Results 1 to 36 of 36
  1. #1
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683

    Building ideas for a fast Rustler

    After reading about fast builds I thought it might be worth a thread listing ideas & theories to make the task easier

    In my experience you need several upgraded parts to make a Rustler push well past 70mph. That's not saying the stock format is an easy platform to improve but for a specific purpose you can make it very fast

    You need a donor vehicle - obviously

    A radio that has long range

    Next, you need a long smooth, open place to test. You don't want people (especially kids), animals, obstacles etc

    "From about 1000 feet away, drive the car towards you --- through a speed trap of some kind , then as is goes away, slow the car down -- slowly -- using 700 to 1000 feet............ Slowing the car down is Very important. If you get it sideways above 50 mph , air -will lift the car off the ground --- so keep it Straight (a gyro can help - if set correctly) Limit your dual-rate & add as much caster as you can. Mount the body so it does not flap around.(body-side/hood/front bumper." - Nic Case


    Equipment to go over 70mph

    Radio: 2.4GHz - long range is crucial

    Traxxas
    Futaba
    Airtronics

    Motor + ESC: Open - Biggest isn't necessarily the best but it does help

    Traxxas Combo
    Tekin Combo
    Mamba Monster Combo

    There are many more variations, these examples are capable of running 6S without too much effort & they are fairly matched

    Battery: 4S, 5S or 6S, 3000mah+, 30C+...choose your brand, here are some suggestions

    Neu
    Hyperion
    Thunderpower

    Tyres: Belted or foam are best. 1/8 scale is a definite advantage. I balance mine using Blu tack

    Traxxas
    GRP M01 Rally
    Jaco

    Gears: Steel Mod1.0 (0.8 will work just as well)

    Spur

    Traxxas Mod1
    Integy Mod1

    Pinion

    RCM Mod1
    RR Mod1



    More to come...feel free to add some concise information if you want, the above parts will get you well past 70mph. There are however many more aspects to a speed run Rustler if you want repeatable performance, I'm sure others will list up suspension, transmission, arms, shafts, steering etc...

  2. #2
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Dont forget about aero mods. Probably the MOST important thing you can do to your high speed build is get the aero package sorted out to keep the air from going under the truck. You can build a custom body with a nose cone:


    Or, you can build a wing mount or a deflector for the nose as many have done. If you dont do aero mods, you can do all the cool building you want and you can go ahead and weight the front of the truck all you want, but at a certain point it WILL take off like a rocket.

    Also, lowering your suspension will go hand in hand with the aero mods and are an integral part of a "go fast" truck. You can strap the suspension down with zip ties (ghetto way) or you can do it the right way using fuel tubing under the shock piston. 3/4 of an inch is usually as far as youd want to go.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  3. #3
    RC Champion
    Join Date
    Dec 2009
    Location
    MI
    Posts
    2,502
    Quote Originally Posted by pavmentsurfer

    Also, lowering your suspension will go hand in hand with the aero mods and are an integral part of a "go fast" truck. You can strap the suspension down with zip ties (ghetto way) or you can do it the right way using fuel tubing under the shock piston. 3/4 of an inch is usually as far as youd want to go.
    I agree that zip-ties are pretty ghetto, but I foresee some people saying that fuel tubing isn't the right way either, but for straight line speed runs, it's probably almost as good.

    I agree with 3/4" being about the max. That's the length I have on mine, and with Anacondas, the ride height is really slammed and just right. With 2.2's though, my chassis was dragging on the ground without a small preload spacer.
    ◄▲▼► SUMMIT ●○●○● 2 RUSTLER VXL's ●○●○● MERV ◄▲▼►

  4. #4
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Just curious, what other ways are there to lower your truck 3/4 of an inch? I guess you could use some shorter shocks? Realistically, using fuel tubing is no different than a shorter shock. But shorter shocks would be the "truest" way to go low.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  5. #5
    RC Racer
    Join Date
    Sep 2010
    Location
    Southern WV
    Posts
    217
    yeah a few ppl on here has used the jato shocks. i personally went the ghetto route of using zipties.
    Rusty 4600kv
    2wd Slash
    3s Lipo Power

  6. #6
    RC Qualifier
    Join Date
    Oct 2004
    Location
    striking jealousy into the hearts of all onlookers!
    Posts
    917
    Quote Originally Posted by PBO
    Limit your dual-rate
    As many times I have lost control at high speed I know that limiting your d/r is not a good idea because it also limit how much steering you would have when your trying to correct.

    Setting your steering EXP adjustment works best if you have that option. It has saved me alot after I made that adjustment. My tx has other options that I have no clue what they do. But it's better to set your steering EXP adjustment instead of the d/r.
    I got skills!

  7. #7
    RC Racer
    Join Date
    Feb 2007
    Location
    NoVA
    Posts
    204
    From what i have learned so far in my quest to go faster:

    Consistently going over 70 or just doing it a couple times is big here. My truck consistently will do 70-71 with the gearing it's on. I attribute about 75% of this to foam tires. Rubber tires are just not consistent, lets a lot more air under the truck chance of blow overs after 65 just become all that more probable. Plus not many tires are made for 65+mph runs. They will eventually shred apart.

    I could just go up to 1/8 buggy tires and do some 1 run wonders as i would like to call them but i'm just taking a different route. I like foams, if you are consistently going to try and make speed runs there is no other way to go. Once you hit 70 the key to doing it over and over is stability. Also flat long stretch of ground is a must. I am only using maybe an 1/8 mile stretch of road. Not ideal but i haven't found anywhere else that is safe. Another point i would like to bring up is that foam tires let you really get into the throttle a lot quicker then rubber tires so it does not require as much space.

    I'm not quite at the point where i need aero mods...at least i don't think so. The truck seems planted enough to not want to lift. I have my front shocks lowered with fuel tubing. To me it is no different then zip ties other then the ties just look ghetto. Also they will stretch over time and can break.

    About gearing, at some point you will be limited as to how tall of a ratio you can achieve.

    48P 35/76 ratio of 2.17
    32P highest ratios if i remember correctly are 28/52 ratio of 1.85
    Mod1.0 26/34 ratio of 1.30

    So you can go much taller with mod1, whether or not you need it well that all depends on your setup and how fast you want to go. With these 3.8" tall foams i did need to go mod1. It takes very tall gearing to run a high number with these. You don't need 32P or mod1 with rubber tires and the stock VXL to run 70mph. 35/76 with a tall 1/8 buggy tire i believe can push 75 as long as the truck can stay down and go straight.

    At some point you will need a taller ratio and then the switch to mod1 is inevitable. Anyone going for big power should just go straight to mod1.
    Rustler VXL - Stock VXL system on 3S / 76.8mph

  8. #8
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    Quote Originally Posted by fastman
    As many times I have lost control at high speed I know that limiting your d/r is not a good idea because it also limit how much steering you would have when your trying to correct.

    Setting your steering EXP adjustment works best if you have that option. It has saved me alot after I made that adjustment. My tx has other options that I have no clue what they do. But it's better to set your steering EXP adjustment instead of the d/r.
    Dual rate fine tunes the speed of your steering & in my experience having the steering speed slowed actually improves the chance of corrections or catching the Rustler before a crash...I might just have slow reflexes though

    Some TX's offer a lot of fine tuning with steering end point & dual rate, which can include 'on screen' mapping

  9. #9
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    Transmission

    FLM 1 degree
    Integy
    New Era

    NB: Traxxas Rear Hub Carriers 1.5 Degree 4-Tec will work with transmissions that don't offer Toe-in

    Must be steel internal gears & it's always wise to have spare planetary gear sets

    Drive shafts

    FLM
    MIP

  10. #10
    RC Qualifier
    Join Date
    Oct 2004
    Location
    striking jealousy into the hearts of all onlookers!
    Posts
    917
    Quote Originally Posted by PBO
    Dual rate fine tunes the speed of your steering & in my experience having the steering speed slowed actually improves the chance of corrections or catching the Rustler before a crash...I might just have slow reflexes though

    Some TX's offer a lot of fine tuning with steering end point & dual rate, which can include 'on screen' mapping
    You do know that the steering d/r only effects the range of the servo not speed. Adjusting the steering EXP would have more effect on the servo speed.

