Recommended Posts

I had many people ask me in the Wildcat 6x6 topic and it's video if I really need 12 motors, couldn't I get simillar performance with a lighter model?

So in order to test and showcase my reasoning I built this very simple 4x4, it uses only 555 parts and is powered by "only" 2 motors:

640x480.jpg

Originally the driveline and gear ratio was as following:

Motor's fast outputs to the 2 speed gearbox - 12 tooth bevel gears - via cardan joints to the planetary hubs

But than I soon noticed the model lacked sufficient torque, especially in high gear, so I changed the driveline to the following:

Motor's fast outputs to the 2 speed gearbox - 20:28 normal differential - via small CV joints to the planetary hubs

640x480.jpg

This driveline ended up having a very simillar gear ratio as the Wildcat 6x6, I think it's some 3% faster, which is negliable IMO.

One thing that I did have to do is lubricate the main drive axle, as it was prone to melting in high gear:

640x480.jpg

Because this light 4x4 has open differentials, the front suspension was designed in such a way that it imitatates a pendular front axle by having shock absorbers on a pivot. This allows the front axle to basically act like a pendular axle, easily adjusting to the terrain amd keeping the weight even on both left and right side.

640x480.jpg

So...What about the results?

Well, the outdoor test showed that the model performs good in low gear, it has plenty of torque to climb and works really smooth and efficient. But where it lacked was in high gear. While it did reach 15 km/h as the Wildcat 6x6, the acceleration itself was much lower and both motors were drawing a lot of current. Any prologned steering in high gear at full power caused the motors to overheat and cut out, no powersliding on gravel like the Wildcat 6x6. Also when driving on the pump track, it was able to go over big hills in high gear, but it was lacking the speed to actually get significant air, again unlike the Wildcat 6x6.

So... Why does it seem more motors and a heavier model is preferable?

The answer comes to one factor - Power To Weight ratio:

  • Wildcat 6x6 uses 12 drive motors and weighs around 2,5 kg - this means each motor has to move around 208 grams of weight
  • This light 4x4 offroader uses 2 drive motors weighs around 0,8 kg - in this case each motor has to deal with 400 grams of weight, almost double of the Wildcat 6x6

So does that mean bigger is always better?

Well when it comes to math, it seems to point that way. But bigger and heavier models suffer from another problem - the Inverse Cube Law. Basically a bigger model needs more structural reinforcments to hold itself together which means it's heavier and therefore needs more power, etc... It's a typical problem in aviation and rocket science. In our case, a bigger model if built efficiently (using frames and such for a light, strong chassis) will generally perform better, but it will also cause a greater load on the individual parts such as suspension components and wheels in the case of my Wildcat 6x6 (when going to quickly over a large bump, the front wheels have a tendency to fall off to to the higher forces in relation to higher weight).

So what's the take from all this? I would summarize it like this:

  • If you want a robust, reliable model go light and slower
  • If you want a very high performance model, pack it full of motors, though individual components may suffer more and fail under their own weight.
  • Also remember there are some heavy elements such as steering motor, wheels, tyres, hubs that you will have to use regardless of the number of drive motors - which weight favours being spread among more motors
  • And also that some components such as planetary hubs do come with some inherent friction that will have to be overcome - which again favour it's friction being spread among more drive motors.

I'd love to to hear your opinion about this. Also if anyone is interested, i can make a seperate topic/video about the Light 4x4 offroader.

Edited by Zerobricks

Share this post


Link to post
Share on other sites
7 hours ago, Zerobricks said:

This light 4x4 offroader uses 2 drive motors weighs around 0,8 kg - in this case each motor has to deal with 400 grams of weight, almost double of the Wildcat 6x6

I know it can sound like pointless and wrong way to go, but what about adding two more motors to your simple model? It won't be 200g/motor for sure, but maybe you will get like closer to 300g/motror instead of 400g/motor?

Share this post


Link to post
Share on other sites
15 minutes ago, keymaker said:

I know it can sound like pointless and wrong way to go, but what about adding two more motors to your simple model? It won't be 200g/motor for sure, but maybe you will get like closer to 300g/motror instead of 400g/motor?

Exactly! And going into that direction you end up with the Wildcat 6x6 with 210g/motor. So as suggested there surely is a middle ground where you have sufficient Power To Weight ratio while also not going over let's say 1500 grams.

Share this post


Link to post
Share on other sites
10 hours ago, Zerobricks said:

Also if anyone is interested, i can make a seperate topic/video about the Light 4x4 offroader. 

I would love a video. Or enough photos to reverse-engineer it. :grin:

Edited by Jayden

Share this post


Link to post
Share on other sites
13 hours ago, Jayden said:

I would love a video. Or enough photos to reverse-engineer it. :grin:

I could, though I think an upgraded version with 4 motors might have less performance issues and longer play time.

Share this post


Link to post
Share on other sites

You made an interesting research, congrats! I would agree with your conclusions except the second one. 

Each motor has individual characteristics as well as It`s own areas of application. For example, PF XL motor has a plenty of torque but it is slow. So it is worth to using it in crawlers. But if you want to make a fast car with it you will have to multiply it`s speed with a gearbox, which always takes space, increase weight, has a plenty of friction... Buwizz (Buggy) motor is a lot faster than PF XL motor, so it can be widely used in fast cars. And it was mostly the only "reasonable" area of application for them, until planetary hubs appeared. Combining Buwizz motors with planetary hubs we get a lot of torque on wheels, a reliably working transmission (sipping fast but without big stress). These ideas are agreed with real car engineering. All this was right until you started speak about "high performance".

The Weight To Ratio reasoning is very important for real sport cars, and clearly can be applied to Lego models. I am trying to lighten the car as much as I can to make a car with good performance, as well as real engineers does. But real engineers usually does not increase the number of engines in their cars. Yes, there was several two-engine rally cars, but we will ignore them :pir-classic:. Engineers try to increase the power of the car by boosting the engine or changing it to a more powerful one. My conclusion from this is the following:

  • If you want to radically improve the performance of the Lego car, you need a more powerful motor. 

For example, if my car was driven by two PF M-motors, I can upgrade them to PF L-motors. Further upgrade will require Buwizz motors, but what should I do next? I spent a lot of time on this question. My answer to it is the following:

  • Maximal reasonable number of Buggy motors is 1motor per wheel (with minimal number of gears in the transmission, preferably without intermediate gears at all). Further improvement of performance will require a third party motor with greater characteristics, for example one from RC world.

Why 4 motors is reasonable? Because real Electric Super Cars use such layout!

Buggy motors seems to be the top motors with PF connectors, because PF connectors could melt under higher load (from more powerful motor). So a serious improvment of electronics is required, preferably RC electronics. Further we will need to reinforce suspension, transmission with metal parts. The final result of such upgrades is an RC car in big scale :pir-grin:. So if you want a true high-performance car to drive you would better buy yourself a good RC car - it will be faster, stronger, more efficient and cheaper!

I like lego RC car and I will stick to them, no matter which limitations they have. Buwizz units and Buwizz motors are great products for Lego cars, which allow to build top RC LEGO vehicles, but they have their own limitations as well as all Lego plastic parts. That is why it is important to understand these limitations and develop new cars very reasonably (balancing between mass and power). 

 

 

 

 

Share this post


Link to post
Share on other sites

Interesting topic! I have been thinking about whether I should experiment with more than 2 motors after the race in the Buwizz camp, because my model seemed quite slow compared to some others using 4 motros (and yours of course), and figured it's exactly as you say, because of the number of motors to weight ratio. I will probably try it once I get my two extrs motors posted, though I am still a bit afraid of smoking away too many components.. But your approach of distributing motor torque seems like a safer way to go. Unfortunately, that does not really favour realistic drivetrains and suspensions, like live axles with a central driveshaft, or there will be a lot of torque directed to those central axles. Even with two motors, the new CV joints in my drivetrain are starting to deform a bit, and also my planetary hubs are running too smooth compared to when they were brand new. I have done the swap of the diffs to older ones to gain more speed, and now the drivetrain is like this: slow output of two motors coupled onto the central driveshaft, going to 20:28T diffs and then to the planetaries). This setup has quite good playable speed with a 1.4 kg model, but still plenty of torque, it can climb a 50 degree slope crazy fast (and it still does not cut out the Buwizz 3 if I avoid running it back and forth quickly). So for me, this is kind of a sweet spot I find both playable, reasonably priced and component friendly (I lubricated every moving component, including the suspension towballs, as even those had visible wear, i.e. plastic poweder).

Anyway, about your model. As far as I can see, the high gear up-gears 3:1, right? With using the fast output, which is about 1.5x faster than the slow output, that's altogether 4.5x faster than the slow output itself which causes a lot of friction and probably loss of efficiency, and then the whole thing is slowed down at the planetary hub 5.4x, which about cancels that speed-up. So maybe, it would be interesting to see how this setup compares to instead using the slow output of the motor in combination with non-planetary hubs. Maybe it has a better efficiency and is less prone to damaging parts. Probably it would be good to lubricate the hubs themselves. Have you ever tried such a setup? I want to test that in a trophy build in the future (with 2 buwizz motors).

Finally, I'd like to make a note about controllability. I think these speeds achievable with more than 2 motors quickly become uncontrollable and hence somewhat impractical, which is also an important playability factor, especially for offroaders. In the camp we have seen a nice build with 3 motors, it was very light, so good power to weight ratio, crazy speed, but it could not perform well in the race because it was soo uncontrollable (also partly due to the app-control). Also, I had the feeling that you were a bit careful with your model in the race, not making use of all the power it has, because you wanted to keep it controllable. That's also one thing to consider when designing a fast model.

Share this post


Link to post
Share on other sites

Great response, @gyenesvi

The new CV joints though very strong do show wear and tear, but that happens even in the original 42099. Same thing with planetary hubs, they get loose over time and generate a lot of white dust on the brim of the hub connection.

Regarding gearing, slow output of the BuWizz/RC motors seems the most optimal with the planetary hubs indeed and if you need more torque, a normal or Ferrari's differential can help along.

My previous models used the original and brick-built portal hubs. Planetary hubs do have a few weaknesses compared to the planetary hubs in my opinion though:

  • Larger pivot point which requires a stronger steering mechanism
  • Lower gearing ratio (maximum of 3:1 is possible) means that the usual cardan joint is prone to breaking apart - this could be remedied using the new CV joints
  • The gears are exposed and prone to catching dirt, reducing performance
  • And lastly the last axle - the one driving the gears does tends to bend out of shape, especially with heavier models since it has to carry the final generated torque of the whole drivetrain
  • Another problem with portal hubs is that due to their lower gearing they require stronger differentials/perpendicular drives. This is why the geraboxes in those models tend to gear down in lower gears instead of fearing up. But gearing down can and does cause the gears to skip - in my case the Tiger 6x6 can skip the 8 tooth gears on the differential casing acting as a low gear when all wheels are blocked. When gearing up in the Widlcat 6x6, there are no such issues.

And of course the planetary hubs have their own weaknesses:

  • Lower ground celarance compared to planetary hubs
  • Higher initial friction
  • Harder to integrate into the model
  • No user-replacable components - once it's worn out there's notinh to replace, you can only buy a new one

Lastly, regarding controllability, you are totally right, no amount of power does any good if you can't control it. And yes I wasn't pushing the Wildcat 6x6 to it's full capability, since I was trying to get through all the obstacles for extra points and I also didn't wanna risk any power cut-outs.

Share this post


Link to post
Share on other sites
9 hours ago, Zerobricks said:

I could, though I think an upgraded version with 4 motors might have less performance issues and longer play time.

