More Street Rod question

[Craven]

Was thinking about building a street rod Pro and was looking at some of the older cars have a enclosed back wheel is that allowed sample is the 1951 Hirohata Mercury. I know the rules say no wheel covers is that what they are talking about.

I do think this vehicle is too long but I am just using it as an example.

 

[Jimmy & his 2 Kids]

I wondered the same thing. Looked at bodies just a few hours ago at the LHS. I might settle on 71 Torino. But I did look at older rods and wondered about the rear wheel cover.
Curious to get that answer.

 

[Quicktimederby]

That car would be legal, as long as the length wasn't to long. Here are the current rules http://npwdrl.boards.net/thread/7/street-rod-rules
The wheel covers are referring to tape or other material on the actual wheel.

 

[Jimmy & his 2 Kids]

Makes sense. Thanks for the explanation!

 

[Crash Enburn]

Pretty much as long as the car fits within length and width limits (8.25" and 3.5" respectively), you're good to go using the model as it comes. You just can't hack up the body for perceived benefit (chop top, drill holes in trunk, cover wheel openings with tape for aero, etc.)

 

[Craven]

Ok do I put my Tungsten cube on the pine undercarriage in the weight pocket like a normal pinewood derby car or do I put then in the body of the car/model. I can get the weight further back if I put it on the body of the car and that would moves my center of mass back. It would give it more motor/push but would run the risk of the front wheels being to light. What is the common practices, if there is one.

 

[Jimmy & his 2 Kids]

I would like to se the gurus answer on this one too. Seems to me the best bet would be following the existing general rule of getting center of gravity/mass in the same area consistent with size of the veh. Back enough to have proper rear (pushing) weight but not too far to get wheelies. So just doing the math accordingly if the model body increased length. Test tack would be so awesome here.

 

[Crash Enburn]

I've always put the weight as far back as I can get it. If you wind up with a CoM that is 0.5" or less, you can move the weight forward by the amount needed to get it to where you want it.

In the case of my avatar car, my chassis goes all the way to the back bumper, and I have my weight stacked up on the end of the chassis there. I also have a Lamborghini Diablo SR where, I first molded some lead and glued it into the back of the body, and then added the rest of the weights to the end of the chassis. I believe that currently both cars sit with a CoM that's a tiny bit more the 3/4" in front of the rear wheels.

Something with a long overhanging back end (like a Porsche 911 or a '57 Chevy) might run the risk of being a wheelie machine if you're not careful, but some double sided tape and a quick check on where your CoM lies is all you need.

 

[Quicktimederby]

Weight placement will depend on the car, within any build. (SR,SS,BASX,Ect.) From what I can remember on your SR was the distance of the NON DOM wheel from the rail, when the DOM wheel is on the rail. I believe that when your DOM wheel is on the rail your NON DOM wheel is close to 3/4 of a inch off the rail. When you have such a big gap and your car wiggles it allows the front of the car to move as much as that gap is. With that much of a gap 1 wiggle will cause another and another and your whole run is ruined. If you bring that NON DOM wheel in towards the DOM wheel and leave yourself a 1/8 inch gap I think you will be happy with the results. It will let you run a more aggressive COM, and use less steer and the car will still be stable. I have some insanely aggressive COM cars will little to no steer, all because of the NON DOM wheel. I like a 1/16th gap, but have a few even tighter. Oh ya and the key to a stable car is a good Foundation.(The drill/alignment)

 

[Craven]

Thank you Crash and QTD. All good info. I hopefully to have my drill/alignment fixed with the addition of a silver bullet pro to my tool box. I did not know the NDW spacing would effect the car. Thank you both again for the help. Existed to see the difference these changes will make.

 

[Stonecold Racing]

Excellent information from 2 of the best Street Rod builders.......another thing to watch out for is if you have a body that has a lot of hangover behind the rear wheels....and the body is low to the track....it WILL drag the rear bumper in the transition zone. Been there and done that. Very disappointing on race day. Good luck on your builds. Ask many, many questions.