Setting your car up with the radio

Modern RC cars have a huge amount of setup adjustments, and have even got to the point where changing the flexibility of components is seen as a valid setup change.

I call shenanigans. My touring cars have all driven the same after a few tweaks. The smoothness of the rear diff makes more difference to a car than a 0.5mm shim.

The one change that does make a real difference in a world of identikit cars is the transmitter settings. You could spend all day trying to lock the rear end in, or you could simply take a couple of clicks off the steering rate. If the car is too twitchy on turn in, take a little bit of steering expo out.

There is no reason to be afraid – modern TCs can turn far tighter than they would ever need to on a track. A car that flows through the apex is always going to be quicker than one that you are fighting.

This all assumes that your steering is set up with balanced linkages and even throw to full lock on both sides. Just don’t take it too far – 50% steering rates may make the car stable, but it won’t be able to steer around the track. If you car needs less than 80% rates or more than 20% expo to be driveable I’d take a good look at the build or the setup. It might be something as simple as a bent hinge pin or a loose screw that is ruining the handling, don’t assume that putting the car on a Hudy station will solve a build issue!


Futaba 3GR – fingertip steering rates modification

Regular readers will know that my trusty Futaba 3VC transmitter finally gave up the ghost a couple of months ago. I borrowed a wheel radio for a little while, and although it felt good on the big on-road track, the fine control wasn’t there on a smaller off-road track.  So I decided to order the mid-range Futaba 3GR 2.4GHz stick set as a replacement.

The 3GR is 90% as good as a 3VC/3VCS for less than 50% of the price. The 3VCS seems to be out of production anyway. The feel in the hand is very similar, the feel of the sticks is very similar (although you cannot rotate them), but you can tell that the construction is not as robust – although a “less robust” Futaba is still more robust than most other brands! The menu system is very time consuming to use because you can only go through the settings in one direction, but it has all the functions I have ever needed. It would also be nice to change the size of the dual-rate steps as I find 2% too small – you can do this on the top-of-the-range radios.  But these are small concerns.

The one thing I really miss is the ability to change steering rates “on the fly”. The 3GR’s rates adjustment is a rocker switch to the left of the steering stick and it is just too far away for you to use while driving. The 3VC/3VCS has two switches on the shoulder of the transmitter that you can use with your fingertips. So I’ve tried to mimic this.

Most of the time was spent choosing the right kind of switch and finding the right position to fit them – you need to clear the steering gimbals and toggle switch. I chose a pair of microswitch action push-button switches (RS #320-988) with black caps (#103-5782) which have a reassuringly positive feel.

I took the ground from this point on the board (G1). The wire is just cheap equipment wire from the dreaded Maplin that has been in my toolbox for years.

The switches are wired into points S11 and S12 – the other wires go to the original switches, which means that I can still change rates with the standard rocker.

The switches themselves are mounted in the back of the case according to the drilling pattern in the datasheet. The ground is shared between the two, the signal is taken from the middle contact (the momentary on). The switch bodies are lined up with the top edge of the handgrip, about 10mm from the inner edge, and with 15mm between centres.

And this is how it looks from the outside. Works perfectly, and now I can change rates on the fly. You could do the same thing for the ATL on the other side of the radio if you wanted.

Now I have a radio that is 99% as good as the 3VC for less than 50% of the cost, plus a tenner in parts and some elbow grease!