I only have 2 BW motors though... However yes 4 motors would have better performance.

Edited by Jayden

Share this post


Link to post
Share on other sites
7 hours ago, gyenesvi said:

Anyway, about your model. As far as I can see, the high gear up-gears 3:1, right? With using the fast output, which is about 1.5x faster than the slow output, that's altogether 4.5x faster than the slow output itself which causes a lot of friction and probably loss of efficiency, and then the whole thing is slowed down at the planetary hub 5.4x, which about cancels that speed-up. So maybe, it would be interesting to see how this setup compares to instead using the slow output of the motor in combination with non-planetary hubs.

Great calculations! I will try such built with:

  • 4 Buwizz motors, slow output
  • 95 mm RC tires
  •  "normal hubs", direct connection of motors to hubs via metal U-joint linkage (strong CV linkage).

Such setup give a close ratio 95/107 * 5.4/4.5 ~ 1.07 while avoid losses in transmission (friction in planetary hubs, differential). All though such layout provides a signifiant stress on the transmission, so the CV joints will stress a lot under the load (comparing to the layout with planetary hubs).

Unfortunately, I will be able to finish these model only in September. So I will report on results later.

7 hours ago, gyenesvi said:

Finally, I'd like to make a note about controllability. I think these speeds achievable with more than 2 motors quickly become uncontrollable and hence somewhat impractical, which is also an important playability factor, especially for offroaders. In the camp we have seen a nice build with 3 motors, it was very light, so good power to weight ratio, crazy speed, but it could not perform well in the race because it was soo uncontrollable (also partly due to the app-control). Also, I had the feeling that you were a bit careful with your model in the race, not making use of all the power it has, because you wanted to keep it controllable. That's also one thing to consider when designing a fast model.

Agree! The lack of control is significant, and there are several points to consider:

  • A high momentum of a car which drive fast (even bigger momentum of a heavy car driving fast). It provides quite some stress both on the transmission and suspension in tight cornering. 
  • A weak steering system. I tried many ways to strengthen the steering system: from increasing the steering arms on the wheel hubs, to the double suspension arms setups... Regardless all the improvements I made, it is all made of plastic, has a significant wobbling (in the connection of a steering rack to steering gear, and in the ball joints of a steering bones). 
  • The lack of physical feedback to the driver. It is impossible to control a fast Lego car even with RC proportional system since the driver can not feel the car. Real drivers can hear the noise of the motors, check various sensors in the car, feel most of the bumps and, most importantly, feel the steering wheel resistance (it is well known that of high speed it is harder to steer the wheels).

Summing up, it is nearly impossible to control a Lego car which drive over 12 km/h especially of the rough terrain. To understand that clearly, just take a look at fast RC cars which has a tendency to roll over onto their roofs :pir-cry_happy:.

Share this post


Link to post
Share on other sites
5 hours ago, Daniel-99 said:

Great calculations! I will try such built with:

  • 4 Buwizz motors, slow output
  • 95 mm RC tires
  •  "normal hubs", direct connection of motors to hubs via metal U-joint linkage (strong CV linkage).

Such setup give a close ratio 95/107 * 5.4/4.5 ~ 1.07 while avoid losses in transmission (friction in planetary hubs, differential). All though such layout provides a signifiant stress on the transmission, so the CV joints will stress a lot under the load (comparing to the layout with planetary hubs).

Unfortunately, I will be able to finish these model only in September. So I will report on results later.

Agree! The lack of control is significant, and there are several points to consider:

  • A high momentum of a car which drive fast (even bigger momentum of a heavy car driving fast). It provides quite some stress both on the transmission and suspension in tight cornering. 
  • A weak steering system. I tried many ways to strengthen the steering system: from increasing the steering arms on the wheel hubs, to the double suspension arms setups... Regardless all the improvements I made, it is all made of plastic, has a significant wobbling (in the connection of a steering rack to steering gear, and in the ball joints of a steering bones). 
  • The lack of physical feedback to the driver. It is impossible to control a fast Lego car even with RC proportional system since the driver can not feel the car. Real drivers can hear the noise of the motors, check various sensors in the car, feel most of the bumps and, most importantly, feel the steering wheel resistance (it is well known that of high speed it is harder to steer the wheels).

Summing up, it is nearly impossible to control a Lego car which drive over 12 km/h especially of the rough terrain. To understand that clearly, just take a look at fast RC cars which has a tendency to roll over onto their roofs :pir-cry_happy:.

Interesting topic! Thanks to @Zerobricks!! 😊

in my opinion more BuWizz/Buggy Motors helps to get faster and get more torque, but as @Daniel-99 already mentioned, it is difficult to control these cars with a cellphone. Unfortunately there is no good solution available to control BuWizz 😕

Share this post


Link to post
Share on other sites
56 minutes ago, FriedlS said:

Interesting topic! Thanks to @Zerobricks!! 😊

in my opinion more BuWizz/Buggy Motors helps to get faster and get more torque, but as @Daniel-99 already mentioned, it is difficult to control these cars with a cellphone. Unfortunately there is no good solution available to control BuWizz 😕

Yes it helps indeed, but the usage of many motors in one car contradict the philosophy of real car engineering, in a way I explained in my first comment. 

It is impossible to control 12 km/h car with a cell phone on a rough terrain. Likely, there are bluetooth trackpads available which has a proportional control and can used with Buwizz units. Though I had no opportunity to test one of them yet :pirate-sad. But both physical and proportional control is not enough to make 20 km RC car controllable, you need a physical feedback. Actually, you you have to seat in the car itself :pir-classic:. Nevertheless, it is possible to control a fast RC car on a flat open areas, but it is a little bit boring for me.

Edited by Daniel-99

Share this post


Link to post
Share on other sites

Thank you @Zerobricks

1 hour ago, Zerobricks said:

Here you go, but remember I'm using LDD with new parts added:

I will (try to) import it into studio. :wink:

Edited by Jayden

Share this post


Link to post
Share on other sites
23 minutes ago, Daniel-99 said:

Yes it helps indeed, but the usage of many motors in one car contradict the philosophy of real car engineering, in a way I explained in my first comment. 

It is impossible to control 12 km/h car with a cell phone on a rough terrain. Likely, there are bluetooth trackpads available which has a proportional control and can used with Buwizz units. Though I had no opportunity to test one of them yet :pirate-sad. But both physical and proportional control is not enough to make 20 km RC car controllable, you need a physical feedback. Actually, you you have to seat in the car itself :pir-classic:. Nevertheless, it is possible to control a fast RC car on a flat open areas, but it is a little bit boring for me.

I know this question response not to the topic, but which Bluetooth trackpads for BuWizz are available?? Without using a cellphone as hub?

Share this post


Link to post
Share on other sites
18 hours ago, Zerobricks said:

My previous models used the original and brick-built portal hubs. Planetary hubs do have a few weaknesses compared to the planetary hubs in my opinion though:

  • Larger pivot point which requires a stronger steering mechanism
  • Lower gearing ratio (maximum of 3:1 is possible) means that the usual cardan joint is prone to breaking apart - this could be remedied using the new CV joints
  • The gears are exposed and prone to catching dirt, reducing performance
  • And lastly the last axle - the one driving the gears does tends to bend out of shape, especially with heavier models since it has to carry the final generated torque of the whole drivetrain
  • Another problem with portal hubs is that due to their lower gearing they require stronger differentials/perpendicular drives. This is why the geraboxes in those models tend to gear down in lower gears instead of fearing up. But gearing down can and does cause the gears to skip - in my case the Tiger 6x6 can skip the 8 tooth gears on the differential casing acting as a low gear when all wheels are blocked. When gearing up in the Widlcat 6x6, there are no such issues.

