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  1. #1
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    Slash 4x4 speed build..need help.

    Hi guys. Im trying to make an 80-100mph Slash 4x4. So this is what Ive done so far. Lots of mods and only getting 46mph on 3s! Does that sound right? Mods below...

    1900 kv long can motor (surpass brand)
    120 amp esc (banggood)
    34T mod1 spur gear
    22T mod1 pinion
    Aluminum motor plate and motor mount.
    Ran it on 3s
    So I took it out on its maiden voyage expecting stupid fast numbers and I only got 46mph hahahaha. I figured with the huge gear changes that it would still go faster than stock on 3s with the 1900kv motor? Any suggestions much appreciated. I am still a noob to modern RC cars. I have a few stock modern cars and Im an old RC guy from the late 1970's to early 90's.

    Anybody have any suggestions to make it go faster? 46mph sound right with the above setup on 3s?
    Last edited by Fullspectrum; 08-06-2019 at 04:03 PM.

  2. #2
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    Too many unknowns... use this to punch in your variables to get your theoretical top speed:

    https://scriptasylum.com/rc_speed/top_speed.html

    Have fun!
    Creativity is intelligence having fun. -Einstein

  3. #3
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    Quote Originally Posted by Squeegie View Post
    Too many unknowns... use this to punch in your variables to get your theoretical top speed:

    https://scriptasylum.com/rc_speed/top_speed.html

    Have fun!
    What unknowns? Actually I tried that calculator and didnt know a few parameters so I couldn't get it to work.
    Its a stock 4x4 slash with 34t spur and 22t pinion with 1900kv motor. Is 46mph about right on 3s?

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    Yup that sounds right. 1900kv is low low. Stock slash motor is 3300kv I believe.
    I'm running sidewinder 8, 2200kv motor, 4s, 22/36t Grp belted tires. And only got 70mph.

    I put it on 6s. I got 80. Now I think I have alot more room to go with 6s. I just need to get a new smaller capacity (weight) 6s. Mine now is 8000mah its huge and heavy. Also need to balance my tires. And probably gear up even more

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  6. #6
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    Since you have such a low kv motor, you can gear way higher and give it more voltage. Your rig woulda ran 45mph on 3s with stock motor.

    Sent from my SM-G955U using Tapatalk

  7. #7
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    Quote Originally Posted by jake414 View Post
    Yup that sounds right. 1900kv is low low. Stock slash motor is 3300kv I believe.
    I'm running sidewinder 8, 2200kv motor, 4s, 22/36t Grp belted tires. And only got 70mph.

    I put it on 6s. I got 80. Now I think I have alot more room to go with 6s. I just need to get a new smaller capacity (weight) 6s. Mine now is 8000mah its huge and heavy. Also need to balance my tires. And probably gear up even more

    Sent from my SM-G955U using Tapatalk
    Thanks Jake...I wired the ocday 120amp esc to run 2 batteries. I tried it on 6s and it seems the esc won’t have it. The light on the esc blinks red and has no power. Back to 3s and everything is fine. So I may try 4s or 5s. Bummer. A guy on YouTube had this esc on 6s and it worked so I’m not sure what the problem is. Maybe it has some kind of built in protection so you can’t run 6s. My fault because it does say 2s to 4s in the specs. I guess it’s hard to go fast on the cheap...and costs more in the end.
    Now I’m thinking to try 3-4s with a higher KV motor because I have the gearing to go faster now I just need the RPM’s. Any thoughts guys?

  8. #8
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    Quote Originally Posted by jake414 View Post
    Since you have such a low kv motor, you can gear way higher and give it more voltage. Your rig woulda ran 45mph on 3s with stock motor.

    Sent from my SM-G955U using Tapatalk
    Yeah I know...I basically wasted my time and money...lol. I clocked it at about the same mph totally stock. So...I’m thinking to take that speed controller out and get something that can handle 6s. That esc can go in one of my other cars.
    Any recommendations for an esc that can handle 6s and my 34/22 gearing with the 1900kv motor?

