[WIP] Greyhound - 4WD RC Buggy with BuWizz 2 - Redesigned wheel hubs

[Didumos69]

On 11/29/2017 at 9:55 PM, agrof said:

I am away from home now, so I can not check, but could be a solution to block the 2L frictionless pin by putting a 3L lightsaber piece into - if it fits, or similar (screwdriver, minifig accessories). With 2L friction pin it will for sure work, and I don't think it would effect the working too much. Tomorrow evening earliest I can show You examples, if needed.

On 11/29/2017 at 9:59 PM, Isak said:

@Didumos69 I guess my question would be do you need to use a frictionless pin? A standard friction black pin would probably be fine seeing as the car will weigh quite a ton. It shouldn't add hardly any friction to the system

On 11/29/2017 at 10:06 PM, Leonardo da Bricki said:

@Didumos69 If there is space, you could put a flick-missile pin with the bar facing towards the rack. Slip a 1/2 pin over it, and that should hold it really well. I've done this before, and usually need pliers to pull the pin off. It makes for an incredibly strong construction.

On 11/30/2017 at 7:04 AM, Jurss said:

From my experience, this connection of steering rod to hub will be pretty loosy with that frictionless 2L pin and 2L axle. It can pretty much affect steering directness,

Thanks for the suggestions and remarks guys! I guess I will have to try this and see how it behaves. If it would make steering sloppy, I will have to figure out another way or skip Ackermann steering. I'm doing my utmost best to eliminate slack in everything moving: turn-table based wheel hubs, gear rack sliders etc., so it won't make much sense to introduce sloppyness in this connection. Stll, if anyone could test how a bar inserted in the frictionless pin would effect it's sloppyness and it's friction, that would be very useful. I don't have any parts with bar-ends myself.

On 11/30/2017 at 6:22 AM, Victor Imaginator said:

Awesome WIP. I will follow this topic with great interest)

On 11/29/2017 at 9:59 PM, kbalage said:

Wow, this buggy looks really exciting, will follow the build for sure!

Thanks Victor and @kbalage!

On 11/29/2017 at 9:59 PM, kbalage said:

As I see you'll use the direct output of the motors, I wonder if there's any possibility to gear it up a little bit for more speed (not sure if the gearing would fit for the front axle), it depends on the final weight as well.

On 11/29/2017 at 10:06 PM, Leonardo da Bricki said:

@kbalage Based on the size, gearing up would reduce performance here. The L-motors wouldn't have the necessary torque.

Gearing up the front-axles sure won't fit. In the back I could make the gear ratio 12:20. Would it make sense to only gear up the rear axles? As for the size and weight, it may seem big, but it really is only 1 stud wider (due to the custom wheel hubs) and 1 stud longer than @agrof's class 1 buggy.

Edited December 1, 2017 by Didumos69

[kbalage]

4 minutes ago, Didumos69 said:

Gearing up the front-axles sure won't fit. In the back I could make the gear ratio 12:20. Would it make sense to only gear up the rear axles? As for the size and weight, it may seem big, but it really is only 1 stud wider (due to the custom wheel hubs) and 1 stud longer than @agrof's class 1 buggy.

I think gearing up only the rear axles would make more trouble than benefit, if there's no room in the front axles for it then don't bother with it. 
@Leonardo da Bricki as I saw agrof's buggy running pretty well (for PF) with only 2 L motors I think it could handle some gearing if you have 4WD. The overall size difference is not that significant, it could work if the weight can be kept in the same range. Obviously if it doesn't fit then there's no point to talk about it :)

I made a dummy chassis for one of my cars to test the different gearing ratios and added the necessary amount of weight to simulate the complete body. It can be useful before trying to squeeze every part in the final design :)

[Tommy Styrvoky]

I was wondering with the hub design, isn't there issues with part collisions inside of the hub, as LDD won't allow that part to be placed inside. Maybe an alternative design like this would work the same function, but fit better? Maybe for gearing it you could use the turntable itself for getting some reduction.

Another thought would be if you plan to use a sbrick or buzwizz, I think it would be possible to decrease the maximum power to the front motors if they are on seperate channels, thus the max speed being the same as the rear motors with the reduction.

Edited December 1, 2017 by Tommy Styrvoky

[Didumos69]

1 hour ago, Tommy Styrvoky said:

was wondering with the hub design, isn't there issues with part collisions inside of the hub, as LDD won't allow that part to be placed inside. Maybe an alternative design like this would work the same function, but fit better?

Thanks Tommy.

I don't really understand what you mean. I don't see what is different in your image, besides the omitted belt wheel and 2l pins. Would you care to elaborate on what's the difference?

It's the axle-bush connectors that are not allowed by LDD. However in practice the assembly fits well. It sits tight, but that adds to stability. I tried replacing the axle-bush connector with a  and use a 1.5l pin instead of the pin with axle, this fits in LDD, but it feels less rigid.

1 hour ago, Tommy Styrvoky said:

Maybe for gearing it you could use the turntable itself for getting some reduction.

I tried to do that, but it's not easy to mesh with a 28 tooth turn table inside the rim. For this model I will not be using the turntable for gearing.

1 hour ago, Tommy Styrvoky said:

Another thought would be if you plan to use a sbrick or buzwizz, I think it would be possible to decrease the maximum power to the front motors if they are on seperate channels, thus the max speed being the same as the rear motors with the reduction.

That's the type of info I need! I'm planning to use the SBrick, but I'm a.newbee when it comes to motorized building, so I can use this kind of info. This way I can experiment with different gearing in the back. Thanks!

[Tommy Styrvoky]

10 minutes ago, Didumos69 said:

Thanks Tommy.

I don't really understand what you mean. I don't see what is different in your image, besides the omitted belt wheel and 2l pins. Would you care to elaborate on what's the difference?

 

I was just including the hub structure, it is missing the belt wheel and pins for both, though I thought this was a more compact design, and it would fit nicely in the hub.

[Didumos69]

1 minute ago, Tommy Styrvoky said:

I was just including the hub structure, it is missing the belt wheel and pins for both, though I thought this was a more compact design, and it would fit nicely in the hub.

I think I understand now. You're version is the one to the right, right? That's an option too and it fits the smaller rim too. However, I wanted to have a solution with pins through the turn-table pinholes and not with axles. Just to minimize slack to the max. I discussed this in the turn-table hub thread.

[Didumos69]

I redid most of the front axles. I had a hard time installing large shocks in a way that doesn't rise far above the rest of the unit. The shocks are placed upside-down with reason. I needed the axle holes to make a good connection with the wishbones. Depending on the final weight I will use two hard shocks or one hard and one soft shock on each side. I had to replace the thin suspension arms and as a consequence I had to get rid of the bottom and top frames. And finally I changed the Ackermann geometry such that the steering rods are aligned perfectly transversal.

Edited December 3, 2017 by Didumos69

[Didumos69]

Now that I have a good feeling about the front axles, I started working on the main structure of the chassis. The front axles are somewhat inclined (about 5 degrees) to obtain caster. A little more modest than @agrof's class 1 buggy, because 4WD ususally comes with less caster than RWD. The tail is - again - based on the (5,12,13)-triangle. The length-wise structure is more or less done. Now I need to work on the width-wise structure. In that process I will also connect the trailing arms in the back. They are still floating now.

One question I'm playing with, is what kind of battery box I should use. And can I pair two battery boxes? I'm planning to use SBrick and will probably not do anything with BuWizz.

[Isamudyson]

with no body yet it looks beautiful

[AkiyamaWataru]

@Didumos69 the easierst way to pair Batteryboxes is to use 2 and use 2 sbricks aswell. And then you can think about how you will be connecting the Sbricks to the motors. With your setup i would use one SBrick for front axle (motors, steering) and the other one for rear axle. What you should consider is ease of reach for the BB's.  With standard BB's you could put them at the side with a vertical drop mechanism. Putting most of its weight to the center of that car.

[Didumos69]

4 hours ago, AkiyamaWataru said:

@Didumos69 the easierst way to pair Batteryboxes is to use 2 and use 2 sbricks aswell. And then you can think about how you will be connecting the Sbricks to the motors. With your setup i would use one SBrick for front axle (motors, steering) and the other one for rear axle. What you should consider is ease of reach for the BB's.  With standard BB's you could put them at the side with a vertical drop mechanism. Putting most of its weight to the center of that car.

Thanks, that makes sense. Today I also looked into the BuWizz. For someone that doesn't have any motors, battery boxes, receivers etc, having a battery box and controller in one unit might be quite convenient.

[kbalage]

22 minutes ago, Didumos69 said:

Thanks, that makes sense. Today I also looked into the BuWizz. For someone that doesn't have any motors, battery boxes, receivers etc, having a battery box and controller in one unit might be quite convenient.

One thing you should consider is how comfortable would you be with the smartphone touch controls versus the physical controls what Lego offers. I know the power functions remote has it's limitations but for a lot of people it's still more convenient than a touch interface. SBrick has a solution for this, but that requires additional purchase - you can connect a (compatible) gamepad to your phone and use it to control the SBrick. Unfortunately BuWizz does not have this option yet.

[Didumos69]

14 hours ago, kbalage said:

One thing you should consider is how comfortable would you be with the smartphone touch controls versus the physical controls what Lego offers. I know the power functions remote has it's limitations but for a lot of people it's still more convenient than a touch interface. SBrick has a solution for this, but that requires additional purchase - you can connect a (compatible) gamepad to your phone and use it to control the SBrick. Unfortunately BuWizz does not have this option yet.

Thanks @kbalage, also for your response in the other thread. I'm new to RC anyway, so I might as well get adjusted to the touch interface anyway. I'm more and more tempted to go BuWizz, because performance is the main objective for this model. I still have one question. With 4 L-motors and 1 servo, do I need two battery boxes or can I work with one?

Update: I have built the front axles. I used custom placeholders for the motors, for I don't own any yet. I had to make a few minor adjustments to make it work, but I'm actually quite content with the result. It has more travel than I expected: 6+ studs travel . I played a little with the steering rods. The steering angle and Ackermann effect are optimal when I move the steering pivot one stud forward. That gives a little toe out (independent of suspension compression), but I have learned from @nicjasno's videos that a little toe-out for driven front axles is actually quite convenient. Due to slack in the setup (yes, there still is a little slack ) traction will pull the wheels forward and align them perfectly parallel when driving forward. So if there are no objections, I will stick to a little toe-out.

On 11/29/2017 at 9:55 PM, agrof said:

With 2L friction pin it will for sure work, and I don't think it would effect the working too much.

I used a 2L friction pin and it works. It doesn't influence the suspension .

Edited December 8, 2017 by Didumos69

[Didumos69]

On 12/6/2017 at 2:53 PM, LvdH said:

This looks truly amazing! Your builds amaze me every single time, especially with their rigidity. 

One question, how in the world do you allign all those pieces in LDD? For me it never fits. 

Thanks! When I have a section that is inclined properly and want to add a subassembly, like for instance the steering rods in the front axles, I copy-paste an axle from that section with the correct rotation. Then I add a new bush and place it somewhere floating. Then I select the subassembly and the bush, and shove the bush over the axle. Now the assembly has the same inclination and can be added without causing problems.

Maybe interesting to know: I made use of this type of connection between the beams running on top and underneath the front module to the 4 axles holding the suspension arms. This does not obstruct the arms or the motors in rotating and makes a nice rigid connection. The axles sit tight against the connectors without stressing any parts.

