Weight distribution test on CR2

[flipside]

Hi all!

I recently joined the atomic carbon team to drive the CR2, and have been testing a lot with the weight placement in the car.

I believe that weight distribution is a very important and dominant factor, which can greatly improve handling of any car.

When building the car, and bringing it up to around 1600gr of total weight by adding lead plates under the lipo's, the rear wheels have about 61-62% of the total weight on them. Compared to other cars this is very low, resulting in a lot of steering, but also a loss of rear grip.

When you start adding weight to the front also, the weight % on the rear can even drop to about 60%, which is really insane :-)

Many people also complain about the losi's front end rolling and nose diving too much in turns. Adding weight to the front will only aid in doing this. I also believe weight up front makes steering slower. Compared to a B4, the front end of the CR is already quite heavy out of the box (thick plastic parts!!).

So I have been testing the car without any weight up front, and then tried to remove weight from under the lipo's and putting it more backwards. The ideal solution to do this would be to make the anti squat block in brass. This is not easy to produce, so instead I made the carbon fibre plate that sits under the gearbox in steel. Also made it wider and didn't make the big hole in the middle.

Here is a picture of this weight plate installed in the car. The thing weighs about 70gr.


I also left about 90gr of lead under the lipo's, cut to 2/3rd of the size of the lipo's and moved it to the back (against the steel plate). That brings my car up to +-1650gr depending on which tyres that are mounted.

All this brings the rear weight % to around 64,5%. Ideally 65% is believed to be the perfect balance for a 2WD, so that's pretty close.

I have been testing with and without this plate, and the effect is huge. The car is much more stable in high speed turns, or when you have to turn in hard after the straight for example. It also keeps the nose flatter while turning. To me it makes the steering much more consistent throughout the turn. It also improves handling on low grip sections significantly.

Last weekend I have raced with this part at the petit RC race. Had a part made for Steven (teammate in belgium) and he also confirmed how well this worked for him. He made a solid C final in his last qualifier, which is very good out of 130 drivers... There were very slippery sections and also on these the effect was huge.

I hope to test it asap on outdoor dirt tracks too. I have read people are using exotic setups to get some rear end grip, I really believe that simply using a good weight balance will give the required rear end grip, while being able to use normal oil, piston and spring combinations.

Interested in hearing people's thoughts on this :-) Will keep you posted with any new findings or improvements!

wouter

[Gayo]

You've got to love oOple for that kind of threads! Very informative, thanks Wouter.
I totally agree with you, I felt also on my B4 and X-6 that adding weight to the front of a car makes steering response slower. You have more steering on-power though.

It would be good to know what kind of weight ratio and overall weight is achieved with the yet-to-come aluminium chassis.

So I'll be the first to ask it here : would you sell me one of those fantastic plates?

[Northy]

Couldn't agree more, it is something I tested roughly on Saturday night when I ran the car. Ran it weight wise as I had outdoors in round 1, then for round 2 took all but 5g out of the front bulkhead and fitted as much lead as I could around the motor. The difference was massive I went about half a lap faster and put me on the pace

I have yet to weigh mine, but again, was going to aim for 65/35 split

G

[SHY]

Originally Posted by Gayo

So I'll be the first to ask it here : would you sell me one of those fantastic plates?

LOL! Now you've become like me!!!

[OldTimer]

There is a rear brace in the works to replace the carbon fibre part with a brass version, but its early days yet, as soon as i have more info i will post here.

[Gayo]

Originally Posted by SHY

LOL! Now you've become like me!!!

Usually you add : "yo tengo dinero"
LOL

[ashleyb4]

How do you figure this out???

I got my digital scales put two wheels on it cancelled them out then got another stack of wheels so they where the same height as the ones of the scales used my spirit level to be sure. Then zero'd the scales and put the back of the car on the scales with the other stack of tyres under the front bulkhead the scales read 1115grams did the same for the front and it read 756grams.

How do i figure the percentage???? Am i doing it the right way????

A

[flipside]

Hey, if you have only one scale, do the following:

Make sure you can put the rear wheels onto the scales (my scale wasn't wide enough, so I had to put a bigger plate on top of it). Reset the scale to 0 with that new plate.

Then make something the same height as your scale+plate where you can put the front wheels on.

Weigh the complete car, for example it's 1620gr.

Then put the car with the rear wheels on the scales, front wheels on the other 'thing' you made.

Read the scales, for example 1050gr.

This means 1050gr out of your 1620 total sits on the rear wheels. Or 1050/1620=0,648148 or in % multiply by 100 so 64,8% of the weight is on the rear wheels.

