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Speed Limit to be cut to 50mph

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Re: Speed Limit to be cut to 50mph

Unread postby Twilight » Thu 31 Jul 2008, 14:58:40

Yes, the London Underground is the worst. No air conditioning down there. Every summer there is a spate of medical emergencies when people collapse from the heat (usually compounding an existing condition). The evacuations are so well practiced, often the delay is only one or two minutes. I have seen it take a quarter of an hour on the main lines.
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Re: Speed Limit to be cut to 50mph

Unread postby Arsenal » Thu 31 Jul 2008, 15:01:12

Houses were built a whole lot different back in the day as well. We have a house that was built in the late 1880's where there is a 20 degree difference from outside to inside. Nowadays you can run the AC and still not get that difference in temp in recently built house.

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Re: Speed Limit to be cut to 50mph

Unread postby Byron100 » Thu 31 Jul 2008, 15:09:22

$this->bbcode_second_pass_quote('Arsenal', 'H')ouses were built a whole lot different back in the day as well. We have a house that was built in the late 1880's where there is a 20 degree difference from outside to inside. Nowadays you can run the AC and still not get that difference in temp in recently built house.

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Tell me about it...my grandparent's old farmhouse was the same way. It'd be amazing how much cooler that house kept even on the hottest days. And just by running the ventilation fan to bring to bring up the cool air from the cellar into the rest of the house, it was almost like having central AC. At night, we'd run box fans in the bedroom windows to bring in the cool nighttime air. Of course, it got down into the 60's and even the 50's during the summer back in those days...it'd be not so pleasant now, I don't believe... :cry:
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Re: Speed Limit to be cut to 50mph

Unread postby Dezakin » Thu 31 Jul 2008, 15:35:29

$this->bbcode_second_pass_quote('kokoda', 'S')lowly at first, but eventually a whole range of restrictions will have to be bought in as it becomes more obvious that oil production has peaked.

I believe thrie is already discussion about America returning to the 55 MPH limit it had during the 70s oil embargo.

Not gonna happen unless congress does what it did with liquor laws and hamstrings states with funding. Really this is a state decision.

$this->bbcode_second_pass_quote('', 'I')t wouldn't surprise me if we had rationing by next year.

Not bloody likely. Markets ration by price allready and tend to do it more efficiently.
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Re: Speed Limit to be cut to 50mph

Unread postby joeltrout » Thu 31 Jul 2008, 15:48:09

I think states such as California & Florida should have 55 mph limits with hefty fines ($1,000 per mph over 55). That way they could fund their state budgets with traffic fines since real estate revenue has disappeared.

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Re: Speed Limit to be cut to 50mph

Unread postby yesplease » Thu 31 Jul 2008, 23:39:52

$this->bbcode_second_pass_quote('Valdemar', 'T')oo bad this will increase congestion and save next to nothing. And the optimal speeds for modern cars is around 70 MPH.
For fuel efficiency it tends to be ~45-65mph depending car, for traffic density it's somewhere around ~35mph since braking distance goes up according to the square of speed. In other words, if I need three car lengths to brake safely at 35mph, at 70mph I need nine, so traffic density has to decrease w/ speed.
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Re: Speed Limit to be cut to 50mph

Unread postby aflatoxin » Fri 01 Aug 2008, 00:06:25

100 mile steady speed averages on the freeway:

1995 Volvo 850 turbo station wagon

55 mph 38 mpg
65 mph 32 mpg
75 mph 28 mpg
85 mph 22 mpg

1986 Mercedes 300e 5 speed manual as above

55 mph 32 mpg (4th gear, wont run in 5th)
65 mph 32 mpg
75 mph 26 mpg
85 mph 20 mpg
100 mph 16 mpg
100+ mph 12mpg (leadfooting it between El Paso and Albuquerque)

2006 Mercedes e350CDI (diesel)

55 mph, drafting a semi 50 mpg
55 mph, not drafting a semi 41 mpg
65 mph 38
75 mph 33

drive slower, save gas.
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Re: Speed Limit to be cut to 50mph

Unread postby Hoops_Mckann » Fri 01 Aug 2008, 00:15:57

$this->bbcode_second_pass_quote('Arsenal', 'I') did my own experiment as well.

