[MOC] Greyhound 4WD RC Buggy /w instructions - Improved rim-hub connection

[Didumos69]

20 hours ago, Yoseep said:

I now replaced the pin with pinhole with an axle with pinhole. I'm writing to ask whether the motor thin liftarm is actually supposed to rotate on that friction pin with pinhole, or did I misread the instructions, cause I really don't remember it being like that the first time around. But it was a long time ago. Also asking because if I get it wrong now, It'll be a slog to rebuild this part.

I can confirm the 3l thin lift arms actually rotates around that pin. Because of the long suspension arms the rotation / suspension travel ratio is relatively small. So I preferred having a firm grip on the motors over a frictionless rotation.

I think your idea may work, but I'm not sure if it increases chances of detached parts. You could try pulling the motor assembly out of its pivot points to compare your solution with the original one.

[Didumos69]

20 hours ago, Teo LEGO Technic said:

Amazing model as always, it's just so satisfying watching that suspension work  . How did you ever get it to run so smooth? Is it something to do with the geometry?

Thanks! It all comes down to suspension. The suspension arms should be able to move smoothly and as a rule of thumb the suspension should be compressed halfway its overall travel under the vehicle's own weight. That will allow the arms to expand as much as compress while driving.

[Teo LEGO Technic]

4 hours ago, Didumos69 said:

Thanks! It all comes down to suspension. The suspension arms should be able to move smoothly and as a rule of thumb the suspension should be compressed halfway its overall travel under the vehicle's own weight. That will allow the arms to expand as much as compress while driving.

Awesome, great advice. I'll be sure to apply that in future MOCs  

[Yoseep]

19 hours ago, Didumos69 said:

I can confirm the 3l thin lift arms actually rotates around that pin. Because of the long suspension arms the rotation / suspension travel ratio is relatively small. So I preferred having a firm grip on the motors over a frictionless rotation.

I think your idea may work, but I'm not sure if it increases chances of detached parts. You could try pulling the motor assembly out of its pivot points to compare your solution with the original one.

Thanks! Was hesitant for a bit, but later the motors got sandwitched in such a tight array of beams composing the double wishbone that it seems even this small loss in retention won't cause any trouble. Tried shaking and pulling in random directions and didn't bulge. Of course, pushing it by driving hard, four stronger Cada L motors for that, will give more truthful results, but I'm optimistic.

And I feel kinda rude about the previous, first post, jumping to a specific without firstly aknowledging how awesome this moc is. Just assembling it makes for an unworldly experience and I would advise everyone to try it. Even without buwizz or batteries. Hell, even without motors and wheels. Just marvelling at the intricate connections that give both rock solid sturdiness at optimized weight is worth the trip. Then I heard it's quite capable as a vehicle as well, haha. Can't wait to try. First time was improvised with two large and heavy Lego AA battery boxes that barely made it move.

Planning to amass a collection / timeline of official supercars that show their advancement through Lego history and this, though a buggy, will stay in it as an shiny reminder of what it really takes to bridge the gap from fragile car statue to actual RC vehicle when the size and weight start taking a toll on pin-joined pieces of flexible plastic and relatively weak motors. Marvellous.

[amorti]

@Yoseep those CaDA monsters pack a punch.

In the front you'll definitely snap plastic universal joints in a second, no matter how many rubber bands you twist around them. CaDA joints are the strongest metal ones I've found so far (except darkicedesign, but the use of a grub screw to tighten against an axle is no Bueno).

In the rear you'll definitely have crunching from the 12 tooth gears. If you look through the thread you'll see I've given some options to strengthen the rear swing arms. Those mods work fine for mouldking motors, however CaDA motors are even stronger. I think you'll need some carbon axles out from the motors, as plastic axles bend in the middle and allow the teeth to skip.

Also check out my suggestion of an even tighter method to bind the wheel to the hub. It helps the universal joints a lot by keeping movement in the expected plane and putting the wheel's crosshole nearer the power.

Edited July 24, 2021 by amorti

[koboltzz]

On 7/24/2021 at 2:04 PM, amorti said:

Those mods work fine for mouldking motors, however CaDA motors are even stronger.

Thanks for this information, but how do you know exactly? And how do you define 'stronger'? Torque or rpm?

Is there a torque test with LEGO vs MK vs CADA motors somewhere on the internet?

[amorti]

3 hours ago, koboltzz said:

Thanks for this information, but how do you know exactly? And how do you define 'stronger'? Torque or rpm?

Is there a torque test with LEGO vs MK vs CADA motors somewhere on the internet?

I know it simply because I have all of those available and have tested them side by side.

In the order stated, the motors have both more torque and more rpm. The cost of course, is that they pull more amps. I know this because if how easy it is to trip a Buwizz safety fuse with two of each of the motors attached.

With Lego L motors you can easily run two in ludicrous mode, with mouldking you're ok in normal but will often trip the fuse in fast, and with CaDA you can only use normal, but even then it's still fastest and most powerful.

You don't get something for nothing!

But yes, there are several tests out there. Most scientific is probably this:

https://youtu.be/oGr4t4ouys8

[koboltzz]

19 minutes ago, amorti said:

I know it simply because I have all of those available and have tested them side by side.

In the order stated, the motors have both more torque and more rpm. The cost of course, is that they pull more amps. I know this because if how easy it is to trip a Buwizz safety fuse with two of each of the motors attached.

With Lego L motors you can easily run two in ludicrous mode, with mouldking you're ok in normal but will often trip the fuse in fast, and with CaDA you can only use normal, but even then it's still fastest and most powerful.

You don't get something for nothing!

But yes, there are several tests out there. Most scientific is probably this:

https://youtu.be/oGr4t4ouys8

You do not need to feel attacked :)

About which order do you speak? You are saying that CADA l motor has more torque with 7.2 V than LEGO with 11.2 V... I would very much doubt that.

The video you linked is not scientific at all. And also in his other videos, he has forgotten to test/calculate torque. In most if not any cases more rpm means weaker torque. Again, please don't take it personal, it's fine when you have a different opinion.

[amorti]

5 minutes ago, koboltzz said:

About which order do you speak? You are saying that CADA l motor has more torque with 7.2 V than LEGO with 11.2 V.

I do mean this :)

Well, I suppose more precisely I mean it draws more current. I don't know if it's the same thing.

And it's fine, I don't feel attacked, honestly. I just try to speak in plain words on this forum, where I know a lot of users aren't native English speakers, that's all.

Custombricks.de keeps the CaDA motor in stock for 13,99€. Why not order yourself one, build a simple chassis, and see what it will manage with each motor? Both for speed, and either a scientific torque test if you have the equipment and interest, or a simple ramp climbing test.

I believe you'll be surprised. And I believe you'll buy more CaDA motors!

Edited July 29, 2021 by amorti

[koboltzz]

1 minute ago, amorti said:

 I don't feel attacked, honestly.

 

Custombricks.de keeps the CaDA motor in stock for 13,99€.

Okay, glad to hear tha.

Yes, I will do and report since we all want the most powerful Greyhound :)

[amorti]

You'll definitely want to strengthen a few things, metal universal joints will be essential in the front and probably carbon axles in the rear swing arms too, unless you drive it carefully with no hard starts and stops.

I'll look forward to a video 

[koboltzz]

14 minutes ago, amorti said:

Probably carbon axles in the rear swing arms too.

Already have the darkicedesign universal joints. Where exactly to change the axles to carbon... and where do I get these?

[amorti]

3 minutes ago, koboltzz said:

Already have the darkicedesign universal joints. Where exactly to change the axles to carbon... and where do I get these?

Darkicedesign joints are annoying because the little screws get loose. I suggest adding loctite.

Freakware offers CaDA metal joints, they're the best available.

Darkicedesign does metal axles which would work well. I have a couple carbon axles in Chinese sets, I don't know a European supplier of them as loose parts I only saw them on Ali.

Edited July 29, 2021 by amorti

[koboltzz]

On 7/29/2021 at 8:04 PM, amorti said:

Both for speed, and either a scientific torque test if you have the equipment and interest, or a simple ramp climbing test.

 

I believe you'll be surprised. And I believe you'll buy more CaDA motors!

I have now compared a CADA L motor with a LEGO and a Mould King motor. As I suspected, the torque on the fast CADA motors is massively worse compared to the other two.

[amorti]

8 minutes ago, koboltzz said:

I have now compared a CADA L motor with a LEGO and a Mould King motor. As I suspected, the torque on the fast CADA motors is massively worse compared to the other two.

Are we both talking about the CaDA Pro motor, the square/boxy shaped one? Sorry, but I don't see that it can have less torque than the Lego motor.

Two of them can pull Brunojj1's Ferrari with 3236 Parts at a respectable speed, including spinning up the tyres. You just can't do that with two Lego L-motors.

Also, you have to make it fair. If the CaDA motor spins at twice the speed of a Lego motor, you need to gear it down half to test their torque.

They are power-hungry. If you tested them on a power source that couldn't give enough power, they would likely show weaker.

[koboltzz]

19 hours ago, amorti said:

Are we both talking about the CaDA Pro motor, the square/boxy shaped one?

Yes, exactly these. Lego and Mouldking L Motors can lift up vertically 770g lead (connected by wire directly to short axle) with 9V. CADA Pro motor are faster, but don't have the torque to lift the lead. I think they are a bad decision for an offroader like this greyhound.

[amorti]

5 hours ago, koboltzz said:

Yes, exactly these. Lego and Mouldking L Motors can lift up vertically 770g lead (connected by wire directly to short axle) with 9V. CADA Pro motor are faster, but don't have the torque to lift the lead. I think they are a bad decision for an offroader like this greyhound.

Now I follow.

Even if the CaDA motors have more power overall (I still believe they have), you can't gear down in this model, so it's no use.

[koboltzz]

On 8/13/2021 at 10:10 PM, amorti said:

Now I follow.

Even if the CaDA motors have more power overall (I still believe they have), you can't gear down in this model, so it's no use.

I didn't build and test any gear design, but how much weight the motors can lift with 9V. And since CADA can lift the least, it has the least torque and is a poor choice for an off-road vehicle.

[HectorMB]

Has someone build this MOC with the BuWizz 3.0?

I bough the instructions some time ago, thincking about getting as well a couple of BWs 2.0. Then, the 3.0 came out and i got a pair. Now, aiming to make this MOC i just realized that neither the dimensions of the BW 3.0 are the same then the 2.0 nor the L PF motors are identical to the PU L motors. Then, i have two alternatives, either adapt the MOC to the PU motos and the BW 3.0 or just squeeze in the BW 3.0 and multiplex the PF L Motors. 
 

[amorti]

You'll have more chance to fit the buwizz in place of the technic hub, than PF motors in place of PU motors as the design uses the extra mounting options of the new XL motors integrally in the design. 

Even then the battery box is pretty well integrated, so you'd probably have to replace that lost strength with some frames or liftarms.

[HectorMB]

As I do not have any technic hub (only the bulky 6xAA batteries), I might try to squeeze the BW3.0 instead of the BW 2.0 and maintain the PF L motors. As in the model the BW 2.0 are located in the rear part, it might be feasible to make room (1 extra stud) for the BW 3.0. On the other side, the PF L motors are really integrated in the structure and the dimensions are to different between PF and PU L motors...

Well, I will try to make some pics if I end up a some sort of solution!

[amorti]

11 minutes ago, HectorMB said:

As I do not have any technic hub (only the bulky 6xAA batteries), I might try to squeeze the BW3.0 instead of the BW 2.0 and maintain the PF L motors. As in the model the BW 2.0 are located in the rear part, it might be feasible to make room (1 extra stud) for the BW 3.0. On the other side, the PF L motors are really integrated in the structure and the dimensions are to different between PF and PU L motors...

Well, I will try to make some pics if I end up a some sort of solution!

Apologies - I was thinking of Didumos's Rocky, not Greyhound. Ignore my previous post.

The PU motors would be a squeeze, since they're a stud longer. Might be possible though, as looking at my model here, I don't see any real no-go's.

The buwizz 3 is the same but 9 studs long instead of 8, right? You can probably find a way to make that work by leaving out the frame bracketing them at the front and replacing the strength some other way. However, the cables sticking out the ends instead of being on the top could be a problem. Worst case scenario, you could lose the seats and shove the batteries inside the cabin. 

Either way, would be interesting to see a PU motor for the steering, since the PF servos are expensive/rare now, and always were weak/unreliable, and inaccurate.

Edited August 30, 2021 by amorti

[HectorMB]

So, at the end, i made it. To keep everything simple, i maintained the old PF L-motors (changing them will imply to make 1 stud longer each suspension axle, with implications in the general geometry) and just changed the BW brick. To place the BW 3.0 i hace to move the 5x7 frames that encapsidates the BW bricks 1 stud backwards. This, indeed, implied several strucutral modifications. The most challenging one is that, moving the 5x7 frame the resulting structure is less sturdy. Nevertheless, it did not tranlate in any real issue when driving the car. As an example, i almost did not use any new part. When i said "almost" I should mention that I used the 15-long liftarm with alternated stud holes for linking the 5x7 frames. Besides that, all the modifications were done "on the run", so I would not say thay were kind of complicated.

  

Nevertheless, it worths mentioning that the conections to the bricks are tricky. As the of PF L-motors are maintained, as well as the PF M-motor (could be easely changed though), I had only 4 ports available, which meant that i had to multiplex the rear and front motors. Obviusly this is not ideal, as the power may not be enough. But i have to say that given the output of the BW 3.0, the car performed well. 

[New_User]

Made one with custom RC components which consist of 2x3S Lipo, 10A ESC, and chinese RC transmitter and receiver. The chinese Cada Pro L motor is lacking the low range torque, it's not ideal for vehicle of this weight.

Using non Lego servo-motor (GeekServo).

Interestingly, the weight distribution of the vehicle is near perfect 50:50.

Thank You @Didumos69 for the remarkable design.

[Variteck]

thank you.

Could you give us more details about 10A ESC, and chinese RC transmitter and receiver products, and how you connected the PF l motors?