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Izzy410 wrote:and the size of the wheel is 26.5 mm in radius and 16 mm wide. if the tyre flex with a thin wall the increase surface area touching the track can increase drag.

How?

I wonder if there are any ways to actually remove the vacuum at the entrance of the co2 canister.(i dunno the perfect word for the part.)
That will reduce drag i guess,but quite hard to be done.

Jersey Tom wrote:

Izzy410 wrote:and the size of the wheel is 26.5 mm in radius and 16 mm wide. if the tyre flex with a thin wall the increase surface area touching the track can increase drag.

How?

okay imagine a stiff tyre that doesnt flex the contact point would be like this

Red dot is the point of contact (friction area)



but if the tyre flex, the contact are increase, hence the red dot area is increased and more friction.



in simple term, just take a cirlce and roll it. its easier than taking an oval and rolling on its long side

pudin wrote:I wonder if there are any ways to actually remove the vacuum at the entrance of the co2 canister.(i dunno the perfect word for the part.)
That will reduce drag i guess,but quite hard to be done.

what you say does have some logic in it but not only in drag reduction but i think in power gained.

just imagine if there's a vacuum at the CO2 nozzle, the gas coming out is pushing against nothing. and can only push the air that is a bit further off where there is no vacuum.



like in this picture where the blue area is the vacuum. so the CO2 cannot push against any mass (air) and only upon reaching the greener contour (low velocity air) can it has something to push on.



Good comment. now i can figure something to overcome this......... hmmm back to thinking.


THANKS for both of you

Okay here's the view of the Turbulent generator. copied from Aixtreme Racing Germany. created a smaller vacuum around the CO2 nozzle. will post CFD data in the hour. off to dinner

That small holes quite hard to be done in the machine isnt it?
or you have other ways to manufacture it?
And you using a 3 axis cutter or a 5 axis cutter?
If 3,you will have trouble cutting the middle part of your car
Unless you use 2 separate balsa and glue it together

Izzy410 wrote:

Jersey Tom wrote:

Izzy410 wrote:and the size of the wheel is 26.5 mm in radius and 16 mm wide. if the tyre flex with a thin wall the increase surface area touching the track can increase drag.

How?

okay imagine a stiff tyre that doesnt flex the contact point would be like this

Red dot is the point of contact (friction area)



but if the tyre flex, the contact are increase, hence the red dot area is increased and more friction.



in simple term, just take a cirlce and roll it. its easier than taking an oval and rolling on its long side

Except rolling wheels are in contact with static friction, not kinetic.

Jersey Tom wrote:
Except rolling wheels are in contact with static friction, not kinetic.

so it still makes a difference doesnt it? if the tyre flex the contact is bigger so to overcome static friction it takes more energy and to overcome the following kinetic friction it also takes more energy.

Same concept of rubber tyre that is fully inflated and that of partially inflated. the surface area increases therefore more friction regardless of static or kinetic

pudin wrote:That small holes quite hard to be done in the machine isnt it?
or you have other ways to manufacture it?
And you using a 3 axis cutter or a 5 axis cutter?
If 3,you will have trouble cutting the middle part of your car
Unless you use 2 separate balsa and glue it together

we have machines you cant imagine of haha there's a manufacturing centre that we use that has facilities for almost anything you can imagine to cut.

plus. *cough* we can always glue it *cough*

heh joking. the parts in the car is made so that it can be machined by the centre we are working with.

anyone knows anything about the Co2 Catridge's Dimension?

Gluing is the best choice but remember the car must be made from 1 balsa block.
BTW nice render.
And,you could try close the hole where the tyre placed,i really dunno how to say this part either.
Because the air at the middle part will be sucked by the vacuum produce from the gaps between your tyres if you didnt close it.
Do you understand ?
I can post a picture if you want to.
Could you post your latest car Izzy?
And the readings too

Izzy410 wrote:

Jersey Tom wrote:
Except rolling wheels are in contact with static friction, not kinetic.

so it still makes a difference doesnt it? if the tyre flex the contact is bigger so to overcome static friction it takes more energy and to overcome the following kinetic friction it also takes more energy.

Same concept of rubber tyre that is fully inflated and that of partially inflated. the surface area increases therefore more friction regardless of static or kinetic

Completely different concept. Tires generate 'drag' through energy loss in hysteretic materials. Not friction. Not a surface thing.

Hey just thought i'd mention to you guys that for the world finals you can't make the car body from separate parts so you cant make it in 2 pieces and glue them together.

pudin wrote:Gluing is the best choice but remember the car must be made from 1 balsa block.
BTW nice render.
And,you could try close the hole where the tyre placed,i really dunno how to say this part either.
Because the air at the middle part will be sucked by the vacuum produce from the gaps between your tyres if you didnt close it.
Do you understand ?
I can post a picture if you want to.
Could you post your latest car Izzy?
And the readings too

understood completely. will do in the next few posts.

Jersey Tom wrote:
Completely different concept. Tires generate 'drag' through energy loss in hysteretic materials. Not friction. Not a surface thing.

Soooooo. im not so sure on the hysteretic materials part but from my search it indicates some sort of material memory? care to explain.

But i still believe if the tyre flex the surface area that is added will add more drag when in contact. and maybe your concept also factors in a part of it.

As to basizeland. i do understand the rule. part of it is bending it. well im not gonna break it. but bend it. im not gonna glue it. we have machine that can do it for us.

Okay. this is the latest car. Iteration number 12. lowest X plane pressure of 15.7 grammes. (managed to get 15.2 but found out some rule was broken)

we dont compute Cd anymore because its 'relative'.

good for getting to know your aero but bad if you only have the same type of engine in this case the standard CO2 canister. but if someone suggest otherwise please do put it on the table. so now we compute concrete pressure. but still missing some data because wheels are not turning and CO2 injection is not inserted into the medium. cant afford that computation at my personal PC. can do at school which is open in a month













If you need additional angle please do reply.

btw anyone can help me calculate thrust force for the CO2 canister? i cant get the math right.

maybe I missed it whats with the airfoil in the front? Also look at the shape of airfoils for low speeds. You dont want the sharp leading edges.