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color01
2010.09.26, 06:20 AM
Had to do it, I made a rear diffuser attached to the motor mount of my MR03. This is the last of the "trifecta" of aero devices I'm going to fab for my Z, other things like canards and vortex generators are probably not worth the effort and would be very delicate. No idea if it works -- in fact, I really don't think it will because the airflow underneath the car is probably not great... but I'll test it out eventually. The only thing I really like about it right now is the fact that it will look sweet under any racing body I can think of.

Meh... who knows? :)

wight
2010.09.26, 07:13 AM
I can see that it would be beneficial on a body with a long rear overhang as it would prevent air getting trapped in that area so much,if it does get trapped that is.As you say in this small scale it's difficult to know if it will do anything.
Perhaps covering under the motor will help also.
None the less it's a very interesting little experiment.

mleemor60
2010.09.26, 09:16 AM
Brian. Create one with a venturi in it.

arch2b
2010.09.26, 11:44 AM
people have been trying this since the mr-01 days.

its just as easy to make a full bottom plate as mentioned earlier. just need to figure out how to allow easy movement of the motor pod/h plate but this was done in 10 minutes with an autoscale case plastic sleeve. i've done this before back in the mr-01 days, again in the early mr-02 days.

http://mini-zracer.com/mini-zgallery/data/649/medium/IMG_19431.JPG

color01
2010.09.26, 02:55 PM
Did it work back then? Because I just tested the one I made, and not only does it not do anything noticeable, it also snagged a bump and broke within 3 minutes. Doesn't seem especially promising.

EMU
2010.09.26, 04:16 PM
Judging by the way that your mounts, it will have a good deal of movement, espially over bumps. Which is why it will snag the track... You may need a mount on the front of the dffuser as well to keep it from moving as much.

arch2b
2010.09.26, 04:51 PM
Did it work back then? Because I just tested the one I made, and not only does it not do anything noticeable, it also snagged a bump and broke within 3 minutes. Doesn't seem especially promising.

well, we don't see them nor talk about them much so i would have to say it was just as curious and debatable then as it is now. if it had proven viable, i think we would have seen lexan precut sheets sold by now.

also keep in mind, the level or skill in racing has improved greatly since the early days as well.

ruf
2010.09.28, 12:03 PM
Yah they kinda sucked back then. That's why I'm pleasantly surprised that your front diffuser has an effect. Will also investigate.

I would suggest tying the diffuser to the the t-plate mount so that it has less of a tendency to move and catch the front edge. I assume you are also at 11 degrees.

color01
2010.09.28, 02:25 PM
I eyeballed it, it was somewhere around 10 degrees before I broke it. :rolleyes:

I'm working on making a removable flat floor for my car so it can better feed a rear diffuser. V2 of the diffuser I'm not sure where to mount, as I want the bottom of the motor mount to still be as low as possible. I think I'll start off the diffuser farther back, and then make the diffuser mount wider, two "arms" instead of one.

(I have to say though, with all the aero stuff going on the car it's getting a bit fat. I'm going to have to use disk damper and no top shock to keep this car at minimum weight... so this better be worth it.)

Felix2010
2010.09.28, 06:28 PM
That's a great setup arch! Nice job. I love all this info guys, it seems Mini-Z is getting to the level of at least 1/12th pan Car in terms of performance tweaks and racing level IMHO.

The new MR03 along with performance enhancing parts from PN, Atomic & Reflex made the MR03 unbelievably consistent and fast. Now with Aero kits, bottom "panels" like Kyosho's new CF chassis plate (And also Kyosho Teflon Tape and even Color0's thin clear tape aero tweak:)), lightweight windows (I saw some on EGR - MART, thought it is was interesting but all my fave kits Sold-Out:(), And new Rear wing options (Reflex's wing looks great) --- All this combined is making Mini-Z more of a "True" race chassis/class than ever before. Hopefully this Mini-Z surge continues and we see more and more growth. From what I've seen in only 5 years in the Mini-Z game is nothing less than amazing.

Phil Ng, Color0, CT, Joe C., Atomic & Co. including our USA rep SaiTam, and everyone else I forgot to mention, keep up the great job guys. Kyosho seems firm on continuing to enhance the Mini-Z racer, so all of the "Little Guys" and new up-and-coming tuning parts companies - You guys are making Mini-Z racing what it is today. Again keep up the excellent work!

