Rear Drive System

The Rear Drive System (RDS) is up, running and available. This past summer we were involved in testing an advanced Power Fin propeller on the RDS. We concluded the summer with 75 hours on the prop and RDS. The RDS was disassembled, inspected and found to be in perfect shape. So in addition to wood propellers, you now have the option to use a Power Fin propeller with the RDS. The primary reasons we choose the Power Fin to test is because it is available in a two or three blade version, it is ground adjustable, and has a very low moment of inertia that is very comparable to a wood prop. All the testing was again done on our company airboat with a 2074 cc engine, featuring a CAST 78mm crankshaft. We know your next question - "how about other props"? All we can say is if you do, it is at your own risk. Be careful and check and double check!

The newest feature we have available for the RDS is the top mounted intake manifold. This is four equal lengths of aluminum tubing, welded to a plenum box on one end and intake flanges on the other end. It is designed to fit the Ellison EFS-2 carb only. It will fit under the cowls of most VW powered home built aircraft. Builders have reported gaining up to 200 rpm by moving the carb from underneath the engine to the top of the engine. The intake manifold system is priced at $219.95.

While on the subject of the RDS, we have been working on an in-flight adjustable propeller of our own design for the RDS. We hope to test it next summer on the company airboat. If successful, it will make a truly great engine and prop package. Imagine being able to turn about 3600 rpm or greater on take off and climb and then being able to dial in the pitch for cruise. And I almost forgot, we are working on the installation of a vacuum pump to the RDS system also. Check the Beetle Flyer Sale section for a great deal on the RDS package and long block kits.

to you and your family from the staff at Great Plains Aircraft. We would like to thank you for your continued support.

Oil Pressure Cures

This last year has produced a rash of oil pressure problems in the field. The majority of the problems started when pilots replaced the oil pumps in their engines. When installing a new oil pump check the following:
Make sure the pump body is the right one for the engine case. The inlet and outlet of the oil pump body need to line up with the inlet and outlet on the engine case.

The length of the drive shaft that goes through the drive gear is critical. The drive shaft needs to seat in the slot that is in the center of the camshaft. Use a caliper and measure from the oil pump body to the back of the slot in the camshaft, then measure your shaft's length. It can be pressed out to make it longer. Some builders have been using gasket sealer on the gasket between the cover plate and the oil pump body. This is not correct! This gasket goes on with only a light coat of oil. There should only be about .002" running oil clearance between the gears and the oil pump cover plate. Any additional clearance will result in low or no oil pressure. On a new oil pump, pack the teeth of the oil pump with bearing grease to get oil pressure ASAP.

Two other problems we have seen. The oil filter screen some times has to be tapped onto the 6 oil sump studs. Some builders have tapped the filter screen in the center of it vs. the flange. What happened in one case was the screen was tapped so hard in the center that it collapsed around the oil pickup tube and did not allow any oil to be picked up by the pump. The other case we saw was with a used engine case and the builder had replaced the oil pickup tube with an incorrect one (no they are not all the same). The oil pick up tube fits very loosely into the female end of the case and in the 3 point position, oil was below the pick up tube (where it attaches to the case) and was sucking air and mist.

Half VW users have the opposite problem. When the case is cut in half, about half of the oil volume is reduced. A stock oil pump will pick up oil faster than it accumulates in the oil sump. Cure is to cut about 1/4" of an inch off the gears and replace with a steel washer of similar thickness. This will reduce the volume of oil pumped allowing the oil to accumulate in the sump at a greater rate than it is picked up by the pump.

The last oil problem that seem to rear itself frequently, is located at the flywheel. When assembling an engine you must make sure that the dowel pins on the end of the crankshaft do not protrude beyond the face of the flywheel. When using a stock 69mm crankshaft with four dowels this is not usually a problem. It is more frequent with the 8 dowel crankshafts. What happens is that the flywheel may not seat against the end of the crankshaft. This allows oil to seep around the gland nut and dowel pins and show up as a small oil leak at the bottom of the Diehl Accessory Case.

Spark Plug Adapters

Frustration can be the mother of invention. We have tried over the last 20 years to buy direct from Champion Spark Plugs and have been unsuccessful. No question that shielded plugs are necessary to eliminate ignition noise, which can also interfere in some aircraft with instrument readings, Loran, etc... Well, in talking with my machinist about the procurement problem at Champion, we came up with the idea of a housing to fit over a standard Bosch spark plug that would adapt to the Slick M2266 harness. As in most cases, it took three tries to get it right. The spark plug adapters have been tested on the company KR for 50 hours and I am please to report that in our aircraft there is actually less radio noise than I had with shielded plugs.

There is no customer machine work or modification needed other than to reduce the spark plug gap on the Bosch plug from .028" to .017".

Shielded plugs sell between $19.95 and $21.95 each. The spark plug adapters and plugs sell for $89.95. Next time you need plugs though, you'll only pay about $8.00 for the set of 4.

Web Update!
The entire Great Plains Catalog and the Sonerai Info Pack are loaded onto our web site! We have also loaded an encyclopedia of VW Powered Aircraft to the site.
NEW-NEW-NEW-NEW-NEW
A Shopping Cart feature will be loaded soon! Our Web address is:
www.greatplainsas.com

Sun & Fun 2000 VW Workshops

We have agreed to do the VW assembly and test running of an engine from start to finish, at the EAA Sun & Fun 2000 Convention again. There will be a few small changes this year. We will start the workshops on Monday and end on Thursday. There will be no VW workshops on Sunday, Friday or Saturday. Because of the time involved in doing the workshop, we will not be doing a formal VW forum as we have for the past 15 years. Simply attend a workshop or stop by the booth if you have questions. Our booth is in building "A".