P McCatty

[MOC] 8868 Claw Rig Rebirth (RC) - Now with Trailers!

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Aptly named "The Godfather" by Blakbird, I had a go at this one a few months ago. LOTS of BL orders, testing, prototype failures, clicking gears, back & forth, partial builds, disappointing tear downs, broken parts, more testing, and now here we are. Initially the idea was to remain on scale, but the end result turned out more like a big brother. The thing is an absolute unit at 3 kg & contains almost 5 meters of pneumatic tubing. Let me know what you think! If there are any questions I'll be happy to answer.  

Features:

01. RC Drive (6 x 4). PF XL Motor geared at 1 : 0.397
02. RC Steering. PF Servo Motor.
03. RC Turntable. PF M Motor with Worm Gear.
04. RC Compressor. PF L Motor driving 2 x 6L Pumps. Dual Air Tanks.
05. RC Pneumatics. PF Servo & Pneumatic Switch assembly.
06. PRV Function to automatically shut off Compressor.
07. Powered by 2 x Buwizz 2.0
08. Live Axle Suspension Front & (Tandem) Rear.
09. Working Cab Steering Wheel.
10. Opening Cab & Crane Doors. Technic Figure compatibility.
11. Disengage drive & steering motors for manual mode. Working HOG.

Instructions HERE

Credit to @Philo for the original digital file on LDraw & @functionalTechnic for the Pneumatic Servo idea.

 

Things I would or may change going forward:

01. PU + Buwizz 3.0 once the R2C kinks are worked out.
02. (In progress) 6 x 6 drive. The sweep on those portal hubs tho ...
03. Make an excavator on the back & use the 4th pneumatic function for outriggers.

 

 

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Comparison with Original 8868

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Physical Build

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Internal Renders (Functions)

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Edited by P McCatty

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Beautifully done Phillip.  It is good to see this classic re-crafted using modern Technic parts and motors.  

I have an original set and it's one of my favourites (after the Shuttle!).

+ the outdoor scenes of your build in your video are superb!

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Wow, this is so cool! I have dreamed of doing something similar, but I guess I won't have to, not anymore. You've done everything I had dreamed of and more.

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Wow :pir-love:
I love the use of the shock absorber in addition to the pneumatic.
This has so much function packed in.
If I count right there is 5 servo motors in it ? *huh*
And the switch to manual is just top notch.

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11 hours ago, P McCatty said:

... LOTS of BL orders ... almost 5 meters of pneumatic tubing.

 

So that's where all the local pneumatic supplies had gone? :laugh:

Really amazing work! This is so incredible and quite ingenious. I am a big fan of pneumatics and feature-packed technic MOCs. This has to be the best one yet!

Is there any chance you could share more details about how the front axle is suspended, and how you perhaps plan on adding drive to it? I noticed you mentioned the poor steering geometry created by the portal hubs - have you considered using the planetary hubs instead? That's what I intend to use for the next rebuild of my own truck, which I have yet to share on here.

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12 hours ago, lenzie said:

Beautifully done Phillip.  It is good to see this classic re-crafted using modern Technic parts and motors.  

I have an original set and it's one of my favourites (after the Shuttle!).

+ the outdoor scenes of your build in your video are superb!

10 hours ago, howitzer said:

Wow, this is so cool! I have dreamed of doing something similar, but I guess I won't have to, not anymore. You've done everything I had dreamed of and more.

9 hours ago, GerritvdG said:

Nice! 

I also like the possibility to switch to manual driving and HOG-steering. 

 

Thank you :classic: This was one of those that "got away" for me so I threw everything & the kitchen sink at the recreation. It was more challenging than I thought to find quiet secluded spaces to film, especially in the summer when kids are off school. During one session, a little one came over when I was unpacking. She turned around & screamed "IT'S MADE OF LEGO", then another 6 or so came running. I didn't get much done in the way of filming (GoPro & Gimbal on a stick with a controller in the other hand while trying to answer questions & avoiding all the little feet in my shots), but it was very rewarding to share it & get their feedback "OMG it's so sloooow" :laugh_hard:. Fellow maniacs in the making. 

I actually almost gave up on the manual mode. Gearing down the steering & routing it in the frame was a tedious, iterative process & brought out some colorful words on many occasions. In the end it turned out to be useful because it can roll freely & would be an ideal candidate for a big towing job.