This Mini-Z Science thread is awesome. The Motor thread is cool too.:D

EMU
2010.09.28, 08:42 PM
Brian, only worry about weight in 70t classes. With more power, additional mass can actually help the car more than hurt it. Obviously, more downforce is important, but in general, as you increase downforce, you will need stiffer springs. Im sure at this scale, it wont be as important, but I wouldnt ditch a top shock to add a diffuser and keep weight at a minimum.

Most of my mod cars are a little overweight (a gram or two above the limit), but all my stock cars are underweight (so I need to add weight at events). I focus on keeping everything simple in stock, and keep weight low. Mod, I want the car to be very easy to drive, and have a lot of steering to the point that I dont need to push the car to turn fast laps.

color01
2010.09.29, 02:53 AM
I use stiffer T-plates with a disk damper than I do a tri-shock, so I have gotten away before with no top shock plus a disk damper. I guess Kenon is a little bumpy, my car always handled better with soft bump stiffness. Wish there was a T-plate that was hard in roll but very soft in bump so I could have a wider bump stiffness range to tune in.

My center panel is done, and made removable. Looks like a cross on the bottom of the 03. :) Rear diffuser V2 will be coming along soon.

Rune
2010.09.30, 01:53 PM
Here is a floor I made for the 03.
Adds 1,2 grams of weight.
Thickness of the sheets used are 0,25mm. It is quite stiff, and are easy to cut and bend to shape.
The air will be routed out at the rear, and should help regarding air beeing trapped inside the body.

http://lh5.ggpht.com/_2uRHE7AV3zs/TKTavccjRJI/AAAAAAAACtc/I0E_Zv3qVck/s1024/IMG_7209.JPG
http://lh6.ggpht.com/_2uRHE7AV3zs/TKTavVN47ZI/AAAAAAAACtY/4njolmY3z7Y/s1024/IMG_7206.JPG
http://lh3.ggpht.com/_2uRHE7AV3zs/TKTavHx6-sI/AAAAAAAACtU/teWBkNmKGRI/s1024/IMG_7202.JPG

color01
2010.09.30, 01:56 PM
Looks good Rune, couple of questions for you:

1) What material is that? Vaguely resembles Kydex but that stuff was pretty flexible.

2) I wonder if that "diffuser" (it's not really a diffuser anymore) shape is more or less effective than a traditional one?

3) How are you getting the batteries out of the car?

Good to see other people investigating this with me. :)

Rune
2010.09.30, 02:07 PM
Looks good Rune, couple of questions for you:

1) What material is that? Vaguely resembles Kydex but that stuff was pretty flexible.

2) I wonder if that "diffuser" (it's not really a diffuser anymore) shape is more or less effective than a traditional one?

3) How are you getting the batteries out of the car?

Good to see other people investigating this with me. :)

1: Material is 3M 467MP. Backside are with 3M 200MP Adhesive.
2: I am doing testing on it to see if the angle and even if the "flap" is doing anything. Same goes for the whole floor. I have a bad feeling for the air that goes in the front of the chassis. This can be trapped by the "endflap".
3: The batteries has to be picked out with something thin from the side:)

The whole thing are just made to test if it has an effect. I would think of adding a small hole to a batterypushouttool if I end up using something like this.
I have made 3 pcs for the test. They are really easy to fabricate.
I will test at the track today and will post the results later:D

The testing you are doing are really interesting. Nice job!

Rune
2010.09.30, 04:10 PM
A small test is done:
I tested 100 laps with, and 100 laps without. Testing are done on a permanent track that I can drive blindfolded, so any small change are really noticeable.

It actually made a difference in high speed corners.
The balance of the car changed. It went from neutral to a bit understeery:eek: Not much, but enough to notice.
In low speed corners it doesnt seem to have any effect.

I did not change the angle of the flap, so I will try some more tomorrow.

I have to test more before I conclude with anything. It could be the extra weight at the motormount that makes the difference, but it didnt have the feeling of added weight at the rear.

Maybe its time for Flow Viz paint on the cars :D

color01
2010.09.30, 05:29 PM
How well does the car turn when you lift off the throttle? This is usually my test for evaluating whether the effect comes from weight or downforce. When you add weight to the car, the rear end will "swing" more when you steer into a corner off-throttle, whereas if you add downforce it will swing less.

