My Lincoln Electric Rock Crawler Tuber
By Tony Arnold - StampedeProject.com
After a couple welding projects to get my metal burning techniques up to a tolerable level, I embarked on a another fun project... a 1/10th scale RC Rock Crawler with a tube style chassis. Since this little project is solely possible due to my super easy-to-use Lincoln Electric Power MIG 140C wire feed welder, I decided it should be Lincoln Electric themed.
Steel cage tube style chassis are typical in the real 1:1 scale Formula One Off Road rock crawler racing that is now growing rapidly across the US. Even in the hobby scale side of RC rock crawling, tube style chassis have become common. The major difference is that they are typically made from 1/4" or smaller steel/aluminum rod as small tubing would not have the strength to hold up to the stresses of 3-10 foot drops from rocks.
For my build I used three readily available 3/16" X 3' steel rods and set up a simple rod bending jig by clamping two 1/2" bolts in my vise to bend the rod around. With a bolt on each side and the rod feed in between, the rod can be easily bend in a controlled manner to allow for repeatable bends.
WORK DAY 1
With the target idea of having the chassis almost as long as the wheelbase (12.5") and a maximum width of 3", I started by forming the chassis's upper deck by bending one of the rods at it's center at a 90 degree angle. I measured down about 4" on each side and made two 45 degree bends and repeated the process where the rear of the chassis meets up. After the last two 45 degree bends, I bent both rod ends toward each other and cut them so that they matched and met flush.
Using my Axial AX10 RC Crawler chassis as a guide, I took two more rods and measured and cut, and bent them using 45 degree bends leaving 3.5" of room (front to back) for the transmission mount area. I basically copied these pieces again to form the cab and roof pieces. I wanted the cab to angle in a bit, so I made the top roof cross braces 2" each. Above you can see I have also made a couple shock mount hoops. These were simple nice easy near 180 degree bends with one leg shorter than the other so they would angle forward a little. I also clamped the from and rear of the chassis into the vise and bent them up give the chassis a little style.
WORK DAY 2
I was able to get the main chassis welded together and the front shock mount hoops. Since I have not layed out the cash for my Argon bottle yet, I am using standard gasless flux core wire so the welds get a little slaggy (at least in my hands). Oh well a grinding we will go.
I worked through fabricating the full length steel skid plate, the cross and other braces and link mounts. Not pictured are the rear hoops I bent up and have ready for welding together hopefully tomorrow.
WORK DAY 3
Today I finished up welding all the braces and pieces in place. The good news is that I didn't blow through any of the plates during welding, but I did accidentally dismember one of the side braces. Ohhhh I look forward getting an Argon tank for some slag-free welding - I think I might nick name this thing the porcupine or the Hedge Hog. I could use this as a medieval battle mace it has so much slag on it. Ohhh dear God this is going to suck from a grinding and sanding perspective. I foresee a week at least just to get this to the point where it will be paintable, touch up Bondo and then use that super thick coverage primer and then probably repeat the process a couple times. Let the finishing begin... this is going to suck...
WORK DAY 4
A night of scraping, grinding, Dremeling, and sanding and I stopped to put my first thick coat of primer to see the areas I would still need to work on. Luckily most of the light to medium imperfections were covered and smoothed out by a couple coats of primer. Obviously I have some filling and final sanding of a few area but I am getting there.
WORK DAY 5
Today I was able to do the final filling, finishing, and another couple heavy coats of primer to fill any remaining imperfections. It took a little time and patience to assure the holes I drilled for shock and link mounting were even from side-to-side. The key to this project so far is to take your time. Every time I get in a hurry I screw something up.
WORK DAY 6
Last night I did a little more sanding after priming and drill all the holes for the shock mounts. After a couple coats of gloss black Rustoleum High Performance Pro Enamel on the chassis, it's finally starting to look like something.
I am still letting the 24 hour dry process finish before I do the link mount holes and then do a final coat. Sorry no pics today, I didn't want to chance messing up the paint.
Other parts in process:
- Ordered some small Lincoln Electric Stickers to make the branding a little easier.
- Spun some 5/16" Stainless Steel lower links in my Proxxon Mini Lathe...that will never ever, ever, ever... break.
- Picked up yet more steel, this time 1/4" and 3/4", you'll have to wait and see on what I do with that.
- Some 1/8" thick Lexan for the body panel.
WORK DAY 7-9
I have accepted the fact that the finish will never be perfect since I didn't weld using gas and there is still slag here and there that is in places I just can't get to. Overall though it looks pretty good for my first chassis ever made. The first round of paint is dry and hard enough to start drilling the front link mount holes after a ton of measuring and figured out the final shaft lengths. I wanted to avoid having a grid of adjustment points and run with just the single mount points so hopefully I will get lucky. My intent is to have the upper and lower links all roughly the same length for better geometry on a 4-link link setup. More than likely with RCP's 4-link Mount Conversion Plates front and rear on the Axial driveshafts.