 

4 hours ago, Touc4nx said:

Wow :pir-love:
I love the use of the shock absorber in addition to the pneumatic.
This has so much function packed in.
If I count right there is 5 servo motors in it ? *huh*
And the switch to manual is just top notch.

4 hours ago, M4rk said:

So that's where all the local pneumatic supplies had gone? :laugh:

Really amazing work! This is so incredible and quite ingenious. I am a big fan of pneumatics and feature-packed technic MOCs. This has to be the best one yet!

Is there any chance you could share more details about how the front axle is suspended, and how you perhaps plan on adding drive to it? I noticed you mentioned the poor steering geometry created by the portal hubs - have you considered using the planetary hubs instead? That's what I intend to use for the next rebuild of my own truck, which I have yet to share on here.

4 hours ago, suffocation said:

Superbly crafted. I love the manual drive & steering option; the pneumatic servo switch is ingenious!

 

It's too bad the Servos are so expensive these days. From what I've seen, as of now alternates aren't very good at achieving the 15 positions either. The shocks were definitely necessary due to the "boom crashing down" phenomenon. There is a tiny bit (almost imperceptible) of slack at the upper ranges but I eventually got the linkage to dampen virtually all of the crane arm movement. They also keep the arm elevated (maybe halfway) after the inevitable pressure drop if not in use for a while. In any case, that's what the bar at the rear bumper is for :grin:

The front suspension is a basic 4 bar parallelogram made with 6L links. I used a 9L link as a panhard rod for lateral positioning. It might be visible in one of the pictures - I also protected the ball & socket connections from popping out by integrating them into the frame & using additional bracing. I'm making a prototype for the drive at the moment. It might not happen right away due to other priorities. I'm using the C-Shape Pivot Frame (92910). Less links to work with & I might be able to get more suspension travel. So far I've also got a positive caster built in. I tried to get kingpin inclination on the portal hubs to offset the massive sweep but there just isn't enough room for this scale, & I eventually moved on to the planetary hubs like you said (great minds & all that :wink:). Hoping those newer CV Joints can handle the torque.

I can't take credit for the Pneumatic Servo. I first saw it  HERE by FT Creations. Working out the trig, the relationship is (surprisingly) pretty linear. The trouble I had was that the axle kept falling out. I first redesigned the guide to work with a frictionless pin, then added a 4L axle with stop to secure the connecting 2L liftarm. This was very reliable & I feel it might have worked out if the motors were upright instead of sideways, but one of them disengaged during testing (1 in 1000 type thing) & I went back to the drawing board. The 5L liftarms now eliminate that possibility altogether. I also considered geared options as shown by Sariel. The 8-24 pairing can't be stacked since the 24T gears would mesh. The 12-20 pairing slightly exceeds the range of the switch & is harder to achieve fine control. 

 

 

Edited by P McCatty

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Very nice work! I love RC pneumatics and generally all function-packed models, and this succeeds at both. I appreciate the attention to realistic suspension and steering, and appreciate that clever servo-valve mechanism being introduced to me.

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As a Claw Rig lover, I can only bow before the work done on this MOC. Great fidelity to the original, excellent integration, tons of playability, and very efficient pneumatics management: this is truly amazing and you can be proud!

Do you have an idea of how many hours you spent on this project, and within what timeframe?

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On 8/23/2021 at 4:35 PM, 2GodBDGlory said:

Very nice work! I love RC pneumatics and generally all function-packed models, and this succeeds at both. I appreciate the attention to realistic suspension and steering, and appreciate that clever servo-valve mechanism being introduced to me.

On 8/23/2021 at 5:36 PM, Celeri said:

As a Claw Rig lover, I can only bow before the work done on this MOC. Great fidelity to the original, excellent integration, tons of playability, and very efficient pneumatics management: this is truly amazing and you can be proud!

Do you have an idea of how many hours you spent on this project, and within what timeframe?

Thank you! To be honest I have no idea how much time I've spent on it. I just know it was a LOT. I've only recently come out of the dark ages, picking up a few medium sized models here & there to see what this studless thing is all about (yes it's been THAT long). I actually started tossing around some ideas & basic prototypes over the winter. Then I switched gears to work on a few smaller MOCs before getting back on track in the spring. In the end, the build was really the fun part. I tested & retested everything, built up sub-sections & prototypes, tore it all down to access that one part that needed to be changed, etc. This process is actually very useful because naturally the sub-models sort themselves out, & the "method of assembly" comes to the forefront. To put everything together as a "project" took a TON of work. I had to learn LDCad for the flex parts. And as you can see, there are a lot of them. To that end, Philo is an incredible resource. Once I sequenced the steps & sub-models, I put together the display build seen above from scratch. After that it's final testing & tweaks while filming/playing with it. Once satisfied, I started annotating the instructions. This is quite tedious & not as much fun, but had to get done. Stud.io has it's quirks so I had to be inventive, finding various work-arounds. Finally, for the obligatory video the filming & editing took a fair bit of time as well. Totally worth it :grin:

 

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I can´t believe what I am seeing.

