Limitless The ideal body for speed runs

[LibertyMKiii]

As most of you know I have been attempting to build the ideal body for speedrunning. I thought it would be fun to discuss what an ideal speed run body needs and what it could/should look like.

There are 3 primary focus points for the ideal speed body.
1. Enough downforce to get traction with the 15+ horsepower outputs of the 8s systems. Plus foams need significantly more downforce to find traction.
2. Low drag but also must not flip at high speeds. (so some drag is absolutely necessary to keep the front pinned down)
3. Stiff body that does not flex, which would change the downforce mid-run. (or must be reinforced)

The original example and gold standard was Nic Case's RC bullet which set the RC wheel-driven speed record of 202 mph all those years ago. It is clear to see the front end generates massive downforce! The rear vertical tail has a small silver integrated airfoil for rear downforce. (also aerodynamically hides most of the antenna)

Interestingly enough he had previously tried some more rounded designs that didn't go well like the SR11. It seemed to flip often at 170-180 mph. I should have paid closer attention to that fact when I went on to make bodies rather similar to this that had the same issue.

I'll start by sharing what I have done over the past few years. (does not mean I was right and a few examples were proven to be very wrong)

My first attempt began with a hand-sculpted design for the Unlimited project.
This body design actually is probably the best one I ever have created, now looking back at it with some 20/20 hindsight.

The issue with the Unlimited body was that being hand sculpted it was not 100% symmetrical. The front had one side with a different curvature than the other and I know this would be catastrophic for the car at speeds above 100 mph. I always took my pictures at an angle where it was not very visible

Later I purchased a 3D printer from some of the proceeds of the sale of the Unlimited project. This would allow me to create more accurate molds/plugs for body creation.

The next version was similar but considerably more rounded and smooth. I refer to this as the "Long Nose" 7th scale body.
It generated great frontal downforce. Raz attempted this one many times and had issues with the car fishtailing. It may be worth re-visiting and just needs a rear wing? He was also snapping front axles often, which could have been due to the lack of rear traction? Still a bit of a mystery and could use some more exploring...

Thinking that the long nose body's issue was excessive downforce and looking at designs of well-functioning RC bodies like the 917 and Dome bodies I decided to change the front end significantly while retaining the same mid and rear of the body.

This design proved to not have enough downforce as Raz and another top-name speed runner both confirmed it would flip around 150-160 mph. Now, with that said..... both of them removed the front splitter that was integrated into the body, which removed a significant amount of front downforce. Regardless, it could use more front-downforce and absolutely must have some rear wing to provide rear downforce also. This design I put through some simulations and has extremely low drag, but just not enough downforce as needed for an 8-second blast to insane speeds.

Then a combination of things occurred. James McCoy started testing some new batteries and motors and took the 1/7 scale platform to speeds none of us expected. He did this with the Delta Plastiks 1/7 Ford FC100 body.

This body currently has been 204 mph piloted by James and has some really great design features. Raz and some others have been in the 190-200 mph range with this same body also.
Key features of this body:
1. High downforce front end, but not too much drag.
2. Side channels to control airflow and help alleviate high air pressure zones from washing into low-pressure zones.
3. Built-in rear wing (can be hard to see, but is visible in my plaster copy of the body)

I have a small project going to modify this body because it just works and could be improved slightly.
I never modified the rear, you can see the rear kick-up that acts like a rear wing.
The changes I had made were to smooth out the vents, wheel arches, fake lights, etc. Clearly, I removed a majority of the driver's canopy and streamlined those areas. It cannot be fully removed without making the transition from the hood to harsh.
The other thing I did was remove the rear vertical fins because they would be re-created in a carbon fiber plate after the body is made. They wouldn't mold well and would be impossible to repair a tight internal void in the mold if something went wrong.

I may re-visit finishing the body in the winter when it is not 100 degrees in the garage!!!!

Currently, I am a bit sidetracked working on revising my blunt nose body so that I can utilize it on my 1/7 scale Hobao VTE2 project car. I was chatting with James McCoy about the front and he agreed I need to fix the nose to increase downforce. I wanted to take advantage of the 2 I have in the garage so I have begun modifying the nose and will be ultimately wrapping it with Vinyl so it won't be visible what was done underneath anyway.

