Three rows of 6 1/4th inch cubes behind the back axle

Has anyone used the standard slot of the back axle and installed 3 rows of tungsten cubes behind the axle? If so how does it do? I am knew to this and trying to figure out a few things without the aid of a track.
Thanks in advance.

 

It will get very wobbly going down the track. That is a lot of weight behind the axle, and it will make your dominant front wheel very light (your COG will be way back).

As a second note, try to drill your car instead of using the slot, if you are allowed. You will be a lot happier with the alignment.

 

It is very difficult to build a stable running car with 15-18 cubes of tungsten behind the rear axle.
If you use the existing axel slots, it will be even more difficult. Most cars will do well with up to 12 cubes of tungsten behind the rear axle. I would also suggest that those 12 cubes be placed as close to the rear axle as possible.

 

You can get fast without a track.
These guys that answered are the fastest in the nation, they know the stuff!

 

I have been experimenting with some tungsten "blocks" that are solid 1/4 inch thick that weigh about 65 grams. Do you folks think that the 2.3 oz is a bit much or should I stick to the 2.0 oz of cubes. I realize I am only dealing with .3 oz extra, but everything else in this game is so precise that I need to ask anyway.

I am a scout car guy looking for a little more push, but I find myself rolling a couple of blocks forward ahead of the axle to get my wheel weights right which might just be a zero net gain with a little less stability. Looking for guidance.

 

12 cubes behind the axle the rest in front. You are shooting for around 20 grams on the dominant front or you won’t be able to get a handle on it.
Then its wheel & axle prep.
If you concentrate on John’s prep videos you’ll be faster than 90% of the Scouts in the country. The other 10% watched the video too.

 

A 65 gram solid block is ok behind the rear axle. Much will depend on the quality of the track and the alignment of the car. You may need to run a bit more steer to get the car stable if something is a bit off.

 

My daughter and I ran into this issue; wish I had logged in to see this post. She stacked 18 1/4 tung behind rear axel and placed the rest of the weight at the nose of the car (in front of front axel) to get COG just about 1" in front of rear axle.

Man, did that thing wiggle! So now post-event we are trying breaking down what should have been done.
Base on the advice above, and some of the other forum posts, here are our questions if we were to attempt this again and do it better:

First current stats that we would used instead (based on the current car body, wheel/axels used)
Original axel slots needed to be used

0.6 oz = car (mostly ladder style used)
0.4 oz = wheels+ axle = 0.4oz
2.0 oz = 12 x 1/4 tung behind rear wheel axle (butted against the axel rather than the back edge of car)
total 3.0 oz leaving 2.0 oz to place.

Posted above was the suggestion of 20 grams (0.71 oz) on dominant front wheel.

Should we avoid placing this in front of the front axel or stay behind it? (we only went full front of axel to the nose of the car to get the 1" COG the first time 'round with a heavy 3 oz on the tail )

With 0.71 oz sitting on the DFW, what should we do with the rest of the weight?
Stack it front of car for max stability; ignoring 1" COG for something greater?
Stack it mid car achiving 1" COG?
Stack a little in front of rear axel, counter weighting rear of front axel until all weigh used and 1" COG?

 

It seems like you are over complicating it a little bit. If you’re building a ladder body, and cut out your weight pockets, I’d assume you have enough room for 4-5 rows of cubes right in front of your rear axle. For behind the rear axle, you want anywhere from 2.0-2,2oz. The rest should go in that 4-5 cub row fitting weight pocket in front if that makes sense. You will only actually need about 9-12 cubes or so in the pocket. This will get you enough weight on your DFW. 0.71 oz is a lot to me, I’d put more like 0.5-0.55 for a scout car on the DFW.

you shouldn’t put any weight on the front half of your car.

I don’t know how other racers do it, but I just don’t worry about COG. Never have and likely never will.

 

T-Bone Racing thanks
A little backstory: this was the 2nd year where one of my youngest "first year to pinewood" sibling's car dominated when it really wasn't supposed to.
For a 5-6 year old's car, I let them do as much as they can; sanding, painting, and gluing in weights. I cut the car, dremel out the weight pockets and place on the wheels and we tone it on the toning board together. Never have we wanted a 5-6 year old's car to appear like it was built completly by dad. It should do ok, but have room to learn how to make it do better for next year.
My older seasoned children, on the other hand, apply actual physics to their cars and pour alot of time into them. Understandably, our biggest issue is not having a track to test new design concepts on, only having to rely on race day to see what the cars are going to do. (That would solve a lot)
The results end up being that my older children's cars end up doing much more poorly than the 5 year old's car, and it has the appearance of, "it's because dad built it". This is the opposite from reality. The reality is that dad did the most basic weight placement for the 5 year olds, and spent hours with the older children tweaking their speed cars.

My oldest childe (16) applied her school physics, arguing that she wanted to treat the 1" COG as the fulcrum of a lever. If she maxed out 18 cubes behind the rear axel, she would only have to place 3-4 cubes to the very front of the car to achieve the balance, only having to sacrifice 0.6-0.8oz to gain an extra 1 oz of weight to the rear. I thought she was on to something. She spent many hours on the car. I honestly thought her car was going to blow away all of the competition. You can guess it did very poorly. The wiggles were horrible on her test runs on race day. She quickly tried ripping 2 cubes off the back and placing them in the front. It reduced some of the wiggles but not enough for race time.

I understand that the immediately response should be, "find out why the basic built car is doing better that the others". This is what I'm doing here.
Younger basic builds =
Usally not shaped for speed; car, rocket, & pickle shaped cars.
What we have left over for weight placement is divided up with how much can we put behind the rear axel and mid car to achieve a safe 1-1.5 COG.

While this works, we now what to figure out exactly why it works so it can be bettered on when we are trying to actually go for speed with the older children's cars.

So, when the above resposonses say that after placing X cubes behind the axel, put the rest in front, they don't mean "in front of the car", (like i thought they were saying) but rather, in front of the rear axel?
I really would like to help my daughter understand why her smart build didnt work.

 

Thanks all. I think I understand that I was way closer to doing it right when we were stacking the mid of the car to counter the weight in the rear, than what we did this year. What weight that can be placed back of the rear axle of a car is depend on if weight on DFW and COG is established, while placing the extra weight diectly in front of the rear axle; too little on DFW and COG = too much weight in the rear for that car. Too forward of COG is way less an issue than a COG too far back.

I was making it way to hard. thsanks again

 

What is the recommended wheel gap for the DFW?

 

Yes, in front of the rear axle, not the front axle.

 

This is hard to answer because of how slight this gap actually is. It really isn’t that complicated though. It should be a little looser than the rears, but not too loose. It should just have a slight little bit of play when you move the wheel between the axle head and body/washer. It really is more of a feel thing then something measuriable, at least for me.

Hope that helps!