Electric Conversion of a King Motors (HPI Baja 5B)

Another interesting project for us is the electric conversion of a King Motors KSRC-002. Ours was bought from Heat Hobby of Miami, FL. Out of the box, the only thing that needed to be assembled was the spoiler. Thankfully, we won't be using it. Inspecting the role cage and the transmission shaft we found some rust. This is not really a nice thing to find on your brand new model. Oh well, it will probably get replaced. Since this is an electric conversion, the first thing that I did was hop onto every HPI forum and King Motors discussion that I could find.

Several guys are using huge current setups, 200A or more. That may be necessary, we will see. I do not think they were using as many cells in serial as we intend to. Our plan is to run 9s2p or 9s3p, we also only want to be able to dash. the conversion we are running will be about getting it set up, and then moving toward the longest running build possible. Out of the box, we can see a bunch of things that do not make sense in a racing vehicle. Ok, probably not a race ready device out of the factory.

Why would you use 0.125" (3mm) steel as your chassis? Cars do not use 3mm of steel in many structural places. It can hold up with a person standing on it. One of our first projects will be to replace the chassis with an Aluminum one. This should take out about 2lbs (1kg) without any stress. Another interesting choice, which is clearly about cost is the roll cage mounts that are plastic. It is my opinion that the plastic knuckles are where the cage breaks not the quarter-inch (6mm) steel tubing. Which was also poorly finished and rusted in one of the welded joints. If King Motors reads this, please do some inspection of the parts before they leave the factory.

The fuel tank was pulled out along with the engine. a few bolts and it removed cleanly. Next time, why bother buying a full setup, go roller chassis. Forum after forum said the FM radio that they ship with it sucks. I have to say that we did have some interference on our little test stand. I could see where this would be an issue. So I yanked it out and replaced it with a composite capable 6ch Spektrum unit which we use in our planes. It is a great 2.4GHz DSM-2 radio. There are two-channel versions if you prefer.

The throttle servo and steering servos are crap, but useable. One part that is a bit challenging was the clutch. Not the clutch bell, but the clutch on the drive flywheel. Several places lauded designs that keep it in, noting that the clutch helps reduce the biting nature of the electric motors' torque curve. Anything to keep the wheels hooked up is better. Just make sure that you put the pin in first, othwerise you cannot get it through the hole with the shoe. You will need a piece of wire to go through the eye on the pin and above the retaining plate to keep the pin from falling through the hole. It is not hard to fix, but it is annoying.

The steering servo was replaced with a nice metal-bearing quarter scale unit. Our HB unit is faster, digital and stronger than the factory version. There is no reason not to use digital anymore, I hear that there were some issues in the beginning.

The catch with this that we found. The drive pinion that you need is a 1.5 mod. Yes, 1.5mod, the stock that came with our bell housing is a 17t. I contacted my normal strange parts connection at Impakt/Tekno RC. They are always awesome. They said that they did not have the parts in the scale, and directed me over to Monster RC. This is a reason, that I always go to them first. Customer service is not only helping them on your site, but helping them get what they need. Following their suggestion, I went over to RC Monster. They had the a selection of 1.5 mod gears. I emailed Mike at RC Monster, he responded quickly and said which parts that I needed. Again, great customer service, you can get 1.5 mod gears in a bunch of sizes from 12t-22t. They are cut for 8mm shafts, so pick up the reducers as well. RC Monster shipped my order the same day.