Landracing Forum

East Coast Timing Association => ECTA General Chat => Topic started by: mxnuke on January 19, 2015, 11:06:48 AM

Title: vehicle weight
Post by: mxnuke on January 19, 2015, 11:06:48 AM
How does weight effect a car in the standing mile? With the car still pulling past 1 mile, is less vehicle weight better ? If you have traction. I'm new to this so i hate to ask but i want to give this a try [ i did a search first ]. Thanks
Title: Re: vehicle weight
Post by: fredvance on January 19, 2015, 01:34:26 PM
In the standing mile, on pavement, less weight is better. The longer the track the less important weight is.
Title: Re: vehicle weight
Post by: 55chevr on January 19, 2015, 02:54:13 PM
The paved courses are basically a long drag race. I suggest launch hard and hold the higher gears to the red line before shifting.  The salt flats are another matter.  With 2 miles to get speed you can recover from a short shift and vehicle weight is less of a factor.

Joe
Title: Re: vehicle weight
Post by: greenjunk on January 19, 2015, 09:09:09 PM
Not sure how much experience these guys have with cars, but i have not seen weight really matter.  I've seen 3000lb cars run the same speed as 4000lb cars.  What matters is aero, and traction.  Now I'll say i'm talking about cars capable of running over 190mph in the mile.  I can run within 1mph of a car with little aero and huge power as my car with lots of aero and little power.  I know this because we proved it each running 4 passes over 200mph in one meet.  Under 175 what actually matters is having the appropriate amount of tire spin off the line.  I don't quite understand the physics of it, but just like drag racing wheel spin yields MPH.  As much as 10mph could be had in a 150-160mph car.
Title: Re: vehicle weight
Post by: fredvance on January 20, 2015, 03:23:37 PM
At the last Texas Mile, Brenda Sue, on one run, spun the tire pretty much most of 1st gear. It was her slowest speed of the meet.
Title: Re: vehicle weight
Post by: mxnuke on January 20, 2015, 06:42:29 PM
Thank you guy's for your input.I'm sure you get lot's of questions from newb's like me,but the long winter gives me time to think [ not good ].My car is power limited,ran 124 mph in the 1/4 last fall.So now i have to update safety equipment and tires,but i'm working on it.Would love to be done in time to run the 1/2 mile event to sort out car and get my feet wet.Keeping the front to rear weight bias may be better than the overall weight to a point,but i hope to get car to 3200 lbs.Any input will help,thank's
Title: Re: vehicle weight
Post by: Jack Gifford on January 21, 2015, 01:02:15 AM
... wheel spin yields MPH...
:? At Maxton, I was told that ECTA frowned on any tire spin. [Was I too naive to realize someone was 'jes a foolin' wit' me?]
Title: Re: vehicle weight
Post by: jacksoni on January 21, 2015, 08:15:16 AM
... wheel spin yields MPH...
:? At Maxton, I was told that ECTA frowned on any tire spin. [Was I too naive to realize someone was 'jes a foolin' wit' me?]
True- tends to spray the cars lined up behind you, not to mention staff and spectators with gravel/sand etc.

First time at Wilmington with my current car did not have a limited slip- and the usual LSR skinny tires. When given the go signal, I gently let out the clutch and fed it gas. Didn't move. I went "oh crap, the clutch is slipping". Gradually started to move and then made the run without further incident. My crew member in support truck behind me said I disappeared in a cloud of smoke as I lit up the right rear.  :cheers: Nobody said anything but this is frowned on.   :-P :roll:
Title: Re: vehicle weight
Post by: 55chevr on January 21, 2015, 08:31:38 AM
What is frowned upon is burn outs to heat tires.  There are people staging behind you and this will shower them with whatever is kicked up.
Title: Re: vehicle weight
Post by: redhotracing on January 21, 2015, 09:43:22 AM
What is frowned upon is burn outs to heat tires.  There are people staging behind you and this will shower them with whatever is kicked up.

x2

"Launching" the car (ie drag racing) is frowned upon, given the propensity to spray rubber, gravel, et cetera towards those lined up behind you.
Coming off of a push truck (or under your own power) "HARD" enough to spin the tires is okay... You're usually 100 ft or so down the track at
that point, anyways. I was VERY sideways for the first 1/10 mile on my last 203 run, no one said anything except "add weight!"
Title: Re: vehicle weight
Post by: entropy on January 21, 2015, 10:15:08 AM
At the last Texas Mile, Brenda Sue, on one run, spun the tire pretty much most of 1st gear. It was her slowest speed of the meet.

