Just the front, rear really dont need it especially with the weight transfer.

Hey did you happen to Catch last nights episode of the "Mythbusters". It was about aerodynamics and creating less drag on a car with the addition of dimples. (IE. Like a Golfball) they were able to prove a 12% gain in gas mileage just by adding dimples across the entire car. They were using the science of a dimpled golfball will fly farther than a non-dimpeled using the same amount of thrust. (which is about 40%)

After reading through your thread last night I watched the epsidoe and thought that I would pass this info along. As I thought this might help you out with your goal. Wind is going to contribute in a huge way and every little bit would count when trying to break a new record. You should check it out. It may just give you that little bit extra of an edge over the comp. if you were to design the body correctly. Anyhow Good Luck. :smile:

Cool! I will see if its on hulu and watch it. Question is how am i going to dimple my body? Maybe a soldergun with a proper tip IDK.

Great episode, 9% increase was amazing !

Heat gun and some sort of tool with the correct diameter ends.
Like this ?

http://dsc.discovery.com/videos/myth...-vs-clean-car/

Checkout Dirty Vs Clear Car High Speed 3

Good shot of the car

I was thinking Really thick Lexan ( Maybe .060 [or thicker] and a Countersink) :lol: Oh and a couple spare hours of time...

maybe you could try to make the underside of the chassis as flat as possible, creating less drag for air under the chassis. if you can speed-up the air flowing under the chassis, the difference with airspeed flowing over the body is minimized, resulting in less lift.

edit:
some additional info

Quote:

Even with these limitations, the underbody is of major importance in the aerodynamic setup of the car. This is particularly true on the speedway circuits. In order to achieve an efficient setup, the front and rear wings are much smaller than on a road or street setup. The frontal area of the car is reduced in size so it can slice through the air, in an effort to reduce the drag coefficient. The front wings are not used for downforce on the speedway setup, but rather as a trimming device. The major downforce comes from the chassis and underbody design. The rear wings are also much different in appearance on the speedway setup. Instead of the standard wing or high downforce wing used on the road and street setup, the rear wing is almost horizontal with smaller endplates. The speedway rear wing is shaped to create less downforce and reduce drag. The optimum setup on the speedway is to create enough downforce on the cars so when they reach the corners they can run flat out. Drag reduction is more important than downforce on the speedway setup. The best setup would be an adjustable wing to reduce drag on the straights, but supply downforce in the corners. CART regulations, however, prohibit this type of setup for safety reasons.

found here: http://www.nas.nasa.gov/About/Educat...r/chassis.html

or, add a fan at the rear of the chassis: http://www.autoevolution.com/news/gr...17.html#image2

You can see Nic Case used that concept in quite an elaborate way

http://i257.photobucket.com/albums/h...e/DSC03517.jpg



NASA is a great site, you can spend days in there!

Its fairly flat on the bottom other than the holes cut in the lower plate for the older battery cells the and the front has a slight kick up for adding more caster or camber (what ever its called) . see pic

http://i153.photobucket.com/albums/s...s/CIMG2579.jpg

I plan on using clear packing tape over the bottom holes too smooth them out.

I lengthened the chassis again this time with a mono block and I am using the long hardcore titanium skid for a wheel base of ~15 inches Hopfully to get more high speed stability. I was going to order a custom shaft from rc alloys but found out the savage xk rear shaft might work perfect. I started trimming the slipstream body up figuring out I should of left some of the plastic on thats supposed to be trimmed off. I figure out I screwed it up for the best setup for high speed. So it is going to be used for my g4 maxx now . So I started trimming the Jconcept body up to the best of my ability. I know some of you dont like the looks of it and I am kinda partial to the slipstream body also but this body looks like it would be better for the build after I mounted it. At least until I get another slipsteam I need to move forward. Understand I still need to trim the bottom up but I am planning on running a thin lexan sheet on the hole bottom of the truck to help with reducing drag on the bottom. I left the front of the body long also because I plan on running a front wing off a 16th scale ofna model that matches the rear wing almost perfect but alot smaller.