With my first rear diffuser I was getting more "swing" entering corners, which meant that it was not working properly.

Flow Viz paint would be cool but I'm sure it will be banned the very moment we put the car on the track. :p It's oily, after all, so it could ruin our track surfaces.

Rune
2010.09.30, 05:46 PM
Definetly less steering both on and off throttle in high speed corners. No added "swing" off throttle on turn in.
As I said it does not have the feel of added weight in the rear.

I cant imagine it produces a lot of downforce, but I guess reducing turbulence the air under the car can get rid of some lift.
Also: In theory the flatter floor will make the car much more sensitive to rake. Positive rake should add downforce.

I will test some more tomorrow, but the impression is that it actually works in some way.

color01
2010.09.30, 06:16 PM
Could I buy some of the 3M material from you? It looks and sounds quite promising. If we can get this underbody aero to work then we can run smaller wings for less drag and weight up high, that's a double benefit. :)

I also just tried what you said, the inner batteries on the 03 CAN be picked out with a plastic wedge! Which means that I no longer need a removable center panel and can make a permanent one like you've done.

Your results sound great Rune, keep us all posted!

Rune
2010.10.01, 10:01 AM
No problem.
Its just some small sheets that are discards from work. PM me your adress and I can send some in a envelope.

Rune

color01
2010.10.01, 12:12 PM
PM sent, thanks!

Seeing as I have the PN lower arm set, I'll have to make a 3-piece underfloor instead of just two, but I'm looking forward to trying it out!

Rune
2010.10.01, 06:58 PM
More testing done.
The flat curving on the rear part are wrong. It seems that it is a lot of turbulence there. Rubber and dirt are really building up on the 90 degree part where it wraps around the motormount. Not anywhere else.
I just followed the curve on the mount when I made them.
I am sure a lower angle will be beneficial.
http://lh4.ggpht.com/_2uRHE7AV3zs/TKZ1SIiZy2I/AAAAAAAACuA/2ERGOOcOpxg/s1024/IMG_7209.JPG

I have now tried with some different bodies. It is vital to have an opening at the back to get any effect. If the body are closed at the rear it only help with getting less traction:p
With a body that have a open rear end, e.g. the Supra without rear bumper mounted, I still feel it gives some increased traction.
It is not a very big difference but still.

Will do more testing regarding rake, and a lower angle on the rear part tomorrow.

wrcsti
2010.10.01, 07:38 PM
Being an aero nut i would say that yes they would work but nothin too noticeble. Now if you can place skirts and a small motor making a vacuum would be more efficient, might be against every rule out there but it would be better. At this scale or actually any scale a diffuser that steep would literally stall. These cars are too low to the ground to have the proper channels to feed a diffuser big enough to make a big difference, unlike the skirts and vacuum which works at every scale.
http://www.babble.com/CS/blogs/droolicious/2008/11/23-End/air_hogs_zero_gravity_micro.jpg
http://www.motorsportcollector.com/CHAPARRALPHOTOS2/2Jp2.jpeg
http://www.autosrapidos.com/superautos/b/brabham-bt46b01.jpg


Also i read your front difuser thread and was surprised by how well you describe it. Maybe you should consider something like this
http://www.fourtitude.com/news/uploads/Tradition_News/008__scaled_600_001.jpg
Obviously to a way bigger scale.

color01
2010.10.02, 02:03 AM
Well the thing here is that we know skirts and vacuum works -- all the pan car bodies (PN, ATM, etc.) work very nicely when you lower them to the minimum physically possible ride height. Cutting holes in the front of a body has been shown to hurt the handling greatly, most likely because it disrupts the low pressure zone behind the front bumper.

What we're beginning to find is that venturi effects ALSO take hold at this scale, and it's worth a noticeable amount of time (16 seconds in 5 minutes?!) and thus worth investigating more. The thing about smaller cars and slower speeds is that the diffusers theoretically will NOT stall, actually -- the boundary layer is thicker and stays better attached to surfaces.

From Rune's most recent results it seems entirely possible that the airflow is remaining attached all the way up till the vertical section of his diffuser. If that is the case then all he has to do is relax the angle of the diffuser a little bit and he'll be generating useful downforce with no flow separation at all!

wrcsti
2010.10.02, 08:50 AM
Look at how low his car is. There wouldn't be enough airflow to feed such a tall exit. My theory on the dirt is that he is getting turbulence stuck there from the body. Now if he were to use a venture on the extra space the body leaves on the sides he would get betteer results.

