Over the holiday break I stayed home. Instead of going away I launched into a much needed complete 4WD strip- down and rebuild. The old Rangie needed attention. Body off, motor and gearbox out. It took ages. Wheels off, man those big t yres take up some room when stacked! Suspension apart, all joints checked, overhauled, lubed. Both diffs overhauled and adjusted. CVs too, stripped and cleaned. Drive-shafts checked. Shockies opened and valving modified. Hubs cleaned up, new wheel-bearings all round. Power steering upgraded. Motor and gearbox replaced. That was a mission, choosing the best options. Ratios too high or too low? Balancing power against economy, weight and size to fit available space. Optimising cooling. Modifying wiring and connectors. Many hours were spent on my 3D CAD system matching up dimensions, working out mods. In the end much of it worked out easier than expected. Ratios are spot on, power and control are excellent. The power steering is perfect. There are no signs of overheating. Nothing leaks, apart from some momentary smoke and a blown fuse. Low speed throttle control when rock-crawling is wonderful and the spring and shockie changes worked. With wonderful approach and departure angles and belly clearance it seldom hangs up. It’ll climb a near vertical face until it ’s about to fall over backwards. No diff- locks yet so an excessive cross-axle will stop it. It’s a real treat having it mobile again though. A few mods still on the list – a winch for starters. That will require an upgrade to the radio control from t wo channels to four to work the winch. Ah, there’s always more to wish for. Good thing it ’s only a model! Some readers may remember I wrote about this model Rangie in the mag ( 2001) when first built. It began as a box of bits from a model shop. A Tamiya go-fast 4WD racing buggy and some extra parts. I shortened the chassis, fit ted monster truck wheels and t yres then made a reduction gearbox to fit a smaller motor. The object was to make it a good rock- crawler. The original racer went very fast, had a limited three- step speed control and a battery charge was gone in a couple of minutes. Speed control was via vulnerable and inefficient resistors that got very hot and tended to burn out. My original mods had kept that controller but was flat out at walking pace and had reasonable low speed control. Also the original steering servo struggled to steer the bigger wheels in rough terrain ( much like some full- size 4WDs!). One of the upgrades was to a cheap ESC ( Electronic Speed Control). These are vastly more efficient as they don’t waste power into resistors and have stepless control from zero to flat out. Excellent at very low speeds. The steering servo was replaced with a high torque variant, of which many are available. It seems undefeatable so far. The main reason behind a revisit of the motor-gearbox was ‘realism’. The original high-power motor fitted sideways into the chassis just ahead of the rear axle. There wasn’t much room to fit a different motor and a reduction box so I’d made a right-angled worm drive box with the smaller motor vertically above it. The ratio and motor where ideal – it had enough power and a battery charge would last an hour or so. I didn’t like that when powered on or off it would lurch forward or stop instantly due to the worm drive. I’d always wanted to change it to spur gears to remove the lurch. This time I looked at many ways to repower it and spent ages trying to adapt a t wospeed electric screwdriver motor to fit. They have very compact three stage epicyclic reductions of about the right ratios and would have allowed the possibility to later give a Hi- Lo ratio switch via radio. This, however, entailed a quite complex gearbox build with bevel gears, new driveshafts and bearings, etc, and lots of machining and fabrication. I did make a test setup to check ratios – Lo was excellent but Hi too slow. Then I discovered some small industrial motor- gearbox units from China. Bought one, tested it, wrong ratio. Bought another ( NZ$ 10!) and it ’s perfect. It needed only a couple of basic adaptors and works well with the ESC. Motor is sweet and runs cool. So, a happy rebuild, mostly done at my desk and without having to stress my back or scrabble around beneath the vehicle changing oils or bushes!
Scaled down Rangie provides hours of fun.