I am borrowing some design ideas from the FC100 with some front air guides that will run along the top of the body. These force the air to stay in that area retaining some high pressure downforce creation there over the nose.

I started re-shaping the nose with some loctite expanding foam. I use painters tape to help control where it goes and it won't stick to the blue painter's tape

Now I have applied some body filler over this so I can sand it smoothly to transition into the carbon body without a seam. Then I'll wrap it up with Vinyl that is bright for visibility....
I believe this mod along with a wing will get this body performing the way it needs to be!!!! (fingers crossed)

All of this also has me thinking that my 200+ project body needs more front-end downforce also, which I will need to modify. Currently, I am thinking about some small wings that would extend out of the front of the body to aid in front downforce generation. (mostly because I love the shape and don't want to hack it up too much)

I have been hyperfocus on aerodynamic drag and didn't give enough attention to downforce generation, but enough about my failed attempts LOL

What are your thoughts and what have you tried or thought about trying? Open to hearing your thoughts on what I could do to improve these designs I have or talk about your body and what could be done to help it out.

 

[Hector_Fisher]

Disclaimer: i have not attempted serious speed running.

The designs i'm seeing here are in line with whats been done before, including what you see on 1:1 land speed record cars. However, as you pointed out, James' latest showed that there is not necessarily one ideal body for speed running. I think that's the key point.

I think you're going in the right direction: you understand the point is to design a body anticipating that the aerodynamic effects on the car are different for any given speed. Your latest seems to have addressed the issues you're foreseeing. The challenge is understanding what those affects are. You'll either have to do some incremental field testing or bolster your confidence with some other set of engineering data. Access to a wind tunnel would be an awesome help. Otherwise, you could go the CFD route (simulated fluid flow) in order to gauge stability at various speeds. There are open source options out there for CFD, such as OpenFOAM.

When i do get into speed running, my biggest desire is to delve into active-aero and speed/force driven, servo operated aerodynamics, running some sort of logic board with gyro/speedo sensors.

 

[LibertyMKiii]

Disclaimer: i have not attempted serious speed running.

The designs i'm seeing here are in line with whats been done before, including what you see on 1:1 land speed record cars. However, as you pointed out, James' latest showed that there is not necessarily one ideal body for speed running. I think that's the key point.

I think you're going in the right direction: you understand the point is to design a body anticipating that the aerodynamic effects on the car are different for any given speed. Your latest seems to have addressed the issues you're foreseeing. The challenge is understanding what those affects are. You'll either have to do some incremental field testing or bolster your confidence with some other set of engineering data. Access to a wind tunnel would be an awesome help. Otherwise, you could go the CFD route (simulated fluid flow) in order to gauge stability at various speeds. There are open source options out there for CFD, such as OpenFOAM.

When i do get into speed running, my biggest desire is to delve into active-aero and speed/force driven, servo operated aerodynamics, running some sort of logic board with gyro/speedo sensors.

I had thought about doing something like that also. If you do experiment with such a build consider building it similar to how the front steering posts work on the front of RC cars (where the wing is not pushing directly on the servo. )

Based on my experience I would say that you need the 100% high downforce nearly full time. The acceleration phase by your throttle is around 8 seconds and once at full throttle, it is still accelerating for another 2-3 seconds. At that point, it is time to hit the brakes and you need the downforce again, so it may not be worth all the effort considering you need it pretty much the full time except for maybe 2 seconds of the run. Another factor is upsetting the car's balance at those speeds.

I'd imagine you want to cut your teeth running 100% downforce and reach some high speeds first. Then see how a controller might help.
Getting to that point takes years of speed running....

 

[Hector_Fisher]

I had thought about doing something like that also. If you do experiment with such a build consider building it similar to how the front steering posts work on the front of RC cars (where the wing is not pushing directly on the servo. )

Based on my experience I would say that you need the 100% high downforce nearly full time. The acceleration phase by your throttle is around 8 seconds and once at full throttle, it is still accelerating for another 2-3 seconds. At that point, it is time to hit the brakes and you need the downforce again, so it may not be worth all the effort considering you need it pretty much the full time except for maybe 2 seconds of the run. Another factor is upsetting the car's balance at those speeds.

