What are the advantages / disadvantages of a long wheel based car?

Mister B Racing

Mister B Racing

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Nov 6, 2013
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Hello again everyone!

What are the advantages / disadvantages of a long wheel based car?

My very first car I am working on / rebuilding for the Street Stock Amateur class, has the rear axles drilled 5/8” from the rear of the body. The rear holes are canted so that the top of the rear wheels are in towards the centerline of the car. The front axles are drilled at 5-1/2” forward of the rear axles.

Thanks!

MRB (Steve)
 
Could I add that it's harder to get the COM to the back on a long wheelbase car? With four+ grams (two wheel's weight plus the axle's weight) so far out in front it makes it harder to build a tight COM.
 
bracketracer said:
Could I add that it's harder to get the COM to the back on a long wheelbase car? With four+ grams (two wheel's weight plus the axle's weight) so far out in front it makes it harder to build a tight COM.
Click to expand...

You are correct, but only to the extent of the weight of the wheel and axles. I don't think it's really that much of a disadvantage. 5 kids won SS at the 2012 National championships with a long wheelbase car.

I really don't know if there is so much as a disadvantage to a long wheelbase. I base that opinion on the 2012 SS Nationals race, 5 kids had the long wheelbase car and beat Johns car "Bruce" (Probably one of my favorite cars) with a short wheelbase in that race. So I really think if you build and tune the car to your wheelbase you'll be good. IMO /images/boards/smilies/smile.gif
 
At the 2012 Nationals the rules changed and allowed extended wheelbases and also the 2.0 gram wheels. That was the first race that allowed those changes... Most guys ran their standard short wheelbase cars and some probably with heavier wheels. My advantage back then is that I had ran long WB cars a lot and knew they were faster and I could cut my own wheels...

If that race should show you anything, it is that longer wheelbase cars and lighter wheels run faster.... Owens had a long WB car too....

Zeebs comments were spot on.... If I wrote the race on paper, a short wheelbase car with the rears all the way back should win, but in reality it doesn't work that way....

Bracketracer, you are correct that it is harder to get a small COM with the rears all the way back, but that is actually an advantage. With the rears all the way back you will have a larger COM and a more stable car with the weight placement the same as in a standard 4-3/8" WB set-up.... and by the way, trying to get a really small COM is a rookie mistake. I am sure the fastest racers don't fool around with trying to get a sub 1/2" COM.... 5/8"-7/8" COM is fine.... I never even check mine. Pack the rear of the car with 2 ounces of cubes, put the rest up front and leave 1/2 ounce or so for tuning...

It may surprise you, but I don't cut my weight pockets like most people. I cut out the entire area between my axles which allows me to place some more weight further back.... I don't think you can do this unless you glue in your weight.... that's why I always glue in my weight.
 
For those that have asked this is how I do it....

BODY.JPG

Before drilling I cut the weight pocket and glue in the weight.... I glue solid all of the weights behind the rear axle and (at least) the first row in front of the rear axle. You need to glue in the weights to keep the body rigid during drilling. You need to glue in the first row in front of the rear axle otherwise your drilling gets screwed up... I use the extra weight pocket in the front to add the remainder of the weight and to move around tungsten putty for the fastest car. I always use the exposed axle tips from below to rotate/install/remove/adjust gaps on the axles. I never touch the axle head or the area where the wheel rides.
 
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If I want to remove more weight from the body..... after weight is installed, drilling done and body shaped I flip over the car and use my same weight cutting process to hollow out an area on the underside of the car. I adjust my end mill bit to leave maybe 1/16" of wood on the top and I use my Silver Bullet fence to get the pocket straight. After the area is hollowed out I use expanding foam to fill the cavity. After it hardens I use a razor blade to cut it off flush with the bottom of the car and then cover the entire bottom with self adhesive paper.

body3.JPG
 
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Awesome tips/images/boards/smilies/thumb.gif Feels like Christmas came early!!
 
Thanks 5kids, unbelievable cool of you to share your skills and knowledge. And gentleman that's a 2.96 car I pretty sure
smile
 
053_zpse5bf3d52.jpg

Scott, thanks again for the tips and inspiration. Been in the shop most of the day and here's what I came up with. Needs a bit of fine tuning but overall it turned out pretty good.
Pictured are the 4 jigs and router table I built. Not as safe as routing from the top but I'm going to put some handles on the piece that holds the car- gotta keep my fingers intact/images/boards/smilies/biggrin.gif Sure feels good to have sawdust flying again! (oops-entered the wrong date)
 
Looks good! I've got to learn how to build a jig for routing out weight pockets like that. Time to find a class on building router jigs or just go the trial and error path.
 
Corvid - Man that is looking good ... Looks like your back in the groove!!!!

I love the SMELL of Pine Wood in the Morning!!!

Papa V
 
It took a lot of trial and error and I must admit I surprised myself that it worked. I can't even imagine attempting the x-factor style-man that looks challenging. First pic I've posted in a few years so I figured what the heck, glad you guys like it/images/boards/smilies/smile.gif
 
Corvid Racing said:
053_zpse5bf3d52.jpg

Scott, thanks again for the tips and inspiration. Been in the shop most of the day and here's what I came up with. Needs a bit of fine tuning but overall it turned out pretty good.
Pictured are the 4 jigs and router table I built. Not as safe as routing from the top but I'm going to put some handles on the piece that holds the car- gotta keep my fingers intact/images/boards/smilies/biggrin.gif Sure feels good to have sawdust flying again! (oops-entered the wrong date)
Click to expand...

Now that looks sweeeet Corvid!!!!

If I was being critical, the only thing I would change is that the ribs where the rear axles are drilled look too long.... 5/16" long is plenty. It is actually easier with a to install/remove/adjust axles with a shorter engagement area... and they will still be secure in the block. With the longer ribs like you have cut it is hard to grab the axle tip to move the axle.

Also, cutting the forward weight reduction pocket before shaping the car limits how thin you can make your car, so I cut that last...

but, Job well done though! Looks better than any bodies I have ever made!
 
Good deal!
Very helpful suggestions and not taken as critical one bit. Besides, without constructive criticism in life there'd be much more trial and error and learning the hard way. I'm digging the idea of easy axle removal and tuning- truly blown away at how freely knowledge is shared on this board- best ever/images/boards/smilies/smile.gif
 
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