I agree with you on these points about portal hubs, for me the most annoying is the terrible steering geometry, not only because they need a stronger mechanism, but also because they require a lot of space. Furthermore, you can't put a locked differential into a portal axle, because of the large scrub radius the wheels are actually travelling a noticeable distance in the opposite direction, and that  would twist the drive axle. In my model steered with an M motor and linear actuator, the motor was not strong enough to steer it in place when locked (even without weight on it), because of this twist effect (in this case the drive axle was strong enough to stop the steering).

Anyway, when I said I'd like to compare non-planetary hubs with the above mentioned gearing, I actually meant plain hubs, not even portals, that would have a similar gearing to your setup as @Daniel-99 has calculated. However, I have forgotten about steered front wheel drive, which would be only possible with old CV joints in case of a plain hub, which I think is not a great idea for high-power fast applications (apart from maybe popping apart, I think they would wear pretty fast, and also steering radius is bad). So the plain hubs should be reserved for RWD off-roaders only, nonetheless a trophy truck could still fit that design.

@FriedlS, currently I am using BrickController2 app with a gamepad for Buwizz, that's my current best option. It already gives much better controllability than the touch-screen.

Share this post


Link to post
Share on other sites
31 minutes ago, gyenesvi said:

Anyway, when I said I'd like to compare non-planetary hubs with the above mentioned gearing, I actually meant plain hubs, not even portals, that would have a similar gearing to your setup as @Daniel-99 has calculated. However, I have forgotten about steered front wheel drive, which would be only possible with old CV joints in case of a plain hub, which I think is not a great idea for high-power fast applications (apart from maybe popping apart, I think they would wear pretty fast, and also steering radius is bad). So the plain hubs should be reserved for RWD off-roaders only, nonetheless a trophy truck could still fit that design.

Talk about plain hubs, I do hope and expect LEGO to release a version that can accept the new larger CV joint without any gearing. This would open up option to be used for faster models in conjunction with the new differential from the Ferrari. For now I make due with using new CV joints inside the normal hubs, though it's not a perfect solution and requires a second inner joint.

Share this post


Link to post
Share on other sites

In one of previous posts you mentioned old gray differentials and differential from Ferrari; does differential from 42109 set have bigger friction?

Share this post


Link to post
Share on other sites
18 minutes ago, 1gor said:

In one of previous posts you mentioned old gray differentials and differential from Ferrari; does differential from 42109 set have bigger friction?

From my experience the 42109's differential works best when driven by a 28 tooth gear bevel gear inside the 7x11 frame (perpendicular). When using a 12 tooth bevel gear to drive it ((perpendicular)) it's more likely to skip than even the old 28 tooth differential.

Share this post


Link to post
Share on other sites
7 minutes ago, Zerobricks said:

From my experience the 42109's differential works best when driven by a 28 tooth gear bevel gear inside the 7x11 frame (perpendicular). When using a 12 tooth bevel gear to drive it ((perpendicular)) it's more likely to skip than even the old 28 tooth differential.

That is what I was wondering; why when I use PF motors somehow older gray differential it seems to work more smooth?

Only to me Ferrari differential gears look even stronger than gray differential, but big question is wether is it usable for normal indoor use on models that have less than 2 - 2.5 kg

Share this post


Link to post
Share on other sites
1 hour ago, 1gor said:

In one of previous posts you mentioned old gray differentials and differential from Ferrari; does differential from 42109 set have bigger friction?

I think the heavy-duty diffs with the read 28T gear may have bigger friction that the Ferrari's because the read gear and the 12T spur gear are double bevel and are both rubbing against the 5x7 frame (how it's typically built), while the yellow gears are not double bevel, so less friction is expected at the frame. Also, the teeth are more like a crown gear which has less friction I guess. Similarly, the old diff is not double bevel, so it's not rubbing against the frame.

