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 :cry:

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]

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 :lol::lol::lol:


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

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 :thumbsup:

[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]

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 :)

*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]

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! :thumbsup::lol::lol::lol:

[Lonestar]

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]

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......

[Lonestar]

Shy,

this is an interesting perspective... on low-grip tracks, more weight generates more grip - but is the incremental grip overproportional vs. the incremental weight, or is the better handling mostly coming from the car's reactions being slowed down and then becoming easier to drive overall? My understanding of tire adhesion is that more weight means more grip, but not enough to compensate for the extra inertia... hope I don't confuse you more with this :)

I really like the sprung vs. unsprung mass perspective too... I didn't think about that one initially... good stuff...


Anyone without any commercial interest wanting to add to the "technical" part of the discussion? ;)

Paul

[Mr. Pink]

If you can add mass close to the centre of gravity you will not increase the inertia as much as if the mass was added further away. A normal 2wd byggy with rear motor will have quite high yaw and pitch inertia and very low roll inertia. But a X6 will have lower yaw and pitch inertia and a higher roll inertia, (battery placed from side to side).

Another benefit could also be that it also lowers the centre of gravity if the CG is originally positioned higher than the weight added.

[Patriiick]

The price ratio of such parts vs gains still is not me convinced...
You are still adding mass regardless and acting on 2% pc of the total car mass. It does have an impact i am sure, notable one you bet, must-have for the future.. not so sure.

I m not talking about adding 15grms under the bulkhead to midly compensate for lipo weight..,
but people are adding under pack weights, on servo, behind bulkhead, even on motor.. this is getting totally silly !!

2 years from now, i d be happy to bet that noone will add weights anymore to such extremes as today. it s like charging packs in ice, running the stiffest chassis possible, progressive springs, super long shocks in front..
It all faded out at some point.

[The Pookster]

Anyone without any commercial interest wanting to add to the "technical" part of the discussion? ;)

Paul

Interesting thread as I've been pondering this after returning to the RC world after stopping in 1996.

Basic science says the lighter car will be faster. In all forms of motorsport there is a minimum weight, and teams spend a fortune lightening their cars to get to the weight limit. Reason being that more energy is required to move the greater mass, in any direction, and on top of this are inertial effects which increase the energy required to accelerate the mass, or to put this simply for the mass to change from one moving state to another.

In practice it is not so simple as the car has to contend with bumps and make use of the grip available from the tyres.

In a tractive and braking sense the tyre's grip is primarily controlled by the mass it's carrying, so a heavier car will have more traction, or a more rear weight biased car the same. So in a low grip scenario the extra energy needed to accelerate the higher mass could be much less significant than the improvement in available traction.

In a cornering sense the tyre's grip is not a simple function of mass, infact carrying more mass could reduce it's capacity depending on it's properties. This is very long and complicated to explain but F=muR does not apply simply because the tyre is rolling and flexible. In a 1/10th sense different foam inserts will produce different cornering properties (as different tyres pressures do on the big stuff). A heavier car will need bigger/stiffer inserts to allow the tyre to produce more cornering force and these same inserts could then reduce cornering force on the lighter car. This is also the reason why high unsprung mass on a light car could not be desirable.

As for the bumps well whether the car behaves itself or not is a function of mass, unsprung and sprung, spring rates, mass distribution, damping properties (at different damper speeds) and tyres. Mass is only part of it.

1/10th damper technology is archaic and this means that it is impossible to seperate the performance between large bumps at high speeds, or rough ground, or handling and so on. It may be that a heavier car has a larger window of performance and the dampers are better at dealing with the variety of what's thrown at them.

My observation is that weight gets put on regardless at the moment but as the sport moves forward those that can find a way of making the set-up work with a lighter car are going to be faster, just basic physics.

[Richard Lowe]

I don't know if this apply's to anyone else but personally there are only 3 reason's I add weight to a car...

