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Hi all you Slot car guys, Girls, and....
Something I should know, but for some reason, I have forgotten.
Weight of a slot car, or anything for that matter.

Weigh the car and you get XX. Weigh the Front and you get YY, Weigh the rear and you get ZZ. Simple.
XX=YY+ZZ But it never does. It's the same weighing Left and right. They never add up to the total sum. Gross weight.

WHY?

Got to be a scientific answer to this. Even if you use 2 Scales, exactly the same make model, and have been calibrated to the same degree. Even 4 scale, one for each wheel, the same. Never adds up to the total weight of the car.

Any of you Professors got a good answer, formula for this?

Cheers
Andy
 

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Lee Green
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Well that's because when you have half the car over the scales it's measuring more than half of it ... Try standing on scales with one foot , put the other leg out , just because it's not over the scale doesn't mean it's not weighing it ! Simples really
 

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Actually it is more complicated than that.

The difference is caused by the acceleration due to depravity.

Remember, "to inflibidy and blancmange" !!.

vbr Chris.

ps: What you are actually measuring are "moments" about the other end, you know, simple lever theory !!.
 

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Tony Condon
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Chris
thats disgraceful .it sounds to me if you are not taking this thread seriously
Pull your self together and man up

Cheers tony
 

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Well thanks a bunch guyes for telling me something I allready know.
There must be a way of doing this, so all =.
I'm sure you can come up with better ideas. This is School boy stuff, but come to think about it, non of us School boys.

QUOTE QUOTE (Flange @ 6 Nov 2011, 13:33)

Well that's because when you have half the car over the scales it's measuring more than half of it ... Try standing on scales with one foot , put the other leg out , just because it's not over the scale doesn't mean it's not weighing it ! Simples really

If that leg your sticking out is resting on something. Balanced. ??????
And if each wheel was sitting on it's own scale????
 

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Rich Dumas
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You might want to consider the fact that many balances will be affected by the magnets in the car. When I weigh cars I put a block of styrofoam on the balance and tare that, then I put the car on the styrofoam and weigh the car.
 

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Sorry, missed that bit. Why do I need to know?
Been playing with the balance of a slot car for sometime now. and have just started filling in a db by SCC IA. there is a page with a drawing of a Chassis. you feed in the total weight, & F/R & L&R weights. so, all being = which they never are. you can see where you may need to add, and where you may need to remove. Simple. (To get a, for example, 40/60 split F/R and a 50/50 L/R)
If a track runs CW, it will have so many left and right hand turns, so getting the balance right, could be the difference between winning or not. But, if you put that same well balanced car on a CCW (AC) track, it will perform in a different way.
That's it in a nut shell.
But if you carp at racing, as I am. it will not make the blind bit of difference.

anorak. No, Hoddie

QUOTE (RichD @ 6 Nov 2011, 16:26) <{POST_SNAPBACK}>You might want to consider the fact that many balances will be affected by the magnets in the car. When I weigh cars I put a block of styrofoam on the balance and tare that, then I put the car on the styrofoam and weigh the car.

OK, makes sence. What if you used lead?
Car on scales, 104g, heavey little car, resin bodied. Now turn scales off, remove car. place lead sheat on scales, turn scales on. reading 0.0. Place car on scales. reading 104g. No mag, apart from the two in the Shark motor. Non of my cars have mags, apart fom that in the motor.

OH!
 

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Ey Up Our Tony,

the actual quote is "to infinity and beyond", but my nephew kept holding his arms out wide and shouting "to inflibidy and blancmange" which we all thought to be hilarious.

So sorry that you do not !!.

Read my ps: that was the sensible bit, did you not get that ??.

Perhaps the gravity of the situation has escaped everyone.

In the mining world we have powered supports which are rated in tonnes, but is a 500T support capable of holding 500T mass, or 500T weight ??.


Aahh.

To accelerate or not to accelerate, that is the question.

vbr as always, Chris.
 

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QUOTE Skid mark
I repeat myself when under stress...... I repeat myself when under stress...... I repeat myself when under stress...... I repeat myself when under stress......

