Who has to use the original BSA slots??

[Pinewood Daddy]

Our District rules state the original slots must be used. This doesn't allow extending the wheel base or 3 piece construction.

[Stephen's Dad]

Do the rules specify "original wheelbase" or just "original slots must be used". Some builders cut the block into sections & reglue the slotted section where they want the wheels to be.

[Pinewood Daddy]

Do the rules specify "original wheelbase" or just "original slots must be used". Some builders cut the block into sections & reglue the slotted section where they want the wheels to be.

Actually it says "Axel grooves cannot be relocated or altered in any way." There are also pictures that show and say the wheelbase cannot be altered or the slots deepened. Very clear.

[clemsontigerfanatic]

Does anyone have a idea of how much distance extending the slots gives?
We have built cars that were the only car with a extended base. It did not win overall. It was not against the rules.

Always a bridesmaid never a bride.

[Pinewood Daddy]

Does anyone have a idea of how much distance extending the slots gives?

I built my first extended wheel base car (Open class) at 5.50". That's 1.125" longer than standard. The rear wheels are 1/32" from the back of the car. The front wheels are 1/4" from the front (in case the car hit something it hopefully wouldn't upset the alignment). You could probably stretch that another 1/8" comfortably.

[2kids10horses]

We have to use the slots, but I CAN cut some block off the back and add to the front. This moves my CM farther uphill, gaining a bit of potential energy.

2K10H

[clemsontigerfanatic]

Does anyone have a idea of how much distance extending the slots gives?

I built my first extended wheel base car (Open class) at 5.50". That's 1.125" longer than standard. The rear wheels are 1/32" from the back of the car. The front wheels are 1/4" from the front (in case the car hit something it hopefully wouldn't upset the alignment). You could probably stretch that another 1/8" comfortably.

I meant how much of a time advantage . Sorry

[PW Grasshopper]

Last year, district no and pack yes. This year, thankfully, district and pack no.

[WarpSpeedINC]

Does anyone have a idea of how much distance extending the slots gives?
We have built cars that were the only car with a extended base. It did not win overall. It was not against the rules.

Always a bridesmaid never a bride.

The extended wheelbase may only offer an advantage in stability, or the cars willingness to go where it is pointed (tracking width vs. wheelbase ratio). It loses some of it's advantage, by losing "fall time" of the weight on the front wheels.
If you have 1oz on the front wheel/s, as soon as the front wheels hit the flat, that 1oz of total weight is no longer accelerating the car. Now, we are only relying on the 4oz on the rear axles for acceleration. The longer you can get the most weight to fall, the faster (more energy) the car has the potential of going.
There may be a slight gain with the long wheelbase, due to more leverage (moment arm) to rotate the mass of the car at transition, but one of the many tallented engineers would have to chime it at this point.
We think you only need as long a wheelbase as your set-up / pieces / Track will allow.
Look at Wheeler Racing in the WIRL. Some of his fastest Mods. are short wheelbase!
Just keep those rear wheels as far from the starting pin as possible!!


Warp Speed

[2kids10horses]

Warp,

I agree with your analysis. We were able to move our axles back by cutting off the wood behind the rear wheel and moving it to the front.

Now, we placed two ounces of tungsten behind the rear axle. Doing this really weighted the rear end, so I had to place two ounces of tungsten about 2 inches in FRONT of the rear axle. I positioned it so that the balance point is about 3/4 inch in front of the rear axle.

I had hollowed out the body using a forstner bit, and it grieves me to say that there is empty air between the rear axle slot and where I had to place the weight to get the balance right.

It's too late to change the design now, but I'm wondering for next season:

Should I pass on putting weight behind the rear axle and concentrate all the weight just in front of the rear axle?

(My thinking was to have some weight in the "way back" for as long as I could to provide that extra energy push.) You know, I hadn't thought that by extending the nose of the car in the front, it moves the weight of the front wheels back, too!

2K10H

[joe]

While we're at it, there seem to be (at least) 2 other advantages to short wheelbase. If you're going to ride the rail, it doesn't seem advantageous to have a longer wheelbase - since principal effect is to increase the turning radius; i.e. keep the car off the rail for longer period.
If you shorten the wheelbase, you can back-weight more aggressively because the front wheels are closer to the COM. i.e. if you moved the weight back along with the front wheels you could keep the weight constant on the front wheel while moving the COM to the rear. Also, wouldn't the effect of a shorter wheelbase mean that the dominant wheel could be "straighter" since it will turn the car more easily to the rail? Perhaps not much, but it should give a very slight advantage. This would require a long, thin nose. I wonder if it would work?

[PWD]

We have very liberal district rules. We can put the wheels anywhere we want. It is funny what you get use to. It seems wrong to me to do it any other way. But it is really just what we have always done.

When first started looking at WIRL this is what bugged me the most. But in the end I really don't think it makes much difference.

[robinr123]

Mad River District (CT) rules:

"Wheelbase (distance between the
axles from front to rear) will remain at the as
delivered dimension of 4 3/8" +/- 1/8”. The
original slots in the wood block may be filled
and re-drilled to insure that they are
‘square’. But the original dimension must be
maintained."

[sprntrcr]

We don't have to use the slots, but must keep the stock wheelbase.

[Soxfanatik]

I moved the wheels to the far back and far front and my car is not as fast as it should be....