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Discussion in 'Rivian General Discussions' started by Nordic, Jul 23, 2019.
InsideEV also posted an article with the same video embedded.
From the autoblog article - "Video has surfaced of a Rivian R1T doing a "tank turn" — that is, spinning in place like a tracked vehicle."
There's one problem with that statement and that is the pickup in the video did NOT spin in place. If it did, then yes, it would be a tank turn/steer. However, the video basically shows that after the truck stopped it accelerated forward for a distance and whipped the back-end around. The "tank steer" looks to have kicked in toward the end of the maneuver to assist bringing the front-end around completing the 180.
Also, nearly all the comments from the InsideEV article claimed the maneuver was CGI. If that's true, I don't see the point of the video, especially since it wasn't an official video from Rivian marketing.
However, the most interesting part about the video ... it's now "no longer available due to a copyright claim by Rivian IP Holdings, LLC." Hmm ....
I'm also wondering about the Ford pickup ad that shows its EV prototype towing 1.2 million pounds. Could small truck tires with only the weight of the pickup bearing down actually get enough traction to pull that much weight?
There is a lot of hyperbole and some downright silliness in some of the marketing around EVs.
1) I don't think the tank turn was CGI, and am guessing the forward move first was to create momentum to help the truck break traction when executing the turn.
2) Ford train video is definitely hype, but probably effective marketing for most audiences. I'm betting a modern diesel truck could do the same thing...trains have low rolling resistance.
1) The tank turn video is 100% CGI. No question. The feature, however is 100% real (have seen video direct from Rivian employee's personal cell) but will be off-road only.
2) I fully agree. Remember when the Toyota Tundra (~11k lb towing capacity) towed the space shuttle Endeavour (~300,000 lbs) back in 2012?
Hmmm. The train weighs four times what the shuttle did. To me it's less a question of the torque of the towing vehicle than whether the friction between the tires and the ground surface would be sufficient to overcome the inertia of 1.2 million pounds, despite low rolling resistance once the load is underway. For instance, without antilock systems, hard braking almost any car will break the tires loose from the pavement. Would a typical small truck tire that would lose traction under heavy braking have enough friction to overcome the inertia of a 600-ton train? I don't have the math knowledge to calculate how much load is put on the tires by a rapidly decelerating truck of roughly 6,000 pounds, so it's an honest question, not an argumentative one.
Not mine (from Republic Locomotive):
The Power required to move a train is defined by a simple formula:
Where P is power in horsepower at the rails, T is tractive effort in pounds and S is speed in miles per hour.
The tractive effort required to move a train consists of numerous factors, but for most applications only four need to be considered. First, a force of 2 to 5 pounds per ton of train weight is required to move on straight level track. At very slow yard speeds only 2 to 3 pounds is needed while increasing to about 5 pounds at higher speeds. This force is required to overcome bearing friction, rail deflection, minor flange contact, etc. Years ago, the initial starting requirements were much higher when cars had friction bearings. Today, with all roller bearing journals, this is not much of a consideration.
Looks like it would only need about 3000 lbs of tractive force and only 8hp at 1 mph.
So it would work. Amazing.
The friction of rubber tires from a truck are actually much higher than the friction of the trains wheels on metal. This is why trains need very shallow gradients. They don't have the friction on the drive wheels to climb steeper grades.
If you guys haven't already seen this, here is some analysis on the train pull:
That's very interesting. However, I really enjoyed the first comment under the article:
"574,964 lbs. That's the weight of the train that the world record holder pulled using his teeth - almost half (46%) of that which the F-150 managed. Try again, Ford."
Yet more engineering/nerd stuff about the math behind the train pull: