Limitless Project Downforce for VTe2 and Limitless

This site may earn a commission from merchant affiliate
links, including eBay, Amazon, and others.
https://www.thingiverse.com/thing:5202601

1669829422167.png
 
On Sunday I did a little parking lot drive and tested the rear wing. I cut together some "highlights" and a little comparison of the different driving behaviors with and without the wing. Hope you find it interesting (y)



View attachment 259706

Time to get me some goose neck....
wings!
 
On Sunday I did a little parking lot drive and tested the rear wing. I cut together some "highlights" and a little comparison of the different driving behaviors with and without the wing. Hope you find it interesting (y)



View attachment 259706
Looks fun. Ideally if you could do repeat runs with the car at 100% around a high speed turn and compare the setups. A GoPro hero5 or newer will show speed and G-force to compare the data.
 
Looks fun. Ideally if you could do repeat runs with the car at 100% around a high speed turn and compare the setups. A GoPro hero5 or newer will show speed and G-force to compare the data.
That's exactly how I want to test. But I don't have a GoPro for telemetry. So maybe compare the times through the turn via my (runcam thumb pro) footage.
And I could try setting the skyrc GPS to a 100-meter run, then I would have a graph of the speed I was doing.
Is there any way to measure G-force without a GoPro?

I actually prefer swan necks and chicken wings...;)
 
That's exactly how I want to test. But I don't have a GoPro for telemetry. So maybe compare the times through the turn via my (runcam thumb pro) footage.
And I could try setting the skyrc GPS to a 100-meter run, then I would have a graph of the speed I was doing.
Is there any way to measure G-force without a GoPro?

I actually prefer swan necks and chicken wings...;)
The reason the GoPro would be nice is that on video you could see entry speed into the turn and exit speed which would be helpful. (along with the g-meter)
I am not certain how you could capture similar data with another device although I am sure they exist. I think the SkyRC only captures g-meter for drag runs and likely wouldn't work out for this use case.
 
The reason the GoPro would be nice is that on video you could see entry speed into the turn and exit speed which would be helpful. (along with the g-meter)
I am not certain how you could capture similar data with another device although I am sure they exist. I think the SkyRC only captures g-meter for drag runs and likely wouldn't work out for this use case.
What about something like this?
https://apps.apple.com/us/app/g-force/id287193619
1669998838794.png
 
Quick update: New front wing, tiny middle rear diffuser ( plan on building the outer sections with tape and chopsticks) In the simulations the outer parts of the diffuser were not creating much downforce at all.

And some wing force leverage testing. With chopsticks taped under the chassis, where the wheel would touch the ground. So that the placement on the scales and suspension movement does not matter.

Base weight over the front axle is 2288g
1kg downforce on the FW adds +1359g on the front axle. So 359g due to leverage.
1kg on the rear wing leads to 2121g on the f axle. So the missing 167g are added to the rear axle due to leverage.
So since the front wing is further away from the front axle it does not have to generate just as much downforce as the rear wing, because the leverage is helping here more.



IMG_20221212_145623.jpg

Here 1kg is placed on the rear wing.



IMG_20221212_145606.jpg

Here 1kg on the front wing



IMG_20221212_145554.jpg

No 1kg weight added.

IMG_20221212_200839.jpg


IMG_20221212_200906.jpg
 
Hey I just wanted to give some updates after a couple of months and (only) one driving session with the vte2 due to bad weather.

I tried to measure g forces with my old smartphone but there were too many vibrations, at least when taped to the rear diffuser. Will try it in a different spot maybe...

The front wing produced too little downforce and I still had understeer. Instead of sanding the wing and making the surface smooth, I went ahead and printed a new front-wing. :)

IMG_20230228_193209.jpg


Towards the end of the run, the 1717 reached 66 degrees Celsius. So I now installed a 4010 fan and a passive heatsink on the end of the motor can:unsure:.
IMG_20230227_093806.jpg


And I added a cinema camera setup on the center brace, one for HD footage, one for FPV driving.
IMG_20230212_123613.jpg


Maybe I will try the tougher carbon fiber when I crash my brittle 3D plastics. But so far they have survived(y).

