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So as those following my stalled Vanwall build will already know I'm off on another project without of course finishing the first......

I got to thinking after another of those frustrating race nights (with folk who actually buy modern competition cars and practice (for hours and hours) as drivers) where I always seem to come last.........

What I need to do is build a car (an F1 of course as that's my thing) which will have a clearly unfair advantage so I can go faster!

So I thought well there was that car that was deemed legal just for that one Swedish GP - the Brabham BT46B. As most will know there was a big fan in the back and a skirt around the bottom so it literally sucked down onto the road.

like this....

IMG_2398.JPG

it just happened that I finally got one of the Spanish Scalextric BT46's and I found some drawings and hey, with some thining and lowering its not bad.

so I did some drawings.......

and then I started building........

IMG_2400.JPG

IMG_2404.JPG

The real problem seems to be that with slot cars there's, ...... well, a SLOT, so I'm never gonna get the suck I really need. I had ideas about making two skirted zones one under each side pod, hoping that provided the car didn't slide too far (it shouldn't as it'll be sucking!) adhesion should be better.

Then I thought, heck the speed, power and aerodynamics at 1/32 just aren't like the real thing so maybe the fan will overcome the slot problem.

So I'm just going to build it and see what heppens. This is where I am now....

IMG_2399.JPG

Question - anyone know where I can get a 14mm diameter fan / propeller / axial impeller from???????????

I'll update as it evolves (and it'll be quicker than the vanwall which I WILL finish afterwards)!

Andi
 

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.. Leo A Capaldi ..
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Hello,
I am interested party in this. Have 2 Brabhams in exactly the same circumstance. I thought it would be easy to use a cooling fan from a laptop computer - still looking for one small enough. Have thought about using a small minilite wheel but difficult to get the blades right.
 

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You had just better hope that while it works like the real thing, real life is not emulated by the event officials and your creation of imagination and art becomes a shelf queen within 24 hours of a wheel turning.

Great work so far of course!
 

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Nice ! Also curious as to how this works out as (also) in my distracting-me-from-what-i-should-be-finishing project stack is a usefully wide 1/24th Chaparral 2J that's just begging for working fans. More or less decided on an anglewinder with a crown mounted on the "clear" end of the back axle to run the fan, or fans if I can get them to fit.

Didn't look for actual fans or propellers but think you'll get what you need out of a piece of thin aluminum sheet - scribe out a circle, cut it and drill a hole dead center, cut the blades and twist them to the appropriate angle, and then secure it on a piece of threaded rod with nuts maybe ? Good to be able to tweak the angle of those blades...

Re suction around the slot; thinking it a good idea to cover the slot as much as possible a (ie with a thin strip of lexan) and drawing from around it but maybe hooking something up to the guide that maintains it's position over the slot while the car drifts is possible also ? Skirting would be good...

Hmmm...

Keep posting updates ! That looks excellent and pretty sure it'll work...

And if it works well enough to get banned you can put a bag on the back and rent it out as a track cleaner instead !

Cheers,
S.
 

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Fantastic, what an idea.
I'll follow this build with huge interest.

Another great 70s F1 car.

I was looking at getting an ostorerro Lotus 79 but I think I'll hold back now, as it will be obsolete once this cars finished.


Good effort Andi.
 

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Al Schwartz
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OK - let's play a game - it's called "Fun With Numbers"

Air pressure at sea level is roughly 1000g/cm2

Assuming the body of the car is about 3cm wide at the rear, 13 cm long and tapers to a point at the front, the area is (3 X 13)/2 or 19.5 cm2 - let's call it 20 cm2

If we could pull a perfect vacuum under the car, the down force would be 20cm2 X 1000g/cm2 - 20 Kilos! (that would bend a few axles!)

Obviously we neither need nor want that much force - how much do we want? How about the equivalent of the down-force provided by a moderate magnet - say 200g.

So how much vacuum is that? 200/20,000 = 1/100 = 0.01 or 1% of 1 atmosphere or 7.6mm of mercury.

Now mercury is a nasty, toxic substance (that we used to play with when I was in school) so let's convert it to something else. 1 Atmosphere = 34' of water = 1036 cm. We need to be able to lift a column of water 1036/100 = 10.4 cm

This is 1/10 or less than the vacuum pulled by the average vacuum cleaner.

The experiment is simple:

Build a body mock-up and install fan

Attach a flexible tube to the body (air tight seal) and attach the other end of the tube to one leg of a U-tube containing water (beginning to sound like a high school physics class?)

Support the body mock-up in typical operating position

Turn on fan

Measure rise in column of water in leg attached to tube.

Results to be written up in standard form and turned in next Thursday

EM
 

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You what?