The front wing still needs to be mounted up.
http://i153.photobucket.com/albums/s...s/CIMG2649.jpg

Does it remind you of somthing ? Not exactly but you guys know what I'm trying to do .
http://i153.photobucket.com/albums/s..._1-470x352.jpg

http://i153.photobucket.com/albums/s...s/CIMG2650.jpg

http://i153.photobucket.com/albums/s...s/CIMG2651.jpg

Notice the esc is sticking out of the body because the body sits so low. It will still be protected by the roof and the wing. It couldnt of worked out better because it is perfect for keeping the esc the absolute coolest and easy access to the switch. right on top.

http://i153.photobucket.com/albums/s...s/CIMG2652.jpg

hmmmm....maybe you could have just left that horozontal piece of lexan on the front of the body instead of trimming it off - could have been your front splitter built in for free!

But in all honesty - I think to reduce drag, that front wing needs to extend to outside of the wheels so that it can open a pocket of air for the wheels to pass through.....I think......

There was no horizontal peice in the front of the body. I know what your thinking but I still have to trim the front of the body so the suspension will work. As it is now it is sitting on the ground holding the truck up. The wing is for more frontal down force and too help the air sweep up and over the hood of the body. I am hoping the front wing with vertical stabilizers help the truck track straight at high speed. Just an Idea and I am going to test it out. I am going to order another sliptream body and see if I can refine it.

From goofing around with my jato I would say to try and find a wing that almost looks like a scoop..

http://www.rccna.com/photopost531/da...um/jato002.jpg

this little wing came in handy when I pit a RB 523 in the jato, car became alot more stable at speeds with noticeable less tire wear.

Cool ! I am going to try it with and without. Not to get off subject but how did you like that rb 523? I have one for my sons predator t-maxx I heard its a ripping fast engine. I havent had a chance to try it out yet.

http://www.f1technical.net/articles/...frontwing3.gif

I think the simple shape of the MT body needs a simple shape for the front splitter. You may be able to make a wider splitter that is able to direct the air flow outside the wheels but I would have thought a wider version is ultimately more drag?

I can see a simpler shape even from that wing, if you ignore the body/nose & connect the existing radius...it does resemble the more rounded RC body

it was absolute over kill but was fun as hell :) strong motor so pushing big gearing wasn't a problem.

Good news! I got a hpi savage xl dogbone and it fits perfect. It only cost >$11 shiped in > 1 day. Beats paying $26 for a custom one that wont show until end of the week. Couldnt of worked out more perfect. Just need to make an adaptor plate for the top. I am going to lock the front dif tonight with bad horsie diff locking grease. It is the thickest stickiest grease I have ever seen and I am told it will lock the diff up like a posi.

I did the front diff with the bad horsie difflock but not sure if its going to work. It is a hole lot tighter but it will still differentiate. Definatly not locked. I made my adaptor plate out of some 2.5 mm carbon fiber and a peice of billet plate. Turned out nice but I might cut the spacer down to keep the weight down.
I am also having second thoughts about running the jconcepts body because of the flat not so aerodynamic nose. It does have alot lower roof line than the slipstream though so I really dont know if it would make a difference. I went ahead and ordered another slipstream, maybe I can make the new one work better. I think the front wing design is out though unless I need some front down force which I think the body should take care of anyway. Here a pic of the carbon fiber adaptor plate I made. The billet spacer underneath is needed because the monoblock is pretty thick. The carbon fiber peice will make a good place for the gyro to go when it shows up.
http://i153.photobucket.com/albums/s...s/CIMG2653.jpg

Same distance
 

[QUOTE=Rivermaxx;329980]I did the front diff with the bad horsie difflock but not sure if its going to work. It is a hole lot tighter but it will still differentiate. Definatly not locked. I made my adaptor plate out of some 2.5 mm carbon fiber and a peice of billet plate. Turned out nice but I might cut the spacer down to keep the weight down.
I am also having second thoughts about running the jconcepts body because of the flat not so aerodynamic nose. It does have alot lower roof line than the slipstream though so I really dont know if it would make a difference. I went ahead and ordered another slipstream, maybe I can make the new one work better. I think the front wing design is out though unless I need some front down force which I think the body should take care of anyway. Here a pic of the carbon fiber adaptor plate I made. The billet spacer underneath is needed because the monoblock is pretty thick. The carbon fiber peice will make a good place for the gyro to go when it shows up.


It looks good River. Your extra spacer looks very much like what I have setup on my high speed project, only with a double monoblock instead. With the double monoblock setup it is extremely strong and quite easy to modify in order to make them match up together. It looks nice so far River. I think the front wing design is still a good bet in order to avoid liftoff on the front end. If you do go over 100mph it will try to lift up on you because you have a lot of air space under your chassis.

