The Final Views of the Hodgson 9

As of 3 April 2005, I consider the Hodgson 9 Finally completed! Here it is in its final iteration.

The engine is fairly large. On the back of the firewall is the small, 1,200 mAH sealed lead acid battery, the throttle and spark levers, and the transistorized ignition. On the engine side of the firewall is the fuel/oil tank, and the coil mounted towards the bottom.

The battery is perhaps oversized. If you make a similar engine and ignition, you could probably mount an 800 mAH 6 or 12 volt battery and be assured of lengthy runs.

The fuel capacity I estimate at around 6 to 8 oz, which provides for a medium to full throttled run of perhaps 12 minutes.

Difficult to see are the linkages which carry the throttle and spark commands forward to the carburetor and distributor base respectively. The engine is turning 5,200 RPM with the big 22" propellor. When the electronic ignition (hall effect) was properly functioning, I did measure over 6,000 RPM on occasion. I think the top end right now is limited by the dwell, with some floating of the mechanical points taking place at the high RPM.
A nice 3/4 view. The legs of the firewall are welded from square section tubing, while the feet were turned from bar, drilled, and welded to the ends of the tube. The red paint is a regular alkyd spray enamel.

About the only thing i am unhappy with is the balance of the engine. It vibrates a bit more than I would like, probably due to the use of steel connecting rods rather than the aluminum called for in the plans. I don't think the extra strength is necessary, and in fact 7075 alloy aluminum is generally just as strong as the mild steel I used.

Easier to see now are the control levers and the black plastic housing which contains the ignition circuit. On the fuel/oil tank are 2 standard brass plumbing fittings, with the 2 screw caps modified slightly for appearance. The oil control needle valve is the smaller knurled thumb screw on the far left at the top of the tank. The spark plug wires are #18 test probe wires which are especially pliable and well-suited for this duty. I have noticed a little softening of the rubber insulation around the heads where they get a bit oil soaked, but in general they perform well.

 

 

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