Mike Tulls creations, Vixen V8, StuG

Vixen V8 Engine &

V8 Powered StuG III 1/6th scale model tank

Customer reviews
RC Transmission logo               Vixen logo

By Mike Tull


The Vixen V8 engine is the creation of my friend Mike Tull. I was collaborating in the build of the engine and created the 3D part models and design package. He build the V8 together with the CG2B into a StuG3. The outline V8 engine specifications are:

90 degree V8 configuration.
Flat plane crankshaft.
Water cooled.
Wet (oil filled) sump with splash lubrication
Overhead valves, pushrod operated
Bore 23mm stroke 25mm  10cc (0.61 cu inch)
Swept volume approx 80 cc (4.88 cu inch)
Fuel and ignition system: option 1    Methonol and glowplug, option 2    Gasoline and CDI spark via distributer.
Spark plug or glowplug thread is standard 1/4" x 32 tpi
Normal operating revs  800 to 4000 rpm

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Image1         Image2

CAD assembly of V8 Vixen                                     CAD assembly of the V8 in the StuG III


Below you see the Vixen into the finished engine bay of a Metalboxmodels StuG model. Note all the plumbing for the liquid-cooling. Feast your eyes on these pictures below. It is without a doubt the pinnacle of internal combustion engine powered model scale tanks to date! The tank is fitted with a hybrid powertrain, both electrically and gasoline.


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StuG1            StuG2            StuG3

See Demonstration Video


More videos 









What happened before


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The Vixen and Metalbox StuG on display at the London Model Engineering Exhibition at Alexander Palace (known as 'Ally Pally'). The engine and CG-2B gearbox attracted much attention and was a real crowd pleaser.


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Mike’s Vixen V8 powered Panzer on display during ‘The Model Engineer Exhibition’ in Sandown Park in the United kingdom. It stood amongst his other extremely impressive model engineering work like the two exact 1/4 scale replicas of the Bristol Mercury 9-cylinder radial engine! Mike presented a very interesting lecture ‘The evolution of the Radial Aircraft Engine’. The Panzer’s transmission was fully functional and the enthusiastic audience awed breathless during his demonstrations. Me and my wife were the Vixen-V8-groopies and enjoyed his lecture and demonstrations very much, thanks Mike!


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On the left above, the centre differential of the triple differential system. The servo drive motor is made from a cordless drill motor and provides fully proportional steering in addition to the clutch/brake steering provided by the CG-2B gearbox. ( note the similarity with the S-tank transmission scheme! )
A temporary electrical installation was made so that the whole drive train could be tested using the onboard electrical motor in place of the Vixen V8. The tests were very successful and both the clutch/brake and the fully proportional steering system worked well, first time.


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The epicyclic units are made from recycled Sturmy Arched 3-speed bicycle gearboxes. The first photo shows the parts to be used. The standard Annulus Gear needs to be reduced in length, problem is it is as hard as flint. So I used a 25mm diameter Dremel cut off disk, run at high speed, to cut it up. It was all done in less than half an hour, and several broken disks. The Planet Gear Carrier material is also too hard to modify; so a new item was made as a direct copy but modified to interface with the pinion shaft. The Sun gear was pinned to a new shorter shaft. I used a 40 tooth 5 mm pitch toothed belt pully.


Picture 017            panzer3_front            panzer3_doggie           


Feast your eyes on Mike’s artwork. The following pictures show the early progress on the V8 work. The last picture shows the CG2B and the V8 Vixen mounted in a wooden Panzer3 mockup.  Note the radiator behind the V8; its from a CPU cooler and fits (and looks!) perfectly inside the hull. Mike wrote; ‘A large packing crate arrived from METALBOXMODELS from China. Wow!!! what a jewel. The lower half of the Pz 3 arrived fully assembled as in the photos. I just could not wait to put in the CG-2B and the Vixen V8 and the radiator. Just look at them; they were just meant to be in there. Even the dog (Molly) got into the act!’ I have been admiring the magnificent workmanship on the PZ111. It is far more authentic and detailed than the Armortek equivalent. I will use the electric outboard motor to run it around until the Vixen is ready.’


V8            V8_3            image031


‘You can see I have made progress on the water-cooling, exhaust manifold and \inlet manifold. The latter is made in two halves, glued and screwed together.  The cylinder heads are now fully ported and now only awaiting the valves and rocker arms.’

Mike wrote:’ I have attached photos of the camshaft in the milling fixture, eight cams have been profiled and the other eight are waiting there turn. It is a very slow process and the silver steel is very tough and rapidly wears the cutting edge off the mill cutter. There are also photos of the completed cam shaft and several stages of assembly of the complete valve gear. The assembly actually took a full day, as I had to finish the 'Fix' to the cylinder heads and also insert the valve guides and valves. Lots of true 'fitter' work to make everything fit, just so. I can make the pistons and conrods without the engine. I will later hone the cylinder bores and make the piston diameters to fit, also bore the big end bearings to match the crank pins.’


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‘The first photo shows the inlet and exhaust valve production method. The valves are made from 303 free cutting stainless steel. A short length of the valve stem is turned to final size and the keeper groove is cut with a narrow parting tool. Then the full length of the valve stem is machined to size and polished to fit the bronze valve guide. The valve head is then profiled to shape. The part finished valve is cut off the stock material, held by the valve stem to faced off the valve head. The other photos show the result of another months work. I have made 18 (plus a few spares) valve guides, inlet, exhaust valves, spring keepers, cam followers and cam follower guides; not to mention a large quantity of steel and bronze swarf.

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The crank shaft and cylinder liners are made from a very tough chrome molly alloy steel. Machine speeds and feed-rates were considerably slower than with aluminium alloys.  It was essential to remove as much surplus material on the milling Machine before eccentric turning the four crankpin journals on the lathe. It all took a very long time, but was very rewarding to see it spin freely in the crankcase.


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The cylinder liners fit into the aluminium cylinder jackets and will be sealed with 'O' seals top and bottom. I have still to hone the bore to the final size. I will do this with an expanding lap and diamond abrasive paste. Finally, I have made the flywheel out of a 50 tooth Mod 2.0 gearwheel, which matched the starter motor gear, fitted the engine mounts and the starter motor. It took courage to connect the starter motor to a fully charged battery, but everything was OK, It all spun freely and the flywheel and crankshaft continued spinning for ages. All I need now is some pistons fuel and ignition.’

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