Thursday, September 15, 2016

There's nothing like an Allison V12 if you want power

Some time ago I got my hands on MPC's Allison-powered Thunderbird, known as Allison Thunderland, or simply Big Al. Chassis and body are pretty poorly detailed, but the Allison V12 is well done and, apart from being entirely chromed, is a joy.

My interest in doing something with the Allison was revived by a tour of the Curtiss museum in Hammondsport, New York, in July this year. This is a great museum if you are a serious piston head. Apart from a number of oddball motorcycles and other odds and ends from the prewar era, they have many early aero piston engines, from a wide range of radial motors (several Curtiss motors among them, obviously) to the various V12 motors designed in the years leading up to WWII by Rolls Royce and Allison among others. The ultimate in this line was an example of the 3000 horsepower Allison Double Twelve, consisting of a pair of V12s on a common crankcase and last used in the B29. 

All this reminded me of pictures of a monster rat rod I once saw online, using a Packard V12 out of the PT boat program. So a truck-based rat rod seemed in order. Next question was what to put it in, and coincidentally AMT's White Freightliner, in the short-cab single-drive version, turned up this week. The chassis will get highjacked for the Allison, and the cab will go on my dual-drive kit in place of the sleeper cab that it came with.

First step was to dechrome the motor, so out came the Easy-Off. This left a shiny residue behind that required additional soaking in alcohol.

The Allison gearbox, visible in the photo above in the sprue on top next to valve covers, is really just a clutch housing and maybe just a reduction gear, so first step in converting this to a rat rod was to fit the gearbox from the White. Coincidence or not, this fits right on the back of the Allison, with the same 'D' shaped doweling requiring no filing or fabrication. Further coincidence, the Allison engine mounts sit perfectly inside the White chassis rails, at just about the right height to line up with the differential while sitting high enough for the exhaust pipes to clear the chassis rails. All that is needed is to tilt the motor slightly back as with the Cummins, so the driveshaft clears the middle crossmember; I'll shim up the forward mounts for this purpose. Was the White kit designed for this motor as Plan B? 

Quite the monster ... although it looks like it will be taller and shorter than I might have liked. I've got a Ford T pickup truck body that might look good on it, although a bucket would probably be more appropriate. Clearly the Freightliner radiator will be way too tall.

Note the front wheel is not attached at this point, and will sit further forward giving a lot less front overhang than the photo implies. Good progress so far; my intention will be to at least finish something in the next little while ... given I have been retired for a couple of weeks now, there should be plenty of time. Stay tuned!

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