[MOC] The fastest Lego Technic lipo racer | At the very limit

[896gerard]

I have long awaited the moment that two race buggy motors would be in my reach, as they are quite expensive now... and I also bought the Lego Technic lipo battery two years ago. The perfect recipe for a small lightweight racer! Read the rest of the story at: http://www.moc-pages.../moc.php/424516.

For now, there's just these two pictures and two videos. To post the photos on Eurobricks, I had to serieusly resize them. If you want to see the better quality images, just click this link: http://www.brickshel...ry.cgi?f=561899. All photos can also be found on the MocPage link, and can also be hosted from MocPages. This is because brickshelf has sometimes a rather long posting time.

Please do not use THESE EXACT photos on another website, they are really at 10% of their real quality because Eurobricks requests it. The brickshelf photos are really better!

[THERIZE]

That thing is awesome!! It must be a incredible lot of fun to drive something like that.

[spongebrickpl]

Great toy to play with:) I would like to have something like this. This car is a great drifting vehicle. You packed it very well:)

[zux]

Great skills stuffing so much in this size and the shape looks great!

Also I'm a bit sceptical about all of these fastest MOCs. Any MOC based on chassis of 8369 would outrun being considerably larger.

[LEGO Train 12 Volts]

Fantastic car, fantastic video ...amazing drifting! :wub:

[896gerard]

Great skills stuffing so much in this size and the shape looks great!

Also I'm a bit sceptical about all of these fastest MOCs. Any MOC based on chassis of 8369 would outrun being considerably larger.

And that's why I'm saying consistently everywhere that it's the fastest lipo racer, so a racer with the lithium battery on board. If you see it that way, it really is the fastest. And everyone may correct me because I don't waste all my evenings watching YouTube videos, I rather spend my evenings building cars like this.

And as for the speed: Off course, the RC unit can pump more juice that the lipo battery box. But it is thousand times less fun if you build it that way because the lightness is gone. It certainly wouldn't fly over the ramp anymore.

[2LegoOrNot2Lego...]

Really amazing build, so small, so light and therefore so fast!!!

[brunojj1]

Thanks for sharing this crazy wiesel! Especially the trick with the slow current increase is great, I also have such troubles sometimes and will consider this solution in future. You must have had a lot of fun and did get the speed and efficiency to the max and it´s a considerable achievement!

[896gerard]

Thanks for sharing this crazy wiesel! Especially the trick with the slow current increase is great, I also have such troubles sometimes and will consider this solution in future. You must have had a lot of fun and did get the speed and efficiency to the max and it´s a considerable achievement!

Many people are telling me about this 'current startup' problem with using two RC buggy motors on one lipo battery box. Therefore I've started looking around a bit now and found that even less people have done it this way then I thought....

... they just bought another expensive lipo battery box and used one lipo box for one RC buggy motor. But as an electrical engineering student, I'm always looking for the boundaries of any given system. The idea of using this bypass is just something I found out after building the Luctor because the gearbox broke everytime I used the bang bang controller, the immense torque of two XL motors was enough to pop out some gears at high loads... So the XL motors also were controlled with the speed remote to have this slow-current starting system. To conclude, the racecar startup system was invented on a slow truck!

Some links for evidence: http://www.moc-pages.com/moc.php/414168 and for the controller: http://www.moc-pages.com/image_zoom.php?mocid=414168&id=/user_images/52513/14340583375

[Epic Technic]

Really nice little car, seems like a ton of fun to drive around. However, I do not see how you managed to reach a top speed of 14 km/h, I did the math and at 7.2 volts with that gear ratio the car can only theoretically go at 11.4 km/h without friction on a flat surface.

[896gerard]

Really nice little car, seems like a ton of fun to drive around. However, I do not see how you managed to reach a top speed of 14 km/h, I did the math and at 7.2 volts with that gear ratio the car can only theoretically go at 11.4 km/h without friction on a flat surface.

Good question. I always like these questions. However, I have measured this speed with my calibrated bicycle computer. Calibrating means measuring the circumference of the front tire manually in mm and inserting it in the the bicycle computer. This method is not in the bicycle computer's manual.

Having said that, I clocked many (at least 5) 12 km/h runs. When the straight road was a little longer, I clocked speeds of 13.8 km/h. There were at least 2 runs with 13.8 km/h on them. I do not understand it either, but I just put in the video what I measured.

[zux]

And everyone may correct me because I don't waste all my evenings watching YouTube videos, I rather spend my evenings building cars like this.

Don't get me wrong, I really like your model, you managed to include all of these components in a great format with cool looking shape. And the model, I imagine, is very fun to drive.

And as for the speed: Off course, the RC unit can pump more juice that the lipo battery box. But it is thousand times less fun if you build it that way because the lightness is gone. It certainly wouldn't fly over the ramp anymore.

