Cuyuna 430

Last updated
Cuyuna 340 & 430
Type Two-stroke aeroengine
National origin United States
Manufacturer Cuyuna Development Company
First run1979
Major applications Pterodactyl Ascender
Unit cost US$800 (1980)

The Cuyuna 430 and Cuyuna 340 are a family of two-stroke, twin-cylinder piston snowmobile engines that were redesigned to serve as ultralight aircraft powerplants. [1] [2]

Snowmobile land vehicle designed for winter travel on snow

A snowmobile, also known as a motor sled, motor sledge, skimobile, snowscooter, or snowmachine, is a motorized vehicle designed for winter travel and recreation on snow. It is designed to be operated on snow and ice and does not require a road or trail, but most are driven on open terrain or trails. Snowmobiling is a sport that many people have taken on as a serious hobby.

Contents

Development

While developing the Pterodactyl Pfledge flying wing ultralight in the late 1970s, designer Jack McCornack experimented with a number of possible engines. Early flights used a German-made Sachs engine, but the high exchange rate and long lead times for this engine convinced him to try other options. [2]

Pterodactyl Ascender

The Pterodactyl Ascender is a family of U.S. designed and built ultralight aircraft that were sold in kit form between 1979 and 1984 under Pterodactyl Limited and is currently being sold by DFE Ultralights.

McCornack settled on a snowmobile engine produced by the Cuyuna Development Company as having the best potential. In 1979 he modified the engine with a crankcase extension, an additional main bearing, lowered the compression ratio using an additional head gasket and substituted a smaller 32 mm (1.26 in) Mikuni carburetor, amongst other modifications. The original snowmobile engine produced 40 hp (30 kW). Lowering the compression ratio not only de-rated the engine, but also made pull-starting easier and allowed it to run on lower-octane regular auto fuel. The resulting engine worked well, was de-rated to produce 30 hp (22 kW) at 5,500 rpm and proved reliable in service. [2]

Crankcase

A crankcase is the housing for the crankshaft in a reciprocating internal combustion engine. The enclosure forms the largest cavity in the engine and is located below the cylinder(s), which in a multicylinder engine is usually integrated into one or several cylinder blocks. Crankcases have often been discrete parts, but more often they are integral with the cylinder bank(s), forming an engine block. Nevertheless, the area around the crankshaft is still usually called the crankcase. Crankcases and other basic engine structural components are typically made of cast iron or cast aluminium via sand casting. Today the foundry processes are usually highly automated, with a few skilled workers to manage the casting of thousands of parts.

Compression ratio The ratio of the volume of a combustion chamber from its largest capacity to its smallest capacity

In a combustion engine, the static compression ratio is calculated based on the relative volumes of the combustion chamber and the cylinder. It is a fundamental specification for combustion engines. The dynamic compression ratio is a more advanced calculation which also takes into account gasses entering and exiting the cylinder during the compression phase.

Carburetor Device in internal combustion engines

A carburetor or carburettor is a device that mixes air and fuel for internal combustion engines in the proper air–fuel ratio for combustion. It is sometimes colloquially shortened to carb in the UK and North America or carby in Australia. To carburate or carburet means to mix the air and fuel or to equip with a carburetor for that purpose.

Citing liability concerns over producing a two-stroke engine for human-carrying aircraft applications, Cuyuna declined to produce the modified engine. Instead, Cuyuna decided that the resulting engine was different enough from the base snowmobile engine that they would supply assembled and test-run shortblocks as parts to McCornack's company, Pterodactyl Limited, who would then complete the engines and be the manufacturer, allowing Cuyuna to continue producing snowmobile engines. [2]

After two years of poor sales of snowmobiles, due to a dearth of snow and no lawsuits against Pterodactyl Limited regarding the engine, Cuyuna agreed to build the engines themselves. [2]

The 430 was also produced in a reduced 2.362 in (60.0 mm) bore version called the 340. The modification reduced its displacement to 339 cc and output to 25 hp (19 kW) at 5500 rpm. The standard 430 has a bore of 2.658 in (67.5 mm). [1]

Variants

340D
Direct drive version, 25 hp (19 kW) at 5500 rpm, recoil starter. [1]
340R
Reduction drive version using a belt drive system, 25 hp (19 kW) at 5500 rpm, recoil starter [1]
430D
Direct drive version, 30 hp (22 kW) at 5500 rpm, recoil starter. [1] [2]
430F
Reduction drive version using a 3:1 gearbox system, dual carburetors, producing 45 hp (34 kW). [3]
430R
Reduction drive version using a belt drive system, 30 hp (22 kW) at 5500 rpm, recoil starter [1] [2]
UL II
35 hp (26 kW) version

Applications

Specifications (430D)

Data from Cuyuna [1] & McCornack [2]

General characteristics

Components

Performance

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References

  1. 1 2 3 4 5 6 7 Cuyuna Development Company: Cuyuna Engines, Cuyuna Development Company, undated
  2. 1 2 3 4 5 6 7 8 McCornack, Jack (Fall 1980). "The Cuyuna 430D Experimental Aircraft Engine, Ptimes Vol 2 No 1" (PDF). Archived from the original (PDF) on 2011-07-16. Retrieved 2009-09-29.
  3. ↑ Cliche, Andre: Ultralight Aircraft Shopper's Guide 8th Edition, page D-17. Cybair Limited Publishing, 2001. ISBN   0-9680628-1-4
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