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15mm longer arms and the gearbox is free floating need to make a panhard rod to stop lateral movement , top right arm is pretty close to the motor so I'll move it outward 4mm at the axle end , the arms came out more parallel than I planned anyway , the JRX2 arms flare outward more and that's the look I want . Also need to give it new shock mounts with the axle 15mm further back .
At the moment the original rear suspension pivot points clear the axle so the gearbox could be left whole but I think I'll lop off the whole mess from the gearbox once I have a firm plan for the panhard rod. The trailing arm shape can be further refined too now I know it's working .

A little silent movie of the rear suspension , the Panhard rod is some old butchered parts I had laying about but I'll model one up for Thingiverse . There is a little lateral movement that I tried to show at the end of the clip , it's caused by the arm flexing , as this is home printed I kept the inner side of the arm flat so the ball sockets printed well , in an ideal world there would be re-enforcement ribs like the outside to reduce the flex , again I can add them for Thingiverse as an option .

https://youtu.be/Zmv0B1NiHmM

What a happy coincidence- the original suspension mount was perfectly positioned to be used for the panhard bar mounting point

This is a very cool project. Thanks for posting!

If this is heresy, let the Inquisitors take me away....

I’m disappointed you took the easy way out with a Panhard instead of doing a Watt’s link.. Just kidding! Looks great! I can’t wait to see a vid of this going over jumps and rough terrain.

BattleTrak wrote: ↑Wed Jul 20, 2022 8:07 pm I’m disappointed you took the easy way out with a Panhard instead of doing a Watt’s link.. Just kidding! Looks great! I can’t wait to see a vid of this going over jumps and rough terrain.

A mate of mine said the same thing about a Watts linkage , truth is the Panhard rod really doesn't move a great deal and the arc of lateral axle movement is imperceptible, I may have to beef up the trailing arms for running though as they won't take much abuse , undecided on the material to print final parts in , Polycarbonate would be too brittle like these PLA test arms , plain or even CF Nylon would be rather noodly but impact resistant and it's not a big deal if they flex a bit , not sure .

Got the hopper body fitted , needed the cutout for the motor elongated , also got some temporary front shocks fitted , really crappy WLtoys A959 shocks but the fit is good as is the spring rate .
Just got to fit some electronics and I can give her a whirl.

Little video , still hopping I'm pretty sure its just over sprung , it bounces on a static drop , could be the tires as well , the front is working well though .

https://youtu.be/QjHalURBCv8

Your awesomely fast progress is putting my Hyper Hornet project to shame. The is a very cool Grasshopper! Well done!

Frankentruck wrote: ↑Tue Jul 26, 2022 9:12 am Your awesomely fast progress is putting my Hyper Hornet project to shame. The is a very cool Grasshopper! Well done!

I'm long on time short on money right now so I can work fast on stuff that's made with materials on hand.

Just stumbled onto this project....pretty cool!

Cool running video!

Starting to think the hopping is now due to the overall weight of the rear drive and motor , if I move either wheel it's really free but if I thump the diff upwards moving the whole transmission it's a lot of mass , I'm now definite that it's not the axle torque twist , I can lift the car by the rear axle keeping the chassis horizontal effectively torquing it counter to wheel rotation and the suspension still moves freely , it's just the mass , maybe thicker oil in the shocks ?

The design of these buggies with the motor and gearbox hanging from the shocks does result in a lot of the buggy weight being unsprung weight. The shocks really can't do anything to help with it. The rear tires are the shock absorbers for handling the bouncing due to the motor and gearbox weight, and then whatever bouncing the gearbox does gets pogo transmitted into the chassis through the rear shocks. Maybe softer rear springs and lighter oil to upset the chassis less? Not sure if much else can be done without a gearbox setup change.

Frankentruck wrote: ↑Tue Jul 26, 2022 11:20 am The design of these buggies with the motor and gearbox hanging from the shocks does result in a lot of the buggy weight being unsprung weight. The shocks really can't do anything to help with it. The rear tires are the shock absorbers for handling the bouncing due to the motor and gearbox weight, and then whatever bouncing the gearbox does gets pogo transmitted into the chassis through the rear shocks. Maybe softer rear springs and lighter oil to upset the chassis less? Not sure if much else can be done without a gearbox setup change.

I've been eyeing ways to lose weight in the axle , I've bobbed off the stock pivot point completely but other than fitting a smaller BL motor there's not much to do .