Limitless First time speed build.

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@LegacyIV how's it going man? You get the car sorted out?
Changing the throttle curve now. I tried saving the curve I want and loading the exact same thing for my second xlx2 but it looks nothing like how I did it any tips?
Ok I figured out how to save the throttle. Car is running muuch smoother now. Trying to figure out how to upload the before and after videos. Thanks for the help. I set my punch to 30% btw
 
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Changing the throttle curve now. I tried saving the curve I want and loading the exact same thing for my second xlx2 but it looks nothing like how I did it any tips?
Ok I figured out how to save the throttle. Car is running muuch smoother now. Trying to figure out how to upload the before and after videos. Thanks for the help. I set my punch to 30% btw
Once you save the file and go to the second esc, make sure the curve on the second esc says linear, maybe even toggle it between the options then put it on linear to basically reset the line,
After you do that hit load curve and add the one you saved. It should work properly
 
That was actually a success. It took me a minute to get it rigged up, but I ran a comparison between a Castle 8mm bullet (left) and an extracted bullet from a QS8 connector (right). The Castle bullet came in at ~220mΩ and the QS8 bullet at ~290mΩ which, at this resolution, is an irrelevant difference and can be considered, near as makes no difference, identical.
View attachment 284741
Very interesting. I wonder if there’s a difference connecting a bullet to a qs8 v qs8 to qs8. The reason I ask is because the bullet barely reaches beyond the resistor portion of the qs8 connector so there’s less surface area of the actual connection….
 
Hey all I just really need some help with my build. Limitless v2 dual 1721, x4 cnhl 6200 4s1p have been ordered. My main problem at the moment is figuring out what gearing I should be using. I've already watched all of Raz's videos 100 over seeing if he mentions what gears to use but he doesn't. Community may frown upon me for just wanting the hand out but the thought of going through all these different pinion and spur gears buying them $20 a pop just doesn't sound enjoyable to me. I saw that these cars are fast and just want to enjoy the speed. I just want to know what gearing is used for 150mph and 180mph with my setup and I guess a bashing gearing setup also for the days I just want to rip around without blowing my motors/esc. Sorry for the long post and I understand if im banished for wanting the handout I know some of you guys worked very hard to reach these high mph and I respect it but the gearing part of this hobby is where the joy bleeds out for me.
I have a motor and gearing spreadsheet from RC Explained that gives me my speeds from different gears....try using a 30t pinion and a 34t spur/spool....at 32t pin and 34t spur with the castle 1721 my spreadsheet say I can do 227mph
Hey all I just really need some help with my build. Limitless v2 dual 1721, x4 cnhl 6200 4s1p have been ordered. My main problem at the moment is figuring out what gearing I should be using. I've already watched all of Raz's videos 100 over seeing if he mentions what gears to use but he doesn't. Community may frown upon me for just wanting the hand out but the thought of going through all these different pinion and spur gears buying them $20 a pop just doesn't sound enjoyable to me. I saw that these cars are fast and just want to enjoy the speed. I just want to know what gearing is used for 150mph and 180mph with my setup and I guess a bashing gearing setup also for the days I just want to rip around without blowing my motors/esc. Sorry for the long post and I understand if im banished for wanting the handout I know some of you guys worked very hard to reach these high mph and I respect it but the gearing part of this hobby is where the joy bleeds out for me.
I have a spreadsheet from RC Explained...try using a 30t pinion and a 34t spur/spool
Here it is
 

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Very interesting. I wonder if there’s a difference connecting a bullet to a qs8 v qs8 to qs8. The reason I ask is because the bullet barely reaches beyond the resistor portion of the qs8 connector so there’s less surface area of the actual connection….
From my own experience, Castle bullets lead to unreliable connections when plugged into QS8s because they don't reach down far enough. That's why I extract the pins from QS8 males connectors whenever/wherever I use bullets in my power couplings. The only place I use Castle bullets is to connect the motor to the ESC.
I have a motor and gearing spreadsheet from RC Explained that gives me my speeds from different gears....try using a 30t pinion and a 34t spur/spool....at 32t pin and 34t spur with the castle 1721 my spreadsheet say I can do 227mph

