## F1 in schools bearings

Post here information about your own engineering projects, including but not limited to building your own car or designing a virtual car through CAD.
flynfrog wrote:
dan217 wrote:
flynfrog wrote:what are your theories are they based on existing aero science? How did you come up with your design and what do you hope to accomplish with it.

If you read the description the facebook page with the extrusion im trying to get the air to meet at the point where the gas canister releases a burst of CO2 so the gas has something to push againt while the other not to have any extrusions is basical to control the direction of the burst of gas from the gas canister; so it helps it to go in a straight line rather than wasting energy producing life or downforce.

don't think of it as pushing against something. A rocket in space has nothing to push against. It is simply throwing stuff out of the back to go forward.

If you can imagine standing on a raft and throwing a large rock. I like the idea of minimizing lift and reducing drag. Do a little more reading on basic airfoils. while sawtooths have been used on wings to try to increase lift prevent stalling and reduce drag that doesn't mean they work in all situations. They are generally more of a band aid when trying to push the limit on an airfoil.

play with this
http://www.grc.nasa.gov/WWW/k-12/airplane/foil3.html

watch the drag and DF numbers. dont forget to adjust it for your speeds.

I am trying to get the air to meet up where the CO2 gas canister releases its thrust to create a high pressure point to push the car forward. The other idea of the ring without any cutouts is basically to just control the gas flowing out of the canister
in a straighter line as when you see the cars go forward all the gas just goes up.
dan217

Joined: 25 May 2012

dan217 wrote:snip..

I am not sure what you mean by the gas going up. The gas in the canister is going at a higher pressure than the gas in the atmosphere. That is why it leaves the canister. The hole you punch is the only thing that is going to be able to direct the gas. It will flow form high to low pressure and since the pressure is lower all around it once the initial velocity is lost out of the canister the gas flows every where.

Think of trying to blow a piece of paper off a desk its pretty easy when you are close to the desk but if you move across the the room you lose the ability to direct you stream of air.
"The question isn't who is going to let me; it's who is going to stop me."
flynfrog

Joined: 23 Mar 2006

flynfrog wrote:
dan217 wrote:snip..

I am not sure what you mean by the gas going up. The gas in the canister is going at a higher pressure than the gas in the atmosphere. That is why it leaves the canister. The hole you punch is the only thing that is going to be able to direct the gas. It will flow form high to low pressure and since the pressure is lower all around it once the initial velocity is lost out of the canister the gas flows every where.

Think of trying to blow a piece of paper off a desk its pretty easy when you are close to the desk but if you move across the the room you lose the ability to direct you stream of air.

I am trying to focus the air if that makes sense. For example if you open your mouth really wide and try to blow the paper of the desk it won't go very far but if your focus the air using your lips you will be able to blow the piece of paper further.
dan217

Joined: 25 May 2012

dan217 wrote:
flynfrog wrote:
dan217 wrote:snip..

I am not sure what you mean by the gas going up. The gas in the canister is going at a higher pressure than the gas in the atmosphere. That is why it leaves the canister. The hole you punch is the only thing that is going to be able to direct the gas. It will flow form high to low pressure and since the pressure is lower all around it once the initial velocity is lost out of the canister the gas flows every where.

Think of trying to blow a piece of paper off a desk its pretty easy when you are close to the desk but if you move across the the room you lose the ability to direct you stream of air.

