Showing posts with label engineering. Show all posts
Showing posts with label engineering. Show all posts

Friday, October 11, 2019

TrashTeg, The Chronicles; Part 4: Home Depot Racing Sway Bar


Introduction

The Integra and Civic chassis that Honda produced from the late eighties to the early 2000s were set apart from average FWD cars because they could handle well out of the box.  With modification, they could handle even better.


One common problem with FWD cars is understeer.  Because the front wheels are doing the accelerating, turning, and the majority of stopping, the tires tend to "fall off" sooner than their RWD counterparts.  To combat this, FWD race car builders increase the chassis frequency, or "stiffness," of the rear of the car using sway bars or stiffer springs.

Photo of Chelsea the Civic Dog Legging by WindShadow Studios

In this post, readers will see how EJ2 Track Rat was able to create a low-budget solution for drivers looking to increase rear roll stiffness via use of a stiffer sway bar in the rear of the car.

Background

Alex's TrashTeg was driving fairly well.  He was able to pass competition school with NASA Northeast in it and he learned a fair amount about racecraft during the course of the season.  He was also having a ton of fun.  However, Alex was beginning to realize the limits of his budget-built car-- Partially because his car had too much dive, squat, and roll under braking, acceleration, and cornering, respectively.

Photo of TrashTeg Leaning by WindShadow Studios

When TrashTeg was first built, it had the following setup:
  • 205 Toyo RRs 
  • At a ride height of ~5.5-6 inches 
  • With a front spring rate of 650 pounds/inch,
  • Rear spring rate of 750 pounds/inch,
  • No front sway bar,
  • A 25 mm GodSpeed (eBay) rear sway bar,
  • And some Koni Sports he got for free from our friend Anthony
Our goal was to increase the roll stiffness of the car while still keeping the car controllable at the limits with a healthy amount of rotation in corners.  We had two options: increase front and rear spring rate, with a stiffer rear spring rate than front, or increase front spring rate and throw a big rear bar on.

Since I only had a pair of 800 pound/inch springs in my garage, we figured we'd throw the 800 pound/inch springs up front, and increase rear roll stiffness without springs.  The easiest way to do this is with a bigger sway bar, which A-Spec Racing (ASR) makes.  Their 32 mm hollow bars come in different thicknesses and since they're hollow, they have the advantage of less weight vs. their solid counterparts for the same amount of torsional resistance.

ASR Hollow Rear Sway Bar Kit

However, ASR bars are not cheap at ~$500 for a full kit and Alex had already purchased a $300 eBay sway bar kit.  He wasn't about to spend $500 more for the ASR product as a result.  But, he and I were both interested in doing something creative.

Getting Ready for some "Creativity" with a Welder

A while back, I saw a thread on a forum where a Miata driver welded additional metal to his/her sway bar to increase torsional resistance, thereby increasing chassis frequency at the respective end of the car.  

Much debate was had on this thread-- specifically whether one can weld to a sway bar and expect it to work because sway bars go through a forging process that allows them to become "spring steel."  Spring steel is highly malleable, but returns to the shape it was bent from fairly easily.  Welding to spring steel changes that property and increases brittleness.

Example of a Cracked Sway Bar (Not Ours)

Doing the Deed

Since we don't care about armchair engineers and we buy parts for our destined-for-doom race cars on eBay, we decided it'd be worth a go to attempt something similar.  The new setup would have the following changes: 
  • Ride height lowered to 5" at pinch welds
  • Front spring increased to 800 pounds per inch
  • A "custom" xxx mm solid rear sway bar, courtesy of the plumbing aisle at Home Depot
 We started by purchasing some steel black tubing with an inner diameter of 1" and a wall thickness of 0.133" for about $20.  A 1" inner diameter equates to 25.4 mm which is only slightly larger than the OD of our eBay sway bar.  

Our plan was to cut this bar to length so that it would fit between the pillowblocks that mount the sway bar to the subframe.  Then, we would cut the bar in half, length-wise, and weld half of the Home Depot pipe to the sway bar.  This would result in a solid sway bar with a diameter of ~28 mm.


Sway Bar Diagram from ASR

Our Plan from EJ2 Track Rat

We laid out the eBay sway bar after purchasing the pipe from Home Depot and we started by measuring where our addition would be and how short we'd need it cut.

Laying Out the Sway Bar

Next, we cut our Home Depot pipe to length using a cut-off wheel.  Ideally this would be done with a band saw, but with a pipe-vise it's easy to do with a $30 Harbor Freight cut-off wheel.  The cut just isn't as clean.

Alex Cutting Home Depot Pipe to Length

Next we cut the pipe in half, lengthwise using our cut-off wheel and our old school bench vise from eBay.

Cutting the Home Depot Pipe in Half Length-Wise

To weld our cut-off half of the Home Depot pipe to our eBay sway bar, we would need to first clamp the OD of the Home Depot bar to the sway bar.  After grinding the surface of the Home Depot pipe and the sway bar clean, we clamped the Home Depot bar to the sway bar using a set of Milwaukee vise grips.

Half of a Home Depot Pipe Clamped to an eBay Sway Bar

I ran a bead across a section to the left and right of the vise grip, then moved the vise grip down the length of the sway bar and repeated the process...the entire thing was done with flux wire.

Close-up of Beads Ran Next to Vise Grip

The entire bar welded up looked amusing, to say the least.  It really was also great practice for welding.  I needed some, so this was of benefit to me.

Picture 1 of Welded Sway

And Picture 2...

Finally, we sprayed the bar gloss black and mounted it onto the car.  Once on the car, we checked to ensure clearance between our modified bar and the subframe brace was satisfactory.

The Bar Mounted to the Subframe

Checking Fit with Bar at Full Droop

Checking Fit with Bar at Full Compression

And after installing the rear bar, we installed my front springs and manually set ride height as we always do-- the LoBuk way.

Alex Setting Ride Height to Clock Bushings

Another View of Alex Setting Ride Height to Clock Bushings

Impressions

Alex tested TrashTeg at Watkins Glen in October of 2019 with NASA NE to see how the changes improved the car.

Alex Suiting up for a Race at The Glen

On Track, he noticed sharper turn-in due to the stiffer front springs, but the larger rear sway also allowed the car to have less mid-corner push.  The new sway bar we created held up for a full weekend of abuse at one of the best and most demanding tracks in the Northeast.

After our racing shenanigans on Saturday we attended a NASA Northeast BBQ and had a good time.  The car held up, the mods made it faster, and we had a great time.

Me, Alex, Jeremy, and Yuko at the NASA NE BBQ

Until next time, thanks for reading!