Lunchie

is all this aero even legal?

NitrousBIG

You got me thinking about the legality! I did not think about the rules when building this, it is purely an experimental exercise at this point. But your question got me to see what the rules are.

These are the ones that seemed pertinent.

-Spoilers may not extend beyond the width of the body.
Not sure how this would apply to the side pods. If this would be considered a spoiler? The rules do say "Buggy and truck bodies used in ROAR-sanctioned events should resemble those used in full scale off-road and stadium racing". And I have seen some full scale off road buggies that have in-closed nerf bars that aid in aerodynamics. So using that logic the side pods should be legal? But I don't think anyone has tried this before.

-Where permitted, add-on spoiler material must be securely fastened to the
body.
I think this makes the window extensions legal. And they are narrower than the rear pods.

-Off-road wings may be mounted using wire or fastened directly to the
chassis. There is no minimum clearance for off-road wings. Front wings are
allowed if utilized on the body's full-scale counterpart. If allowed, front wing
dimensions are specified in the class rules.

-Front wing max width 127mm, mine 91mm. So.... That's legal.

-As for the rear diffuser. There doesn't seem to be a rule. Guess that means it legal.

-I wasn't able to find anything about the rear arm mud guard/wings. The rules just state that wings must be fastened to the car. There is nothing that says you can't have multiple wings, if these are classified as wings?

So.... Is it legal? As far as I can tell yes. But buggy aero continues to evolve so at some point ROAR will limit it I am sure. The rules are so wide open at this point I encourage people to test thing and see what works. Even if it is illegal. That might spur on an idea that might be legal. If nothing else it should make racing more interesting, I get sick of everyone's car looking the same. That's why I have ordered parts to start a new carpet car.

NitrousBIG

Well... Its been a while and with snow coming down and time off around Christmas I took some time to take some pics and update the cars development.





Yuck!!

Carpet season is in full swing and they had the track open over Christmas. So I took the 22 there no knowing what to expect with over a 68% rear weight bias and really soft off-road suspension. But I was really surprised at how well it worked.












I installed the Spektrum 7050 and wired the positive lead straight to the battery. It worked at home then fried upon arrival at the track. Ordered a new one and phoned Horizon Hobbies to clarify the wiring of the servo straight to 7.4v. They said both positive and negative have to be wired to straight to the battery. I did that and it did the same thing, it fried! So I threw my good old 6070 in and finally that worked (not to 7.4v).

Once everything was running I broke the front wing off in a crash and kept driving but I didn't notice a difference. Confused I made a bigger wing (from 90mm to about 120mm) tried different angles and still couldn't feel a significant difference. There is some kind of aero voodoo happening........ I think I need a wind tunnel now!











It was interesting running this car on carpet. I learned a lot! I was pleasantly surprised at how well it did handle. The centralised mass DEFINITELY works and makes the car very responsive and easy to drive.

The four gear tranny does not work on carpet but I think it will work not to bad once some of the other handling gremlins are worked out.

I learned a ton about ackerman and the affects of bell cranks, drag links and what a forward facing and rear facing bell crank does.

Once I got comfortable with the car I started giving the car more steering and started to notice some design flaws. My current design gives the car a little more total ackerman than the factory system due to the nature of the movement of the single bell crank. The way this linkage setup works the ackerman increases exponentially as you steer (unlike the original 22 slider, which would give linear ackerman gain). So, as a result, when I dialed in more front traction the car became very twitchy around center and then had less steering at full lock.

I was very dissapointed at the time until I put all of this together. After some sketching and working things out in my head my current theory goes as follows. A forward facing bell crank (like in my car) will be sensative around center and less so at lock. Adding a second bell crank and a drag link will lessen this affect. Then something like a slider will give neutral steering progression.

Switching to a rear facing bell crank will have the opposite affect to what I have now. In theory this will create steering that is docile around center and progressively more aggressive toward lock. And once again the dual bell crank with drag link offering a middle ground.

So with that "spectacular realisation" I began working on new front end geometry on the second 2wd buggy I referred to in an earlier post. Not knowing if I could make the design work and not currently having a working CAD program (working on getting Solidworks educators edition) I started mocking things up last night in cardboard. I need to make some aluminium posts for the new bell crank setup to complete this prototyping stage. So, instead of stopping I started playing with some of my ideas to further lower the cg and centralise the mass further. The blocks on the back of the upper bulkhead are the new shock towers that place the would be shock towers inside the cab instead of out front disturbing air flow. This is just an idea I am throwing around and checking the ideas feasibility, its looking good so far but the idea will require further prototyping and mock up. One point about this I do want to clarify that I am NOT changing any geometry with this experiment just relocating the shocks. My only concern is additional binding this may cause.





The final sketchs that lead to prototyping. The new bell crank design should put the pivots VERY close to factory 3.0 pivots.



I think that's all for now. I'll try to post more frequently as my theories develop.