I am trying to focus the air if that makes sense. For example if you open your mouth really wide and try to blow the paper of the desk it won't go very far but if your focus the air using your lips you will be able to blow the piece of paper further.

that would have to do with the shape of the hole punched in the canister not changing the angle of your ears. Instead of focusing on trying to manipulate air coming out of the nozzle work on getting a good overall shape. Read up on a few of the projects on here. Getting the basics right is worth more than a small trick.
"The question isn't who is going to let me; it's who is going to stop me."
flynfrog

Joined: 23 Mar 2006

That would have to do with the shape of the hole punched in the canister not changing the angle of your ears. Instead of focusing on trying to manipulate air coming out of the nozzle work on getting a good overall shape. Read up on a few of the projects on here. Getting the basics right is worth more than a small trick.[/quote]
I have read all about the other projects and know the basics now. The basic body shape is quite good a lot better than most people's even the cars on here i don't feel very comfortable posting the picture here as it has many new ideas and i have found a lot of loop holes in the rules. I am trying to win the best engineered car aswell so these "small tricks" help with that. I can email you the pictures but I can't post them on here.
For the rear spoiler I have gone with a simple teardrop as thin as we are allowed to go. For the front spoiler I am thinking of an airplane wing sort of spoiler. How will the height of the spoilers affect the aerodynamics?
I would have just done lots of experiments in the Virtual wind tunnel but our school doesn't have despite the fact every school competing in F1 in schools is supposed to have it. The teachers have no idea why they don't have it.
For the wheels I am going as small as allowed at 26m.m diameter. while the normal siize is 30m.m this is for aerodynamic purposes but would this mean additional pressure on the bearings as the wheel has to rotate more times to cover the same distance?
dan217

Joined: 25 May 2012

xpensive wrote:
Smokes wrote:...
Using the smallest size possible will reduce the rotating mass and hence reduce the amount of energy used to turn the wheels though this is still dependant on load.
...

This thread is breaking some serious ground now!

But seriously, this link is a good start to get things straight, it even has an on-line calculator, just take it from the top;

http://www.skf.com/portal/skf/home/prod ... ink=1_0_35

That is interesting but what about the fact that the bearing will have to do more revolutions to cover the same distance and this might increase friction because of the g forces created by the spinning bearing putting more load on the balls therefore increasing friction. Am i completely wrong?
dan217

Joined: 25 May 2012

Though I have promised both myself and richard not to comment anymore on this, but when tribology is part of
what I do for a living I cannot help myself;

If you hold a ball-bearing in your hand and turn one of the races clockwise, then turn the other one anti-clockwise,
how can you then imagine that one of the two completed processes demanded more energy than the other?

Sometimes the world is simpler than we make it out to be.

And btw, I believe that Lee Harvey Oswald was the shooter.
"Bernoulli is a nine-letter name"
xpensive

Joined: 22 Nov 2008

xpensive wrote:If you hold a ball-bearing in your hand and turn one of the races clockwise, then turn the other one anti-clockwise, how can you then imagine that one of the two completed processes demanded more energy than the other?

Sometimes the world is simpler than we make it out to be.

Indeed. I can't fault that analysis. My work is grounded in balanced load paths and equilibrium. If the internal analysis demonstrates a lack of equilibrium then there is something wrong with the internal analysis.

So I'm puzzled by Tok's experiment and the NASA paper. There's something missing between x's explanation and Tok's expermiment. What is it? Experimental error combined with a misreading of the NASA paper?
richard_leeds

Joined: 15 Apr 2009
Location: UK

richard_leeds wrote:
xpensive wrote:If you hold a ball-bearing in your hand and turn one of the races clockwise, then turn the other one anti-clockwise, how can you then imagine that one of the two completed processes demanded more energy than the other?

Sometimes the world is simpler than we make it out to be.

Indeed. I can't fault that analysis. My work is grounded in balanced load paths and equilibrium. If the internal analysis demonstrates a lack of equilibrium then there is something wrong with the internal analysis.

So I'm puzzled by Tok's experiment and the NASA paper. There's something missing between x's explanation and Tok's expermiment. What is it? Experimental error combined with a misreading of the NASA paper?

The missing puzzle piece is that motion is transferred linearly around the parts. Not angularly.

Try the two rulers and a pencil experiment. If you move the top ruler by 10cm, the pencil will move 5cm and the bottom roller stands still.