I have a spreadsheet from RC Explained...try using a 30t pinion and a 34t spur/spool
Here it is
If you enter unrealistic values into a speed calculator you'll get unrealistic results. You're leaving out two crucial factors in that calculation: Voltage & KV sag under load. Running on 8S, depending on your batteries, your voltage is going to sag down to at least 27.5-28V under optimal conditions with great batteries that have been heated and properly broken in, etc. and possibly down as far as 25, 24 or 23V if you have mediocre batteries at room temp. At those speeds you should be calculating the motor at roughly 80% efficiency (2020KV in the case of a 1721), give or take 1-2%. Where exactly you're running in terms of efficiency can be determined after the run with data log analysis. A third factor will be that, as you get faster, the air gets thicker.

If I put those numbers through my speed calculator, assuming a voltage drop to 3.3V/cell (26.4V total) I get 199mph...which isn't going to happen with the 1721. You'll peak the amp limit of the XLX2 with that setup long before you ever get there. Raz hit 192mph with the 1721 and that was running 8S parallel under perfect conditions with a little downhill and probably a little tail wind nudge.

Theoretical numbers are great. Realistic numbers are better.
 
Alright this video shows how poopy my throttle was. In the beginning of the video that's not a norm, I just happened to find the point on my throttle where there's not enough power to spin the gears. But regardless that shouldn't be able to happen once I'm on the throttle it should spin slowly which isn't happening it just goes fast as hell.


As you can see here much better the wheels are spinning very slowly and I've never seen that before as you can hear from my reaction.


And a new problem I found not sure why that's wobbling like that. First thing that came to mind was maybe I messed up when I changed my diff fluid. Maybe I'll open it up and see if there's anything going on. as you can see when i move the left wheel its very loose and flimsy. right wheel is much stiffer and you can hear the servo when I move it but only on the left side.


P.S I understand the car isn't under load so this will be different when I take it on the road.
 
I'm not thst good at explaining things nor do I know very much, but I think you should adjust your servo end points. When you turn left the angle of the steering post and servo linkage make a straight line. Adjust the end points so that the wheels don't turn so far that the linkage makes that straight line. Hopefully others will be able to help more. Bada$$ build you have though.
 
Alright this video shows how poopy my throttle was. In the beginning of the video that's not a norm, I just happened to find the point on my throttle where there's not enough power to spin the gears. But regardless that shouldn't be able to happen once I'm on the throttle it should spin slowly which isn't happening it just goes fast as hell.


As you can see here much better the wheels are spinning very slowly and I've never seen that before as you can hear from my reaction.


And a new problem I found not sure why that's wobbling like that. First thing that came to mind was maybe I messed up when I changed my diff fluid. Maybe I'll open it up and see if there's anything going on. as you can see when i move the left wheel its very loose and flimsy. right wheel is much stiffer and you can hear the servo when I move it but only on the left side.


P.S I understand the car isn't under load so this will be different when I take it on the road.
It not easy to tell in the video but from the way it looks to me, it seems like there's excessive play in the ball joint area which is causing the hub carriers to vibrate excessively. I could be wrong, that's just what I'm seeing in the video.

Take the wheel off and grab the hub carrier and check the top and bottom ball joint individually by pulling and pushing on the hub carrier and if the hub carrier is moving more than a quarter to half mm in any direction, I'd consider that excessive play/slop. The way I adjust mine is to just take the hub carrier with the ball joints installed in my hand and lightly snug down the ball joint plug so that it becomes difficult to move. Take the threaded end of the ball joint and set it so that it's pointed upwards and then back off the plug slowly. Stop at exactly the point where the threaded end of the ball joint falls. This should get you really close to the the tightest you can set it without causing binding.