NitrousBIG

Almost forgot I got some video of the car running on the track.

https://www.youtube.com/watch?v=WFGEsja54S0

https://www.youtube.com/watch?v=X6cOFWbb-L8

https://www.youtube.com/watch?v=uSl3AIcd1ZE

Not bad for a car setup for medium traction off road IMO.
Not my best driving but..... Well that's it for excuses!

NitrousBIG

Well its snowing again. WTF this is the worst winter I can remember.

Anyways, couldn't got to the track so after looking into the different CAD programs my brother suggested Autodesk Inventor. As an teacher I can get a free version. So I am testing it out for the school. My co-worker just ordered a 3D printer, can't weight to start playing with that!

Anyways started messing with it and this is what I've got so far.



Bell crank is at full lock.... Can't figure out how to fix that?

NitrousBIG

Started trying to design the front arms.... I suck at Inventor! But you can see some progress. I am really trying to achieve an organic design that works to aid in my aero goals. I did this one as a dual plane wing and I'm thinking about trying a single plane. I need to build some and do some wind tunnel testing. Or try to get the wind tunnel testing in Inventor working.



That's all for now.

radek

Enjoy seeing these kind of projects, yours goes where the bigger manufacturers don't. And also a bit all over the place. In a good way

Keep it up!

I reduced ackerman considerably by moving the bellcrank ballstud 3mm further forward. For carpet I just find that better. This required moving shocks slightly further forward. And by mounting bellcranks uppside down, got rid of that horrible bumpsteer the 22 gets at an 18mm ride height. Both tweaks just a matter of personal Preference.

NitrousBIG

Thanks! I am doing most of this just to learn. And I appreciate the added info you gave. Acherman is something I have never really played with and I have jumped into the deep end! What I also find interesting is how things interact with one another. You mentioned that you are running at 18mm (about where I am at) and this just made me realise how lower ride height = less weight transfer therefore less aggressive steering when cornering hard (read higher steering angles). Now you got me thinking about less kick up to encourage weight transfer. How would this play into things????

Now I'm confused at a higher level!

radek

Wish I knew

Tried the 20 degree pivot in the hopes of more entry steering. Found it made steering more nervous around center, but decreased it overall. So switched back to a 25. This test didn't really say anything as I should have taken the time to change rollcenter/shock package as well, to really evaluate the 20 kick.

Lot's happening in the carpet racing scene. And I don't envy car manufacturers trying to keep up with it all. Fact that the cars still look so different tells me there is still a long way to go. Compare kf2 outdrive angle to any other car at carpet ride height and top drivers loading their newly designed carpet specific B6 cars with brass bulkheads and steel weights up front, even though it destroys any weight centralization.

Interesting times ahead.

NitrousBIG

I was updating my other build threads and thought I would include an set of links so here goes


A pic of all my recent projects ready to go to the track.



Project XX-24



Link http://www.rctech.net/forum/electric...l#post14801863

Really proud of this:
http://site.petitrc.com/setup/losi/s...ith22FrontEnd/


Project SCTE [Light Weight and Aero]



Link http://www.rctech.net/forum/electric...l#post14801802


Project 22-4



Link http://www.rctech.net/forum/electric...l#post14801838


Theory Build



Link http://www.rctech.net/forum/nitro-of...ory-build.html


I also picked up a truck, camper and boat. The boat has a build thread as well.



Link http://www.themalibucrew.com/index.p...ifornia-skier/

That's all for now. Enjoy!

taylorsizemore

iTrader: (5)

I love these projects! Thanks for sharing your process, I'd love to work on something like this someday. Enough other projects for me though.

I wanted to mention Autodesk Fusion 360, I use it nearly every day at work and really love it. It's free for educators and students too.

Good luck and keep sharing!

NitrousBIG

This guy posted this on youtube and my response might clarify what I'm doing for those of you who may not have read my thread from the beginning.

Posted in the comments on You Tube
Ok, so here is the feedback you are not going to want to hear.
First off, you are not a good or consistent enough driver to truly push a car to the point where you can see/feel real shortcomings. Basically, because you are driving the car wrong, it seems to you that the car is wrong, but it is your driving that is causing some of your issues.
Second, your "aero" work is laughable at best. Off-road rc cars don't travel at high enough speeds for significant gains to be made with aero. Also, aero is all about controlling the air, and most of your "upgrades" do nothing because the air is dirty, and way too low energy to really do anything significant.
RC cars rely almost entirely mechanical grip. You have done a bunch of stuff to remove weight, and centralize mass, but you fail to understand that removing too much weight from the chassis alone throws off the sprung to unsprung weight ratio.
You have the ability to make one off parts because you are a shop teacher. Yet your lack of understanding of vehicle dynamics, and driving ability make for a development path of your "upgrades" which are going to yield very little tangible improvements. Go ahead and find the fastest driver at your track, and have him take a couple laps with your 2wd buggy. I guarantee the good driver is going to think your car is really difficult to drive fast.
You can trust I know what I'm talking about. I have been racing rc cars for 25+ years, and I am a mechanical engineer, with a focus on vehicle dynamics.


My Response
Just wanted to respond to Jules....