1 - Add weight at either end to change the weight distribution and balance of the car.
2 - To keep the front end of a 2wd down.
3 - To get up to the weight limit (:p)

I always prefer my cars to be lighter and need less motor for adequate straight line performance, making them like a brick and then going for the brute force method of adding more power seems a bit silly to me. It takes more effort to get the thing moving and change direction, all the electrics get hotter, tyre wear (and wear and tear in general) is worse. A lighter car will recover from bumps more quickly too as there's less weight to stop moving, also in my experience a lighter car is no less stable through bumps if your shocks are right...

When I was running the B4 the only weight I had in it was the Trish front bulkhead (40g) to keep the front on the ground, move the weight forward a bit and get up to the weight limit. And the squat block (28g), to get up the the limit and balance the bulkhead which moved the weight a little too far forward, it was under 1500g...

[PTRU]

one of the reasons I add weight to the car is to lower the C of G simples

this makes the car handle better all round.

plus a tuning aid.

[The Pookster]

Stuff

This makes sense to me.

Interestingly my B4.1 is so much better on the bumps I'm going to straight away start running it under 1500 grams. For whatever reason, whether it's the new shock angles or the new shocks, it has much less friction than the old one as well as more travel. Feels softer on the bench but just glides around the track. And being rear motor traction shouldn't ever be a problem.

It needed 40 grams just to get it legal so plenty of scope to play with weight distribution.

[RudeTony]

I am shocked at some of your comments lads.
You are actually saying that the likes of Ellis Stafford, Lee Martin and so on don't know what they are doing and week after week they win major meetings.....these are some of the best drivers in Europe!!!
Matt Benfield's B4.1 had weight in it at the last national and he finished 2nd only to Kev Lee in the last leg of the A and his car looked brilliant.
How can you argue facts and facts.

I hear the theories and yes they are right in principle but no one can argue with Ellis running loads of weight in his car and has dominated the last three years. 3 years lads, not one event.......come on that is a difficult one for anyone to argue with.
Weight works - simples :D

[The Pookster]

As it's your business to sell weight to RC car owners then that's an obvious post.

Weight works at the moment, the key to moving the game on is to understand why and how to get the car to work without it.

[MRD]

Like Tony says, you can't argue with the results.

Sometimes I run at a very small local indoor track thats all slippy polished floor with no jumps and Ive been playing with the weights in my X6. So far Ive found that putting more weight in the front makes the car push into the bends rather than giving it more grip but exit grip seems better. Weight on the rear improves traction and grip out of the bends but makes the tail a bit loose mid corner and hampers acceleration. This makes weight a valuable tuning aid to get the best out of the cars setup. The first thing I alter is spings, then its weight, then I move onto shock positions and the rest.

When I ran my B4 I used sticky weights and never moved them but with the X6 Ive got the full brass kit so I can add or remove weights to suit the conditions :thumbsup:.

[Richard Lowe]

...advert...

Why don't Pidge/Ellis run their cars at 3kg Tony, they'd be even faster then!?

[Crash]

Well done guys this is one of the most interesting threads I've read in ages. Everyone has valid points and their own experiences to share. What gets me though harks back to the original question - why?

When I started racing in the early 90's we did everything we could to make our buggies lighter (including drilling a silly amount of holes in the chassis of my XX!) so we could maximise the performance of our motors and cells.
These two areas have developed at a staggering rate in our fine hobby, but has it simply shown that the cars themselves haven't kept up?!

We've gone full circle, first we make them lighter, now we make them heavy. Who's going to be the first top racer to win right on the weight limit again?!

[Mr. Pink]

My theory on this is that back in the days with brushed motors and nimh/nicd batteries both power and amount of energy stored to finish 5min of racing was the main concern to make the cars go faster. The solution then was that lighter was faster as it put less strain on the motor and batteries. Now with brushless, lipo and power beyond, the limit now is how to get that power more effective to the ground. And if the tyres will produce more relative frictional force with a higher tyre load then heavier is faster.