And I made some silicone o ring dampened 3d printed bump stops to stop the car from bottoming out so hard.
I am thinking about adding a cap pack. It reached 2v ripple voltage at one point. And the car suddenly went 127kmh instead of 120 at just slightly warmer lipo temps then the three runs at 120 before that:unsure:.

Now I just want to protect the esc a little with the caps. I already soldered a 50v pack but now I think I should have gone with more 35v capacitors instead.
Some strange soldering:
IMG_20230224_121846.jpg


My FR 35v 680uF 18 m ohm 2470mA ripple current 3g weight(10times) would have been better probably:mad:
My panasonic FM-A 50v 680uF 16 m ohm 3160mA ripple current 5,6g weight (6times)

IMG_20230228_201605.jpg


Is the cap pack overkill? For 2v ripple?
 
Last edited:
I came across this when doing some research on the forum. What FM Panasonic caps did you use?

And what is the voltage rating all about? 35v seems still ok for 8s lipo since castle uses them...
But I bought 50v caps because I read in a FPV copter guide that they use 35v minimum for 6s and 50v minimum for 8s. :unsure: Or is 35volts ok since we use higher capacitance in the cars than in the drones.


https://oscarliang.com/capacitors-mini-quad/#Capacitor-Gets-Hot-After-Flight
 
I came across this when doing some research on the forum. What FM Panasonic caps did you use?

And what is the voltage rating all about? 35v seems still ok for 8s lipo since castle uses them...
But I bought 50v caps because I read in a FPV copter guide that they use 35v minimum for 6s and 50v minimum for 8s. :unsure: Or is 35volts ok since we use higher capacitance in the cars than in the drones.


https://oscarliang.com/capacitors-mini-quad/#Capacitor-Gets-Hot-After-Flight

One thing I have noticed is that the voltage moves around and sometimes spikes over the voltage of the batteries. Always good to have some headroom. The general issue is finding space on the chassis but your GT Chassis there should have plenty of room.
 
Hey, short update:
I made a 35v cap pack 9x 680uF Fm panasonic.

And a new suspension mounted diffuser. It has extra long vertical strakes to shield the diffuser from tire turbulence.
However, I am not sure wether it produces meaningful downforce.

View attachment 289492

View attachment 289493

View attachment 289494
I feel ya. Without a proper Venturi tunnel I have my my own questions as to the effectiveness of diffusors in terms of generating downforce on these RC cars. If I'm not mistaken, neither James McCoy nor Tony Ingalls run diffusors on their GT cars.
 
Hey, short update:
I made a 35v cap pack 9x 680uF Fm panasonic.

And a new suspension mounted diffuser. It has extra long vertical strakes to shield the diffuser from tire turbulence.
However, I am not sure wether it produces meaningful downforce.

View attachment 289492

View attachment 289493

View attachment 289494

That turned out really nice! It appears your angle is far more realistic than the 25 deg. that Arrma used on the Limitless/Infraction/Felony.

I am in that same school of thought that the air gap under the car is too tight to allow enough airflow. There will be a boundary layer interaction with the bottom of the car and another with the ground. I don't think there is enough gap between those two for an under-car venturi to be useful.

BUT I have been wrong before 🤔
 
@Lennart Don't worry about the 1717. You hear about all the 5 people that grenaded them but you don't hear about the 10,000 people that haven't had any issues.

I've run my at 55K RPM for speed runs with no issues, with that said, it could blow into pieces at any time. But it is what it is and I will run it till it doesn't work anymore. It's not something I worry about. Would I bash with tall gears and high RPM - ah probably not.

