Weight Distribution

[Crooked H]

I thought this would be another good subject to trade thoughts on. For some oddball reason or not, this seems to be one of those things people either don't think about or just prefer not to discuss. Please begin formulating some thoughts on this subject and post them when you get a chance. I will do the same; but right now I must retire to bed as the sandman was kind enough to remind me I have to go to work tomorrow. :rolleyes:

[Ghost]

god you must bag out early in CO.

As for the Weight distribution, I tried to set my 150mm chassis up with the weight as centered fore/aft and left/right as well as low in the chassis as possible for a good starting point.

I will have to rework the 140mm I picked up on ebay, but again I will go for centering all the 'adjustable' components to get it ready.

[No Limits]

Hey Crooked H I just designed a sway bar if you wanna check it out next practice. Let me know. I have to still try it at the track but I am pretty sure it works. I noticed a difference on tile. But we'll see. TIM

[Crooked H]

Congrats on the swaybar setup No Limits.

One point I would like to touch on within the weight distribution subject is the controversy over battery arrangement on a pan chassis. I have grown tired of the saddle packs suck, they don't handle as well as center placement absurdity that keeps arising. A statement like that is a true testament to the inability of its speaker to tune a car properly. Whether your heaviest weight is placed within the center of the chassis or at its edges, one fact will remain constant; if the car is balanced, guess what? its balanced. I have found that a saddle setup with the electronics placed similar to the Team Epic chassis yields a vehicle that corners quite flatly, thus making full use of the contact patch of the tires. This is what can lead to traction rolls in this type of setup, not the chassis leaning over and catching the ground as many would have you believe. This can also be observed in many 10th scale touring cars as many have center, saddle, side, and anything possible battery mounts. And just as I observed in micros, the saddle pack equipped ones cornered relatively flat.
The other point of argument is that the way saddle packs transition their weight on the tires scrubs off speed. This amount of supposed speed loss is virtually nonexistent when the vehicle is properly balanced and if that virtually nominal amount of speed makes the difference between a victory or loss for you, you have some other issues that need to be worked out. Another point is the total comparison between a saddle pack equppied micro and similar battery configuration 10th and 12th scales. The only similarity between them is the end result which is flat cornering. Each type however makes use of different suspension setups to best tame the characteristics of a saddle pack. This holds true for the micro. No matter what pack configuration you use, you must tune it to handle properly.

To put that in layman terms, if one person has a well balanced saddle pack configuration and goes against someone with a center mounted, not-so-balanced configuration, as long as he is a decent driver he can expect victory.

[Crooked H]

Another point I would like to discuss is fore/aft weight distribution since stock chassis setups can also benefit from this as well. I am trying to theorize a basic rule of thumb for an allowable differential in fore/aft balance that will give fairly neutral handling and doesn't require corner weighting the car in order to achieve it. Also if you guys have some ideas on how some possible setups that could achieve this would look, sketch them up or post pictures of them.

[Mondo]

Crooked H

Excellent reply and you made some extremely valid comments.

I have a Penguin LM Pan chassis.
I only use T.O. 7.2V and T.O. 6.0V packs (Saddle packs are a hassle to make)

The Penguin has a battery mounting plate. This has two positions, obviously for 140/150mm settings, but at 150mm, wheelbase I can move the battery holder back by an inch (22mm)
The T.O. batteries are mounted with velcro.
I can move the batteries by an inch without having to move the battery mounting plate. The wonders of velcro.

On Monday I raced on a carpet track. There were 9 Micros in the race.
The Penguin was set up all wrong, I had zero traction. I came bog last in Heat 1. All I did was slip and slide.
Into the pit and I realise my spare suspension plates are not in my toolbox.
So, I put the standard tires on (I had soft tires in Heat-1) and moved the battery as far back as it would go.
Heat-2 was a different story, I was up there with the front runners.
A huge improvement that I attribute to weight distribution.
I used the KoPropo 301 Micro RX which was mounted on the right side deck. The Novak SPY was on the upper deck.

I don't believe the RX has any affect on weight bias as it weighs something like 15 grammes (1/2 OZ?)
The SPY is a little heavier, but resides above the battery pack.

This is just one example of how weight distribution can work. It worked for me.