Andy had a chance to belt this thing round Walter's track last night and I have to say it's already pretty quick, even without the body and front axle, etc. It's going to be fun timing laps with and without the fan working. He seems convinced that this is going to be a race winner!

By the way Andy, it's my Dremel you need to cut the axle down not my bloody hacksaw. Bring it over and we'll grind the end flat too.
 

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Some years ago I built a slot car with a fan to suck it down to the road.
Getting the fan sucking up the air was no problem, and it was quite quick round the track. Quite quick but an otherwise similar conventional car was slightly quicker.

That was without skirts, so the next move was to fit some skirts.
Static pressure tests were quite encouraging, but trying it for real, didn't produce a performance improvement.
I tried lots of different ways to make the skirts work and ended up with either
Enough load on the skits to stop them leaking too much which reduced the load on the wheels and produced drag
Or
Reduced the drag and put nearly all the weight on the wheels which resulted in too much leakage to achieve much of a pressure differance.

Even with skirts it worked well enough to be quite quick round the track but an otherwise similar conventional car was still slightly quicker.
After a while I gave up on fans & skirts and decided I'd be better off building conventional cars. Maybe somebody else will find a way of making it work better????

Best of luck with the Brabham, I reckon there's every chance you'll get a model that looks great and goes pretty well. Quick enough to beat all the conventional cars? That's a huge challenge.
 

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I think it was E.S. Young who wrote this engineers prerogative: "The first concept of superior principle will always be beaten by by a proven example of established practice."

I say press on and go for all maximum of downforce!
 

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Conti - you are daft as a brush and I really love your car! Could you build two please?
 

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Nobby Berkshire
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"Suck or blow?"

It won't suck! It's impossible to suck a slotcar to a slotted track unless the suction is to the sides of the slot. And in such a tiny car the suction face will be so small it will make zero difference.

But if you get it to blow then it might push your car along a bit faster
 

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Screwneck's observation present just another small challenge; the volume of air that can enter through the slot must be mitigated by the volume of air that the fan can suck. Add a vane or two. You could create a skirted tunnel where there is no suction too. There is always a solution. I think you should keep going.
 

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very creative, good luck with it!

I'm tipping the guide would do some work sealing the front of the car? I understand it won't be a seal as such however the volume of air escaping that way will be a lot less than the rear.

should you build a twin chamber vacuum under the car imagine when it gets sideways!!! actually it's not that hard to imagine, it'll be the same as a sideways mag car..

I'll be following this one with interest,

Chris
 

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Get a few of those whistles like the ones in Marc's link and figure out how to cut one apart and fit it so it turns easily... they turn very easily in the whistles... I have had one. Let the speed of the air flowing under the car make it turn.

Let it be for show only... it is simply not feasible to get it to actually make the car go faster than a well-built and carefully set up conventional car.

Reread what Gone Racin wrote and really, really think about it. Putting down working skirting and expecting the motor to overcome the extra friction is asking too much.

Magnets, anyone?
 

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I built a chassis for a, then popular, 1:24 thingie wedge many years ago. They didn't come much more wedge like than this particular shell. As part of the build I put clear lexan sidewalls on the body, as high and long as was allowed then.

The chassis, being 1:24 was wide so I wanted to keep the weight down. In order to do that I cut a big rectangular hole in the centre of the chassis. The car went like a proverbial rocket! What I didn't realise was that the shell sucked the air through this hole and out the back, a huge empty space. Remember this was in the days before F1 cars had skirts and things. The sidewalls helped to keep the displaced air on top of the body as well as acting like the vanes on a dart in corners, stopping the car sliding too much. I'm amazed that this principle has only just been adopted in F1, behind the airbox.

The point is that this project of Andy's could well work but other considerations such as additional gear friction, weight, and aerodynamics also need to be included, and I'm sure Andy will be doing that, knowing him.

Hats off time, this is a great project by a great guy!
 

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mac pinches
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Throughout history there have been madmen thinking they can do what other
people keep telling them that there "thing" will not work it seems like we have
one of these guys in Andy.
His thinking reminds me of of other nutters of the past, two guy spring to mind,
they had these strange idea,s also,, one of which made many people chuckle,
they foolishly thought they could leave the surface of the planet !!! the idiots
where called Wright, i think they lived somewhere near a place called Kittyhawk.
in the US of A, i could be wrong ?
Mac P
 

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Guys,I sort of get the feeling that Andi, is building a Brabham Fan car in 1/32 and he wants the fan out back turning in order to look good going around without actually creating suction. As far as the rest of it goes , I think he's having a bit of a wind up!
Sounds like he's got a few bites.


Although I might be completely wrong and the guy will turn out to be a genius.
 
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