How to properly launch a FED?

[dreracecar]

Years ago when cars had torsion suspension, the front axle would drop thus moving the spindle pivot and turning the wheel all while the driver had the steering straight. Driver would look at the turned front wheels and would correct the situation by turning the steering wheel- but when the car came back down the front would correct itself and head towards the wall. Look at some old dragster wheelstand pics. The Good drivers would turn the front wheels even further for the reverse action when the car would come down and the wheels would go the other way.

[Mister_Fitz]

My car has a torsion suspension at front, I will have to check for any "bump steer" effect when the axle unloads/loads.

I made some measurements on my wheelie bar today. It seams like it is about 2" off to the left. I guess it is to the right direction, to help unload the left wheel since the right one will be unloaded by the engine applying torque on the rear axle?
I will make the wheelie bar adjustable side ways asap. Is it a good idea to decrease the offset a bit since the car is pulling to the right?
One other thing I saw was that when the single wheelie bar is offset the wheelie bar wheel is no longer parallel to the car. Is this a problem? I have not seen any wheelie bars that is adjustable to compensate for this.

Tire speed is easy, start dropping tire pressure in 1/2# increments.  It'll eventually give you tire speed.  If i dead hook my tires on my 200" car, it'll drive the car in a random direction.

I do not really follow you on this one. Shouldn't I be adding pressure to eventually loose some traction with the harder tires and then get some tire speed?

How big is the window from starting to get tire speed to smoking the tires?

[Mister_Fitz]

Or...
Am I doing it the hard way now... Is it better to just leave the wheelie bar as it is, since it probably is fairly right. Pick a fixed launch rpm and only experiment with the tire pressure until I get some tire speed at the launch and see if the problem is gone?

[Dolmetsch]

If it were mine before I did anything else I would pull the axles and look at the splines. Even a fairly bad alignment should not cause a side launch  because in the car has any suds at all it is basically on the rear wheels at that moment. Only other possibility is you are correcting the steering during wheels up instead of letting it do its thing. Wheels flop to one side on most conventional steered cars. When I have a guest shoe in the car I always tell them Do Not correct steering on the launch. car will run straight on its own. Any back talk and their ride is cancelled. on mine when the front wheels come up the wheels flop left however when the car settles they are perfectly straight again with no correction.
Have a video of it that shows it very well.
don

[wideopen231]

I am assuming you have been over the whole car and looked for craked welds? Spool are all spline in good shape? About everytime I have had a car launch to one side or other more than once I found something broken Or had let someone work on chassis that caused it to bind up and act stupid,long story lots of cussing.
]Went from DNQ to number 2 (4th qualify round)on early shutoff after cutting 2 bars that we had been told was new rule.Before cutting the car acted like it was on crack,jumping all over the place. Just throwing thoughts out there since most other have been hit upon.

[Supercat]

Mr. Fitz. When you do your burnout and then back up how far do you go behind the starting line? The reason I ask is that "MANY" people back up to short and make track alignment corrections in a very short/too short a distance as they stage.
We back our 200" up to a crew member standing on the track side of the waterbox. We then make any alignment corrections in the first few feet as we pull forward, rolling as straight as possible for as long as possible to center the tires and chassis to the track.
When you make a moderate to strong correction durring final staging you put a twist or side load in the tires, lift the front and the car will center to the last big correction.

I too am chasing a wheel speed issue now but that should be corrected on the next time out. If the new convertor gets here in time. We launch at about 2500 rpm which is just too low for our combo.
Have fun and let us know what you find.

[BK]

My car has a torsion suspension at front, I will have to check for any "bump steer" effect when the axle unloads/loads.

I made some measurements on my wheelie bar today. It seams like it is about 2" off to the left. I guess it is to the right direction, to help unload the left wheel since the right one will be unloaded by the engine applying torque on the rear axle?
I will make the wheelie bar adjustable side ways asap. Is it a good idea to decrease the offset a bit since the car is pulling to the right?
One other thing I saw was that when the single wheelie bar is offset the wheelie bar wheel is no longer parallel to the car. Is this a problem? I have not seen any wheelie bars that is adjustable to compensate for this.

Tire speed is easy, start dropping tire pressure in 1/2# increments.  It'll eventually give you tire speed.  If i dead hook my tires on my 200" car, it'll drive the car in a random direction.

I do not really follow you on this one. Shouldn't I be adding pressure to eventually loose some traction with the harder tires and then get some tire speed?

How big is the window from starting to get tire speed to smoking the tires?

That's how it was explained to me. Engine torque unloading the right rear tire. My experience was bar to left, moves weight to right, car goes straight. Also I agree more air more wheel speed. But more air raises the wheelie bar. My guess is you weren't on the wheelie bar. 2" offset on bar sounds like plenty but not too much.

[slingshot383]

A softer (lower rpm) launch will make it easier to climb the ring gear.  You want to launch at 600 - 400 rpm under the converters stall speed.  And yes, it raise slicks air pressure @ 5 psi. increments until you start slipping the tire.  You really need somebody watching the car to help with that, shorter wheelie bar contact with pavement, less than 4 wrinkles of the slick at launch movement.  Those wrinkles are important clues also, they need to be in the lower front of the tire, and not behind axle centerline.   

[GlennLever]

Take a look, remember I am a low  HP dragster only running 8.00

Comments

[slingshot383]

Glen, your car looked good at Gateway, and that picture has the crush right where it's supposed to be low and in front of axle centerline.

[GlennLever]

Who are you and will you be at the HRR next week?

As of right now we will be going.

I'm not preregistered, but called NHRA and was told I can do that at the gate.

[Mister_Fitz]

A softer (lower rpm) launch will make it easier to climb the ring gear.  You want to launch at 600 - 400 rpm under the converters stall speed.  And yes, it raise slicks air pressure @ 5 psi. increments until you start slipping the tire.  You really need somebody watching the car to help with that, shorter wheelie bar contact with pavement, less than 4 wrinkles of the slick at launch movement.  Those wrinkles are important clues also, they need to be in the lower front of the tire, and not behind axle centerline.

I will try to launch 600 - 400 rpm bellow the converter stall speed next time I'm on the track.
In what range will a "normal" tire pressure be? I know it will depend on a lots of things, but it would be good to just have an idea. I have been running around 10-12PSI before. Wouldn't the tire pressure be very high if I increase with 5PSI a couple of times until I get some tire speed?

Take a look, remember I am a low  HP dragster only running 8.00

GlennLever, what is the size of your tires? How much pressure do you run in them?

[George]

My injected combo liked 6-7 psi with the Goodyear 8525. It was a SBC 640hp and weighed about 1500# wet with driver.

[jspell]

George, what ET / MPH did that set up run?  How high on the two-step?

[George]

Best Time: 5.08 ET. 1.06 60' . 138.mph. 1/8 mile Engine: SBC 23 degree. 100% Alky. 355CID. Cast Iron.
 Track: Central Illinois Dragway. Havana , Illinois
Vehicle: FED 223" 6.00 Cert. (owner)

5500-5800 launch rpm

Short block and Convertor are for sale. We built a blown combo. George