1/8 Scale Race Car Frame Original Design Build

[regular guy]

Decided to use 1/8 scale engine dirvetrain and supension parts I already have.

Put them on a board in the right relationship to each other and

start doing some visualizing.

Come up with a design to get started on.

Will post pictures of putting together parts first.

Edited July 12, 2017 by regular guy

[pharoah]

That ought to be impressive!  I might recommend  the 85 Corvette if you're building a sporty type car. A good start anyway.

[regular guy]

Things are taking shape.

1/8" basswood will be better than 1/8" Plastruct tubing glued end to end.

The basswood is a little stiffer than balsa.

Frame model is 18" overall.

108" wheelbase 1:1 scale.

Latest is designing passenger compartment wide.

Then 'pulling in' front and rear subframes for suspension.

[regular guy]

Things are coming into focus more now.

Drawing frame in Turbocad.

Drawing it 1/8 scale. That means frame is 24" inches long in drawing.

Not drawing it real world size and scaling it down with Turbocad tools.

Frame is a 'mule'. Test model to refine suspension.

This kind of suspension.

http://www.forgottenfiberglass.com/technical/chassisframeandsuspension/build-yourself-a-kurtis-style-chassis-hot-rod-magazine-july-1954/

Key here is 'inward facing links' not outward facing like on sprint car.

Our frame will be '4 tube' space frame not ladder frame like Kurtis.

[Ace-Garageguy]

 

Drawing it 1/8 scale. That means frame is 24" inches long in drawing.

That's 192 inches bare frame length in 1:1. Kinda huge for anything billed as a sports car or hot rod. It's about the same overall length as a 2001 Ford Explorer or a Lexus LS 430. If you have any body overhang front and rear, it's going to get really huge.

Consider that a '32 Ford has a 106" wheelbase, with an overall length of only 165.5". A '55 Corvette has a 102" wheelbase, and only a 167" overall length.

It's your design, and you can do anything you want, but some awareness of real-world car dimensions is good to have when you set out to make something new.

[pharoah]

Unusual suspension choice,but I guess it's a good one. I envisioned something more high tech . Are you going with a  front engine?

[Ace-Garageguy]

PS. The blueprints of the Kurtis chassis show it to be 157" long. 

That would only be 19.625" in 1/8 scale.

Still curious as to how you arrived at 24".

On another note, the solid axle / torsion bar suspension at both ends works well for a race car on a smooth track. It maintains zero camber change in roll, which is good, but it can tend to get upset having to deal with bumps and potholes found on real roads.

 

 

[regular guy]

 

'Are you going with a  front engine?'

Yes. Different versions straight 4, straight 6, small block and big block V8.

Straight 4 is for first version smaller car. Lighter weight tubing.

'found on real roads'

Made the decision to leave the Bucket T type thinking behind.

Build a race car type sports car.

Having the foundation for the torsion bars suspension out at the ends does load the frame at the ends.

Do you brace the heck out of car to make it rigid out there? No. I'm not going to.

It will result in a 'Flexi Flyer' type frame.

That's racing. Not made to go 100,000 miles.

[regular guy]

'how you arrived at 24".'

Sorry about that! Hate to see you waste all that effort. That work would have designed half my car.

The MULE is 24" long. 1/4 scale. 8 feet long. Suspension only.

That's to work out the frame sections for the suspension.

1/8 scale is 18" full car. 9' wheelbase w/18" overhang on both ends.

That is just a 'rough out' design. Fine tune it later.

Make drawing revisions in stages until it gets to a final form.

[regular guy]

[regular guy]

Here's Turbocad drawing of first frame tube.

Not much there but what is there is right.

.25" tubing. 1/4 inch square tubing.

24" long.

Will post more as I draw it.

 

[Ace-Garageguy]

It will result in a 'Flexi Flyer' type frame.

 

That's racing. Not made to go 100,000 miles.

That's 1930s design philosophy.

Race cars today strive for very a rigid structure (as do production cars). The simple reason is that it's much easier to tune suspension if you only have the suspension variables to contend with. Tuning suspension on a flexible chassis, where the chassis is moving and not stable, is at best an exercise in frustration.

If you're interested in the reasoning and engineering behind chassis design, this is still the best entry-level book in the field. It got me started in the right direction decades ago.

                                             

 

[DumpyDan]

Cool, will be keeping an eye on you about this one.  Looks way out of my league. 

[regular guy]

'Looks way out of my league.'

Then it's my fault for not explaining this right.

The whole idea is to get guys 'off the sidelines' and 'into the game'.

My projects are just this rearranged.

http://www.kingmidgetcarclub.org/junior.html

I found and bought for myself 13" rims that are 4 on 4 pattern and will fit on go kart hubs.

[regular guy]

I made the first step and signed up for some webhosting sites.

That's to put plans on there.

Frames can be made at a local welding shop.

One of the first 'sub projects' is simple single transverse (across the chassis) leaf spring and

single radius rod suspension.

Maybe all you can do with the sports car is bounce around the farm with it but

it builds skills for later projects.

[regular guy]

[regular guy]

I use Turbocad.

It's the most conservative CAD drawing program.

Other drawing programs will have so many features it will increase learning curve.

For simple projects you can use copier paper, a ruler and a square (to make right angles).

That will give you something to take to welding shop.

Just telling them can lead to getting back something that isn't what you had in mind.

 

[regular guy]

[regular guy]

Fixed the drawing.

This one is 96" x 30". 1" square tubing.

Its a 'mule' to work out front and rear suspension.

Next is to add 'stands' or 'pedestals' to hang links on.

Shooting for transverse leaf spring and single links.

Want to keep it as simple as possible to get it built.

It will be a 3/4 size real world race car with a little 4 cylinder engine.

[regular guy]

[regular guy]

Here is frame 'base' with 'uprights' drawn.

They are 18" tall. On top of frame tubes.

Idea is to put in a transverse leaf spring mount next.

That will locate the rearend and the front axle.

I've come around to 'laying out' from the rear to the front.

That allows for everything.

This is a suspension 'mule'.

Idea is to get the suspension right then add other sections of frame.

 

[regular guy]

The new design is 'quarter elliptical' springs.

In plain talk it is what we know as a leaf spring cut in half.

Here's the real world leaf spring.

https://www.etrailer.com/Trailer-Suspension/Universal-Group/SP-177275.html

Next is drawing the 'pads' or 'bases' for them.

[regular guy]

Progress report

1) Came around to 'Single leaf spring, single pair of links' suspension for each axle

Picture bucket T suspension in a sprint car tubular frame and that's about it.

Keep in mind this is a small race car. Triumph TR6 size or a tad bigger

2)This is more of a side note.

Lindberg Diamond Duster/SC 101 Roadster frame is a Kurtis SS kit car frame. Like the link up above.

I thought that was pretty darn interesting.

I would say the SC in that stands for Southern California and the 101 is for Highway 101 along the coast.

So you have a Southern California Highway 101 Roadster. Yep! That's cool!

[regular guy]

Update.

Sorted out a few things.

1 Front subchassis width formula.

2 Overall length formula

3 Cockpit dimensions

4 Decided to build a 'mule'. Solid suspension 'roller'.

That gives a green light to actually build something.

[regular guy]

UPDATE

Figured out making passenger compartment wide.

Keep rest of frame like an Indy car or Big car.

Putting crashbars at front and rear of passenger compartment.

That's so if a wheel gets knocked off and car slides it doesn't 'pogo stick' when it hits a sharp object.

That drawing is bottom loop.Car will have a top loop about the same.

 

 

Edited June 4, 2018 by regular guy