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To those uninitiated in the world of R/C, I thought I'd put up something a bit different to the usual. The R/C car I will be working on is a 1/8th scaled, 4wd nitro powered monster truck. It wheelies, stoppies, jumps and rips the fuck out of dirt. They really are great fun, but when you buy them new they unfortunately have a habit of breaking. The only way to stop it happening is to fix things as they break so that it doesn't happen again.
Anywho, this savage was left outside for about 6 months, got nicely rained on and was just left to turn to shit. So the engine no longer starts, and a few bits have rusted to the point where I need to replace them. I'll walk you through the stripdown and rebuild, including a replacement engine. Just to have a bit of fun and show you how these little things tick.
Here she is, filthy and rusty as fuck. It's actually quite large in person, bigger than it looks here.
You can see the clutch bell rusted in this shot, and the car just in a general state of disrepair. The engine is in really bad shape internally, crankshaft has a coating of surface rust and the bearings and grinding from rust.
Here you can see the bottom of the 3 speed transmission, the twin disc brakes and the drive shafts (we call them dogbones). The bones and cups are nicely rusted so I'll have to sort that out. The issue with these cars is the brake is applied at the gearbox rather than the wheel, putting a shitload of stress on the diffs and drivetrain. This particular model has extra strong diffs but the older ones had plastic cases and only two spider gears rather than four. They had a habit of breaking and it was common practice to upgrade them before ever turning the thing on.
Tyres, fuel tank and engine out.
You can see just how badly it needs a strip and thorough look over.
Gearbox and engine plate out. The big plastic gear is called a spur gear. It is ok but a little worse for wear so I'll replace that, they're only a couple of bucks each. Some people replace these with a metal item, rather stupidly too. It is far cheap and easier to have one of these break than have your tranny or drivetrain or clutchbell break instead. It's good to know you have a weak point. There is an integrated slipper clutch, of which you can see the spring, they really don't work very well on this scale.
The gearbox in this photo is a auto 3 speed. The savage comes stock with an auto 2 speed that I plan to reinstall during this rebuild. The 3 speed gives sweet fuck all gain for a fucking lot of trouble, it's very hard to setup right. I did have the option to just buy the upgrade parts and upgrade my 2 speed box, but I bought an entire new box instead so that I could do a direct swap if needed. Glad I did, and can keep the 3 speed in case I blow the 2 speed (unlikely).
Slowly coming apart, you can see the dogbones out and one side of the TVP chassis out. The thing that makes these truck special is their Twin Vertical Plate chassis. It makes them exceptionally good offroad and through jumps, although pretty shit at racing. You buy a savage to bash around and have fun, not to race. All the other monster trucks simply have a belly style chassis thats also quite a bit heavier.
You can see just how rusted the dogbones are here. I was going to order new ones but due to a stocking issue ended up just giving them a clean with sandpaper. They will rust again and I can replace them later.
Another example of the rust in the drive cups, both cups will be replaced.
This is the rear shock tower, it's really filthy but after having a closer look at the shocks, diff and drivetrain it is all in perfect nick. I'm not going to do anything with it, because in a reasonable amount of time the shocks and diff will probably need a rebuild so i can pull it right apart then to clean. At that time I will also change the wheel bearings. The front shock/steering tower is in the same condition, so both will be bolted back on as is and filthy.
Here is the front steering/shock tower and radio box. You can see the digital high torque steering servo I've put in, this truck steers really really well now. Hitec make good servo's. Really should strip and clean it but too much to do already. Will keep to my rebuild later plan.
Here is the engine with the head, sleeve, piston and conrod out. The piston, sleeve and conrod look reasonably good but the bottom end of the engine is in really poor shape. I did have the option to rebuild but decided to just put a new donk in. At the current exchange rate the decision was easy, $120 for a new one. Then I can break her in really well and look after her properly. The reason this one has rusted is because nitro fuel is hygroscopic and attracts water. Without putting after run oil in your engine at the end of the day, the water hangs around and rusts it pretty quickly. Pure laziness on my part.
New donk. This is an axial .28 (4.6cc) engine. It pushes roughly 3hp and revs to about 37 000 rpm. It is an extremely simple engine. It uses a glow plug like a diesel, so there's no ignition system and it is a two stroke so there's no valvetrain. Perfectly simple and ideal for use in such a small car. This is the spec 2s version, which revs slightly higher than the spec 1s but isn't substantially better. The spec 1s is what HPI rebadge as their stock engine, so that purple headed thing is the 1s version of this.
Flywheel on, you can see the clutch components sitting on the piece of paper ready to go on. The carb is configured completely wrong for the layout of the car so I need to pull it off and twist all the nobs and shit around.
Here we have the original 2 speed tranny with a new spur gear and drive cups on. I've transplanted the brake pads and discs as they were fine. She's clean and ready to go back in.
Here's the donk with the carby reconfigured, the 3 shoe centrifugal clutch and clutchbell installed. She's ready for an exhaust and air filter, and to go back in.
Exhaust and air filter on. I'm really liking the green heatsink.
Radio/servo box and front steering/shock tower back together. I had it partially dissasembled to check all the steering linkages and make sure nothing needed replacing.
Chassis and engine plate mocked up so I can figure out the order of bits to go back in, it's an artform. These things are a confusing cunt of a thing to strip and rebuild because of the TVP, you get the hang of it after a while though. Also gay because everything has to come right apart to do anything. I did take a few PSB'ers suggestion of using sandwhich bags to label and store various screws, has made the rebuild infinitely easier.
You can see I've given all the metal a really thorough clean. The engine plate in particular needs to be clean as it is far easier to set the spur gear mesh without sand and shit jammed between itself and the engine mount.
Tranny in.
Donk in, looking good so far.
Front shock tower in, few screws in to hold shit together while I get things assembled.
All chassis screws in now. Throttle and brake linkages set up.
I've put in a fuel filter as the fuel tank gets filthy as fuck thrashing on dirt. The tank does have an inbuilt one but i'd rather be safe than have to replace the engine again, going to take really good care of this one. I'm digging the purple and green anodized scheme, might have to order some mods to extend it throughout the truck.
Fuel lines swapped over for clear ones, makes it easier to see where the fuel is when priming the carby. My truck did come with a roto start which basically uses a drill like device to spin the engine to start it. I've decided to not install it and keep with the pull starter that came with the axial engine. Can always whack it in later if need be, but it's too much shit to carry around on field. Sick of having so much shit to charge too.
You can see the cleaned up dogbones, and new drive cups. Everything looking far better.
Looking like a truck again.
Mmmmmm.
So yea, time to break in the new engine and have some fun
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Originally Posted by Retro 
Which type of chassis is on it? 
Percute et Percute Velociter
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