Simple as that!

[flipside]

the car must be placed with its wheels on the scales and other surface, not with the bulkhead or any other part! And with everything fitted as you would race, including body etc...

[ashleyb4]

Ok might go give it another go with the plate idea

A

[ashleyb4]

Right Just tried it using some sheets of acrylic as a base and it works out at 63.7%

A

[flipside]

And where is all your weigth placed, how much is the cars total weight?

[ashleyb4]

Car weights around 1770 If i remember right and the rear weight was 1130..


Ive got 10 grams infront of the servo the rude bits weights each side of the servo 120 grams of lead under the cells 25 grams under the motor in the square 22 grams each side of the motor on the side pods. O and 10 grams on the rear shock tower..

A

[olefiloux]

Originally Posted by Gayo

Y

So I'll be the first to ask it here : would you sell me one of those fantastic plates?

héhé!! Gayo would say: would you sell me TWO of those fantastic plates!???

[Wacker 2]

Originally Posted by flipside

Hey, if you have only one scale, do the following:

Make sure you can put the rear wheels onto the scales (my scale wasn't wide enough, so I had to put a bigger plate on top of it). Reset the scale to 0 with that new plate.

Then make something the same height as your scale+plate where you can put the front wheels on.

Weigh the complete car, for example it's 1620gr.

Then put the car with the rear wheels on the scales, front wheels on the other 'thing' you made.

Read the scales, for example 1050gr.

This means 1050gr out of your 1620 total sits on the rear wheels. Or 1050/1620=0,648148 or in % multiply by 100 so 64,8% of the weight is on the rear wheels.

Simple as that!

You're only working out half of the figures!

If the car weighs 1620g... work out the rear weight as you've already done, then turn the car around so that you have the front wheels on the scales and weigh that. I guarantee the front and rear weight added together will total more than your total car weight of 1620g.

The reason for this is that you will have some of the middle weight (middle of the car, batteries & radio gear etc) applying weight to both the front and the rear wheels in a static position on a flat surface.

The way to calculate the ratio of weight on the front and the back wheels you need to calculate the total weight from adding the front weight and the back weight together (we know this will add up to more than the cars weight of 1620g) and use that figure to calculate the percentage of weight on the front wheels and on the back wheels!

Hope that makes sense?!

All is kinda redundant really as the weight is only really an issue with car handling when looking at weight transfer - either on or off power or in the corners. This will all be determined by 'where' the weight is, shock oil, springs, ride height front and back, wheel base etc.

If any of this helps, I'm glad to be of service!

Jon!

[flipside]

Well the difference isn't big, it matches pretty good over here. I don't understand why it wouldn't add up? I maybe get a 10gr difference adding the two compared to the total weight. I think it has more to do with inaccuracy of placing the car (when flipping around).

Recently I simply bought a second scale so the front and rear each have their scale. When I add these numbers, it is exactly the same as the total weight when putting the car on one scale only.

Of course the weight is different while driving, but this setup gives you a good idea for adding lead to your car. I presume you agree that it is different to place 150gr of weight on the front or on the back of your car...

And even if it's only theoretical in this static setup, I made that weight plate because I noticed the small rear weight % on the cr2, and now my car feels 100 times better :-)

Can't wait to test it on dirt tracks, but I'm 99% sure that the effect will be massive.

[Legacy555]

Why has no manufacturer released a car yet that is correctly balanced when using Lipo cells and meets the minimum weight limit?

[Northy]

Originally Posted by Legacy555

Why has no manufacturer released a car yet that is correctly balanced when using Lipo cells and meets the minimum weight limit?

Because I'm guessing it's not as easy as typing a question on a stupid internel forum and also people are still learning what is "correct"

G

[Legacy555]

Originally Posted by Northy

Because I'm guessing it's not as easy as typing a question on a stupid internel forum and also people are still learning what is "correct"

G

By people, do you mean the general racing layman? I was refering to manufacturers with design engineers and development drivers.

[OldTimer]

Originally Posted by Legacy555

Why has no manufacturer released a car yet that is correctly balanced when using Lipo cells and meets the minimum weight limit?

One of the major problems is what is correctly balanced for you will not be for another driver, so its very difficult to come up with something that suits everyone.

For example last year with the CR2, most people were adding weight to the middle and front of the car, ie brass front bulkheads, lead under the servo speedo, lipos etc. Were as the belgium guys (flipside and the other belgium's) are running very little if any weight at the front of the car and adding weight under the back half of the lipos and under the motor.