Rune
2010.10.02, 09:39 AM
The body is completely open at the rear, so the air passes trough without any conflicts with the rear of the body.
But of course a lot of the turbulence can be from the air passing in on the sides and the wheelwells.

The exit is way to tall, or at least to steep. Absolutely. I made a new one that has a much lesser angle at the rear. Will test out tomorrow.

color01
2010.10.02, 06:01 PM
Right, a shallower diffuser angle would probably help. Does your new diffuser have vertical fins sealing off the diffuser channel? That would minimize the effect of the moving diff and wheels, although whether or not that's good or bad is up for debate. Full scale racers have tried to use the rear wheels to pull air through the underbody.

I never asked, but what body are you testing this diffuser under? I tested the new PN pan car and I feel like front and rear diffusers would generate the downforce to really make the car come alive. I'd like to try it out. :)

Rune
2010.10.03, 03:33 PM
Supra with and without rear bumper. The floor does not work with rear bumper. Seems to make things worse. This is the body that it seems to be doing the least to. Could be because of no lexan wing. just the stock one.
350Z 2007 with rear opened. Lexan wing
GT-R 2008 with rear opened. Lexan wing

I have tried the new version with shallower angle, but not enough to have any results. Will test more and post pics tomorrow.
I have to make some kind of supports for it first. As far as I can understand, 7 degrees should be the correct angle, but up to 10 could work.

Edit: No vertical fins.

wrcsti
2010.10.03, 08:32 PM
Its not about overall angle. You just cant make it like ___|`````
It has to flow a bit more like ___%````

Also like i said before if there isnt sufficient airflow it wouldnt do much. You should add some rake to the car.

Here i drew it out. Black is floor/difuser and green is airflow.
http://img811.imageshack.us/img811/633/123qv.png

Rune
2010.10.09, 08:42 AM
It is hard to make a floor and diffusor that are service friendly (really dont want to call it a diffusor) . The flat floor makes the batteries run hotter. I have not measured by how much, but it does not seem to do anything about runtime or effect. The rear part are glued in place, but tears of by hand without leaving residue.
The material is not stiff enough for such a long flap at the rear, so it sags after some time.
I will try to make a better looking version with something else to see if I can get it to be more lasting.

To the good part. The grip seems to increase, and it does not change the balance of the car as much as the last one, as it seems to add overall grip. Will be fun to try it out with the much more effective Reflex Racing wings.

Debris are sticking to the angled rear part. i have tried to take some pictures of it, but it is not easy to see how much it is. Also there are some debris sticking to the rear of the wing.

I added a large rear wing to the Supra, and they seem to work well together.
One other thing with the Supra is that it actually feeds the floor better than the other bodys I have tried since the middle part of the front lip are raised.
http://lh4.ggpht.com/_2uRHE7AV3zs/TLBpx2PIPUI/AAAAAAAACvk/dnEAoeg1LjY/s1024/IMG_7220.JPG
http://lh5.ggpht.com/_2uRHE7AV3zs/TLBpxwDxmkI/AAAAAAAACvo/UUKf2k6lIRM/s1024/IMG_7221.JPG
http://lh6.ggpht.com/_2uRHE7AV3zs/TLBpyuFrD_I/AAAAAAAACvw/0Tz8OTIg1rM/s1024/IMG_7236.JPG
http://lh6.ggpht.com/_2uRHE7AV3zs/TLBwQO3lHRI/AAAAAAAACwM/izvzCmFQMjE/s1024/IMG_7259.JPG
http://lh4.ggpht.com/_2uRHE7AV3zs/TLBpywYY8OI/AAAAAAAACv0/vxTwdXS9WqY/s720/IMG_7242.JPG

All in all. It seems to have an effect. Maybe the underfloor is worth keeping, since that does not interfere with anything other than batterychanges. It is always fun to try out stuff to see if it has any effect. It will be interesting to see if Color gets the same results and can make something more effective.

color01
2010.10.09, 05:40 PM
I think the only change I would need to make to your diffuser is to have vertical fins at the ends to seal off a "tunnel" for the air to expand in. The way yours is right now, I could see air swirling in from the top and sides to fill in the wake behind the diffuser, which would reduce its effectiveness significantly.