You probably not aware which set type I was referring to. While being ~2.5Kg heavy it still can run up to 20km/h. There's no issues with drifting, making donuts on smooth or dirty surface and jumping over the ramp. It can even do sort of a wheelie if driven on a surface like carpet (with good friction/contact).

And that's why I'm saying consistently everywhere that it's the fastest lipo racer, so a racer with the lithium battery on board. If you see it that way, it really is the fastest.

So what do I need to break the "Fastest lipo racer" title - simply buy a LiPo battery and use it with model above? The title just doesn't make sense.

[896gerard]

So what do I need to break the "Fastest lipo racer" title - simply buy a LiPo battery and use it with model above? The title just doesn't make sense.

No, you can get the title only if make your own model a little faster. It is seen from an engineering perspective, when you start using the Lego electronics at their limit. Building at the limit is what I have done, I hope everyone including you understands that.

And with the Lego RC Unit, all you have to do is connect the few big components such as motors, steering and the shape of the model is pretty much defined. Also you need to do very little about the drivetrain and current startup, as the RC unit does that already. In this model, those things are not automatically granted, so you need to design them yourself, which delivers much more satisfaction when it's working all correctly.

Edited January 30, 2016 by 896gerard

[Epic Technic]

Good question. I always like these questions. However, I have measured this speed with my calibrated bicycle computer. Calibrating means measuring the circumference of the front tire manually in mm and inserting it in the the bicycle computer. This method is not in the bicycle computer's manual.

Having said that, I clocked many (at least 5) 12 km/h runs. When the straight road was a little longer, I clocked speeds of 13.8 km/h. There were at least 2 runs with 13.8 km/h on them. I do not understand it either, but I just put in the video what I measured.

Interesting, maybe the road was a bit sloped. Anyways, I still think that it holds the fastest lego lipo car title. ;)

[896gerard]

Interesting, maybe the road was a bit sloped. Anyways, I still think that it holds the fastest lego lipo car title. ;)

The speed runs were done on the same asphalt that you saw in the video, so if it has a slope then the slope is quite invisible... And it was not my idea of giving it a title, but you always have to think of a YouTube video title and this was the right one, according to me... But I really like that you did a calculation, doing that occasionally keeps me and all the others sharp!

[zux]

No, you can get the title only if make your own model a little faster. It is seen from an engineering perspective, when you start using the Lego electronics at their limit. Building at the limit is what I have done, I hope everyone including you understands that.

And with the Lego RC Unit, all you have to do is connect the few big components such as motors, steering and the shape of the model is pretty much defined. Also you need to do very little about the drivetrain and current startup, as the RC unit does that already. In this model, those things are not automatically granted, so you need to design them yourself, which delivers much more satisfaction when it's working all correctly.

Well, there are faster models, but they didn't use the LiPo batteries - official set like 8675 mentioned earlier. If you don't see this as a competitor while being actually faster, then you can check Sariel's models. He made a 15+km/h model (which is a piece of engineering like you like more). Both would be faster no matter if LiPo batteries were used or not, it is an easy switch.

[Blakbird]

Really nice little car, seems like a ton of fun to drive around. However, I do not see how you managed to reach a top speed of 14 km/h, I did the math and at 7.2 volts with that gear ratio the car can only theoretically go at 11.4 km/h without friction on a flat surface.

7.2V is only the nominal voltage using an assumed 3.6V per cell. Then actual voltage on a fresh charge is considerably higher. Most chargers target 4.2V per cell so you should start with 8.4V.

[896gerard]

Well, there are faster models, but they didn't use the LiPo batteries - official set like 8675 mentioned earlier. If you don't see this as a competitor while being actually faster, then you can check Sariel's models. He made a 15+km/h model (which is a piece of engineering like you like more). Both would be faster no matter if LiPo batteries were used or not, it is an easy switch.

Well, if I've got it right, Sariel does not have the lipo RC unit, but 2x unit that is powered with 6 AA batteries. He says on his website that the top speed runs were done with fresh batteries. With the Peugeot, he clocked 15.6 km/h, off course with those fresh batteries. So that's not quite 'lipo'. And if you mean rechargeable batteries, those are not lipo buth NiMh and have a lower voltage than throw-away batteries (1.2 instead of 1.5), giving any model less power.

And indeed the RC unit in the 8675 set uses a lipo, but this set (and the 3 other sets in which it occurs) contains so few real Technic pieces... my title says: Lego Technic lipo racer.

Further, I'm very surprised about the fact that my little car with 2 race buggy motors on one standard Lipo battery box (so with half the motors and less than half the power because of the BB current limit) went 14 km/h while the mighty Peugeot with all its power did 15.6kph... (Off course, the 2 km/h difference is still a huge gap at those speeds!)