Splitters, Spoilers and Wings
My latest article in NASA‘s Speed News magazine is once again the featured subject on the cover! This article describes the basics of air dams, splitters, spoilers, and rear wings. Those are all practical and inexpensive additions with a good performance payoff in terms of lap time, and in terms of performance gain per dollar spent. It is an honor and a priviledge to be able to share my knowledge and experience with NASA’s racing membership. Many thanks to the staff and management of Speed News, and I look forward to future opportunities to contribute. Check out the article starting on page 34 by clicking here.
Speed Demon
Think Fast – The Racer’s Why-To Guide to Winning has been selected as one of Popular Mechanics “10 Racing Books to Channel Your Inner Speed Demon”! Here is what Phil Berg of Popular Mechanics has to say about Think Fast:
If you could tap the mind of a racer and engineer, you’d have a shortcut to learning all the different disciplines required to put together a well-rounded team from one point of view. Author Neil Roberts was an SCCA formula car road racer and an engineer for the Swift Indy car company. In addition to these accomplishments, in Think Fast Roberts translates engineer-speak to language the rest of us can relate to and apply to more of life’s tasks than just racing a car.
Not Fade Away
The March 2013 issue of NASA‘s Speed News e-zine features my article titled “Not Fade Away” as the cover subject for the issue. Many thanks to NASA and the Speed News staff for this honor. This article describes how and why air cooling of race car brakes makes a car with marginal brake cooling faster, safer, and less expensive to operate. It also describes how to add a brake cooling system to your racer. Click this link to read the issue, and stay tuned for more of my articles in future issues. I am honored and humbled by the opportunity to contribute to Speed News, and I look forward to each new issue.
Scratchin’ Faster
Paul Costas has done it again.
Two more Whelen US Time Trial Championship days at Texas World Speedway, two more wins, two more track records. He makes it look easy, especially considering that Scratcher is actually a simple, conservative, low budget track day car that is up against much more modern, sophisticated, and expensive machines. A big part of Scratcher’s performance is Paul’s driving skill and experience at TWS. The rest is a result of spending money on only the high-payoff performance items, clear thinking, and logical development. Paul and I have been educating each other for decades on our respective specialties, so it is especially gratifying to see him perform well on the race track.
This achievement has extended Paul’s win streak in Scratcher to a perfect 5 for 5: Five NARRA events, five TTU wins, five TWS track records.
Paul Costas’ 5 for 5 TTU trophy collection
I am sure that there will be many more opportunities to highlight Paul’s racing accomplishments as Scratcher’s development continues. For now, celebrating this win is great fun. Congrats to Witchdoctor Motorsports!
Big Goals, Thin Wallet
The February 2013 issue of NASA‘s Speed News e-zine includes my article entitled “Big Goals, Thin Wallet“. As you might imagine, it’s about how to economize your racing program where you can, but it’s also about selecting the few key items that you should splurge on. I have spent a lot of years and a lot of nickels and dimes shredding rubber into dust, and my results have taught me a thing or two about turning pennies into performance. I would like to thank Speed News for the opportunity to share what I have learned along the way, and I look forward to future opportunities to contribute.
Click and read! You just might like it.
Best of the Best
NASA‘s December 2012 issue of the e-zine Speed News is their “Best of the Best” issue, and it includes a reprint of my article ”Crude Tactics” from the October issue. It is an honor for my writing to be included in a “best of” issue.
I would like to thank the National Auto Sport Association and the editorial staff at Speed News for this compliment, and I look forward to more opportunities to contribute to Speed News in the coming months. Stay tuned for more!
Fan Mail
Here is a recent example of the positive feedback that I get about Think Fast – The Racer’s Why-To Guide to Winning.
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I received your book yesterday and just finished what I am certain is the first of many more readings. It is an excellent piece of work that takes up from where Carroll Smith left off so many years ago. My editions of Smith’s works are so dogged-eared that further reading now requires a certain delicacy.
It’s not only the information you provide, but the logical progression through each area and from one area to next that is exemplary. I am not an engineer by training nor any stretch of the imagination. My understanding of race cars began the day I brought home my first Formula Ford in 1971 and began taking it apart.
To to tell the truth, despite many rereadings of certain concepts in Smith’s books, there were always several concepts that I had trouble getting my head around. In at least two instances, you have wiped away the lack of understanding and made those things easy to grasp.
Again, my thanks for your effort to put this work together and make all that very important information available to the likes of myself.
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See what I mean about positive feedback? It’s downright humbling.
You can check out Think Fast, read several excerpts and reviews, and order a copy for yourself or a racer you know by clicking here:
Then, Now, and Soon
When the posts on this blog get less frequent, it means that a lot is going on behind the scenes. That has been the case for a long time, and it’s all good news!
I recently completed more than a year of consulting for the Northrop Grumman Corporation, helping develop a number of Unmanned Aerial Vehicles for military applications. Some of those aircraft are in the field now, saving the lives of America’s warriors at this very moment. Some are nearing completion, and others are in the early stages of development. Each aircraft will have an important role to perform for our military services. I would like to thank the key decision makers at Northrop who opened the door for me to contribute to the defense of the nation in some small way.
I recently began a long term assignment for Honda Performance Development, and I’m having an absolute blast in the process! Everything about it is better than I have experienced in a very long time: the environment, the clarity, the focus, the resources, the traditions, the history of excellence, and the freedom to innovate. Of course all of that is because the people are absolutely spectacular. Great things are coming from this group.
In addition to the projects that I can tell you about, there are more under way, but they are not ready for the spotlight just yet. One of those projects is absolutely spectacular and amazingly fun, so it’s hard for me not to tell you about it. When the time is right, I will.