Edited December 8, 2017 by Didumos69

[kbalage]

4 hours ago, Didumos69 said:

Thanks @kbalage, also for your response in the other thread. I'm new to RC anyway, so I might as well get adjusted to the touch interface anyway. I'm more and more tempted to go BuWizz, because performance is the main objective for this model. I still have one question. With 4 L-motors and 1 servo, do I need two battery boxes or can I work with one?

 

As I did not have detailed experience with this configuration (4L motors) I decided to create you a little test video so you can compare the performance of the different solutions and probably it'll help you to choose the optimal solution. I used PF rechargeable battery boxes as I did not have 12 fully charged AA or AAA batteries but the performance should be similar. The vehicle does not have steering as it was only a quick test and I think the servo does not have a big impact on the performance. The car is exactly 1kg without batteries or receivers. 

As you can see the speed difference is not that significant, probably it would be with more weight added. I can test with extra weight later once you know how heavy your car will be.

The stress test already shows the weakness of the 1 battery solutions, the only single battery version that survives here is BuWizz in normal mode.

The climb test shows the weakness of the v1 IR receivers, it cannot climb well even with 2 of them. Unfortunately the V2 is more expensive and you cannot get it with a set nowdays.

All in all the 2 BuWizz version will give you the most power, but I think that's the most expensive as well. BuWizz just released their v2 unit which will give you slightly more performance. On the downside their software is still pretty unpolished and lacks customization. SBrick can be customized well and can also use a gamepad, but there you need to buy separate battery box(es).

I hope this video will help, let me know if you need more information.

[JonathanM]

7 hours ago, Didumos69 said:

I copy-paste an axle from that section with the correct rotation. Then I add a new bush and place it somewhere floating. Then I select the subassembly and the bush, and shove the bush over the axle. Now the assembly has the same inclination and can be added without causing problems.

Genius. Am totally using this trick!

3 hours ago, kbalage said:

Unfortunately the V2 is more expensive and you cannot get it with a set nowdays.

Hmm, I thought the newer V1's (e.g. in 42065) used a similarly spec'd motor driver as in the V2's?

[Didumos69]

Wow @kbalage,.that's an awesome comparison, thank you very much! I'm afraid I'm not going to wait buying motors etc. until I know the exact weight. It will most likely be the two BuWizzes setup.

[BusterHaus]

My experience with toe-out hasn't been very good. It slows down the car, but maybe balloon tires will have less problems because of the smaller contact area with the ground. 

Are you planning to lubricate the small turntables? Their friction will sap some power from the motors. 

Beyond those two points everything looks great. I've been following the build since day 1 and it is a pleasure to watch the car evolve. 

 

[PorkyMonster]

IMHO, its a pity that the design does not allow for a gearbox, and there is no space for gearing up the wheels individually... because, based on my calculation, it can only go up to 7 kmh , based on wheels of 94.8 mm diameter, and the maximum 390 rpm that PF-L motor can do at 9 volts (slightly more for buwizz at 10 volts)...

One real issue I see is that of the toe-out - because you don't have other geometries like caster (ok, you have 5 degrees... which is rather negligible and can easily be canceled out by your toe-out) and kpi as well... so driving this buggy in a straight line may be challenging. 

Edited December 9, 2017 by PorkyMonster

[Didumos69]

19 hours ago, BusterHaus said:

My experience with toe-out hasn't been very good. It slows down the car, but maybe balloon tires will have less problems because of the smaller contact area with the ground.

15 hours ago, PorkyMonster said:

One real issue I see is that of the toe-out...

So I decided to revert to none-toe geometry. I'll keep the idea of toe-out in the back of my mind when I start test-driving. This meant I needed to adjust the steering rods, which was quite challenging, but this setup seems to do the job perfectly:

It may seem that I'm working with a lot of space, but it all comes very precise. The steering rods tilt a little while steering, with the suspension fully expanded/compressed. So I had to remove and replace some parts to prevent the rods from sticking behind small ridges, for instance at the sides of these connectors. Also, the steering rods disappear partly inbetween the A-arms while steering, which confines them two max 2 studs height.

