by "Jcarr" (jcarr)
Published 11/17/2017 at 10:27
by "Jcarr" (jcarr)
Published 11/17/2017 at 10:27
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STARS: 0
I have a question for you. As I was driving to work this morning, I passed a big rig and it got me wondering how much effort it would take something like my GMC Envoy to move an empty semi trailer on a flat surface. That got me wondering about the physics of pulling something on wheels as opposed to pulling something without wheels.
How does one determine the effort needed to pull something on wheels vs. something not on wheels?
If an empty semi trailer weighs 15,000lbs, on a flat surface it should feel like pulling less because the wheels mitigate some of the friction, right?
"OpposResidentLexusGuy - USE20, XF20, XU30 and Press Cars" (jakeauern)
11/17/2017 at 10:30, STARS: 1
Wheels make it much easier. I have towed with a Tundra and while it is great, it could not pull this without wheels.
"MasterMario - Keeper of the V8s" (mastermario)
11/17/2017 at 10:34, STARS: 1
It will definitely feel like pulling less, wheels mitigate most of the friction. That’s the whole point of wheels. It wouldn’t take much effort to get an empty trailer moving, your envoy would handle it fine. On a flat surface a person could get an empty trailer moving if they had enough grip.
"crowmolly" (crowmolly)
11/17/2017 at 10:35, STARS: 1
!!! UNKNOWN CONTENT TYPE !!!
This truck is 30 US tons, so your Envoy should handle it OK.
"Bman76 (hates WS6 hoods, is on his phone and has 4 burners now)" (bman76-4)
11/17/2017 at 10:37, STARS: 1
*cough*those bogies were hydraulically powered*cough*
"Jcarr" (jcarr)
11/17/2017 at 10:41, STARS: 0
I get that, I was just curious how you would go about calculating the actual “feels like” weight.
"Sam" (samwellington)
11/17/2017 at 10:41, STARS: 5
F = mu*N is the equation that gives you what you need I think.
mu is the friction coefficient (the resistance based on wheels or no wheels) and N is the normal force (the weight of the trailer). That’ll give you the minimum force required to pull it whether it has wheels (low mu) or no wheels (high mu).
(Full disclosure: this is based on a year of high school physics taken 3 years ago, and I got a C)
"Jcarr" (jcarr)
11/17/2017 at 10:42, STARS: 0
How do you determine the mu?
"OpposResidentLexusGuy - USE20, XF20, XU30 and Press Cars" (jakeauern)
11/17/2017 at 10:45, STARS: 1
Shudduppppp
"Future next gen S2000 owner" (future-next-gen-s2000-owner)
11/17/2017 at 10:48, STARS: 1
If you summed up all the rolling resistance and frictional values you could find it. Just figure out the center of gravity and it becomes a repetitive math problem.
"MasterMario - Keeper of the V8s" (mastermario)
11/17/2017 at 10:50, STARS: 0
Not quite right. The friction coefficient for no wheels would be based on the frame sliding on pavement whereas the friction coefficient for wheels would be based on the axles sliding in their hub (assuming no rolling resistance in the tires)
"PartyPooper2012" (PartyPooper2012)
11/17/2017 at 10:52, STARS: 3
There is a chart that has friction coefficients for things like dragging on ground, ice, wheels etc. look that up - friction coefficient chart
"PartyPooper2012" (PartyPooper2012)
11/17/2017 at 10:56, STARS: 1
Stolen straight from the internets
"MasterMario - Keeper of the V8s" (mastermario)
11/17/2017 at 10:57, STARS: 1
Finding the force required would be based on a simple sliding friction problem for no wheels.
http://www.softschools.com/formulas/physics/static_friction_formula/30/
For wheeled you would need to calculate the friction in the axles/hubs which you can probably find on the internet somewhere. This would be assuming no rolling resistance from the wheels either.
"PartyPooper2012" (PartyPooper2012)
11/17/2017 at 10:58, STARS: 1
To be fair, that guy is putting out at least 300 horse power
"Spanfeller is a twat" (theaspiringengineer)
11/17/2017 at 11:00, STARS: 1
Its called friction and newton’s first law.
You can pull an empty semi trailer if you vehicle can physically support the weight of the tongue of and the force necessary to achieve and sustain motion is applied.
"Demon-Xanth knows how to operate a street." (demon-xanth)
11/17/2017 at 11:00, STARS: 2
There are a number of limiting features:
1: The rolling resistance. Weight deforms tires, that the deformation causes resistance.
2: Wind resistance. Trailers are quite large parachutes.
3: Inertia. This also affects stopping and turning in an obscene way.
Remember, this happened:
https://jalopnik.com/5951454/how-a-5600-pound-toyota-towed-a-292000-pound-space-shuttle
Conversely:
!!! UNKNOWN CONTENT TYPE !!!
"EngineerWithTools" (engineerwithtools)
11/17/2017 at 11:03, STARS: 2
There are basically 3 things that you fight in a rolling vehicle on a flat surface: Rolling resistance, windage and aerodynamic drag.
We’ll focus on rolling resistance:
Rolling resistance for a given setup is proportional to weight and mostly independent of speed (staying away from edge cases). For a vehicle or trailer, it’s the sum of the bearing drag, not including bearing windage, force required to deform the tires a little and some other very small things. Vehicles have a coefficient ~ 0.01 and trucks are marginally less. So using .01, a 15,000 lbs trailer would take 15000*.01=150 lbs to pull slowly under ideal conditions. (Maybe a little more just to get it started.)
Taking the wheels off and just dragging the frame down the road changes the coefficient to the static coefficient of friction between the two surfaces (and then the dynamic coefficient of friction after it’s moving). Steel - to - concrete static looks to be about 0.5. So 15000*.5=7500 lbs. to get it moving, marginally less to keep it moving.
"EngineerWithTools" (engineerwithtools)
11/17/2017 at 11:06, STARS: 0
Ha! Were they really? I see axle tubes, brake cans and drums on the front bogies, but no hydraulics. Were some of the others powered? It was already pretty cheesy in my opinion (you want to prove something to me? let’s find a hill). Powered bogies would take it from cheesy to complete farce!
"Sam" (samwellington)
11/17/2017 at 11:13, STARS: 0
The Space Shuttle may be slightly higher than the Tundra’s recommended hitch weight.