As if all of that wasn’t enough, there is an amazingly excellent possbility for the future, but that is also way too early to talk about. The combination of all this engineering goodness then, now, and soon has me smiling all day every day. There has never been a better moment in my career.
A Thousand Faster Thinkers
Think Fast – The Racer’s Why-To Guide to Winning achieved a major milestone today: One thousand books delivered! A thousand thanks to each of you who bought a copy.
I certainly wasn’t expecting this, but the feedback about Think Fast has been absolutely 100% positive. I have been honored and flattered by your comments about the book, and I hope to continue learning from them as well.
The content in Think Fast must be fairly solid if it has stood up to the scrutiny of so many racers. Also, I must have gone to print with it at the right time since I have only thought of one detail that I should have included. It’s an important safety related detail, so here it is:
Your brake bias bar clevises should have flats on one side that will contact the sides of the brake pedal when the bias bar rotates more than about 15°. That will keep one brake circuit functioning if the other one fails. This requirement is in most rule books, but many of the bias bar assemblies that I see don’t look like they would be very effective if one circuit fails.
I had several goals in mind when I wrote Think Fast:
- Share what I have learned about race car engineering and driving at every level from autocross to the Indy 500
- Show readers what to focus on and what to skimp on so that they can afford to do what it takes to run with the lead pack
- Share the guidance that I have provided to a handful of Formula SAE teams with a wider audience
- Inspire at least one racer to pursue a career in race car engineering, and to teach that person some of the specialized details that they will need on the job
- Describe what it takes to create and implement a successful team-effort program in any field of endeavor, using the fundamental principles that racing teaches every competitor
- Open new doors for myself as a motorsports engineer and racing mentor
As far as I know, every one of those goals has been met in spectacular fashion. Are you the one person that I inspired? If you are, I would be delighted to learn about your adventure.
If you would like to learn more about Think Fast, and perhaps order a copy for yourself, here is the place to go:
Tripod Clocking
I’m a huge fan of tripod joints for high power applications. Tripods are one of the two common joint designs used on the ends of the halfshafts that connect the transmission to the drive wheels of a car with independent suspension. The other common joint type is a CV, or constant velocity joint. The reasons that I like tripods over CVs are that they are more efficient than CVs up to a joint angle of 8°, their service life in high-power applications is vastly greater, and they don’t need an exotic and annoying grease like Krytox in high power applications. Krytox is an amazing grease, but the only effective solvent for it is freon. Freon is not exactly a practical solvent. At Hall Racing, we went from having to do CV maintenance every day at the superspeedways to half-season inspection intervals with tripod joints. That made a giant difference in maintenance workload on the team.
When you are assembling tripod joints onto a halfshaft, you are faced with a choice. Since the coupling between the tripod and halfshaft is a spline, you can clock each tripod joint to any angle that the splines will line up. Should you align the two tripod joints on each halfshaft with each other, stagger them 60° apart, or just plug them on at a random angle?
Halfshaft assembly with aligned tripod clocking
Halfshaft assembly with 60° staggered tripod clocking
As it turns out, it does matter how the joints are clocked relative to each other, and that clocking depends on the driveline geometry and suspension alignment of your car. So, there is no one-size-fits-all answer to this question.
Many years ago, I performed a kinematic analysis of a tripod joint to find out what makes them tick, and if there were any oddities in the way they work. I learned some interesting things from that investigation:
- A tripod joint produces an exact 1:1 drive ratio all the way around, regardless of joint angle, so it is a true constant velocity joint.
- When the joint angle is not zero, the center of the tripod joint is offset from the housing axis. The joint center displacement increases with the joint angle.
- As the car moves down the track, the tripod center precesses in a circle around the housing axis at an average of 3 times the shaft speed. I call that an average speed because it accelerates slightly for 30°, then decelerates slightly through the next 30°, and so on.
The fact that the joint center is offset when there is a non-zero joint angle is a source of vibration. That vibration can be minimized by clocking the two joints on each halfshaft optimally. The optimal clocking will offset the two ends of the halfshaft in opposite directions, so that they will precess out of phase with each other, and the center of gravity of the halfshaft assembly won’t move much.
If the tripod clocking results in the two joint ends being offset in the same direction, it can produce a vibration that is severe enough to halt a test day at a high speed track. This happened to us at Hall Racing in 1994 at the Phoenix International Raceway mile oval. That was our first oval track test day with the new Reynard 94I, which was our first Indycar with tripod joints on the halfshafts. That’s the day that we discovered that on oval tracks, the tripod clocking had to be different on the left and right sides of the car, because the right side had negative camber and the left side had positive camber.
Here is the way to clock your tripod joints optimally:
If the two tripod joint angles on a halfshaft are in the same direction, then the tripod clocking should be staggered 60° in order to offset the two joint centers out of phase with each other. An example of driveline geometry that produces both joint angles in the same direction is a car with the diff center slightly below the axle center, negative camber, and a small or zero fore-aft offset between the axle center and the diff center. Here is a rear view illustration of that driveline geometry:
Driveline geometry with both halfshaft angles in the same direction
If the two tripod joint angles on a halfshaft are opposite to each other, then the tripod joint clocking should be aligned. That will offset the two joint centers out of phase with each other in order to minimize the movement of the CG of the assembly for minimum vibration. An example of driveline geometry that produces opposite joint angles is a car with the diff center above the axle center and negative camber. Another example is a car with a large fore-aft offset between the diff and the axle center. Still another example is a car with the diff center a long way below the axle center. Here is a rear view illustration of that:
Driveline geometry with opposite tripod joint angle directions
So, now you know how to clock your tripod joints when assembling them. I’ll bet that you didn’t think you would learn that today, did you?
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