The AHC "Red Racer" RRV

Created: June 2001
Updated: July 2007
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Texan and Motor Boy Bert Streigler acted as Proof of Concept tester for the AHC Diesel plans and brokered the deal that led to the acquisition and distribution of the project to Australia, Canada and the UK (virtually what remains of the "British Empire", in fact!) Email discussion among our group led us to the conclusion that the AHC performance was severely restricted owing to the physical limitations placed on the engine by the inlet porting. As a rancher, farmer and retired engineer, Bert is always thinking and acting on what he's thinking about. So in short order, Bert set about seeing how the AHC case could be adapted a different induction scheme.

There are two basic possibilities; front rotary and rear induction. From the rear, several variations are possible: rotary valve (disk and drum), reed valve and "clack" valve. Bert chose the rotary valve as this had worked so well on our Vivell 09 reproduction. There was even a half serious suggestion that a dual side-port/RRV variant be tried (there have been production engines that had both FRV and RRV induction). However, we must put that proposal aside as indicative of the British love of complexity for complexity's sake, or the crafting of complex solutions to non-problems (ever worked on a Jaguar?)

He bagan by cutting off the delicate venturi (before it fell off, some might say) and driving a rear rotary valve from a small crankshaft extension timed to give 180 degrees of induction from 40 degrees ABDC to 40 degrees ATDC. Bert applied some heat resistant paint to the case, probably based on the well known phenomena that red cars always go faster (usually while being driven by blond women!) The exhaust and transfer timing are unaltered. The black T-Bar compression screw adds to the sporty look. Bert boldly named it the RED ROVER in honour of the car used in the original Motor Boys series of books. The rest of the Motor Boys, being a somewhat irreverent group, promptly re-named it the RED ROOSTER. That special red rooster paint takes a while to dry out, but I hassled Bert for a test report and here's what he sent back:

Ask for test results and ye shall receive! I mounted up ole Red Rover today, using a 9x4 plastic Master Prop, the same one I ran on the side port before. The engine started almost instantly and I ran it a total of no more than 30 minutes, then cranked right down on the compression and tach'd it at a steady 8,300 RPM! It is still stiff and I bet there is another 200 rpm there somewhere.

Boy, was I wrong about the bypass limiting the engine regardless of the inlet, etc., but that is a good way to be wrong. The engine is every bit as docile to start and handle as the sideport version, but mine is up 2,000 RPM on my other one!!!

The exhaust was nice and clear with no signs of internal problems of any kind. After the running, I took it apart and autopsied the bits and pieces, but there is nothing to report as there were no problems of any kind evident. Vibration is about the same as the sideport version I built, but both engines have a steel rod. This little sucker really barks on that 9x4, but it is still very economical on fuel. The Genie needle valve works nicely. It still runs pretty hot and will require more running in for sure, but there is a walloping performance gain.

With the basic design for the Red Rover worked out, Bert handed the rough plans to Roger Schroeder for pattern making and foundry work on a special backplate. Using no science at all, Roger and I decided that it would "look" better if the venturi slanted back a bit more -- with the extra clearance from the head, finger choking for priming becomes a bit easier. Even though Roger had decided not to make a standard AHC, the temptation to machine one of his castings was too great. The result seen here is the second prototype completed by Roger on 2001-05-20 with his sandcast backplate.

So there you have it. The Red Rover provides the basic engine with the fuel/air mix it needs to reach the capability of the rest of the engine. Side ports are not exactly renown for power, rather they are easy starting and handling engines, able to run happily in either direction as the timing is completely symmetrical. However, they are not generally as restricted as the AHC whose problem lies in the very small inlet imposed by the die casting. The Winston brothers had a real clunker on their hands and probably decided to shelve the whole project.

Our versions are made with more care and precision than could have been brought to bear on a mass produced engine, so will obtain the best that the engine is capable of in this configuration. But for AHC in the 1940's, couple the probable production difficulties they were facing with the general lack of knowledge among US modellers regarding compression ignition engines and add to that the poor performance to spell "forget it"! Today, we can only surmise that testing of the original prototypes must have been very bad for AHC to not carry through on it, given the other engines they did produce.

 

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