2000 Ford Explorer
I have done an experiment on my fuel usage. 220 mile trip with the cruise control set.

85 MPH 3hr 15min trip time. 17.4 MPG 12.64 gallons used
75 MPH 3hr 37min trip time. 19.8 MPG 11.11 gallons used
65 MPH 4hr 02min trip time. 24.6 MPG 8.94 gallons used


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You get over 24 mpg in THAT??? at that speed???
Damn, that is about what my lexus is300 sedan (automatic) gets on the highway at that speed???:(
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Re: Speed Limit to be cut to 50mph

Unread postby aflatoxin » Fri 01 Aug 2008, 01:10:25

$this->bbcode_second_pass_quote('Hoops_Mckann', '')$this->bbcode_second_pass_quote('Arsenal', 'I') did my own experiment as well.

2000 Ford Explorer
I have done an experiment on my fuel usage. 220 mile trip with the cruise control set.

85 MPH 3hr 15min trip time. 17.4 MPG 12.64 gallons used
75 MPH 3hr 37min trip time. 19.8 MPG 11.11 gallons used
65 MPH 4hr 02min trip time. 24.6 MPG 8.94 gallons used


Arsenal


You get over 24 mpg in THAT??? at that speed???
Damn, that is about what my lexus is300 sedan (automatic) gets on the highway at that speed???:(


What surprises me is this:

I regularly rent SUV's for work. On long, weeklong 1000 mile + trips with different drivers on a combination of highway driving and oilfield dirt roads, the gas mileage for a Chevy Trailblazer, Tahoe, and Suburban are almost identical. The suburban is 4x the size of the trailblazer.
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Re: Speed Limit to be cut to 50mph

Unread postby the48thronin » Fri 01 Aug 2008, 01:16:51

lol (I cant resist..)

75 MPH......5.3 MPG
65 MPH...... 6.4 MPG
58 MH..... 7.8 MPG

1996 Detroit 430hp 18 speed trans Cant stay in 18th below 58 due to engine lugging below 1300 rpms.

55 MPH in 17th gear... 7.1 MPG

please don't draft behnd 18 wheelers, you cannot draft on mine due to the air tabs eliminating the vacume behind my trailer but I remember how worried I used to be about people drafting behind me before I installed the air tabs.

For those of you concerned about fuel savings more than apearance on an SUV Airtab will work on busses ambulances and suvs...


from my onboard computer data at this time.

Current trip ( from jan 1 reset)..7.2 MPG for 47,040 miles average speed 53.4 MPH
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Re: Speed Limit to be cut to 50mph

Unread postby yesplease » Fri 01 Aug 2008, 01:49:22

$this->bbcode_second_pass_quote('the48thronin', 'p')lease don't draft behnd 18 wheelers, you cannot draft on mine due to the air tabs eliminating the vacume behind my trailer but I remember how worried I used to be about people drafting behind me before I installed the air tabs.
Air tabs shouldn't eliminate the pressure drag, just reduce it, not that anyone tailgating a semi doesn't deserve to get darwinized if they hit it. Speaking of which, did you notice any changes in mileage/boost pressure after installing 'em?
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Re: Speed Limit to be cut to 50mph

Unread postby the48thronin » Fri 01 Aug 2008, 20:55:59

$this->bbcode_second_pass_quote('yesplease', '')$this->bbcode_second_pass_quote('the48thronin', 'p')lease don't draft behnd 18 wheelers, you cannot draft on mine due to the air tabs eliminating the vacume behind my trailer but I remember how worried I used to be about people drafting behind me before I installed the air tabs.
Air tabs shouldn't eliminate the pressure drag, just reduce it, not that anyone tailgating a semi doesn't deserve to get darwinized if they hit it. Speaking of which, did you notice any changes in mileage/boost pressure after installing 'em?


