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  Author    Wind Tunnel Project  (currently 1,715 views)
Allan Brown
Posted on: December 20th, 2014, 21:27:54
Attachment: dscf7400a.jpg - 137.71 KB (810 views)
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Back of rear diffuser.

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Graham Bichard
Posted on: December 21st, 2014, 15:46:14 Quote Report to Moderator
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Good photos Allan.  That's the reason for my experiments - to smooth the airflow under the car and try and reduce drag.  Putting a smooth cover over the subframe may also keep some of the dirt offof the fuel pump (on my car).  I would have the fuel tank in the way too, of course, so couldn't raise the rear in a diffuser style.

Interestingly, I would look to have a lip going up the front of the rear subframe, between the subframe and the heel board if room allowed.  I've read this is the best way of achieving a smooth flow.

If I get the gearbox stripped down tomorrow, I'll try and set up the tunnel and show the results I obtain.
Also - are there any other MM models anyone knows of I could try using, preferably with a more accurate underside?
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mike brown
Posted on: December 21st, 2014, 20:54:04 Quote Report to Moderator
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I haven't seen my kit resin 66 and 67 models for a while (buried in a box somewhere) but I recall them being surprisingly accurate when I got them. Might be worth a look.
Mike

Last modified December 21st, 2014, 20:54:51 by mike brown
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Graham Bichard
Posted on: December 22nd, 2014, 11:04:38 Quote Report to Moderator
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This isn't the, quite large scale, Tamiya type kit is it Mike?

There was a link on here (going back a little while) for one of these that was on ebay.
Unfortunately it was a bit rich for me, but would've been a good size to use (not sure how accurate the underside was though).

I had also thought about the plinth mounted Le-Mans type models, but was put off a bit by the cost (and then dismantling it!) and the thought that the underside might not be too accurate (having some sort of mounting point probably moulded in).
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Graham Bichard
Posted on: December 22nd, 2014, 11:14:59 Quote Report to Moderator
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Quoted from Allan Brown, posted December 20th, 2014, 21:25:47 at here

I remember when we did the bonnet we originally dipped the the whole front of the bonnet but found the air flowed better with about 5" of the front of the bonnet left in place. 



Should've added earlier - this is the kind of thing I was thinking of, for the bonnet/radiator air extraction.  Are you still using this Allan?  How did you determine the air flowed better with the front edge of the bonnet remaining?  Wool tufts?

Have you considered putting rubber skirts along the lower sills of your car (regs permitting, of course).  I'm thinking something like conveyor belt type stuff (quite rigid) mounted behind the wheels, probably fixed on the lower floorpan bit.  Not really practical for a road car, but I believe containing the air within the floorpan area (as opposed to spilling out the side between the front and rear wheel) can have a big effect (as proven by Colin Chapman!).   One thing I have learnt through investigation/reading is just how much air is forced around the sides of cars, not up and over as you might expect.  In fact this is something that my mini tunnel might be able to show.

I'd love to experiment with the florescent water (as used in F1 these days) - it should be fairly easy to set something up.  That would require a working car though   .

Last modified December 22nd, 2014, 11:15:28 by Graham Bichard
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mike brown
Posted on: December 22nd, 2014, 17:33:31 Quote Report to Moderator
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This is the one I have.

Here is another.

And this is where I got the pictures.
http://www.marcos-jp.com/e-Miniature_Models.htm
Mike
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Graham Bichard
Posted on: December 22nd, 2014, 19:23:44 Quote Report to Moderator
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Yep - that's the one I was thinking of!  A good size too.
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Graham Bichard
Posted on: January 3rd, 2015, 18:09:26 Quote Report to Moderator
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I haven't forgotten about this - just finished the gearbox rebuild.
Back to work on Monday so progress may slow, but I'll let you know how I get on eventually!
Happy New Year
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Allan Brown
Posted on: January 3rd, 2015, 22:09:46 Quote Report to Moderator
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I don't use that bonnet anymore due to having a Carbon Flip front now.
I am really annoyed that I can't find that video of my wind testing. I used a large fan and a lot of talcum powder and videoed it from the side, you could clearly see how the talc flowed over the car. We also used cotton wool which worked well.
I still have the fan so might try it again one day.
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Rodger Howard
Posted on: January 4th, 2015, 10:30:57 Quote Report to Moderator
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What did you actually achieve from the wind tunnel testing? Wouldn't it have been easier to read the results of the testing of the transx car at Mira?
I would have thought concentrating on getting the standard items correct to improve corner speed and stability was much more important from an overall lap perspective for the majority of us. Lets face it , undertrays etc will preclude you from running in the majority of FIA classses.
I bought a copy of the original marcos homologation papers from the 60's and made sure my car met them in the first instance during the process of my build.from the lack of interest in my posts on my car it appears that esoteric factors are much more interesting for the majority of forum members which i supose is great if your goal is to think about things rather than action them for a meaningful outcome.
My goal is to race at Lemans with a stable reliable car in 2016 or 2018. Stop by and say G'day.
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Graham Bichard
Posted on: January 4th, 2015, 16:30:00 Quote Report to Moderator
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Rodger, I'm not building the car to compete - I'm aiming for a nice long legged GT car hopefully (one day!).
The wind tunnel is for a college project  and my idea for the flat bottom undertray is to smooth airflow, hopefully reduce fuel consumption, improve refinement (by reducing wind noise) and hopefully help keep some dirt off of the fuel pump.
I'd like to think the car will be IVA'd in time for the LMC 2016 - that's the target, and will be sure to cheer you on!  (I admt, it may not have any fancy underfloor arrangement though - I'll just be happy if it materialises on the road)

I seem to recall when Peter Stephens designed the body kit for the MG ZT's, he stated his aim was to remove lift from it (as opposed to producing +ve downforce).  One of the ways he went about this was by trying  to manage the flow under the car.  But if the MM is actually neutral lift already, by smoothing the underfloor some downforce may result (if class rules allowed you, of course).  
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