Rollin’ In My Sixtyfour
AN EXCLUSIVE IN-DEPTH FIRST LOOK AT REDCAT’S INNOVATIVE RC LOWRIDER
An Exclusive In-depth First Look At Redcat’s Innovative RC Lowrider
Editor’s Note: Redcat gives us an exclusive in-depth first look at their groundbreaking release, the Sixtyfour. The exciting Sixty-four is an intricately detailed, fully-functional hopping, ready to run RC replica of a 1964 Impala SS Lowrider. Matt Jackson, Director of Engineering for Redcat, shares an inside development view of this incredible RC vehicle in his own words. It’s a truly fascinating and informative read.
Back in 2016, the owner of Redcat discovered the work that custom builder Jeroen de Vries, better known as “Jevries”, had been doing on making custom one-off RC lowriders, and started to believe that there was probably a market for such vehicles. As he grew more convinced that the market was there—and a fairly large one—he set a plan in motion to develop a commercially viable lowrider. Redcat entered into a consulting agreement with Jevries, purchased one of his custom creations, and started looking for engineers.
At the time, Redcat had not built a car from the ground up. The Everest Gen7 was starting to be developed in partnership with influential members of the Redcat Everest 10 community, but most vehicles that Redcat
had brought to market were rebranded models developed by factory partners in China.
This is where I came in. In early 2017, Redcat contacted me through a mutual friend, stating interest in starting an engineering department at Redcat to lead new product development. At the time, I was employed at Local Motors, where I was leading the development of the Olli, a self-driving, mostly 3D printed, 8 passenger shuttle bus. The attraction of starting my own department, and being paid to indulge my RC hobby, was too much to pass up.
In April of 2017, I started at Redcat, and brought along with me Alaric Egli, another mechanical engineer who had lots of RC experience. On our very first day, we were presented with the custom model Redcat had bought from Jevries, and given the goal of figuring out how to build something similar that could be mass-produced. The Jevries model was a masterwork of scratch building; it had hand cut aluminum extrusions for the frame, custom brass suspension links and steering rack, delicate balance, and a complicated electronics system to control the suspension actuation.
HOPPING MOTION
Jevries’ method for creating the hopping motion was a relay-controlled motor, which when activated, would spin a pulley that would wind up a string, which passed through a series of eyelets and eventually would yank downwards on the strut tower brace, forcing the front suspension down very quickly. Another string was tensioned with a spring to pull the strut tower back up when the hopping motor was turned off.
We learned quite a lot from the Jevries model. We learned that the weight balance was extremely important to being able to successfully and reliably hop; having the weight of the driving force in the hopping mechanism as far back in the car as possible was essential. We also learned that if you wanted to mass produce something to hop reliably, using strings and tension springs was probably not the way to go, as springs stretch out and strings eventually break after an indeterminate number of hops.
So early on in our time at Redcat, Alaric designed the bell crank mechanism to actuate the front suspension, which is now in production on the Sixtyfour (and patent pending), and we set about testing various methods of pulling on the main crank to cause the car to hop. We tested multiple methods of winding a string like Jevries
did, but quickly found that strings are too unreliable for a consumer product.
We moved on to testing solenoids, but found that the way solenoid performance numbers are reported are somewhat misleading regarding how much instantaneous pulling force they actually generate. Starting to get frustrated, we decided to go with the simplest solution (usually the best idea), and experiment with high speed servos. We had previously avoided the use of a servo, as the amount of force and speed of motion transmitted to the bell crank changes depending on the position of the servo horn.
It turned out that servos were 100% the best way to go, as the servo provides fine adjustment for the ride height of the front end, and you can tune both the speed and force of the movement by adjusting the length of the servo horn and the pushrod. Armed with this newfound resolve to use a servo as our hopping solution, we started soliciting all the usual suspects in the servo game for their highest speed, most powerful servos available. As soon as the test subjects came in, we set to work evaluating each one. Seriously, we’ve got a really big box full of servos that were candidates, and we certainly know which servo providers we can trust now in terms of performance numbers!
While Alaric was working on the mechanics of how the hopper would work, I set about working on the radio design. Obviously, there would be some challenges to using a standard pistol grip style radio, as you need to be able to control the suspension at the same time that you are handling the throttle and steering. Initial designs included such outlandish ideas as a completely separate radio to handle just the “hydraulics” that you could pass to a friend, game controller style radios, even a custom modified pistol grip that would allow you to handle throttle and steering with one hand. In the end, we decided that the best course of action was to highly modify an existing 6-channel aircraft radio. Flysky worked closely with us to develop the LR6X radio specifically to meet the needs of the Sixtyfour.
