Mid-Build Evaluation: On to the hard part-Alignment -Advice?

[resullivan]

If the rears are drilled canted and done correctly then no bend is required. If you have a drill press or even just a drill you can chuck the axle and tell pretty quick how straight it is. I have found it easier to go through a hand full of axles and find the straight ones vs using the axle press.

[Gregg H]

Stan, and resullivan, your last two posts were helpful. I was able to better (not perfect) direct my son to get alignment for this years Derby.

UPDATE: Today was our Den and Pack races and my Bear cub's car won it all! Now, we are not strangers to this, as my other two boys have also won the pack. As I mentioned, for several years they would qualify for the district race and then finish in the middle of the pack at that. My youngest, of course, wants to out-do his brothers. Now, this car did not set a track record, but it did win by open space on our 28ft wooden track. Our pack takes the single fastest time from each car and then ranks them. It isn't my preferred way to determining a champion but it is what everyone else wants to do. Districts averages your runs, which I think it better, but that is a different thread.

I have to say, this year I learned a new appreciation for how sensitive alignment can work and the interplay between the wheel, axle, and car body. This same son had a car that won his den and set a track record two years ago and we still have it intact for comparison on a little test track. Using that car as the control I was shocked at how different the results can be just by turning an axle, or changing a wheel. Prior to this I was just sticking them on without regard to alignment. I now realize we were just getting lucky. Getting close, but not getting as much as we could.

This car was a standard wheel base, three wheeled rail runner, with a COM at 3/8" of an inch. I was concerned it would jump the track as that was the most aggressive weighting I had ever used. I fully expected the rear-end to shimmy or "death wiggle" at the bottom of the slope, which it did. I still need to figure out how to eliminate that.

And now on to Districts (our council calls them regionals). We will need to build a new car as they have slightly different rules than the pack we are in does. Can't do much to the wheels but we can do anything we want to the axles. We must use slots, but their wording will leave an opening to cut the block and change the wheel base. I have a better idea about how to align for a railrider with bending the axles and drilling cant, and I still think I can improve the wheel bore and axle prep. Thanks for the advice.

[Speedster]

Gregg H, are you thinking of "shifting" the wheelbase (cutting off the back and moving it to the front) or "extending" the wheelbase (cutting the car in half and placing wood in the middle of the car)?

[Gregg H]

Gregg H, are you thinking of "shifting" the wheelbase (cutting off the back and moving it to the front) or "extending" the wheelbase (cutting the car in half and placing wood in the middle of the car)?

Speedster, my thought is to cut it in such a way (5/8" inch in front of the intended front slot (inbetween the two slots) of a stock block ) that I turn it around and get an extended wheel-base (not adding wood inbetween) and thereby creating an extended wheel-base. This diagram shows what I am doing: https://plus.google.com/u/0/photos/your ... 8808036275" target="_blank

I had posted in a different thread (http://www.derbytalk.com/viewtopic.php?f=11&t=7384" target="_blank) that the rules for our regional race state this: "The two pre-cut slots provided on the block of wood in the kit are the required location for placing the official BSA nail axles into the car. This is not optional." No reference to a wheelbase measurement is given, I checked with the race organizer about my interpretation and he concurred that what I am doing above falls within the wording of the rules.

Gregg

[Speedster]

If the race organizer OK'd it you should be fine.

[Gregg H]

Another Update: VICTORY at Regionals!

I want to start by thanking those who have commented on posts to help others learn from their past experiences. I have picked up a lot over the years. My youngest son only has one more derby year after this year, and we have had a lot of fun building fast cars. We wanted to "up our game" this year, and we did that. The third weekend in April we went to a "regional" race and my son won his rank easily - much more easily than our own pack even. Our council went with a different approach this year, and eliminated district races (there are 9 districts in the council) and instead did four regional races, of which the top three finishers qualified for the council final next weekend, May 10th.

We built a new car for regionals, as it and council uses a different set of rules. We did cut the car into two pieces and glued it together such that it created an extended wheel base. The other tweaks we made also went in (tungsten, thin body, spoon design, built for rail-riding, better axle and wheel prep, and then alignment. I learned alignment makes a huge difference and was our biggest improvement. With this car I went with much less cant in the rears (1 degree) and I think this is better. When we tested it against our home track record-setting car and adjusted the alignment in our test runs and it BLEW IT AWAY then I knew we were headed to the regional race with a very fast car. It never lost a race and after the averages were calculated it won by almost 2/10ths of a second on the 28 ft track, about 1 length of open or more to the 2nd place car. After the trophy presentation many of the other dads and scouts wanted to look at the car, and my son described to them the reasons the car was fast. No one else made an extended wheel-base like we did, and most of them left thinking that was the reason, though we both know the alignment for rail-riding was the biggest factor. Also, my son did a great job protecting the car, as this was a scout-loading type race, and he carried it around very carefully, never touching the wheels. At least a half dozen of them dropped their cars while waiting their turn to race.

This car has had all of a half dozen runs total in it's life, including the testing. It was boxed in it's carrier after the racing and hasn't been touched since. Should we bother trying to tweak anything? The COM was a very conservative 3/4", but it was solid with no wiggles and rode the rail perfectly. Should we mess with moving some weight around? Or should we just lube it up again and let it run at council? Is there a time-proven method of treating the car during a three week interval between races? I would love to hear some thoughts.

[birddog]

Greg H:

Congrats on the win and good luck next weekend!

I would not touch your car except for a re-lube the morning of the race. I've played with cars to try to get them better and actually ended up making them worse and not being able to get them to run as fast again. I wouldn't risk it given how well your car ran.

birddog

[FatSebastian]

I wouldn't risk it given how well your car ran.

I agree with birddog. Even if was possible to tweak the car to be a tad faster, it may result in set-backs along the way and thus take more effort than most kids have patience for.

[Stan Pope]

I agree with the advice unless your car suffered deterioration in performance during the last race.

I've shown you how to check your alignment. That check would be reasonable.

Then if the check shows misalignment (only if!) and you have learned how to bench align maybe then correct the misalignment.

Probably no realignment needed. Racing without incident ... struck by another car, run into a hard backstop, etc., should not hurt your alignment.

[Gregg H]

Thank you gents. You confirmed my intuition on this one. We will do a quick check on the alignment, re-lube, and let it fly!

[Gregg H]

Update: My son finished 3rd in the Council race last weekend! Having never made it beyond districts, where we would get trounced before, we were thrilled to have the car perform well enough to bring home a nice big trophy. We didn't adjust anything as was discussed earlier in this post. The car that finished first in my sons rank race (Bear) set the track record, so we have some fast competition. Examining the car after I suspect they were using lightened wheels as they seemed thinner, but I wasn't going to raise any issues. We did it right and were happy to get there and mostly just to improve the building skills that resulted in more speed. Thanks again for the advice guys. Our derby season is finished - only one more remaining before he advances.

[Stan Pope]

Congrats, Gregg & Jr!

[Speedster]

CONGRATULATIONS Gregg Team !!!! Might we see a picture of your car?