Why weight on B4 / B4.1 ?

[Richard Lowe]

Tony Tony Tony

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

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]

Originally Posted by Richard Lowe

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]

Originally Posted by elvo

...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

[ben]

Originally Posted by Richard Lowe

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

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

[Richard Lowe]

Whatever

[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]

Originally Posted by SHY

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

Until recently.

[PaulRotheram]

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

[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]

Originally Posted by elvo

Until recently.

Meaning what AE-man?

[flipside]

Originally Posted by SHY

Meaning what AE-man?

Meaning untill the wheel color arguments kicked in :-)

[SHY]

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

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

[Lonestar]

Originally Posted by SHY

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

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

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]

Originally Posted by Lonestar

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]

Originally Posted by Lonestar

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??