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I'd also recommend getting some quality dry lube for use in your ball joints. Using oil or grease tends to attract lots and lots of dirt/dust/debris. I like to use two drops per ball of this stuff (If this isn't native to your geographic location, there are lots of other dry lube manufacturers and shouldn't be hard to come by). Add dry lube, rotate balls a couple of times (the double entendres of ball lubrication are fantastic btw) to distribute the lube and then let the alcohol carrier evaporate. Makes for much smoother balls imho that stay surprisingly clean. Just a thought.

But the first thing I'd do if I was you is install the sensor wires. Your car will run 10x smoother, that's not even hyperbole. Night and day aren't as different as some motors with and without sensor wire.
 
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First thin is I would disconnect the servo and make sure there it no play in the system.

With or without any play discovered, like @chris adams said, check your endpoints.

It looks like your steering geometry is a bit out of whack. Ideally you want two 90° angles for maximum throw. It looks like you have more left turn that right, but it doesn't matter much for speed runs. What does matter is that you don't over extend the geometry. You do this with servo endpoints.

When the link arm aligns with the bell crank (left pix) your at the fully extended limit. It just keeps pulling and oscillates back and forth until is settles, which may never happen. Going the other way it's jamming (left pix) the bell crank up against the physical limit. Neither situation is good for your servo or steering linkage.
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This is a very rough sketch to give you an idea of what I'm trying to say. Turning left, the link arm doesn't get longer (tension) and turning right it doesn't get shorter (compression).
1680417128810.png
 
First thin is I would disconnect the servo and make sure there it no play in the system.

With or without any play discovered, like @chris adams said, check your endpoints.

It looks like your steering geometry is a bit out of whack. Ideally you want two 90° angles for maximum throw. It looks like you have more left turn that right, but it doesn't matter much for speed runs. What does matter is that you don't over extend the geometry. You do this with servo endpoints.

When the link arm aligns with the bell crank (left pix) your at the fully extended limit. It just keeps pulling and oscillates back and forth until is settles, which may never happen. Going the other way it's jamming (left pix) the bell crank up against the physical limit. Neither situation is good for your servo or steering linkage.
View attachment 289990View attachment 289989

This is a very rough sketch to give you an idea of what I'm trying to say. Turning left, the link arm doesn't get longer (tension) and turning right it doesn't get shorter (compression).
View attachment 289993
Makes sense the only time im going to be turning that far is when im making a U-turn. Gonna keep it the way it is like the range of motion I don't want. struggle turning around
 
First thin is I would disconnect the servo and make sure there it no play in the system.

With or without any play discovered, like @chris adams said, check your endpoints.

It looks like your steering geometry is a bit out of whack. Ideally you want two 90° angles for maximum throw. It looks like you have more left turn that right, but it doesn't matter much for speed runs. What does matter is that you don't over extend the geometry. You do this with servo endpoints.

When the link arm aligns with the bell crank (left pix) your at the fully extended limit. It just keeps pulling and oscillates back and forth until is settles, which may never happen. Going the other way it's jamming (left pix) the bell crank up against the physical limit. Neither situation is good for your servo or steering linkage.
View attachment 289990View attachment 289989

This is a very rough sketch to give you an idea of what I'm trying to say. Turning left, the link arm doesn't get longer (tension) and turning right it doesn't get shorter (compression).
View attachment 289993
It's not so much that the steering geometry is out of whack as this setup is almost a carbon copy of one of Raz's builds from 2021. The second motor forces a lateral displacement of the servo necessitating a diagonally oriented connector from servo horn to servo saver.

To my mind a lot of the anomalous behavior we're seeing at the wheel stems from running moderately high gearing on these motors in an un-sensored array. It would behave much differently at a stock 15/46 gearing but, as it stands, this is not the setup for crawling the wheels at 60rpm.
 
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