Learning to Crash

[Cafe']

Alight, all learning here. i am doing my first ladder chassis. And the thought never occurred to me until now beside finding balance. Is it better to have the weight as close to better as possible. In the pick below my son is using lead and that is where the lead needs to be placed for balance

 

[Crash Enburn]

In this case, your rear wheels are forward more than they should be. With the wheels forward, it lets you (tempts you to) put more weight behind them. And then, as you've seen, you end up moving the forward weight around so that the car isn't doing non-stop wheelies. With the rear wheels at 5/8" from the back of the car, you can't really get too much weight behind the axle (and still have a relatively thin car).

Were you to run this chassis, I'd tell you to cut the rear weight a little and move the balance to the other side of the rear axle.

Ideally, you want to have the weight as densely located as possible.

Other thoughts on this chassis:

• You can make the rear axle support narrower. 1/4" is all you need.
• The sides can be cut to 1/8" (this is how you see all our cars done — the 1/8" sides leaves 1.5" of space to put in weights, rows of six 1/4" cubes
• With the rears at 5/8", you get 1/2" of depth to add weight behind the axle .
  
• You don't need that many rungs.
• Don't expose that much of your axles. While there will probably be no problem, you've given up half the axle support/grip.
• Nice, clean openings.

 

[Cafe']

Thank you for your reply Crash Enburn...
I stretched the wheel base to 5.5 .......the exposed axles you see are actually just placed there for stance purpose. They in actuality 1/4 forward. In RR the length of the car can go up to 7.5 inches and max weight is 5.5oz. I am trying to take advantage of their rules with longer car and more weight. On our track the fastest car we've seen is 2.94.....With the 7.5 length and 5.5 weight restriction what wheel base would be advantageous?

 

[Crash Enburn]

Build it like a regular league-style car that is 7.5". Rear wheels 5/8" from the rear, two rows of cubes behind, the rest forward; perhaps with a slight favor to the DFW side. Wheelbase... Whatever you feel like, really. 4.5-5" would be typical. Longer is fine, but unless the track is rough, I'm not convinced that there's benefit.

With careful prep on the wheels and axles, you'll dominate.

 

[Crash Enburn]

Another thought. Usually, when we refer to the CoM on your car, it's as it relates to the rear axle. Since we all put our rear axles in the same spot, the CoM measurement has meaning that is easily pictured. Since you are using lead, which is less dense than tungsten, you're not going to be able to get the weight as densely located. Which frees up your rear axle location. As long as the balance point of the car is >1/2" from the rear axle (not gonna be wheelie-ing) and your weight is to the back, you're golden.

 

[Cafe']

Ok, after advice givenon chassis I trashed the last one and did this one
Chassis height: 3/8 ( thinking a little too thick)
Rear axle: 5/8
Wheel base: 5"
Overall: 7" (will stretch it out to 7.5")

 

[DerbyDad4Hire]

Thin it up and you should be good to go.

 

[Cafe']

Thin it up and you should be good to go.

Thank you sir...

 

[Cafe']

Been working on this to relax these past few days. my wife's sister passed away so this is been a relaxing time.... balsa fenders weren't too bad with the video from bulldog

 

[Cafe']

got more sanding in today....should I thin them out more?

 

[derbydentist]

Looking good! The body looks much lighter than mine. Are you adding something in the front middle of the car to be the same length as the front fenders. I don't know a whole lot about the electronic timers at the end of the track and how they are triggered when the car goes under it to record the time. Is it a beam that goes all the way across or a single beam that comes up and down? The only reason I bring this up is that if there is a single beam in the middle of the rail that is triggered and given your car design in the front with the fenders sticking out past the car then the fenders wouldn't trigger the stop sensor and wouldn't get triggered until the middle of the car passes which would result in a slower recorded time than if the middle of the car was the same length as the fenders. Also I think it would be better because the starting pin would then rest the car with the weight in the back higher up the track resulting in more potential energy and faster times. Otherwise there is no benefit to having a longer car if the weight isn't higher up the track at the start. Just some thoughts - again I don't really know how the sensors work at the end so take this with a grain of salt haha

 

[Cafe']

derb dentist: yes. I am filling the gap between the front fenders. but still debating on how I want to do it.

 

[derbydentist]

derb dentist: yes. I am filling the gap between the front fenders. but still debating on how I want to do it.

Nice- scratch everything I just said then haha- can't wait to see the final result!

 

[Crash Enburn]

In most races, having the fenders further forward than the nose would be illegal ("No part of the car can extend forward of the start pin [meaning the spot on the pin contacting your car]") Quickest and easiest fix would be to simply add a popsicle stick tongue to the car.

The way the timing lights work varies. Our church's track uses light sensors. With an incandescent light overhead, the sensor senses the car by the shadow of the car cutting the light. One sensor per lane.

 

[derbydentist]

Thanks crash for the info on the way the lights work. Now I just have to figure out how to get my car to throw a shadow in front of it haha

 

[Cafe']

Going on, I'm trying mod-podge as a sealer

Then using wicked createx paint but had the worst time painting because I didn't clean my airbrush last time. So I stopped for the night to clean them.

 

[Cafe']

Jacked the wife's Dremal vise To hold the car while I put some paint down....sssshhhhh, lol,,,,

 

[derbydentist]

Jacked the wife's Dremal vise To hold the car while I put some paint down....sssshhhhh, lol,,,,

Haha that's awesome! I've stolen some things from my wife too... Try my paint stand next time - derbyguys.com- I'm kinda partial to it but I really haven't seen a better way to do a nice full car paint job in one shot. I have a pic or two of it on the "my sons BB8 car" thread

 

[Cafe']

Haha that's awesome! I've stolen some things from my wife too... Try my paint stand next time - derbyguys.com- I'm kinda partial to it but I really haven't seen a better way to do a nice full car paint job in one shot. I have a pic or two of it on the "my sons BB8 car" thread

Ha ..... that's a great idea!

 

[derbydentist]

Ha ..... that's a great idea!

My dads idea- we've been using it for decades in my family!