    When I first started doing speed runs I always thought that was the best thing to do and that is what I did (set d/r low so it would drive straight). But now Im alot faster and my street is narrow I can't do that anymore I need all my steering range so when the car has gotten sideways and gone beyond point where the gyro can't help me I will need all the steering range I can get to straightening it out are else I will be hitting something. Well that already happen so that's way I don't touch the d/r but used the EXP instead.
    I got skills!

  11. #11
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    I've mixed up my EPA's with my EXP's - sorry about that, running low on sleep at the moment

    I still don't understand why you'd want full steering range...you only need to turnm around not navigate a tight technical track

  12. #12
    RC Qualifier
    Join Date
    Oct 2004
    Location
    striking jealousy into the hearts of all onlookers!
    Posts
    917
    Sometimes I will lose traction or hit debris then the car will rocket in one direction and having full steering range helps alot to get it straight again. Say for instance, if you don't have full steering and lose traction then the car start heading for the curve and with the steering range low the car will not have enough steering range to steer away from the curve in time. With the full range steering and EXP option you can easily avoid situation like that. I learned the hard way.
    I got skills!

  13. #13
    RC Turnbuckle Jr.
    Join Date
    Mar 2009
    Location
    San jose, California :D
    Posts
    4,681
    Nice thread PBO..we needed one of these ;P
    EMBE/ Savage X
    x2 BL slash
    Ultra lx1e

  14. #14
    RC Qualifier
    Join Date
    Mar 2010
    Location
    charlotte NC
    Posts
    311
    How low will the Jato shocks get you?
    Too many characters and not enough space allowed.

  15. #15
    RC Qualifier
    Join Date
    Oct 2004
    Location
    striking jealousy into the hearts of all onlookers!
    Posts
    917
    Quote Originally Posted by jarchie
    How low will the Jato shocks get you?
    It will get you very low but you will need FLM towers to balance out the front & rear. FLM has the best mounting positions.

    If your top speed is under 75mph it's not necessary to drop the Rustler low.
    I got skills!

  16. #16
    RC Turnbuckle Jr. rjm2519's Avatar
    Join Date
    Feb 2008
    Location
    Fl
    Posts
    3,062
    Somewhere someone has to have a touring car type body, preferably a dodge viper, that would cover the wheels and the entire front end for aerodynamic purposes. I have thoroughly convinced myself with a body like this it would be more than possible to get over 75 mph with a vxl system under ideal conditions with a monster 3s pack.
    Donít handicap children by making life easy

  17. #17
    RC Qualifier
    Join Date
    Oct 2004
    Location
    striking jealousy into the hearts of all onlookers!
    Posts
    917
    Quote Originally Posted by rjm2519
    Somewhere someone has to have a touring car type body, preferably a dodge viper, that would cover the wheels and the entire front end for aerodynamic purposes. I have thoroughly convinced myself with a body like this it would be more than possible to get over 75 mph with a vxl system under ideal conditions with a monster 3s pack.

    A touring car type of body wouldn't work as well as the stock body for a number of reasons. One It would have to much open space underneath it causing alot more problems. The stock body is good at just about any speed if it's not beat all up. But a touring body for the Rustler would look cool.
    I got skills!

  18. #18
    RC Turnbuckle Jr. rjm2519's Avatar
    Join Date
    Feb 2008
    Location
    Fl
    Posts
    3,062
    You could use scrap lexan to fill the gaps where the chassis doesn't meet the body. I don't see how it wouldn't help having the tires all under the shell out of the way to improve aerodynamics. If you lowered the car enough airflow under the car would be minimized as well.
    Donít handicap children by making life easy

  19. #19
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    Thought I might bring this one back for some aerodynamics...