[SHY]

Now now, come on! I doubt Tony is becoming a millionaire selling his little brass weights! :D

Ellis has done extensive testing, below and above what he currently uses. So of course this tree doesen't grow into heaven!

When I earlier stated that in onroad a heavier car is faster in the wet, that is of course only to a certain extent. That's common reason! What the limit is will vary depending on conditions, but there will be a "sweet spot".

And yes, all your physical theories are "correct". But you're forgetting that RC racing simply cannot be compared to 1:1 racing. The speed, low weight and power is simply way way too extreme here!

Me and Elvo had a fantastic & VERY long discussion tread on myTSN (Serpent) many years ago. The topic was "fluid dynamics", more commonly known as aerodynamics. I learnt all about Bernoullis theorem, inverted aeroplane wings, diffusers, gurneys, vortexes and so on... which was so much fun & very interesting! But in the end the conclusion was: The speed relative to the scale is so high that more or less none of these principles apply! Firstly we don't have "drag penalty" as we're overpowered. Secondly it's just "pushing air" here and there, plus tons of turbulence! So it's very much down to experimenting!

Keep in mind that also insects don't have "aerofoil" wings. They're just simple & flat, like RC wings. They just showe air around! :lol: (fluid dynamics don't work in such a small scale, as the air molecules are always the same size)

(Yeah, yeah.. the point comes now...) :yawn:

The same is the truth for weight. Forget your schoolbooks! Go to the track and start testing - with laptimes! If you at a given track and the best setup you can come ut with - are faster with a very light car - nice! Go for it! But try also with more weight - at different places in your chassis!

I'll do whatever is faster! F*** theory! Books have been rewritten throughout history! :lol:

And look at F1! They're experimenting all the time! Motorsport is no "given science"! It's trials & errors & crazy stuff all the time! A given setup change may even have different results on different tracks! So TEST, TEST, TEST!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! :thumbsup:

That being said, we now see more and more tracks with astro turf. Which means high grip and a fairly flat surface. This caters for lighter cars. My guess is we will also see softer (yet durable) tire compounds in the future (maybe also lower profile). Again, easier to get a light car working well... In my crystal bowl I see OR getting closer to on-road...

[warped]

Weight is good because:

Adding weight low down lowers the cars centre of gravity = more stability + more corner speed + better acceleration out of corners.:thumbsup:

Adding weight improves the ratio of sprung to unsprung mass.

Adding weight stops you're car from doing wheelies.

When you hit a big bump the suspension always bottoms out so suspension settings are irrelevant , but a heavier car requires more energy to make it fly.

A heavy car has more inertia so will be less responsive and easier to drive, especially in bumpy conditions.

It's easier to get the correct weight distribution by adding weight than modifying the car.



Weight is bad because:

A heavy car needs more power to accelerate and uses more energy.

A heavy car has more inertia so will be less responsive and will wear the tyres faster.

A low centre of gravity can hurt straight line acceleration on a 2wd as there is less weight transfer to the rear. (Only applicable if the car won't wheely)

Heavy cars break more wishbones.

Lifting heavy objects can injure your back.

BRCA insurance does not cover cars above 20kg.

[flipside]

I'm gonna comment too :)

There is a very important thing that more weight does, and that is it makes the car easier to drive. Especially on bumpy astro tracks, and in the UK that's all they got in the national series. There's no use for the super fast laptime if you crash twice in 5 mins. Anyone who has done a national in the UK knows these guys have 2 times 3 minutes of practise before qualifying starts. So you better get the car safe and easy, as the tracks they run on are VERY difficult. Of course the top guys also have to be super fast but I bet that even they make a trade off between fast laptimes and a car that is still driveable.

Then there's always the personal feel you want for your car. Some people just don't like how a heavy car feels (like richard for example). Ellis does, but his driving style simply asks for heavier cars. I don't think Tom God runs his car at 1700-1800gr? And he won this year.

