Fully printable monster truck with four link suspension and four wheel drive and steering with three differentials. I wanted a monster truck that actually looks like a monster truck, and not a truggy with large wheels.
I have uploaded new front and rear diffs. They use stronger and coarser gears. I have run my PLA version hard for a few times with no problems so it's definitely stronger than before. The updated file is GB02-gears.stl
New abuse video with a new lighter printed body. I printed it with 2% infill which saved 130 g. The rear diff now has two ABS bevel gears, which seems to hold up really well. I suspect ABS will be a good, cheap material for bevel gears.
Removed the "gears01" file and replaced it with gear sets specific to the gearboxes they are for, to avoid confusion. The new gear files are called CGB-gears and GB02-gears
Changed the diff bevels slightly to improve gear mesh.
Fixed a slight error in GB02.
Added a servo saver and the associated links.
Added a special version of the GB02 input called GB02-input-onepiece. It's a one piece part that requires that you pause the print between 22.2 mm and 23 mm and install both ball bearings before you continue the print. This creates a stronger part without gaps.
Also changed GB02 with a stronger version after I broke mine while jumping.
I made small changes to GB02-input and mating bevel gears (in gears01). If they break, the new parts have deeper gear mesh for higher strength.
Made slight changes to the lower suspension arms to improve the strength of the screw holes of the clamps. Also slight changes to the outside of GB02 for strength around the bottom area. Still compatible with the previous version.
Added split frame sides for small printers. Frame01-split01.stl and Frame01-split02.stl. Not tested by me.
I added two optional short suspension kits for shortening the wheelbase. Use in the front, rear or both as desired. Each kit shortens the wheelbase by 20 mm.
I added a new axle gearbox assembly which uses a new input shaft which doesn't require carbon rods or filing of flats on the rods. It's easier to make and is stronger. It is uploaded as GB02.STL and GB02-input.STL. I also updated Shaft02.STL with a more robust design. Note that GB01 is still available, but I recommend the new version. The new version replaces two of the 3x7x3 mm bearings per axle for the same 12x18x4mm bearings used everywhere else.
Here's a video showing the performance with a 35T motor and lipos. I don't recommend runnign a lower turn than this. The photo showing the motor and pinion is taken after all my testing is done. The pinin shows no sign of use. Looks new. If you want to run higher turns that's fine:
I added a photo of the truck with a cool lexan body from Banggood.com. Also attached is a photo of body post drilling dimensions, and a photo of the frame without body. Check out the new video with the lexan body.
Changed "Frame03.STL" with an extra cross tube and also made small changed to "Spindle01.STL". Working on all the rive shafts now so new GB-housings, shafts and couplings will come up some time in the next few days.
I uploaded some stronger spindles and live axle housings with stronger spindle lugs.
I made a body for it as well tonight. It is based on a Tokyo Marui Big Bear Datsun body, with modifications to better fit this truck. It has been widened to fit over the batteries and has special body posts. I attached photos both without and with paint.
I appreciate any donations for my hard work and releasing for free, but only if you enjoy the model. ;)
Torture test video with lexan body:
-Tighten the suspension arm clamps around the axle balls untill they allow some movement, but not too tight. The ball joint needs to be able to move with suspension travel.
-The axle gearbox halves may have some uglyness in the top where the 7mm bearing goes. Just remove any excess plastic threads and stuff the bearing in there. I've done it to many units without failure. I might improve this part of the design later on.
-Apply a small amount of grease to the inside of all drive joints so that the plastic knuckles don't melt from friction. I use cheap bicycle lithium grease. Any grease will do.
-Apply grease to all gears. This prevents melting and keeps them working for long. I made closed gearboxes so that they could be greased without contamination. I use cheap bicycle lithium grease. Any grease will do.
-The drive shafts and drive knuckles can be a little tight. They will bed in.
-The gears will bed in if they feel rough in the beginning. Most of the gears seem to be very strong and show no signs of overloading. The differential bevel gears can break with very rough use if they are made from PLA. I eventually printed them from Taulman 910 nylon, which survived my torture tests.
-The smallest differential gears need small shafts to hold them in place. Make these short pieces from 1,75mm filament. Super easy and plenty strong with five shafts on total per diff.
-Ball bearings can be a tight fit, depending on how accurate your printer prints. The holes are designed slightly oversize. Just press them in there or carefully hammer with something that ensures the force hits the outside race. :)
-The lower links flex when the car rolls. This is by design and works well.
-Some parts have alternative parts so that the builder can create variations and change the look of the truck.
-The screws all thread into the plastic parts without any metal nuts. It may be difficult to screw them in the first time.
-Though the hardware list calls for machine screws, similarly sized self tapping screws will work fine in most cases. The exception being where the part is supposed to pivot on the screw, like the spindles and suspension link hinges. The length can also be different than the recommended in many cases as the holes are usually much deeper than necessary.
-The rear steering servo needs to be reversed. If it can not be reversed in the radio the longer servo link can be used instead by connecting to the top servo arm instead of the bottom.
-The diff lock gear is not recommended for jumps and high speed bashing because it increases the load on the whole drive train.
-GB02 is recommended, but if you for some reason still want to use GB01, here are instructions: On GB01 The input shaft on the live axle is made from 3mm carbon fiber rod. File flats on each end to fit in the gear and shaft joint and . The flats don't have to be perfect. Also apply CA glue to the flats when assembling. The gear ratio between the input and wheels is 5:1.
