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MOD of Madoka's Buggy 2
This minor MOD of Madoka Arai's fast, agile Buggy 2 MOC relocates the IR receiver, addresses some steering and rear suspension issues, and tweaks the styling a bit.
About this creation
Please feel free to look over the images and skip the verbiage.

While I'm posting minor MODs of spectacular MOCs by renowned Japanese builder Madoka Arai (aka Madoca1977 on YouTube and Rebrickable), I might as well share this MOD of his fast, agile PF Buggy 2.

The current MOD, with the IR receiver relocated to maximize its field of view...



The video and most of the photos below show the previous version, which differs only in having its IR receiver in the original location in back.









Madoka's own video and beautifully photographed online instructions show the starting point in great detail.

To keep straight who did what, "MOC" and "Buggy 2" will refer to Madoka's original design, and "MOD", to my modification of it. And since I really didn't change much, all comments will apply to both unless otherwise noted. All embedded images are of the MOD.



Buggy 2 caught my eye while poring over Madoka's YouTube channel. All of his designs are worthy of careful study, but this one offers dazzling performance and lots of neat tricks in a fairly simple build. It's also relatively inexpensive as Madoka's MOCs go.



This MOD of Madoka's Tatra 813 is also chock full of valuable lessons from the master, but it's a much bigger bite to chew, both mechanically and structurally, and a small fortune to build.

On this page<< Back to top




Review of Madoka's MOC

If you're looking for a fast, nimble remote control buggy to build from instructions, you'll have a hard time beating the performance and looks of Madoka's PF Buggy 2.

It's very quick on flat ground and scampers over terrain of moderate relief and steepness at respectable speeds. Ground clearance is ample. Maneuverability is good, but a vehicle this fast really needs quicker steering responses. Climbing ability is traction- rather than power-limited. Battery life is excellent with the PF rechargeable.



The MOC takes a surprising amount of punishment for its weight but doesn't handle hard front-end collisions well, as discussed below. Most frustratingly, it's also subject to all the flaws of the PF remote control system. A Bluetooth-based sbrick receiver would really shine here.



The mechanicals are fairly straightforward:Steering alignment is too fragile (see below), but the front suspension is otherwise quite robust.



The soft springs on the black 9.5L shocks (2909c03) used on all 4 wheels are perfect for buggy's mass and dynamic wheel loads.



The DGB A-arms (wishbones) and yellow wheel spindles up front are expensive. (I added the black front bumper and white skid plates.)

The L (propulsion) motor casings seem to be up their task of keeping the rear live axle intact and aligned.



As seen many times in the video, the IR receiver is easily shadowed in its original location in back.

The unique rear suspension is hard to categorize but resembles a pair of MacPherson struts linked above by a strut bar doubling as a roll cage member and below by black 9L radius rods (near the center of the next photo) connecting the live axle to the lower chassis via towball pins.



The stiff LBG hubs connecting the black wheels to their motor shafts reinforce the drive axles against (i) motor torque and (ii) bending and torsion due to wheel loads.



There are 3 motors: An L driving each rear wheel directly, and a PF stepper up front for steering. All share the same V2 IR receiver and lightweight PF Li polymer battery.



Since both L motors are powered by the same IR receiver port, one of them has to be fed through a PF pole reverser to get both working toward the same direction of travel.

NB: If you're after a rock crawler capable of tackling severe terrain at much lower speeds, you'd be better off with something like the STEEL CRAWLER by Nerds forprez or the Technic - Monster Crawler - SBrick by White Shapes instead.

The heavy 3rd party tires used by these crawlers would probably improve traction, but they would definitely hurt top speed and might detract from overall climbing performance as well.

It's not a snow buggy, either.






Modifications

The current MOD, with the IR receiver poking up through the roll cage to maximize its field of view.



The previous version, with the IR receiver in its original location.





Compared to Madoka's contribution, my mods were fairly minor:
  • Added a much-needed front bumper and strengthened some key weak points in the steering system and rear suspension
  • Strengthened the chassis and roll cage here and there
  • Added a front skid plate and redesigned the rear wing
  • Tidied up the black and white color scheme
  • Eliminated the driver's seat to offset weight gains elsewhere
  • Relocated the IR receiver to the top of the roll cage to expand its field of view
These changes increased play value significantly, especially the last one.



In part, the MOD represents an attempt to address the MOC's 2 greatest mechanical weaknesses. Both relate to front-end collisions, which are all too frequent with the so-called PF remote control system.