  9. #9
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    Quote Originally Posted by Fullspectrum View Post
    What unknowns? Actually I tried that calculator and didnt know a few parameters so I couldn't get it to work.
    Its a stock 4x4 slash with 34t spur and 22t pinion with 1900kv motor. Is 46mph about right on 3s?
    I guess the main unknown for me was your tire size.

    If you need to gear up, you can get a center motor mount from Saga.
    Creativity is intelligence having fun. -Einstein

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    Quote Originally Posted by Squeegie View Post
    I guess the main unknown for me was your tire size.

    If you need to gear up, you can get a center motor mount from Saga.
    Ok thanks. As for tires they are 100mm in diameter Speedhawk Speedtreads. So Esc wise... is a Hobbywing Max 10 too wimpy for 6s or should I get a Max8?

  11. #11
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    Ok probably going to get a Max 8 but after searching the internet for 45 min I can't figure out what size bullet connectors the Hobbywing Max 8 uses for the motor to Esc. Any ideas?

  12. #12
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    Quote Originally Posted by Fullspectrum View Post
    Ok thanks. As for tires they are 100mm in diameter Speedhawk Speedtreads. So Esc wise... is a Hobbywing Max 10 too wimpy for 6s or should I get a Max8?
    Using your values in the Scryptasylum calculator, your theoretical top speed is 56.2 MPH.

    Quote Originally Posted by Fullspectrum View Post
    Ok probably going to get a Max 8 but after searching the internet for 45 min I can't figure out what size bullet connectors the Hobbywing Max 8 uses for the motor to Esc. Any ideas?
    According to the manual:
    Output End: Female 6.5mm Gold Connectors (pre-soldered onto the PCB of the speed controller).
    https://cdn.shopify.com/s/files/1/01...17279721408534
    Last edited by Squeegie; 08-07-2019 at 11:13 AM.
    Creativity is intelligence having fun. -Einstein

  13. #13
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    Quote Originally Posted by Squeegie View Post
    Using your values in the Scryptasylum calculator, your theoretical top speed is 56.2 MPH.



    According to the manual:
    Output End: Female 6.5mm Gold Connectors (pre-soldered onto the PCB of the speed controller).
    https://cdn.shopify.com/s/files/1/01...17279721408534
    Ok thanks...I didnt thinks the specs would be in the manual...just setup instructions. Thanks. Im now thinking to put an Arrma BLX 185 6s esc in. Seems the motor connectors are the same as my cheap Surpass 1900kv motor. Actually Im kinda surprised that Arrma uses that guage wire for 6s. But that 185 esc has the right connectors and already has xt90's on it so I just drop it in. Now how to secure a 6s battery in the slash?

  14. #14
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    I use medium sized PureTech straps for my 3S and 4S LiPos.

    I don't know what size fits your specific 6S

    Measure the diameter of your LiPo and order accordingly:
    https://puretechproducts.com/product...-quick-mounts/
    Creativity is intelligence having fun. -Einstein

  15. #15
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    Quote Originally Posted by Squeegie View Post
    I use medium sized PureTech straps for my 3S and 4S LiPos.

    I don't know what size fits your specific 6S

    Measure the diameter of your LiPo and order accordingly:
    https://puretechproducts.com/product...-quick-mounts/
    Ok thanks. Got this message late. I ended up getting some Arrma straps and the Arrma Blx 185. The esc bolts right to the chassis. And on 6s it almost throws the tires off of the rim! Hahahahaha. Now just need to strap the 6s in and stiffen and lower the suspension. The Arrma BLX 185 uses the exact same size motor connectors 4mm I believe as my cheap surpass 3670 1900kv motor.

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    Relocated receiver box(will be a pain to service front diff though) and secured motor wires and esc switch.

  17. #17
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    If you are doing speed runs don't use a Hobby wing esc. They cut amps heavily under speed run conditions.
    Mamba Monster 2 is really the best bang for the buck while retraining a small size.

