Limitless LibertyMkiii's crazy belt drive car project

[Diem Turner]

If i had Elon budgets i'd just shout, let's add some graphene to the foam.

Seriously, i do think we just need some luck. Eventually some space or other tech company will need lighter and stronger foam compound for some weird usecase and hope it ends up on the consumer market. It's not unlikely it does already exist

We probably just need to explore other foam rubber compounds that already exist and, given enough time and resources, we're bound to find the "magic rubber".

 

[Dan B.]

So this poses the question: What will that "better tire" look like, i.e. of what will it be made/how will it be constructed? Do you think it's just a matter of perfecting the full surface glue-up of the foam (which, when compared to rubber, has the property of being relatively light by volume which results in less rotational mass pulling on the bonding area between tire and rim...which, even at that weight, I imagine is rather substantial at those rotational velocities) or have we reached the limits of what foam rubber is physically capable of and we need to think in terms of something entirely new in both tire material and design?

The answer might be something nobody expects. How fast can an RC car go? A lot faster as scale increases. Don’t forget, we might not be married to 1/7 cars for long. I’ve wondered why no one is pursuing the records with a 1/5 even today. The larger the scale, the larger diameter of the tires, and the lower the RPM’s are for any given speed. We may have hit the current limit for high speed RC tires, but we’ve only done so for 1/7 scale rigs. What if we got up into 1/4 scale? We’d be edging closer to pneumatics, even. Or good, belted non-pressurized rubber tires for sure. Just a theory…

EDIT: I just saw that @LibertyMKiii said basically the same thing in regard to tire size having to increase. Never mind…

 

[Diem Turner]

The answer might be something nobody expects. How fast can an RC car go? A lot faster as scale increases. Don’t forget, we might not be married to 1/7 cars for long. I’ve wondered why no one is pursuing the records with a 1/5 even today. The larger the scale, the larger diameter of the tires, and the lower the RPM’s are for any given speed. We may have hit the current limit for high speed RC tires, but we’ve only done so for 1/7 scale rigs. What if we got up into 1/4 scale? We’d be edging closer to pneumatics, even. Or good, belted non-pressurized rubber tires for sure. Just a theory…

It's a thought but, practical attempts rarely see 1/5 scale race cars pierce the 100mph barrier, to say nothing of 150, 180, 200, etc. This, of course, could be down to a number of factors or, and this is my suspicion, a conflagration of factors. The bigger car requires more power. The bigger car has a larger cross section creating more resistance requiring yet more power. There doesn't appear to be much of a 1/5 scale speed running scene and, as a result, there really isn't a speed running aftermarket scene which can (and probably does) affect everything from gears to tires. I'm only speculating here but, the lack of any really fast 1/5 scale cars, seems to validate the fact that something is limiting the possibilities. I realize that sheer cost could be an issue but, there are enough ballers in RC that at least two or three would have materialized in the last few years but if you search 1/5 scale speed run on Youtube, you'll find more X-MAXX, Kraton 8S, DBXL-E and Losi 5ive videos than dedicated road cars like FG. I get the sense that 1/8-1/7 scale is the sweet spot for speed running with the available components (electrics, power to weight ratio, etc.), though that perception is probably biased by the fact that most serious speed runners are running 1/8 and 1/7 scale cars...but it might also be that they're running them because they're the sweet spot. Chicken...meet egg. That's my half cent anyways.

 

[Dan B.]

It's a thought but, practical attempts rarely see 1/5 scale race cars pierce the 100mph barrier, to say nothing of 150, 180, 200, etc. This, of course, could be down to a number of factors or, and this is my suspicion, a conflagration of factors. The bigger car requires more power. The bigger car has a larger cross section creating more resistance requiring yet more power. There doesn't appear to be much of a 1/5 scale speed running scene and, as a result, there really isn't a speed running aftermarket scene which can (and probably does) affect everything from gears to tires. I'm only speculating here but, the lack of any really fast 1/5 scale cars, seems to validate the fact that something is limiting the possibilities. I realize that sheer cost could be an issue but, there are enough ballers in RC that at least two or three would have materialized in the last few years but if you search 1/5 scale speed run on Youtube, you'll find more X-MAXX, Kraton 8S, DBXL-E and Losi 5ive videos than dedicated road cars like FG. I get the sense that 1/8-1/7 scale is the sweet spot for speed running with the available components (electrics, power to weight ratio, etc.), though that perception is probably biased by the fact that most serious speed runners are running 1/8 and 1/7 scale cars...but it might also be that they're running them because they're the sweet spot. Chicken...meet egg. That's my half cent anyways.

Agreed, but I think the something that is limiting it is just the reason that nobody is doing it and that the current components (XLX2’s, etc.) are maxed out at this scale. I don’t think getting the power to push a 1/5 or 1/4 would be that much of an obstacle, someone just needs to build it. We’re just at the mercy of basically one manufacturer doing ESC’s right now, and that’s what the surface RC world has maxed out at. Bigger scale could have real benefits too, at least theoretically, with tires and aero getting much better potentially? IDK, I could certainly never make that kind of leap to a larger scale given how expensive it is to build a speed run car as it is. Definitely too rich for my blood, as the saying goes.
But hey (and here I try out my best Rod Serling voice) “imagine, if you will…a 1/4 scale Porsche 917K, carbon chassis, a giant TP motor at each wheel, screaming past at 240mph., just the the originals did.” Chills, baby!

 

[LibertyMKiii]

The only problem as scales go up is costs.
I couldn't imagine the costs or damage from a 1/4 scale crash

For whatever reason, the 1/5 scale on road tires are not much larger in diameter than the 1/8. We would need a significant diameter increase to bring the RPMs down enough to help a significant amount.

You can get Gone Bananas to "skin" any RC wheel with foam. The Xmaxx and XRT guys do that for speed runs.
I have some Losi 5b wheels for that intent, but there is no way I am scrapping this car and starting over LOL

98mm GRP vs Losi 5 buggy wheels:

 

[TN-RC]

So this poses the question: What will that "better tire" look like, i.e. of what will it be made/how will it be constructed? Do you think it's just a matter of perfecting the full surface glue-up of the foam (which, when compared to rubber, has the property of being relatively light by volume which results in less rotational mass pulling on the bonding area between tire and rim...which, even at that weight, I imagine is rather substantial at those rotational velocities) or have we reached the limits of what foam rubber is physically capable of and we need to think in terms of something entirely new in both tire material and design?

Me and @LibertyMKiii asked the same question "What will that "better tire" look like" I am not going to share what we came up with, but we have some ideas. I hope I will be able to run some experiments this summer or fall since I have a foam manufacture just up the road with a walk-in office.
There are many solutions that we have talked about and I really what to try them.
The only problem that comes to mind is how to test the tires for 200mph without going 200mph I will have to spin them but will also have to know what amount of force is on the wheel/tire at 200mph.

The answer might be something nobody expects. How fast can an RC car go? A lot faster as scale increases. Don’t forget, we might not be married to 1/7 cars for long. I’ve wondered why no one is pursuing the records with a 1/5 even today. The larger the scale, the larger diameter of the tires, and the lower the RPM’s are for any given speed. We may have hit the current limit for high speed RC tires, but we’ve only done so for 1/7 scale rigs. What if we got up into 1/4 scale? We’d be edging closer to pneumatics, even. Or good, belted non-pressurized rubber tires for sure. Just a theory…

EDIT: I just saw that @LibertyMKiii said basically the same thing in regard to tire size having to increase. Never mind…

You hit the nail right on the head. It will take more time to accelerate so long roads are needed and it will be way more expensive to build.
But the larger the car and tires are the more places you can run, I don't think you could take a 1/7th out to a salt flat but you could at 1/5th or a 1/4th. I think we would start needed to use (RC) aviation radio technology at that point.

It's a thought but, practical attempts rarely see 1/5 scale race cars pierce the 100mph barrier, to say nothing of 150, 180, 200, etc. This, of course, could be down to a number of factors or, and this is my suspicion, a conflagration of factors. The bigger car requires more power. The bigger car has a larger cross section creating more resistance requiring yet more power. There doesn't appear to be much of a 1/5 scale speed running scene and, as a result, there really isn't a speed running aftermarket scene which can (and probably does) affect everything from gears to tires. I'm only speculating here but, the lack of any really fast 1/5 scale cars, seems to validate the fact that something is limiting the possibilities. I realize that sheer cost could be an issue but, there are enough ballers in RC that at least two or three would have materialized in the last few years but if you search 1/5 scale speed run on Youtube, you'll find more X-MAXX, Kraton 8S, DBXL-E and Losi 5ive videos than dedicated road cars like FG. I get the sense that 1/8-1/7 scale is the sweet spot for speed running with the available components (electrics, power to weight ratio, etc.), though that perception is probably biased by the fact that most serious speed runners are running 1/8 and 1/7 scale cars...but it might also be that they're running them because they're the sweet spot. Chicken...meet egg. That's my half cent anyways.

I think we don't see big numbers because a lot of people don't have them because of the cost and size, and they are trying to do that with 1 motor fort the size and weight vs. a dual motor 1/7th you would need over 6 motors in a 1/5th scale car. (You were saying most of that)

Agreed, but I think the something that is limiting it is just the reason that nobody is doing it and that the current components (XLX2’s, etc.) are maxed out at this scale. I don’t think getting the power to push a 1/5 or 1/4 would be that much of an obstacle, someone just needs to build it. We’re just at the mercy of basically one manufacturer doing ESC’s right now, and that’s what the surface RC world has maxed out at. Bigger scale could have real benefits too, at least theoretically, with tires and aero getting much better potentially? IDK, I could certainly never make that kind of leap to a larger scale given how expensive it is to build a speed run car as it is. Definitely too rich for my blood, as the saying goes.
But hey (and here I try out my best Rod Serling voice) “imagine, if you will…a 1/4 scale Porsche 917K, carbon chassis, a giant TP motor at each wheel, screaming past at 240mph., just the the originals did.” Chills, baby!

I think the Max4 was a good push in the larger scale direction, but I think you are right about the ESC, one that was double the size but 4x power would be great for large scale.

 

[Dan B.]

Me and @LibertyMKiii asked the same question "What will that "better tire" look like" I am not going to share what we came up with, but we have some ideas. I hope I will be able to run some experiments this summer or fall since I have a foam manufacture just up the road with a walk-in office.
There are many solutions that we have talked about and I really what to try them.
The only problem that comes to mind is how to test the tires for 200mph without going 200mph I will have to spin them but will also have to know what amount of force is on the wheel/tire at 200mph.

You hit the nail right on the head. It will take more time to accelerate so long roads are needed and it will be way more expensive to build.
But the larger the car and tires are the more places you can run, I don't think you could take a 1/7th out to a salt flat but you could at 1/5th or a 1/4th. I think we would start needed to use (RC) aviation radio technology at that point.

I think we don't see big numbers because a lot of people don't have them because of the cost and size, and they are trying to do that with 1 motor fort the size and weight vs. a dual motor 1/7th you would need over 6 motors in a 1/5th scale car. (You were saying most of that)

I’ve seen the fly guys use 12s ESC’s for awhile now, and a few people were running them in DBXL-E’s before the Max 4 came out. They’re smaller than an XLX2 as well. How many 12s ESC’s and big ol’ TP motors can you cram in a 1/4? $$$$$!!! It’d be a really fun project to watch as long as it was on someone else’s dime.

 

[TN-RC]

The only problem as scales go up is costs.
I couldn't imagine the costs or damage from a 1/4 scale crash

For whatever reason, the 1/5 scale on road tires are not much larger in diameter than the 1/8. We would need a significant diameter increase to bring the RPMs down enough to help a significant amount.

You can get Gone Bananas to "skin" any RC wheel with foam. The Xmaxx and XRT guys do that for speed runs.
I have some Losi 5b wheels for that intent, but there is no way I am scrapping this car and starting over LOL

98mm GRP vs Losi 5 buggy wheels:

View attachment 273051

I am thinking someone should put this on a Typhon. The cost would be 4X of a 1/7th scale, but if you think about it when you get that big it could be a club or a group or a business tax deductible/advertisement that would be a cheap build by 30X+ vs. anything else you would see on a race day on the salt flat.

 

[chekos1]

This 200+ build is on pause for a bit. I need to have some aluminum CNC'd for this one and honestly, the wind is knocked out of this particular sail.
Watching Tony's 203 mph in car video I can see those dual motor 1/7 cars will be hitting speeds of 215+ beyond what the tires can handle.

Until better tires come along I just don't see a point in shooting for those 200+ speeds.

Come on Liberty, you should see this project through. I think you are so close to stop pushing now!

Sure the only limiting factor right now is probably the tires. You cant really improve them, I tried to come up with something but custom options require so much time and money and at the end of the day I don't think it is worth it. But there might be ways to indirectly conserve the foams and even prolong their life into higher speeds. My feeling tells me that a lighter car should be able to stress the tires less and that might give you an edge at 200mph+. Not sure about this at all though.

I have very limited experience on this and I think that I need more runs to verify my findings. I can say that stiffer wheels appear to be better, but again not 100% sure.

I will try and collect some more data at ROSSA this year as I am hoping to have a second car with 1/8 BSRs. Time to connect those 3s in series and send it, hopefully I can learn something before it goes up in flames.

 

[LibertyMKiii]

Come on Liberty, you should see this project through. I think you are so close to stop pushing now!

Sure the only limiting factor right now is probably the tires. You cant really improve them, I tried to come up with something but custom options require so much time and money and at the end of the day I don't think it is worth it. But there might be ways to indirectly conserve the foams and even prolong their life into higher speeds. My feeling tells me that a lighter car should be able to stress the tires less and that might give you an edge at 200mph+. Not sure about this at all though.

I have very limited experience on this and I think that I need more runs to verify my findings. I can say that stiffer wheels appear to be better, but again not 100% sure.

I will try and collect some more data at ROSSA this year as I am hoping to have a second car with 1/8 BSRs. Time to connect those 3s in series and send it, hopefully I can learn something before it goes up in flames.

I am not stopping on the project, but just shifting focus for a bit.
I always have to tinker and make things...

 

[LibertyMKiii]

Interesting video. He is engineering a 250+ mph tire.
Requires a long run as the traction is less than a standard tire.

 

[TN-RC]

Interesting video. He is engineering a 250+ mph tire.
Requires a long run as the traction is less than a standard tire.

2 problems and I am sure you are thinking about the same things.
1. The way it is we don't have enough space for what we have got now so longer run up is not an option.
2. His test was with no force on the tire and no added vibration.
I am glad people are out there that are testing tires ideas!
Also did he send this video to you, it's unlisted?
Also, if you look at his other videos, his road is the best road for speed running I have ever seen!

 

[LibertyMKiii]

2 problems and I am sure you are thinking about the same things.
1. The way it is we don't have enough space for what we have got now so longer run up is not an option.
2. His test was with no force on the tire and no added vibration.
I am glad people are out there that are testing tires ideas!
Also did he send this video to you, it's unlisted?
Also, if you look at his other videos, his road is the best road for speed running I have ever seen!

Oops hopefully he is ok with me sharing it... I was chatting with him about it this morning. He has tested this tire up over 100 mph already.
It's all new and in development, but very interesting.

 

[MLyons]

Also, if you look at his other videos, his road is the best road for speed running I have ever seen!

You'd be hard pressed to find a runway that nice in the UK, let alone a normal road.

 

[TN-RC]

Oops hopefully he is ok with me sharing it... I was chatting with him about it this morning. He has tested this tire up over 100 mph already.
It's all new and in development, but very interesting.

Hopefully he doesn't beat me to the gun, I got more ideas I want to test this spring/summer.

 

[joshludden]

Hopefully he doesn't beat me to the gun, I got more ideas I want to test this spring/summer.

I've always wondered why someone doesn't make a solid rubber tire for speed running, kinda like what the REALLY fast guys use to run 700+ mph on the salt flats?

 

[TN-RC]

I've always wondered why someone doesn't make a solid rubber tire for speed running, kinda like what the REALLY fast guys use to run 700+ mph on the salt flats?

The problem with rubber is that it is heavy, I am going to try it, but it will look different than what we have now.
I have talked to LibertyMKiii quite a bit about all of this, when someone makes a 200mph pass with a 1/7th scale RC car the wheels are spinning faster than ThrustSSC (world land speed record holder) wheels would have and way RPM's then the fastest wheel powered car.

 

[Jason F]

I've always wondered why someone doesn't make a solid rubber tire for speed running, kinda like what the REALLY fast guys use to run 700+ mph on the salt flats?

The “Solid tires” used at Bonneville are all aluminum, with some grooves cut into them, no traction compared to rubber.

 

[TN-RC]

The “Solid tires” used at Bonneville are all aluminum, with some grooves cut into them, no traction compared to rubber.

I could be wrong, but I think the "Aluminum only" wheels are used on non-wheel powered cars, so traction does not matter.
It looks like on the worlds fastest wheel driven car they used an aluminum rim with a solid rubber tire.

 

[Jason F]

I could be wrong, but I think the "Aluminum only" wheels are used on non-wheel powered cars, so traction does not matter.
It looks like on the worlds fastest wheel driven car they used an aluminum rim with a solid rubber tire.

Most vehicles that are wheel driven use a solid wheel/tire that is bonded, but it is not rubber (too heavy) it is some kind of silicone.