    Aerodynamics is a complex subject. To describe the perfect setup is very subjective & requires a large matrix of settings to achieve the best configuration for a given driving style however there are many constants (I've skimmed over a few to keep things simple);

    a) attached & separated flow
    b) velocity distribution
    c) boundary layer
    d) laminar & turbulent flow
    e) the Reynolds number
    f) Bernoulli's equation
    g) Venturi effect
    h) drag
    i) lift

    You could write a book on each subject. Maybe the best way to improve the Rustler aerodynamic profile is to keep any changes simple & make single adjustments to those changes so that you don't get lost. At least this approach lets you understand the effect of each change & interpret what you need

    If you consider air as liquid, as in it becomes hard when you are moving through it quickly then to me it makes more sense. In effect you are pushing through it & you need to trick as much benefit from the 'liquid' as possible



    One of the easiest & most effective changes you can make is to reduce the lift characteristics. If you can manage what happens to the air at the front of the Rustler then you have an excellent starting point. The easiest way is to this is to control the air flow under the vehicle by creating a splitter...


  20. #20
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    Doing this allows airflow under the vehicle but at a 'beneficial' rate that will exit without generating considerable lift. You can improve on this though by creating a venturi at the rear of the vehicle. In simple terms this means the rear is open & the high pressure under the body escapes as low pressure. Drag RC's must use the venturi effect to stop blowovers



    Open wheel vehicles have the added problem of wheels



    There's only so far you can go with a Rustler to retain the overall shape & significantly improve the aerodynamic profile. You can't fill in the space between the wheels, you can't cover the entire vehicle wheels & all, so you must focus on the body & make improvements there. In addition to the 'splitter' & venturi you can reduce the height or volume of the body, this in turn reduces the size hole you need to push through the air



    The one above is mine, I made later changes to smooth the boundary layer & increase the venturi by extending the body length with flat pieces of polycarb riveted to the main body, removing the rear wing & shortening the splitter depth

    Vertical stabilizers are usually considered mandatory at speeds over say 80mph & you rarely see a very fast RC without significant vertical stabilizers

  21. #21
    RC Racer
    Join Date
    Apr 2011
    Location
    Nyc
    Posts
    127
    It's Funny PBO, that you had no faith in my 100+mph rustler set up but it's so funny that your thread is so similiar to mine that i just posted last week.
    And IT'S SO FUNNY THAT DAD LOCK'S MY THREAD AND YOU COME OUT WITH A SIMILIAR THREAD LIKE MINE THAT YOU HAD NO FAITH IN 12HRS LATER AFTER MY THREAD GET'S LOCK FOR NO REASON AT ALL. THAT'S SO FUNNY HMMMMMMMMMMMM???

  22. #22
    RC Racer
    Join Date
    Apr 2011
    Location
    Nyc
    Posts
    127
    Quote Originally Posted by PBO View Post
    After reading about fast builds I thought it might be worth a thread listing ideas & theories to make the task easier

    In my experience you need several upgraded parts to make a Rustler push well past 70mph. That's not saying the stock format is an easy platform to improve but for a specific purpose you can make it very fast

    You need a donor vehicle - obviously

    A radio that has long range

    Next, you need a long smooth, open place to test. You don't want people (especially kids), animals, obstacles etc

    "From about 1000 feet away, drive the car towards you --- through a speed trap of some kind , then as is goes away, slow the car down -- slowly -- using 700 to 1000 feet............ Slowing the car down is Very important. If you get it sideways above 50 mph , air -will lift the car off the ground --- so keep it Straight (a gyro can help - if set correctly) Limit your dual-rate & add as much caster as you can. Mount the body so it does not flap around.(body-side/hood/front bumper." - Nic Case


    Equipment to go over 70mph

    Radio: 2.4GHz - long range is crucial

    Traxxas
    Futaba
    Airtronics

    Motor + ESC: Open - Biggest isn't necessarily the best but it does help

    Traxxas Combo
    Tekin Combo
    Mamba Monster Combo

    There are many more variations, these examples are capable of running 6S without too much effort & they are fairly matched

