I want to start by acknowledging two SRFC list members who inspired me to do this: Mike Blott and Brian Thomasson.
Mike realized that it's possible to push the GWS prop much further onto the shaft than is shown in the advertising pictures. This allows the shaft to be shorter which helps the prop run true, and makes the shaft less likely to bend in a crash.
Brian posted a note on SFRC pointing out how overbuilt the GWS gearbox really is. He posted a few pictures showing his mods to make the assembly lighter for use with a Braun prop.
Since Brian used much lighter props he discarded everything except the front ball bearing support. Unfortunately this made the gearbox far too weak for use with the standard prop and some further tinkering was called for.
I arrived at the compromise configuration shown here trying to remove some extra weight and to shorten the propshaft. However, a totally unexpected benefit was that the gearbox becomes much easier to mount on a plane with glue, by taping in place, or with rubber bands.
Note that there are now 2 different versions of GWS props and
propshafts:
the first version uses 2 dimples to seat the prop. If you have this type, press the prop on all the way, then add one of the larger washers and a nut. Turn the nut until it presses the prop onto the shaft so that it's almost touching the black gear. When you are doing this hold onto the prop itself. DON'T hold the plastic gear.the second version has a hex-shaped indentation at the front of the prop. Seat one of the nuts in the front face of the prop hub and thread it on all the way until it almost touches the plastic gear. Hold on to the blade and tighten a second nut against the first nut as shown in the picture.
Here are the other steps to modify your motor:
1. Pull out the circlip and washer at the shaft's rear and remove the shaft.
2. Unscrew the 4 larger screws from the front of the motor.
3. Pull off the rear plastic piece towards the back.
4. Saw the middle section off as shown in the picture.
6. Remove the bits above the front and rear bearings. Since the plastic is somewhat brittle you're better of cutting it off with a saw so you won't have to worry about anything breakin off accidentally.
7. Slide the rear piece back onto the motor.
8. Check that the shaft turns freely and install 2 of the screws you removed before.
9. You can cut off the rear section of the shaft or leave it in place. If you use a grinder to cut the shaft be careful not to overheat the it since this may distort the plastic gear causing it to slip.
11. Install the prop on the shaft as described above.
12. If you want to shorten the front of the shaft, after you install the prop cut it off as shown in the picture and file the end smooth.
13. If you are going to glue the motor in place wrap it tightly with a few turns of masking or other paper tape.
14. Insert the propshaft and prop into the bearing supports and find a suitable plastic or rubber tube to press-fit onto the rear of the shaft.
15. Pat yourself on the back for a job well done and go fly!
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