1 hour ago, 1gor said:

Only to me Ferrari differential gears look even stronger than gray differential, but big question is wether is it usable for normal indoor use on models that have less than 2 - 2.5 kg

I'm sure it is, it's probably designed for that use case. The only thing is that the gearing is slightly slower than that of the old grey diff (14:22 = 0.63 vs 20:28 = 0.71), which may or may not be good depending on the use case.

However, the above slight difference gave me a really interesting idea to try once I get some of those diffs. In rock crawlers, the front wheels often has about 10% overdrive compared to the rear ones to pull the car onto the rock more than to push it (and flip it backwards). With using the old grey diff at the front and the new yellow diff at the back, it would be possible to achieve that ~10% speed difference in an elegant way (otherwise it would be really complicated and would not worth it). The only downside is that the yellow diff cannot be locked..

Share this post


Link to post
Share on other sites
1 hour ago, 1gor said:

That is what I was wondering; why when I use PF motors somehow older gray differential it seems to work more smooth?

Only to me Ferrari differential gears look even stronger than gray differential, but big question is wether is it usable for normal indoor use on models that have less than 2 - 2.5 kg

I have a smillar experience, i think it's simple down to how you drive it. If you're using a 28 tooth gear as mentioned before, it will of course have a smoother and more efficient transfter of power than a 12 tooth gear. Generally the bigger the gears you use in the driveline, the more efficient and smooth rolling they are.

1 minute ago, gyenesvi said:

I think the heavy-duty diffs with the read 28T gear may have bigger friction that the Ferrari's because the read gear and the 12T spur gear are double bevel and are both rubbing against the 5x7 frame (how it's typically built), while the yellow gears are not double bevel, so less friction is expected at the frame. Also, the teeth are more like a crown gear which has less friction I guess. Similarly, the old diff is not double bevel, so it's not rubbing against the frame.

I'm sure it is, it's probably designed for that use case. The only thing is that the gearing is slightly slower than that of the old grey diff (14:22 = 0.63 vs 20:28 = 0.71), which may or may not be good depending on the use case.

However, the above slight difference gave me a really interesting idea to try once I get some of those diffs. In rock crawlers, the front wheels often has about 10% overdrive compared to the rear ones to pull the car onto the rock more than to push it (and flip it backwards). With using the old grey diff at the front and the new yellow diff at the back, it would be possible to achieve that ~10% speed difference in an elegant way (otherwise it would be really complicated and would not worth it). The only downside is that the yellow diff cannot be locked..

Yes, the 12 tooth gear has to carry the entire load, while spinning much faster than when using a bigger gear which needs to spin slower, therebye having lower fuction.

The yellow diffs can be locked, the gray casing is still the same.

Share this post


Link to post
Share on other sites
1 minute ago, Zerobricks said:

The yellow diffs can be locked, the gray casing is still the same.

Oh sure, indeed, what I wanted to say is they cannot be built permanently locked, without using that locker of the case, in a way that fits into the 5x7 frame. With the old grey diff that could be done by replacing the gears with a locking bridge, and in case of the red gear on the heavy-duty diff, the whole can be replaced with a 28T double bevel gear to get a permanently locked axle with the same gearing ratio. Neither of these tricks can be done with the new yellow diff I guess.

Share this post


Link to post
Share on other sites
5 minutes ago, Zerobricks said:

I have a smillar experience, i think it's simple down to how you drive it. If you're using a 28 tooth gear as mentioned before, it will of course have a smoother and more efficient transfter of power than a 12 tooth gear. Generally the bigger the gears you use in the driveline, the more efficient and smooth rolling they are.

 

I notice that when using PF XL motors (on models that have enough space for them) when using 40 and 24 tooth gears and not 8 gears to make reduction

Share this post


Link to post
Share on other sites
9 minutes ago, 1gor said:

I notice that when using PF XL motors (on models that have enough space for them) when using 40 and 24 tooth gears and not 8 gears to make reduction

Exactly. And I used the same technique in Spano GTA and in the Speedbreakers. Bigger gears are simply, smoother, more efficient and they can carry much higher loads.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.