[duxrneet]

I recently measured the width of the tires front and rear, making this my little thought of the day. The area of the tires F/R is in a ratio of 40.3/59.7% So I would suspect that the most neutral handling (and the best acceleration without losing traction) would come from a weight distibution of the same ratio F/R.

[Crooked H]

Interesting find Dux. I took note of some of the handling characteristics of my old setup which biased slightly more weight to the rear and found that in a mod motored micro, this produced a micro that had dragster like acceleration and reminded me to slow down to take turns. I compared this with my current setup (which works well for stock motor classes or expert drivers) which is usually near a 51/49 front biased depending on the batteries used and how they are positioned. In my current setup, the car will turn on a dime even at speed and requires you to be mindful of your racing line as it is a point-shoot steering setup now. This branches off into my aerodynamics topic a bit, but I am hoping to master this sort of weight bias with aero tuning similar to what the Ford Rally Team achieved with the Focus WRC which has a 52/48 front biased setup when sitting still, but 50/50 at speed thanks to downforce. This allows the vehicle to be stable at speed and also late brake at carry more speed through the turns.

Here is a brief description of my setups:

Old Setup

ARM switched to Ratzas Chassis
GTP Steering with servo on the right
Receiver on the right, behind servo
ESC on the left mounted to the rear of the f/r centerline of the chassis
Batteries center mounted with velcro to adjust weight bias

New Setup

Ratzas switched back to ARM Chassis
Center mount servo (Team Epic Style)
Receiver mounted on right side near front
ESC mounted on left side near front
5 cell saddle pack mounted on both sides in rear with velcro. 3cells on left, 2 cells on right and can be adjusted to tune weight bias

[HO502cid]

Originally posted by Crooked H

New Setup

Ratzas switched back to ARM Chassis
Center mount servo (Team Epic Style)
Receiver mounted on right side near front
ESC mounted on left side near front
5 cell saddle pack mounted on both sides in rear with velcro. 3cells on left, 2 cells on right and can be adjusted to tune weight bias

Looks nice, wouldn't you benefit from having the set of three on the right side behind the Rx? The Rx weighs less then the ESC, I would assume. If you have an extra cell on the right side it may balance out the slightly higher weight of the ESC.... just a thought.

[Crooked H]

For some oddball reason, the side with the reciever was actually heavier. This could be the effect of the speed control (a Futaba MC330r with 20 gauge wire) sitting more inboard towards the servo than the receiver (Futaba R123F) which still resides clear on the other side of the belt.

[HO502cid]

Originally posted by Crooked H
For some oddball reason, the side with the reciever was actually heavier. This could be the effect of the speed control (a Futaba MC330r with 20 gauge wire) sitting more inboard towards the servo than the receiver (Futaba R123F) which still resides clear on the other side of the belt.

Very odd indeed.

[TFRMicro]

Crooked H, what tools do you use to check the car to see if its balance or not...?

This is a very interesting topic...:cool:

[Dan Sparbel]

The oval racers at the local track - including me - use 4 postage scales (one for each wheel). I'm sure the same could be done with a micro... or you could just tie a string to the exact middle of the chassis and hang it upside down or somethin...

[ScottMcLeod]

On a stock micro, without any electronics...

So just a motor and a battery pack, where is the weight distributed, and how much?

(just so I can figgure out how to get my stock all balanced up.)

[duxrneet]

Depends on the car. You'll have to try/figure it out!

[Crooked H]

TFR- I use the makeshift, get a cylindrical shaped object (long screwdrivers work well), and place it under the center of gravity and lift the car up method. This isn't a very accurate way of doing it, but it gets you in the ballpark especially if the car is grossly unbalanced. The postage scale method described by Dan is very good but I haven't been able to get access to one to balance the micro.

Scott- On a stock micro with only a battery pack and motor, if the pack is mounted in the stock configuration, then the weight is biased toward the rear, though I'm not sure of the ratio. It can be balanced out depending on the weight of the electronics that you later place on the chassis as well as how you place them on the chassis. I've seen people mount the receiver and ESC on the top deck with velcro so they could move them fore/aft to tune their handling.

[TFRMicro]

Great, thanks...

[GT Eye]

So what im assuming after reading is that weight distribution is a lot more important than weight itself.
On this board, people seem to be obsessed with shaving off weight- is any of that consequential?

