Fast RC crawler - 4XL motor

[Tamas Juhasz]

Hi!

I made a few crawlers until now, and I wanted to create something new, with more fun. So I decided to add a lot of power in a lightweight chassis to be the crawler fast, but also capable. My goal was to make the most simple and effective Lego rock crawler:

http://www.brickshel...ry.cgi?f=538615

I used a flexible frame as suspension, this helps to keep it lighter, there is no need for a lot of parts to create a 4 link or other suspension. As you can see below in the video, this "suspension" also works well on terrain. Has LiPo battery, and V2 IR receiver. There are two receivers, two XL motor is connected to each, there are 4 XL motors in total. After the motor's output, a 24:12 gearing (deceleration) is built in, so the wheel spins about 85 rpm, which allows to reach 1,7 km/h. The wheelbase-width ratio is similar to real RC crawlers.

I tried to add a big ground clearance, there was no problem with it. It's an advantage of this flexible chassis, there is nothing under the middle of the vehicle. The wheels are RC4WD 1,9" Rock Crusher XT's, their weight helps a lot of the stabilization of the vehicle. The XL motors are placed low, they also help to have a better center of gravity.

I added a simple body, with more crawler-like look, than in my previous crawlers.

Steering:

One M motor steers the two XL motors in the front axle. These motors are connected to mini turntables to be more stable and robust.

The steering ratio is 5:1. http://www.brickshel...16_1280x960.jpg

I used strong pins from 8842 to make stronger connections in the axles. All the motors and the main parts are connected together with these:

Weight: 1105 g.

I don't know yet the number of pieces, but it can be about 200.

A 720p video:

Most interesting parts: 01:11 ; 01:37 ; 03:16

What do you think?

Edited January 12, 2014 by Mbmc

[Zerobricks]

Simple and fast! Its great!

[KirTech LAB]

Very original and light construction!!!

Does one LiPo batery power four XL-motors without any problems?

[cgg199]

Another TT with no Lego Shock Absorbers. Is this the Future of Trial Trucks?

Great design and very good performance!

[Gee]

This has all the right ingredients: light weight, power and simplicity. Very very capable and a nice antidote to all the suspended crawlers that you see. Keep it up man!

[Tamas Juhasz]

Thanks guys.

Shock absorbers:

It depends on the builder, if you like them, you will use them. The truth is, in 99% of 4x4 off roader constructions, shock absorbers are unnecessary. A linked suspension is always more stable and gives more optimal weight distribution, better center of gravity in terrain. Lego vehicles in this speed (under few km/h) don't need shocks. We use them in suspensions to make the axles/wheels back to the original position, once they are moved by terrain. But there are so many different constructions, sometimes it' much better to use springs (Lego shocks are only springs, except for the one in 8466 door mechanism), e.g. for crawlers, realistic models, Tatra. I don't think non spring suspensions will be more popular in the future.

Very original and light construction!!!

Does one LiPo batery power four XL-motors without any problems?

Yes, in this weight one LiPo is enough. The terrain in the video was pretty hard, but had enough power to go through. Falling back or rolling down is the real problem (as in every crawler). With two it would be more powerful, but more heavy, and I have only one LiPo. It would be difficult to place a second LiPo under the small body.

Edited January 12, 2014 by Mbmc

[Boxerlego]

Amazing! That is a clever design.

[SNIPE]

I would slow it down a bit because when it is going over stuff it was too fast, and real off roaders tend to crawl a long not whizz over large obstacles

Other than that nice job, I like how the tires dont have anything in the way of them (chassis is above the wheels) so it can drive over tall things.

Shame theres no larger wheels.

Edited January 13, 2014 by SNIPE

[Tamas Juhasz]

I'm afraid I don't fully understand your first sentence.

Edited January 13, 2014 by Mbmc

[Lakop]

That's a great crawler. Watching the video I began to think " will it go up stairs", then it did! I wonder if you could build a shorter wheelbase version as I noticed the chassis hit the stairs as it climbed down. A minor negative but I would build one if I had four XL motors, a clever design.

H

[Tamas Juhasz]

Thx Horace T.

I would slow it down a bit because when it is going over stuff it was too fast, and real off roaders tend to crawl a long not whizz over large obstacles

You are absolutely right. That's why I connected all motors to channel one and to the same colored output. So I can control it with the speed remote controller (except in 1-3 level, those have little torque with this gearing). You can see an example in the video from 0:21 to 0:25 - typical case, when low rpm is needed to win against tricky terrain.

Edited January 13, 2014 by Mbmc

[ddimkin]

That's the smartest design I've ever seen - the idea with no suspension is phenomenal!!! Huge congrats!!! I own the 9398 set but I am not satisfied at all - tunned it a lot but still nothing :) It comes with 2 x L-motors and a servo motor. Today I will order two more L-motors and a second receiver and start building something like your crawler in LDD (haven't used LDD before). I use these on my 9398 to increase power and get constant voltage for the motors:

http://www.ebay.co.uk/itm/NEW-6400mAh-8-4V-Battery-Pack-Pouch-For-CREE-XM-L-T6-LED-Bike-Head-Lamp-Light-/111308082933?pt=UK_ConsumerElectronics_Batteries_SM&hash=item19ea7a8ef5

http://www.ebay.co.uk/itm/350963713406?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649

Wish me luck :) can't wait to start!!!

[Ape Fight]

Weird looks, awesome off-road abilities. Looks a riot to drive : )

[rollermonkey]

@200 parts?

Maybe you can enter this in the [MINI] contest!

[Boulderer]

Wow! You weren't kidding about the lightweight chassis. As said by others ... weird looks but, looks like great fun. And, at 200 odd parts, really quick to put together. I wonder if an L motor version would work?

[ddimkin]

4 x L motors should be no problem especially if you increase the voltage and keep it constant (see link in my post above). You can check this:

http://philohome.com...p.htm#Synthesis

@MBMC, could you share LDD file? :)

Edited July 25, 2014 by ddimkin

[Boulderer]

4 x L motors should be no problem especially if you increase the voltage and keep it constant (see link in my post above). You can check this:

http://philohome.com...p.htm#Synthesis

@MBMC, could you share LDD file? :)

Great link, thanks

[grum64]

Great performance but man, it's an ugly little critter!

Edited July 25, 2014 by grum64

[ddimkin]

Check this out:

http://www.eurobricks.com/forum/index.php?showtopic=97878&hl=crawler