Losi JRXT 3d printed parts

[Lizardking]

Just wanted to share my Losi JRXT 3d printed parts. My truck was actually a JRX2 buggy that was converted using a JG kit. The kit included the truck body, high offset wheels, tires and body mounting hardware. While the wheels are actually fine and kinda dope, the mounting hardware left something to be desired. I get that it was an early mod where people were converting their buggies to trucks, before the JRXT even existed, but it looks handmade and idk … off.

When Losi finally designed and released the JRXT based on the buggy, the mounting posts looked much better, particularly the front bumper/post combination. To me it looks iconic and makes the truck body with the mounting points towards the front look “correct”.

Anyways, I borrowed the 3d model from a guy who made an exact replica of the bumper/mounting posts of the original parts for the JRXT mini. I printed the first one by increasing the size to 160% of the original (1/16 to 1/10 is a 60% increase). After ~6h of printing i tried installing it and found that it was too big by about 3mm when measuring the bolt holes with a caliper. The exact size you want to use is 147.3%. I confirmed it by printing again and fitting the bumper. Props to the guy who painstakingly modeled the bumper. I used ABS for added toughness, 50% infill (might increase it but part becomes heavier) and 120F build plate temp and 225F nozzle temp (140 F default is too “melty” and deformes the part). Printed at an angle for more shear strength with tree supports and adhesion. Printed on an older Ender 3. These bumpers are going for $100 on ebay

I dont know about you guys and how you feel about 3d printing parts for old RC’s. Personally it has saved me $, and even being able to drive some cars where the parts don't exist anymore. I have fixed many cars like this, mostly mini-z where the plastic motor housing and shock mounts become brittle and the replacement is not subjected to extreme forces.

This is the link for the models: https://cults3d.com/en/3d-model/game/losi-truck-style-body-mounts-for-the-mini-jrx2-work-in-progress

Will post more photos as I progress.

[Lizardking]

Mounting posts

[Dangeruss]

That's pretty cool the mini sized up with the holes in the right place and everything. Could probably upload it to Shapeways and make a few bucks. I dunno what's up with them but they're still letting customers shop and add things to a cart, though I haven't tried to check out yet.

3D printing is cool, but depends on expectations. Most home 3d printers aren't going to produce particularly nice results. And you have to ask what your time is worth. It's a hobby so, different for everyone there but... I think on RC cars it excels with nonexistent parts, or solution parts to replace something else.

All this of course is if you're not SilverTriple who can 3D print objects that you'd swear were injection molded... which I still say they are!

Seriously impressive that you were able to get the mini body mount to size up, print, and bolt on though. ...but, less handmade looking than the JG mounts... mmmm.... noooooo

[Lizardking]

When I finish I’ll show the results with the before (JG) and after (3d printed) so everyone can see. I still have to clean and deburr and sand the prints, and maybe airbrush them using black paint to match or dye them as we did with nylon back in the day. Still deciding. I may be alone in not loving the JG body posts.

The link i posted is from someone else's model. If I put it somewhere it would be a remix, and for free. Maybe on thingverse.

Getting the body on Friday. Will keep posting.

[Lizardking]

Rear post

[Lizardking]

Re-doing the front skid plate. Increase nozzle temp from 225 to 230 for better binding. Re-orienting the part on its side so edge of the “L” shape is on the z-axis (weakest layer bond). This way filament runs continuously from back to front of the plate. This way hitting an object will apply forces to the x-y axis layers. Shear impacts (t-bone the front) will be more suceptible but there is more “meat” in that direction. I believe this will make it stronger.

[Lizardking]

Stress failure points. Notice the stringing of the material. Needs to melt more for better binding.

[Lizardking]

Front skid came out muuuuch better using 70% infill and reoriented on the build plate. This is the ABS printed parts vs the vintage JG mounts. Decent weight savings, particularly so high up from CG. Getting the repro body tomorrow.

[Lizardking]

Printed this servo holder from the same material as the body posts/skid (ABS). The graphite chassis already had two holes drilled into it to hold the servo down but it was super wobbly.

Side note: Losi really thought double sided tape would hold a servo down? Early days I guess…

The holes were not countersunk, leaving the two cap-heads hanging below the chassis. The servo was also held to the posts with the little rubber grommets that come with them. First time I’ve seen that in a car to be honest.

