George Lendich wrote:

Paul,

I turned-up a plug for the housing centre hole, to set the depth
of the ring gear to that of the starter gear.

As can be seen the ring gear fits perfectly in the top of the
housing with about 2 mm gap (between gear teeth and housing) .
The starter gear teeth mesh nicely with the ring gear.

Weight is down to 13.8 lbs, which is by no means the lowest
weight we can achieve.

George (down under)

Okay, Okay, I finally did something.  I just pulled the redrive off the
motor
and weighed the aluminum bits including the rear axial bearing seat on
the RWS RD1B and it's 4837 grams.  I think that's 10.64 lbs.

Chris C.
microcosman.com/aircraft

I think we can get some more weight out of George's bell housing once
I get it in my hot little hands. There are a bunch of 3 inch holes

possible.

Also some pocketing around the center plate which could eventually go into
the pattern. I also need to see the wall thickness's. Perhaps we can get
it cast here in CA with thinner walls.

Paul Lamar

Chris C, Microcosm.

That's good feed back, I beginning to get the feeling we can get the weight
down to less than that with thin walls.

Paul,
The feed back I'm getting is that 4 mm walls is possible if the runs
(distance the aluminium has to run) weren't so long.
When I built the pattern, I used a 3 mm and a 2mm stiffener material, I also
used a one layer bi-axial layer to give it strength.
Perhaps a 4 mm stiffener with one layer of fibreglass will give about a 4.5
mm.
Also I put  more than enough in the corners to give them a nice radius -
this could be reduced.
The squaring -up of the corners of the  MM sides added additional material.
There is extra thickness in the PSRU mount plate and as you say this can
also be reduced with some milling or pattern changes.

I guess I made the internal stand-offs a bit on the big side to allow for
measurement errors and over-designing (as usual)

I would like to reduce the internal stiffeners but haven't a clue how this
can be achieved.

As you can see there is a fair bit of savings before you start cutting into
the housing. I think the only way to do it to an absolute minimum is to
start from scratch.

I will look at that in the next few days but don't want to get too far down
the track in case some further suggestions take things in another directly
entirely.

George (down under)

 
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