Belt Drive 4wd (racer) Do they exist anymore?

[Horatio]

Yeah, I'm a fan of the carbon and anodize. Def drool worthy.

I don't even know if my local track has a Touring Car (TC) class. I'll have to ask.

I hope he says no. One less car to maintain. HA

I've got plenty of cars for the driveway, if that's the case.

You'll like this then:

A 69mph street weapon.

Change the tyres, and it does all the same insanity off road. And not a belt in sight!

 

[CertifiedMike]

You could have told me (you didn't) but it would have been pure opinion based assumption if you did.

You're right in saying that the situation changes as the load increases. But not in a way that magically makes belts better, or that the inherent loss in the system goes away. That's a fallacy repeated over and over on RC forums for years.

"At lower loads, the percentage of energy lost to friction, heat, and other inefficiencies can be quite high compared to the output. As load increases, these losses may remain constant or increase at a slower rate than the output, leading to higher overall efficiency."

In other words, if you run your belt car at the lowest speed possible, a comparitively high percentage of the energy being applied is to overcome the losses to make it move. As more and more power is introduced, this percentage becomes relatively less vs the power being put into the system. The load isn't making the belt system 'better', the resistance is still there.

Our RC belts have "unavoidable losses due to mass, windage and hysterisis losses. Synchronous belts experience higher losses around small diameters because, first, synchronous belts are affected by pulley diameter, and second, even though different synchronous belts may run on the same physical pulley diameters, the drive efficiency can be quite different, just as with V-belts."

Our RC belts stretch under load - which reduces efficiency still further. Implying that additional load.

The Dyno isn't lying or misrepresenting things. At a time when brushed stock racing was happening, on 7.2v Nicads or NiMH cells, this mattered. This is why the TC3 simply won everything in 27t stock classes. It was basically untouchable.

In 2000 "In Modified and Stock Touring car A Mains, fifteen of the twenty cars were TC3s!" - at National level racing."

Now that we have all the brushless power in the world, the weight distribution advantages over rules any requirements we may have needed in the past for less resistance in the transmissions of our touring cars.

For off road, the arguments made in favour of shaftdrive are no longer being challenged. Obviously Schumacher are still giving it large. So both types of drive can and do still work well provided the car is good.

FG even have a 1/5th scale brushless, belt drive!

I don't know if its an "arguement"... Maybe a debate?
Did you open my link above?
Losi is in the belt game too.

I think as long as new materials that allow better heat loss, less friction, tighter machined tollerances or less mechanical loss, even better lubricants will keep "better" drive lines changing and evolving.
A reinforced belt will behave differently than one that is not. A reinforced belt is more durable than one that is not.
Lightweight materials make driveshafts rotate faster, making them more efficient.
A spring steel drive shaft will behave differently than one made of titanium.

We live in exciting times!

I'm still waiting for "direct drive" wheel systems where the wheel and hub ARE the motors... Maybe one day???

 

[Horatio]

I don't know if its an "arguement"... Maybe a debate?
Did you open my link above?
Losi is in the belt game too.

I think as long as new materials that allow better heat loss, less friction, tighter machined tollerances or less mechanical loss, even better lubricants will keep "better" drive lines changing and evolving.
A reinforced belt will behave differently than one that is not. A reinforced belt is more durable than one that is not.
Lightweight materials make driveshafts rotate faster, making them more efficient.
A spring steel drive shaft will behave differently than one made of titanium.

We live in exciting times!

I'm still waiting for "direct drive" wheel systems where the wheel and hub ARE the motors... Maybe one day???

Perhaps it's a mass debate.

 

[CertifiedMike]

Perhaps it's a mass debate.

I lived in Mass for years... you may well be on to something here!!!

 

[Horatio]

Look at the colours on this bad boy!

Shafties have thrown down the gauntlet in RC speed running for years, since the TC3 at an oval race meeting in 1999 threw down 70.67mph at the Cal State Dominguez Hills Velodrome, Dominguez Hills, California.

In 2001, Cliff Lett broke the speed record with a 2WD pan car - 111 mph. So it wasn't belt or shaft driven (if we exclude the solid rear axle, which in fairness is a type of shaft! )

So now, in 2024, we see 224mph to beat, on a 4WD Shaft driven car.