Not only the pneumatics are awesome, but all the gearing seems to be great!

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great modification of my valve and anyway superb model you created. It is exactly what I like: many RC functions, well working functions and pneumatics. How did you model the pneumatics digitally? With LDcad?

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On 9/20/2021 at 2:44 PM, functionalTechnic said:

great modification of my valve and anyway superb model you created. It is exactly what I like: many RC functions, well working functions and pneumatics. How did you model the pneumatics digitally? With LDcad?

Thanks! The RC valve is very clever & well done. Yes I used LDCad for all the flexible components. There was a bit of a learning curve but in the end it is fairly intuitive. Modeling all of the hoses & wires turned out to be both tedious & fun at the same time (if that's even possible) :laugh:

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On 9/22/2021 at 6:05 PM, P McCatty said:

Thanks! The RC valve is very clever & well done. Yes I used LDCad for all the flexible components. There was a bit of a learning curve but in the end it is fairly intuitive. Modeling all of the hoses & wires turned out to be both tedious & fun at the same time (if that's even possible) :laugh:

yes, LDcad is not so intuitive but it is also how I model flexible parts. The rest I do in Stud.io. Do you make everything in LDcad?

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On 9/29/2021 at 5:09 PM, functionalTechnic said:

yes, LDcad is not so intuitive but it is also how I model flexible parts. The rest I do in Stud.io. Do you make everything in LDcad?

Likewise - I use mainly Stud.io, then export & hop over to LDCad for the flex parts before re-importing. I really love the old school look & feel of the UI. Stud.io does have some functionality with flex parts, specifically the rigid hoses. I played around with this when I did the RC MOD for 8437 Future Car. It's really touchy & I much prefer LDCad. Going slightly off topic I wish Stud.io would fix the size guide text in the instruction maker. You wouldn't believe how tedious it is to use images (of text) as a work-around.

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Posted (edited)

While ripping around with this Truck, the first thing that became apparent was that I had nowhere to put the objects I was picking up, since the Crane occupies the entire rear section. That's really where this Trailer idea came from. The most straightforward execution came in the form of a 3-Axle Turntable Drawbar set-up, using the built-in trailer hitch. I also went back to basics by keeping everything manual & making the design as simple as possible.

 

The first thing I tackled was the suspension. One possibility was implementing live axles with shock absorbers. And with no gearing it would be less complex than a driven vehicle, but I figured there still had to be an easier way. I followed @Jennifer Clark's builds some years ago & I vaguely remembered a concept on pendular suspension. I quickly found it by revisiting the discussion of her All Terrain Crane.

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Maintaining ground contact was the main objective. The flex was surprisingly significant - the secondary objective then became preventing contact between the tires & the Frame. Stops were installed to limit the travel on the front axle. And a smooth guide rail directs the wheels underneath the Chassis at extreme steering angles or while being jackknifed, even if the suspension is already flexed. For the rear axles, since they are also connected side-to-side, the tandem acts like a rectangle with ball joints at the corners & the lateral pivot axis in the middle. The movement is therefore limited by the play in the connectors.

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During development & testing, the model would sometimes (annoyingly) roll away if the surface was uneven. The obvious solution was to use wheel wedges, as I sometimes did while my hands were otherwise occupied. But without a drivetrain, there was a bit of room in the axles to attempt an elegant (but simple) parking brake system. After some trial & error, I settled with a liftarm construct that initiates contact with the tires to apply friction, while the engaging lever pivots in a manner that locks the system in both the open & closed positions.

