F1 in Schools Help - basizeland's project

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flynfrog
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Re: F1 in Schools Help

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I would remove all three rudders your car is following on a string no need to add directional stability

also the more you can fair in the wheels the better

basizeland
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Re: F1 in Schools Help

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yeah makes sense not to have anything. I want to hire an accelerometer that fits into the canister chamber and then i will be able to tell the max speed and whether it is moving sideways down the track or lifting off the track. One reason that i added it is because you see the car hit the side of the track sometimes which slows the car down.

I am using normal economy steel bearings that i have pulled the seals out of and washed all of the lubricant out so that they will spin as fast as possible but because i took the covers of they have got little bits of grit in them which is slowing them down. with these bearings our car run a 1.045, I am looking at trying some ceramic hybrid bearings and some high speed cage bearings to see whether there is any improvement.

Last year we bought full ceramic bearings from the US but when we got them they seemed to run rough but were still quicker then the normal steel bearings so we used the ceramic bearings in our race car for the national final and used steel ones in our display car because it cost us $200 for four ceramic bearings.

The organisation that runs F1 in Schools is REA and they keep one of the cars after the event and we didnt realise until we got home that they keep the car with the ceramic bearings so we have been trying to get them back and we just found out that they took the car over to London for the world final and they are putting it in the Australian embassy. which means that we wont bet the bearings back.

We were going to get the full ceramic bearings again but are not sure whether it is worth getting them again.

bazanaius
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Re: F1 in Schools Help

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flynfrog wrote: your car is following on a string no need to add directional stability
missed that bit in the rules! in that case yeah, get rid of that rudder altogether. I think keep the front end plates to break the beam - I like that idea ;-)

basizeland
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Re: F1 in Schools Help

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I managed to run some cfd on the new car and here is the pics

these are showing pressure
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These are showing velocity

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The values that it gave out were alot higher then the previous car this cars is
Drag Cdx 4.909146E-01
Side Cdy 3.669407E-03
Lift Cdz 8.417304E-02
compared to the previous car which was
Drag Cdx 3.902936
Side Cdy 6.427080
Lift Cdz 1.006333

Jersey Tom
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Re: F1 in Schools Help

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You mean a lot smaller.

How do you know your CFD answers are any good? And not just junk with pretty pictures? For example it doesn't look like there's any flow out of the CO2 canister. I'd suspect that will have an effect on the rest of the airflow.
Last edited by Jersey Tom on Sat Sep 26, 2009 5:29 pm, edited 1 time in total.
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Jersey Tom
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Re: F1 in Schools Help

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Also..

I assume, and hope, that you're using the narrowest wheels you can? Where do you stand on body width?

I'd think you'd gain a lot by fitting that CO2 canister housing down much lower and out of the air. Having it sticking up into the airflow is just giving you extra surface area.
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basizeland
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Re: F1 in Schools Help

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Im not sure whether the cfd answers are any good and i know some of the other teams have used Fluent but I managed to get a copy of fluent but i dont know how to use it and i cant get the car into the right format to use it in fluent.

I dont think that the program that i am using is capable of having the co2 flowing out of the canister.

The wheels are 15mm wide which is the minimum the car is 60mm wide although it could be 50mm wide the back cant be any smaller because the wheels must be visible from the top and side so if i make the car skinnier the wheels will have to stick out of the car.

The co2 canister housing is as low as it can go because there is a rule stating that the lowest point of chamber to race surface is 22.5mm which is what i have it at.

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flynfrog
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Re: F1 in Schools Help

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I would blunt the nose of the co2 chamber points are for super sonic flow

ideally it would be an airfoil cross section.

Look up naca air foils there are even free programs that will five you a point table you can load into your cad software


can you adjust the cell size on your cfd program? it looks to be on the large size.

basizeland
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Re: F1 in Schools Help

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Flynfrog is this what you meant by using naca airfoils for the co2 chamber

Image

Mystery Steve
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Re: F1 in Schools Help

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basizeland wrote:is this what you meant by using naca airfoils for the co2 chamber
Would have to see a top view. Airfoil shapes have significantly lower drag coefficients than spheres/cylinders; nearly an order of magnitude less. (As a side note: look at the shape of most slender fish, such as trout or salmon. The shape of their body, looking from the top, generally has the shape of a typical NACA airfoil. This is an adaptation that increases the efficiency of their energy usage as they swim through the water.) The reason an airfoil has such a significantly lower drag is due to flow separation at the back end. If the flow can be reintroduced to the free stream smoothly, the low pressure wake that is left can be minimized, thus reducing the drag.

One complication that you would have to consider is the fact that the CO2 cartridge is also contributing to the flow. If the wake left by the body is the same size or slightly smaller than the plume from the cartridge then that should be sufficient. This is why Jersey Tom recommended including it in your CFD, if possible. I'm not specifically an expert in CFD, as I work in FEA and Hydrocodes, but if you post any information on boundary conditions and mesh sizes, some of the guys here might be able to give you some insight as to how valid your results are or how you could improve them.

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flynfrog
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Re: F1 in Schools Help

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it should start to taper back to the CO2 nozzle. Also the leading edges of your side pods should be rounded

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flynfrog
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Re: F1 in Schools Help

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also you want your Cp behind your Cg for stability

basizeland
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Re: F1 in Schools Help

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here is the picture from the top

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mep
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Re: F1 in Schools Help

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Do you need any downforce?
I cant see a reason for it so you don't need any wings on the car.
You can remove the small wing on the rear.
Edited: Ok, I checked the rules now you need useles wings

Instead you can pay more attention to the way you cover your wheels.
Can you rise the side pots so that they are as high as the highest point of your wheels with having them still visible from the top.
Maybe it is better to let the air escape to the side behind the front wheels than to the top. You can take some race cars with covered wheels as example.
Try to improve the air deflection in front of the rear wheels on the underside of the car.


For the CO2 housing try to optimise the way it is attached with the rest of the car. Maybe it is better to have the cylinder far away from the car body connected with some thin struts. The flow around the lower site of the cylinder could be improved by this. Similar to the engine of a airplane, who is mounted below the wing. This is a good thing to check with your CFD software.
Last edited by mep on Mon Sep 28, 2009 4:33 pm, edited 2 times in total.

bazanaius
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Re: F1 in Schools Help

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mep - if you go back to the first post in this thread there is a link to the rules of the comp. These give answers to some of your questions about wings, height etc.

flynfrog - some good suggestions, could you explain your last point so basizeland (and anyone else interested!) understands why? I guess just pointing him in the direction of a useful google search would work!

re. tapering at the back of the co2 holder - does the cannister have to fit into the model without modification? i.e if you taper the back of the cannister, it wouldn't fit anymore from what I can see?

Would rounding the leading edges of the sidepods be useful given their proximity to the wheels? I'd be interested in some smoke pics from the tunnel of this area in particular as I think it's likely a lot of drag could be created here, which wouldn't be picked up in the CFD you're running at the moment.

Interesting idea about the flow of the cannister interacting with the wake, and an even better idea about how to deal with it in a really simple way! My first response was to try and rig up some kind of CFD/Test!!

Basizeland - did the second set of figures from your cfd really come out that low? Or possibly, did the first set come out that high? That is a significant decrease in all three forces, given the amount of changes that were made.

as suggested I think looking into the validity (or the interpretation) of your results is a worthy pursuit.

B