at our club we run a horrendous amount of weight in our non mag sclaey nascar category, but its the only way to make them run smooth at speed!

 

a scaley magnet can pull as much as 80g at track distance.... i.e. hold a car to the rail hanging upside down!!!!

This means you may need as much as 80g in weight to emulate the effect of a magnet!!!.. but 15-20g is enough in most cars.

however more weight = slower accelleration, longer braking distance, less top speed....

The faster you travel the more weight is required to regain the stability lost from disposing of the magnet ...

Its a balance

 

QUOTE (hankscorpio @ 22 Jan 2011, 18:24) <{POST_SNAPBACK}>a scaley magnet can pull as much as 80g at track distance.... i.e. hold a car to the rail hanging upside down!!!!

This means you may need as much as 80g in weight to emulate the effect of a magnet!!!.. but 15-20g is enough in most cars.

however more weight = slower accelleration, longer braking distance, less top speed....

The faster you travel the more weight is required to regain the stability lost from disposing of the magnet ...

Its a balance

So your saying I should put more weight in some of my cars?

This is the bit I most aware of. I once put 100 WT of dry cement into the boot of my 3Ltr Capri, just to keep the back stable. She handled better, but lost her get up and go. I ditched the cement.

 

For non-magnet racing adding weight is the last thing to do after issues like gear mesh, true wheels and tires and loose bearings have been delt with. Some cars may run well with no weights at all. Once you start to get better grip some cars will want to flip in the corners, rather than slide. I like to stick thin sheet lead to the bottom of the chassis, if there is enough clearence, to counteract that. I like to have 65% of the car's weight on the rear tires. I only add weight at the front of the car if it wants to lift on acceleration.

 

Also torquier motors like the SCX are less sensitive to weight. A Hornby Nascar is quite heavy already and adding weight really detracts from performance both acc- and dec-elerationof cars like these. Keep it to the minimum and experiment with different positions. Sidewinders often need a small amount of front weight because of the nose-lifting effect of weight and power being at the back.

 

In real world racing, it's all about the 'unsprung' weight. If you need to add weight, it should be below any suspension effect that a slot car may have to avoid pitching.

Jules

 

Don't we all know that in real world slot car racing weight distribution is all part of a well tuned chassis?

Of course weight distribution can be changed by removing weight as well as by adding it.

Adjusting how much weight is on the guide and how much on the front wheels can make quite a differance in some cars.

 

QUOTE (Gone Racin @ 22 Jan 2011, 21:51) <{POST_SNAPBACK}>Don't we all know that in real world slot car racing weight distribution is all part of a well tuned chassis?

Of course weight distribution can be changed by removing weight as well as by adding it.

Adjusting how much weight is on the guide and how much on the front wheels can make quite a differance in some cars.

This is what I'm trying to get at.
You may have a set weight for a car that suites a track. Take to another and by adding, removing or moving it around you may get better times.
I race my son on Plastic SS & SC track at home. they go well enough, but put them onto wood and a total different ball game. The need less weight adding to them, some taken off.
So getting the balance right could be the difference between winning on not. It's the same in the real world.

 

Car doesn´t be too heavy, more important is the weight distribution on the chassis. Light car is easier to handling.

 

Although it deals with specific issues on 'traditional' cars my article on weights and magnets below deals with these issues.

Have a read!!

Cheers

Andi

 

Thanks Andi, that should be a must read for anybody who is into getting a car sorted, just right.
I'm going to have anther read, then act.
Thanks again for pointing me (us) to it.

Andy

 

QUOTE (Pioneer @ 22 Jan 2011, 19:56) <{POST_SNAPBACK}>In real world racing, it's all about the 'unsprung' weight. If you need to add weight, it should be below any suspension effect that a slot car may have to avoid pitching.

Jules

Now that explains the diet youve been on Jules. Trying to improve the unsprung to sprung ratio

People seem to get hung up about *adding" weight. Its supposedly counter intuitive to speed. Use the stop watch as your final and only parameter. If the lap times drop then just smile when an "expert" tells you adding weight is a bad thing. There is a "science" to adding weight which is pretty basic.

cheers
rick1776

 

I used to add weight to pretty much all of my cars. After a while i found removing the weight did not adversely effect lap times. I've found a better way of getting a car to handle is to adjust the number of turns in the screws. In some cars this is not enough, and thus weight is then necessary, however seldom more than about 10g. My infamous 09 auslot proxy aston martin was one of the lightest cars in the field @85g approx, and a full 70g lighter than an almost identical car, so it for sure goes back to the handling aspect, and finding a nicely balanced car.

It really does depend on the driver and their experience also, the more practiced i have become, the less weight i tend to use, i find other ways around issues including set up and varied driving tactics.