19 hours ago, BusterHaus said:

Are you planning to lubricate the small turntables? Their friction will sap some power from the motors.

I'm not planning to. They feel very smooth running. I hope the reduced slack will compensate for the little extra friction. Btw, I will eventually be using the Unimog tires or Claas tires. I know Claas tires don't have the right profile, but their size fits better I think.

19 hours ago, BusterHaus said:

Beyond those two points everything looks great. I've been following the build since day 1 and it is a pleasure to watch the car evolve.

Thanks!

15 hours ago, PorkyMonster said:

IMHO, its a pity that the design does not allow for a gearbox, and there is no space for gearing up the wheels individually... because, based on my calculation, it can only go up to 7 kmh , based on wheels of 94.8 mm diameter, and the maximum 390 rpm that PF-L motor can do at 9 volts (slightly more for buwizz at 10 volts)...

For me the main idea behind this model is to integrate all motors in the suspension. I realized it would give me max 7km/h in advance, but when I see the last scene in @kbalage's test video, where the vehicle climbs a 33 degree slope, I know what I'm aiming for. I want this vehicle to ride a rough off-road track with the same ease.

15 hours ago, PorkyMonster said:

... - because you don't have other geometries like caster (ok, you have 5 degrees... which is rather negligible and can easily be canceled out by your toe-out) and kpi as well... so driving this buggy in a straight line may be challenging.

Well, I am much inspired by this model (even though it has a solid rear axle) and I noticed that a modest caster angle is actually quite common for 4WD buggy's.

Edited December 9, 2017 by Didumos69

[PorkyMonster]

12 hours ago, Didumos69 said:

For me the main idea behind this model is to integrate all motors in the suspension. I realized it would give me max 7km/h in advance, but when I see the last scene in @kbalage's test video, where the vehicle climbs a 33 degree slope, I know what I'm aiming for. I want this vehicle to ride a rough off-road track with the same ease.

12 hours ago, Didumos69 said:

Well, I am much inspired by this model (even though it has a solid rear axle) and I noticed that a modest caster angle is actually quite common for 4WD buggy's.

Right... for off-road, and at 7kph, its fine that there is slight toe-out and little caster. In fact, one can easily get away even with negative caster (like so many Lego MOCs before... LOL). I actually thought you were gunning for higher speed and on-road when you used 4 motors, queried about Buwizz, included caster, and so on... haha... my bad.

 

[Didumos69]

I made a few more improvements to the front module. There was a problem with one of the gearrack sliders. The one at the front side of the gearrack collided with the steering rod when it moved outward. So I refactored the entire gearrack support. In addition, I inserted minifig hammers into the 2L pins connecting the steering rods to the wheel hubs. That works very well. I'm now quite confident the front module will endure. Here are two renders of the front module with the steering, drive, suspension and bracing separated:

Edited December 13, 2017 by Didumos69

[Rudivdk]

Wow, you've got some crazy techniques going on there when it comes to bracing and rigidity. And I thought I was overdoing it when I built my familycar....

Very nice job sofar, this thing might end up surviving the Topgear Toyota Landcruiser tests...

[Didumos69]

On 12/13/2017 at 10:27 AM, Rudivdk said:

Wow, you've got some crazy techniques going on there when it comes to bracing and rigidity. And I thought I was overdoing it when I built my familycar....

Very nice job sofar, this thing might end up surviving the Topgear Toyota Landcruiser tests...

Thanks! The whole front module is mounted to two lengthwise beams. The difficult part was to firmly connect those beams to the main structure and to introduce a caster angle at the same time.

I continued working on the main structure. I now also have most of the width-wise structure done and integrated two removable BuWizzes. Also the trailing arms of the rear suspension are completely integrated now. Only need to add a connection between the topside of the front module and the sides of the main structure and then the chassis design should be done.

Edited December 15, 2017 by Didumos69

[DugaldIC]

This thing is looking more rugged than your supercar. I can't wait to see some footage of it ripping around it'll fly with four L motors and two buwizz.