QUOTE Anyone else totally baffled

YES, ME!

QUOTE (Skid mark @ 6 Nov 2011, 20:03) <{POST_SNAPBACK}>How about sawing the car in half?


I think you mean quarters
 

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Well if you really want to know go to http://hyperphysics.phy-astr.gsu.edu/hbase/mass.html#wgt and I am absolutely convinced you will go to bed with a wry smile and a headache, especially if you follow the links. Suffice it to say the short version because it is all down to mass, force and gravity. If you way summint on Earth it's Mass is whatever, weigh it on the Moon same mass but one sixth of the weight - So I put it to you all lets have a track on the moon and that will make a level paying field then we can all Slug it out! BTW The slug is the unit of mass in the US common system of units. Good luck. If you do get to the bottom of it please let me know - Thanks - Rusty.
 

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Ok Ok, if you really want to know. The easy way, no real maths, physics, or anything difficult. Find the center of gravity for the chassis balance until level on a spare piece of tube or rod held from left to right (door todoor). Mark it, measure it and then you have front and rear balance point the "moment". Then weigh it and aportion the weight as a percentage, so if it's dead in the middle of a 6" (152mm) car each 3" (76mm) is 50% of the weight. Hold the tube Bonnet to Boot to get the left to right pecentages. There you go "Simples"
Oh I lied about no maths - sorry L to R do the same again
- Rusty
 

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Cheers Rusty,

Nice, someone else with a brain, good to make your acquaintance.

We engineers should stick together ??.

Saviour, I know where you are coming from, but it aint always easy.

Some things you can learn, given the right teacher, but others, you gotta just feel !!.

OMG that reads patronising, but I really dont mean it that way.

Some have an instinctive feel what is right, others have to learn it, same in many walks of life !!.

VBR Chris A.
 

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Sorry guys but I get the same weight to within about 0.5g which I put down to the repeatability of my cheap $12 ebay digital scales. Car weighs 92g on one scale and when balanced between two scales weighs 32g front and 60g rear = 92g total

Please allow for the slight difference in gravity between Australia and whereever you may live.


cheers
rick1776
 

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Tony Condon
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Hi Guys
I,ll endeavour to say something sensible for a change ,and yes chris I did see the comedy in your comment ,and Iam aware of where the original quaote came from ,my commnet was an attempt to piggyback off that houmour
right back to the problem in hand
Back in the dark ages there was an article in model cars on a thing called a balance bridge
Basically take a sheet of 1/4 inch thick blasa wood 2.1/2 inches wide 6 inches long .now take a piece of brass tube 1/8 OD and glue it dead centre across the middle of the wood at right angles to the length .Now cut a slot at one end down the middle of the wood (to take the slot guide ) this will need ot be acouple of inches long. Now trim the other end of the plank such that if you place the plank down on the bench ,on the tube it balances ie neither end touches the bench
you have now built your balance bridge
So what good is it
Well if you now place you slot car on the balance bridge along the length of the plank you will find that depending how far towards one end or the other it is then tha tplank will touch down at one end
So if the car has prefect 50: 50 balance and you place the middle of the car over the brass tube then it will balance again
So if you calibrated the balance bridge such that if the wheel base of the car is 100 mm you can divide that by 10 so you get 10mm increments and draw across the width of the plank 10 lines either side of the brass tube(on the opposite face to the tube ) you will see that the front wheels of your perfectly balanced car will be on the 5 th line in front of the tube and the rear wheels will be on the 5th line behind the tube
Now this is unlikely but what you might find is that the rear wheels are on the 3rd line behind the tube and the front wheels are on the 7th line infront of the brass tube you will see that the weight distrubution is 70:30 towards the back .
NO SCALES NEEDED,no need to worry about magnets
If you wish adjust the weight didtribution add some weight front or rear and replace the car on the plank and see where it balances
The cost of these components are about 20p and the only prblem is that you need to relibrate it for different wheel bases and it is a bit iterative
Hope i,ve explained that ok
 
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