transbrake=wheelstand "UPDATE"
#1379303
01/31/13 10:00 AM
01/31/13 10:00 AM
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Joined: Dec 2004
Posts: 415 New Braunfels, TX
416challenger
OP
mopar
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OP
mopar
Joined: Dec 2004
Posts: 415
New Braunfels, TX
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I have another post for "what will it run", but I figured I would start another to keep it separate. I installed my 418 into my dad's 85 Shelby Charger and now installed the transbrake. The car is a full tube car with ladder bars and non adjustable shocks. I was launching at 3000 rpm on the 2 step and the car wanted to stand up every pass. It seems to be dead hooking. What do you guys to to calm down the launch? More tire pressure,different launch rpm?
Last edited by 416challenger; 02/16/13 01:31 AM.
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Re: transbrake=wheelstand
[Re: 408strokerdart]
#1379306
01/31/13 12:04 PM
01/31/13 12:04 PM
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Joined: Dec 2004
Posts: 415 New Braunfels, TX
416challenger
OP
mopar
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OP
mopar
Joined: Dec 2004
Posts: 415
New Braunfels, TX
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Trans is a 727 with standard gear set, 4.30 rear gear and 29.5 x 11.5W tire. I have a video from a cell phone that is not very good, but I will see if I can post it.
Last edited by 416challenger; 01/31/13 12:05 PM.
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Re: transbrake=wheelstand
[Re: 416challenger]
#1379307
01/31/13 02:01 PM
01/31/13 02:01 PM
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Joined: Jan 2003
Posts: 684 St. Charles, MO.
Slingshot383
mopar
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mopar
Joined: Jan 2003
Posts: 684
St. Charles, MO.
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With the engine warmed up, with the car stopped, foot on brakes, put tranny in high gear, while watching the tach, floor it, and let off the gas right away. The highest rpm reading is your flash stall. Set your launch rpm 400 - 600 rpm under the flash stall. You'll shock the converter less than what you are now, and also the engine should be in it's sweet spot.
1994 Undercover Chassis 125" altered
stack injected big block, soon blown and injected
Member of The Torque and Recoil Club
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Re: transbrake=wheelstand
[Re: 416challenger]
#1379313
01/31/13 04:37 PM
01/31/13 04:37 PM
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Joined: Aug 2003
Posts: 43,185 Bend,OR USA
Cab_Burge
I Win
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I Win
Joined: Aug 2003
Posts: 43,185
Bend,OR USA
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Several things I have treid over the years to calm the car down on the starting line and limit the hieghts of the wheelies,stiffen up the front shocks or tie the front suspension down with a travel limiter,put the ladder bar in the lowest hole in the front, make the stall RPM as high as posiible so the motor CAN'T flash the converter at all, ie throttle on the floor on the trans brake when the first bulb lights up, WOT
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
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Re: transbrake=wheelstand
[Re: Cab_Burge]
#1379315
01/31/13 06:44 PM
01/31/13 06:44 PM
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Joined: Jan 2003
Posts: 10,000 Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,000
Frostbitefalls MN (Rocky&Bullw...
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One thing to consider is just how much starting line ratio you have. At a certain point, the car can pull the front into a wheelstand no matter what you do, if it gets traction. Here are the numbers from my car, and why I fought wheel stands for so long. 106 inch wheel base = 8.833 ft. 800 ft/lbs torque x converter multiplication(2)=1600 x low gear (2.45)= 3920 ft lbs x rear gear (4.56) = 17875 ft lbs x .90 (driveline loss) = 16087 net ft lbs torque at the hit. Rear tire radius is 33/2, or 16.5 inch. divide torque (16087) by tire radius, multiply by 12 inch, and you have the torque in ft lbs which acts against the whole car. Now divide that by the wheel base (8.833ft) and you know how much front end weight the car can DEAD LIFT, no spring help, etc. Mine comes out to 1324 lbs. With a front weight of only 1480, it doesn't take much help at all to go on the bumper instantly. When you figure in the fact that the torque is actually working against a center of gravity about 20 inches off the ground, it reduces the required lifting torque even more. You can move some weight forward, which to me is a better solution than tying the front down because you can shock the tires just enough to get the front in the air a bit, and after that the front/rear distribution does not mean a thing, the rear tires are carrying it all anyway. I made a change from 1480 on the front to 1600. That may seem like a lot, and it is. But the car is now controllable and very consistent. You could start with a big weight move, and see if more rpm will hook the tires. lighten the front back up as needed.
