How would you design a late model ?

[croston71]

If you aspired to be a dirt late model chassis builder how would you go about the task?

1. Get a con senses of the generally accepted center of gravity & start with the left or right frame rail. No, start at the front & work your way to the tail. Possibly begin on the tail & run frame rails forward to the front.
2. Start on the outside & proceed inward assuring the center of gravity never gravitates while giving lateral reinforcement.
3.Position the center of gravity in the co-median & plot all intrigueal adjoining components!
4. Ask god !

[hpmaster]

Do what I think most people do. Copy what you understand and know how to make work then modify and improve what you don't like or understand about that design.

[croston71]

My thought is when a chassis builder/driver starts believeing he or she is going to make/force a defective design work/win he or she has already lost cause-train of thought!

[MasterSbilt_Racer]

When you start from scratch designing any racing vehicle, you design the suspension first. Once you know where those pickup points will go in space, you design a chassis to support those points and to hold all the necessary components that it takes to move the chassis. I would design something that looks nothing like a current DLM.

[croston71]

Again?! I think a point from which all other il-lust-rations can be attached in a logical & numerical sequence for form & function!

[Ronin]

This is how I approached the design of our racecar:

Step 1 - study the rules to ensure you understand them.
Step 2 - study the rules again to identify any loophole that you can exploit to your advantage
Step 3 - design the front suspension keeping in mind the intended wheel offset as this will affect the suspension characteristics.
Step 4 - design the rear suspension allowing alot of scope for adjustments. Because your design works on paper (or CAD) it does not mean it will work in practice.
Step 5 - Mount the large parts in space to calculate the center of gravity. These include engine, transmission, fuel cell, radiator and driver. Also mount the shocks in space as you need to know where the mounts on the chassis should be.
Step 6 - design the chassis frame around everything else.

Cheers
Arno

[hpmaster]

My thought is when a chassis builder/driver starts believeing he or she is going to make/force a defective design work/win he or she has already lost cause-train of thought!

First you may be very wrong to think a design is "defective" to start with. The constrants, large componets, construction materials and rule restrictions have already been addressed in virtualy all modern chassis designs. Trying to reinvent the wheel shows how little a designer may understand these factors. Check out the Cadillac CTS or the Ford GT 40 design stories.

[EAMShater]

i cant wait til someone comes out with another canitlever car like the old custom chassis that frank mcclendon built back in i think the late 80's early 90's. now those were crazy. or something like the daytone prototypes with the shocks mounted over the rearend facing outward and the motor in the back with dual independent rear suspension. we cant stay 4 link forever. something has to be better.

[zeroracing]

The four link we currently use creates a large amount of forward traction, all the other road racing types typically don't need to so have not been made too in the past. I am not sure how you could tune an inboard type suspension for the level of traction we need, in addition you would see a return to old old school flat cars, those cars get minimal body roll, to get large suspension travel the linkage would become too large and hard to fit within everything, given each pieces motion paths.

[EAMShater]

I saw an old custom chassis car a few years ago in a shop owned by greg brown of phenix city and it was ran at EAMS back when they still ran supers on a reg saturday night and he and bobby thomas would go at it every saturday night. idk what king of suspension it was but it had rods that ran up and down behind the axle tubes and on the top connected to a shock somehow that ran horizontally in the car facing frontwards on both sides. it had a pull bar type deal in it over the rear end that was about 5 feet long in it that connected almost by the front of the deck on the frame and from all the stories i've heard that car was unbeatable at EAMS in the mud he and bobby thomas would turn lets just say 15.20's as an example and bobby would be close in the old jigalo cars but when it dried off that car never lost a bit of speed and would still turn the same relative times while all the other cars would fall off tremendously. i would just love to see that car run. frank was a heck of a designer and one of the smartest men in dirt racing. not many have heard of him but he and c.j. rayburn worked together alot from what i've heard and you can ask any chassis builder and tell them your from phenix city or columbus georgia and they'll ask if you know him or how he's doin. he now has nothing to do with racing(thanks to the Thomas family at EAMS i believe) but he does still do machine work at a head shop here in columbus. I am only 21 and have been racing full size late models for about 4 years and have sure heard alot of stories about him. Terrance Nowell is a good friend of mine and we go to each other's shops alot helping one another and he drove for him for sometime and he said his front ends to this day are better than any that you would ever drive and thats what made his cars. the rears were kinda crazy with all the cantilever stuff and all cause the man hated 4 bars and torque arms even tho from what everyone around here says he built the first of each and said theyre junk and still believes that to this day but the man could design a front end they said.

[MasterSbilt_Racer]

The four link we currently use creates a large amount of forward traction, all the other road racing types typically don't need to so have not been made too in the past. I am not sure how you could tune an inboard type suspension for the level of traction we need, in addition you would see a return to old old school flat cars, those cars get minimal body roll, to get large suspension travel the linkage would become too large and hard to fit within everything, given each pieces motion paths.