    Battery: 4S, 5S or 6S, 3000mah+, 30C+...choose your brand, here are some suggestions

    Neu
    Hyperion
    Thunderpower

    Tyres: Belted or foam are best. 1/8 scale is a definite advantage. I balance mine using Blu tack

    Traxxas
    GRP M01 Rally
    Jaco

    Gears: Steel Mod1.0 (0.8 will work just as well)

    Spur

    Traxxas Mod1
    Integy Mod1

    Pinion

    RCM Mod1
    RR Mod1



    More to come...feel free to add some concise information if you want, the above parts will get you well past 70mph. There are however many more aspects to a speed run Rustler if you want repeatable performance, I'm sure others will list up suspension, transmission, arms, shafts, steering etc...




    Rember This, you been there & done that. so go back hmmmmmmm!


    Draven, I've been there & done that. Thanks anyway

    It seems pointless to repeat what has already been explained by others here but all the RC people who are sitting on the edge of their seat waiting for you to reveal the ingenious modifications or adjustments that overcome the known Rustler issues aren't getting any discussion or answers from you. This is up to you but as I explained; no answers or explanation = skepticism

    I discussed my concerns regarding your claim with those that believe & respect you on Youtube & frankly they don't have a clue. I didn't create threads here or anywhere else 'hating' your setup but in the way of forums when it came up I've asked the same questions & as per Youtube, I've been labeled a hater etc

    It's up to you I guess but as the more experienced RC people here start to relax back into their seats with increasing skepticism, your claims seem less likely...

    As Tat2 said "I'd love to be proven wrong here. Really!" - you need to believe this

  23. #23
    RC Champion
    Join Date
    Sep 2010
    Location
    the giant boot. Anybody?
    Posts
    2,727
    This thread is headed the same way, if you guy's want to bad mouth each other or be rude do it in PM's. Some of us are interested in the simplicity or technology of people's speed acheivement's. Believe it or not, but most of all keep it to yourself if you feel the person is hiding something or trying to pull a fast one over on us. Don't go name calling or "YELLING". I'm not pointing finger's at anybody, just saying these thread's can lead to big achievement's in speed for all of us.
    *Proud Husband of United state's Air Force wife.*

  24. #24
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    I think PBO and fastman are both actually addressing the known issues with going fast. Non have CLAIMED to go over 100... they are just stating what issues are likely to arise in the quest for high speeds. I read this thread with interest (and im tickled to see my own vehicle in there as an example of what TO do for a change... hehe... thanks guys "sniff")
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  25. #25
    RC Turnbuckle Jr. Desert JATO's Avatar
    Join Date
    Aug 2007
    Location
    Riyadh, Saudi Arabia
    Posts
    5,661
    Quote Originally Posted by pavmentsurfer View Post
    i think pbo and fastman are both actually addressing the known issues with going fast. Non have claimed to go over 100... They are just stating what issues are likely to arise in the quest for high speeds....
    not true....check your info before posting it.......

    Quote Originally Posted by pbo;
    my best was 168.8km/h with gps,

  26. #26
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    7,276
    Kinda insteresting how my 1:1 car easily does 100 mph without all the fancy air flow stuff. I don't think a lot of downforce is what you are looking for to go fast in such a small car, but just neutral behaviour. A car which is designed for a lot of downforce, will take off as soon as a little unwanted air comes under it.
    Nobody is born with experience