In the interests of objectivity and so people understand that I am only trying to state facts - top fuel dragsters super chargers are belt driven. No joke - these are 11000hp monsters.

 

[Horatio]

I'm still waiting for "direct drive" wheel systems where the wheel and hub ARE the motors... Maybe one day???

You'll like this video then.... obviously belties won't - because: no magic belts

KT somehow manages to wreck it on the bench. Then finishes it off big time stylie in the Gladiatorial Arena that is: the local Supermarket carpark....

 

[Lukedavis]

for the sc10 it was covered
View attachment 205955

ultimate rc (rip a great channel) has a video on it

I got one of those for 20 bucks a few years ago... I didn't realize how good of a score it was and traded it for a losi mini-t roller.

 

[CertifiedMike]

One thing we are drifting from is the original post of a 4wd racer.
When all out speed in a straight line and NO belt stretch would seem to be important (I don't know a lot about speed cars), it seems shafts and gear/direct drives are the popular choice.
I also have heard that heli motors are a common choice for a speed car.
Also not my first choice for a 4x4 racer.

R/C is HUGE!!! There will be a team who does a gear car or belt or... that WILL beat these records too one day.

I really like building.
I've been enjoying fitting new tech into my old Kyosho's lately!
Seeing things advance from brushed to brushless, nicad to lipo, carbon fiber parts over glass and graphite...
Let me assure everyone who wasn't there racing 30 years ago... we ARE currently living the FANTASY of vintage R/C racers!!!
There WILL be a better "nitro" fuel one day.

This is just how things work.

 

[Horatio]

I saw a good review of the Losi 22-4 2.0 here:

Losi 22-4 2.0

It's a nice looking buggy and Losi belt drives in the past were always well sealed and engineered.

It will be really interesting to see how it fares against the modern shaft driven machines - and the CAT of course.

The review states that it is very competitively priced and durable. It scored 9/10 on every metric, so the reviewer obviously likes it.

Let's see what 2025 brings.

 

[Horatio]

Here's a post from a few years ago on this subject:
The Jury's Out.....
It's a fascinating subject and brings out the geek in me.....wait a moment - RC racing is a niche hobby/sport and through the eyes of people outside of it - we're all geeks anyway! So let's not worry about it!

Over the years, I've raced numerous electric and I/C classes. I've raced at least 2 cars with chains. A dozen or so with belts and several shaft drive cars.

I think the subject can get us bogged down in theory. Yet very little scientific testing can be found. What we have instead are race results which people tend to base their opinions on. Combine that with racer's hardcore preferences and trends and we have a very emotive subject.

First off, we have so many classes, scales and formats. I/C - Nitro, Petrol. Electric - stock, modified, superstock, brushed, brushless. 1/10th, 1/8th, 1/5th.

I think in 1/10th it's clear to see that both shaft and belt can be used to good effect in both on and off-road applications. In 1/10th touring, in stock and superstock, I always preferred shaft drive. Given that I used the same motors, cells and esc's for my cars and my sons' cars, it was interesting to see how much was left in the cells after a 5min race. On twisty indoor circuits on carpet, I found the shaft cars (TC3, Yok MR4TCSD RS) consistently ran cooler and finished each round with more left in the cells vs the belt cars (Schumacher Axis). My sons found the belt drive cars easier to drive with a more planted feel. I liked the acceleration of the shaft driven cars and never really found torque-steer to be unmanageable on superstock. I felt I could drive around such issues and used good radios and servos for a very connected and responsive 'feel'.

Off road, in 1/10th 4WD Mod class racing, I generally preferred belt (Bosscat 3000 works) and the way the car felt in the air and on the loose stuff. Mostly, I raced on grass and as a race day went on, the track surface could start to wear and bring up stones. Technically, the belt drive was sealed, but just like your bathroom light is supposed to be sealed and still seems to get dead insects inside, belts and pulleys on grass tracks ALWAYS seemed to pick up at least one stone per meeting!

For a season, I tried a Tenth Tech Predator, shaft drive. It was blisteringly quick in a straight line. It was definitely more efficient than the belt drive CAT 3000. But.....I preferred the way the suspension felt on the CAT and how the CAT felt in the air. I also liked the fact that if I crashed the CAT, it used to stay intact. The Pred was not a forgiving car. If you got it wrong, it would break.

Belts require tension and thus sap some of the power on tap just to stay engaged with the pulleys they turn or else risk slipping. Getting the tension just right isn't easy. Kevlar reinforced belts need to be 'broken in' too - we used to soak ours in WD40 to soften them. Even when impeccably prepared and setup, belt drives are not as free running as shaft drives.

Shaft drives have to be perfectly shimmed and bedded in to get the best out of them. Hollow carbon shafts can also sound like a bag of nails.

Because our cars are so much more than just a driveline, so many aspects dictate whether or not they are competitive or not. The number one thing of course is our thumbs.

So.....belt or shaft? I think Shaft drives are more efficient. However, I think a well configured belt chassis can put power to the ground better on 1/10th classes.

For larger scales, Nitro, Petrol or Brushless, it has to be shaft for engineering related reasons for off-road classes. It seems clear that for high power applications, shaft offers the only workable solution. 1/8th Buggies, Truggies etc only use shaft drive.

With well engineered input gears and crown gears, losses with shaft drives are minimal, even taking into account transitioning rotation through 90 degrees at both ends of the car.

And remember - your belt drive car is still mostly shaft driven - because it puts power to the wheels using 4 drive shafts!

 

[Horatio]

Belt drives are not as efficient as racers give them credit for. It's pretty clear that as drive systems go, the main redeeming feature is that they are economical to mass produce. Belts place larger side loads on shafts/bearings, require a significant amount of friction to avoid slipping on their pulleys and oscillate during use, limiting the speed they can be used.

Popular as belt drives are, the claims regarding their efficiency over other drive types is largely fallacy. The reason behind their popularity lies in optimal weight distribution, smoother power delivery and the ability of the belt drive to absorb shock loads without damaging anything.

With the motor removed, roll a belt drive car down a short ramp and observe how far it rolls. Now try the same thing with a shaft drive car. The shaft drive car will roll much further.

Since batteries and brushless motors have improved, we worry less about the efficiency of our drivelines - it's a mute point. Driveability is far more important. Belt drives seem to offer this driveability in certain classes.

In stock class 1/10th Touring, when we were just starting to use NiMh cells, I found that shaft drive cars had more left in the cells than belt drives. This would indicate that shaft drive cars are actually more efficient than belt drive.

Regardless, what wins races? Consistency, Reliability Driveability - all of which can be found in both shaft or belt drive cars.

 

[9x19]

https://rchobbyexplosion.com/team-c...sis-kit-no-body-tires-or-electronics-c-00133/

On-road pan car

 

[CertifiedMike]

https://rchobbyexplosion.com/team-c...sis-kit-no-body-tires-or-electronics-c-00133/

On-road pan car

Thats puuuurty AND not a bad price!

 

[jimdavis577]

You could have told me (you didn't) but it would have been pure opinion based assumption if you did.

You're right in saying that the situation changes as the load increases. But not in a way that magically makes belts better, or that the inherent loss in the system goes away. That's a fallacy repeated over and over on RC forums for years.

"At lower loads, the percentage of energy lost to friction, heat, and other inefficiencies can be quite high compared to the output. As load increases, these losses may remain constant or increase at a slower rate than the output, leading to higher overall efficiency."

In other words, if you run your belt car at the lowest speed possible, a comparitively high percentage of the energy being applied is to overcome the losses to make it move. As more and more power is introduced, this percentage becomes relatively less vs the power being put into the system. The load isn't making the belt system 'better', the resistance is still there.

Our RC belts have "unavoidable losses due to mass, windage and hysterisis losses. Synchronous belts experience higher losses around small diameters because, first, synchronous belts are affected by pulley diameter, and second, even though different synchronous belts may run on the same physical pulley diameters, the drive efficiency can be quite different, just as with V-belts."

Our RC belts stretch under load - which reduces efficiency still further. Implying that additional load.

The Dyno isn't lying or misrepresenting things. At a time when brushed stock racing was happening, on 7.2v Nicads or NiMH cells, this mattered. This is why the TC3 simply won everything in 27t stock classes. It was basically untouchable.

In 2000 "In Modified and Stock Touring car A Mains, fifteen of the twenty cars were TC3s!" - at National level racing."

