Why weight on B4 / B4.1 ?

[Lonestar]

Hi guys

This is likely a dumb question... I am still struggling to understand why it matters so much to add ballast to the B4 / B4.1... Trishbits, ghea, AE's newly released ballast, 1:1 wheel balancing leads, everyone seems to be doing it.

One stupid Q - why? What can weight achieve that setup can't? Obviously mass repartition. But then why does every one add weight all over the car? And for those adding weight only at one end, what does this achieve handling-wise (not just static-scale-wise) that setup changes like shocks/springs/wheelbase can't do???

Thanks... Sorry, not much of an expert on car setup... I can drive it (almost) properly but can't setup a car to save my life

Paul

[RudeTony]

The long and short of it these cars just perform better with weight in the right places. They absorb bumps better, jump better and a heavier car is so much easier to drive. Not all are as gifted as some of our top UK drivers that have reactions quicker than cats - that sounds good eh.....it all seems to work and that is the bottom line in my opinion.......

[Lonestar]

Tony, thanks for sharing some knowledge...

My question was more about "why"... wheel rates are wheel rates... other than rotational inertia, I don't get it... why?

Paul

PS: your company is making lipo ballasts, right?

[Big G]

I don't think anyone in 1/10th uses wheel weights. my understanding was it was more of a 1/8th kinda thing than 10th...

why add weight is to do with the loosing of weight when we went to lipo power. adding more weight on the front will make the car handle different. also I found my B4 was underweight when using lipo so I had to add some to get through strutinering (I can't spell that word)

[MattADH]

A light can be faster but harder to drive. We use weight at the front to stop the car from lifting the front wheels and some at the back to aid rear traction - its like a tuning aid.

Some cars have not been designed around LiPo and the power they deliver/ lighter weight. I personally use additonal brass weights under the battery and servo to try and balance the B4's handling. I had to play around with this when we switched from NiMH to LiPo and I was not the only one who struggled with the change over. Its a case of personal preference as some of the faster drivers can run lighter than others as they have the skills to match.

I agree with what Tony says that for me, the additional weight makes the car easier to drive and therefore I am less likely to crash...

[RudeTony]

In any motorsport weight is a big issue. Where you place is changes the way the car reacts and so on. In buggies it can change the way it jumps, the way it stears and so on. The key is to get the weight as low as possible and as central as possible so on the wheels is not a good idea in 1/10th off road... Then by movement of the weight front and back you can balance a car the way that you feel comfortable. We can also all learn by the top drivers as well.......yes my company makes weights for various cars and we work very closely with the very best drivers of each manufacturer to make sure our weights are actually a performance extra rather than just weight. Testing is the best way in my opinion......sometimes what might be good for me may not be good for lets say you but using a good set up as a starting point, the majority of the time it's great for many.......hope this helps

[Rocking Donkey]

I think the wheel balancing weights being referred to are the 5g and 10g self adhesive weights used to balance full sized car wheels which are commonly used to add balast to out 1:10 cars.

I think part of the reason for adding wieght to a rear mounted motor 2WD is that the brushless motors are significantly heavier than brushed and LiPo's lighter than NiMH, the prevelent form of propulsion when the cars were developed. Brushless/LiPo also provide more torque that NiMH/Brushed. If you don't add any weight then these effects are going to combine and your car will want to wheely all over the place.

I've been thinking about trying brushed motors agian in 2WD and running a little lighter as I like the nimbleness when changing directions and through sweepers.

Ben

[Lonestar]

Originally Posted by Big G

I don't think anyone in 1/10th uses wheel weights.

now this is the one comment I didn't expect anyone to post... Have a read at the question again


Sidenote : people do balance their wheels in 10th scale, believe it or not but that's another discussion

Paul

[RudeTony]

Some people do balance their wheels in 1/10th -Simon Reeves always does - I am sure if he sees the post he will verify - I don't myself

[Reevsey]

As Tony has mentioned i do balance my wheels, some think i am mad but i do think there is a benefit to the feel of the car and you will have a smoother transmition that will last alot longer as it will not wear as fast.