As for the temp 65°C is fine and shouldn't be even close to anything damaging. There's also a difference between running temp and resting (storage) temp. When I do a speed run, I might see 75-80°C when the run is done. If I let it sit, the temp gets much higher which tells me the temp sensor is starting to read the true temperature or the sensor is out of range and doing weird stuff. Either way it's just sitting there with no stress on it.

Their isn't much in the motors (magnets, coils and some sensors) I don't believe it's an electronics issue. Which leads me to believe the temperature issue (others pleases chime in) is mechanical. The first is the bearings and lubrication. The second is the thermal expansion. The third might be any insulation or bonding material thermal limits. But, again hot is different than hot under stress.

BTW I'm sure (or at least I hope) that Castle tests every motor that goes out the door for max RPM to make sure it doesn't fly a part.
 
That turned out really nice! It appears your angle is far more realistic than the 25 deg. that Arrma used on the Limitless/Infraction/Felony.

I am in that same school of thought that the air gap under the car is too tight to allow enough airflow. There will be a boundary layer interaction with the bottom of the car and another with the ground. I don't think there is enough gap between those two for an under-car venturi to be useful.

BUT I have been wrong before 🤔
Yeah, but not since 1982.
@Lennart Don't worry about the 1717. You hear about all the 5 people that grenaded them but you don't hear about the 10,000 people that haven't had any issues.

I've run my at 55K RPM for speed runs with no issues, with that said, it could blow into pieces at any time. But it is what it is and I will run it till it doesn't work anymore. It's not something I worry about. Would I bash with tall gears and high RPM - ah probably not.

As for the temp 65°C is fine and shouldn't be even close to anything damaging. There's also a difference between running temp and resting (storage) temp. When I do a speed run, I might see 75-80°C when the run is done. If I let it sit, the temp gets much higher which tells me the temp sensor is starting to read the true temperature or the sensor is out of range and doing weird stuff. Either way it's just sitting there with no stress on it.

Their isn't much in the motors (magnets, coils and some sensors) I don't believe it's an electronics issue. Which leads me to believe the temperature issue (others pleases chime in) is mechanical. The first is the bearings and lubrication. The second is the thermal expansion. The third might be any insulation or bonding material thermal limits. But, again hot is different than hot under stress.

BTW I'm sure (or at least I hope) that Castle tests every motor that goes out the door for max RPM to make sure it doesn't fly a part.
It seems like the 1717 you get is either going to fail early or live forever if I take a cross section of the reports of people's experience with their 1717. But I'm with you on the reporting bias. I've made the same argument in previous threads. It appears as though we hear a lot more about grenading motors but, yeah....that's just kind of obvious. Most content providers/creatos don't post videos titled, "Yep, motor still works". Parts failure is just a natural spectator sport of most tech oriented hobbies.

What you're seeing with your temps creeping up with the car at rest is the core temperature moving outwards. The temp your sensor is reading at the end of the run is only showing how much of the heat has made it to the skin of the can. It's a couple of degrees hotter at the core and it takes 5-10 minutes before the indicated temperature levels off, stabilizes and returns to closer to normal operating temperature. Your sensor isn't malfunctioning, it's simply a matter of delayed thermal propagation.

The problem with high temperatures are the magnets. How high you can go with your temps will depend on the chemical composition of the neodymium that are in your motor. If you look around the net you'll find a variety of listed max temps for neodym magnets ranging from 80-100°C and some even listing max working temps of 200°C (though I'm pressing "x" to doubt on that....not saying that's impossible, only that taking most motors beyond 100°C is almost certain to, at least partially, damage the magnetization, possibly rendering the motor useless in a worst case scenario). That being said, I've heard of people accidentally taking their motor into the 140-150°C range briefly and living to tell the tale, though at that point I'd be willing to bet that the motor took at least some permanent damage to its magnetization.
 
Old Thread: Hello . There have been no replies in this thread for 90 days.
Content in this thread may no longer be relevant.
Perhaps it would be better to start a new thread instead.
Back
Top