The lack of fenders means that front-end collisions are likely to impact at least one wheel. Uneven wheel impacts can shift the steering rack relative to the pinion attached to the steering stepper motor. This leaves the front wheels turned to the right or left when the stepper returns to center.

Realigning the steering is a chore. The front bumper I added helps a lot in head-on collisions but not in the more common impacts from both front and side. Hardening the entire steering mechanism helped with the latter, but steering alignment fragility remains the MOD's least endearing feature.

Front-end end impacts also cause the towball ball pins connecting the lower rear radius rods to the live axle to pop out of their L motor pin holes.



One of the offending towball pins is seen here just in front of the bare rear axle. Wrapping the pin ends of these towball pins with cellophane tape before inserting them helps.

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PF remote control

This buggy is yet another example of a highly capable PF vehicle hobbled by PF infra-red remote control (IRRC) -- especially outdoors, where a buggy belongs.



The wrong turns in the video were just my bad driving, but the incessant starts, stops, and overshoots and the uncomfortably long off-screen excursions were all due to fundamental IRRC flaws. Relocating the IR receiver afterward helped, but not nearly enough.1



The 3 handsets below embody some of the trade-offs involved in making the best of IRRC in the buggy's case.



The ergonomic 3-state (bang-bang) joystick below allows one-handed operation. Bang-bang speed control works fairly well in the buggy, but it's just too fast for bang-bang steering at speed.



The next 3-state option capitalizes on a control layout familiar from real cars. This one takes 2 hands.



The more cumbersome handset at the top of the next photo combines a speed control (left) with a simple 3-state controller (right). The former allows the small steering inputs needed in vehicles this fast, but only at the expense of responsiveness and ergonomics.



<< Back to top




MOD specifications

Vehicle type:Off-road buggy
Construction:Studless
Overall dimensions:320x222x148 mm (LxWxH)
Scale:~1:12 in length
Mass:685 g
Platform:4x2x2
Front suspension:Independent double wishbone
Rear suspension:Macpherson strut-like
Drivetrain:Direct drive to rear wheels
Final drive ratio:1:1
Motors:2 Ls for propulsion, 1 stepper for steering
Electrical power supply:7.4V Li polymer PF rechargeable battery
IR receiver:V2
Modified LEGOŽ parts:None
Non-LEGOŽ parts:Tape on outboard radius rod towball pins
Credits:Minor MOD of an original MOC by Madoka Arai

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Footnotes

1 "Remote control" hardly applies to the PF system. Miserable range (typically 5 m at best) calls the "remote" part into question, and frequent connection failures due to beam blockage, IR interference, and who knows what else make the "control" part laughable. The fact that the motors stay on for some time after a connection loss (~1 sec with a 3-state controller and indefinitely with a speed control) only compounds the problem. The Bluetooth-based sbrick receiver eliminates all these problems but has issues of its own.