 

Ahh yes the flying brick which weighed in at 148g. I remember it well, my car was in the lane next to it. My instructions to Trev who was racing my car in that lane was to avoid being on the outside of it during a corner. My 1/24th scale cars come in under that weight.

cheers
rick1776

 

I know I'm new to this whole slot car tuning thing and (shock horror) I run on plastic track. But why would a regular car need to weigh in over 100g? Maybe I'm being simplistic.

I try to buy identical pairs of cars whenever possible. One for myself and one for His Lordship. We have completely different methods of tuning cars. I try to do all the right things before adding any weight to a car. HL uses weight as his only tuning medium other than tyre change and true. My cars invariably come in between 5 and 20g lighter than his. And in all instances he has driven my cars and commented on their 'responsiveness'.

Most notable of all in this list of matched cars are a pair of Ninco Exiges and a pair of Scaley Ford GTs. Even with alloy wheels on the rear (original wheels split and required replacing) my Exige comes in at a good 12g lighter than his and is certainly faster, more responsive (could possibly be considered twitchy) and stays in slot better. On the Ford GTs mine has original plastic wheels where HL's has alloy rears. Mine weighs 15g less than his, has no weight added, is faster and more predictable.

I'm only beginning, but I can certainly see the benefits of getting everything right before reaching for weight.

The heaviest cars in my 'tuned' collection are a Carrera R8 (naked it weighs in at 105g) and the Pioneer Bullitt at about 92g. The Carrera is about to have a motor upgrade as it runs really well on a friend's big 1/24 track but is too big to run comfortably on my little one.

Embs

 

Hi Embs

You're right, weight is not the definitive answer to improving handling, it's just part of an array of options open to the tuner.

Once I have the car handling as well as I can, then I play about with weight. Sometimes this stabilises things and makes it more controllable under acceleration, but if you can keep it light, it puts less stress on the motor and other bits. Sometimes weight makes little difference. Horses for course really and you often find, as someone else said, that you need to alter the set-up when switching from one type of track to another (plastic to wood, fast to twisty etc).

Some of my cars have no weight added, like my Fly Audi Quattro that competes in the GB Slot Rally Championship. Top ten last time out with just loosened body screws, but it has 4wd and drop arm. Might see if I can tweak it a little for this year.

Cheers
Dave

 

I would think that a certain mass must be required otherwise grip would be lessened through rear tires. There must be a trade off between losing too much weight and not being able to put the power down.

On a plastic track I would guess that a reasonable mass is necessary to keep the car in the slot, particularly if you are accelerating hard out of a corner.

slotmonkey.

 

QUOTE (slotmonkey @ 26 Jan 2011, 20:10) <{POST_SNAPBACK}>I would think that a certain mass must be required otherwise grip would be lessened through rear tires. There must be a trade off between losing too much weight and not being able to put the power down.

slotmonkey.

But the heavier you make the car, the greater the inertia, and thus more grip is required in order to prevent wheelspin, so it is not some proportional gain you make with weight. Also, the greater weight, the greater the centrifugal forces acting against lateral grio on corners, and trying to pull the guide out of the slot.... so I prefer to make my cars with the smallest, or no addition of weight.

Actually, the most acceleration is at exit of turns, both because the differential/potential is greatest, and because you are also dealing with centrifugal forces as well as linear ones.

As Mannimal said, it is easily possible to optimise most cars with very little weight addition. Giving the body and/or pod correct flex to load up the outside tyre, creating the best possible load psmm (per square millimetre - sorry I just made that up) will create best grip and best early acceleration.
- Think of the times you had an "equal" car with another driver, but they ALWAYS got better drive out of a corner, and leapt maybe 1/4 or even half a metre on you at the beginning of the straights . . . good tuning, good loading, and everything very "square" and flat.

I recently had a car in a proxy race series, which had a 29K rpm motor, low gearing, and weighed only 76 grams. But it had very good grip and drive out of corners, and because of low weight and low gearing, it had good brakes with an s-can. it worked well on wood, and on Scalextric track.

 

The best weight for a car is that weight which will produce the fastest lap times. Too many people get hung up with chasing ever lighter weight. I talk about non mag racing here. If I have a car which is traction limited (spinning its wheels under acceleration) then reducing the weight will probably not make it accelerate any faster. If I have a car which tips over well before it breaks traction during cornering then I either need to add weight down low of remove weight from up high. Vice versa if the car is spinning out.

Getting the right weight balance in some instances may not produce better times but the car is SO easy to drive as a result. Such a car usually does well in race situations as it doesnt deslot. On occasions Ive had cars that have been off the pace but easy to drive. They have usually ended up near the pointy end at races's end.

Tractive force = m*g*u. u is the coefficient of friction and it is not a constant but changes as m changes. So a particulat weight will generate more traction. Straight line acceleration can actually increase with additional weight IF you are traction limited in the first place.

You will enjoy extra tractive force during cornering as a result of additional weight but this will be equally matched by an increase in centrafugal force. m*v^2/r.

If adding weight decreases lap times it is hard to argue agaist this.

cheers
rick1776