-540 or 380 motor and ESC. The prototype uses a 21t GoolRC brushed motor for overload testing. I recommend a minimum of 35T. Search for "320A esc" on Ebay for cheap esc. The best ESC for it is the Hobbywing Quicrun 80A "Crawler Brushed" ESC which can be set up to run with reduced brake and reduced punch which extends the gear life considerably: http://hobbywing.com/goods.php?id=543&filter_attr=5426.5599 this ESC is also available from Hobbyking.
-Metal gear servos. Maximum 23mm body length. I use these: https://hobbyking.com/en_us/corona-ds-843mg-digital-high-torque-micro-servo-4-8kg-0-10sec-8-5g.html
-Six cell Sub-C ni-mh battery or 2S hard body lipo.
-The springs are made from regular road bicycle tubes. Cut them as wide as you need to get the necessary tension. The butyl is very durable and won't rot. I used one of my old punctured tubes. I also use these rubber bands to hold the battery in place.
-In addition to the printable body you can use other bodies. I ordered this body which fits well: https://www.banggood.com/RC-Car-Spare-Parts-Shell-For-Traxxas-Grave-Digger-RC-110-RTR-Truck-p-961475.html?rmmds=myorder
-Four monster tires. I have not designed printable tires for it because it would take an absurd amount of rubber to make them and it's just so cheap for good tires. It probably takes less time to order and receive than it takes to print as well. :P I use the chevron version of the two in the following links:
-7 3mmx19mm carbon fiber or brass shafts for the diffs and live axle gearboxes.
-4 to 8 3x7x3 ball bearings. Search for "3x7x3 10pcs" on ebay for cheap bearings.
-20 12x18x4 ball bearings. Search for "12x18x4 20pcs" on ebay for cheap bearings.
-44 M2x8 screws - differential gearbox assembly, upper four link clamp and steering link assembly. 24 of them for assembly of the two piece wheels.
-2 M2.5x22 screws - For mounting a 380 sie motor.
-22 M3x8 screws - Main frame assembly and steering spindle assembly.
-8 M3x12 screws - Lower suspension link and upper rubber band posts.
-6 M3x22 screws (M3x24 can also be used) - 540 Motor mount and lower rubber band posts.
-4 M4x20 screws - For the wheels.
Steeringlink01.STL - Steering links.
Steeringlink02.STL - Offset steering link for the servo saver.
Servosaver01.STL - Servo saver for installing onto the servo arm.
Bodypost01.STL - Shortest body post.
Bodypost02.STL - Body post.
Bodypost03.STL - Body post.
Bodypost04.STL - Body post.
Bodypost05.STL - Longest body post.
Bodypost05.STL - Body post for the rear of the Banggood Vampire Ghost Lexan body. Use file Body04.STL for the front posts for that body.
Suspension01.stl - Lower suspension links. Alternative 1. Choose the one you like.
Suspension02.stl - Lower suspension links. Alternative 2. Choose the one you like.
Suspension03.stl - Upper suspension links.
Suspension04.stl - Lower suspension bushing and rubber band flanges.
CGB-380.STL - Central gearbox and pinion for 380 size motors.
CGB-540.STL - Central gearbox and pinion for 540 size motors.
CGB-gears.STL - Central gearbox gears.
GB01.stl - Old version live axle gearbox housing.
GB01-input.stl - Input coupling and bevel gear for the old GB01 housing.
GB02.stl - New and improved version live axle gearbox housing.
GB02-gears.STL - GB02 gears.
GB02-input.stl - Input coupling and bevel gear for the new GB02 housing.
Gears01.STL - Gears and differentials.
Difflock01.STL - Locking "gears" for the diffs. Use if you want to lock the diff. Untested!
Shaft01.STL - Live axle drive shafts
Shaft02.STL - Central drive shafts.
Spindle01.STL -Steering spindles.
Frame01.stl - Main frame sides.
Frame02.stl - Front and rear frame pieces. Alternative version 1.
Frame03.stl - Front and rear frame pieces. Alternative version 2.
Frame04.stl - Front and rear frame pieces. Alternative version 3.
Wheel01.stl - Monster truck wheel.
Body01.STL - The nose of the pickup body.
Body02.STL - The cabin of the pickup body.
Body03.STL - The bed of the pickup body.
Body04.STL - Posts with extra room for the thick printable body.
ShortWB01.STL - Suspension kit for shortening the wheelbase. option 1 arms.
ShortWB02.STL - Suspension kit for shortening the wheelbase. option 2 arms.
All parts are supposed to be printed in the orientation they open. No support should be necessary. The live axle gearboxes have cylindrical support built in, which is easy to break off after printing.
The prototype was made exclusively from PLA.
For the body I recommend printing with one perimeter only, and about 2% light infill (rectilinear or "fast" infills that don't cross over on every layer). The nose piece needs to have a plane to support the detail in the grille at 105 mm. The rear piece also needs a plane to support detail when it gets to 168.8 mm to support the inset pieces of the tail gate. I changed from 2% to 10% at these points, and added a few full layers to give support.
For longevity, the bevel gears in the axle differentials can be printed from a tougher material, like Taulman 910 nylon. I did this to mine after a severe braking and acceleration test session killed the PLA gears. The central differential is fine in PLA.
I printed just about everything with 30% infill. Wheels 15%. I recommend printing the spindles at 100%. Up the infill if you have problems.
Good layer adhesion is very important for many parts, so no skimping on the temperature.