Can of worms

[Battle_axe]

Right weight why run it form all my physics lessons and common sence i cannot see the point in people running weight in there car when running lipo i understand the need to bring the weight up to the min limmit but thats it surely all that needs to be done is put the weight needed (to bring it up to the limit) in places to restore the origanal weight distrbution and thats all. any people have other ideas? hope tony gets in on this too.

[Marvin]

It can make the car easier to drive. Added weight that has been placed low down can actually lower the centre of gravity, and aid grip. Also, on a bumpy track, or a loose track it can make the car less 'skittish' as it'll be affected by the ruts and bumps less than a lighter car.

[Chrislong]

Cos a heavier car is easier to drive consistently fast.

A light car is capable of being driven faster (within good track conditions and relatively smooth track), but not many can drive it to its limit at the speeds we reach as it will be harder to drive (and setup being nailed is more critical).

Think of it by scaling up our scale. The cars reach a scale speed of 300-400mph or thereabouts, reaching top speed in less than a second, and with a scale weight of 16-18kilos = hard to drive fast! (insane)

[Agt26]

Adding a little extra weight can help keep the car settled/planted on a rough track. It can also help with getting the balance of front and rear grip right.

(someone else could probably give a better explanation)

Andrew,

[Battle_axe]

i ran my 2wd last week on dirt with lipo and the car cornered allot quicker and i was much faster round the tighter sections of the track the only place i truely strugled was over the double double section of our track where i strugled to keep the nose down the car all up wth a 3800 lipo was 1370g i think if i put the lead in it to take it up to the limit in the front it sould drive ok? wrong or right?

[tymill]

I can imagine a few ways that increased mass in the car would help handling.

As mentioned earlier by Marvin, the centre of gravity can be manipulated and moved closer to the ground, which can help keep all four wheels more evenly loaded when under acceleration either laterally or forward/back. The forces acting on the car to accelerate it (friction between the wheels and the track) are on the ground, and the closer the c of g is to the ground, the less of a torque is induced to roll the car (either sideways or into a wheelie/endo).

Also, increased mass increases the inertia of the whole car, so it is more stable and "unwilling" to be accelerated in weird directions by bumps etc.

I suppose you can also manipulate the polar moment of inertia a bit - that is how "centred" the mass is in the car. If the polar moment is reduced, (mass in the middle) the car will change direction more easily than it would do if the mass was at the ends of the car. Think of how it's easier to spin a 500g mini-football than a 500g hula hoop...

Further, it improves the unsprung mass ratio so the suspension works better. That is the fraction of the car's mass that is not "suspended" by the suspension (e.g. wheels, tyres, and a fraction of the suspension parts) is lower. Think Hornet!

But hey, I'm certainly not a top-flite driver, but I've got a pretty good head for these general concepts. I'm totally willing to be corrected though!

Cheers,
Ty

[jhammond]

^That's a very good explanation!

Bravo.

[MRD]

A thumbs up to Tymill Hawking

[Battle_axe]

Originally Posted by tymill

I can imagine a few ways that increased mass in the car would help handling.

As mentioned earlier by Marvin, the centre of gravity can be manipulated and moved closer to the ground, which can help keep all four wheels more evenly loaded when under acceleration either laterally or forward/back. The forces acting on the car to accelerate it (friction between the wheels and the track) are on the ground, and the closer the c of g is to the ground, the less of a torque is induced to roll the car (either sideways or into a wheelie/endo).

Also, mass generally increases the inertia of the whole car, so it is more stable and "unwilling" to be accelerated in weird directions by bumps etc.

I suppose you can also manipulate the polar moment of inertia a bit - that is how "centred" the mass is in the car. If the polar moment is reduced, (mass in the middle) the car will change direction more easily than it would do if the mass was at the ends of the car. Think of how it's easier to spin a 500g mini-football than a 500g hula hoop...

Further, it improves the unsprung mass ratio so the suspension works better. That is the fraction of the car's mass that is not "suspended" by the suspension (e.g. wheels, tyres, and a fraction of the suspension parts) is lower. Think Hornet!

But hey, I'm certainly not a top-flite driver, but I've got a pretty good head for these general concepts. I'm totally willing to be corrected though!

Cheers,
Ty

this is all a verry good explanation and i agree with what you are saying in the end i cant argue with physics as for the foward drive this is surely something that can be corrected with differnt springs oils and as the car is now lighter running a softer car should be easyer. i am soo new to driving and racing these things but if people are adding lead beond and ontop of the weight with nimh then to be honest i cant see the improvment this can add to the car and i will save my money

[super__dan]

If it feels good do it!

[tymill]

Cheers dudes - looks like I've just been outed as being a science teacher!

And hey, for what it's worth I'll never have to worry about being underweight racing my gold tub RC10!

It's all good...
Ty

[Richard Lowe]

I've always liked running my cars light, but then I also generally prefer a car with a stiff chassis to a floppy one unlike most.

One of the biggest gains from moving to lipo (especially with 2wd) IMO is the ability to move the weight to the extremities of the chassis - as tymill already mentioned. It's much better to get up to weight with things like brass bulkhead/squat blocks which give you the calming effect through bumps without the car having to heave lots of lead about letting you keep straight line performance.