Meanwhile, business as usual was
continuing at Redcat, and in early autumn 2017 the Everest Gen7 was released. The Gen7 release was hugely successful for Redcat, and almost immediately the main focus of the engineering department was put onto the development of the follow-up vehicle, the Gen8. The hopper project (as it was called at the time) was largely viewed as being complete from an engineering standpoint, and a body modeler had been contracted to develop the ‘64 Impala body to fit on our chassis, which was at the time a standard 1/10th scale wheelbase. The original goal of the hopper was to make a vehicle that would accept just about any 1/10-scale body.
Sometime in mid-2018 the first samples of the hopper were delivered to Arizona from the factory. We were excited about the performance of the vehicle, we fell in love with finding new tricks that could be pulled off, and were getting set to approve the sample to go into mass production, but something about the hopper just did not feel right. The owner of Redcat showed the pre-production sample to Jevries. While I think he was pleased with the performance, he was not thrilled with the body.
When trying to make a ‘64 impala, you need to be careful. The design is very iconic, and its many devotees would have been very disappointed with the original body we had produced. On a traditional 1/10th scale wheelbase, the aspect ratio of the car is all wrong— something that is painful to look at for Impala aficionados.
Not really sure what to do
about the future of the project, the owner of Redcat was visiting some high end RC body factories in Asia, and they agreed that the iconic Impala design deserved the most respect we could give it. It was time to start over from scratch! We wound up sending the body factory as many ‘64 body pictures as we could get our hands on, and even used a 3D laser scanner on an extremely accurate and detailed diecast model.
The body factory worked their magic, but found we would still need to make some compromises to create such a detailed body. In order to achieve the correct undercuts, hood and trunk lines and more, we determined we would need a 5-piece body. The result is a super scale body that captures the iconic 1964 Chevrolet
Impala! Once the body factory had arrived at the final shape for the body, the Redcat engineering team was in a different position than when the project had started. Alaric was at this time balancing his efforts between development of the Gen8 Axe Edition and the Wendigo, so I had to take on the continued development of the hopper chassis.
It is important to make distinction that this vehicle was designed around the body. We felt that the body is iconic enough and important enough to the lowrider community that everything became focused around making this a Sixty Four Impala. All concessions to making the chassis easy to fit with other bodies were abandoned; we began to redesign the
chassis around the body, and included many details to resemble the underside of an actual Impala. The chassis was extended to fill in the overhangs front and rear all the way to the bumpers, and chrome exhaust was added to complete the look.
Once the chassis redesign was complete, the molds for the chassis were remade at the factory, and we received our first samples in mid-2019. A new problem surfaced; the servo we had settled on as our production hopping servo got discontinued, and with the increased weight of the vehicle, we were back to square one with regard to servo selection.
We had just recently released the Gen8 Axe edition which featured a Reefs steering servo, so on a visit with Reef
himself in California I let him in on our secret “hopper” project which had a very unique servo requirement. He immediately understood the appeal of the product, and knew what we were going for. I told him the specs for the hopping servo we were aiming for, and he told me “I think I can beat that. I’ll send you something in a few weeks.” Boy did he ever. On our 7.4V system, the servo he provided produces 270 oz. of torque and turns 60 degrees in 0.06 seconds!
Knowing that this vehicle was going to be heavily customized by the RC community, we decided that the power we could provide in our current ESC was not enough. We tested the car with one of the Reefs hopping servos in each of the suspension servo positions. Combined, these 3 servos
have enough power to get all four wheels of the car off the ground!
The issue with that modification was that the power draw was enough to brown out the receiver. At that point we got in touch with our partners at Hobbywing who had just supplied us with the power system in the Gen8 Axe. Hobbywing managed to squeeze a BEC into one of their WP-1040 ESCS that could handle pumping out 5 Amps at 7.4 volts, and just like that our power supply issue was solved. There should now be enough power supplied by the ESC to run almost any accessory someone wants to cram into this car!
The last couple months of 2019 and the first few months of 2020 were spent on reviewing pre-production samples of the various parts of the Sixtyfour. Right as we were gearing up for production, COVID-19 hit the world. Suddenly, instead of traveling to China to work with the engineers on the production floor to hit the desired performance and out of the box quality, we were relegated to staying home and shipping samples back and forth; not the most efficient method for getting a product out the door. As such, it has now taken three and a half years since the development of the Sixtyfour started, but it is finally shipping. The reception to the announcement of the car has been amazing, and I am extremely excited to see what people do with this car that has been such a labor of love for the team here at Redcat.