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Thread: MPH Challenge

  1. #41
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    Kenny said it...if you split the air you must try to put it back together. You'll need the wing if the rear end is going to be blunt like that.
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  2. #42
    RC Turnbuckle Jr. 08kgraves's Avatar
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    yeah if you ever look at anything used for like world speed records they typically all have a teardrop design
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  3. #43
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    no problem just let me know dad

  4. #44
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    Yesterday I got a load of firewood and after stacking it in the garage I got out the leaf blower to clean up the mess. While blowing out the bark and debris something Double G said popped into my head, a Wind tunnel.

    I tied a string to the rig and attached the other end to a digital fish scale and the other end of the scale anchored to a wall. I blocked the leaf blower in place to keep it from moving and positioned it about 3 feet in front of the rig. Instant Red Neck Wind Tunnel (without the tunnel)

    Itís not very scientific and there is a lot of turbulence but the numbers I got were pretty interesting and amusing.

    Without a body and just the rear wing the scale was being pulled 2.6 lbs on the average. With that simple body I made and the wing the scale was being pulled 1.2 lbs on average.
    Thatís more than Ĺ less of the initial drag with a body than without a body

    I then put my scale under the rig and set the tare to 0.
    No body and wing = 1.8 lbs of down force.
    Wing and body = 2.6 lbs of down force.
    +.8 lbs of down force with the body
    If I watch closely I can see the rear springs/shocks being compressed a little more with the body than without.

    Iím going to make a couple different body styles and experiment a little more just to see what kind of numbers I can come up with.
    Maybe Iíll add a second leaf blower and get an anemometer (I think we have one at the office thatís never used anymore )
    No slipper/tall gearing/power = broken parts.

  5. #45
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    Quote Originally Posted by Snook Man View Post
    Instant Red Neck Wind Tunnel (without the tunnel)
    WHY am I NOT surprised? loll NOw you need to find the balence between increased downforce and increased drag.

    +1 Most speed record body styles seem to be closed wheel, very low to the ground avoiding air under the chassis and as little downforce as possible but have stability.... I'm anxious to see this develop Snook..

    Winter Projects? OH yeah, you get that stuff called snow?... Best way to avoid that... SoFla baby!!! RC's Year Round!!!!!

    I was wondering your reasoning for having the engine reversed on the chassis? Is this due to the tranny?
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  6. #46
    RC Turnbuckle Jr. Snook Man's Avatar
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    Yep, with the tranny output shaft centered with the diff pinion and mounted on top of the chassis it was easier to just flip the tranny with the spur in front. That way I donít have to be bothered with the engine being in the way of the center shaft, and the COG will be more toward the center of the chassis.

    Unlike a Top fuel dragster I will only need enough down force to keep the rig from trying to take flight I donít think the engine will be strong enough to worry about spinning the tires with the gearing thatís needed. Iím just trying to hit 100mph, Iím not worried at all about the ET (for now).

    I made a mockup body for the rear and the drag was reduced to 11oz on average. Some down force was lost with the rear body on also. From what Iíve read, when the wing cannot see the ground unimpeded (with the body tucked up under it) down force will always be lost.
    I also mounted a pair of old chevrons on the rear to see what happenedÖBig difference, almost 2 lbs more drag than with the narrow buggy tires.

    I will probably make a body to cover the front wheels up and see what happens but with the width of the Maxx rear suspension enclosing them would probably be too much drag.

    Like you said, I will just have to play with it to find a good balance between the down force and drag with a scale this small.
    Iíd like to at least get close on the 1st try



    And I do miss the warmth of SW FloridaÖ
    No slipper/tall gearing/power = broken parts.

  7. #47
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    very interesting build. Have you decided on an engine yet?

  8. #48
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    Better tires but I'm not sure if they'll let you hit three digits haha, just kidding man.
    It's coming together, but do you think you might want to lower the stance in the back?




