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saltfever
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« Reply #60 on: October 03, 2010, 06:01:29 PM » |
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I'm anxious to see the changes Blue mentioned in his post #57. Good description but you know . . ." a picture is worth . . . "  |
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robfrey
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« Reply #61 on: October 07, 2010, 10:04:17 AM » |
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6363 A/BG ALT
carbinitelsr.com
carbiniteracing.com
carbinite.com
projectvinny.com
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bvillercr
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« Reply #62 on: October 07, 2010, 11:17:51 AM » |
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How fast do you guys plan on running again? The Goodyear 2222 from what I understand is rated at 300mph, although we have had them higher. Also not sure how it would be for a front tire? Good luck with your build.  |
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robfrey
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« Reply #63 on: October 07, 2010, 11:43:55 AM » |
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Sorry, wrong part number. I need the 450mph goodyears like the ones on the Speed Demon.
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6363 A/BG ALT
carbinitelsr.com
carbiniteracing.com
carbinite.com
projectvinny.com
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Jonny Hotnuts
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« Reply #64 on: October 19, 2010, 02:56:59 PM » |
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Not talking smack but I am concerned about the COG/COP relationship with this configuration.
Ever consider vertical fins off the rear wheel covers (*similar in setup to a F15)?
-BTW:
Great job RF....
~JH
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jonny_hotnuts@hotmail.com "Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully." *Andres Segovia (when Im not working on the car, I am ususally playing classical guitar)
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Jonny Hotnuts
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« Reply #65 on: October 19, 2010, 03:08:41 PM » |
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-also, it may of been mentioned but what engine configuration is planned for the vehicle?
~JH
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jonny_hotnuts@hotmail.com "Sometimes it is impossible to deal with her, but most of the time she is very sweet, and if you caress her properly she will sing beautifully." *Andres Segovia (when Im not working on the car, I am ususally playing classical guitar)
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joea
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« Reply #66 on: October 19, 2010, 03:30:05 PM » |
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..so johnny, where did you measure/calculate the cog.....?....and the cop....?....
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Rex Schimmer
Hero Member
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Age: 70
Location: Fulton, CA
Posts: 1475
Only time and money prevent completion!
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« Reply #67 on: October 19, 2010, 04:39:00 PM » |
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I think it is pretty easy to just look at Rob's drawings and you can tell that the CofG (center of gravity) is well in front of the CofP (center of pressure). The engine is going to probably be close behind the drivers cockpit and probably most of the liquids, water, oil, fuel will be ahead of the driver and with the big wheel "spats" the CofP is most certainly to the rear of the car.
Rex
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Rex
Not much matters and the rest doesn't matter at all.
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joea
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« Reply #68 on: October 19, 2010, 10:38:44 PM » |
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yes Rex, but i was curious what johnny was pondering...after reading his query...
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saltfever
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« Reply #69 on: October 20, 2010, 02:01:50 AM » |
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Actually, Jonny may have a point. Excuse my inept use of Word Draw but just threw this together. It would be great to have a nice CAD system (and the skill to use it) like Rob. Assume the CG is located as indicated. Now compare the amount of surface area in front of the CG compared to the surface area in back. CG and CP look very close. No way of telling exactly from here but Rob's CAD program can calculate the area exactly. CG/CP location might be worthwhile to look into. I have no way of knowing the CG location and it can be moved by relocating various mass as Rex mentioned. But those wheel covers do offer a good location if you have to add area to get the correct CP relationship.
PS: Enlarge the picture to see where I put the CG.
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« Last Edit: October 20, 2010, 02:04:10 AM by saltfever »
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joea
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« Reply #70 on: October 20, 2010, 08:52:07 AM » |
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salt fever....there is NO WAY they would allow the cog to be there....
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SPARKY
Global Moderator
Hero Member
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Age: 70
Location: Phoenix
Posts: 3635
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« Reply #71 on: October 20, 2010, 08:57:33 AM » |
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Do front inline wheels have a greater resistance to directional change than side by side  |
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WORDS to build by!
"--virtually the entire success of a turbo/engine system lies in thermal managemant."
Corky Bell MAXIMUM BOOST
" I am a firm believer in the people. If given the truth, they can be depended upon to meet any national crisis. The great point is to bring them the real facts." A. Lincoln
agendadocumentary.com
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JoshH
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« Reply #72 on: October 20, 2010, 10:03:38 AM » |
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CG and CP look very close. I don't think so. There is a ton of area out back. Consider the area of the wheel covers (inside/outside) and the airfoils (top/bottom). Lots of surface there. |
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Blue
Sr. Member
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Age: 51
Location: Sparks, NV
Posts: 383
Don't guess, TEST!
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« Reply #73 on: October 20, 2010, 12:31:19 PM » |
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OK, time to chime in. Yes, that CG estimate is pretty close. As JL222 and many other highly successful LSR racers have pointed out, it is good to have the weight as aft as you can stand it for traction. My job was to come up with a configuration that allowed a mid CG to be highly yaw stable. Al Teague and Craig Breedlove had done this with very similar configurations, so that's where I started. Far from this being some wild hair I pulled out of my a--, the configuration is based on actual, record setting, stable jet and wheel driven cars. We just moved the rear wheels out further than Al had them and moved the wing onto the rear axle.
The Cp (yaw neutral point) is located 3 to 4" aft of the leading edge of the rear wheel fairings. Three things that put the yaw neutral point father aft than expected from looking at the side view are (in order):
1. There are two tails. In the side view we only see one. For a back-of-the-napkin Cp, stack the second tail on top of the first one and then look at it.
2. Wing sections are neutral at their 25% chord point, while rounded objects (like the fuselage) are neutral further aft.
3. The Wheel fairings have span (vertical) and end-plate effect (the ground) that make their effective aspect ratio between 1.5 and 2. The fuselage has a lateral geometric (side view) aspect ratio of less than 1/10th of that and since it is rounded on the top and bottom and up off the ground it's contribution to yaw is only 2 to 3% of the effect of the wheel fairings.
The stability margin is 2 to 10X that of any of the current 400 mph club, and with the wing and adjustable flap we are looking for more than enough downforce on the rear wheels to exceed our available power. All of this comes with very little separation (exposed tire sections are about it), minimal wetted area, and lots of laminar flow. I'm not just designing it, I'm building the bodywork; so we'll see.
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"Doing the same thing as everyone else insures the same result", Shawn Fischer
"Extraordinary ideas do not come from ordinary thinking", Dan Bond
"Don't compromise, optimize", Eric Ahlstrom
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JoshH
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« Reply #74 on: October 20, 2010, 01:19:29 PM » |
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All of this comes with very little separation (exposed tire sections are about it), minimal wetted area, and lots of laminar flow.
The exhaust outlet could be tricky; its likely going to have significant interaction with the airfoils. Also the configuration makes the parachute packaging and deployment challenging. I won't ask about frontal area... |
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