I'd imagine you want to cut your teeth running 100% downforce and reach some high speeds first. Then see how a controller might help.
Getting to that point takes years of speed running....

Exactly, my thought was to design a passively high downforce wing (or splitter, etc) that the servo could ease up on based around certain parameters or conditions. Creating active aero dynamics that are passively neutral would, like you said, rely solely on the strength of the servo to hold steady, which isn't that robust of a system (as you can see with "neutral steering" that you can usually still physically turn even when the servo is holding true).

To be fair, i'm only hypothesizing and dreaming here since i still need to make an official foray into speed running. Does my project to build an HPI Bullet to run on 8s count as speed running???

You should know yourself it doesn't take long to get into the speed running hobby; it only takes around 8 seconds or so! The trick is being able to come back from that speed run and do it again... that's where the years of experience plays into!!!

 

[Notoriousone]

As far as what speedrun bodies are readily available, overall I think the FC100 with its huge front end downforce would probably be the best. I have run this body many times, never past 140mph but fast enough to see a difference in how it really keeps the front down compared to other bodies, to the point where it rubs the front tires and the nose skims the ground more than other bodies.. I have to run the front higher and firm up the front shocks to somewhat compensate for this downforce but I think this is actually a good thing. Under hard acceleration on a 20hp full throttle speedrun I think the rearward shift of the cars CG would work toward balancing out the front downforce, but not be enough to cause a blowover or at least less of a chance of one compared to other bodies. Of course this is just my guess, I have no way of knowing for sure and there would be plenty of other variables as well. I would love to see some real wind tunnel data on these bodies, though I know due to cost of such things this would probably never happen

 

[LibertyMKiii]

Exactly, my thought was to design a passively high downforce wing (or splitter, etc) that the servo could ease up on based around certain parameters or conditions. Creating active aero dynamics that are passively neutral would, like you said, rely solely on the strength of the servo to hold steady, which isn't that robust of a system (as you can see with "neutral steering" that you can usually still physically turn even when the servo is holding true).

To be fair, i'm only hypothesizing and dreaming here since i still need to make an official foray into speed running. Does my project to build an HPI Bullet to run on 8s count as speed running???

You should know yourself it doesn't take long to get into the speed running hobby; it only takes around 8 seconds or so! The trick is being able to come back from that speed run and do it again... that's where the years of experience plays into!!!

Not sure the HPI bullet is the best platform to use, but then again I took a Kraton 6s to 96 mph

There is no replacement for that behind-the-wheel feeling of knowing what the car is doing and when to get out of the throttle. That just comes with time and experience. Trying to go fast before you are ready for it cost big money in crashes. I know that first hand trying to run 8s in a Typhon before I had ever gone above 100 mph. Now we are doing 120+ on 3s. So foolish was I

There are so many small details that go into this segment of the hobby. It is incredibly technical and I absolutely love it!!!!!

As far as what speedrun bodies are readily available, overall I think the FC100 with its huge front end downforce would probably be the best. I have run this body many times, never past 140mph but fast enough to see a difference in how it really keeps the front down compared to other bodies, to the point where it rubs the front tires and the nose skims the ground more than other bodies.. I have to run the front higher and firm up the front shocks to somewhat compensate for this downforce but I think this is actually a good thing. Under hard acceleration on a 20hp full throttle speedrun I think the rearward shift of the cars CG would work toward balancing out the front downforce, but not be enough to cause a blowover or at least less of a chance of one compared to other bodies. Of course this is just my guess, I have no way of knowing for sure and there would be plenty of other variables as well. I would love to see some real wind tunnel data on these bodies, though I know due to cost of such things this would probably never happen

100% agree
I love the FC100 body. It manages to give you the best downforce without being slow in any way. It is really great!

I think for an absolute newb the 917 body is really good for stability and downforce, but you won't go as fast because the downforce is even higher than the FC100.

