How to properly launch a FED?

[Mister_Fitz]

What is the best way to launch a FED?
I have an FED, old 60s Jr Fuel, that I'm racing with just for fun. My problem is that the FED tends to pull to the right (most of the times) when I let it go from the transbrake. I have tried some different launch rpms and different tire pressues with out finding something that I think works good enough.
I have a long distance to the nearest dragway so I get perhaps 10-15 passes a year. So it takes time to figure it all out by my self. So if any of you have any ideas I would really appreciate it.
The FED has 150" WB.
350" SBC, alcy injected
PG with transbrake
Chrysler 8-3/4" - 4.11 rear ratio
M&H Racemaster 12" x 33" x 15"

Once I get up to speed the car is stable.

Am I perhaps launching it to "gentle" so that the slicks hock up to soon/hard? Can I get this problem then?

How do you launch your FEDs?

[masracingtd1167]

The first thing you should do is check the circumference of the tire . Inflate the tire to the pressure you want and take a tape measure and measure both tires it should be within a 1/4 inch . If one is too small you can sometimes stretch the small one a little by inflating it to around 20 lbs and then let the air back out and check it again . If the tire is old this may not work .You may not want to hear this but with a car that short you really need a wheelie bar . With the tracks the way they are today and using an auto trans it just makes good sense to use one . I am not a big fan of changing tire pressure to make a car go straight but I know that some people do it . Could you borrow a smaller set of tires from someone to try I think it might help give you a little wheel speed and that will help a lot . When we ran the short wheelbase cars years ago  we ran a 10 inch tire and a clutch .I hope this helps you . Bill 

[ricardo1967]

This is a great topic, thanks for posting it Mr. Fitz .

I have done only three test passes so far in a dragster, my old FED (173", SBC 400, PG, transbrake, MT 3068W 31.0/10.5-15W M5, unknown rear axle ratio). They were all incomplete passes due to scary moments at launch (the local track is very narrow!). On my second pass I tried to 'tame' the launch by launching on 2nd (top) gear. It shot straight to the right side guard rail (didn't hit) and I aborted it. I realized that, because most of the cars at this track are door cars, with a wider tire tracks, I had mistakenly placed one tire on a stickier path than the other. Not sure if this could relate to your problem but thought about mentioning it anyway.

Does your car wheel stand? Do you have a wheelie bar? If so, the older 2-wheel style or the newer mono-wheel design?

[Mister_Fitz]

The rear tires are brand new and are within 1/4".
I allready have a wheelie bar. It has a singel wheel. According to my measurements the wheelie bar wheel is of center with about 1". I'm not sure how this affects the launch but I will make i adjustable and center it.
I also have a hard time knowing if the wheelie bar hits the track or not.
What is a good starting point for wheelie bar height?
What is the best way to get a good amount of wheel speed with the setup I have now?

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[Pipe Dreams]

 
Mr Fitz,  I had the same problem with my car when I first started running it. I tried lots of things, but the bigest thing I found that helped my car was lowering the wheelie bar. I run mine set at about 2 1/2" . You can also try differant tire pressures from side to side after you know your tire rollout. I run mine at the same pressures now, but running the right tire a 1/2 pound lower than the left also helped.

[dreracecar]

To easily verify what the wheelie bar is doing is by painting the wheel with shoe polish and to have someone on the crew veryfi the marks left on the track. you can pick up notes on ---
when the bar hit at launch and for how long, is the wheel steering the car?

[JrFuel Hayden]

Mr Fitz, I agree with Bruce, shoe polish on the wheelie bar wheel, and look at marks on the track after you take off. You can also use VHT wheelie bar spray, or I use kids side walk chauk. Also if you have a crew member video your runs have them shoot your wheelie bar tracks so you can watch.
I have run into a FED pulling to the right when I had one of my motors in a B/ND running in NHRA Comp, we fixed it for that event until we got the slick company to give us another pair, by running 1/2 pound more in the right slick.
Another good idea is to check rear end location by measuring wheel base on both sides, keeping in mind if your chassis has an offset front axle [ NHRA allows 2" offset]. I know a famous JrFuel driver that always commented on how much he had to "drive" the dragster that was built in the 80's, but when they had the car "front halfed " the chassis guy found the rear end was not square in the frame, so Don was very happy afterward that the car went straight. The very best thing to do if you think your race car is not plum is get it on a chassis jig.
The reason the wheelie bar height is important is if your bar is too high, and you have a tight converter, at launch you could be jerking you front end up hitting the wheelie bar hard thus unloading your slicks and maybe unloading your right slick more. Bruce is right about 2 1/2" height. It could also add to your problem if your wheelie bar is too stiff, thus adding to the unloading of your slicks. We use a 3 bar CM 5 feet long with no supports between the 3 tubes so it works like a spring and more gently pushes the front end down.
Another crazy thing that might be going on is since you are new to this FED deal is right after launch you may be looking for your shifter [ on the right ?] thus going to the right. After all you will go to where you are looking. 

