2013 - Losi Mini Desert Truck
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(originally posted on UltimateRC.com on 2013-11-14)
It is done.
This is my first hobby-grade RC, and after three months of near-constant tinkering (and an embarrassing amount of money spent on parts), I have finally upgraded and/or modified all of the parts I wanted to. All of the remaining stock parts are there because I decided they were good enough and didn't need upgrading.
Last night I replaced the last part I intended to replace: the stock steering servo with a Hitec HS-5055MG metal-gear servo. And tonight's tinkering finally fixed the last lingering annoyance about the truck's handling: 1 ounce (28g) of lead ballast mounted to the front axle, to counteract the truck's tendency to ignore steering inputs under hard acceleration, and bounce like a motorboat when driving through grass.
The shocks were replaced with the Losi aluminum shock kit for the Mini-T, with the mid-stiffness damping pistons installed front and rear. The front and rear springs both came from the Losi rear-spring kit, with the stiffest blue springs in the rear and the mid-stiffness green springs in the front. The front suspension linkages have been completely rebuilt with captured-ball joints, so they don't pop off in a crash. They hold so well that I actually snapped a turnbuckle a few weeks ago, but that turnbuckle had already been bent a couple of times, so its days were numbered anyway. The steering bellcranks have also been replaced, with an aluminum-and-graphite kit from GPM, for less flex and better precision.
The drivetrain has been completely replaced, with a Tacon 5200KV brushless motor, an Associated RC18 13-tooth hardened-steel pinion, a Losi dual-disc slipper clutch, a Losi ball diff, a Losi hardened-steel idler gear from the metal-gear-diff kit, Losi CV axles, a GPM aluminum gearbox casing and motor-mount plate, a customized slipper cover that fits as well as the original but provides clearance for the dual-disc slipper clutch, and Boca Yellow Seal ceramic bearings on every single rotating part.
The electronics have also been completely replaced, with all-Losi parts (why, I dunno, just because): an Xcelorin brushless ESC with a matching programming card tucked in the toolbox, a 2.4GHz Spektrum-compatible 3-channel receiver, and a Losi running-light kit that's been heavily customized to use much better LEDs than stock. Power is supplied by Turnigy 2S LiPo packs.
Since the chassis has a tendency to crack over time where the front bulkhead attaches, I installed a 3Racing graphite reinforcement brace over the top of the bellcrank housing. Also, the front and rear hubs and suspension pivot blocks have been replaced with aluminum units from GPM, so the only non-metal parts in the suspension are the lower arms, to reduce the number of spare parts I need to keep on-hand.
And lastly, the stock wheels and tires were replaced with Losi Mini Smasher tires mounted on RPM "Spider" 8-spoke rims. They get much better traction in grass than the stock desert tires ever did, and based on my testing of all the Losi mini tires available, the Mini Smashers are the best for any terrain except 100% on-road. The wheels are held in-place with flanged locknuts from TheToyz; the flanges help keep the wheels aligned properly much better than the stock locknuts did.
Modifications made since the original post:
- I found a better set of wheel nuts from Associated, which have wide-enough flanges to cover the entire front wheel bearings, so there is no visual difference between the rear wheels and front wheels anymore.
- I replaced the Losi-rebranded receiver with the same model of Spektrum receiver (for consticency with my other vehicles).
- I replaced the Xcelorin ESC with a Turnigy Trackstar ESC (a rebrand of the Toro Brushless Micro ESC, available for purchase without a matching motor); the Trackstar ESC doesn't cog the motor at low speed the way the Xcelorin ESC did.
- I replaced the 5200KV motor with a 6200KV motor. The vehicle is now a speed demon, relative to its size, yet it's easy to control with all the mods and tuning I've done.
- The Losi ball diff required more service than I was happy with, so I replaced it with a MIP ball diff. After having both brands of diffs in my hands, I think the MIP ball diff is better-designed.
- The Losi dual-disc slipper clutch works great, but the spring retaining washer is made of plastic, and it was slowly deforming over time, so I replaced it with a metal washer. The hole in the metal washer was too large, so I added a cone-shaped spacer from a Dubro captured-ball link to help center the metal washer. It hasn't lost its setting in months.
Modifications made since the original post:
- After running my ECX Smash for a while, I concluded the Mini-T platform really does benefit from having larger "monster truck" tires, so I mounted-up a set of Associated Mini Rival tires for my Mini Desert Truck. I'd like something with a more aggressive tread pattern, but the extra tire height helps in grass regardless of tread pattern, and the Mini Rival tires are made from better rubber than the stock Mini-T tires.
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