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  9. #49
    RC Turnbuckle Jr. 08kgraves's Avatar
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    i agree, you want it sitting much lower in the rear.
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  10. #50
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    Quote Originally Posted by Snook Man View Post
    I will probably make a body to cover the front wheels up and see what happens but with the width of the Maxx rear suspension enclosing them would probably be too much drag.
    Most top speed runners do cover the wheels, not as much for the drag but the increased resistance on the wheel from the turbulence of the air at high speeds. Less work for the engine to turn the wheels.....

    So it may not affect the drag much but it will help cut down the wheel turbulence which will give you more driveline efficiency....

    Have a look at any land speed record vehicle built after the 60's, even RC speed record vehicles... The wheels,,,, they are covered....

    But there is a clss of speed record vehicles for open wheeled vehicles. Just an FYI.

    Here's a post from over on UE, I know it's electric, but it has some very good ideas and info....
    Robin Williams
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  11. #51
    RC Turnbuckle Jr. Snook Man's Avatar
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    Squat the suspension/chassis or the body?
    The chassis is only approx Ĺ inch off the ground in the rear and about ľ inch in the front
    Lower front + a higher rear creates some down force, remember, it’s a pan chassis with the rear bulkheads & diff mounted on top of it. I will probably have to use limiters inside the shocks to keep the down force from compressing the suspension too much and causing the chassis to bottom out and to keep the rear a little higher than the front at full compression. I can already see the rear squat with just a leaf blower.
    The rear of the body is sitting on top of the shock tower and I can not go any lower with it unless I expose some of the tower.
    I won’t be able to set the ride height until I get the rear wheel/tires, they will be slightly taller and narrower then the chevrons.


    As for the engine I will use, I have something up my sleeve

    I’ve read that post a few times already Rob , That’s most likely the wheels and tires I will be using on the rear.
    No slipper/tall gearing/power = broken parts.

  12. #52
    RC Turnbuckle Jr. 08kgraves's Avatar
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    in that case nevermind
    there's no life like a LOW LIFE!
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  13. #53
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    Another design for the body would be a raindrop shaped one. I know some pinewood derby cars go really fast with that design.( different idea but it should apply here too)

  14. #54
    RC Turnbuckle Jr. 08kgraves's Avatar
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    well a raidrop is essentially what i ment by a teardrop. there the same shape, but its the most aerodynamic design there is anywhere.
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  15. #55
    RC Turnbuckle Jr. Snook Man's Avatar
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    While the teardrop shape is one of the most aerodynamic itís just not practical to make on an rc or 1:1 vehicle. Thatís why we donít see a bunch of teardrop shaped cars driving around these days.

    I made a front clip that covers the front suspension and wheels and changed to a rear wing with less drag and down force and got the least amount of drag so far.
    The front clip is a separate piece and I can make a few more shapes to see which works best and weighs less. The next front clip will be more pointed in the front sort of following the blue tape. If I go overboard with the design/shape of the body, the added weight may just negate the reduced drag. Thatís something I will have to experiment with when the rig is being powered by the engine.

    No slipper/tall gearing/power = broken parts.

  16. #56
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    Great Design so far, but don't forget that you need to find a balance between downforce and weight and drag. Too much downforce and you will actually be creating more weight the faster you go, however this will also cause you too have less top speed. More Drag and it will be harder for the rear wheels to break loose on acceleration. If I were you I would be looking at F1 style vehicles to try to imitate their body design. Try to build a really low but some what large front splitter, that will give you lots of from end downforce to keep the front end down. Then you can reduce the rest of the body size, saving you weight.
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  17. #57
    RC Turnbuckle Jr. Snook Man's Avatar
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    Here’s a good funny for your weekend.

    I haven’t even driven the rig yet and I have already crashed it.

    Testing a different front clip I bumped into the string holding the rig to the scale with my foot.