Maybe one day I can build a wind tunnel test setup. I would be the guy crazy enough to do it LOL

 

[Hector_Fisher]

Not sure the HPI bullet is the best platform to use, but then again I took a Kraton 6s to 96 mph

There is no replacement for that behind-the-wheel feeling of knowing what the car is doing and when to get out of the throttle. That just comes with time and experience. Trying to go fast before you are ready for it cost big money in crashes. I know that first hand trying to run 8s in a Typhon before I had ever gone above 100 mph. Now we are doing 120+ on 3s. So foolish was I

There are so many small details that go into this segment of the hobby. It is incredibly technical and I absolutely love it!!!!!

I know it's not the best platform--and that's kind of the appealing challenge. i'm currently running on 4s on the Bullet and geared for 60ish and i've slowly built up speeds to full throttle. There are definitely issues i'm seeing that I need to correct for higher speed, but that's part of the fun in this hobby; and specifically in speed running. I have no lofty goals or anything, and I'm not honestly expecting to break 100, just kind of experiment along the way and see what happens.

That technical side you mention is certainly what's pulling me in to speed running!

In a way, it will likely be similar to your OP. The best approach will never be stick power in a car and slam the trigger, but slow incremental additions of power/speed and observing the changes that occur so you can accommodate or change as necessary. The hard thing to predict, like you mentioned, will be the sudden dynamic shifts, like a blow over at 150mph...

 

[K-BASH]

Could a wind tunnel be made using smoke to see how an what the air does over the body,turbulence,restrictions.....1 thing I've learned from this hobby is that ANYTHING CAN BE DONE......4ft Dia. Smooth culvert pipe,5 smoke machines,fan that blows upto 150mph

 

[jondilly1974]

What about something that flexes under high speeds but gives downforce at lower speeds? Imagine an airfoil on a spring. It would produce drag and downforce until a certain load and then flatten out at higher speeds. Just a thought

 

[Hector_Fisher]

Could a wind tunnel be made using smoke to see how an what the air does over the body,turbulence,restrictions.....1 thing I've learned from this hobby is that ANYTHING CAN BE DONE......4ft Dia. Smooth culvert pipe,5 smoke machines,fan that blows upto 150mph

But seriously, getting a tunnel with 150mph would not be nearly as challenging as getting clean laminate air flow to simulate what you'd be passing through with the RC. If you use straight fan air, it would be too turbulent and unpredictable to provide any meaningful data.

What about something that flexes under high speeds but gives downforce at lower speeds? Imagine an airfoil on a spring. It would produce drag and downforce until a certain load and then flatten out at higher speeds. Just a thought

That was my first thought. Something that flattens down at higher speeds, and it would definitely be a simple system with some sort of progressive spring coil.

My end goal would be active aero that could react to sudden changes in airflow or car movement and compensate accordingly. Something with the passive state being way higher than normally needed levels of down force so that in the event the car begins to blow over, the logic board could react by applying maximum down force to counter the lift. But this is all just deep space dreaming for me at this point

 

[LibertyMKiii]

I know it's not the best platform--and that's kind of the appealing challenge. i'm currently running on 4s on the Bullet and geared for 60ish and i've slowly built up speeds to full throttle. There are definitely issues i'm seeing that I need to correct for higher speed, but that's part of the fun in this hobby; and specifically in speed running. I have no lofty goals or anything, and I'm not honestly expecting to break 100, just kind of experiment along the way and see what happens.

That technical side you mention is certainly what's pulling me in to speed running!

In a way, it will likely be similar to your OP. The best approach will never be stick power in a car and slam the trigger, but slow incremental additions of power/speed and observing the changes that occur so you can accommodate or change as necessary. The hard thing to predict, like you mentioned, will be the sudden dynamic shifts, like a blow over at 150mph...

I noticed in another thread about motors that you have a mind for technical thinking. I think speed running is a great rabbit hole to journey if and only if you have good roads. Even still it is a gigantic money pit so just be ready for that!

Originally I thought the battle could be won with superior aerodynamics. I underestimated just how much downforce these cars need. It is a crazy amount!!!! My VTE2 with the FC100 body scrapes the ground above 110 mph until I added the fuel tubing shock travel limiters. So now it is just pushed down as far as my suspension will allow.