As soon as I get your material in the mail I'll be trying this out -- I will glue the rear diffuser to the motor mount as well as mount the two screws in the rear of the pod, that should make it a little tougher and help keep its shape after many runs on the track. :)

In the meantime I'm still enjoying my cut-out-rear 911 GT1, there is definitely a mild "diffuser" effect resulting from the open rear and I had way more rear downforce than I really needed. While I'm waiting for your 3M material I'm working on a way to get some more front downforce -- if it proves too much then I'll be needing that rear diffuser to work. :p

Rune
2010.10.09, 08:00 PM
Its on the way Brian:)
Looking forward to hear about your results.

I have one with fins ready here. Will try to install it after the F1 qual and race.

Rune
2010.10.10, 05:17 PM
Last one for now.
The results on track are really promising.

http://lh5.ggpht.com/_2uRHE7AV3zs/TLI1Y7rLCOI/AAAAAAAACxE/P-Pk9DPmI_k/s1024/IMG_7268-1.JPG

http://lh3.ggpht.com/_2uRHE7AV3zs/TLI15kyytuI/AAAAAAAACxs/7krVnqEXi_s/s1024/IMG_7270.JPG

color01
2010.10.10, 10:50 PM
Looks great Rune! Can't wait to get mine on. How much weight does the undertray + diffuser setup add to your car and how much does your car weigh in total (w/o batteries)?

Rune
2010.10.11, 04:20 PM
Floor and diffuser weighs 1,8 grams with adhesive. The diffuser beeing the heaviest part.

As for the total weight of the chassis without batteries (complete). 96,2 grams (with new tires, ATM dish wheels and alu knuckles)

Hopefully you will get the material soon:)
http://lh5.ggpht.com/_2uRHE7AV3zs/TLI1bdtlBWI/AAAAAAAACxY/29TGqqW4sKM/s1024/IMG_7273.JPG

leonen
2010.10.13, 09:43 AM
I think the approach must include the body 100%.

I mean, each body will behave differently to aero, and for example, the flat floor should extend to the limit of the body you're using. and the diffuser not "lead any air" into the body.

Your front diffuser is great, but by leading air into the body, you're creating turbulence inside as air ends up trapped here. Punching some holes in the rear window or the back of the body might help here, as it will accelerate the air flow over the chassis and thus, "pushing" it downward.

I found out that removing taillights or having some sort of "holes" where airflow can find it's way Out of inside the body (not big holes) the performance in curves rises.

Now back to the floor, try having a "complete" version, where the only holes are for the wheels and the diff. And also that the diffuser ends up behind the body, leading air outside, to the back of your car.

Another solution I found out to be very effective, is to have small Ferrari FXX-like spoilers in the rear. Similar to the Gourney Flap, which I will try to test it out tonight.

See you!

rensuchan
2010.11.04, 12:16 PM
leonon,

Did you ever try out the small spoilers? I'm interested in the aero discussions here.

leonen
2010.11.05, 12:48 PM
Yes I have. Just Small Gourney wings over the wheels.

I specially use Atomic rear Spoilers, used downside up. I mean I remove the two stands they have and glue them upside to the body, trying to give them certain upward angle.

Try that!

color01
2010.11.05, 11:00 PM
Leonen, a bodyshell without a front diffuser would allow air into the body too, only that it's swirling around and turbulent and would increase the air pressure and create lift.

As for flat undertray vs. front diffuser, the flat undertray would be good only if driven at the rear by a rear diffuser, otherwise the air still has no gradual volume to expand into, and once it does (say, at the end of the chassis) you're going to generate a lot more drag due to the low pressure air suddenly having to slow down. Routing air into the body (front diffuser) vs. letting it stagnate inside the shell (flat undertray, sealed floor) doesn't seem any different to me, although the air pressure will change, it acts upon both the underside of the body and the top side of the chassis, and forces will cancel out. I do think, however, that if you have a method of extracting air from the body-chassis void, then a front diffuser will be better than a flat undertray since you are encouraging airflow through the chassis as opposed to trying to suck air out of a space that doesn't allow airflow.

