[MOC] Project Thrasher (rock crawler/bouncer)

[AndyCW]

Hey gang,

Here is my most recent creation. This was good enough to make a video of, but I have numerous improvements to make.

I hope the above codes embed the video. I'm still having troubles with this forum and embedded media. If the above does not work, how is it done?

5292 Buggy Motor x2

PF Servo motor

Efferman's Shapeways portal hubs and heavy duty U-joints

RC4WD Rockcrusher H/T 1.9 tires

Zippy 3 cell Lipo 11.1v 45c

Pololu Trex dual motor controller

Traxxas 2.4 gHz transmitter/receiver package

1.6 kg total weight

Triangulated 4 links front and rear

Caster, Kingpin, and Ackerman on front axle

8.3:1 axles run off of fast output

Ultra heavy duty driveshafts

Jeep like body

Portal hubs like Unimog

Double reduction center section like Rockwells

The 12bevel gears acting as the pinion gears started to grind after a couple of days of abuse, but it took that long for them to cause problems. I also had heat issues with the motor controller. Prolonged high load driving would cause the motor driver to shut down. I'll need to add a fan, heat sink, and/or change the enclosure.

Efferman's shapeways parts held up quite well. I was initially skeptical of the portal hubs strength, but they never let me down even if a wheel became blocked. They also kept the portal hub within the tire. This stopped them from eating leaves and grass. The rear stock lego hubs ate quite a bit of debris.

It took several iterations of driveshaft before I found one that would withstand the shock loads of full throttle obstacles. My telescoping designs all failed so I needed to redesign the geometry so that the need for the telescoping feature was minimized.

An hour of wheeling at the park only drained half of my battery.

Next step will include more motors and less gear reduction.

Questions, comments, concerns, or relevant war stories?

v/r

Andy

Edited November 5, 2014 by Jim
Embedded video

[Doc_Brown]

On your YouTube page click on "share" then copy paste the highlighted link directing here. :)

I love your heavy duty drive-shafts!

But I do think you used way too many non lego parts, and therefore its too easy to get great results.

Regardless of that you did a great job putting it all together.

Next job is to make something that will keep up with a Twin hammers or Wraith! haha

[HorcikDesigns]

Mabe the best lego crawler I have ever seen. I really like the use of that "big piece" form Racers RCs as an bumper ;)

[AndyCW]

Jim,

Thanks for fixing me up with the embedded video.

Doc,

Other than the portal hubs and associated u-joints the entire driveline is Lego. The non-lego parts are for the supporting systems. The green crawler was a SCX10. It was faster and better at crawling. Hopefully my next version will be more equivalent. The response from other people at the park was much more interest in my truck than the other one.

Gzzig,

Thanks for the compliment. Hopefully V2 will be even better.

v/r

Andy

[HorcikDesigns]

You are welcome, but have you more photos (of the axles and chassis)? ;)

[AndyCW]

Here is a link to my picture folder over at Imgur.

https://listener79.imgur.com/all/

These are all of the pictures that I currently have. Is there something else anybody else might want to see? The truck is still assembled and another picture is easy to take.

v/r

Andy

[darksheep]

If you have time may be you could make instructions, I showed this to guys at work and they all want to make one.

I might also do so ,in December .

[VKTechnic]

Mabe the best lego crawler I have ever seen.

You get what you pay for

I really wish LEGO would make a higher-spec R/C system using good LiPo batteries, proper R/C (receivers, ESC, etc.), and more powerful/faster motors. Maybe someday...

[AndyCW]

VK,

You're kinda right about the price. The motor driver was not cheap. The Traxxas components were donated by a friend with spares. The battery is actually cheap and came from my RC planes parts stash.

This one likely costs less than some of my other trucks. My other creations have had multiple Lego rechargeable batteries and multiple PF servos.

You're onto something with a proper Lego RC system. This would also require more powerfull motors to rationalize. Who really needs RC for a MOC that is as slow as a racing snail?