Hitting bumps can indeed be solved with changing pistons etc, but one thing you don't change: weight of your wheels+tyres. So going extremely heavy or extremely light will not be good as this messes up the ratio between chassis weight and wheel weight. Only way to test that is by trial and error.

Personally I also don't like super heavy cars, but I also never succeeded in running with very light cars. So I go for the medium solution (as with any setup change I make :D). Smooth high grip I will use around 1550-1600gr (2wd) and on lower grip, or bumpier astro, more like 1650 - 1670 max. Depending on grip level, weight will also be moved fwd or back.

As tony says, just try it for yourself, and if you get lost, do what the top guys do and start over again. Or even better, the subtop, as they will most likely have setups that suit the majority of the drivers. I've driven with some cars or seen people trying to drive cars from the top drivers, and usually they can't complete a single lap without crashing out twice in every corner :D

[SHY]

This is the best oOple discussion tread in 2010!!! :thumbsup:

[RudeTony]

Why don't Pidge/Ellis run their cars at 3kg Tony, they'd be even faster then!?

Richard Richard Richard !!
If you chose to run your car light then that's fine mate.
You are a top driver, I respect that and you have to do what is right for you and how it all feels for you.
I am simply saying for the majority (probably over 95%) a heavier (note heavier, not 3kg) car is easier to drive and this reduces errors and therefore the overall package is better and ultimately quicker.
In fact a heavier car under test after test conditions is quicker on lap times as well.
You can push the car more when heavier because like I said before it’s simply better over bumps and jumps.
This is Off-Road – not touring cars where I would agree lighter should be better!!
These are all facts from the best drivers in Europe and the club racer, under test conditions, by results, by Championships and every day racing.
Maybe in the future we will learn, if it’s there, that we can run lighter and lighter but at the moment there cannot be arguments that a slightly heavier car is faster.

Ellis runs a kit of some 310g of weight that he moves around to TUNE his car to the conditions.
Lee has various weights from 70g upwards for under Lipo and under Servo for TUNING his car.
Tom Cockerill recently realised running weight is an easier car and he is our 2010 Champion

I posted here to help Paul (Lonestar) not to get into arguments lads.
Everything I say has factual results and not hypothetical or theories or maybes, Facts!!

Finally to those that have commented on this being a commercial interest and I sort of resent that comment ...... those who know me also know I certainly don't need to sell brass, it's not my living, it's my hobby ...... I can't keep up as it is with orders all over the world and certainly didn't post here for that reason but I suppose some people have assumed that....... never mind eh!!!!

[MattADH]

Matt Benfield's B4.1 had weight in it at the last national and he finished 2nd only to Kev Lee in the last leg of the A and his car looked brilliant.

Not wanting to change the topic from the car in question but it was 4WD at Stotfolf that had the weight in it.

Back-to-back testing on high grip found the car to be more stable and less reactive to direction changes. It may not be the perfect answer to getting the car's handling to my liking but it works.

I dont do much racing outside of the Nationals and in the 4WD, this has really helped me without changing oils and pistons bu half weights, etc.

Just for the record, Mike and Grant Williams (who came up with the idea in the CAT) tune their 4WD using different lead plates under the chassis.

[RudeTony]

Not wanting to change the topic from the car in question but it was 4WD at Stotfolf that had the weight in it.

Back-to-back testing on high grip found the car to be more stable and less reactive to direction changes. It may not be the perfect answer to getting the car's handling to my liking but it works.

I dont do much racing outside of the Nationals and in the 4WD, this has really helped me without changing oils and pistons bu half weights, etc.

Just for the record, Mike and Grant Williams (who came up with the idea in the CAT) tune their 4WD using different lead plates under the chassis.

I apologise Matt - i just wated to say how good you drove :)
But your 2wd was good as well - what weight you running on that Matt?