It is a logical fallacy for me to use a full-size car analogy here, but I don't think it's entirely wrong: Modern LMP1 cars use front diffusers followed by a flat-plate floor and rear diffuser. Older racing prototypes did not, they had mostly flat plate floors. If the front diffuser didn't work, they wouldn't spend so much effort incorporating it into the design and then figuring out how to extract the air afterwards. If the air from the front diffuser can be extracted successfully, then I think there is no way that it will ever be disadvantaged vs. a flat-plate underfloor, given that with a front and rear diffuser you generate strong suction in two areas, from two air sources (front and side), vs. one generalized area from 1.5 air sources (front, a little from the sides) with a full flat undertray driven by a rear diffuser.


But all that is just theory. I wish that Rune would have more updates for us while I'm out of town on business and can't work on anything Mini-Z! :(

Rune
2010.11.06, 09:44 AM
I wish that Rune would have more updates for us while I'm out of town on business and can't work on anything Mini-Z! :(

I wrote up a small piece in my blog for a couple of weeks ago with some more pictures.
http://www.mini-znorway.com/2010/10/aerodynamics.html

I have tested a few different designs from then, and things look promising.
The most important factor is that the outlet at the rear isnt hindered in any way. The pics in the article shows how it is was when I wrote it up. Since then I have lifted the rear opening in the body until it was flush with the diffuser roof.

Rune

color01
2010.11.11, 05:17 AM
Ok, so I finally made one for myself and did some preliminary testing...

http://img97.imageshack.us/img97/8256/img0565qn.jpg

To be honest, I can't tell if the diffuser is doing anything at all. I'm able to reach nearly the top speed of my 70t motor on the linoleum, but without going to the track I still can't really discern any change between with-diffuser and without-diffuser.

Rune, I notice I am getting the same dust patterns as you are on the trailing edge of the rear diffuser -- I think this may be a bad sign that we are both getting flow separation and turbulence inside the diffuser section. Normally dust only collects when the air is swirling around, like behind the front and rear bumpers; the front diffuser on my 911 never collected any dust. I wonder if the angle of the rear diffuser is just too steep?

I will keep working on my diffuser, but I have to admit I am a little skeptical of using it vs. just making the rear wing a little taller. Thanks again for the material though, it is definitely good for making aero parts. :)

Rune
2010.11.11, 05:35 AM
Ok, so I finally made one for myself and did some preliminary testing...
Rune, I notice I am getting the same dust patterns as you are on the trailing edge of the rear diffuser -- I think this may be a bad sign that we are both getting flow separation and turbulence inside the diffuser section. Normally dust only collects when the air is swirling around, like behind the front and rear bumpers; the front diffuser on my 911 never collected any dust. I wonder if the angle of the rear diffuser is just too steep?

I will keep working on my diffuser, but I have to admit I am a little skeptical of using it vs. just making the rear wing a little taller. Thanks again for the material though, it is definitely good for making aero parts. :)

Nice observation about the turbulence.
I will try with even shallower angle to see if this can help.
The angle on the latest one pictured are the one I felt gave the biggest effect, but that could be because of other factors also.

I will test some more when I have some time.

wrcsti
2010.11.11, 02:11 PM
Ok, so I finally made one for myself and did some preliminary testing...

http://img97.imageshack.us/img97/8256/img0565qn.jpg

To be honest, I can't tell if the diffuser is doing anything at all. I'm able to reach nearly the top speed of my 70t motor on the linoleum, but without going to the track I still can't really discern any change between with-diffuser and without-diffuser.

Rune, I notice I am getting the same dust patterns as you are on the trailing edge of the rear diffuser -- I think this may be a bad sign that we are both getting flow separation and turbulence inside the diffuser section. Normally dust only collects when the air is swirling around, like behind the front and rear bumpers; the front diffuser on my 911 never collected any dust. I wonder if the angle of the rear diffuser is just too steep?

I will keep working on my diffuser, but I have to admit I am a little skeptical of using it vs. just making the rear wing a little taller. Thanks again for the material though, it is definitely good for making aero parts. :)

there can be other factors as well. For starters it is not fenced in on the sides, this lets air slip in and out at will, causing turbulence. also try and make the floor wider than the body by mm or so to keep air from moving around inside too much. those 2 things should help both of you guys. I set up a possible rig to test DF from a difuser and have all the materials to build it. minus a small rc car :rolleyes:

color01
2010.11.12, 05:49 AM
Alrighty! I reduced the angle of the diffuser as well as added two strakes to close off a channel. I opted to run the strakes a little more inboard, such that I could have a full-length strake that would not contact the diff.

http://img560.imageshack.us/img560/532/img0572y.jpg

I have some very inconclusive test results, in that before taking this picture the strakes were originally longer and extended further backwards. With the diffuser in that config, I seem to have lost significant amounts of rear grip... then I clipped off the extensions (resulting in the current pic) and I gained it all back??? :eek: I'm not sure what happened there, probably some other factor that I did not control for (temperature, etc.). In any case, the diffuser officially works now, and its effect seems to be stabilizing rather than providing outright downforce. Will test drive again tomorrow and see if I can get any better impressions.

