mung
Sr Member
Almost 10 years ago in 2015 I did a post on my blogsite called Giant Tyres and DIY PVC wheels.
In that post I showed a method of making some beadlock wheels out of PVC plumbing parts for the super massive Interco Super Swamper 40 series tyres from RC4WD.
The tyres are 250mm in diameter (10") and weigh over a kilogram each and I had 3 pairs, planning to make a 6x6.
The tyres in question are on the left with Proline 3.8 trenchers in the middle and Imex Jumbo Maxx (3.2) Swampers on the right.
Later that year (2015) I did a post about a test rig to see if I could make a motor per wheel set up work using a Traxxas EVX brushed speed control running three motors per side.
I found that it did indeed work using cheap 540 geared motors using Imex Jumbo Maxx tyres and Losi ATX tyres with a 500rpm (at no load) gearbox.
I determined that due to the increased circumference, 1.4 times greater, the Interco Super Swampers would need gearing down somewhat.
Over the last 9 years I have pulled the tyres and wheels out of their boxes and then promptly put them back in again.
There have been a number of body concepts and chassis suspension ideas all eventually rejected.
I had another false start when a purchase of a set of gearmotors turned out to be too weak finally much later I settled on some more 540 brushed motors paired with 160rpm gearboxes that seemed to have the required torque.
Last year I made some progress on the chassis of another 6X6, the suspension of which which helped solidify the design for this project.
I also had bought a cheap 3D printer and got used to thinking about making more complex parts for my extremely low budget projects.
In 2024 I finally felt I had the confidence to tackle probably the largest RC scifi vehicle I will ever attempt.
First thing I did was build a prototype suspension arm and figure out the shock position required.
I am using Traxxas GT shocks from a Traxxas Summit.
These are designed to take the very large leverage of an inboard shock arrangement so are good for a very heavy direct suspension at the expense of considerably reduced suspension travel.
I figured the shock would work at about 30% percent of the distance from the pivot point to the wheel centre.
This gave me enough support to hold up what will inevitably be an extremely heavy model, and still have a reasonable amount of suspension travel.
Moving the shock further towards the pivot will result in more travel but with less weight capacity and vice versa.
It's a bit of a balancing act and I can only judge this by feel rather than by any advanced engineering skills or math.
There is a 10mm flange on both sides of the chassis wall with a 10mm rod holder gripping a short 10mm aluminium shaft.
The flanged bearings have grub screws to prevent the suspension arm sliding out.
The rod holder is mated to some rectangular 20mm x 40mm aluminium tube via a 3D printed part.
All the 3D printed parts were printed in PETG and designed to be an interference fit inside the aluminium tube.
They were secured with countersunk bolts and nylock nuts.
The final red parts were printed at home on my cheap Anycubic Kobra Neo whereas the black prototype parts were printed on the Prusa MK4 at work.
The Prusa prints are generally much smoother and certainly a lot faster to print but the machines cost considerably more to purchase.
At the other end is another 3D printed motor holder which clamps onto the motor can.
These particular motor gearbox combinations came with a mounting plate at the front which is also attached back to the 3D printed motor holder with M5 threaded aluminium spacers.
The wheels are mated to slightly modified Traxxas 17mm hubs with a grub screw securely loctited against the flat on the gearbox shaft.
With the suspension sorted out I started on the chassis proper and drew up a side layout in CAD.
Then I needed a cut outline as I was planning to build the chassis out of two layers of 6mm Foamed PVC.
Usually I do this by hand as described many times in my projects but in this instance made use of the CNC router I have access to at work.
All the mounting holes for the suspension bearing flanges were cut at the same time.
It would be nice to have one of these at home but I do not have the space or crucially the cash.
The layers were glued together with super glue after first roughing up the mating areas with coarse sandpaper.
The rest of the chassis was built from the same material making a long open box with a 45 degree angle at the front and a 15 degree angle at the rear.
To be Continued...
In that post I showed a method of making some beadlock wheels out of PVC plumbing parts for the super massive Interco Super Swamper 40 series tyres from RC4WD.
The tyres are 250mm in diameter (10") and weigh over a kilogram each and I had 3 pairs, planning to make a 6x6.
The tyres in question are on the left with Proline 3.8 trenchers in the middle and Imex Jumbo Maxx (3.2) Swampers on the right.
Later that year (2015) I did a post about a test rig to see if I could make a motor per wheel set up work using a Traxxas EVX brushed speed control running three motors per side.
I found that it did indeed work using cheap 540 geared motors using Imex Jumbo Maxx tyres and Losi ATX tyres with a 500rpm (at no load) gearbox.
I determined that due to the increased circumference, 1.4 times greater, the Interco Super Swampers would need gearing down somewhat.
Over the last 9 years I have pulled the tyres and wheels out of their boxes and then promptly put them back in again.
There have been a number of body concepts and chassis suspension ideas all eventually rejected.
I had another false start when a purchase of a set of gearmotors turned out to be too weak finally much later I settled on some more 540 brushed motors paired with 160rpm gearboxes that seemed to have the required torque.
Last year I made some progress on the chassis of another 6X6, the suspension of which which helped solidify the design for this project.
I also had bought a cheap 3D printer and got used to thinking about making more complex parts for my extremely low budget projects.
In 2024 I finally felt I had the confidence to tackle probably the largest RC scifi vehicle I will ever attempt.
First thing I did was build a prototype suspension arm and figure out the shock position required.
I am using Traxxas GT shocks from a Traxxas Summit.
These are designed to take the very large leverage of an inboard shock arrangement so are good for a very heavy direct suspension at the expense of considerably reduced suspension travel.
I figured the shock would work at about 30% percent of the distance from the pivot point to the wheel centre.
This gave me enough support to hold up what will inevitably be an extremely heavy model, and still have a reasonable amount of suspension travel.
Moving the shock further towards the pivot will result in more travel but with less weight capacity and vice versa.
It's a bit of a balancing act and I can only judge this by feel rather than by any advanced engineering skills or math.
There is a 10mm flange on both sides of the chassis wall with a 10mm rod holder gripping a short 10mm aluminium shaft.
The flanged bearings have grub screws to prevent the suspension arm sliding out.
The rod holder is mated to some rectangular 20mm x 40mm aluminium tube via a 3D printed part.
All the 3D printed parts were printed in PETG and designed to be an interference fit inside the aluminium tube.
They were secured with countersunk bolts and nylock nuts.
The final red parts were printed at home on my cheap Anycubic Kobra Neo whereas the black prototype parts were printed on the Prusa MK4 at work.
The Prusa prints are generally much smoother and certainly a lot faster to print but the machines cost considerably more to purchase.
At the other end is another 3D printed motor holder which clamps onto the motor can.
These particular motor gearbox combinations came with a mounting plate at the front which is also attached back to the 3D printed motor holder with M5 threaded aluminium spacers.
The wheels are mated to slightly modified Traxxas 17mm hubs with a grub screw securely loctited against the flat on the gearbox shaft.
With the suspension sorted out I started on the chassis proper and drew up a side layout in CAD.
Then I needed a cut outline as I was planning to build the chassis out of two layers of 6mm Foamed PVC.
Usually I do this by hand as described many times in my projects but in this instance made use of the CNC router I have access to at work.
All the mounting holes for the suspension bearing flanges were cut at the same time.
It would be nice to have one of these at home but I do not have the space or crucially the cash.
The layers were glued together with super glue after first roughing up the mating areas with coarse sandpaper.
The rest of the chassis was built from the same material making a long open box with a 45 degree angle at the front and a 15 degree angle at the rear.
To be Continued...
