I was cleaning my electronics bench yesterday and realized I probably had enough spare parts from my other R/C ventures to gut and rebuild the Camaro with more modern parts. Sure, the parts probably cost more than the car did, but I already had them so why not?
The first order of business was assessing whether the existing mechanisms in the car are serviceable at all. After removing the 13 required screws to get the body off the chassis, we get a good view of the inside:
The brushed motor / gear-differential assembly (right) are probably either usable as-is or not usable at all, so I decide to keep them intact and try just driving them with a brushed motor speed controller.
The receiver / control combination circuitboard in the center looks surprisingly antique for something from the mid-2000s. (close-up) It's a totally analog 27 MHz radio receiver circuit, apparently made by the toy division of Huawei. It's all thru-hole components and a couple of relays. Honestly, it's shockingly reminiscent of the circuitboards that were in my childhood toys in the 1980s. It was probably designed in that era. Yeah. That has to go.
But what of that "steering" mechanism? This car was fast and fun as it was originally built, but one thing I always hated about it was that the controls weren't proportional. It had about two speeds, and the steering had three positions: Hard left, center, hard right.
Taking apart the steering mechanism we see why:
So the steering mechanism is a geared brushed motor connected to a set of contactors that close when the steering is in the "R" or "L" position. It's like a motorized switch for selecting between "L" and "R".
The underside of the mechanism mates with the steering crossbar with a 5mm peg:
I momentarily consider removing and re-using that disc, but decide that just putting a similar sized plastic peg on the end of a standard servo arm is probably easier.
Here's the resulting chassis steering mechanism minus the legacy control parts:
It looks thankfully simple and straightforward. I need to fabricate a mount to hold a standard servo in a position where the arm can actuate that steering crossbar. So, I measure and design a similar shaped peg for a servo arm and then a mounting bracket it suspend it from those two "towers" where the old, bulkier system used to be. (Part designs are here: http://www.thingiverse.com/thing:1025747)
Servo with servo arm & fabricated peg and 3D-printed mounting adapter:
New steering mechanism mounted in the chassis:
Here's a video of a function test. It works surprisingly well for a first attempt!!
I used the receiver from a Hobbyking GT-2 TX/RX combo, and a Hobbyking X-Car 45A Brushed Motor ESC as the motor driver. They were straightforward to install. I replaced the battery connector with an XT-60 since I have lots of XT-60 equipped LiPo batteries already.
Here's a chassis / electronics "before/after" combo:
The original system ran on a 9.6V NiCad battery. So we decide that either a 2S Lipo battery for "medium speed" or a 3S Lipo battery for "Turbo Speed" will probably work.
Sure enough, with 3S it's fast as lightening and can drift, spin-out, and do donuts. I don't have any great videos of it driving yet, as Miles isn't terribly skilled at either driving or videography, and I can't do both at the same time. I'll make a video with my GoPro and post it soon. In the mean time, here's a basic video (with a 3S 1300 mAh battery) to show that the conversion worked. (Yes, he stopped just prior to the wall. Whew!)
It works great, and it's fun to drive! Here's a complete parts list:
"Donor Car": Jada Toys 2006 Camaro Radio Control Car
Steering knuckle & Micro Servo Mounting Adapter
HobbyKing X-Car 45A Brushed ESC
HobbyKing HK-GT2 TX/RX combo
Turnigy TGY-50090M Analog Metal Gear Servo