You would not drive your full scale car with unbalanced wheels

[Lonestar]

Sorry guys had to take off unexpectedly yesterday as I had only partly read thru the thread.

Thanks for the answers.

Just to be clear - this is NOT a discussion about wheel balancing. What I wrote above is that people use a variety of weight "shapes" to add to their cars... whether it's the fancy ones (trishbits, rudebits, ghea, AE's newly released 17g one) or cruder ones (adhesive leads initially designed for 1:1, ie full scale cars, wheel balancing).

I understand adding weight to the cars on one end to change weight bias. What I don't get is people adding weight around the CG, or all around the car, unless of course it's to pass tech inspection.

If one adds weight around the CG, this is roughly equivalent to going to softer springs/hydraulics.

Compensating for nimh transition to lipo makes sense though.

I can understand somehow about adding weight evenly but further away from the CG, as this increases rotational inertia and slows down the car's overall reactions, which can make it easier to drive... I think it also means than when the car loses grip on one end and is gone, more energy will need to be dissipated until it can regain grip, basically it's easier to steer a speedboat back on trajectory than a petrol tanker...

Ok - I guess I'll have to try it myself in the end. It was my impression that a lot of people add weight without being really sure why. I have some self adhesive leads at home... time to balance my whe... er, sorry, to weigh the car a bit and see what happens

Paul

[RudeTony]

Your points are sort of valid but I will put to you this scenario and you will understand that it's the actual weight that matters - where you put it is how the car reacts but it's the actual weight makes the difference. Of course where we put the weight is important but remember that sometimes we are sort of limited and rely on the companies you mentioned to work with top drivers and manufacture parts that are in the rigt places.

You have a bump in a middle of a straight !!!
Your car is travelling at 35mph with no weight, in fact it's well under weight just for this experiment.....
It will hit that bump and fly in the air because it's light. It just won't matter how your suspension, oils or anything else is set up - it will fly because it's too light.....
Now same scenario but with a real real heavy car.
The heavy car just won't fly, it's too heavy, it will go over the bump with no issue.
That is why weight works.

Saying all that, like Matt stated, the top drivers will try and run the cars as light as possible, we all try to, but weight has to be added as these cars are off road cars and they jump, they bump and so on. If it was touring cars you points would be so much more valid but in off road the weight is actually a must.

Hope this has helped a little more for you

[Mr. Pink]

Some advantages with adding weight that I could think of.

*The unsprung mass(suspension/wheels) relative to the sprung mass is lowered.

*Tyre to road friction is most often not directly proportional to tyre load. (Fy= μ*mg) μ is actually dependant on the load of the tyre. Adding weight adds load to the tyre and depending on the tyre characteristics it could produce more (or less) friction so that the car can corner faster.

[Lonestar]

Originally Posted by Mr. Pink

Some advantages with adding weight that I could think of.

*The unsprung mass(suspension/wheels) relative to the sprung mass is lowered.

yes - didn't think about that one. should help suspension do its work properly indeed. makes sense

Originally Posted by Mr. Pink

*Tyre to road friction is most often not directly proportional to tyre load. (Fy= μ*mg) μ is actually dependant on the load of the tyre. Adding weight adds load to the tyre and depending on the tyre characteristics it could produce more (or less) friction so that the car can corner faster.

fair point too - on dirt (not valid on asphalt) mu is a monotonic function of load, but then again one has to find a tradeoff between grip and inertia...

Thanks for your comments

Paul

[SHY]

Originally Posted by RudeTony

Your points are sort of valid but I will put to you this scenario and you will understand that it's the actual weight that matters - where you put it is how the car reacts but it's the actual weight makes the difference. Of course where we put the weight is important but remember that sometimes we are sort of limited and rely on the companies you mentioned to work with top drivers and manufacture parts that are in the rigt places.

