How fast with short wheelbase?

[masracingtd1167]

Ok here is something to think about . Two fed's both cars weigh 1600 lbs one is 160 w.b. the other is 200w.b. same motor same distance away from rear centerline . The shorter car will have more weight on the front wheel's ! What dose this have to do with anything ? I am not really shure just felt like typing something . 

[GlennLever]

Ok here is something to think about . Two fed's both cars weigh 1600 lbs one is 160 w.b. the other is 200w.b. same motor same distance away from rear centerline . The shorter car will have more weight on the front wheel's ! What dose this have to do with anything ? I am not really shure just felt like typing something .

Ok, I'm tired, was supposed to do club racing last night and it was called off as I was leaving the house (rain), I was up at four and at the swap meet grounds to prepare at five, it was 53 degrees at two PM, I was supposed to do test and tune after the swap meet, but was just cold, and I was just to tired.

I do not think you are correct, the front and rear tires will carry the same weight regardless of the wheel base.

[George]

No expert here but I have used a friends electronic scales on all four corners on our FED. Moving weight around makes a difference . We put the Optima battery inside the nose piece ( in front of the wheels).

[GlennLever]

No expert here but I have used a friends electronic scales on all four corners on our FED. Moving weight around makes a difference . We put the Optima battery inside the nose piece ( in front of the wheels).

Correct, moving weight around, forward and backward in the chassis would effect weight bias.

This is not the question raised.

Weight remanins the same in two different chassis, rear axle center remains the same, forward engine placement remains the same, the difference is the length of the chassis (distance between the front and rear wheels) Distance between the front of the engine and the rear wheels remains the same. Weight on all four wheels would remain the same regardless of the length of the chassis. Move the engine forwar and that would change.

I think??.

[wideopen231]

Ok here is something to think about . Two fed's both cars weigh 1600 lbs one is 160 w.b. the other is 200w.b. same motor same distance away from rear centerline . The shorter car will have more weight on the front wheel's ! What dose this have to do with anything ? I am not really shure just felt like typing something .

Ok, I'm tired, was supposed to do club racing last night and it was called off as I was leaving the house (rain), I was up at four and at the swap meet grounds to prepare at five, it was 53 degrees at two PM, I was supposed to do test and tune after the swap meet, but was just cold, and I was just to tired.

I do not think you are correct, the front and rear tires will carry the same weight regardless of the wheel base.

 IMO if front end is farther out it will have less effective weight especailly under power,that just simple physics(leverage).The rear wheels have more levarge on front end while trying to pick it up.

  I grabbed front end today and raised the front up about a foot without a lot of effort, I know on our funny carI could not have done it  and motors are close to same distance.Now Im not small guy but Im not powerlifter either.
  I would also think the more effective weight underpower would help handling if anything.

[Dolmetsch]

OK. Now we are getting somewhere.
When I am in good traction and if I run my tires too low my car will pull the wheels on launch so the tail or bottom of the cage smacks the ground.  Of course the first instinct would be some sort of wheelie bar but that tends to hurt traction a bit since it has to to some extent unload the tires the amount of pressure the wheelie bar/s are taking. The alternative is to make the chassis longer without increasing weight. In my case since the car is a bit overbuilt (1 5/8" mild steel .120" min DOM ) that is possible. However That is not what I wanted so I elected to run the tires no less then 9 psi which deals with the problem for me nicely.
Many of the early Altered and such handled badly because of the high center of gravity and a lack of understanding of Automotive suspension design.  Many very short road cars will do over a buck fifty and handle like a dream. It is not the wheelbase that is the problem. Or lets put it this way , It is entirely possible and practical to make a short wheelbase car , even a rail handle well. Air does not much enter into it if it is a open tube frame car (no body frward of the motor) Some of things done to rails of front suspension would make even a good sports car squirrely if it was set up that way.  They are all done with good intentions but sometimes excessive is excessive. Extreme caster angles , no ackerman , fast ratio steering arms and zero toe sometimes take the suspension or alignment into extreme areas where it is probably not wise to be. I know not everyone will agree but it is part  my trade by profession so you will excuse me if I hope.  Sometimes things are just done that way because the other guy did it that way.  Not a good enuf reason I think. The two fellows who also drove my car  are used to longer cars. One drove a successful RED (225 inch) for years. (I supplied his engines. Actually I am happy to be able to say ENGINE) The other runs a 160 inch FED with a injected BBChevy currently. Both offered the comment without any asking on my part. They were surprised.  If you check the ride along video you will see that even in the traps there is not any sign of ill handling. It is rock solid straight.  I have see lots of video if those 90 to 120 inch cars running straight and strong back in the day. I have also seen some bad ones but generally altereds not rails as I recall.  Bottom line is does the front axle know or care how close it is to the rear? Probably not would be my opinion. It cares about its alignment.
Don

[Pipe Dreams]

   Just one more thought to throw into the mix. In a front engine dragster we set behind the rear wheels, so the drivers weight also needs needs to be added to the equation.
   When we weighed my car on a set of four corner electric  scales the weight on the front wheels was  10 pounds lighter after I had gotten into the car.

[GlennLever]

The whole premise of the question was the only difference between the two vehicles was the wheel base.

[rooman]

If overall weight is the same and the motor is in the same place the long wheelbase car will have less static weight on the front wheels because they are further from the engine mass which is usually the biggest chunk of weight in the car. Think about a big kid and a little one on a teeter-toter (see-saw). The little kid needs to be further away from the pivot point to counteract the big kid's weight.
As Pipe Dreams commented, he added his weight to the car but the front end got lighter due to the fact that his body mass was pretty much all behind the rear axle centerline. 
 Taking an extreme example, if the front wheels were moved back to a point in line with the front crank pulley the static weight on them would be higher than on the rear wheels even if you clipped the frame off and made the car lighter overall. It is all about where the center of mass is related to the contact patches.

Roo

[GlennLever]

If the total weight of the vehicle does not change and the weight distribution on the rear wheels does not change how can the weight of the front wheels change?

See below?

[rooman]

That is the point, the weight on the rear wheels will increase as the fronts are moved further away from the center of mass. The CG will move back relative to the center of the wheelbase and will add to the amount carried by the rear wheels. Try it with a 2 x 4 and a pair of bathroom scales. Put a brick on the 2 x 4 near one scale and then move the other scale incrementally further away from the brick--overall weight will stay the same but the bias will move towards the scale with the brick closest. (The 2 x 4 should be sitting on something that will allow it to pivot somewhat in the longitudinal axis.

[coupemerc]

Good discussion and excellent explanation/analogy by Roo. It explains the basic evolution of all out dragster chassis design. Wheel bases got longer so they could optimize three things... put more weight on the rear, control wheel stands (wheelbase X front end weight) and minimize overall  car weight. Very generally, the longer cars have the POTENTIAL to put more power to the ground earlier in the run and that translates to quicker ETs.

[masracingtd1167]

Great discussion guy's ! A lot of good input from everyone !

[wideopen231]

Hey guys NHRA rule book allows 300 inch fed in T/D. Would make one awsome looking car,bad part your but would be at mph when tires where at finishline.

[janjon]

I believe the engineering concept as relates to wheelbase, with weight being equal, is "polar moment of inertia". Swing a short stick in a small arc, versus swinging a much longer one of the same weight. The longer one takes more effort to start the swing, and to stop it, since mass, even though it is less mass, is farther from the center of rotation. In our case, the differential centerline, or thereabouts.