Regarding @jondilly1974 's idea of a flexible wing, it could work. Even carbon fiber at the right thickness would be an ideal candidate. My concern is that the power comes on heavy after 50% throttle. You really need optimal downforce nearly the whole time. For something like this you could probably use a leaf blower to confirm it flexes at high airspeeds.

If someone gets serious about wind tunnel ideas I have done a significant amount of research and planning to build one that would take up a majority of your 2 car garage. It uses large industrial fans that move some serious CFM and the narrowing down of the airflow through the test section gets the airspeed up to 160+ mph as needed. I also already planned how to make the airflow straighten out via thousands of tubes. Eagle tree went under a few years ago, but they had a nice RC plane telemetry setup that would measure air speed with a pitot tube. I'll have to search for another solution on airspeed measurement.

The biggest challenge would be accurately measuring the downforce and drag while on a moving belt/treadmill. Without the treadmill, you cannot correctly measure ground effect and ground boundary layer airflow aspects that occur under the car while moving along the road at speed.

The whole thing becomes an extremely large and expensive project. If we end up moving and we can afford a place with a 3rd car garage or a massive basement then I'd be game for starting a scale wind tunnel build

 

[Tex Koder]

What about something that flexes under high speeds but gives downforce at lower speeds? Imagine an airfoil on a spring. It would produce drag and downforce until a certain load and then flatten out at higher speeds. Just a thought

or just a piece of mild spring steel ,shaped into an airfoil to begin with..

But seriously, getting a tunnel with 150mph would not be nearly as challenging as getting clean laminate air flow to simulate what you'd be passing through with the RC. If you use straight fan air, it would be too turbulent and unpredictable to provide any meaningful data.

That was my first thought. Something that flattens down at higher speeds, and it would definitely be a simple system with some sort of progressive spring coil.

My end goal would be active aero that could react to sudden changes in airflow or car movement and compensate accordingly. Something with the passive state being way higher than normally needed levels of down force so that in the event the car begins to blow over, the logic board could react by applying maximum down force to counter the lift. But this is all just deep space dreaming for me at this point

Unless you use a* blower design like the Dyson "purifier" fan [laid on it's side parallel to the surface of your wind tunnel].
It can produce a stream of air with very little turbulence >

* or several of them.

 

[Tex Koder]

@LibertyMKiii

I'm getting ready to start a print of your "LN" design..

Will see how it turns out ,with 1 layer wall thickness...

I'll probably print at 50% scale first.. see how it turns out and save on time & filament.





***********************************************************************************************************************************

...

I may re-visit finishing the body in the winter when it is not 100 degrees in the garage!!!!

Currently, I am a bit sidetracked working on revising my blunt nose body so that I can utilize it on my 1/7 scale Hobao VTE2 project car. I was chatting with James McCoy about the front and he agreed I need to fix the nose to increase downforce. I wanted to take advantage of the 2 I have in the garage so I have begun modifying the nose and will be ultimately wrapping it with Vinyl so it won't be visible what was done underneath anyway.

I am borrowing some design ideas from the FC100 with some front air guides that will run along the top of the body. These force the air to stay in that area retaining some high pressure downforce creation there over the nose.

View attachment 230698

I started re-shaping the nose with some loctite expanding foam. I use painters tape to help control where it goes and it won't stick to the blue painter's tape

View attachment 230699

Now I have applied some body filler over this so I can sand it smoothly to transition into the carbon body without a seam. Then I'll wrap it up with Vinyl that is bright for visibility....
I believe this mod along with a wing will get this body performing the way it needs to be!!!! (fingers crossed)

All of this also has me thinking that my 200+ project body needs more front-end downforce also, which I will need to modify. Currently, I am thinking about some small wings that would extend out of the front of the body to aid in front downforce generation. (mostly because I love the shape and don't want to hack it up too much)

View attachment 230700

I have been hyperfocus on aerodynamic drag and didn't give enough attention to downforce generation, but enough about my failed attempts LOL

What are your thoughts and what have you tried or thought about trying? Open to hearing your thoughts on what I could do to improve these designs I have or talk about your body and what could be done to help it out.

