Rear wheels

[BlewBYu]

Other than local rules dictating, is there any reason to put the wheels any distance other than 5/8 of an inch from the rear of the car body? By putting the wheels as far back as possible, it allows a tremendous amount of weight in the rear, as well as being stable because of the extended wheel base.

 

[Crash Enburn]

The point of it is to allow the CoM to be pushed as far back from the pin (as high up the hill) as possible and still result in a stable car.

The position of the rear wheels does not dictate an extended wheelbase or not. Our BSA cars all ran stock wheelbase with the rears at 5/8".

As far as possible reasons not to:

• Rules require original axle positions
• You are not trying to win
• You're building a Street Rod, and the rear wheels are further forward

 

[ngyoung]

No. there really isn't any reason not to if your rules don't prohibit it. Only reason not to other then rules is if the scout himself wants to do a design that needs them in a different location.

 

[NeedforSpeed]

I would see no reason to have the wheel anywhere but 5/8 from the rear. This post talks about it:

http://www.pinewoodderbyonline.com/post/why-are-rear-wheels-so-far-forward-6759808?highlight=rear+wheel&pid=1281569713#post1281569713

 

[Obsessedderbydad]

Also the longer the wheels are on the slope the more PE you have

 

[BulldogRacing]

what if you were putting 3 rows of cubes behind the axles?

 

[TRE]

what if you were putting 3 rows of cubes behind the axles?

Thats too much weight

 

[Obsessedderbydad]

I've seen it done before, but you can't with a 5/8" from the rear wheel.

 

[Crash Enburn]

Technically, the position of the rear wheels has nothing to do with the actual potential energy. The position of them, however, does allow a car to make better use of that energy. The PE has to do with how high the weight is. Period. However, if your CoM is behind the rear wheels, you have a wheelie machine that is completely incapable of making use of that energy.

You want the wheels as far back as possible to then be able to get the CoM as far back (high) as possible and still be stable.

Also, if your body is 1/2" or more, you can stack the cubes in back... (But you wouldn't want either the thickness or that much mass).

 

[Vitamin K]

The one situation that I can see for where you'd want to move the rears up is if you're experimenting with a fender design that tapers behind the rear wheel. However as far as I know, there's not been any proven speed benefit to this.

 

[Obsessedderbydad]

Technically, the position of the rear wheels has nothing to do with the actual potential energy. The position of them, however, does allow a car to make better use of that energy. The PE has to do with how high the weight is. Period. However, if your CoM is behind the rear wheels, you have a wheelie machine that is completely incapable of making use of that energy.

You want the wheels as far back as possible to then be able to get the CoM as far back (high) as possible and still be stable.

Also, if your body is 1/2" or more, you can stack the cubes in back... (But you wouldn't want either the thickness or that much mass).

Yes you're right the PE comes from the weight. I was looking at it the same way you're saying it. You'll impact your PE more by keeping the wheels on the slope longer