Acceleration and Coasting - anything thoughts?

77Bandit · #1 (**permalink**) 04-08-2009, 08:46 PM

I'm wondering if anyone can tell me about how long it takes to accelerate a loaded truck to around 70mph from a standstill - say 60k+ lbs, also can anyone share with me how well a loaded truck will coast? Has anyone ever had a breakdown and coasted to a stop and though probably not a happy memory...can recall about how many miles you were able to go? I'm doing a project for school and thought I'd ask the experts!)
Thanks!

PS Guestimates are most welcome - and if I ever get real data I can tell you how close you were!)

carl_3431 · #2 (**permalink**) 04-08-2009, 09:11 PM

There are a few variables in the acceleration of a loaded truck. Mainly the horsepower under the hood. It can range from 350hp or lower to 600+. The terrain is also a factor.

As far as coasting goes, you can coast all day long if you're going downhill. You might be able to coast a loaded truck on flat ground for maybe a mile from 65mph.

Comftblynumb · #3 (**permalink**) 04-08-2009, 09:21 PM

Very much depends on the terrain. With even a slight down hill, you can coast quite a way. Uphill, and the numbers on your poll would change dramatically. A fully loaded truck can weigh 80,000 including load and equipment, (anything over requires special permits). With the equipment I drive, getting to full speed (governed at 62) can take over a mile on flat ground. You might notice on the highway you will pass a truck while going up a hill but then it flies past you going down hill. That is gravity hard at work on us.

Horse power settings also make a difference. Today's trucks are monitored closely by the trucks computers. Mechanics can tweek the settings for about everything.

Coasting on flat ground would be just a little less than a car only because we have more tires on the ground causing friction resistance. I recently had my truck shut down because the coolant level got too low due to a slow leak in radiator cap. (The truck computer again). Was on pretty flat ground and from 60mph, I coasted appx 1/2 a mile where there was enough shoulder to pull off the road. Had some speed left but not much.

Good luck with your report!!!

baiano · #4 (**permalink**) 04-09-2009, 06:01 AM

Also depends on how many trailers being pulled. Generally with me, if I am grossing 60k I have more than one trailer, which creates more drag. Also, if I have 3, 60k spread across 3 trailers makes for pretty light loads which allows the wind to have a little more fun with me, also slowing me down.

If you need someone to confuse you more, I'm right here.

77Bandit · #5 (**permalink**) 04-09-2009, 10:19 AM

Thanks for the replies and good information! I should have said I was thinking on flat terrain so thank you for reading my mind!) I just happened on that show on the speed channel last night where people guess the quarter mile time for cars/trucks/motorcycles - someone should run a real truck there!

Comftblynumb - you said that engine speed is governed at 62mph? Is that because of a certain company, or truck manufacturer, or state speeds? I live in Michigan and I thought here trucks were limited to 55mph, but that isn't the case in other states is it? - are trucks allowed to go 70mph in some states?

Cerberus_Kelpie · #6 (**permalink**) 04-09-2009, 03:11 PM

Speed Limits fluctuate from State to State:
in Texas on I-10 near El Paso the speed Limit is 80 for ALL vehicles.
On I-40 and I-30 it's a bit less.
in New Mexico on I-10 and I-40 the Speed Limit is 75 for ALL vehicles.
I don't know about the speed limit on I-25.
Ohio has/had the Split Speed Limits where Trucks were supposedly relegated to 55 but cars could go 65.
California has the Split Speed Limits like Ohio (did) but cars can go 70.
North Carolina--anywhere from 55-70.

Flat land with a Road Tractor (2001 Freightliner Century Class for example with a 525 HP [at 2300 RPM] Cummins N-14 into an Autoshift and 3.38 Drives) and a 53' Dry Van (with the tandems set just forward of the 40' mark) loaded therefore making the Combo equivalent to 80,000 lbs., it would usually take about 1.5-2 miles to FULLY get to cruising speed with ALL tires properly inflated.
Sometimes less distance, sometimes more.
This is on a DRY road, Sunny skies with a mean temp of 70 and a slight cross wind. A headwind forget it, a tailwind YES.

Coasting on flat ground works BEST in Neutral.