Marco Polo Boats is pleased to announce that it is now selling a custom version of the Mitrpak T-102-M right angle bevel gear drive configured for the human powered boat market. We call it the MPB MitrpakDrive.

The customization includes tapered square input shafts (J.I.S.) to accommodate standard unicycle cranks (not shown in photo above), solid internal tension pins to increase the working torque rating, and a simple 6 mm cotter pin groove for inexpensive shaft coupling.

The gear increaser ratio is 1:2. When combined with our PlanetDrive, you can achieve prop rpm unheard of in human power propulsion.

MITRPAK units utilize double-shielded, permanently greased standard metric series ball bearings, hardened alloy steel spiral bevel gears and an aluminum alloy housing for maximum strength and heat dissipation. Stainless steel shafts are standard. Positive lip grease seals lockout contaminants and prevent leakage.

History

There are two major issues in human powered pedal boat mechanisms. The first is to change the direction of the pedaling motion 90 degrees so that power can be transmitted to a shaft and prop, and the second is to increase the rotations made by the pedaling motion by the time power reaches the prop without much loss of energy efficiency so that the prop rotates many more times than the pedaling motion.

Note: This discussion relates to pedal systems that drive a prop, and not those which drive a paddle wheel (usually less efficient and requiring significantly more space) nor fin-type such as the Hobie MirageDrivetm (which does not allow for reverse).

The right angle transfer is usually solved by employing either a twisted chain or belt mechanism from the upper pedal crankshaft. Marco Polo Boats offers its customized Mitrpak right angle drive as an elegant and reliable alternative to the twisted chain or belt.

Drawings/Specifications

You can view technical details of the standard Mitrpak T-102-M here. Our version has the same specs except as noted above.