PS:
If you need vinyl to wrap your modified CF shells..
Just let me know, I still have quite a bit of stock from my vinyl making days..

 

[LibertyMKiii]

@LibertyMKiii

I'm getting ready to start a print of your "LN" design..

View attachment 230767


Will see how it turns out ,with 1 layer wall thickness...

View attachment 230770


I'll probably print at 50% scale first.. see how it turns out and save on time & filament.





***********************************************************************************************************************************



PS:
If you need vinyl to wrap your modified CF shells..
Just let me know, I still have quite a bit of stock from my vinyl making days..

I used to always print them with some small amount on infill so the body holds the correct shape. Something like 3% was plenty for that.
I ordered some neon orange vinyl off Amazon that looks pretty cool for high visibility. Also I have that gold chrome seen in the photos above.

 

[Tex Koder]

I used to always print them with some small amount on infill so the body holds the correct shape. Something like 3% was plenty for that.
I ordered some neon orange vinyl off Amazon that looks pretty cool for high visibility. Also I have that gold chrome seen in the photos above.

For testing..
I like to leave it at 0% infill, I like to live on the edge

 

[Hector_Fisher]

I noticed in another thread about motors that you have a mind for technical thinking. I think speed running is a great rabbit hole to journey if and only if you have good roads. Even still it is a gigantic money pit so just be ready for that!

Originally I thought the battle could be won with superior aerodynamics. I underestimated just how much downforce these cars need. It is a crazy amount!!!! My VTE2 with the FC100 body scrapes the ground above 110 mph until I added the fuel tubing shock travel limiters. So now it is just pushed down as far as my suspension will allow.

Regarding @jondilly1974 's idea of a flexible wing, it could work. Even carbon fiber at the right thickness would be an ideal candidate. My concern is that the power comes on heavy after 50% throttle. You really need optimal downforce nearly the whole time. For something like this you could probably use a leaf blower to confirm it flexes at high airspeeds.

If someone gets serious about wind tunnel ideas I have done a significant amount of research and planning to build one that would take up a majority of your 2 car garage. It uses large industrial fans that move some serious CFM and the narrowing down of the airflow through the test section gets the airspeed up to 160+ mph as needed. I also already planned how to make the airflow straighten out via thousands of tubes. Eagle tree went under a few years ago, but they had a nice RC plane telemetry setup that would measure air speed with a pitot tube. I'll have to search for another solution on airspeed measurement.

The biggest challenge would be accurately measuring the downforce and drag while on a moving belt/treadmill. Without the treadmill, you cannot correctly measure ground effect and ground boundary layer airflow aspects that occur under the car while moving along the road at speed.

The whole thing becomes an extremely large and expensive project. If we end up moving and we can afford a place with a 3rd car garage or a massive basement then I'd be game for starting a scale wind tunnel build

A flexible wing might work, but may also "flap" depending on the circumstances. You'd need some more testing for that idea. A rigid splitter or wing that is spring hinged (or something to that effect) would likely work better, provide more consistent performance, and be more tunable (dampening may be key here to prevent flap).

The funny thing is, if you were to get a tunnel up and running, you'd probably be doing more actual RC engineering/testing than TRX and Arrma.

Agreed that a wind tunnel alone would provide data on downforce, but not accurately show what ground effects. Now we're looking at a treadmill capable of 200mph! It's more of a dream than anything for me. Knowing I had access to a wind tunnel back in my college days and didn't really understand how cool that was makes me want to kick myself.

Like you said before, there is no substitute for testing and time with rubber on the road. I think the incrementally increasing speed tests combined with some supplementary data should increase confidence of a platforms stability.

One thing I'd like to do is become more familiar with lidar scans so I can automatically build 3d meshes for fluid flow simulation. That would be useful for modelling any RC. That might give more insight as to why the kraton wants to rocket to the moon after 70mph.

Dang it @Tex Koder , i've already got a drill press on my list of big tools in the garage, stop making me want to get a printer!!!