[Crooked H]

Yes and no. Under most circumstances, a micro with equal power to others that weighs less will be faster, which is why many of the rules for larger scales have a minimum weight requirement. The problem arises in some cases where the car may be too light. The reason it can be a problem are if you get into contact with another vehicle on the track, the lighter car is going for a little flight. Also in the case of mod-motored micros, extremely light weight can cause problems with traction and high speed handling although some of this can be alleviated with a high-downforce body. You have to find a happy medium between weight reduction and your driving style.

No matter the weight of the car, it is a good practice to balance the car to the best of your abilities. I have seen heavy cars win races because they were balanced and the driver was able to concentrate on driving rather than having to fight to keep the car on the racing line.

[jblackmore]

I guess most of you guys are racing on tarmac, but for carpet running I find sanding the tyres is the best tuning aid to get the car balanced, I typically sand the rears at the start of every meeting, and leave the fronts alone, and if I get corner entry understeer, I sand the inside edges only of the fronts.

A balanced car is one which can be driven on the throttle, lifting off will tuck into the corner, and accelerating will straighten out into understeer - this is what you should be aiming for.

Often a balanced car will have unequal weight distribution, so don't think that balancing your car with a ruler and straight edge is going to give you balanced handling - its trial and error that counts, and whatever works for your car on your track with you driving will be best.

[Crooked H]

Originally posted by jblackmore
I guess most of you guys are racing on tarmac, but for carpet running I find sanding the tyres is the best tuning aid to get the car balanced, I typically sand the rears at the start of every meeting, and leave the fronts alone, and if I get corner entry understeer, I sand the inside edges only of the fronts.

A balanced car is one which can be driven on the throttle, lifting off will tuck into the corner, and accelerating will straighten out into understeer - this is what you should be aiming for.

Often a balanced car will have unequal weight distribution, so don't think that balancing your car with a ruler and straight edge is going to give you balanced handling - its trial and error that counts, and whatever works for your car on your track with you driving will be best.



Actually I do race on carpet. What you are describing has very little to do with weight balancing in a car. What your are talking about is tuning the handling by virtue of tire traction, which much like weight distribution and aerodynamics, is merely a single brick in the wall of total car tuning.

As far as your statement, " Often a balanced car will have unequal weight distribution" , what we are describing here is an actual weight balanced car which makes tuning all the the other factors of handling much easier. I feel you may have misinterpreted this topic and be describing a car with balanced handling which is a different view from weight balancing, with the latter being a step toward achieving the first one.
:)

Two notes of importance here:
-a weight balanced car is easier to tune in order to achieve balanced handling
-no amount of tuning can completely compensate for bad driving:D

[jblackmore]

CrookedH, I understand the thread was about weight distribution, I was just trying to point out that you don't need a 50/50 weight distribution in both axis to have a car that handles well on carpet.

If your running std chassis and radio gear, there is not a lot of room for moving weight around anyway, so you are going to be stuck with about 40/60 f/r anyhows.

You should be able to get a car to handle by tuning tyre grip, springs and driving style even with an uneven weight distribution.

As always, a better driver will always beat a better car, so practice time is probably more useful than throwing a lot of $$ on corner scales for micros :-)

[GT Eye]

How do you calculate your F/R weight ratio anyways?

[Mondo]

Originally posted by jblackmore
As always, a better driver will always beat a better car, so practice time is probably more useful than throwing a lot of $$ on corner scales for micros :-)

And that is the Gospel truth!

[Crooked H]

Yes, but a better driver with a better car obliterates his competition mercilessly. :D

GT Eye- balance the car in the area of the chassis halfway between the front and rear tires. A long screwdriver is very useful for this.

[Apex]

What about stock micro suspension rates? Someone advised me to take out the rear spring for better handling. on the contrary, the car handled awfull, bouncing, wheel spinning, and rolling all over the track. I put 5 O-rings for the body posts/wings, etc.. on my rear suspension shaft, and the car now handles VERY well. I have much more responsive control when my car has to deal with an ubrupt collision with another, and it's much faster around corners, since the rear end is not bouncing.

has anyone played with their rear spring settings, and had the same experience as I?