    I had been tying the string off to the front center of the 4tec bumper but the new front clips cover it so I took a shortcut and just made a loop in the string and put it over the front body posts.
    I guess when I bumped into the string with my foot the rig moved forward enough to create some slack and the loop popped off the posts from the wind turbulence.
    You guessed it, while figuring out for a split second what I had bumped into the blower continued to push the rig backwards out of the garage. By the time I saw what was happening it was too late. Under my truck it went and down my steep driveway at a slight angle. Well, off to the side of the driveway is my mailbox and the forces of nature that apply that attract RC’s to mailbox posts were in full force. If there was ever any doubt in my mind about that force of nature it is now gone for good.

    Maybe it’s an Omen… No damage this time though.
    No slipper/tall gearing/power = broken parts.

  18. #58
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    I have a full set of narrow maxx arms id sell real cheap snook. I know you'd have to swap CVD's, but heck, when you are going for 100mph, you might have to do things like that. lol
    Cummins Powered!

  19. #59
    RC Turnbuckle Jr. Snook Man's Avatar
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    Quote Originally Posted by CumminsDriver View Post
    I have a full set of narrow maxx arms id sell real cheap snook.
    Thanks for the offer buddy. Those are the narrow Maxx arms I have a few full sets I could sell you
    I'm actually thinking about cutting them down to get the rear wheels a little closer together.
    No slipper/tall gearing/power = broken parts.

  20. #60
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    I should have known. lol Im anxious to see how you come out with this. Im sure you could narrow it up even more if you wanted to cut it down, as you mentioned. It has to be at least a little fast being that light with a big block. lol 100mph is fast though. You will definately need a good place to run it. Almost need something tall (maybe a truck bed) you can stand on to see it good because it may take at least a little room to get it wound up that fast.
    Cummins Powered!

  21. #61
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    <--Take it from a Chicken who learned the hard way..this goes without saying but..
    you're gonna need a fail safe of some sort, and very long, smooth runway.
    Drag strip or freshly paved stretch of roadway would be best.
    Even an abandoned air strip would work. At high speeds the slightest
    little bump or rut could send the car airborne like a Cessna, or cartwheeling like a tumbleweed.
    My Karma runneth over your Dogma.

  22. #62
    RC Turnbuckle Jr. 08kgraves's Avatar
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    i see this happening to snook lol

    http://www.youtube.com/watch?v=x1cJD...eature=mh_lolz
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  23. #63
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    Quote Originally Posted by 08kgraves View Post
    aww dude that sucks!!! but honestly how dumb do you have to be to give yourself that short amount of space to run? thats like trying to tread a needle while running full speed toward it! someones gonna get stabbed lol

  24. #64
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    Hows that nitro taste on your electric?

  25. #65
    RC Turnbuckle Jr. Snook Man's Avatar
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    I may try something similar to the last pic... Thanks for the link ToXiC.
    No slipper/tall gearing/power = broken parts.

  26. #66
    RC Turnbuckle Jr. Snook Man's Avatar
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    My beautiful wife brings my lunch down to the workshop today.
    See sees this, looks at it for a couple seconds and says, ďThatís pretty big, are you going to put a couple engines in itĒÖ
    The thought hadnít even crossed my mind until then, but it has now

    No slipper/tall gearing/power = broken parts.

  27. #67
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    snook, just looking at the last pix, you already achieve the 100mph to me man. great job on fabricating that body.

  28. #68
    RC Turnbuckle Jr. 08kgraves's Avatar
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    yeah that is a pretty sweet body man
    there's no life like a LOW LIFE!
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  29. #69
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    with the body like that it looks like you can use the bigger tires to get that better top end without maxing out the motor or motors if you chose to do so. i think a big block with the right gear ratio would be so much better with a great tune and nice hi flo filter you can do it if anyone can! your like a rc smarty!! yes i said smarty because it sounded better in my head...

  30. #70
    RC Turnbuckle Jr. 08kgraves's Avatar
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    atleast you admit it tev lol. did you ever decide exactly what tires you were going to run snook?
    there's no life like a LOW LIFE!
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  31. #71
    RC Turnbuckle Jr. Snook Man's Avatar
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    Rear Wheels & Tires will be done similar to this. I will be using 0 offset.

    Wheels are cut to desired width.


    High speed/density foams are glued on.


    [Above images courtesy of rivermaxx].
    No slipper/tall gearing/power = broken parts.

  32. #72
    RC Turnbuckle Jr. 08kgraves's Avatar
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    ok, got ya.....

    quick question..... i thought that the standard maxx wheels were zero offset, the ones that bolt in center were like 1/2" offset, and wheels like u just posted a pic of were more like 1" offset?

    The more offset the wider the truck is overall.
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  33. #73
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    I say you should put at least four big blocks in it Snook





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  34. #74
    RC Turnbuckle Jr. Snook Man's Avatar
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    Quote Originally Posted by 08kgraves View Post
    ok, got ya.....

    quick question..... i thought that the standard maxx wheels were zero offset, the ones that bolt in center were like 1/2" offset, and wheels like u just posted a pic of were more like 1" offset?

    The more offset the wider the truck is overall.
    You can get the dish wheels in 0 Ė Ĺ - or 1 inch offset.

    Iím trying to keep the rear wheels inside the body with that last design.

    I cut a set of Narrow Maxx a-arms down ĺ inches per side and buried the pivot balls as deep as they can go and still allow up/down travel. I narrowed it 2 inches from the stock narrow Maxx width that way.
    I also made a hinge system for the rear body posts so that the body can be lifted off the front posts (like a 1:1 Funny car) for accessing a roto starter. It only takes a couple seconds to lower the body back over the front posts and install the 2 body clips rather than fooling with the entire body.
    Iím also working on making the rear spoiler angle adjustable.





    Total body length is 36 Inches long and 13 inches wide at the spoiler.
    Total weight with everything except a little fuel and RX battery is 7lbs 9 oz (thatís with stock chevrons tires, the dish wheels and foams will weigh considerably less than them).

    I also calculated the wind speed of the leaf blower at 63MPH at the nose of the body with 14 oz of drag. The wind speed falls off to 48 mph at the rear of the body so the 14 oz drag will not be as accurate as with the whole rig moving through the air but it gives me a way to measure the drag with different spoiler angles.

    Just a work in progress.
    No slipper/tall gearing/power = broken parts.

  35. #75
    RC Turnbuckle Jr. 08kgraves's Avatar
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    looking good, im digging the hinge system
    there's no life like a LOW LIFE!
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  36. #76
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    Any ideas how you are gonna get air into the engine?
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  37. #77
    RC Turnbuckle Jr. Snook Man's Avatar
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    If the engine starves of air with the filter inside the body I will either snorkel the filter above it or add a cowl/scoop to let some enter in the area of the air filter(s).
    The body will actually be lowered about another 1 inch which will leave about 2/3 of the cooling head exposed I just havenít trimmed the bottom of the body yet until I get the correct size tires.

    If thatís fails I will come up with something


    I knew that question would be asked sooner or later so I took the funny pic for giggles.
    No slipper/tall gearing/power = broken parts.

  38. #78
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    hey snook do you think it would be possible to run a channel up the center of that body for maximum air flow.. like vipers and corvettes have on there roof. ive even noticed them on roofs of bodies for rc's
    road rage its not just drivin its a blood sport

  39. #79
    RC Turnbuckle Jr. 08kgraves's Avatar
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    Quote Originally Posted by nitro on fire View Post
    hey snook do you think it would be possible to run a channel up the center of that body for maximum air flow.. like vipers and corvettes have on there roof. ive even noticed them on roofs of bodies for rc's
    thats a good question ive seen those as well.

    and snook, nice pic you got there lol
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  40. #80
    RC Turnbuckle Jr. Snook Man's Avatar
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    When you guys say air flow are you talking about for engine cooling or engine/carb air intake?



    If I can manage to reverse the transmission primary OWB (I think I can) this is an idea Iím kicking around to be able to mount 2 engines at normal height side by side.
    I also need to see if I can find mod 1 spurs that will mesh with the slipper shaft and output shaft or find mod .8 - 27T clutch bells to get the ratio Iím looking for.





    No slipper/tall gearing/power = broken parts.

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