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Old 08-01-2012, 06:29 PM   #1 (permalink)
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T-100 road test results

I got in late last night from New Mexico.Drove straight through,703 miles.
I delivered the cab-wing spoiler for Gilkison's 4RUNNER/APEX travel trailer and we were able to do a short shake-down run leading up to his 1,200-mile upcoming trip to Denver,Colorado and back.(another thread if we learn anything concrete).
On my trip I ran three segments,with 'normal' posted speed up to 70 mph max cruise speed out to Monahans (390-miles),then I was running 80-mph(3,050 rpm ) from there out to 60 miles out when a tire divorced it's tread,shredding part of the truck before finding it's way to the road bed.I was able to ease her over to the shoulder to enjoy some West Texas' sunshine and heat while I swapped the tire and dealt with the aero naughty bits which had just been killed by the Michelin 'grenade.'
I had to remove the passenger side rear wheel skirt as it had lost some of it's mounting hard points as well as that tire's lead fairing which was only half-attached by then.The bellypan and inner fender wells are toast in that region now and will have to be restored before I leave for Bonneville.(didn't have enough to do as it was).
I made it into Gilkison's running back down at 'normal' velocity.Shook Tire Co. of Las Cruces,NM was able to scrounge up a very-used 15" tire for me as a 'spare.'
After some 'fun' activities and the wing testing,I headed back,running straight in on a single tank from the gas station in Dona Ana,NM.
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*overall round-trip was 1,379-miles
*fuel consumption was 42.698 gallons
*ave trip fuel economy was 32.296 mpg (including 60 miles @ 80 mph)
*compared to the truck's mpg baseline I saw a 38.611% improvement in mpg
*From SAE Paper # 649A this suggests a 64.35% drag reduction
*At 64.35% reduction the T-100 would have only 35.65% of original drag.
*From an original published Cd 0.44,the new wind-averaged Cd is 0.156.
*Test weight was 4,135 lbs.
*There was the monsoonal weather pattern going on with strong winds and many rain squalls going west on day one.
*Day 'two' was dry with much West Texas wind (think wind power capital of the U.S.A.)
*When I filled up back in Denton it was 98-degrrees F,29.87" corrected baro.,29% R.H.,wind south at 9 mph.It had been SW @ 10 mph,with gusts to 23 at Midland,Texas that afternoon.
*Max. speed (during evasive passing maneuver) 84 mph.
*All traffic was stuck in a 9-minute gridlock,zero mpg wait,going through the U.S.Border Patrol inspection station in NM.
*I ran with my window all the way down,the passenger window cracked about 1",and my side of the slider window wide open.
*No AC
*No accessories
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At Cd 0.156 and 64.35% drag reduction,Hucho suggests that the top speed will rise 21.45%,from 96 mph,to 117 mph.
*I was missing the forward three sections of belly pan(no time to install them).
*I was missing the rear wheel trailing fairings.
*I was missing the boat tail tail light lenses
*I had the new body damage and those missing parts for 929 out of 1,379 miles of the trip.
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If I can restore and harden everything by September 4,I may be able to eek out a little better performance.Out a time gotta go!

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Old 08-01-2012, 08:00 PM   #2 (permalink)
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You need to get some better trailer tires. I believe something similar happened last year.
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Old 08-02-2012, 10:36 AM   #3 (permalink)
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A successful run, despite the tire.

Jethro: sounds like it was the truck's right rear that went, not the trailer?
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Old 08-02-2012, 05:46 PM   #4 (permalink)
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tire

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Originally Posted by JethroBodine View Post
You need to get some better trailer tires. I believe something similar happened last year.
Yes,Jethro,Darin picked up on the tire being on the T-100,not the trailer,as that project will languish as so many others for awhile.Just running the tail this time out.
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Old 08-04-2012, 04:45 PM   #5 (permalink)
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interpreting the numbers

I've spent some time with the trip data and here are some observations:
*With a measured wake area of 35% of frontal area and referring to Kosin and Lehmann's work illustrated in Horner's Fig. 3.23 (see Tempate thread) it puts the 'fuselage' of the truck at about 60% of 'Template' aft-body.
*At this length the 'Template' would allow Cd 0.153,which is in close agreement with Cd 0.156 from SAE Paper # 649A(delta-Cd vs delta-mpg)
*With the added length of nose and tail,the fineness ration of the T-100 is L/D= 3.704,up from 3.134 for the stock truck.
*The 1993 "Yellow Ferret" EV-1 land speed record car,with boat tail,had a fineness ratio of 3.732 and estimated drag coefficient of Cd 0.158.
Some other fineness ratios and Cds:
*1991 GM Ultralite -------- 3.259= Cd 0.19
*2009 VW 1-liter---------- 3.346= Cd 0.195
*1993 GM EV-1 LSR ------- 3.732= Cd 0.158
*1937 Schlor car---------- 3.394= Cd 0.186
*1999 GM Precept -------- 3.42 = Cd 0.163
*2005 AeroCivic----------- 3.722= Cd 0.17
*1984 Probe-IV----------- 3.828= Cd 0.154
*1984 Citation IV --------- 3.854= Cd 0.18
*1921 Jaray pumpkinseed---4.006= Cd 0.13
*1957 MG EX 181 --------- 4.526= Cd 0.12
*1933 Lay pumpkinseed ---- 5.044= Cd 0.12
*1987 GM Sunraycer ------- 4.853= Cd 0.12 (as raced)
*1996 HONDA Dream-2 ----- 6.666= Cd 0.10
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Each vehicle must be viewed with respect to it's own individual and unique body features,however Hucho's length-to-low-Cd relationship is firmly represented.
--------------------------------------------------------------------------
From Hucho's relationship of drag reduction to top speed,as the truck now stands,it's top speed should be in the vicinity of 117-mph,up from 96-mph.
I'll add another 18" of tail for Bonneville 'n call it good.With 3-miles of run up we'll see what she can do.
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Old 08-05-2012, 08:19 AM   #6 (permalink)
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CapriRacer can comment most intelligently on that tread separation (as we amateurs call it), and Texas heat, high speeds plus tire age (and wear type, not just miles) are such, that, as of 97F ambient one starts to see t-s [gators] all over the place. Can almost call it the beginning of summer in this state.

Glad that no other damages accrued, and that a full stop was safely made.. Are LT tires on the replacement list?
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Old 08-06-2012, 04:47 PM   #7 (permalink)
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LTs

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Originally Posted by slowmover View Post
CapriRacer can comment most intelligently on that tread separation (as we amateurs call it), and Texas heat, high speeds plus tire age (and wear type, not just miles) are such, that, as of 97F ambient one starts to see t-s [gators] all over the place. Can almost call it the beginning of summer in this state.

Glad that no other damages accrued, and that a full stop was safely made.. Are LT tires on the replacement list?
I've got to keep H-rated rubber on the beast until after September.And I don't have a spare set of wheels which means I'll have to live with these.
It was the VERY OLD Michelin OEM type tire which grenaded.I was shocked when it happened but not surprised.
When a clock or a calendar dictates a departure date rather than actual project completion I'm always at risk.It's the way of the low buck scientist I guess.

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