  27. #27
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Quote Originally Posted by Desert JATO View Post
    not true....check your info before posting it.......
    Should have been more specific... non have claimed IN THIS THREAD to have gone over 100 (i checked again... non have claimed it.)
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  28. #28
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Quote Originally Posted by Petertje60 View Post
    Kinda insteresting how my 1:1 car easily does 100 mph without all the fancy air flow stuff. I don't think a lot of downforce is what you are looking for to go fast in such a small car, but just neutral behaviour. A car which is designed for a lot of downforce, will take off as soon as a little unwanted air comes under it.
    Keep in mind though, were talking 1/10 scale. 100mph at 1/10 is... well... I dont know exactly, but its well over 1000mph in 1:1... if you were going that fast in 1:1 scale... aerodynamics and lift would CERTAINLY be a huge issue.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  29. #29
    RC Champion
    Join Date
    Sep 2010
    Location
    the giant boot. Anybody?
    Posts
    2,727
    The power to weight ratio we are talking here is like taking the power a bugatti veyhron making 1,001hp and putting it in a power wheel's barbie jeep. Coming up with a way to make it stay down and planted is the ticket.
    *Proud Husband of United state's Air Force wife.*

  30. #30
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    7,276
    Quote Originally Posted by pavmentsurfer View Post
    Keep in mind though, were talking 1/10 scale. 100mph at 1/10 is... well... I dont know exactly, but its well over 1000mph in 1:1... if you were going that fast in 1:1 scale... aerodynamics and lift would CERTAINLY be a huge issue.
    The scale is only useful for length/width/height comparision but for other things it's useless. If the weight would be 1/10 of a 1:1 car, you would need way more than a Mamba Monster.
    I was not talking about lift, I meant that looking for a lot of downforce is useless. You just have to keep it on the ground, that's all. Not saying that it is easy to do, but it is the only thing you need. For racing you need downforce to go fast around corners, but for speed runs you don't as much.
    Nobody is born with experience

  31. #31
    RC Turnbuckle Jr. Desert JATO's Avatar
    Join Date
    Aug 2007
    Location
    Riyadh, Saudi Arabia
    Posts
    5,661
    Quote Originally Posted by pavmentsurfer View Post
    Should have been more specific... non have claimed IN THIS THREAD to have gone over 100 (i checked again... non have claimed it.)
    Honestly your exaplantion is relly FUNNY...
    So what is the difference if pbo claimed this huge top speed ( 104+mph ) in this thread or in another one ??

  32. #32
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    Quote Originally Posted by Petertje60 View Post
    I was not talking about lift, I meant that looking for a lot of downforce is useless. You just have to keep it on the ground, that's all
    This is correct. Too much 'downforce' creates drag & this is what I modified to 'release' more speed from my setup. Removing the aggressive elements smooths the flow & reduces the drag coefficient. It does need to stay planted though & a normal 1:1 passenger sedan usually becomes very light in the rear at a certain speed (depending on speed & shape) & will start to lift off. Adding elements such as rear defusers to 1:1 cars creates the vital venturi effect which keeps the rear end planted

    Audi had these exact early problems with their first TT coupe design at high speeds. Braking & cornering at these speeds (approaching 160mph from memory) caused the rear to loose traction & attempt to overtake the front which had predictable outcomes

    For interests sake the 1/10 100mph speed scales to 316.23 mph 1:1

    Desert JATO, I'm not claiming my top speed as a record or asking anybody to believe it. I don't have anything to support the claim & the context that I mentioned it was in this direction also...just the final speed I believe I achieved

  33. #33
    Marshal Dadx2mj's Avatar
    Join Date
    Aug 2007
    Location
    So Cal
    Posts
    21,209
    For what it is worth a 1/10th scale car going 100 mph works out to 316.23 mph to scale.

    SCALE SPEED CALCULATOR LINK
    BlindMan Racing
    Rusty - MERV - Pede 4x4-Alias
    SPC Lipo Power

  34. #34
    RC Turnbuckle Jr. pavmentsurfer's Avatar
    Join Date
    Jul 2009
    Location
    Ontario, Canada
    Posts
    11,145
    Thanks for that clarification guys... i wasent sure how to do that math.
    Pede, Summit,
    ERBE, Rally,
    Motley Crew, 1SQ

  35. #35
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    7,276
    There is a long thread about scale stuff already. The calculator uses a factor of the square root of 10 instead of 10. The outcome is meaningless for things you have to cope with to get to 100 mph. Power to weight ratio can be used without scale calculations for comparision with 1:1 cars. Scaled or not, you still want 100 mph.

