Maximizer VW Belt Drive

Well Maximizer plans are available once again. Go to this website: https://docs.google.com/forms/d/e/1FAIpQLScBUXxyrUc8Jw7ZSbng4JmarKgcIBWkl-oV38l3sYzq5D5pYw/viewform?pli=1

The Maximizer Belt Drive Unit designed by Don Stewart to be able to

use the VW engine to a better advantage on airplanes.

Here is the Maximizer on Armando's Headwind

Yes  you can hand prop the engine with the Maximizer on it!

The Maximizer lets the engine swing a bigger prop at slower RPM increasing performance

on a VW engine.

Maximizer Tips

There are two versions of the Maximizer included in these drawings and I’m sure you’ll be able to tell them apart by the title boxes on the prints. The prints with the oldest date represent my original drive and the second is a drive I worked up for Mosler Motors, who changed their name to Tech or something like that. I think they are now out of business.

You’ll notice there are two different belt types used. The best belt is the one shown on the newest design and this belt is good for 65 HP maximum. The 3V belt on the first version is ok for up to about 50 HP. The new design DRIVEN pulley was designed to be turned from either a casting or billet so it’s probably the easiest to build.

Notice that there are also two designs for the DRIVE pulley. If you decide to use the old design, DO NOT build the pulley without the steel component. The pulley WILL FAIL without it. The old DRIVE design, with the steel component, is meant to be mounted to the crankshaft directly. The new DRIVE pulley is meant to be adapted to a crankshaft propeller flange. If you build the new design DRIVE pulley, provide the propeller flange with a pulley pilot at least 1/4” deep and fit it to about +.002” maximum.

You can “mix and match” these parts however you wish and the unit will work fine. You can also modify the mounting holes in the mounting plates to fit your engine. You’ll probably have to do this as the new unit was designed for the Mosler Motors engine and I’m not sure how close it was to the VW engine block. The old design is “old” and I have no idea if VW has changed the case dimensions. It would be wise to check before drilling any holes. If you wish to adapt the unit to different engine, I’m sure a similar plate system can be used.

There has been discussion about the wear on the bearing in the “little” end of the engine. I haven’t heard about any wear from any of the builders of Maximizers and many drives have run to the point that the engine had to be rebuilt. Nobody mentioned wear on that bearing. So far as I have been able to determine, there’s a much higher load on that bearing from propeller gyroscopic loads when running direct than will ever be imposed by the belt tension of the drive if it’s tensioned properly. In fact, one of the reasons I designed the drive was to get those gyroscopic loads out of that bearing and also to relieve the crank of the “stretching” or tension loads from the thrust bearing being located at the other end of the engine.

Please note that the Maximizer name is registered to me and the design is patented. If you intend to duplicate the drive, I’ll be pleased to negotiate a licensing arrangement for use of the name “Maximizer” as well as the manufacture of the unit itself.

Don Stewart

Don's  address is

Don Stewart

W8923 N Lake Dr.

Vulcan, MI 49892.

Phone Don at 906 282 3045.

This letter below written some years ago now-

Don,

I saw your advertisement and just wanted to write to say thank you after all these years. In about 1980 I bought plans and a set of rough castings for the Maximizer from you and machined one for my 1600 cc VW gyrocopter.

I was able to pull 390 lbs static thrust on a 66" diameter wide chord prop at 3950 engine rpm. This equaled the best that could be done on a SCAT direct drive 2500 cc VW engine with dual weber carbs and at a tiny fraction of the price of that expensive conversion.

Fifteen years later I heard that the maximizer was still operating well on the same installation though I don't know how much time it had on it. Thanks again, it made my two seat gyrocopter possible.

Chad Wille, St. Croix Propellers

Below is a article in pdf format from the 1971 article Don wrote about his Maximizer VW belt drive