I was able to hold the servo down very securely with inly two screws and the printed part. Really neat. If i strip the servo I can replace it with a metal gear one. Maybe thats what the grommets were for…

The file can be found here: https://www.thingiverse.com/thing:3318566


Printed 70% infill. For integrity you need to print it on its side to take advantage of the xy plane bond strength. This came out better than I expected.

I’m not sure if I want to paint or try to dye the ABS. Might just leave it white and save my energy for painting the body.

[Lizardking]

Forgot to mention the steering was binding. Had to clean those cups they were full of dirt.

[Lizardking]

Final install. Took a bit of positioning and trimming to make it so the body does not scratch the wheels while fully turning and compressed. Now we paint.

[RogueIV]

That's pretty cool the mini sized up with the holes in the right place and everything. Could probably upload it to Shapeways and make a few bucks. I dunno what's up with them but they're still letting customers shop and add things to a cart, though I haven't tried to check out yet.

3D printing is cool, but depends on expectations. Most home 3d printers aren't going to produce particularly nice results. And you have to ask what your time is worth. It's a hobby so, different for everyone there but... I think on RC cars it excels with nonexistent parts, or solution parts to replace something else.

All this of course is if you're not SilverTriple who can 3D print objects that you'd swear were injection molded... which I still say they are!

Seriously impressive that you were able to get the mini body mount to size up, print, and bolt on though. ...but, less handmade looking than the JG mounts... mmmm.... noooooo

Shapeways is bankrupt and no longer doing business. The website is still there but no one is there to support it.

Also I had done similar with the front mount. I didn't have the body mount portion to the front bumper and I used the measurements from the Mini JRXT and scaled them up.

The mini JRX series isn't a direct scale as they have a few different scales they use depending on the parts but you can reverse engineer parts off of the minis and scale them using the proper scale to make a pretty convincing 1/10 scale part.

[RogueIV]

Printed this servo holder from the same material as the body posts/skid (ABS). The graphite chassis already had two holes drilled into it to hold the servo down but it was super wobbly.

Side note: Losi really thought double sided tape would hold a servo down? Early days I guess…

Just about everyone back in the 80's used double sided tape or "servo tape" to hold the servo down. This had a pretty good benefit back in those days as servos were much weaker and more prone to stripped gears, the tape would act as a servo saver allowing it to absorb impacts during crashes without destroying the servo. Also, it's lighter than extra screws and mounts, and back then lightness was everything, I mean look at all those drilled out chassis from back in the day! People woul literally spend hours drilling out a chassis to save like 20grams...

[Dangeruss]

Shapeways is bankrupt and no longer doing business. The website is still there but no one is there to support it.

Something's up with Shapeways... what company goes bankrupt and leaves the site up like it's business as usual.

Didn't know you'd scaled one of the front body mounts up before, very cool.

Yep, servo tape works fine. Cheap tape would let loose, but good 3M tape is almost permanent... ask anyone who's ever tried to remove it.

Notice only Associated owners drilled their chassis'... us Losi guys didn't need to.

[Lizardking]

Printed this servo holder from the same material as the body posts/skid (ABS). The graphite chassis already had two holes drilled into it to hold the servo down but it was super wobbly.

Side note: Losi really thought double sided tape would hold a servo down? Early days I guess…

Just about everyone back in the 80's used double sided tape or "servo tape" to hold the servo down. This had a pretty good benefit back in those days as servos were much weaker and more prone to stripped gears, the tape would act as a servo saver allowing it to absorb impacts during crashes without destroying the servo. Also, it's lighter than extra screws and mounts, and back then lightness was everything, I mean look at all those drilled out chassis from back in the day! People woul literally spend hours drilling out a chassis to save like 20grams...

Yeah, this is my first time experiencing the JRX2/T and have to say the graphite plate is surprisingly light while also being extremely stiff. Feels high tech even by today’s standards (actually higher tech with everything being plastic nowadays). My early build experiences were tamiyas and an RC10B2 which had a the servo tied down. I admit super high quality 3M tape would probably hold well enough. Thanks for the responses. Great knowing people actually reading this