    The Audi problem didn't decrease top speed, it just decreases the amount of control you have left at it. That was exactly what I meant. You get higher speeds, just less control. Which means longer distance needed for braking.
    Nobody is born with experience

  36. #36
    RC Turnbuckle Jr. rag6's Avatar
    Join Date
    Mar 2008
    Location
    PM me if ya wanna bash at Greenwood Bashplex!
    Posts
    13,072
    Draven, dad did not close your thread because of anything you did. Pbo did nothing to get your thread closed. He was just following the rules he has to enforce, and we have to live by in this forum. Thank the guy who was warned ahead of time and continued trolling the issue. That guy closed the thread. Losing your cool in this thread is not helping your credibility.
    I believe your vid if it makes any difference, but what do I know, as my top speed was only 62mph(no vid, sorry) w/ a sidewinder4600 2 pole(record lol?).
    Please stick around though, as we all need to see your continued efforts/failures/successes. There will be people who will believe your accomplishments and not believe them. Just keep doing what you are doing and be as open as possible. Your work does have value here.
    Wanna bash at Greenwood Bashplex in Pittsburgh ???

  37. #37
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    A few tips;

    Brushless motors loose torque the more they rev. It won't work to have your vehicle geared to achieve your speed at 60,000rpm, the torque curve drops away & is further compromised by frontal drag, drivetrain drag etc. A simple equation is to gear for twice the speed you want. Therefore your RPM should be half the motor maximum RPM & comfortably within a strong torque range

    When doing your calculations you can use this Top Speed Estimator by entering values into all the boxes. It's important to use a lesser voltage value to compensate for voltage sag & other issues such as drag. This is a conservative look at the setup I used...it allows some ceiling height;

    Differential Ratio: 1
    Transmission Ratio: 2.727272727272727
    Other Ratio: 1
    Spur Tooth Count: 34
    Pinion Tooth Count: 26
    Total Voltage: 19.20 (I used 3.2V per cell)
    Motor KV: 2700
    Tire Diameter (inches): 4
    Tire Ballooning (inches): 0.1
    Motor Current Draw: 150
    Motor Coil Resistance: 0.004
    Spur/Pinion Ratio: 1.31 : 1
    Total Ratio: 3.56643 : 1
    Tire Circumference (inches): 13.19 inches (335.15 mm)
    Rollout: 3.70:1
    Total Motor Speed: 50220 RPM
    Vehicle Speed: 175.95 mph (282.63 km/h)
    Effective KV Value: 2615.63
    KT constant: 0.5 oz-in/A
    Motor Torque:0.39 ft-lbs
    Final Torque: 1.4 ft-lbs
    Final Power: 2880 watts (3.9 HP)

  38. #38
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    7,276
    Do the foam tires (as most use for high speed runs) really balloon? Even if its only 0.1 inch? Be aware you add 5% (theoretical) top speed with 0.1 inch radius on a 4 inch diameter.
    Last edited by Petertje60; 04-30-2011 at 01:49 AM. Reason: added info
    Nobody is born with experience

  39. #39
    RC Champion
    Join Date
    Feb 2009
    Location
    Sydney
    Posts
    1,683
    I use the full profile Jacos (white) & they do balloon when I've bench tested them, 1/10 of an inch is maybe a little conservative - it could be 1/8. I use the white Jacos for the gearing benefit over the low profile also

    The low profile (faux CF) Jacos may not balloon as much?

    Edit: The white Jacos when new are 4.23" - I use foam tyre condition & this wears them pretty fast so my 4" is about right
    Last edited by PBO; 04-30-2011 at 02:47 AM.

  40. #40
    RC Turnbuckle Jr. Petertje60's Avatar
    Join Date
    Jan 2011
    Location
    Rotterdam, Netherlands
    Posts
    7,276
    My point was that adding something like 0.1 inch ballooning adds even 5% top speed.
    For theoretical speed the calculator is useful. For the real world IMO it is useless.
    Nobody is born with experience

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •