MANIC FREAK - Schumacher Racing

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Above: 4WD transmission layout clearly visible (air filter removed for clarity) shows power being carried forward by the drive belt and pullies Above: Adjustable servo saver and front disc brake assemblies Finally, the chassis rolls on ‘super grip’ tyres and huge chrome-effect wheels, which are attached by 17 mm hex nuts. Using 17 mm hubs opens up a world of choice when it comes to future wheel and tyre options. Unfortunately Schumacher do not include a wheel nut wrench, which is why it is a good idea to consider buying the very reasonably priced Nitro Starter Kit, which resolves this problem and also gives you a box spanner, fuel bottle, glow starter (although it’s far better to use two glow sticks to start the Manic!) and a couple of crosshead and flat blade screwdrivers. tRAnSMISSIOn Drive is transmitted from the twin shoe clutch (how many times have I said ‘twin’) to a 24 DP spur gear. The clutch is rather like the popular MIP hop up, but be careful when removing the clutch bell as it runs on floating needle rollers with no cage to keep them together. The spur gear layshaft is the first part of a triple metal gear reduction box with a ball differential whose unequal length outdrives transmit drive to the rear wheels via a pair of really chunky telescopic driveshafts. On the outer end of the spur gear top layshaft a pulley and toothed belt drive connects to the input shaft for the front gearbox, which follows the same method of reduction and drive to the front wheels, as it does at the rear. The chunky square section telescopic driveshafts feature CV joint stub axles, each of which attaches to the aforementioned 17 mm hex hub. The entire transmission and wheel hubs are fully ball raced with sealed bearings. Above: Chunky arms and driveshafts are matched by the solid chassis plate which looks bump box compatible, but isn’t RRCi FEAtuRE Above: Digital 27 MHz ‘Response’ radio transmitter offers all the essential features, and a few more besides Working on the Manic is a breeze. The front and rear transmission assemblies can be split from the chassis with the removal of just four or five screws and popping a few ball joints. It couldn’t be easier. The same goes for drive belt replacement, which is even easier. Remove one of the belt pulleys and the rear radio tray post and you can swap the belt in just a few seconds. tWO hEADS BEttER thAn OnE? And so we arrive at perhaps the most interesting aspect of the Manic! With a total displacement of 6 cc it is in fact a pair of 3 cc (.18 ci) engines that have been paired up with operationally linked crankshafts. This latter item is crucial to the smooth running of the engine, and is why the Manic power plant should function without any of the problems that can afflict other twin-engine applications. The engines always drive each other reducing the risk of a low tick-over flame out, and allowing a taller overall gear ratio than either could pull alone. The rearward of the two engines is the one that is connected directly to the transmission and the first thing mounted on the external crankshaft is a toothed belt drive pulley, followed by the conventional flywheel, clutch and clutch bell assembly. A special flywheel on the forward engine also accommodates the same type pulley, and it is the toothed belt drive between the two engines that keeps everything synchronised. Now that you know what literally makes this twin-engine ‘tick’ let’s look 12/09 WWW.RADIORACECAR.COM 27
SChuMAChER 1:8 4WD tWIn-EngInE ‘MAnIC’ MOnStER Above: Starter unit is built onto rear engine crank. Two into one exhaust system with rear facing single stinger. Admit it…you want one! Above: Big end alignment after fitting synchro jigs, means two power pulses per revolution Right: Synchro drive is normally shrouded by two-piece protective cover. Tightening the drive locknut after synchronising the engines at the assembly in more detail. As you can see the engines sit on a central mounting plate and a pair of engine posts at the front and rear. So after removing six screws, the whole lump comes out as a single unit. That eyecatching heat sink head is a single piece of billet-machined alloy, and attaches to the two engines in the normal way with four bolts apiece. The next interesting feature is the purple anodised carburettor inlet manifold. This item provides for the simplicity and reliability of a single carburettor feeding both engines. Access to the top end mixture screw is nice and easy as this sits atop the carburettor pointing skywards. The bottom end screw is forward facing and can be adjusted with a flat blade driver. Adjusting the idle screw is slightly more awkward as it is at an angle close to the heat sink head. The engine breathes through a twin (there’s that word again) stage air filter which you have to lube and fit yourself before first firing it up. The engine exhausts exit through a pair of unequal length manifolds and a cylindrical transverse silencer can with a single rubber stinger pipe pointing out of the back. The Manic kit comes with a Rotostart drill attachment, which you can use with any suitable cordless drill, or if you prefer, the optional Schumacher Rotostart electric starter. As I mentioned earlier, remember that you will need two glow starters to get the Manic’s twin cylinders fired up, preferably a long reach Core Glow start (CR046) to clear the truck cab and reach the engine below, while the rear engine can be reached by a regular short glow stick like that included in the Nitro Starter set (G852), as the load deck sits only just above the heat sink. So that is what makes the Manic go, but what about stopping it? Thankfully the answer is that both front and rear gearboxes are braked separately, so with no centre diff the two brakes work together and pull the truck down from extreme speeds without a fuss, even with just a 4-cell receiver pack. 28 WWW.RADIORACECAR.COM 12/09 Above: Optional U3544 synchro assembly jigs are used to set the cranks exactly 180 degrees apart for best power delivery Left: Twin shoe clutch and loose needle rollers within the bell. Be sure to keep them lubricated EngInE AutOPSy If you are familiar with Schumacher products, you will also know about their liking for Torx fasteners and whilst you get a basic Allen and Torx key set included, it’s worth buying yourself a Torx driver and bit set, before starting any work on the Manic, but bear in mind that Schumacher have their own T10 Torx driver (HW008) though it’s not always included in the kits. The easiest way to remove the engine is complete with its engine mount, which, as I mentioned earlier, involves removing the six chassis screws. The exhaust can is stabilised with a mounting wire retained by a setscrew, but we found it necessary to remove the complete mounting wire because the exhaust fouled on the rear brake pivot, preventing its removal. On closer inspection we found that on our Manic we could remove about 5 mm off the mounting wire with a Dremel, which would then give sufficient room to remove the engine and exhaust quicker and easier. Obviously you also have to disconnect the throttle return spring and throttle linkage and fuel pipe connections and in about one minute, the whole lot is on the bench. If you wish to ‘split’ the engine, you can now see that it’s a case of removing the centre bracket, which locates on the two crankcases at the base, and the one-piece heat sink head. The head bolts were VERY tight on our review Manic, so use a good quality hex driver. Slacken the two pinch bolt nuts that clamp the one-piece inlet manifold and lift off the inlet manifold and single carburettor assembly. You can now remove the two-piece synchro drive cover, which exposes the synchro drive belt. Next, cut the tie wrap retaining the forward exhaust manifold (the twin manifolds and exhaust can are a one-piece item) and pull the forward pipe off the manifold flange. You can now just slip the drive belt off and you have successfully split the engine. To access just the synchro drive belt, the bottom half of the cover slips off easily enough (mind you don’t lose the little strengthening plate that slots in the centre), but to remove
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MANIC FREAK - Schumacher Racing

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