RC 4x4 models (EN)
WLtoys A979 off-road
2016-12-18: WLtoys Vortex-A949 off-road

I had this RC toy lying on my table for several months, I was using it just as an unusual cargo for my Tatra 130 and for doing some slow and safe driving on our RC shows .
For a real off-road trip the car was waiting to have some dirt protection added to the chassis. At first, I thought I'd 3D print some fenders, but this turned out to be unnecessarily complex and possibly brittle. A friend of mine pointed out a simple solution – use a suitable polyethylene bottle :) . So I did and the dirt protection was ready within an hour and finally, we could have taken this car for an off-road trip. Since there is winter knocking on the door, the ground is already frozen and "Father Frost" has conjured up beautifully white ice spikes overnight – so enjoy the frozen scenery in this short video :) .
During filming we took a few photos. The first ones were shot at the start (Vortex A949 still very clean :) )
Cooling of the electric motor was not necessary this time, the ambient temperature was below 0°C, the motor was cold all the time (and so were my fingers :) ). In the middle of the trail we took this photo, just before jumping into almost frozen mud bath!
Returned safely home...
Having experience with the A979 , I was expecting, that filming this "cruise missile" will be more pain than pleasure again. Unfortunately yes, the car is almost uncotrollable even at moderate speeds. Moreover, with the standard light battery my car behaved mostly unpredictably, any piece of rock could have thrown it off ballance.
As you've seen in my previous post, I've 3D printed holders for a huge NiMH 6cell battery. I'm aware, that such a great added mass really eliminates some of the crazy stunts you guys are doing with this tiny chassis, but I was primarily concerned about long endurance for video shooting.
With the huge added mass, the car is much more consistent at higher speeds – once you speed up, gained higher momentum helps the car to somewhat "ignore" the looseness of imprecisely manufactured steering and suspension. Interestingly, making a hard turn on dry tarmac can even cause the car to flip over.
Sadly, even on flat tarmac, the A949 behaves much worse than the A979 . Even lifting off the throttle makes the car turn! At walk speed, the driver still must perform steering corrections all the time. The huge looseness of imprecisely manufactured steering and suspension are the cause...
The steering has a big gap in the center (before the servo moves and pushes the joints into their holes) and also the ESC seems to have a lag responding to drivers commands. I'll try to solve the joints' looseness somehow to see if it helps.
Still, the small Vortex A949 toy has gained a bit of my respect. Even though the car has even lower ground clearance than the A979 , it managed to make its way throughout the frozen course I prepared and also bravely performed all the stunts in the video. Most of them were shot more than five times before the right drive-through was achieved.
So one one side, my battery upgrade kit helped the car to sit better on the ground (i.e. be less nervous). As expected, the car's endurance was improved greatly and enabled us to records some interesting video sequences off-road. But again, when the ambient temperatures are higher, the driver must be careful and check electric motor's temperature regularly and make longer stops to cool it down.
Moreover, my flexible fenders around the wheels prevented some of the dirt and water getting directly onto the electronics, motor and gears, but some more protection will be required at the sides of the chassis. The A979's solution was better.
The fenders brought one more interesting improvement I didn't expect – they prevent the lexan bodywork from moving too much on the chassis. The bodywork then looks then more like an integral part of the car (i.e. more realistic).
Warning : since the NiMH battery is much heavier than the original one, the driver has to be careful with long jumps. The chassis isn't really designed for such weight and some of the long jumps with hard landings seen on other youtube videos could be the last ones for this heavier configuration. So far so good, the car made it home safely, we have driven carefully.

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