transmission and low range would be able to do the same.
The track is perfectly flat. Steel wheels rolling on steel rails- very low friction. We're talking about a *rolling* coefficient of friction somewhere between .001 and .005 (feel free to google this... I did).
So 1,000,000 pounds with a rolling coefficient of friction of .005 (worst case). That means you need 5000 pounds of force to move it. Now on dry pavement, good tires can have a coefficient of friction of up to .9... and we can be sure they picked good tires for this commercial. So... 5000/.9=5555.56
So in a worst case scenario of .005 rolling coeffient of friction for the rail cars, you need a truck that weighs 5600 pounds to pull it.
Now... does the drivetrain have enough torque to do it?
2019 F150 uses P265/70R17 tires. Diameter of 30.5". Radius=1.27ft. That axle needs 7,060 lb-ft of torque to move this worst-case train. Sounds like a lot.
I bet my rusty old 2000 GMC Sierra 1500 could do it. This is a very plan-jane ordinary truck. Smallest V8 option, 4wd. Nothing even remotely special about it:
4.8L engine torque: 285 ft-lb
1st gear ratio: 3.06
Transfer case low ratio: 2.52
Typical torque converter torque multiplcation ratio: 2.3 (Wikipedia says 1.8 to 2.5 and I don't care enough to look up the exact spec).
Rear axle gear ratio: 3.42
285 X 3.06 X 2.52 X 2.3 X 3.42= 17,287 ft-lb of torque at the axle. 17,287/7060=2.45
So my sad old GMC has more than twice the torque required to move this train. And that's worst-case. The train was probably quite a bit easier than that to move.
Conclusion: marketing gimmick. But most of us already knew that without math
Last edited by turkey-head; 07-23-2019 at 06:20 PM..
It's not fake. And frankly most any truck with an automatic transmission and low range would be able to do the same.
The track is perfectly flat. Steel wheels rolling on steel rails- very low friction. We're talking about a *rolling* coefficient of friction somewhere between .001 and .005 (feel free to google this... I did).
So 1,000,000 pounds with a rolling coefficient of friction of .005 (worst case). That means you need 5000 pounds of force to move it. Now on dry pavement, good tires can have a coefficient of friction of up to .9... and we can be sure they picked good tires for this commercial. So... 5000/.9=5555.56
So in a worst case scenario of .005 rolling coeffient of friction for the rail cars, you need a truck that weighs 5600 pounds to pull it.
Now... does the engine have the power to do it?
2019 F150 uses P265/70R17 tires. Diameter of 30.5". Radius=1.27ft. That axle needs 7,060 pounds of torque to move this worst-case train. Sounds like a lot.
I bet my rusty old 2000 GMC Sierra 1500 could do it. This is a very plan-jane ordinary truck. Smallest V8 option, 4wd. Nothing even remotely special about it:
4.8L engine torque: 285 ft-lb
1st gear ratio: 3.06
Transfer case low ratio: 2.52
Typical torque converter torque multiplcation ratio: 2.3 (Wikipedia says 1.8 to 2.5 and I don't care enough to look up the exact spec).
Rear axle gear ratio: 3.42
285x3.06x2.52x2.3x3.42= 17,287 ft-lb of torque at the axle. 17,287/7060=2.45
So my sad old GMC has more than twice the torque required to move this train. And that's worst-case. The train was probably quite a bit easier than that to move.
Conclusion: marketing gimmick. But most of us already knew that without math
If you know and have seen how trains get moving. The couplings are loose for a reason. You pull one, it snatches the next one and so on. I worked at a car plant and have loaded rail cars, all 3 levels. When the train gets moving, you can hear the noise going from the first car all the way down the train to the last car as the slack is tightened up in the coupling making it easier to move. If all the couplings on these train cars were tight, the truck would of had to pull the full weight of the total of the train. Not possible. This was a gimmick.
If you know and have seen how trains get moving. The couplings are loose for a reason. You pull one, it snatches the next one and so on. I worked at a car plant and have loaded rail cars, all 3 levels. When the train gets moving, you can hear the noise going from the first car all the way down the train to the last car as the slack is tightened up in the coupling making it easier to move. If all the couplings on these train cars were tight, the truck would of had to pull the full weight of the total of the train. Not possible. This was a gimmick.
I think you and RCHydro are both right. He's right that loose couplings help overcome the initial inertia of each car. Your math is right once all the couplings are tight and the whole train is starting to roll as a unit.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