Now there are two ways to return the relative position between the two rulers to the same arrangement.

-If you move the top ruler back, the relative rulers arrangement returns to the original position and the pencil to it's starting point.
-If instead you move the bottom roller 10cm in the same way as the top one was moved, the relative arrangements between rulers is back, but the ball is 10cm apart from the original location.

Now when you look at the races, they behave like the rulers in the experiment. The balls like the pencil. In ideal conditions, the ball will roll on both races with no slip.

BUT the rulers have different lengths. The inner races is shorter. The balls center tangential translation speed will be he average of the tangential linear speeds of the races.

When you alternately apply 1 turn to each race, you input different linear speeds to the system. Since the speeds and distances are different, the energy involved will be different.
rjsa

Joined: 2 Mar 2007

xpensive wrote:Though I have promised both myself and richard not to comment anymore on this, but when tribology is part of
what I do for a living I cannot help myself;

If you hold a ball-bearing in your hand and turn one of the races clockwise, then turn the other one anti-clockwise,
how can you then imagine that one of the two completed processes demanded more energy than the other?

Sometimes the world is simpler than we make it out to be.

And btw, I believe that Lee Harvey Oswald was the shooter.

Lol you didn't answer my question. If you use a small bearing the advantage is that the mass is smaller therefore less energy needs to be used but on the other hand a smaller bearing would mean more load on the ceramic balls because of the fact that there are more revolutions therefor more centrufugal force is created. The sort of forces which keep the bikes in this link attached to the cage.http://www.youtube.com/watch?v=l6A1KJcpiXo
dan217

Joined: 25 May 2012

Ok Guys, here it goes:

It seems pretty obvious that there is a difference in balls' distance traveled for either the inner or outer race movement. Same must happen with speeds.
rjsa

Joined: 2 Mar 2007

Two different things are being discussed. Distance travelled by the balls & work done.

I am shocked that there is surprise at the difference travelled by the balls when either the inner or outer race is turned. X linked to the Wiki page on epicyclic gearing & I used the equation to calculate the distance travelled (based on 1 tooth per mm of circumference). The kinematics are just the same as a simple epicyclic gear set. Here is the derivation of the epicyclic gearing formula.

What I will also tell you from personal experience is that it is much harder to turn the sun (inner gear) than the anulus (outer gear) of an epicyclic set where the planetary gears are held in position (but allowed to rotate). But it is precisely the same with spur gears, it is easy to turn the fast shaft but much more difficult to turn the slow shaft. In both cases with no load on the input & output shafts.
tok-tokkie

Joined: 8 Jun 2009
Location: Cape Town

I have xplained this misunderstanding, due to illusion and relativity, to richard in a PM, but I give him the honor as moderator to present it.
"Bernoulli is a nine-letter name"
xpensive

Joined: 22 Nov 2008

I don't get all the mistery and drama...
rjsa

Joined: 2 Mar 2007

Sorry about the delay in replying to x, I've been away. As x described to me in a PM, there is an explanation for the observed differences in rotation.

We need to think about the movement of the balls relative to the inner ring, as opposed to the absolute movement in space.

xpensive wrote:- If you keep the inner race still and rotate the outer race one turn, the rollers will travel some 2/3 of a turn relative to the inner race.

- If you keep the outer race still and rotate the inner race one turn, the rollers will travel about 1/3 of a lap relative to the outer race, but still some 2/3 of a turn relative to the inner race.

Conclusively, the number of turns the rollers make around their own axis is the same, which is what decides the power-loss, both by hysteresis and viscous losses.

The reason why lifespan reduces with a rotating outer race, is that the rollers becomes subjected to higher centrifugal loads due to the higher carrier-speed of the rollers.

I suppose there is a possibility that the higher centrifugal loads would result in higher friction between the ball and the outer ring??? However would this only be a factor for very high rpm???
richard_leeds

Joined: 15 Apr 2009
Location: UK

PreviousNext