And now a view from the underside showing off my underfloor:

http://img299.imageshack.us/img299/2613/img0571z.jpg

I wonder if there's any way to smooth out the area the T-plate occupies... it definitely looks like that could trip up the airflow and hurt the efficiency of any rear diffuser.

As far as weight is concerned, I'm in surprisingly good shape... my MR-03 weighs in at 91.7g w/ foam tires and w/o batteries; with rubber tires approximately 94.2g. The F430 is fairly light, so with that on the car is 125.2g w/ foams, ~127.6 w/ rubbers, and hence when you add 47g for batteries the running weight comes out to 172.2g w/ foams, and 174.6g w/ rubbers and dish wheels -- just under the PNWC weight limit. I definitely plan to fab a front diffuser for the F430, which will add a gram, and then save some weight through wheel choice, and bring the car to 175g exactly. Numerical example to show that all this aero modification need not come at the penalty of weight -- at least not in official racing. :) For club events who really cares if there's another MR-03 in the field running 10g underweight, lol...

color01
2010.11.12, 06:53 PM
...and I have some disappointing news to report.

I did a more systematic test of the diffuser today, first 5 minutes of testing with the central underfloor and the diffuser, then 5 minutes without the diffuser, then 5 minutes without the underfloor either.

The car feels the most stable without the central underfloor or the diffuser. :confused: At speed, there's no additional "swing" effect that would result from only adding mass, so I presume that both aero pieces (tray, diffuser) are produce a tiny bit of downforce that counteracts the mass-pendulum effect. At low speeds however, the additional "swing" from the diffuser is noticeable (slightly).

With both aero devices off, forward traction is reduced a tiny bit when accelerating from a standstill, as would be expected. As far as cornering goes, however, I felt that I could apply more mid-corner throttle when completely omitting the undertray and the diffuser altogether.

So my results are a little disappointing compared to Rune's... I doubt I will be pursuing it any further as I can just raise my rear wing a little bit to get more downforce and stability. :confused:

wrcsti
2010.11.14, 07:38 PM
and that is why i dont think a difuser would be good at this scale. Now somewhere up there in 1/10 - 1/5 it would be right on, but likely would be easier to make a ground effects car at that scale than at this.

EMU
2010.11.15, 12:39 AM
How much weight is the diffusor/undertray?

color01
2010.11.15, 02:57 AM
1.6g using Rune's adhesive-backed 3M material. If you want some let me or Rune know. I'm going to keep a bit for myself to make front diffusers and rear wings, it seems quite durable. :)

Kerk
2011.01.24, 09:20 AM
Sorry to barge in, I'd tried this on my F430.

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs796.snc4/67630_441228503650_626178650_5476679_253715_n.jpg

http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs824.snc4/68476_441228393650_626178650_5476678_320363_n.jpg

I could totally replace the lexan wing I had in the original position on the asc.
The front edge of the diffuser has about 1mm gap to the edge of the motor ATM v5 motor mount and a slight cut out to clear the ball diff. After runs, the chamber remains clean while debris accumulate all over the rear of the asc.

Regarding central under trays, why not use the teflon sheets that Kyosho sells? Sometimes just for testing, I just tape scotch tape from the belly and joins up with my diffuser completing a smooth surface to the exit. You can create temporary side skirts touching the ground with the tape too (for testing, of course) :)

Cheers!!

color01
2011.01.24, 04:34 PM
Wow, looks good! I'm surprised you say you can completely replace a lexan scoop wing -- is the difference in rear traction that drastic when installing your rear diffuser? Please take more pics, I'm interested since I couldn't get mine to work.

Thanks!