I really like that other high speed rig shown earlier, because he even designed a kind of vane system into the underside of his chassis shield to deflect air that does get under the vehicle off to each side, which reduced the airflow going all the way to the rear of the vehicel. Ultimately reducing the chance of liftoff.

Like I mentioned before you may want to look at the other examples of 1:1 vehicles in both funny car and F-1 racing. Even for a 1:1 vehicle they keep the chassis just a fraction of an inch from the ground, and still add wind deflectors to keep the front end on the ground. 100mph airflow will lift anything up that gets in its way as long as it can get underneath the object in question. Just an opinion, and I love the work your doing. Good luck River.

Yea. I think I am going to change it again its too busy and I can make it alot nicer and simpler. The addition of the mono block and the adaptor and billet block added alot of weight I dont want. So I am going to make a new one peice carbon fiber plate for the top and something for the bottom skid.
Jerry if you look at the pic you can see there is about 1/4 of an inch of space between the body and the ground. I need some space because the suspension does travel some. As it is it should work out fine and the front of the body and windshield should provide the necesary downforce needed. If not I will add the wing or a splitter of some sort.
http://i153.photobucket.com/albums/s...x/CIMG2655.jpg

Better.
 

It looks better and better as you go RiverMaxx. Your suspension should be setup for hardly any travel at all considering that you are doing straight shot speed runs on somewhat smooth surfaces with it. The other thing that comes to mind is that you want to have enough weight in this vehicle to keep it from floating up on you. You also need weight for the vehicle to carry some momentum as it travels down the course against the head winds, wich will help reduce the strain on your powerplant keeping everything cool. If it is too lite nothing will keep it from flying away once it hits the head-wind at 100mph. The weight needs to be proportional to the size of the scale. Having a lite weight vehicle is great for handling if you are racing on a dirt course, but for speed runs on a drag strip environment you really need some weight to keep it on the ground.

Just trying to share some thinking with you wheather you agree with me or not. I would really like to see you hit some serious speeds with this project, which will be a great example for myself and others to follow. I hope to do the same thing at some point. I think going over 100mph should be easy if you setup your build right. Surviving the run will be the real challenge, and having to repeat the same speed or better for certification is another thing all together. You have to be able to do two identical passes to qualify the record.

The suspension has < 1/2 the travel of a stock maxx with the revo shocks which I think is pretty good considering its supposed to be a monster truck . The truck as it sits right now is > 10#'s and I'd like to get it right at or under 10#'s. Most of the weight is moved towards the front and under acceleration some of the weight should tranfer towards the back. As far as the truck lifting off I really dont think that will be a problem. The weight moved forward, sloping front hood and the low cog should keep it on the ground. Most of the videos I have seen with lift off or wheelies are small 3# cars and big tall high cog MT. If you watch OverrevOs video he didnt have any problem with lift off @ 70-91.2 mph.
Keep the ideas coming I appreciate them as my brain is on overload trying to figure out how to do this thing right any I deas are taken into cosideration. I personally dont think I will hit a 100mph but having that goal is something to strive for. As for the record I think you have to have 2 passes withen 5% of each other for the record. Understand I am competing in electric open wheel class which means buggies, truggies,MT's and no limit on voltage. Current official ISC record for open wheel is like 58mph, which I could probably do backwards LOL. The old (Not a class anymore because of lack of participents) current official top speed record for MT is 72 mph which was a wheely king. Fastest official E-maxx is like ~70 mph. I already hit 67mph about 1/2 throttle and letting off my first time out with the good foam tires. I see no problem beating that as long as I can get the truck to go straight. If I hit 80mph I will be happy as hell! How many MT's or emaxxes have you seen do that. Not many, and definatly no e-maxx. Its easy to make a onroad car go fast but making a vehicle designed for offroad go fast is definatly a challenge.

I agree you need some weight to keep the wheels pointing down but the aero setup is IMO the critical issue. If you consider a 1/10 TC can (relatively easily) achieve 100mph weighing less than half of what a 1/8 off road vehicle can, I don't see a direct relationship between scale/weight/speed. Also weight impacts acceleration directly, you will still reach the same terminal velocity with added weight...it'll just take longer to get there. In my experience range is a major factor in any speed run, once you get over 800ft even a 1/8 starts getting small, over 1000ft is quite challenging...1200ft a 1/8 looks like a non descript blob

I think you're confused about the 2 pass theory. A single pass that is correctly measured (ISC use optical timing traps with backup device) is all that's required for an official or unofficial record

http://rc-isc.com/ISC%20Rules/ISC%20Rules%2009.pdf

Go to page 8...

