LocostUSA.com

As I dive into suspension designs I continue to find myself finding more interest in the solid front axle. Not because I think it is superior to any independent or McPherson strut design but because I want to try to replicate the style of the old Indy roadsters from the 50s - early 60s. Because of this, I find myself understanding why it's not common anymore due to its issues and restraints, however, I do find some pros that I think could outweigh some of the cons in a potential design...

1. low amount of pickup points to be located
2. Cheap to build
3. weight could possibly be equal if not less than a double-wishbone front
4. durability
5. no compromise between scrub radius and camber gain
6. generally simple-ish
7. parts are easy to find in the oval track racing aftermarket

There are of course many problems with this form of geometry which is usually dependent on what kind of linked suspension it is. Some examples are triangulated 4-link, Panhard bar, and Watts link.
This is when the problems begin. In my personal opinion, the Watts Link is a superior way to constrain the degrees of freedom of the axle. This is perfect for the rear but when it comes to the front end some big bump steer and roll steer problems occur.

Many if not all of the Indy Roadsters used a pitman arm and drag Link steering design. Something that is still heavily used on many different types of oval track racing. The idea hasn't changed for many years due to its simplicity and durability. But all of these racers use a Panhard bar front end due to the complexities of a Watts Link and drag Link. Something I haven't seen since the Indy Roadsters like the Bryant Cooling and Heating Special in 1962.

Now I do not want to design a car to only turn left but I want to create a design that can use the consistency of the Watts Link and still be able to travel without an excessive amount of bump steer. From my general understanding, the only way to go about succeeding in such a design is to match the angle and length of the drag Link to the trailing arms at ride height. This should in theory remove any binding and reduce if not eliminate any bump steer.

This is all just a hypothesis I tested in a simple inventor project. I have no idea the possible problems with this design and I wonder if anyone has some wisdom or information on the idea or if someone has built a Locost solid front end before?

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Look at a Jeep CJ. The pitman to spindle link runs laterally to the opposite side, making it as long as possible so the push-pull from vertical travel is reduced, like a panhard.

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Miata UBJ: ES-2074R('70s maz pickup)
Ford IFS viewtopic.php?f=5&t=13225&p=134742
Simple Spring select viewtopic.php?f=5&t=11815
LxWxHt
360LA 442E: 134.5x46x15
Lotus7:115x39x7.25
Tiger Avon:114x40x13.3-12.6
Champion/Book:114x42x11
Gibbs/Haynes:122x42x14
VoDou:113x44x14
McSorley 442:122x46x14
Collins 241:127x46x12

Ignoring camber control, the more practical issue is that it has a high unsprung weight. Said another way, hitting bumps will hurt more - how much so is subjective.

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Midlana book: Build this mid-engine Locost!, http://midlana.com/stuff/book/
Kimini book: Designing mid-engine cars using FWD drivetrains
Both available from https://www.lulu.com/

I do believe JD just flashed a big Thumbs Up in the sky at the mention of Arthur Mallock.

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Cheers, Tom

My Car9 build: viewtopic.php?f=35&t=14613
"It's the construction of the car-the sheer lunacy and joy of making diverse parts come together and work as one-that counts."
Ultima Spyder, Northstar 4.0, Porsche G50/52

Front beam axles pose an interesting dilemma. There is little accurate first hand information from reliable sources about them for our applications. Only a tiny fraction of people today have ever driven a beam axle car, and only a tiny fraction of them have done so on one 'optimized' for sporting use. So basically, take anything anybody says about them with a large grain of salt.

I actually have put a lot of thought into ways I'd like to try implementing a front beam axle, in part to perform a bit of 'mythbusting' on it.

One of the (if not 'the') best internet discussions on higher performance front beam axles for cars can be found here:
https://www.fsae.com/forums/showthread.php?1324-Beam-Axles-Front-Rear-or-both

I almost hesitate to post this, since I have come to some different conclusions in the years since, but we also had a decent discussion on the subject years ago: https://www.locostusa.com/forums/viewtopic.php?f=53&t=9417

As I recall, the Mallocks weren't actually beam axles. They were swing axles made from cut up beam axles.

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-Justin

"Orville Wright did not have a pilots license." - Gordon MacKenzie

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