Last edited by gregsdart; 01/31/13 06:49 PM.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: transbrake=wheelstand
[Re: gregsdart]
#1379316
01/31/13 09:47 PM
01/31/13 09:47 PM
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Joined: Oct 2003
Posts: 21,345 Marysville, O-H-I-O
70Cuda383
Too Many Posts
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Too Many Posts
Joined: Oct 2003
Posts: 21,345
Marysville, O-H-I-O
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on the issue of weight distribution not mattering once the front wheels are in the air... what about the torque moment around the rear axle? a 35 lb batter over the rear axle has a torque moment of what..a foot? so it's a 35 ft/lb torque load....but if you put it way up front, that's 35 lbs times...10 feet? that's 350 ft lbs of "counter torque" I'm still trying to learn as much about how to set up suspensions as I can, but it would seem to me that even if you DO have both front wheels in the air, and all the weight is on the rear, that your weight distribution can still have an effect on controlling wheel stands also in that video...I agree, looks like he got squirley. does the car leave straight and the track had poor prep causing it to pull one way or the other? or does it do taht every time? it sounded like he had to let off the gas because of how out of shape it was getting.
**Photobucket sucks**
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Re: transbrake=wheelstand
[Re: 70Cuda383]
#1379317
01/31/13 09:57 PM
01/31/13 09:57 PM
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Joined: Jan 2003
Posts: 10,000 Frostbitefalls MN (Rocky&Bullw...
gregsdart
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,000
Frostbitefalls MN (Rocky&Bullw...
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Quote:
on the issue of weight distribution not mattering once the front wheels are in the air... what about the torque moment around the rear axle? a 35 lb batter over the rear axle has a torque moment of what..a foot? so it's a 35 ft/lb torque load....but if you put it way up front, that's 35 lbs times...10 feet? that's 350 ft lbs of "counter torque"
Funny you should mention the battery, because that is exactly what I moved, plus more. The battery was a 40 lb unit, and it went forward 140 inches. I also went lexan in the rear window(15 lb lighter) and a glass trunk lid, for another 35 lbs. The effect was more than the actual weight moved, because the distance moved was more than the wheel base. My car needs that much extra resistance to offset the huge amount of launch torque. It sure does look like of OPs car needs it too.
Last edited by gregsdart; 01/31/13 10:03 PM.
8..603 156 mph best, 2905 lbs 549, indy 572-13, alky
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Re: transbrake=wheelstand
[Re: 416challenger]
#1379319
02/01/13 12:15 AM
02/01/13 12:15 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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If the car was straight on the launch, you have too much pre load on the right bar... that will drive it to the left... increase in tire pressure will give you a controlled slippage at the tire... I dont know what pressure you have but try 1/2 pound increases till you tune it in... that'll get you up on the tire and should give you more MPH also... once you get it close then its 1/8 psi for final tune.... from your launch I would think its already in the lowest front hole... but if it isnt lower that .... the pic in my sig is great for pics but thats not how I normally leave... more like this pic... in this pic the RPM is lowered also
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Re: transbrake=wheelstand
[Re: tboomer]
#1379321
02/01/13 10:01 AM
02/01/13 10:01 AM
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Joined: Jun 2003
Posts: 52,972 Romeo MI
MR_P_BODY
Master
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Master
Joined: Jun 2003
Posts: 52,972
Romeo MI
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Quote:
Just a thought here..and Mr P. can confirm this! When I first started using a brake,my car was pulling to the left,too. And the guy that did my chassis work is one of the best in the business! Turned out to be driver error. I was so used to footbraking the car and always launched with both hands on the wheel. My button is on the wheel and when I let it go,the car would come down and always go to the left. I changed my technique by resting my left arm on the door bar and holding the wheel in the 8:00 o'clock position..Bingo! Problem solved! I was jerking the wheel to the left! Car goes straight as an arrow!
Yeah, many guys do that... I brace my elbow on the door window sill
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