Have Fun with your new project !
Jon Hansen, Hayden Wheels, and Hammer-Hansen-Hook JrFuel

[dreracecar]

A simple way of a quick check on the chassie is to string it
Both tires equal air pressure
String/cord from Home Depot/hardware store
Tie lenght to 2 heavy jackstands per side(3-4 feet longer than WB)
place 1 JS behind rear slick and adjust front JS so that the string "JUST TOUCHES" the front/rear sidewall,
Do that on both sides
Stand back to see what you have

Is 1 wheel towed in more? is the whole RE cocked? at this point you can check the front end toe by measureing each rim to the string. Front ends can be off , the import measurment is the difference between the front and rear of the rim be the same for both sides. 4 7/16 & 4 1/2  and 5 7/16 & 5 1/2 is still 1/8 toe and not dealing with 2" offset or the front axle off to one side

[ricardo1967]

All great input here, I'm following this thread very close.

I think one way to eliminate any chance of being tires' at fault is swapping their positions in the rear axle. Agree?

[masracingtd1167]

All great input here, I'm following this thread very close.

I think one way to eliminate any chance of being tires' at fault is swapping their positions in the rear axle. Agree?

      Very good idea !!

[Mister_Fitz]

Thanks for all the good and helpful answers!

I had a small impact with the track wall about a year ago, very narrow track. Then I built a chassis jig and straightened the chassis. After the repairs the wheelbase and the cross measurement of the wheelbase differed around 2mm, that's around 1/16". So I think that the chassis is as square as it can get.

I'm currently running about 1/4" - 1/2" of toe in. I know it is a bit much, but I thought I rather have to much then to little, the car would be more stable at high speed? Are there any down sides except the increased roll resistance?

I will try to get hold of some shoe polish to paint on the wheelie bar wheel. It is a very good idea.
How do I tell if the wheelie bar wheel is steering the car, or if the car is steering to the right for some other reason and the wheelie bar just follows?

I do not think that I'm steering the car to the right by mistake. I don't shift to 2nd until about 100-150 m out, so during the launch and the following seconds both hands are on the steering wheel.

I was just in my garage and I measured the roll out of the tires and I noticed that the left tire have changed allot since before the race previous weekend!
The tires are brand new and this weekend I put one burnout and one pass in them, both the pass and the burn out were actually quite gentle...
I have measured the roll out of the tires during 1-2 weeks in the garage, tires mounted to the rims, and they were within 1/8".
Now how ever has one of the tires expanded and the roll out differs a little more than 1"!! How is that even possible??
I have completely deflated the big tire and put about 21 PSI in the small one. I will try to inflate the small one even more and put it out in the sun for a while. Is it possible to get them back with in 1/8" again? Have some one heard of anything like this?
I do not think this sudden tire expansion completely explains the launch problem. Last 2-3 seasons I have had the same problem with my old set of tires.

My Race master tires have arrows on then so they are direction sensitive. Is it possible to swap them anyway? Or will the tires be damaged?

[dreracecar]

1/8" is nothing,  air pressure set at the last moment before you bring the car up into the fireup zone is the best. Direct sun on one tire will raise presssure on that one tire and not the other. Goodyear tires are only directional for the first strong hit to set the tire-after that they can be switched--dont know about M&H. Raise the bar and add more weight to the front and try again, if it does not turn its the bar

[gregm784]

I try and have someone video each run. After the video, i make sure they video the wheelie bar mark on the ground.  Pick a goofy color of chalk or shoe polish, so you know what mark is yours.

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.

[BK]

I had similar problem with my car. I ended up steering the car with the wheelie bar. When I had two wheels I would set the left wheel about an inch lower than the right. It would stop the left side letting more weight transfer to the right.  With the single wheel I would have the wheel 11/2 to 2 inches off to the left. I also ran a 1/4Lb more air on the right. Mine would dead hook and then unload the tires on the bar. To take some hit out I put a pneumatic cylinder with a needle valve on the throttle. Slowed the 60 foot a little but the car was deadly consistent. I was running Super Pro brackets so ET didn't mater that much.

[Lorbiecki]

1.) Is the car lifting the front end and then making a move? If so, look at wheelie bar alignment. We had a bar that was bent and it actually drove the car to the side.

2.) If it is not on the bar and going to the side, then all the above will effect it.

3.) Look at your driving techniques. I have seen people that actually turn the wheel without knowing it on the launch. Sounds weird, but sometimes when accelerating, the drive may use the steering wheel to support the hand and it will rotate unintentionally.

4.) Try to get the car to slightly spin the tire.

5.) I have been up to one PSI different between the two tires. Don't be afraid to do it!

Good luck...