 

[LibertyMKiii]

A flexible wing might work, but may also "flap" depending on the circumstances. You'd need some more testing for that idea. A rigid splitter or wing that is spring hinged (or something to that effect) would likely work better, provide more consistent performance, and be more tunable (dampening may be key here to prevent flap).

The funny thing is, if you were to get a tunnel up and running, you'd probably be doing more actual RC engineering/testing than TRX and Arrma.

Agreed that a wind tunnel alone would provide data on downforce, but not accurately show what ground effects. Now we're looking at a treadmill capable of 200mph! It's more of a dream than anything for me. Knowing I had access to a wind tunnel back in my college days and didn't really understand how cool that was makes me want to kick myself.

Like you said before, there is no substitute for testing and time with rubber on the road. I think the incrementally increasing speed tests combined with some supplementary data should increase confidence of a platforms stability.

One thing I'd like to do is become more familiar with lidar scans so I can automatically build 3d meshes for fluid flow simulation. That would be useful for modelling any RC. That might give more insight as to why the kraton wants to rocket to the moon after 70mph.

Dang it @Tex Koder , i've already got a drill press on my list of big tools in the garage, stop making me want to get a printer!!!

You will absolutely need the 3d printer when you want to start creating things and testing various shapes. The key for RC applications is having it large enough. Most of the RC bodies I made were printed in 6 large pieces.

I cannot tell you how many times something looked right in CAD and then when I had it physically in my hands 3d printed I realized it needed to be changed. Especially with parts like wings or other small components.

 

[Hector_Fisher]

You will absolutely need the 3d printer when you want to start creating things and testing various shapes. The key for RC applications is having it large enough. Most of the RC bodies I made were printed in 6 large pieces.

View attachment 230818


I cannot tell you how many times something looked right in CAD and then when I had it physically in my hands 3d printed I realized it needed to be changed. Especially with parts like wings or other small components.

View attachment 230820

Any recommendations then????

 

[LibertyMKiii]

Any recommendations then????

The go-to seems to be the Creality Ender 3, which has available some large print bed upgrades.
I have the Creality CR10s pro, but I wish I had asked around and bought the Ender 3. We actually have a 3d printing section of the forum and some good discussions have been had there if you want to do some research on it.

 

[Tex Koder]

A flexible wing might work, but may also "flap" depending on the circumstances. You'd need some more testing for that idea. A rigid splitter or wing that is spring hinged (or something to that effect) would likely work better, provide more consistent performance, and be more tunable (dampening may be key here to prevent flap).

You're correct on that point!
No matter how stiff the spring steel may be , it will hit it's harmonics -eventually- at one of those break neck speeds (155+MPH)...

The funny thing is, if you were to get a tunnel up and running, you'd probably be doing more actual RC engineering/testing than TRX and Arrma.

When the wind tunnel and moving treadmill surface is built & activated, he would take RC aerodynamics design/testing to the next level ,for sure.

Agreed that a wind tunnel alone would provide data on downforce, but not accurately show what ground effects. Now we're looking at a treadmill capable of 200mph! It's more of a dream than anything for me. Knowing I had access to a wind tunnel back in my college days and didn't really understand how cool that was makes me want to kick myself.

Don't beat yourself up..

Had I stayed focused and REALLY explore all the lab equipments that was available to me when I was back at the University ,way back when.. (And comprehended their use AND had the balls to roll up in there as a freshmen to Just Do It! Especially knowing what I know now.)
Man, all the crazy schiithings and experiments I would have done.

Like you said before, there is no substitute for testing and time with rubber on the road. I think the incrementally increasing speed tests combined with some supplementary data should increase confidence of a platforms stability.

One thing I'd like to do is become more familiar with lidar scans so I can automatically build 3d meshes for fluid flow simulation. That would be useful for modelling any RC. That might give more insight as to why the kraton wants to rocket to the moon after 70mph.

Dang it @Tex Koder , i've already got a drill press on my list of big tools in the garage, stop making me want to get a printer!!!

Hey now, YOU came onto this forum on your own free will.
No one here is twisting your arms..

I'm no siren, so IF you hear a 3D Printer calling your name, that's on you.