[Richard Lowe]

Tony Tony Tony :lol:

I was only having a giggle with the above comment, 3kg would be a touch over the top :woot:

I've found in the case of the X6 all the weights are to move the weight around in the car, not to increase the running weight in general. The fact the car ends up heavy is just a side effect of it being a bit of a fatty, mine is almost 1700g without any weight in. I have around 100g in mine which I move about to change the balance, I wish I could try it lighter but the base car being so heavy means thats not possible :(

[elvo]

I wish I could try it lighter but the base car being so heavy means thats not possible :(

Say what? Mine, with the heaviest of the heavy lipos in it, is only 1550.

[elvo]

OK I'll bite as well.

The textbooks all say light is right, light should always be faster. But then again, all the textbooks are about on-road, rubber slick tyre-kind of friction, which tapers off as load increases. On asphalt, weight transfer is a bad thing. Weight is bad, period.

At the other end of the spectrum, there are Baja trucks, CORR trucks, sand rails,... Those folks all seem to concur that bigger and heavier is faster. If they were let loose, they'd all be building 5 tonne monsters with 2m wheels. The rules specifically constrain wheel size, and that keeps all the rest (hp, vehicle mass and dimensions) in check. note that these folks have 2 things in common with us: 1) dirt, and 2) they face rough terrain and obstacles which are bigger than the vehicle.

R/C-wise, we've all been busy testing with weights ever since LiPos arrived. The first thing I noticed was that a sheet of lead down low is much better than using heavy NiMH cells which put the weight high up. That's a no-brainer.
Then there's the light car. Around 1500g, close to the weight limit. Personally I've never been comfortable nor (consistently) fast with it. Motoring down and softening up the suspension a little does make it more driveable, but still,.... it always seems fragile and skatey to me. The tyres have a hard time keeping in touch with the ground. And having tyres on the ground is an advantage when racing. It's like what Doughty and Flipside have already posted: wheels have mass as well, and it seems you need a high enough sprung/unsprung mass ratio. Regardless of wheel color.
As a side note: over a year ago, there was a lot of talk about Team AE's "B4 light set-up". It seems to have dies a silent death....
A heavy car ( >1700g) does work. Off-road traction is something undocumented and unpredictable, but pushing spikes or pins into the ground is completely different from rubber adhesion. Off-road, more wieght = more grip. A heavy car is easy to drive, and easy to drive HARD. It's as if more mass is like a bigger stick you can attack the out-of-proportion obstables we call jumps with. The downside is that you need a lot of motor. Things heat up more, components wear out sooner.
The stopwatch tells me that the optimum lies somewhere around 1600g. It depends on the track a bit, on a difficult astro track with lots of bumps and jumps, I usually run around 1650g. Same for low grip dirt. I only run light (around 1550) indoors and on billiard-smooth astro. The thing to keep in mind with those figures is they're for a car that's not ridiculously over-powered. The more power you intend to lay down, the more weight you need to bring. And Tony can help you with that.

[MattADH]

Once again Elvo is the voice of reason!

[Richard Lowe]

...wheels have mass as well, and it seems you need a high enough sprung/unsprung mass ratio. Regardless of wheel color.
More support for the anti-yellow wheel argument? Does the colour used increase the mass of the wheel and make the sprung/unsprung ratio worse?!

There, I've scientifically proven yellow wheels are slower :woot:

[ben]

More support for the anti-yellow wheel argument? Does the colour used increase the mass of the wheel and make the sprung/unsprung ratio worse?!

There, I've scientifically proven yellow wheels are slower :woot:

Rich, you run spoked wheels. Your opinion isnt valid!

[Richard Lowe]

Whatever :p :D

[rich_cree]

not as bad as the 1/8 scale fellas, red or green spoked wheels are surprisingly common!!!

[elvo]

Well Rallycross does have a lot more mass to start with, plus, it varies throughout the run as the fuel load decreases. I imagine red and green spoked wheels being an attemp to to keep the unsprung/sprung mass ratio under control.

[elvo]

This is the best oOple discussion tread in 2010!!! :thumbsup:

Until recently.