Comments

 I made it 
  December 15, 2015
Quoting matt rowntRee Reminds me of the Tamiya Frog I had as a kid! Except this one looks less likely to break and cost a fortune to repair. Unless the "S"brick breaks. ;) Awesome work, perfect for chasing cats. XD Zippy!
Thanks, Matt! Being my 2nd fastest LEGO RC vehicle (after the latest motorized prop cart at http://www.mocpages.com/moc.php/403294), this buggy does have some cat-chasing potential, but in our house, the dog is the only one that runs. The unflappable cat either ignores moving LEGO altogether, comes up to get a closer look, or just steps out of the way like a bullfighter. It's possible to run over its tail without getting a reaction. Then there's Kramer, our big, ferocious-looking Belgian sheepdog. He bolts for another room the second anything LEGO shows up. If he happens to be on a hardwood floor at the time, there will be a great deal of paw-spinning, just like in the cartoons.
 I like it 
  December 15, 2015
Reminds me of the Tamiya Frog I had as a kid! Except this one looks less likely to break and cost a fortune to repair. Unless the "S"brick breaks. ;) Awesome work, perfect for chasing cats. XD Zippy!
 I made it 
  December 5, 2015
Quoting jds 7777 The problem I have with the sbrick is it's $60 price tag. And I don't like the idea of not having any tactile feedback from the controls. But still, probably the best platform available for now. I may try to rig something up sometime. I've already built custom Lego batteries (totally worth it) and multiple custom motors (not worth it); so maybe I'll give it a shot.
Yeah, that's the cost of 4 V1 receivers or 2-3 V2s, but I've vowed not to buy any more of either. Looking forward to seeing what you come up with.
  December 5, 2015
The problem I have with the sbrick is it's $60 price tag. And I don't like the idea of not having any tactile feedback from the controls. But still, probably the best platform available for now. I may try to rig something up sometime. I've already built custom Lego batteries (totally worth it) and multiple custom motors (not worth it); so maybe I'll give it a shot.
 I made it 
  December 5, 2015
Quoting Nick Barrett The PF IR system can be frustrating... this makes good use of it, although I thought the rear suspension set-up would be fragile when I saw it. Nice, and useful, mods.
Thanks, Nick! I had the same reservations about the rear suspension, but it holds up surprisingly well when the radius rod towball pins don't pop out.
 I like it 
  December 5, 2015
The PF IR system can be frustrating... this makes good use of it, although I thought the rear suspension set-up would be fragile when I saw it. Nice, and useful, mods.
 I made it 
  December 4, 2015
Quoting jds 7777 Nice job! The drivetrain reminds me of the one used in Saiel's Baja truck. I found the last remote interesting. I tried using the speed controller for land-based vehicles. But found the ridiculously long lag, lack of any sensitivity whatsoever, and lack of actual stopping points for the dials so infuriating that it was nearly sent through the nearest window (to put it delicately). After it smashed 4-5 MOCs, I gave up. I'd like to see someone rig an RC aircraft remote control for Lego - then publish instructions so the rest of us mortals can use it to.
Thanks, JDS! Like you, I have no polite words for the speed control, and for all the same reasons. But alas, it's a necessary evil at times. For example, steering a vehicle as fast as this buggy with a 3-state controller, as I did in the video, is a recipe for missed turns and crashes, and it showed. A real RF controller like the one you're wishing for is my 3rd wildest dream. (Sorry, can't talk about the 2 wilder ones here.) Saw such a DIY controller on the web a while back, but implementing it was way over my head electronically. For now, the sbrick is probably our best bet. Bluetooth signaling isn't ideal, either, but it's way better than IR, and the ability to whip up your own MOC-specific phone interfaces is huge.
 I like it 
  December 4, 2015
Nice job! The drivetrain reminds me of the one used in Saiel's Baja truck. I found the last remote interesting. I tried using the speed controller for land-based vehicles. But found the ridiculously long lag, lack of any sensitivity whatsoever, and lack of actual stopping points for the dials so infuriating that it was nearly sent through the nearest window (to put it delicately). After it smashed 4-5 MOCs, I gave up. I'd like to see someone rig an RC aircraft remote control for Lego - then publish instructions so the rest of us mortals can use it to.
 I made it 
  December 4, 2015
Quoting Oliver Becker This buggiest buggy comes great, Jeremy! Nice boots, by the way... "These boots are made for walkin'" could be a alternate background music? LOL ;) Love your humor, your replay to Gabor made a big smile on my face! :)
Many thanks, Oliver! If PF remote control were worth a darn, you wouldn't have had the pleasure of seeing my favorite winter shoes. (I'm really frustrated with PF RC right now.) Gabor and I like to give each other a hard time.
 I like it 
  December 4, 2015
This buggiest buggy comes great, Jeremy! Nice boots, by the way... "These boots are made for walkin'" could be a alternate background music? LOL ;) Love your humor, your replay to Gabor made a big smile on my face! :)
 I made it 
  December 4, 2015
Quoting Gabor Pauler You broke the world record of creating the most heavy duty remote controller. Almost bigger than the car.
That's how I got all these big arm muscles, Gabor! It's also what happens when you get desperate enough for remote control that deserves the "control" part. It's actually pretty useful with boats.
 I like it 
  December 4, 2015
You broke the world record of creating the most heavy duty remote controller. Almost bigger than the car.
 I made it 
  December 4, 2015
Quoting Didier B I'm so disappointed it does not fly ! Great job Jeremy... In addition to the technical part the shape is also excellent. I really like it ! Didier
Thanks, Didier! Can't wait till my sbricks arrive to unleash its full potential. My exasperation with PF remote control grows with each new MOC.
 I like it 
  December 4, 2015
I'm so disappointed it does not fly ! Great job Jeremy... In addition to the technical part the shape is also excellent. I really like it ! Didier
 
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