Bargain Geared Motor for motorizing plastic kits

I was at the Edmonton Dollarama store when my eyes lit up on seeing a handheld battery (2x AA cells) powered pencil sharpener (CDN 2 bucks
only). Right away this was the solution to powering a number of boats ( Revell Flower class corvette, civilian boats and a fishing boat) that had bugged me for years as the shaft output is suitably slow and has a very high torque output. I showed it to my hobby shop guy and he agreed that it is a real bargain as the motor itself would have cost more than $2 and the reduction gears more like $15 if sold in a hobby shop as an independent item.
"the shaft output was suitably slow and had a very high torque output." Every RC conversion of the corvette on YouTube typically shows the corvette moving way too fast. This is understandable as making one's own reduction gears is too complicated and it is impractical to slow down the motor itself (no guts.) You wouldn't believe the number of toys and alarm clocks I butchered in my search for a solution.
I have experimented with several ways to adapt this pencil sharpener to drive a boat propshaft. This is the best solution, still working on it, I came up with.
The sharpener comprises a clenched--fist sized conformal plastic housing. Discard the battery cover and build up (I used foam board inserts ) the battery recess to be level with the other half of the flat base. This creates a firm flat base for the sharpener assembly that I can install with minumum fuss to the bottom of the boat and with it aligned to the propshaft datum. Solder external wire leads from the (AA battery) terminals (to the motor) to connect the motor directly to an external battery power pack.
My battery pack for this sharpener motor is a regular blister pack of two D cells. I used a solder iron to burn holes into blister plastic so that I can solder the wires directly onto the D cells inside the blister packing. Silicone seal the holes to keep water out. Trim the card to fit the battery pack to the hull equipment installation. The card should be easy to screw to the bottom of the hull to secure the battery, a neccessary precaution for RC boating. Fit switches and the RC equipment connections to the wires. This solution does away with having to buy a battery holder or the need for a rechargeable battery. For a buck one should have an hour's or more of motor run time and just toss the pack away when the juice runs out.
Sharpen a pencil sized wood dowel and let a 3/4 inch stub stick out of the sharpener. I bought half a dozen sharpeners as they are real cheap and often Dollarama items don't come around again. Use another sharpener to make a tight fit point as the taper is slightler longer than the garden variety pencil sharpener. I haven't done this part yet but this is my plan. I intend to pare/sand down a 1/4 inch length at the flat end of the dowel to accept a coil spring The other end of the spring will fit a metal collet (will make one) attached to the propshaft. This allows a transition connection from the sharpener's larger output shaft to a much smaller diameter propshaft . The spring takes care of any minor motor-propshaft mis-alignment as well as act as a torque shock absorber. I won't need a universal joint coupler. At $2 you can afford to take a sharpener apart to see if you can come up with a better installation. I did and it is still the best to leave things well enough alone and do what I did.
To fix the sharpened end of the dowel firmly to the gearbox output remove the steel blade. Replace in the same position, but covering the whole recess space available, a metal plate bolted down with the same nut and bolt. Where the plate covers the "sharpener" slot drill two small holes for tiny wood screws to secure the pointed dowel end. Now there won't be any slack or backlash.
One more refinement. I am using a brass rod inside a brass tube for the propshaft and prop tube. The commercial ones are either too large or too small and don't fit the available props. I have seen brass tubes soldered vertically on the forward end of the prop tube. I presume this is a stuffing box to fill with some sort of grease to keep water from entering through the propeller end of the tube. My solution is to use a plexiglas square rod (homemade from scrap) large enough to to drill a hole for the prop tube to pass through it. I'll drill a reservoir into the plexiglas that will allow cooking oil (non toxic, biodegradeable) to enter a small hole in the prop tube to lube the tube as well as keep water out. The plexiglas rod will also serve as a proptube brace.
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