Category Archives: Uncategorized

Revisiting understeer

 

Frankster left a comment on my previous post regarding understeer and looking where you want to go, and I thought it interesting enough to post here:

“Look where you want to go” does not apply to understeer. You are already looking and steering in the direction you want to go, but it’s not happening because you’ve lost front end traction.

If you continue look in the direction you want to turn and steer that way (around the curve) you will continue or even increase the understeer situation. You need to momentarily steer LESS in the direction you want to go until the front wheels regain traction.

Good point, Frank, I should have been a bit more clear. I didn’t mean you can look where you want to go and you will magically go there without any other actions. Obviously you need to consciously use the throttle, brakes, and steering.

But from a racing perspective, I don’t agree completely with what you’re saying.

In an understeer situation, there are theoretically two ways to correct it – either reduce the steering angle as you point out, or reduce throttle. Let’s look at both of these in more detail.

Reducing steering angle will obviously reduce understeer, and in the Safeway parking lot, this will work great. However, on the track, if you reduce steering angle, you will drive off the track…remember, we’re at the limit here, and we were already planning to exit the curve with about 12 inches or less to spare between the car and the edge of the track. In some cases the edge of the track is dirt, but in other cases it’s a concrete wall. There’s no room to open the steering wheel.

The other option is to reduce throttle. This shifts weight forward, onto the front tires, increasing their grip. Understeer is thus reduced, and the line around the turn tightens. We’ve lost some time by lifting off the throttle, but we’re still on the track. Don’t get crazy with the lift, though, or the car will start rotating – you’ll go from understeer to oversteer in a heartbeat. More on this below.

So what does this have to do with where you’re looking? If you’re looking where you want to go, and lifting off the throttle to keep the car on the track, you will naturally tend to lift just the right amount. Too little, you drive off the track. Too much, you’ve lost more time than you had to. And at the same time, you’re making steering corrections – definitely look where you want to go.

Incidentally, when most folks start understeering, their natural reaction is to lift off the throttle. This is why most street cars tend towards understeer when you drive them off the lot – it’s generally safer for the average Joe in most situations.

Of course, you can also forget the steering correction altogether, and use throttle to kick out the rear
end.

Frank wasn’t specific about how to use the throttle in this case, so let’s look at both possibilities.

First, you could stomp on the throttle. If you have lots of horsepower, you might be able to break the rear end loose, and go from an understeer situation to power oversteer. This could work in some situations, but in most cases at the cornering limit of the car you will bump up against the laws of physics and go flying off the track.

Second, you could lift off the throttle to “kick out the rear end”.  Definitely possible – if you do an abrupt lift in mid-turn, the rear end of the car will get very light (remember, all the weight shifted forward) and typically start coming around. The trick here is to get back on the throttle at just the right time and the right amount to get weight back on the rear tires without breaking them loose, or you just might loop it all the way around. That said, a quick lift like this is often a good way to clear up a mild-to-moderate understeer with minimal time loss under racing conditions. I say “under racing conditions” because during qualifying, the lap is probably shot. And on the street, just lift slowly and carefully. :-)

 

PPIR national

I’m back home now. So how did the national go? Well, it rained (hard) about an hour before our race.
Things were pretty dry for the race, though, except for a couple of places with standing water. I qualified second (that’s getting to be a habit!), and led going into turn 2. Kim and I went side by side for a couple of turns, and he ended up ahead. We stayed nose-to-tail for 4 or 5 laps, pulling about a 5 second lead over the cars behind us. Then, for the next few laps, we started battling, passing each other a couple of times every lap, going side-by-side through much of the infield, with a net result of going about a second a lap slower (you can’t go quite as fast with a car next to you!). This, of course, allowed the cars behind us to catch back up.

Turn 1 on the road course configuration at PPIR is a full-throttle 4th gear turn, if you get it right. If you don’t, you have to lift a little. Along about lap 10, I was on an unfortunate line through the turn, and had to lift oh ever so slightly (about half an inch of accelerater pedal travel); unfortunately, Dean was about a foot off my bumper and got by as a result. I followed him for a while, trying to be smart – if we kept drafting with each other, and didn’t try to battle it out, we’d catch up to Kim…and I was thinking if Dean and Kim started dicing a little, I could drive by both of them. Great plan, right?

Well, unfortunately Dean didn’t get close enough to Kim to try to pass. And I didn’t get an obvious opportunity to get back by Dean. So there’s about 5 or so laps left, and I’m noticing that I’m gaining on these two by going a little deeper and braking later into turn 2. So I do this for a couple of laps, all is going well, I’m picking up a little ground. Then I try going even faster in there, and lock up
all four wheels…needless to say, you lose a LOT of time when you do something like that. Well, what do you know, Brian gets up next to me. I consider a defensive line through the next couple of turns, but decided against it. Back out on the front straightaway, checked flag! Oh no…I totally missed the one lap to go marker. Screwed!

So I finished 4th. Looking back, I can point to mistakes I made that cost positions, and I can also see opportunities that I should have pressed. Somehow it’s much more clear, as I sit here typing this, than when you’re going 100 mph six inches from another car. Heh.

Note to self: never, ever, EVER go out again for a national race without the radio in the car. I’ve said this before…this time I mean it.

