Raptor Pre-Runner Build

[Raptorn]

Repeating myself: Time to get going again!

I didn't like the second chassis I began to build, so I started from scratch again. The first chassis had major alignment issues (because I made my own A-arms) so I decided to use the Axial Exo Terra parts I had. The only thing I bought for chassis version three is a motor to replace the one I burnt to a crisp almost exactly 3 years ago.

Between parts recycling and my 3D printer it took very little time to mock up. It took me more time to learn Fusion 360 than anything else (frustrating because I'm a CAD wizard at this point). Track width is barely within the fenders, which is lucky because those front arms cannot get any closer together.


I also had binding issues with the 4-link so instead of putting in effort or investigating why I just used Exo shock mounts (I think?) as trailing arm brackets. Fixed! The wood plate is structural.


I got busy bending, brazing, and burning myself repeatedly. It somehow ended up looking nice even though I did no planning. The structural wood was replaced with ferrous material. The 3D printed front suspension part went through a half-dozen revisions in between rebuilding my temperamental CNC noodle maker a half-dozen times.




The cage conforms nicely to the body and the wheels tuck into the fender perfectly (oops no pic). At this point my quarantine project was a roller. Seeing how fast I made chassis try 3 makes me hurt inside. The first time it took a year and a half to reach this point. I'll chalk time savings up to knowledge and experience - and not spending any time planning.

[Raptorn]

The only thing between rolling and driving is motivation - I mean steering. Once again I take the easy route and just hang the servo horn underneath the chassis where it will be ripped off by a rock at some point (oops no pic again just use your imagination).

Then I just piled all the running gear on top and went for a ride. Yes the battery is just clamped on.


It looks like a menacing rock bouncer from this angle.


It shocks me that it drives well. With too soft tires and heavy weight it has enough grip to do small wheelies and roll over on hard turns. Even on 2S it was fast. I gave myself carpal tunnel writing my list of things to fix/improve.

[ferp420]

crazy fab work going on starting from scratch is huge kinda makes me feel like a cheater just droping the body on to a yeti and calling it a day
my plan orininaly was to do a bunch of tube work and make a nice cage but as i started fitting everything it kinda all droped in to place

[Raptorn]

In today's progress: I give the truck the Carolina lean. Also the rear bumper is complete.




It ended up looking very similar to New Bright's plastic bumper, probably because I copied the design. Not really though, I found inspiration in trucks on Race-dezert and Google images.

The battery will go under the bed to help weight distribution.


I ran out of steel making these pieces, then as I applied flux to the last two joints it started raining on me. I made it though!

[Raptorn]

It takes a lot of work to make it look like nothing progressed.

I remade rear links because the axle was not in the right place. I rebuilt and changed spring rates on the shocks (had a horrible time, what a mess). I re-made steering links to correct geometry. I reinforced the center skid mounting. The transmission housing stripped (mostly user error, with some abuse mixed in) so I put in an aluminium one (that's metric aluminum) and reinforced it's mounting. Then some more trimming on the body.


I made a cozy home for the battery.


And because this battery got soft and lazy during quarantine, it wasn't willing to stretch to reach the ESC. How rude. So I had to go out of my way to make an extension cable.


On top of that, every plastic part in the front end is brand new. I got a 3S battery because I have the need for speed! Turns out I have the need for better handling characteristics. On another test drive I was reminded of my suspension tuning ineptitude. It looks like a stadium super truck when it corners, but only on left turns. The torque lean is so bad it lifts a front wheel. It is extremely unstable under acceleration, and I lost control on the first full throttle pull. It only rolled five or six times - oops.



Since the wheels appear to be out of alignment, I went to print another front end. I put in hours making design and strength improvements to suspension parts. I was rewarded for my effort by 5 failed prints in a row. After considering lighting the printer on fire, I decided to fix it because I really want to drive this truck. Thankfully I pay myself in Fig Newtons, because the labor bill for this installment would have been astronomical.

Up next is a real front bumper because I anticipate crashing more.

[ferp420]

you might want to protect that battery better to all it takes is to kick up a stick and its new battery time

[HumboldtEF]

Maybe you can incorporate some reinforcement to the front bulkhead with some steel rod or flat stock.

[Raptorn]

Originally Posted by ferp420

you might want to protect that battery better to all it takes is to kick up a stick and its new battery time

Originally Posted by HumboldtEF

Maybe you can incorporate some reinforcement to the front bulkhead with some steel rod or flat stock.

It is on the (lengthy) to-do list! I haven't figured what material how they attach, but some panels around the battery (front, sides) are in the future. Until they are done I'll just not run over any sticks.

Idea similar to these: Project Zeus: Cycon's Steven Eugenio Trophy Truck Build

[Raptorn]

In anticipation of an inevitable total disaster while driving I started on the front bumper. I wanted something slim and unobtrusive - not the giant stingers cool cats put their slow jeeps. Something like this-


A little cutting, a little bending, a little bit of squinting, and BAM!


On second thought you need more than a little bit of squinting. My panel gaps make Tesla owners jealous.

Everybody loves triangulation, so I added a sprinkle.


Then I really went for it. That aughta be enough to take some hits.

[Raptorn]

Since my battery is a fragile wimp I created some paneling to protect it from nature (and to satisfy the peanut gallery). I carefully brazed M3 nuts to the chassis to hold them on securely. When the body is on the battery is accessible from the rear underside, so I finally can take the battery out without any tools!


To address the truck's horrid torque lean I procured a Wraith swaybar kit. Then a little cutting and filing, then searching stores for a 2.5mm drill bit (or close enough), and I arrived here.


The swaybar mounts turned out great, if I say so myself. I can file steel better than I can take a picture, I promise. Test drives will tell if torque lean and tire lifting are mitigated but it feels so much better just poking it on the bench.

[Raptorn]

Someone commented on YouTube asking for more raptor videos. I now graciously bestow upon the RCC community another "masterpiece."

[Raptorn]

I found a job I hate more than filling shocks with oil: gluing tires. On the bright side, the stiffest foams I could get from CI made a big difference. It is like going from 8psi to 28psi in real tires.


Excited about my newly firm tires I went for another drive. This is exactly how far I got: 15 feet before the pinion said “I’m out.”


Very luckily the pinion was right under the truck, not lost forever in the dirt. I shamefully walked back to the car, drove home, put loctite on, drove back and resumed. Stiff foams and a swaybar calmed the truck down significantly. At the end of a battery I noticed the truck was leaning more and becoming more unpredictable - guess what else I forgot to loctite. Thankfully the swaybar kit came with extra grub screws... Then a rear shock dumped out it’s oil (no pic of the Exxon-Raptor Valdez).

Fine, it’s fine, the truck is going just fine.

It does look good though.

[Raptorn]

While the mailman is delivering new seals for the shock I got carried sway with tearing things down. The chassis plate is very heavy so I cut some out and replaced it with plastic sheet. I also brazed on plenty more nuts for mounting panels around the battery and finally made some body mounts. I don’t like body clips, so I used 3M dual lock- a better Velcro. Then a LOT of sanding rust off and painting.




After final assembly the truck weighs in at 9 lbs RTR. Still pretty heavy, but I think I could have done worse. This lead to a milestone - IT COMPLETED A DRIVE WITHOUT BREAKING!

I made this FPV camera mount out of the first version chassis. Don’t get excited - it vibrates so bad the footage is utterly unwatchable. I had high hopes but I just got hot garbage.

[j0e]

Pretty freakin' awesome, man!
GREAT metal work.

[BJ40Fin]

I keep getting amazed by the frame you've done everytime I see it! so awsome!, as j0e said.. Great work

[350TacoZilla]

Good work! when you said pinion I thought you meant you snapped the pinion gear in rear for a second lol, much easier fix for the motor pinion.