[MOC] Dragonfly dune buggy

[Daniel-99]

DRAGONFLY Dune Buggy

 

Hello everyone! For a very long time I had a dream to build a dune buggy, and finally, my dream come true! The main goal was to use a C+ electrics instead of Buwizz unit. Of course, I am not the first who attempted to build a buggy. I take an inspiration in Madoca`s Blue Lightning buggy.

 

Technical specifications:

- Light and ridged tubular bodywork

- electrics form 42099 set (controlled with C+ app for 42099)

- Long-travel independent suspension

- positive caster angle on the front wheels

- Long wheel for stability on the straigt lines

- Double steering rack and steering arms reduce wobbling of the steering system

- understeering feature (rear wheels get more grip)

- RC tires 90 mm

 

Buggy performed well, comparing to the 42124 set. It appears to be a car that is very comfortable to play with. The speed of the buggy allows you to walk with your normal speed in the park driving it at the same time! Here is a small video of my first tests:

 

As I said, the main goal of this project was to use C+ electrics. But after that I decided to boost it with buggy motors! The overview of the car does not change much. Rear wheels get a positive caster angle, and wheel size was reduced from 90 mm to 85 mm (for reducing speed and increasing torque).

 

Here is a short video with Buwizz-powered Dragonfly. I will definitely make another video about this car then the summer comes.

 

 

[gyenesvi]

Nice buggy, I like the way the front shock absorbers are built into the A-arms. But the caster angle seems a bit too much for me, I am not sure if that much has some mechanical disadvantages, for example, as the wheel moves up, it also moves back a lot, isn't that a problem?

What are the 85mm tires you are using? Do they fit the rim well?

[Daniel-99]

6 hours ago, gyenesvi said:

Nice buggy, I like the way the front shock absorbers are built into the A-arms. But the caster angle seems a bit too much for me, I am not sure if that much has some mechanical disadvantages, for example, as the wheel moves up, it also moves back a lot, isn't that a problem?

What are the 85mm tires you are using? Do they fit the rim well?

I agree, that the caster angle is too big, but I will keep it and make more driving tests. 

The tires I bought at Aliexpres, that is very common in Russia 

https://www.aliexpress.ru/item/1005003264692710.html?spm=a2g39.orderlist.0.0.280d4aa6UZj40A&_ga=2.250904326.1876355886.1648824271-1596240348.1648271540

But all tires with the following parameters will fit well on lego rims:

outer diameter: 85 mm 

inner diameter 1,55 inches

width: 28 mm.

[2GodBDGlory]

Nice job! I've never seen the rear suspension angled like that. Is there any advantage to that when the wheels aren't being steered?

[gyenesvi]

On 4/1/2022 at 4:48 PM, Daniel-99 said:

The tires I bought at Aliexpres, that is very common in Russia 

https://www.aliexpress.ru/item/1005003264692710.html?spm=a2g39.orderlist.0.0.280d4aa6UZj40A&_ga=2.250904326.1876355886.1648824271-1596240348.1648271540

But all tires with the following parameters will fit well on lego rims:

outer diameter: 85 mm 

inner diameter 1,55 inches

width: 28 mm.

Thanks for the link, this is what I was thinking too, just could not find it on Ali. The thing is that I haven't found one with ~85 mm outer diameter that has a thread pattern I really like; so far this is the best looking. Maybe I'll try them out.

[Daniel-99]

Here is a longer run of Dragonfly in the snow!

 

[Daniel-99]

Here is another MOD of Dragonfly. Now with Mindstorm 51515 block as a power source.

The new version has 2 C+ XL motors for propulsion which are connected directly to the rear wheels. Rear axe has a free articulation, but it does not do much, since the car is not powerful enough to go off-road. For steering a 51515 medium angular motor is used.

To be able to control this buggy I installed the Mindstorm app on my tablet. But there is no easy way to make it go without programming... I spent several hours trying to make a proportional control. It is easy to understand that I need, but it is hard to program it in the Mindstorm environment, since there is a very limited choice of commands. So I decided to use some cheats. This buggy uses the proportional control module from M.V.P. (51515 model). But M.P.V. code requires two angular motors (one for steering and another one for propulsion), so I placed another angular motor in the cockpit and add a "fake" front-back joystick to the control (purple one).

 

I am totally disappointed with the 51515 set. It is very weak. Steering motor has not enough power for calibration (with the front wheels lifted from the ground) without any load... You need to restart calibration to get some kind of "working steering system". For comparison, C+ L-motor powered by a Buwizz unit at 50% do this job easily! Further, car is very slow, again due to the weakness of 51515 unit. To see the difference, watch a video below: 

In this video both buggys are powered by Buwizz 3.0 units. The red one has 2 C+ XL motors for propulsion while the black one has 2 Buwizz motors. The difference with 51515 unit is dramatic! Finally, the mindstorm software is very unfriendly for driving the car. It takes a lot of time to connect a tablet to 51515 unit, and to calibrate the steering system. But the most annoying thing is the delay of the control!  

 

Here are few photos of my Buggy:

 

Which version of Dragonfly you like the most?