Will this event have two devices? If so we dont have to back it up with a second pass. That cool! As far as range is concerned I am a bit near sighted so @ 1000ft is probably my limit. Hopefully thats all I need.

This is an awesome build. I dont know how missed this thread. Good work Rivermaxx!

Well I went out and tested again today and got the truck to track alot straighter and easier to control. Got it up to 76mph and then the composite slipper shoes flew out and I dont know where they went. I either burned them up because of slipping or they couldnt handle centrifical force. Anyone know of a fix for this? Is this the unofficially fastest emaxx now? I dont know of one that is faster. I dont have video but next time out I will get some doing 80 mph passes. I still have some higher gears to use but not sure when the slipper started going away. So it might go faster the way it is.

Ditch the slipper completely - for what you are doing, its wasted energy.

Very exciting speed! I've never heard of a faster Maxx. Yeah I'd find a way to ditch the slipper or lock it. (Hurry up Mike! lol kinda depressing)

Edit: Maybe you should get a Strobe slipper. I was thinking that you had one.

Thats the plan I need to get a oomp slipper eliminator.


I am sure the strobe would work flawless but the gears are very limited. I wont be able to gear as high as I am with a strobe. Just wait this maxx is going to break 80 mph next time out.

Way to go River, that's pretty quick!!

I agree on negating the slipper...same thing happened on my Rustler until I locked it tight & added a second lock nut

Too bad.
 

Its too bad MonsterMike does not have the Maxx center diff mount out yet. You would be better off with just a center diff and no tranny to worry about. Then you just wind it up and watch it fly.

Yea I know! It definatly would be good advertising for him @ this event. I have sent him a few emails about it and recieved no reply. I am pretty sure he was involved with the last emaxx that went to this isc event that placed second to the hpi wheelie king's 72 mph. I allready got both those trucks unofficially beat. I didnt even cut the high down force wing yet or use my more aerodynamic body yet. I planed on taking my 30' fifthwheel to the event as it would be a good back ground for a good size RCM banner.

As far as my trans I probably allready covered this but its a g1 single speed gorillamaxx tranny with a UE idler gear and stock plastic drive gear inside. I put a modified revo input shaft in it so I can run the smaller revo mod 1 spur gears that provide a taller gear ratio when combined to the limited pinion gear sizes availiable. I changed all the bearings out with ceramic avid bearings and shimed it perfect as I figured the added cost would be needed because its taking all the power. I was using a 25t hpi hardened gear but found the hot bodies gears on amain to be alot lighter & milled out and also go up to 26t mod 1. I am using a 42 tooth hot racing gear that seems to be working good as it is hardened also. My biggest issue right now is the slipper clucth need to be replaced with a slipper eliminator made by oomp from the traxxas forum.(still trying to get ahold of him and I hope he still makes them) I wish my neu motor had no fins though so I could have more adjustment but I might have to trim a few of them down a little. A nice mount off the front of the tranny would be nice to center the engine and allow more gear adjustment. But I dont have time to get into that right now because the event is two weeks away an I at least want to hit 80 before it comes.

Yea but I want to do away with the slipper pads all together. I have to lock it down anyway. That set up is good for somebody who wants slip. I want no slip at all.

What about using a composite (single) slipper pad & through bolting the 3 elements?

Thats another option but I really want the slipper eliminator kit.

I got ahold of oomp form the traxxas forum and got the last slipper eliminator he has. I was worried for awhile there. I did put int the t-maxx disc brake and with a little work it did fit on the pad holder. I put it on and it seems to work good trying to turn it by hand its locked up.

do you have pic of that eliminator kit

Do a search on traxxas website it will turn up I am sure. pretty basic but I cant make it with out a good lathe with a 4 jaw chuck. actually here you go:
http://i153.photobucket.com/albums/s...PLATEFRONT.jpg
http://i153.photobucket.com/albums/s...RPLATEGEAR.jpg
http://i153.photobucket.com/albums/s...RPLATEREAR.jpg

just drill through the back slipper plate, tap for m3 or 4 and bolt the whole assembly together

Too late now I have one coming. I prefer precision over jimmy rig anyday.