Friday, February 6, 2009

ENGINE MOUNT


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Engine Mount
(All photos courtesy of Mike Sample)

When you install the propeller on the clutch-end of the crankshaft it solves a lot of problems, such as having the nose of the crankshaft break off, taking your propeller with it. But like the man said, there's no such thing as a free lunch. Put the prop on the clutch-end of the crankshaft and you have effectively reversed its direction of rotation. That is, if you are sitting in the cockpit of your VW powered Dream Machine and you've mounted the prop on the fan-pulley hub, the propeller is rotating anti-clockwise. But if you have installed your propeller on the clutch-end of the crankshaft, to someone sitting in the cockpit the prop will be rotating in a clockwise direction. Kinda like it shows in the picture at the top of this article.

Another part of your No Free Lunch is having to carve a propeller for that direction of rotation. (Not to worry. I'll post a big, fat article showing you how to carve such a beasty.) This article will give you some idea of what you will need as an engine mount. The tubing is 3/4" x .049" The method of engine mounting also includes some means of shock absorbtion or vibration damping. In this case, the shock mounts are pre-molded rubber mounts usually sold as 'Lord' mounts. I'll include a drawing showing how to make them, as well as another type which uses simple rubber pucks. (The rubber pucks in Lord mounts are tapered on one end.)

As you can see in the photos, the engine mount is triangulated, taking advantage of the threaded busses found on all 1971 and later VW crankcases.

As you can see, a bed-type mount is used on the FRONT/LOWER mounting bolts.

(When dealing with Volkswagens everything is always called out relative to the vehicle. The forward-most crankshaft bearing -- the one nearest the flywheel -- is the #1 bearing and so forth. This is the convention used in more than twenty million Volkswagen engines over the past seventy-five years and I think you'll have to admit it would be rather silly to try and change things now :-)

You may also use individual mounts at this point, the crankcase providing more than enough strength. But the bed-type mount -- something to which you can weld a mounting tab -- offers a number of advantages when installing your oil cooler, carb-heat box and so forth.

Up to this point the mount is the Plain Vanilla version. The following photos show the mount modified to accommodate various cooling and exhaust systems.




Notice that the struts from the upper attachment points has been 'cranked' so as to allow more space under the cylinder barrels. This is to allow the cooling shroud to wrap around the cylinders and heads.

In this arrangement the dynamo is mounted directly to the crankshaft, eliminating the need for brackets, pulleys, vee-belts an so on. The goal here is to provide an engine installation designed for non-mechanics.

If a starter is required, it is installed on the top of the crankcase. It's ring-gear attaches to the crankshaft between the engine and the propeller hub. This will probably require a blister on most cowlings.

On some airframes the location of the gascolator will have to be changed to allow an unobstructed path for the LOWER/REAR threaded bosses. These were introduced by Volkswagen in 1969 to provide a hard-point for installation of a rear engine mount in the Transporter.

The LOWER/REAR mounting bosses are not symmetrical relative to the parting line of the crankcase, something you want to keep in mind when cutting your tubing.

As on all of the later-model engines, the threaded bosses are fitted with Heli-coil type thread inserts. The engine mount is attached to the crankcase with high-strength metric fasteners having drilled heads to accept safety wire.

The last two photos show the engine mount installed on an airframe (ie, look for the yellow paint). From this point on the installation becomes airframe-specific.




-R.S.Hoover
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