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Definitely possible guys, it'll be a beast I'm sure of it. All of my large RC vehicles used the quad buggy motor setup in the rear, which was more than enough to propel them at blazing speeds. My batteries offered 11-12 volts, but that's not too far off of BuWizz. I never thought of making the front axle driven because I took advantage of high steering angle with my proportional steering. I can imagine that this vehicle will pull like hell off the line, just like a real Tesla :wink: 

Again, I don't have any experience with BuWizz, but my main concern here is how do you plan to avoid ripping apart u-joints and the 3 prong 'CV' joints... In my experience I could never make those last unless I held off the throttle when accelerating and avoided sudden stops, which is no fun. I guess because you don't employ any complex suspension geometry you can focus on the reinforcement of the half-shafts as you do with this design, but I still am skeptical of its longevity when accelerating and steering at the same time, or jamming reverse and forward throttle. Good luck, it's coming together nicely!

Edited by z3_2drive

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1 hour ago, BusterHaus said:

Very nice choice.  Do you have any data from your ripsaw on how long the charge lasts when using 2 buggy motors with a BuWizz? 

Ripsaw lasted some 4 hours on a single charge.

18 minutes ago, z3_2drive said:

Definitely possible guys, it'll be a beast I'm sure of it. All of my large RC vehicles used the quad buggy motor setup in the rear, which was more than enough to propel them at blazing speeds. My batteries offered 11-12 volts, but that's not too far off of BuWizz. I never thought of making the front axle driven because I took advantage of high steering angle with my proportional steering. I can imagine that this vehicle will pull like hell off the line, just like a real Tesla :wink: 

Again, I don't have any experience with BuWizz, but my main concern here is how do you plan to avoid ripping apart u-joints and the 3 prong 'CV' joints... In my experience I could never make those last unless I held off the throttle when accelerating and avoided sudden stops, which is no fun. I guess because you don't employ any complex suspension geometry you can focus on the reinforcement of the half-shafts as you do with this design, but I still am skeptical of its longevity when accelerating and steering at the same time, or jamming reverse and forward throttle. Good luck, it's coming together nicely!

I will see what happens when I have a rolling chassis ready. I plan to load with with some 2 kilograms and see what happens.

In worst case scenario if joints break under heavy braking and accelerating I will smply use PF motors, like 2XL in the back and 2M in front (with correct gearing of course).

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9 hours ago, Zero (Zblj) said:

Regarding the question of too many motors/not enough power:

I think these 3 will do :thumbup:

Just a question regarding buggy motors, I know most builders use one lipo per buggy motor, but does the same hold true for AA battery packs, as I may get a couple buggy motors this summer, and I think I will have to get another lipo battery. As I think the issue with the batteries is the thermal sensor correct?  As it overloads/overheats from the draw from the buggy motors, and it shuts down. 

Also this MOC will be quite nasty when complete, it would be interesting if you keep the chassis light, so it will have ridiculous amount of acceleration and potential for catching some air.:thumbup:

Edited by Tommy Styrvoky

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Here is an update of the model

I finished the chassis and connected Sbricks and used Buwizzes as power source:

800x451.jpg

In low speed the motors have enough power to just barely create some wheelspin. Switching Buwizzes to normal or fast mode makes all 4 wheels to freespin and massive acceleration. BUT accelerating and braking the model too rough triggers Buwizz's protections and resets them to slow mode. The massive accelearation and decelearition also takes a massive toll in U joints, popping them and flatting heads of the CVs. Also the new hubs and wheels have way too much room to play, casing extreme wobbling and vibrations at high speeds.

As much as I want to continue I cant afford to add more weight to already overloaded driveline.

I have following options to resume this project:

1. Exchange RC motors for less powerfull PF motors and continue at this scale

2. Build at a smaller scale, yet with same amount of motors - model will be a lot more crammed but performance will be even crazier with same power at smaller scale

3. Build at smaller scale with reduced amount of RC motors or PF motors with more features and details, but lower performance

 

I am leaning towards option 2, because I really want performance and smaller scale would give even more power to weight ratio.

What do you guys think?

Edited by Zero (Zblj)

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Just a thought but to keep it on the same scale could you eliminate the suspension and make it direct power at the rear wheels and only one u/cv joint at the front eliminating a lot of the drivetrain lash? I know it eliminates the suspension but it would keep your performance and scale, hopefully! 

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3 minutes ago, DugaldIC said:

Just a thought but to keep it on the same scale could you eliminate the suspension and make it direct power at the rear wheels and only one u/cv joint at the front eliminating a lot of the drivetrain lash? I know it eliminates the suspension but it would keep your performance and scale, hopefully! 

I still have a problem with Buwizz's overload protection going off under hard performance. And I can't imagine a 3 kg heavy model going some 15-20 km/h without suspension, it would shake itself apart.

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19 minutes ago, Zero (Zblj) said:

I still have a problem with Buwizz's overload protection going off under hard performance. And I can't imagine a 3 kg heavy model going some 15-20 km/h without suspension, it would shake itself apart.

Ahh true, I didn't think that through! Oh my, best of luck :wink:

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I would say option 2, it would be wonderful to see a model propelled with such power. Too bad it didn't work out with the current setup :look:

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A bit hard to see in the picture, but do you have the RC motors connected to the sbricks and one wire from buwizz to sbrick to provide power?  If so, that may be why the buwizz is going into protection mode.  I haven't read the specs in awhile but I thought the buwizz can handle two RC motors but they need to be using two ports.  Can u try setup again only through buwizz?

I know it's not available on buwizz yet, but a soft start and stop may solve your other issue with u/CV joints.

 

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I played around with Buwizz and figured a way to control two at once, so that i can control 4 RC motors directly. Think I will go down in scale to 56 mm wheels and a symetrical 4x4. Think I will end up with a model X :)

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I am also for option 2, wring out all the juice of those energy bricks! :wink:

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Here is what I came up with:

800x446.jpg

Sadly there is no way I can fit 2 more RC motors in there, but all of the 4 motors there will be fully utilized.

In the end i decided to go for model X and challenge myself with the falcon doors.

I also found a way to control the 4 motors via Buwizz app in a way that also lets me torque vector the left and right side handed motors for better control.

Edited by Zero (Zblj)

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Wow, cannot wait for more, 4 motors sound amazing in such a small vehicle :excited:

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Looking good ?. I think 4 motors is a better choice.

Edited by Aventador2004

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Have you tried mounting the motors as close to the wheels as possible, like in the Fox? Desert752 used 4 rc motors on his SUV racer and had them mounted at the wheel.

 

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I like the decision to reduce scale and weight. Behold the limit of purist construction! What wheels/tires do you plan to use, or are you going to stick with the ones in the LDD model?

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Here is the new, small chassis:

800x451.jpg

The buwuzzes are placed at a slight angle in order not to colide with rear wheels:

800x451.jpg

I took the chasis outside for a run and the results are equally impressive as scary.

At top speed you can easily go out of blutooth range in a matter of seconds.

At cornering the tyres are subjected to really high forces, especially the front ones who do the steering and drive. After 15 min of driving there are already some slight marks on them.

Even though I was driving the chassis on a nice clean playground, some dust and what seems to be grass plant oil stuff got in the hubs, increasing the friction. At home I took them apart and cleaned them.

I can see now why Lego is not keen in making fast or outdoor models, the wear and tear, along the energies involved at high speed is simply too much for brocks to handle.

Work on model will be resumed, though the end model may end up performing too extreme for normal indoor use.

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That sound to overpowered :sweet: Maybe  put the buwizzes in slow mode to reduce wear . Any top speed mesurement ? 

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Wow , that sounds exciting, I can imagine what those beasts can do :devil_laugh: 

Can it do donuts ,drift or burnouts? 

Edited by LXF

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