You have a bump in a middle of a straight !!!
Your car is travelling at 35mph with no weight, in fact it's well under weight just for this experiment.....
It will hit that bump and fly in the air because it's light. It just won't matter how your suspension, oils or anything else is set up - it will fly because it's too light.....
Now same scenario but with a real real heavy car.
The heavy car just won't fly, it's too heavy, it will go over the bump with no issue.
That is why weight works.

Saying all that, like Matt stated, the top drivers will try and run the cars as light as possible, we all try to, but weight has to be added as these cars are off road cars and they jump, they bump and so on. If it was touring cars you points would be so much more valid but in off road the weight is actually a must.

Hope this has helped a little more for you

Very well put Tony!!!

I think I finally got it!

[Lonestar]

Originally Posted by RudeTony

You have a bump in a middle of a straight !!!
Your car is travelling at 35mph with no weight, in fact it's well under weight just for this experiment.....
It will hit that bump and fly in the air because it's light. It just won't matter how your suspension, oils or anything else is set up - it will fly because it's too light.....
Now same scenario but with a real real heavy car.
The heavy car just won't fly, it's too heavy, it will go over the bump with no issue.
That is why weight works.

I can see where you're coming from but I have to disagree with this one... different (lighter overall for the situation you are describing) dampening/springs will provide the same result without resorting to adding weight... Maybe it's easier to add weight than chase the right dampening/pack/spring combination though...

This is an interesting discussion - please keep'em coming.

Paul

[RudeTony]

Originally Posted by Lonestar

I can see where you're coming from but I have to disagree with this one... different (lighter overall for the situation you are describing) dampening/springs will provide the same result without resorting to adding weight... Maybe it's easier to add weight than chase the right dampening/pack/spring combination though...

This is an interesting discussion - please keep'em coming.

Paul

Paul, I'm smilling as we have all thought the same way as you and yes I sort of agree that it's finding the right set up that SHOULD make it work BUT BUT we are talking the best drivers in the UK/Europe and even the World have tried all this and weight is weight no matter what you do.
I believe it's something to do with the speed these cars are travelling these days. They are getting too fast for the scale and hence weight is the way to go - It's the future.
Finally I will leave you with another thought.
If with weight a driver can lap quicker than without the weight, why why would he chase the set up for less weight. Why when he can win will he do that. We can run 15 mins with Lipos and have so much power we put slower mtors in. Why ? Enjoyed the discusion but just put the weight in your car and enjoy racing.
If you do find that magic set up though there would be plenty of people would love to have it.
I am smilling while typing so thats good i suppose!!!!

[Patriiick]

Drivers adding weight rely before all on being able to refer to existing setups and being able to use them over and over without the fuss and make them easily transferrable over lipo use

Adding weight overall just for the sake of sheer weight makes little dynamic sense and ideally, a light car is optimal for any dynamics.

The "pro heavy car" analogy of the car being more stable over bumps just by changing 2-3pc of its total weight seems.. far fetched.

I agree with Mr Lonestar that it is not dynamically efficient overall.

More generally, when i see the insane discussions about weight addons at races, at the local level, the importance given to adding weight is clearly vastly overrated .. at least versus proper driving, damping, tyre inserts etc...

[SHY]

Keep in mind that on a fairly flat and high traction track even an 1:10 OR car will be faster if lighter. We're then more or less racing "onroad" with some jumps. For 2WD on astro I actually tried before LiPo was allowed to use 4 cells and a 3,5 turn - the improvement was remarkable!

It's a totally different matter on a bumpy, rutted track, with low traction...

I'm a very experienced 1:8 TR driver, and there's never any doubt that lighter is faster! BUT - when it's raining and very slippery, then a heavier car actually has an advantage. Simply more grip!

We're never overpowered in dry conditions, and the corner speed is so high that less mass always is faster. But in the wet you're overpowered and need to "sneak around" the track.

There used to be a swedish 1:8 TR car back in the 70/80s called "Viking". It never really did well in dry races, but very often won in the wet. And that simply because it was very heavy! (I don't think they really knew why back then)

[RudeTony]

Lads lads lads - The stop watch NEVER lies and that is what we measure with......