Fred,
(about bikes)
we have had this discussion before , we agreed to disagree... 
Simply spinning the tire doesn't do anything. 
But with big hp, spinning it correctly, using rpm correctly, riding correctly, can make a big difference.
AND weight can make a big difference in the Mile, if the bike is ridden correctly
Karl
Title: Re: vehicle weight
Post by: fredvance on January 21, 2015, 01:31:43 PM
Us disagree! Are you saying less weight is better or vice versa?
Title: Re: vehicle weight
Post by: Stan Back on January 21, 2015, 02:39:09 PM
It takes less power to accelerate less weight.  So -- as long as you're hooked up, less is more better.  So how much do you need -- well try this . . .

Vehicle weight (in stones) x tire contact patch (inches wide / mm long) x number of drive wheels x final gear ratio (to third decimal)

over

coefficient of drag x frontal area (in decimal hectares) x peak horse(gelding)power

equals terminal speed (not taking in clutch slippage, tire growth, traction slippage nor intent).


You're welcome.
Title: Re: vehicle weight
Post by: Geo on January 21, 2015, 02:47:14 PM
Hey Stan,

Applying this to your car I get about 285. Is that about right?

Converted that's 1,995 Henweigh.

Geo
Title: Re: vehicle weight
Post by: Stan Back on January 21, 2015, 03:17:05 PM
What's a henweigh?
Title: Re: vehicle weight
Post by: Ron Gibson on January 21, 2015, 03:26:50 PM
Wouldn't that depend on if it is flying or not?

Ron
Title: Re: vehicle weight
Post by: Stan Back on January 21, 2015, 03:38:06 PM
Don't know.  I got kinda lost on the Point of Interest, Force of Mass, Direction of Vector thread.
Title: Re: vehicle weight
Post by: Elmo Rodge on January 21, 2015, 05:24:21 PM
About 2 pounds, Stan.  :dhorse: Wayno
Title: Re: vehicle weight
Post by: Captthundarr on January 21, 2015, 09:54:52 PM
As we get Amys' car faster weight placement has become the new learning curve. 2013 her then new best speed of 144. she commented on the rear of the car feeling light so we add 145# of lead the rear bumper frame ('91 camaro) 2014 new top speed 159.348 she was happy with the added weight to the rear and the car was on "rails", her words. totalt car weight 2665# wet. this year looking for about 185.0mph then we'll see. don't want to get it much heavier. my 2cents.all I got.
Title: Re: vehicle weight
Post by: entropy on January 22, 2015, 02:03:52 AM
Us disagree! Are you saying less weight is better or vice versa?
hey Fred, i was talking about tire spin on asphalt.
on weight: IMO less is always better if it is in the right place
karl
Title: Re: vehicle weight
Post by: roadracer on January 22, 2015, 12:12:41 PM
When I ran 184 on the mile and 190 on the 1.5 mile I weighed 168 lbs.  I gained some weight and couldn't get over 183 on the mile and 186 on th 1.5 mile.  I lost wight again for last season down to 170 lbs.  186 on the mile.  Didn't get to run the 1.5 mile. 
I also would spin my 998 on almost every run.  A controlled wheel slip from a hard launch. The bike would bracket race 205-206 0n the mile and 210-211 on the 1.5 mile if you rode it that way.
For my bikes a hard launch and less weight is huge.
Title: Re: vehicle weight
Post by: fredvance on January 22, 2015, 05:24:54 PM
Hey Karl, ok we agree on the weight. :cheers: I never spun the little motors, and haven't run the big motor on pavement. Brenda,, seemingly leaves slow. By about 20ft she is at full throttle. Works pretty good. She is doing some drag racing so we are looking for better starts. Having a 115lb rider really helps.
Title: Re: vehicle weight
Post by: greenjunk on January 22, 2015, 05:59:00 PM
frank, 2600lb? my god thats light.  i thought i needed to add weight at 3200# with our car.  keiths weighs over 4000#
Title: Re: vehicle weight
Post by: Captthundarr on January 22, 2015, 06:07:51 PM
The thing is gutted and the only weight added was to the rear last year. When I started building for the mile I kept the "extended drag race" concept in mind. Don't need heavy for traction mostly balance. We have enough aero force on the front but as speeds increase we noticed some lift in the rear so we are sneaking up on it. I've seen folks haze the tires at the big end in wilmington in 3500+ pound car. Some of that was HP but some was due to some lift at speed.
Title: Re: vehicle weight
Post by: greenjunk on January 22, 2015, 06:42:38 PM
its almost all due to lift