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Initially, the Drawbar was a simple A-Frame with a Steering Arm & Ball Joint pin at the end. After a few inadvertent detachments, a more heavy-duty solution was developed, maintaining 3 degrees of freedom. It is now strong enough to support a 3kg Truck by picking up the Trailer. The first Lift Stand prototype was a spring loaded swinging lever mechanism. With uneven terrain & various possible heights required for the hitch, a more controlled, adjustable deployment was required. The small Linear Actuator was perfect for this. Adding in Caster Wheels now makes for easy positioning. Finally, the length of the Drawbar is intentional because it improves maneuverability while in reverse. Shorter Drawbars are more sensitive to steering input as I found out in a frustrating series of trial & error exercises.

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The Logging section took shape as its own attachment because of the frequent need for removal to access the base trailer. Then came the idea of making a Dumper attachment. In order for this all to work, the Chassis had to be fairly universal. The switch can be made in 2-3 minutes with almost no disassembly of the base.

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Attachment points for the Logger were trivial. Coming up with a tipping mechanism for the Dumper in the available space was a lot more complex. Early prototypes involved the use of actuators. Complete solutions were developed for both Linear & Pneumatic options. Due in part to the weight of the Dump Bed (500g), neither actuator delivered sufficient performance (even with intermediate linkages) in order to lift any significant payload, specifically from the rest position where the required force is the highest. I finally settled on a crank based worm-rack sliding mechanism that works exceptionally well, reaching 45 degrees & with a payload capacity of 1.25 kg.

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At first I used a manual stop to keep the Gate in place. Eventually I figured the spring loaded concept that I originally had for the Drawbar Lift Stand was perfect for this application. There was enough room under the Dump Bed to install a shock absorber & corresponding linkage to lock the Gate. And it remains this way even when tipped, allowing only for manual release. The second option uses a 9L Link that attaches to the Frame which automatically releases the Gate lock when the Bed is tipped.

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When hauling logs, we always want to avoid fines on the highway & a tie-down system is essential. The Logger has 4 cable attachment points, so that ideally each log will be secured in at least 2 places. It was a little tricky to keep it all compact enough to enable ratchet release with a full load against the angle beams & also avoiding the massive suspension flex while strapped down..

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This was a fun project to undertake & it's nice to step away from electronics for a bit. If you've read this far I would love to hear your thoughts & feedback. I was thinking of adding a Tanker & Flatbed options but there aren't too many playable functions involved with those.

Instructions (for both) available HERE

Feature Summary
01. Springless Pendular Suspension
02. Lockable Parking Brakes on rear Axles
03. Adjustable Drawbar Lift Stand with Caster Wheels
04. Heavy Duty 3D Coupling
05. Jackknife capability
06. Easily Adaptable Universal Chassis
07. Logger: Ratcheting Tie-Downs x 4
08. Dumper: Max Tipping Angle 45 deg
09. Dumper: Max Tipping Capacity 1.25 kg
10. Dumper: Manual & Automatic Gate Lock Options

 

More images below.

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PS. The Claw Rig shown in the video is an upgraded 6 x 6 version using a (much more powerful) Buwizz Motor for propulsion, along with many other improvements. I'll post about that later.

 

Edited by P McCatty

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Very nice job and presentation! A trailer like this could easily become an afterthought, but you put a lot of thought and engineering into adding functions and giving them good execution.

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Excellent add-on, well thought for all features and going along well with the truck in terms of design.

I also really liked your presentation for this "deluxe" version of your 8868 interpretation.

Great work!

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On 3/14/2022 at 7:58 PM, 2GodBDGlory said:

Very nice job and presentation! A trailer like this could easily become an afterthought, but you put a lot of thought and engineering into adding functions and giving them good execution.

On 3/14/2022 at 11:34 PM, TangersTechnic said:

Awesome, I never owned 8868 but this is a great rebuild and extras with the trailers :)

On 3/15/2022 at 4:17 AM, Celeri said:

Excellent add-on, well thought for all features and going along well with the truck in terms of design.

I also really liked your presentation for this "deluxe" version of your 8868 interpretation.

Great work!

Thank you! I had a ton of fun making these & trying to keep them as universal as possible. Right now I just have the main Chassis & I switch out the Logger & Dumper attachments as needed. I'm tempted to make another Chassis & link them all together as a road train. It's already super long with a single Trailer. And the thought of trying to reverse the whole thing makes my head hurt LOL. For the updated Claw Rig I'm experimenting with RC4WD Dirt Grabber Tires. They look much better, but I'll have to DIY some new inserts so that they can properly support the weight as the Truck is pretty heavy. The Buwizz motor is so powerful that I've been able to haul a loaded Trailer (approx 6kg total) up steep driveways & over uneven terrain quite easily.

 

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