Darksheep,

I'm not likely to make instructions. I just don't have the time or inclination. I can take more detailed pictures when I disassemble it though and will post them here.

v/r

Andy

Edited November 5, 2014 by AndyCW

[timslegos]

I like the sound of more motors! Cant wait to see the next iteration.

tim

[Boxerlego]

WOW! First that was a great video and great music too, I'm impressed with this RC conversion the Rock Crawler performed well. Tho what gets me is the LEGO servo motor, did you have to program the motor driver or was is already functional just by connecting the servo up right of the bat.? I understand you don't want to make instructions but I'm just confused about what going on with the servo motor. You could get probably 10-20 extra watts or more just by adding a heat sink on top of the driver. The 3d printed portal hubs and heavy duty U-joints designed by Efferman's work out great even as you went down the concrete steps, that certainly tested the custom parts out, if something were to break it would have been there. Good luck with V2 looking forward for it!

You get what you pay for

I really wish LEGO would make a higher-spec R/C system using good LiPo batteries, proper R/C (receivers, ESC, etc.), and more powerful/faster motors. Maybe someday...

If there was another rendition of the RC Buggy motors and RC system. That would be awesome. Maybe a 12v system?

Edited November 6, 2014 by Boxerlego

[AndyCW]

Here is a link where instructions of a sort are presented for the RC system and servo interconnection.

http://www.eurobricks.com/forum/index.php?showtopic=88960&hl=z32drive

I used an old lego battery box as my enclosure.

v/r

Andy

[Boxerlego]

I have a question about the servo, is it working with 5v or can that be adjusted to 9v? I looked at the specs of the DMC, It describes a min and max logic voltage. Is that controlling the LEGO servo?

Minimum logic voltage: 2.7 V Maximum logic voltage: 5.5 V

[AndyCW]

The servo sees voltages from 0 to 12 in this setup. The motor driver applies a proportional voltage depending on the pulse width from the receiver. The servo gets its power directly from the battery and the proportional voltage from the driver. The two channels on the motor driver are indistinguishable from each other.

From what I know of regular servos, the Lego one isn't like them.

Perhaps the servo compares its source voltage from the outside wires to the proportional voltage on the inside wires to determine position. The servo does seem more powerful than it was on the PF architecture.

Disclaimer: I am not an electrical engineer or technician.

v/r

Andy

Edited November 6, 2014 by AndyCW

[Boxerlego]

Thanks AndyCW that is awesome! Its great to read that the servo working on good a supply of 12V. That also sounds promising. Now I'm understanding whats going on with the servo motor and the TRexDMC. Looking back at on the walk through that z3_2drive made for this the tricky part is what confused me because the servo end is connected to the motor driver side and that right there is what confused me. I understand how a motor driver works but It just didn't make any sense to me how the Lego sevo motor was able to function with out having to program it.

Now I'm understanding it out by reading this note here and I got to say Wow that is awesome. Note: The TReX does not require use of the serial interface to function; it will work right out of the box as an electronic speed control (ESC). You will not have access to the full suite of features the TReX provides if you do not make use of the serial interface, though

That sounds awesome right there that it will work right out of the box even with the LEGO servo. It makes tons of sense now that the Lego Servo would be able to work like this because that is how it works when connected up to the Lego receiver. So that is why nothing needs programming here for the servo work. It is outstanding that the PF servo is able to function with 12 volts but it might be to much voltage for PF servo to be able to handle the max 16 volts the TReXDMC is able to function with. Only if there was some technical information on the servo towards how much voltage it can handle.

Edited November 6, 2014 by Boxerlego

[AndyCW]

Higher voltage would be awesome. 4 cell lipo would really make the truck fly, but I'm drawing an artificial line in the sand at 3 cells. I don't know whether the servo could take it. I know that the motors could take it, but I'm worried about how much they will be degraded by the additional voltage. They are a lot harder to replace than the servo. I also already have a good supply of 3cell batteries in my RC plane stash.

TL;DR

12v is a far as I am currently comfortable going

How long before you jump on the TrexDMC RC Lego wagon?

v/r

Andy

[Boxerlego]

Its tempting to get one but I'm working/modding of off the PF system. Right now I'm building on another motor control circuit that works with every version of the IR receiver. My goal on this is to make it more compact and work with a range of voltages from 12 to 18.

Awhile ago I connected the 555 timer to the Lego servo to test the idea out and the PWM from the 555 time moved the servo, it wasn't perfect. I'm amazed.

Edited November 6, 2014 by Boxerlego