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[RTolle]

I think that your weight distribution is important however not in the way that you describe. In every other form of r/c that I've seen you want weight evenly distributed from left to right, except in oval, and not front to rear (oval being a special case because you only need to turn in one direction). If you did want it evenly distributed front to rear why do cars like the losi XXX-S and associated TC3 have adjustable battery positions from front to rear? The reason is that your front to rear weight distribution will either increase or decrease traction on the front or rear depending on the spacing of the battery. Also not all cars have an evenly distributed wieght front to rear such as a pan car in which the front is vastly lighter than the rear. If the left to right balence is correct the car will handle in the same manner on both left and right turns thus making a car more predictable and easier to drive.

[Crooked H]

Funny that you mention the 10th scale TC's. As you notice their battery slots only allow so much in the way of redistributing the weight front-rear. Why? To keep a suitable proprtion of front-rear balance that allows the chassis to be tuned not only to track setups and conditions, but also to the user's driving style and preferences. As far as pan cars go, ever notice why they are so tempermental about rear traction. Too much rear weight. I recently did a comparison of 12th scale cars with some with a "normal" extremely tail heavy setup vs one with a front-rear balance that I would estimate at near 45/55. The end result, the "normal" tail heavy vehicle was dependent of traction compound to maintain control while the other setup felt very much as stable as a 10th scale TC even with the same compound tires minus any traction compound, thus supporting my stand of a proper handling vehicle needing a good ratio of front-rear balance.:D

[RTolle]

What you are saying is that a 1/12th scale car is reliant on traction compound b/c the balance is not correct. I'm not sure how you drive so I won't get into that. However, why then do the top racers in 1/12th scale all seem to use the standard wieght setup with compound? Also, if what you say is true then why do laws of physics disagree. It seems to me that the more wieght you have on the back of a car the more "stable" it becomes and or has less steering and can be described as a car that is "tight". A 1/12th scale may seem ustable to you however in my experiance they are extremely stable. I believe that you are confusing stability with an extreme amount of traction and a car that instantly reacts when you tell it to and does what you want it to. That is the reason a 1/12th scale is unforgiving to drive in the sense that when you, the driver, screws up the car has reacted before you can think to correct it but does not spin on the slightest input.

[Crooked H]

While in hindsight I realize I overlooked and overstated a few factors relevant to 12th scale cars, it is important to note that there are way more forces at play in tuning the handling in a pan car than a micro may ever witness including those darn T-plates for cars equipped with them (Carpet Knife uses suspended rear pod). Just remember this topic is about micros.:D

[freestyleracing]

what setup would be better. Saddle pack (2/3) or centered brick cells

they would be on a IPD chassis, but im just asking generally

[EVS-Micro]

Hey,

I would say 2/3 sattle back with 3 on each side. Doing that you can place all your electronics right down the middle between the two. Or still sandwhich your XXL or 230mc agasn't the servo. I would also think, the weight would be distributed nicely.

-CP

[freestyleracing]

that is actually what i have at this point, and im thinking about getting the brick cells to try out the 6 cells right down the middle. It might be better, it might be worse...any more comments would be great

[freestyleracing]

also...i noticed that the front end of the car seems to be higher than the back...could this be affecting my driving (which i must say, could DEFINATELY BE BETTER) and if so, should i just try putting washers on the front end to make a flat surface?

[EVS-Micro]

hey,

are you running with out the rear shock in the back. That may cause the rear deck to look lower than the front end. Not sure on that one tho, other wise putting washers will work great. Make sure not to go to low unless your a on a nice smooth surface. Since you will his every peice of rock in the world.

-CP

:) getting lonely only me and you are posting. :)

[freestyleracing]

haha, i know! there's no one else posting up stuff...especially the stuff on market, i need to get some stuff, but it takes too long for some peeps to get to their replying.

but yea, i was going to use washers, im sure that will definately help in my perf.

[microfuzz]

Hi,

instead of washers, why not try cutting a piece of the shock spring so the car comes closer to the ground in front ?

This would also give the car some droop, so the suspension acts in 2 directions... I think almost every other scale uses droop, which is very important, and this is the perfect way to do it.

I read that by cutting the spring, you'll get more traction rolls and that to prevent this a stabiliser needs to be used (please correct me if wrong).