    The BLX 185 ESC should have all the power you need for your goal of 80-100mph. I ran 96.1 mph with the Kraton V4.
    I highly recommend getting a 17mm hex conversion and getting a set of 1/8 GRP s3 tires/wheels. They are steel belted and rated to 160mph. They are the only street tire worth buying for speed use.

    I think the motor you have will work fine on 6s

    GTR shocks made a world of difference for the stability on my slash 4x4 with the hardest springs I could find (revo springs). I believe it was XL front and XXL rear.

    -Liberty

  18. #18
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    Quote Originally Posted by LibertyMKiii View Post
    If you are doing speed runs don't use a Hobby wing esc. They cut amps heavily under speed run conditions.
    Mamba Monster 2 is really the best bang for the buck while retraining a small size.

    The BLX 185 ESC should have all the power you need for your goal of 80-100mph. I ran 96.1 mph with the Kraton V4.
    I highly recommend getting a 17mm hex conversion and getting a set of 1/8 GRP s3 tires/wheels. They are steel belted and rated to 160mph. They are the only street tire worth buying for speed use.

    I think the motor you have will work fine on 6s

    GTR shocks made a world of difference for the stability on my slash 4x4 with the hardest springs I could find (revo springs). I believe it was XL front and XXL rear.

    -Liberty
    Thanks for the advice brother. I already bought the 17mm conversion yesterday and I will grab a set of GRPs for sure. Shocks? I have a few shorter aluminum body ones Im going to try with adjustable preload. If those dont work I will look for GTR shocks. Can you recommend an air splitter and diffuser? And a better body that will fit on stock slash mounts or some other option?

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  20. #20
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    Quote Originally Posted by Squeegie View Post
    Ok...wil do...thanks bro.

  21. #21
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    I hit 93 today. 6s. 2200kv castle sidewinder system. Geared as tall as possible (23/36 I think). Grp belted tires

    Sent from my SM-G955U using Tapatalk

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    Good job!
    I haven’t run it full throttle yet, but I fit 25/31 Mod1 gears in mine.
    Creativity is intelligence having fun. -Einstein

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    Quote Originally Posted by Squeegie View Post
    Good job!
    I havenít run it full throttle yet, but I fit 25/31 Mod1 gears in mine.
    Factory motor mount?

    Sent from my SM-G955U using Tapatalk

  24. #24
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    King Headz motor mount and Hot Racing motor plate.

    I only have an old pic that does not show it, but it's in there:


    https://forums.traxxas.com/showthrea...Burning-Chrome
    Creativity is intelligence having fun. -Einstein

  25. #25
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    Quote Originally Posted by Squeegie View Post
    King Headz motor mount and Hot Racing motor plate.

    I only have an old pic that does not show it, but it's in there:


    https://forums.traxxas.com/showthrea...Burning-Chrome
    Nice! I need to get the motor mount that flips the pinion to the top of the motor.
    But then I need a new body and I just painted one up.
    My current limiting factor is my street. Need a longer one

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  26. #26
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    If you get the center motor mount, don't forget that you would probably have to get dual battery trays as well...
    Creativity is intelligence having fun. -Einstein

  27. #27
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    Quote Originally Posted by Fullspectrum View Post
    Thanks for the advice brother. I already bought the 17mm conversion yesterday and I will grab a set of GRPs for sure. Shocks? I have a few shorter aluminum body ones Im going to try with adjustable preload. If those dont work I will look for GTR shocks. Can you recommend an air splitter and diffuser? And a better body that will fit on stock slash mounts or some other option?
    If you look at all the fastest Slash 4x4's on YouTube (talking over 140mph) None have wings, splitters, or diffusers. I have been studying aerodynamics quite allot lately and I can tell you the venturi effects of those aero devices do not function correctly at 5-10mm distance off the ground due to boundary layer separation. (even though I tried them myself in the video link below)

    Delta plastics has a whole page dedicated to the Slash and SCT sized vehicles. They make speed run bodies which are thicker material. I will say that you will have to get creative with the body mounting. Many use xo-1 shock towers or modify the existing ones. For mounts I always liked the proline adjustable mounts. The Traxxas RAlly front bumper works perfectly with these mounts and these bodies.

