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Discussion Starter · #1 ·
Posted on here re motors and have had brilliant replies so thought i'd add my other current head filling subject. Chassis pans. Does anyone actually know the science of these sliding, wobbly bits of race cars.? Is there any hard and fast re tuning the pans with weight or controlling the distance each part can move forward/back/sideways? How does adding a load of metal to a chassis, then leeting it move help? I understand its about some sort of damping effect, sort of moving the mass of the car in stages, but would really like to know which part of the cars handling each pan action affects. Or am i asking toooooo much? cheers all Bungee.
 

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Graham Windle
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In a plastic chassied car the main objective is as you say to damp down the vibration and this is done by loosening the body screws ,however with todays variations and some chassis having motor pods loosening of the screws holding this can often help with the handling as it adds an extra bit of flexibility into the chassis there by keeping the back wheels on the deck and proding more grip ., making the thing work in a similar fashion to a brass chassied car with the "wobbley bits".
The main purpose of the "wobbley bit" are to transfer the weight in a desired direction ie forward under braking onto the guide and rearward under acceleration onto the rear wheels whilst at the same time leaving enough weight on the guide to stop it lifting out of the slot ,the floppy side pans are to prevent the car from tipping out in the corners by transfer of weight in a side ways motion.
Newer theory of car handling such as that in the Mossetti style of chassis has a small degree of side ways movement to allow the car to flex also in that direction also .The bscra site has a good article on chassis design.
 

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Matt Tucker
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3,549 Posts
I run a Slot-it HRS chassis (with a fly evo 2rs racing sereis (Jeevers one) body top) in our unlimited plastic chassis GT class. We run each series over 5 weeks with 4 qualifying weeks and the last week being the series final. This is the first time I've run in this series so I've been trying out lots of diff mods to the chassis to get the fastest best handling car. One of the best improvements I found was to put a suspension kit in and make it really quite loose and loosen the screws holding the front of the motor pod quite a lot. It made the car handle corners significantly better and knocked 0.4 seconds of my average lap times. I was amazed as my previously help belief was to get the chassis all nice a rigid - however thinking about it the bit that has to be rigid is the motor, gear and rear axle combo with the rest having some flexibity in to absord cornering and vibration inertia.

However most plastic chassis don't allow you to add this level of flexibility without significant modifications.

Matt
 

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Senior Slot Car Mechanic
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2,230 Posts
QUOTE Newer theory of car handling such as that in the Mossetti style of chassis has a small degree of side ways movement to allow the car to flex also in that direction also.
Sorry Graham,nothing new there,I was doing that as early as 1964.

By 67 I had so much lateral movement in the back end,that the tires would actually come outside the body by 1/16 of an inch.I had over 3/16 rear lateral movement in my 1/32 cars.

Basically,they steared themselves around the corners.

There ain't no science involved,it's all witchcraft and smoke and mirrors.
 

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Graham Windle
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4,442 Posts
That would be the canadian brass door knocker style of chassis Al and not a well sucked popsickle stick
 

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I have a somewhat different take on floppy pans and two-piece chassis.

Basically, a slot car chassis vibrates due to a number of factors: motor vibration, axle assembly imbalance, roughness of the braid path and track, etc. The body, whether hard plastic or Lexan, also vibrates or resonates, both directly and sympathetically.

All of these various vibrations can interact, either cancelling or reinforcing each other resulting in negative effects on handling. Floppy pans or two piece chassis assist handling by "de-coupling" the chassis vibes from the body vibes, preventing these interactions.

Additionally, de-coupling the body from the chassis assists handling in turns by delaying the transmittal of body movement to the main chassis.

There seems to be a point where the amount of relative movement between the two parts provides maximum benefits. Too much relative movement between body and chassis, or between chassis parts in the case of a two-piece chassis, can have a very negative effect on handling characteristics. Generally, movement amounts above the "sweet spot" result in a very loose or tail-happy car and movement amounts less than the optimum amount result in less slide or looseness than will give best cornering speeds.

It is pretty common now in 1/24 non-winged racing to damp or control relative movement between chassis parts using filement tape strips and the width and placement(s) of the tape can give very noticeable effects.

The choice of body material (and therefore flexibilty) makes this very clear, but material choice also affects weight of the body and thus can confuse the issue. However, on the commercial side we notice handling differences between Lexan bodies and the clear PETG material some companies use for vacuum-formed bodies. These materials have very similar weights yet in some instances the handling differences are large due to the flexibility difference between them.
 
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