I too have a front end that is higher, I atttribute it to the ratzas pan having some rear droop (chassis 'bends' a bit under the weight of the batts). (also some alloy knuckles have the bearing hole too low, so the car gets lifted a bit)

I want to try this asap, I'll keep you informed...

Greetings,
fuzz

[MystRacing]

Just a point of clarification on the saddle pack verses centerline battery placement.

First the side to side weight difference. Locating the batteries further toward the outside of the chassis will make the car less responsive to turning. The further the weight is from the centerline of the chassis the slower the car reacts to steering. A car with the weight down the centerline will react faster to steering input and be more responsive.

Second is the front to rear balance. A car with saddle packs will typically have more rear weight bias, because the batteries are typically one of the heavier components and are usually mounted toward the rear. In a micro depending on the electronics used the batteries can actually be one of the lighter components.

One arrangement isn't neccessarily better than the other for the following reasons.

In theory having the weight centered on the chassis instead of toward the outside, making the car more responsive is a good thing. In the real world though it's possible to make the car to responsive. If the car is too responsive it becomes very difficult to drive. If your car is already responsive enough for your driving skill, it's likely that going to a centerline arrangement will do nothing for you except make the car harder to drive.

As far as front to rear goes it's simply a matter of the front to rear traction balance. If the car is a little loose with the saddle pack arrangement and it's changed to a centerline arrangement the more forward wieght bias will make the loose condition worse. If it was pushing with the saddle packs the centerline arrangement would likely make the car handle better. One should note though that these handling changes are simply a matter of moving weight forward and back, and have nothing to do with the batteries being on the outside or center of the chassis. Also what I wrote assumes no changes in the mounting positions of other components.

[doobie4u]

i've tried both saddle and centered and i prefer centered. i found the centered arrangement to not only be more responsive, but also transition better between turns, like s-turns or switchbacks.

[MystRacing]

Weight bias:

Side to side; the weight on one side of the car should equal the weight on the other side. If it isn't the car will turn better one direction than the other. Assuming your not running an oval that is just a cut and dried fact. It's possible to make a valid argument about how much effect it has and the importance, but the fact will still remain that the side to side weight should be equal.

Front to Rear Bias; the front to rear weight isn't at all clearly defined. This weight bias is a function of many many factors. Primarily the amount of front and rear tire traction and the wheel rates. Wheel rates being a function of a-arm length, springs, and shock angle.

As an extreme example an offroad buggy has about 70% of it's weight on the rear tires, because the rear is much stiffer than the front it still handles well. The ratio of the rear wheel rates to the front wheel rates is about 60/40. It isn't 70/30 because the smaller front wheels require more weight to be effective in turning the vehicle with the larger rear tires.

A touring car typically has it's weight around 50/50 front to back. If you calculate the wheel rates (not the spring rates) they are approximately equal 50/50. Typically the front and rear tires are the same.

The bottom line is a car should be weight biased front to rear based on the relative stiffness of the front and rear suspension, and the relative traction of the front and rear tires. If the car has a stiffer rear end than front end, the vehicle will handle best with rear wight bias. If the front end is stiffer it should be forward weight biased. Of course on a micro we also need to take into account the thinner front tires, which should require a forward weight bias; however if the front tires are softer giving more traction it should have rear bias. The point is trying to figure it out on paper there are a lot of factors that effect it so it's extremely complicated.

Trial and error is the only way I know to get the proper front to rear bias and it's different for different drivers, track conditions, tires, chassis, t-plates, etc. etc. There isn't a magic number for micros, and it's almost impossible to calculate.

[MystRacing]

Now having said all of that. from a practicle standpoint. if you go to stiffer springs to reduce front traction, you could make the same adjustment by moving the weight toward the rear. The only difference is we are limited in the number of different springs we have; however, moving weight is basically an infinate adjustment.

I typically run extra weights in my cars, this includes my TC3, NTC3, Carpet Knife etc. for fine tuning. I have an EXO chassis and with my electronics layout I needed just under 1/2 an ounce of weight on the passenger side to get the side to side weight equal. This gives me 1/2 an ounce of weight that can be moved from the front to the rear for fine tuning.

IMO the extra weight isn't a problem because the other cars aren't pulling me out of the corner. It's true in theory that my car is slower than an identicle car without the extra weight but in the real world it doesn't make any noticable difference. I should also mention I'm running a big block.