Now that we have all the brushless power in the world, the weight distribution advantages over rules any requirements we may have needed in the past for less resistance in the transmissions of our touring cars.

For off road, the arguments made in favour of shaftdrive are no longer being challenged. Obviously Schumacher are still giving it large. So both types of drive can and do still work well provided the car is good.

FG even have a 1/5th scale brushless, belt drive!

I would also tend to think that the power source would play a massive part to this is well ... I can't recall any nitro powered belt driven ... I can only assume this was due to the heat being able to effect the belt system ... but what you say about the effects and efficiency of belt vs shaft makes sense .... the tc3 was a beast back in the day .. I raced both electric and nitro versions ... if only they made parts for it still.... I'd probably still run one lol

 

[9x19]

Thats puuuurty AND not a bad price!

AND a kit, not a RTR.

 

[Lumikko]

You could have told me (you didn't) but it would have been pure opinion based assumption if you did.

When run without a load in a comparable application, belt drives are less efficient than shafts or chains. So shaft wins. This is not a matter of opinion (but I could be mistaken.)

You're right in saying that the situation changes as the load increases. But not in a way that magically makes belts better, or that the inherent loss in the system goes away. That's a fallacy repeated over and over on RC forums for years.

I avoid vague terms like ”better” when talking about features that have pros and cons and I certainly never claimed that the loss goes away thanks to magic.

Here’s a screen shot from a lab test comparing belt and chain drives on a bicycle. As the power input increases, friction in the system increases on a linear slope, but the increase is more gradual on the belt.

The preload tension of a belt causes losses even in a no-load situation, but the preload losses don’t increase with the load. The more gradual increase of friction under load starts to compensate for the initial disadvantage as soon as a load is applied.

A similar thing can be observed with bearings: a lubricated bearing stops spinning sooner than a dry one when no load is applied, because the lubricant adds initial drag. However, when the bearings are loaded, the lubricated one will run with smaller losses.

The Dyno isn't lying or misrepresenting things. At a time when brushed stock racing was happening, on 7.2v Nicads or NiMH cells, this mattered. This is why the TC3 simply won everything in 27t stock classes. It was basically untouchable.

With the motor removed, roll a belt drive car down a short ramp and observe how far it rolls. Now try the same thing with a shaft drive car. The shaft drive car will roll much further.

A zero-load dyno test or slowly rolling a freewheeling car down a ramp are poor methods of measuring drivetrain efficiency. These tests would suggest that dry bearings are the most efficient ones when in reality they are not. Efficiency tests should be performed with a realistic load (preferably different levels of loads) to give results that are more useful in real-life applications.

With all this out of the way, I’ll move on to debunking my own claim (or rather admitting that you got me) because I did assume things before.

My argument for the efficiency of the belt drive has been that it becomes comparatively more efficient at higher loads, and I always assumed that RC cars run the belts at the highest load they allow. But if that magical level of power where a belt drive becomes more efficient is never reached, then belt drives are certainly not more efficient.

It could be, for example, that the 27-turn brushed motors could not generate enough power to cross that threshold, so shaft cars were more efficient in practice. Even if it happened momentarily, a belt drive could still be less efficient on average. Peak power is called ”peak” for a reason.

Your experience of having less juice left in the battery after running belt drive vs. running a shaft drive is a real-world example that I appreciate and acknowledge.

In conclusion: I’ll stop saying belt drive cars are more efficient because the claim hangs on the assumption that the average power put through the drivetrain is high enough. Adding load does reduce the difference in losses between a belt drive and shaft drive, but I don’t know if it’s enough for the belt to come ahead in the end. The only correct answer is ”it depends”.

Source for the graph and full test: https://drive.google.com/file/d/1Kv7rAOiuudl3ZfAob6qxBEX_8tSWX3rx/view

 

[Horatio]

I would also tend to think that the power source would play a massive part to this is well ... I can't recall any nitro powered belt driven ... I can only assume this was due to the heat being able to effect the belt system ... but what you say about the effects and efficiency of belt vs shaft makes sense .... the tc3 was a beast back in the day .. I raced both electric and nitro versions ... if only they made parts for it still.... I'd probably still run one lol

1/8th nitro circuit racers - the 4wd ones - are usually belt driven.

 

[Horatio]

When run without a load in a comparable application, belt drives are less efficient than shafts or chains. So shaft wins. This is not a matter of opinion (but I could be mistaken.)