[PaulRotheram]

I've missed threads like these! Enjoyable debate and not too out of hand :D

[Razer]

Puh, read through all of this. Many valid points, but I think that it's always a compromise, not a single receipe.

My car turns into a paper airplane on the jumps without weight. regardless of setup.

And a paper airplane ain't faster than a good, weighted buggy...

[Battle_axe]

I must say I run my car right on the weight limit and with moving the cells and motor by running little spurs like a 75 I have found that the car is somewhere close to right I run 35g in the front as 35 g is what is needed to get it up to weight and I put it in the front as thats where I have found it to work best it's all a matter of choice but lighter for me is faster as I can have less power making the car easier to drive with my on/off approach to the throttle the only exception to this is stotfold where before I blew a spedo the car was running at 1700g as it's so bumpy it was the quick solution to getting the car to work well there just my two Cents there.

[SHY]

Until recently.

Meaning what AE-man? :D

[flipside]

Meaning what AE-man? :D

Meaning untill the wheel color arguments kicked in :-)

[SHY]

LOL! You guys seriously need to drink more!!! :lol::lol::lol:

Btw which one of you was "Mr. Sideburns" first? Who is the original AKA The Real McCoy? :lol::lol::lol:

[Lonestar]

This is the best oOple discussion tread in 2010!!! :thumbsup:

I do have to admit that this flies miles above the usual rest, like "what ezrun combo motor shall I putt in my himoto" :thumbsup:

Ok - I learnt a lot and I'm beginning to get it

. What I seem to read is that there actually are two key drivers for using weight, scrutineering aside, that "traditional" (read suspension, wheelbase, whatever) can't achieve :
1- Overall, more inertia makes the car easier to drive and less prone to snapping violently, and even top dogs still rely on it to make their cars driveable sometimes
2- Strategically disposed weight helps achieve the desired weight distro, ie providing more mechanical front/rear grip without messing with the rest of the setup.

This winter I'll run my B4.1 (currently in the build) indoors on non-permanent mixed lino/carpet tracks, with spec HB Beam Pink tires (that's a US, blue-groove track tire), and monster jumps. Grip is scarce and extremely inconsistent from one track section to another. I guess I'll have to experiment with weight as more weight would help prevent the car from snapping but will be a PITA on the lino sections (zero, or close to zero, grip).

Re the B4's "light" setup that everyone talked about a few months back, isn't that exactly what the FT B4.1 now offers as stock?

Thanks,
Paul

[RudeTony]

1- Overall, more inertia makes the car easier to drive and less prone to snapping violently, and even top dogs still rely on it to make their cars driveable sometimes
2- Strategically disposed weight helps achieve the desired weight distro, ie providing more mechanical front/rear grip without messing with the rest of the setup.



It would of been a lot easier if you just took my word for it all Paul.
Weight works.
I will get you a light set up but not for outdoors unless its FLAT and I mean FLAT -0 in fact you may still need an under servo weight to keepo the front down :)

[Richard Lowe]

Re the B4's "light" setup that everyone talked about a few months back, isn't that exactly what the FT B4.1 now offers as stock?
Yes it is :)

[RudeTony]

Very very close to - minor changes like a no3 front piston instead of no2 and little things like that - the B4.1 was built to be as light as possible hence all up with no weight added is 1475 and like I previously said - with weight coming in at around 1640-60 depending on tracks - the right weigh eh Rich??

[Richard Lowe]

the right weigh eh Rich??
My 4wd's a lot lighter than that :lol:

[RudeTony]

My 4wd's a lot lighter than that :lol:

So is mine - the thread is B4-B4.1 mate :)

[Chris Doughty]

another possible reason, a heavier car will more easily overcome the stiction of the shock seals so the car may feel a lot less like a stiff skateboard and be more supple in the rough stuff

[dinkey]

hi just read this thread , i would love to know the weight in grams ibs etc of of other cars out there i run brushless with nmhs , but i am told lipos are getting heavier, that will push the price of scrap brass right down ??,when every body junks there ballast????????;)