I don't think a lot of forward traction is really needed. You don't need ANY if you don't slow down. A 4 wheel independent suspension car would smoke what we have today and it wouldn't be able to use a lift bar or pull bar.

[MADCAPRACING22]

Thank you EAMShater dude! I have been screaming for years that I would like to bring back a Custom Chassis! Ricky Williams has one still that his son ran in crate. It was a 4 bar. Mr. Richard Turner had one sitting behind his shop that had some Rocket 4 link brackets welded on it. Dean Garland drove it and wrecked it. I tried to talk him out of it but my buddy Cowboy told me I was living a pipe dream trying to bring that rust bucket back. I wish I would have scooped it up because he sent it to the scrap yard. Them Custom Chassis were the thing back in the day! I thought Greg Brown was a Rayburn man in those days. He ran good at Seven Flags too! That Cantilever is very interesting and I think still has potential.

[EAMShater]

Good luck getting frank to build one lol. From what I hear he don't even wanna look at a dirt track car. But as far as the Rayburn and greg browns I ain't sure. Too young to know. I just love hearing all the stories and I know what I seen in that shop was a custom chassis built by frank mcclendon with an all aluminum runion racing motor in it. But frank and c.j. were pretty close back in the day from the stories told. I would love to chop the front end off my bwrc and weld his onto it and see what happens

[croston71]

I helped a guy who ran a cantilever(Rayburn Chassis)it was very interesting. I believe wieght may be a factor by today's standards. I remember the car being very difficult to push. I believe we may have been too soft on the spring setup = rolling resistance=poor gas mileage. I read that Indy cars use a cantilever setup in the front end turned sideways so weight may be able to be trimmed with composite materials.
4 bar is hard to beat but as I see it a guy who releases the throttle at corner entry allows the rearend to square itself when the lr is most desperately needed to drive the rearend to the right. I see the cars a a balance beam the control is put in the driver's hands by a properly adjusted front end. I guys I see at the track seem interested in the rear end only. Am I the only person who visualizes the the mechanical aspects in this manner?

[MasterSbilt_Racer]

An Indy car uses a system with bellcranks that get the shock/spring combo up in the chassis and parallel with the ground. The advantage is that much of this mass becomes sprung weight versus unsprung weight. A cantilever is much the same concept. I have always been intrigued about building a dirt car with similar design ideas. You could easily build a car where the roll stiffness and spring rate at each wheel were totally independent adjustments.

[dualdj1]

An Indy car uses a system with bellcranks that get the shock/spring combo up in the chassis and parallel with the ground. The advantage is that much of this mass becomes sprung weight versus unsprung weight. A cantilever is much the same concept. I have always been intrigued about building a dirt car with similar design ideas. You could easily build a car where the roll stiffness and spring rate at each wheel were totally independent adjustments.

Sounds like you need to get busy

It's an interesting through process though, cause there's only so many ways you can attach a solid axle to a car and generate thrust to move the car. It's all about positioning and thrust angles.

[racin6mod]

I've designed and built my own modified. the first thing to do is get the rule book for the class and that will set your wheel base and alot of other points like motor set back chassis ht,wt even the width and from that you can start with the rest.I've take two years and used my old car as a test bed for some of the idea's. even won with what some might call off the wall ideas.

[cassellracing24]

#4....I would ask God what Bloomquist is doing....

[Ronin]

Sorry to focus on one aspect of this discussion, but here in South Africa our premier dirt oval class primarily uses independant rear suspension. The suspensions mostly come from road going Mercedes cars (mid-80's) as the components are very strong. Our racing is full contact, so cars must be strong. I know these suspensions are not the most effective as they are transfered straight from the road cars, but they are cheap to biuld and maintain.

There is a slow change towards 4-link rear suspensions. Our car will not be the first, but the few already running a 4-link setup is so much quicker than the independant cars. A 4-link car running an almost standard 327 is much quicker than an independant car running a 600hp+ 383. Keep in mind that we use 206/65/16 road car tyres, so traction is more important than power.

Remember that in an independant setup you cannot easily control the steering of the rear wheels. Also, considering the body roll you will most likely loose wheel contact area with the ground and experience large camber changes. Keep in mind that the j-bar adds side bite whilst the torque/lift arm also aids traction. It will be difficult to recreate these forces with independant suspensions. I am not saying that there is nothing better than a 4-link, but it will take some clever thinking to build a suspension system that is more adaptable than it.

Arno

[gdaagent]

The problem with Frank is that he would never build the same car twice. Some may like that, but he likes to experiment too much. He could have been nationally known if he would have become a chassis manufacturer. It took him too long to build just one. I saw one at Mack Waugh's shop in LaGrange a few years ago. Old cantilever suspension.

He was very smart but never consistent. Experiment at someone else's expense.