Second again

Another interesting day…practice was fine, if a bit cool. During qualifying, I lost my transmission…ok, well I didn’t lose it literally, but it wasn’t working very well. Had to get a new one put in before the race. That’s a part of racing you have to get used to – things don’t last like they do in your street car. I think the transmission probably had 13-15 race weekends on it. If you want to run in the front in our class, you’re looking at 1-2 motors and 1 transmission per year, on average. Not to mention an entire set of tires for each national race, on average.

So crap, after all that, I finished second again today. I qualified second, led part of the first lap, and then Kim got by again, and he stayed about 3 car lengths ahead for the remainder of the race. :-( Tomorrow is the day that really counts – Sat and Sun have been regionals, but Monday is a national. Hopefully car and driver will work well together tomorrow and win the race! :-)

Just out of curiousity, do you loyal readers enjoy reading a mix of racing and technical stuff here? I could create categories, I suppose, but I’d rather not…

Racing this weekend

Wow…what a day. I’m racing this weekend at Pikes Peak International Raceway; there are regionals on Saturday and Sunday, and a national on Monday. In today’s regional, I qualified 2nd, 0.6 seconds off the pole (which is a lot – I was a bit disappointed). What a race, though – definitely the best race I’ve had in a long time. Kim (another guy in the CO region) and I pulled away from the pack, were pretty much nose-to-tail the entire race, passed each other probably 4 or 5 times each, and spent a lot of time side by side. At the end, he just got me – by about 3 feet (no exaggeration!), 0.05 seconds. So close!

On the bright side, though, I now hold the track record at PPIR for our class of car. Kim’s fastest
lap today was 0.002 seconds slower than mine. :-) We’ll see if my first track record holds through the weekend!

Weblog changes

I’ve changed a couple
of things about this weblog.


First, in the referrer
listings I keep with each post, I am now filtering out search engine referrers.
They were not only filling up the lists, but there were an interesting problem
with it. I had one post a while back where someone searched for “google
toolbar”, and went through enough pages in google to get to my site. Now, the
posted article had nothing to do with the google toolbar, but happened to have
both words in it. When this first visitor came in, I logged his referrer, and
displayed on that page “Google search results: google toolbar” or something like
that. Well, of course this was indexed, which sent more traffic to that post
from people searching for that phrase, which logged those
referrers…and pretty soon it had wormed its way to the top 2 or 3 hits in
google for that particular search. Not really a good thing, since my post had
nothing to do with what those people were probably looking
for.


I may add search
referrers back later (I’m still logging them, just not displaying them) but in a
different way…I’d show the search terms, and aggregate together all the
queries for those terms into a single line.  So no matter how many hits we
got for “britney spears”, it would only show up once.  This code isn’t
there yet, so for now, they’re suppressed. Sorry!


Second, both RSS feeds
on this site now support ETags, which should reduce bandwidth a lot. So, if you
notice anything strange in your aggregator, or you miss a post (how would you
know? hmm) let me know. This site is the test bed, before the code goes to
newsgator.com. :-)

Email and Weblogs

With most news aggregators available today, you can read weblog posts.

NewsGator 1.1 offers excellent integration with Outlook; and given a weblog post, you can forward it via email.

Tomorrow, May 20, 2003, everything changes.

NewsGator 1.2. Available Tuesday.

Slashdot and getting there from here

In a post about
programming languages and XML, Don
Box says
:



the real challenge is bringing
hoards of developers who jumped on the OO train and believe that no other
approach to design or implementation is reasonable.

So true. I think
this really started a few years ago (remember MTS?) when developers needed
to start thinking about separating data and operations. The idea of this
separation, while being arguably anti-classic-OO, has become more and more
important as time has gone on. Transactional COM+ systems…web services…the
list continues.

Nested Constructs in Regular Expressions

Today I was looking for a way to do nested expression matching with regular expressions, and pretty much came up empty. Then after a trip to the bookstore to pick up Mastering Regular Expressions by Jeffrey Friedl, I finally found it.

Interestingly, even now that I know what to search for :-), I can’t find a single reference to this on the net or on MSDN.

With the .NET regular expression evaluator, there are (?<DEPTH>) and (?<-DEPTH>) constructs that you can use to match nested expressions; for example, if you want to find matching parentheses, or matching HTML tags. Here’s a “simple” example that will match nested <div> tags:

<div> (?><div (?<DEPTH>) | </div (?<-DEPTH>) | .? )* (?(DEPTH)(?!))</div>

Which will match the part in red below:

<div>this is some <div>red</div>text</div></div></div>

This is pretty cool, I’ve got to say. I really can’t do this justice; if you’re interested, I recommend you pick up the book!

How should aggregators work?

(warning: blatant
NewsGator plug ahead!) Ok, so I’m a little
bit behind. :-) In a
post back in April, Dave
Winer says:



RSS readers that work like Usenet
readers
are a waste of time, imho. Aggregators should not
organize news by where items came from, just
present
the news in reverse chronologic order.


He got some agreement, and some disagreement.
My vote?
Why not use an aggregator that will do
both
?

Full text searching in aggregators

Addy Santo suggests that aggregators support full text searching:

Is anyone out there willing to take on a real challenge?  Then how about adding full text indexing into your aggregators!

Yet another advantage for NewsGator…full-text searching through all of your saved news posts. Or even do complex searches involving certain fields, categories, date ranges, etc. And if you don’t want to limit your search to news posts, you can search your email at the same time, too. :-)