Kerk
2011.01.25, 08:57 AM
Hmmm.... Yes and No. The track I run on is not really a very big track, thus I suspect the demand for high down force might be lower than you guys? But yes, at the point of setup, I needed to remove the wing I made, in order to reinstate the balance I had prior.

Here is a pic of the wing I had. Its not a big wing to start with.
http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs739.ash1/163110_494270238650_626178650_6311072_3029637_n.jp g
http://sphotos.ak.fbcdn.net/hphotos-ak-snc6/hs042.snc6/167289_494270443650_626178650_6311076_3575475_n.jp g

Here are some other pictures of the diffuser:
There is about 1mm of clearance from the motor mount.
http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs739.ash1/163115_494271243650_626178650_6311095_8291717_n.jp g

Diffuser in the ASC. THus not a moving mass. I find that even very little load is magnified on the suspension system thus affecting handling tremendously.
http://sphotos.ak.fbcdn.net/hphotos-ak-snc6/hs001.snc6/165159_494270818650_626178650_6311083_7145594_n.jp g

BOxed the opening in the ASC with the strake extended past the lower "spoiler". Got the idea during the 2009 season of F1, with their double diffuser!
http://sphotos.ak.fbcdn.net/hphotos-ak-snc6/hs007.snc6/165763_494271098650_626178650_6311090_2386790_n.jp g

http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs764.ash1/165574_494271178650_626178650_6311092_1286948_n.jp g

By the way, here's link showing the size of our track. Myrtle Beach MiniZ racing in SC, Mini-Z Dynasty (Malaysia) and us, Atomic Collective (Singapore) are running this layout for this month.
http://mini-zracer.com/forums/showthread.php?t=35664

Cheers!!

arch2b
2011.01.25, 09:08 AM
what you've touched on and what i'd like to know more is can you discern the difference in the perfomance attributed to air flow vs. weight placement?

Kerk
2011.01.25, 09:44 AM
what you've touched on and what i'd like to know more is can you discern the difference in the perfomance attributed to air flow vs. weight placement?
Hi Arch, honestly I wasn't concern about this area. Originally, I just wanted to try out the concept, which turned into something that I could feel while driving the car.
You'd just prompted me to do a quick check. I weighed both covers. Originally all testing was done with the Red ASC. Ran the car with the home made wing but without any cut out for the rear diffuser. Diffuser was added while the hole was cut out at the same time. Ran it with both the wing and diffuser but car just understeers quite badly. On removing the rear wing, leaving the diffuser, the balance was very much similar, but rear roll was more in check while you are pushing hard around sweepers.

pictures of weight taken:
http://sphotos.ak.fbcdn.net/hphotos-ak-ash1/hs783.ash1/167358_494305133650_626178650_6311434_5696511_n.jp g
http://sphotos.ak.fbcdn.net/hphotos-ak-snc4/hs1384.snc4/163634_494305173650_626178650_6311435_964687_n.jpg

Cheers!!

color01
2011.01.25, 01:17 PM
Ah, but be careful when testing that way -- removing the rear panel of the car is known to reduce rear lift drastically. A more scientific test, if you could, is to try running your car again without the diffuser but with a 0.5-1g weight taped to the rear bumper to simulate the dead weight of a non-working diffuser. Then try again, removing the weight and installing the diffuser, and see how big the difference is. :)

Looking forward to hearing your results!

Kerk
2011.01.26, 07:12 AM
Ah, but be careful when testing that way -- removing the rear panel of the car is known to reduce rear lift drastically. A more scientific test, if you could, is to try running your car again without the diffuser but with a 0.5-1g weight taped to the rear bumper to simulate the dead weight of a non-working diffuser. Then try again, removing the weight and installing the diffuser, and see how big the difference is. :)

Looking forward to hearing your results!

I do agree that removing the rear panels removes the pressure but the diffuser here is boxed, so any air that will flow through will have to be channeled from the diffuser. Whatever air that flows over the chassis will still be trapped at the back of the asc, right? There are no other exposed openings.

Yeah, I should do the test running with and without the diffuser for an A B comparison. Will try to do that this weekend when I head down to the track. Hope to have some positives!! Fingers crossed.:D

Cheers!!

d1nzfe
2011.02.08, 09:08 AM
Here's mine. :o
https://lh5.googleusercontent.com/_8CG3vcTCIyg/TVFb-xCA3KI/AAAAAAAAAGY/nrw69qmhvac/s640/IMG_1090.JPG