I've been racing since 1986 so that's 31 years and a few years ago I qualified 2nd in the open class at the Cactus Classic.

I have run the popular (normal) setups and won many races but I wanted to further my understanding of vehicle design. Plus, what I'm doing is fun.

This was a practice day where I was learning the track. Plus the car is setup for dirt with a 67% weight bias, I was just doing some testing and experimenting.

I am aware of vehicle set-up through years of racing with team drivers and have a growing understanding of vehicle dynamics / engineering through tuning and building other projects.

You seemed to have missed the whole point of this project! The car has been developed to reduce the polar moment of mass on a low grip clay track, not to make the car super light. The weight was just a side effect of the test. And I made changes to geometry to further reduce the polar mass to see if the gain was worth the loss. Thus resulting in my further understanding of ackerman change due to bell crank geometry.

Your comment about offroad aerodynamics not offering significant gains..... Have you ever run a 2wd buggy without a wing? Have you played with cab forward bodies? Front wings being developed by manufactures? Nobody is looking at air management, just downforce. My tests have lead me to start developing some air management in the buggy I am currently building.

Did you take a close look at what I have done with removing the middle of the front shock tower to get more clean air to the front window and the window canards which significantly improved steering at high speed. I am aware that the side pods aren't doing much, but they offer protection for the esc which is moved on the new car I am building due to testing this new idea.

As for the arm covers they do make a difference at high speed. Tested back to back I felt a difference. Yes I am aware that it is dealing with dirty air and that they have sharp angles where the air would delaminate and "stall" reducing the downforce produced. Again I said this is a test and the test yielded significant enough results to warrant further development. I think that what your missing is that it is probably picking up cleanish air down near the tack and picking it up over the arm. I am planning to build a mind tunnel and vacuum former with a couple of students that will allow for better designs.

I am aware that the rear diffuser is doing little to nothing since there is no floor on the car and offroad cars are too high for any ground effect. It was an idea that didn't work but gave me more ideas to test.

Through my testing and experimenting I have found that the front wing is doing little to nothing and have come up with other things I want to test as a result of what I have learned.

As for the correlation of vehicle weight and unsprung weight I am fully aware of the theory and plan to maintain the ratio in the new car I am building.

So in closing I am aware that the car handles poorly..... It was never meant to work on carpet but my new car isn't done yet so I went out to test some stuff. Just like the manufactures do. I was at the Ready race a number of years ago when Gil Losi and Brian Kinwald were testing a prototype of the XXX-S. I found out later from Gil that it was one of the first times out with the car and they were there to develop concept and learn. Sound familiar?

So yes to put an answer to your statement of my lack of knowledge YES I could go faster copying setups from the fast guys. I have done that. I wanted a new challenge and wanted to explore new ideas. And yes I have a ton to learn but I have learned a ton from doing and trying things that didn't work, as an educator I believe that is the best way to learn. Also I don't have all of the time, resources and knowledge to design and build all of my ideas to life to find out that they don't work so I have to take small steps and develop ideas simply over time.

You would have to take a look at my other project and read about what I am trying to do to realise that everything you said is true but you completely missed the purpose of what I am doing. And that I DO know what I am doing! People need to learn to test things trough testing to develop their cars setups and actually learn about vehicle dynamics, aerodynamics etc. and not try to simply re-regurgitate what everyone else is doing.

So thanks for the advice but I'm good.


Enjoy!

NitrousBIG

Well Photobucket has screwed me over with this and all of my other threads! And I just wanted to say that their decision and the poor way in which they have exicuted it has affected the learning of my students and I am sure the learning of kids all over the world. People are no longer able to learn from many others who have shared their knowledge through the use of Photobucket.

I will work to restore the pictures and continue sharing the evolution of my projects and document my learning.

Here is a screen shot of a test I was trying in Fusion 360. I am working on the idea of 3D printing some aerodynamic arms for the new 2wd I am working on. I have been struggling with the concept and wasn't sure how I was going to model them but I think I have figured it out and now I have to design and build the model to scale. Remember this was JUST A TEST it is not to scale! But I think you can get an idea of what I'm going for.




I've also been talking to one of my former students about building a wind tunnel in my shop this winter. The tunnel would be for RC cars (we vacuum form parts and bodies in my class), testing wings for a tethered electric plane project, and just learning about aerodynamics. This would be cool for checking to see if my ideas are working and why things like my front wing made no difference.

mx836

iTrader: (15)

I'm really bummed about the pictures disappearing in your threads. This type of stuff is right up my alley and after discovering all your awesome threads, I'm sad that I can only read about it.

PS, that link didn't work for me.

NitrousBIG

I worked on Fusion 360 for around 4 hours and I think I've got the arm designed for a 3D Printing test. I might play with it and refine it a little more. Eventually I would like to print this (if it works) out of Nylon/Carbon filament.




Front view, I still have to put in the shock and pivot holes.


This is the outside of the arm. I'm going to try to put the notch in it for the rear carrier.


The inside of the arm. I made a relief for the out-drive, it should clear.