The stainless steel links have been seriously kicking my ass. I have decided that working with Stainless Steel is not for the posers in the group. I have broke two taps so far attempting to thread the holes on the 1/4" links. The problem is that even when correctly lubricated, the cheap ass Home Depot Kobalt taps I am using, just will not hold up even when I am patiently taking my time. This of course requires taking the time to very carefully extract the tap or in both cases completely starting over with that link. What I finally decided on was using the lathe to drill the holes for precision. I first drill 12mm deep holes with the bit supplied with the tap, then following up with an only 7mm deep cut with a larger bit. This allows some fine threading on the larger hole and full threading deeper in the hole and so far no more tap breakage. Thread locking a grub screw in place with this solution results in a a permanent stub to attach the Emaxx links ends to. Since the chassis is longer I decided on 65mm long link shafts which end up around 90mm in total length after the link ends are screwed on. Hopefully I will be able to spend some quite time getting the lower links all done tomorrow. If I can get that done, I can figure out where the tansmission will go, get the holes cut for the driveshafts to pass though the chassis, and start figuring out the upper links.
WORK DAY 10
Finally starting to look like something. The front hood of the chassis had to be bent upward to allow servo clearance and improved shock placement. I now have my Tekin RS Sensored Brushless system ready to install and my ProLine Epic Beadlocks and Switch tires.
WORK DAY 11
Life happened and I didn't get much done this week on the project however I did get the rear hand made aluminum upper rear links done and they worked out perfectly. In none articulated position they should provide the rear shocks a little rock deflection protection.
WORK DAY 12
Finally got the front links done. As with any custom project nothing is identical and the front and rear links are just a little different in length due to the clearance and bent angle.
WORK DAY 13
Of course an Axial transmission would have made things easy and even comp worthy by simply screwing on a DNA dig setup... but with a tons of custom parts, I thought I should do something never done before for a dig setup. After somehow accidentally messing up an 1/8th buggy's brakes after a disassembly, I stumbled on an idea worth pursuing. The thought was what if you didn't have a solid center diff, but a regular diff with very heavy oil in the center diff it might work well automatically cycling between locked and neutral. The kicker is that you could then independently brake the front and rear. This would provide front and rear dig and could provide front to rear diff'ing that can shift traction where needed. With a proportional third channel you can feather the front or rear brakes as needed to shift traction from front to rear or vise versa.
After much meditation, and head scratching I decided on once last and final use for the infamous Ultra-Pede. Yes this is the transmission that started Stampede Project.com and powered my first Stampede. Now heavily worn, this transmission case was either destined for the trash can or in need of some serious overhauling and that's just what it got. All new VXL/Slash metal gears and new bearings with the diff backed with super stiff grease. The case itself was bobbed, chopped, Dremeled, and smoothed to fit inside the chassis. For brake rotor mounts I worked up a set of yoke extensions on my Proxxon mini-mill and mini-lathe (I am thinking it would be tough to live without them). These extensions mount up in the typical Traxxas yoke fashion but add a 1" extension and milled insets that lock the rotors onto the extensions. All that is left is to figure out how the brake pads will mount up and will be actuated. Hopefully all this work nets something interesting otherwise I will be disapointed that a couple weeks of interupted work would have been beter served with just installing a stock Axial transmission and being done with it.
Due to the big Tekin brushless power output, big beefy EMaxx driveshafts where used which will hopefully prevent my typical and continual breakage and replacement of stock Axial driveshafts. Having used the Tekin Sensored 21T system before in a crawler, I knew top end needed a little bump for this rock racer so gearing was bumped up'ed to a 31T Pinion and a 69T spur.
With a build like this you could go with a classic ESC like the Tekin Rebel 2, but the Tekin Brushless system provides incredible power and control.
Days 14-21
It's been a long time. This chassis has been sitting in front of me on my bench. I have probably moved it over a hundred times since my last post... this week I decided it was time to finish it up, but I think I still have a long road ahead. The more details I add to this the more I see that I need to add.
The finish and bits of slag were annoying me, so I stripped the chassis, spent two nights re-grinding the entire chassis and re-priming and re-painting the entire chassis.
A night in front of the TV attempting to catch up on the last couple seasons of 24, were spent swapping out the ProLine Epic Slash beadlocks for Axial RTR beadlocks with optional red anodized rings and hand fitting all the 1/8" thick lexan body panels.
I really wanted to use my old Pede tranny, but that ratty old tranny just didn't look right and I picked up a new Axial tranny and mounted the Tekin 21T Sensored brushless motor. The spur was swapped to a 69T gear and the pinion was upgraded to a huge 31T piece to increase the speed for more racer and less crawler.
I scored some Lincoln Electric Motorsports decals that worked perfect and looked awesome. I need to finish swapping out all the misc. screws for all 3mm round head machine screws with matching all black lock nuts and washers. I still have a few pivot points that needs to spacers.
Day 22
Tried some of FLM (Fast Lane Machine's) new AX10 steel driveshafts and they look so much more scale than the MIP units. Granted the MIP offer about three time the mass of the FLM units, but the FLM driveshaft look the part and apprear to offer equal durability.
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Sources: Lincoln Electric - www.LincolnElectric.com
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