Last minute tuning, what to expect.

[Eric]

Me and my son built his first PWD car, it is a three wheeled rail rider, front left wheel and right front has just a guide pin. I did not have a tuning board so we went in kind of blind to our test and tune night a few nights ago and the car looks pretty good after some steering adjustment. It is running 2.42 - 2.43 over a half dozen runs on a 32ft wood track. I recorded video of four runs, two from the starting line and two from the finish line. After we got home we started watching the video in slow motion. As soon as the start pins dropped the car went immediately to the rail. I found 5kids PDF of the tuning graphic and printed it out. Test our car on the tuning board and it has almost 14 inches of steer over 48 inches. If I dial that back to 3 to 5 inches will their be any negative effects? I am looking for another track to put a few more runs on it but his race is Saturday. I want to gain some speed but not sure if I want to go into it blindly. Thanks for any input.

Eric

 

[Rocket car]

A lot depends on your C.O.M. I would not dial it back that far on a wooden track because of the ruffiness of the track. 3-5" it might wiggle and you will be slower than just leaving it alone. I would play it safe and stay around 7-9" Again depending on your COM.

 

[Eric]

This is how the weights are in the car, front is to the left and rear to the right. The three weights that are in the triangle are no longer there, I removed two and slid the remaing one down into the corner. I still need to add .15oz of weight but I will do that on race day.

 

[Rocket car]

With that arrangement your com is probably 1"-1 1/2" by the time you add the wheels paint, etc. Try ,if you can to move it back to 3/4" to 1" and you will pick up more speed and stay at the 7-9" of steer over 48" . COM Is also known as balance point from front to back, measured from the back axle to that point.

 

[GravityX]

COM is certainly way forward on that setup. You can likely remove some steer. That's a long wheelbase... what is it, 5 inches? That car shouldn't need a whole lot of steer in its current setup.

A viable option... cut out the section of wood behind the rearmost row of weight and move the forwardmost row of cubes to the rear, the long wheelbase should be able to handle that COM. Use 3M foil tape to hold in the cubes at the rear.

 

[Eric]

COM is just under 1 inch. Wheelbase is 5.5. I'm not sure I would want to cut it apart now, my boy would probably freak out. It was one of the three quickest cars at the test and tune. If taking some steering out would pick up a thousandth or two we will probably be ok. Then if he makes it to districts I could talk him into building a new car from the ground up.

 

[SuperFastRacing]

COM is just under 1 inch. Wheelbase is 5.5. I'm not sure I would want to cut it apart now, my boy would probably freak out. It was one of the three quickest cars at the test and tune. If taking some steering out would pick up a thousandth or two we will probably be ok. Then if he makes it to districts I could talk him into building a new car from the ground up.

I would do what Gravity X is telling you to do. To my understanding, more weight in the back will give you more horse power! You have a long wheel base with a lot of steer it should be fine. Make sure you are running tight wheel gaps and you shouldn't have a wobbler.

 

[SuperFastRacing]

BTW. One of the fastest is different from the fastest! In the end you should do what makes you comfortable. I would still cut that part out even if you don't put the weight back there and fill it with 1/4" balsa so you can remove it and see if you pick up speed if you get another chance to test. Also if you get another chance to test, go with Gravity X's set up and take enough steer out until it wobbles and then put it back in until it stops.

 

[Eric]

Thanks for the sound advice guys but we did not feel comfortable cutting the car apart and moving weights with so little time before the race. We did dial the steering back to 8 inches in 48 inches, we went into race day today not 100% sure how the car was going to react. My boy won his Den race and moved on to the pack championship race. The pack championship was the fastest car from the four dens. They made eight runs, two runs in each lane. He swept all eight race. The closest win was buy .001.
We will be building a new car for districts, I'm sure I will have lots of questions. The first one I have is, at districts they run on aluminum and wood tracks. Do we build a car suited for the lesser of the two tracks? Or is there even any difference between the two types of tracks?

 

[Rocket car]

There should be a big difference between the 2. Build for the wood track. The mission from this point is to make sure it does wiggle on either. Plus move that COM back and you will pick up more speed.

 

[jjackrash]

I have been testing on an aluminum best track. The race is tomorrow on a wood track. What do I need to do differently as a far as set up and tuning?

 

[Mojo Racing]

add an inch of steer

 

[jjackrash]

Shoot. Ok, thanks for the tip.

 

[jjackrash]

I appreciate the tip. We tuned the car with a little more turn and the boy went 12 of 12 and won every heat, including the pack finals.

 

[DerbyDad4Hire]

You need to get more weight back.

 

[Mojo Racing]

Congrats ! ! ! I had a boy over today, working on his car... it gets inspected on Tuesday night... he races Friday... Wood track (ughhhh)... Where I normally run 4 inches of steer for a cub aluminum track, I set this one up for 5 inches. And it still screams down my track... super stable... that is what I really look for. I was able to put the NDFW against the rail, and it straightens out great, pull the left rear all the way over... runs great... same with the right rear... it corrects and runs with no issues down the track... I am hoping Friday night is as good as today was. This boy was ecstatic !

 

[jjackrash]

I have been breaking down some slow mo videos. It is obvious from slo mo video that the second to the last joint in lane three was awful.

My buddies' boy had the second fastest times of the day in the first two races, but in the second race the second to the last joint knocked his DFW out of whack and he moved towards the back of the pack the last two races and was eliminated. My boys' car took a big bounce at the exact same place in one of his heats, but he had enough steer to correct almost immediately. It was really amazing to watch. Looking at video many cars got absolutely crushed by that joint in lane 3.

 

[Eric]

I have been breaking down some slow mo videos. It is obvious from slo mo video that the second to the last joint in lane three was awful.

My buddies' boy had the second fastest times of the day in the first two races, but in the second race the second to the last joint knocked his DFW out of whack and he moved towards the back of the pack the last two races and was eliminated. My boys' car took a big bounce at the exact same place in one of his heats, but he had enough steer to correct almost immediately. I was really amazing to watch. Looking at video many cars got absolutely crushed by that joint in lane 3.

This forum has a wealth of info, and if you ask the right questions they have been answered or will get answerd. But how do you know what your specific car is doing? Most wiggles and such you can see with your naked eye but a single bobble at a track joint, how soon the car is hitting the rail or wheels jumping off the track because of the starting gate slamming down can only be seen with video, at least with my eye sight. Lol

 

[Eric]

You need to get more weight back.

On a three wheeled car, do you want positive camber or negative camber on the DFW (axle hole drilled straight in with a bent axle). The new car will have the weight moved back farther. This car I was afraid of it breaking if I cut it that thin in the back. Now I know better. The 5.5 wheelbase ran straight as an arrow with 8 inches of steering and I would not be afraid to dial that back another 2 to 3 inches.

 

[jjackrash]

This forum has a wealth of info, and if you ask the right questions they have been answered or will get answerd. But how do you know what your specific car is doing? Most wiggles and such you can see with your naked eye but a single bobble at a track joint, how soon the car is hitting the rail or wheels jumping off the track because of the starting gate slamming down can only be seen with video, at least with my eye sight. Lol

Yes, you can sure learn a lot with slo mo and an accurate timer.