    This video is a little old now but shows how I setup my Slash 4x4. Bright contrasting colors for visibility not because I like Batman
    https://www.youtube.com/watch?v=hLIIJCWFsPs

    You can explore my other videos and see the crazy project I have now
    Last edited by LibertyMKiii; 08-09-2019 at 12:44 PM.

  28. #28
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    Quote Originally Posted by LibertyMKiii View Post
    If you look at all the fastest Slash 4x4's on YouTube (talking over 140mph) None have wings, splitters, or diffusers. I have been studying aerodynamics quite allot lately and I can tell you the venturi effects of those aero devices do not function correctly at 5-10mm distance off the ground due to boundary layer separation. (even though I tried them myself in the video link below)

    Delta plastics has a whole page dedicated to the Slash and SCT sized vehicles. They make speed run bodies which are thicker material. I will say that you will have to get creative with the body mounting. Many use xo-1 shock towers or modify the existing ones. For mounts I always liked the proline adjustable mounts. The Traxxas RAlly front bumper works perfectly with these mounts and these bodies.

    This video is a little old now but shows how I setup my Slash 4x4. Bright contrasting colors for visibility not because I like Batman
    https://www.youtube.com/watch?v=hLIIJCWFsPs

    You can explore my other videos and see the crazy project I have now
    Hahaha...I will check it and sub you on Youtube. Thanks for the advice bro. Im just waiting on a few more parts now and going to grab GRP tires or Arrma Infraction tires next week. I will make a youtube vid soon on my small build. My goal was to go fast as cheap as I can but Im finding speed costs....lol

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    Quote Originally Posted by Fullspectrum View Post
    Hahaha...I will check it and sub you on Youtube. Thanks for the advice bro. Im just waiting on a few more parts now and going to grab GRP tires or Arrma Infraction tires next week. I will make a youtube vid soon on my small build. My goal was to go fast as cheap as I can but Im finding speed costs....lol
    Can't wait to see it.
    Hopefully with our recommendations you can save a little. I had gone through 3-4 setups before I found what worked. Speed is very expensive and what is worse it is very addictive!!!
    You may find that the 80-110mph range is enough. I hope for your sake, because pushing beyond that is another $300-600

  30. #30
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    Quote Originally Posted by LibertyMKiii View Post
    Can't wait to see it.
    Hopefully with our recommendations you can save a little. I had gone through 3-4 setups before I found what worked. Speed is very expensive and what is worse it is very addictive!!!
    You may find that the 80-110mph range is enough. I hope for your sake, because pushing beyond that is another $300-600
    Yeah I think breaking 100mph is my goal. I think that’s plenty fast and finding long desolate stretches of road is hard to find...lol. So I just ordered a Jconcepts scalpel C10 72 Chevy truck body and foam front bumper for it. I probably should have ordered the Jconcepts scalpel Illuzion body for better aerodynamics but I like the 72 Chevy body better. Plus I can mount my speed meter gps on the bed of the truck. Will definitely keep you posted on progress. I’m really wondering how long the Surpass cheapie 1900kv motor is going to last on 6s....hahahahaha.
    One big regret I have is not starting out with a low center of gravity lcg Slash for this build. I hope I can get it low enough.
    Last edited by Fullspectrum; 08-09-2019 at 04:05 PM.

  31. #31
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    Quote Originally Posted by Fullspectrum View Post
    Hahaha...I will check it and sub you on Youtube. Thanks for the advice bro. Im just waiting on a few more parts now and going to grab GRP tires or Arrma Infraction tires next week. I will make a youtube vid soon on my small build. My goal was to go fast as cheap as I can but Im finding speed costs....lol
    Nice... I'm digging that Infraction!
    Creativity is intelligence having fun. -Einstein

  32. #32
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    Quote Originally Posted by Squeegie View Post
    Nice... I'm digging that Infraction!
    Yeah only one vid on my channel so far but there will be more coming. An I have an infraction on the way as well.