I avoid vague terms like ”better” when talking about features that have pros and cons and I certainly never claimed that the loss goes away thanks to magic.

Here’s a screen shot from a lab test comparing belt and chain drives on a bicycle. As the power input increases, friction in the system increases on a linear slope, but the increase is more gradual on the belt.

View attachment 208655

The preload tension of a belt causes losses even in a no-load situation, but the preload losses don’t increase with the load. The more gradual increase of friction under load starts to compensate for the initial disadvantage as soon as a load is applied.

A similar thing can be observed with bearings: a lubricated bearing stops spinning sooner than a dry one when no load is applied, because the lubricant adds initial drag. However, when the bearings are loaded, the lubricated one will run with smaller losses.



A zero-load dyno test or slowly rolling a freewheeling car down a ramp are poor methods of measuring drivetrain efficiency. These tests would suggest that dry bearings are the most efficient ones when in reality they are not. Efficiency tests should be performed with a realistic load (preferably different levels of loads) to give results that are more useful in real-life applications.

With all this out of the way, I’ll move on to debunking my own claim (or rather admitting that you got me) because I did assume things before.

My argument for the efficiency of the belt drive has been that it becomes comparatively more efficient at higher loads, and I always assumed that RC cars run the belts at the highest load they allow. But if that magical level of power where a belt drive becomes more efficient is never reached, then belt drives are certainly not more efficient.

It could be, for example, that the 27-turn brushed motors could not generate enough power to cross that threshold, so shaft cars were more efficient in practice. Even if it happened momentarily, a belt drive could still be less efficient on average. Peak power is called ”peak” for a reason.

Your experience of having less juice left in the battery after running belt drive vs. running a shaft drive is a real-world example that I appreciate and acknowledge.

In conclusion: I’ll stop saying belt drive cars are more efficient because the claim hangs on the assumption that the average power put through the drivetrain is high enough. Adding load does reduce the difference in losses between a belt drive and shaft drive, but I don’t know if it’s enough for the belt to come ahead in the end. The only correct answer is ”it depends”.

Source for the graph and full test: https://drive.google.com/file/d/1Kv7rAOiuudl3ZfAob6qxBEX_8tSWX3rx/view

Thanks for another excellent reply to this thread! The information contained here is great reference for people trying to make informed buying decisions.

The bicycle tests are very interesting. In the graph, it shows the 250watt marker for chain and belt. This indicates why belts have not really caught on for human powered bicycles.

The blue line represents what people can realistically maintain.

Due to the limitations, gearing and frame related compromises - belt would seem much better suited to e-bikes, right?

I'm obviously not making a direct comparison between human powered bicycles and 27t stock racing, but for reference a good reedy MVP properly prepared for national level racing would be putting out 'about' 150watts on punchy, extremely well matched cells, super peaked.

Compare that to an eBay special £50, 4292 1780kv 4000watt motor!! How times have changed.

Anyway, your informative and diplomatic post has not been lost on me - I appreciate it. Cheers

 

[CertifiedMike]

Thanks for another excellent reply to this thread! The information contained here is great reference for people trying to make informed buying decisions.

The bicycle tests are very interesting. In the graph, it shows the 250watt marker for chain and belt. This indicates why belts have not really caught on for human powered bicycles.

View attachment 208662
The blue line represents what people can realistically maintain.

Due to the limitations, gearing and frame related compromises - belt would seem much better suited to e-bikes, right?

I'm obviously not making a direct comparison between human powered bicycles and 27t stock racing, but for reference a good reedy MVP properly prepared for national level racing would be putting out 'about' 150watts on punchy, extremely well matched cells, super peaked.

Compare that to an eBay special £50, 4292 1780kv 4000watt motor!! How times have changed.

Anyway, your informative and diplomatic post has not been lost on me - I appreciate it. Cheers

You've completely neglected to account for RedBull vs Gatorade and then theres the whole "blondes vs brunettes" controversy.
This thread has gone WAY off topic!

 

[Horatio]

You've completely neglected to account for RedBull vs Gatorade and then theres the whole "blondes vs brunettes" controversy.
This thread has gone WAY off topic!

I could always start a poll here, right? Or would the ban hammer come out.....