I am the trucker "yoda" on the airtab web site ( sigh yes on XM radio as well). They reduce the drag but cannot eliminate it all together..

The vacume cone behind the trailer is reduced at speed to about 5 or 6 ft instead of the normal 35 ft... if you try to draft behind my trailer at 58 MPH you will have to get close enough to get the majority of your hood inside that cone...

MPH change tabs on tractor only.... +.2 and wind stops blowing tractor around in cross winds


a month later I got the tabs for the trailer... MPG up +.3 more

other noticable effects spray from tires both tractor and trailer never rises above the flo0r of the trailer ( winshield hight for nearby cars tho) untill cross winds go above 25 MPH

running on cruise control at places I commonly go, boost pressure was always about 5 pounds lower
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Re: Speed Limit to be cut to 50mph

Unread postby yesplease » Sun 03 Aug 2008, 05:55:34

$this->bbcode_second_pass_quote('the48thronin', 'I') am the trucker "yoda" on the airtab web site ( sigh yes on XM radio as well). They reduce the drag but cannot eliminate it all together..

The vacume cone behind the trailer is reduced at speed to about 5 or 6 ft instead of the normal 35 ft... if you try to draft behind my trailer at 58 MPH you will have to get close enough to get the majority of your hood inside that cone...
It isn't so much reduced as evened out. Granted, you have seen significant gains, but if anything I'd guess that for the most part the VG's didn't change the overall draft seen by a vehicle behind you, just the distribution/location of it. I have some papers that were run at a NASA(?) facility from the creator, but I don't think I'm allowed to post them publicly so for now I'll just present you with this paper by some Mitsubishi engineers regarding VG's on one of their cars. If you examine Fig.9 on Pg.4 you'll notice that the largest change comes from the distribution of pressure at the rear of the vehicle, not from an overall decrease, although there is one. This results in fewer abrupt transients, a more even change in the pressure behind the vehicle. This is why winds don't buffet the trailer as much, the air flowing perpendicular to the object doesn't encounter as large of a pressure drop in as small of an area, even though marring a slight increase the pressure drop overall is more or less the same, so if a big gust comes up from the side instead of adding a whole bunch of air to the relatively small area behind the cab/trailer, it'll add the same amount to a much large area and the truck won't jolt as much from the pressure differences. In terms of a car drafting you, while they will probably see much more pressure ~10' off your bumper compared to w/o the tabs, otoh as they go farther back they may see lower pressure than w/o the tabs due to the VG's lengthening the lower pressure areas farther back.
$this->bbcode_second_pass_quote('the48thronin', 'M')PH change tabs on tractor only.... +.2 and wind stops blowing tractor around in cross winds


a month later I got the tabs for the trailer... MPG up +.3 more
That ain't too shabby, but imagine what a streamlined combo could see. How much would a fleet average of 10-18mpg help the industry, not counting gravel hauling and the like?
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Re: Speed Limit to be cut to 50mph

Unread postby the48thronin » Sun 03 Aug 2008, 21:40:15

$this->bbcode_second_pass_quote('yesplease', ' ')<snip>That ain't too shabby, but imagine what a streamlined combo could see. How much would a fleet average of 10-18mpg help the industry, not counting gravel hauling and the like?


I have several friends who do have more aerodynamic trucks tan mine... my wife has a mack vision also with tabs.

As t your question, although newer trucks have had DECLINING fuel mileage due to changes to meet newer emission standards, several of my friends are getting 9s to 11s. Their profits are of course more than mine in the same loads..

If trucks were to get 15 to 18 mpg fuel usage in the USA would go down to 1/3 what it is now.... demand destruction and the results are well known...
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