  33. #33
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    Quote Originally Posted by Squeegie View Post
    If you get the center motor mount, don't forget that you would probably have to get dual battery trays as well...
    Dang didn't think about that. Guess I could get mod 1 gearing but I'm maxed currently

    Sent from my SM-G955U using Tapatalk

  34. #34
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    Quote Originally Posted by jake414 View Post
    I hit 93 today. 6s. 2200kv castle sidewinder system. Geared as tall as possible (23/36 I think). Grp belted tires

    Sent from my SM-G955U using Tapatalk
    That's sick! Congrat bro! I'm geared 22/34 currently. Still waiting on parts. May be a week before I can attempt any speed runs still. And I have a new body 2 weeks out still.

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    Quote Originally Posted by Squeegie View Post
    Good job!
    I haven’t run it full throttle yet, but I fit 25/31 Mod1 gears in mine.
    Sweet! Any Youtube vids? I'm hoping to get some Youtube vids of mine when I get it out.

  36. #36
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    Quote Originally Posted by jake414 View Post
    Dang didn't think about that. Guess I could get mod 1 gearing but I'm maxed currently

    Sent from my SM-G955U using Tapatalk
    I'm at 22T but I'm guessing 25T is as big as you can go with the side motor mount. I tried a 29T and it wasn't going in. I have a 25T and a 26T that I will try later. I think with some light dremel work you can massage a bigger pinion in there.

  37. #37
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    Quote Originally Posted by Fullspectrum View Post
    Yeah I think breaking 100mph is my goal. I think that’s plenty fast and finding long desolate stretches of road is hard to find...lol. So I just ordered a Jconcepts scalpel C10 72 Chevy truck body and foam front bumper for it. I probably should have ordered the Jconcepts scalpel Illuzion body for better aerodynamics but I like the 72 Chevy body better. Plus I can mount my speed meter gps on the bed of the truck. Will definitely keep you posted on progress. I’m really wondering how long the Surpass cheapie 1900kv motor is going to last on 6s....hahahahaha.
    One big regret I have is not starting out with a low center of gravity lcg Slash for this build. I hope I can get it low enough.
    I can't recall exactly but there was some posts recently (past 2 months) where a speed runner mentioned his regrets taking a truck body over 80mph. Kept have blow over crashes. His was the scalpel body.

    Not saying that it cannot be done, maybe a front splitter would help. Aerodynamics is like a brick when using a truck body.

  38. #38
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    Quote Originally Posted by LibertyMKiii View Post
    I can't recall exactly but there was some posts recently (past 2 months) where a speed runner mentioned his regrets taking a truck body over 80mph. Kept have blow over crashes. His was the scalpel body.

    Not saying that it cannot be done, maybe a front splitter would help. Aerodynamics is like a brick when using a truck body.
    Dammit....oh well. I figured that but we'll see what happens. I'm going to try adding some weight to the front to keep it down..

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    So the only thing I have done recently was lower the Slash with some Hosin 98mm Aluminum shocks with adjustable spring preload. They seem pretty decent and stiffen up the suspension a lot. I changed the mounting locations on the optional holes already on the arm and kept the top in the middle.

    A- arms in the rear are flat and the front are slightly negative to the ground. I'm trying to keep the front a little lower than the rear. On the front I had to put some limiters in to shorten the shock a little. Still waiting on a body, bumper and belted GRP tires.

    Also.. since I'm an old school guy I built a Tamiya Boomerang with 60amp esc and 5900kv motor on a 7.2v nimh. And...a "new" 1995 Futaba Attack stick radio...just to take me back to the old days. Took it out to try on the road today. It flys for a Tamiya. Not sure the speed. Will clock it tomorrow. I'm guessing 30mph?
    Last edited by Fullspectrum; 08-12-2019 at 10:01 PM.

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    I know it’s not Traxxas but I did a speed run with the Tamiya Boomerang and got 35mph but got 32 mph on camera. She rips pretty good for a cheap setup on 7.2v Nimh. Vid is up on my channel. https://youtu.be/KIQpkQEfGaQ

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