George Lendich wrote:

Paul,
Using your drawings as a guide I've approximated the size of the holes
which are 1.75" top and 1" bottom (adv of 1.375) and 1.5"
long.

Therefore 1.375"x 1.5" x.216" (5.5 mm)thick = .4455 cu inches
.4455x 13 holes (being 9  plus the centre 4) = 5.7915
5.7915 x .1 (weight) = .57915 lbs

Did I go wrong somewhere ?
A lot of work for half a pound!

George (down under)

Yes that is about right. My holes were a bit small however. They should be

a bit

larger and further out to the edge. The other weight savings comes from

pocketing

out that massive 15 mm thick center plate.

It would be a big help if you can get the wall down to 4.5 mm.
That alone with the current design would yield about 2.5 pounds.

However I like your new design. I'll attempt to make an accurate 3D
and Rhino can calculate the weight.

Paul Lamar

Paul,
The 3D drawings are great when you are trying to explain concepts to the
foundry and machinery shop - they also add that element of professionalism
and credibility to the project when showing the drawings.
As you say a picture says a thousand words.

Question - how much thickness do we need to retain in the centre section,
where it's scalloped-out, 4.5 mm ?

Yes because now we have a cylinder that surrounds Tracy PSRU closely.
The loads from all the long 1/4 inch bolts go around the corner
and into the cylinder and then into the ribs. A 10 mm thick ring
about 30 mm wide centered on the 1/4 inch bolt holes would be perfect
on the inner surface of the bell housing. 4.5 mm or .177 inches
thick is plenty everywhere else. 

The ID of that cylinder should be 6.75 inches 172 mm as I just measured 
Tracy's PSRU OD today.

I can take a couple of mm (height) out of the rear flange which in turn
reduces the hight of the strengthening ribs, which can also be reduced even
further.

The flange can also be 4.5 mm except where the bolt holes go.
The little bolt hole  plateaus need to be 13 mm thick. 
Maybe more where the two locating hollow dowel pins go. Lower left and upper right.
The hollow dowel pins stick out of the end housing about 5 mm.

The ribs taper from the back 28 mm deep to the front 22 mm deep and at the
face 19 mm to 14 mm deep - that makes the apex at the corner of the rib some
27mm deep - to the face of the housing.
A little reduction there, do you think?

I don't follow you here. Are we talking about the triangle shaped ribs?
The cylinder should be about 40 mm high and since the OD of the
cylinder is about 180 mm and the OD of the bell housing proper (not
the flange) is about 356 mm the base of the ribs should be 80 to 85 mm
long. PL

The ribs themselves are about 5.5 mm (thick) and I can pull a mm out of
those as well.

Yes that too. PL

The mounting pads are bigger (wider) than they need to be - some adjustment
there.

Mounting pads? PL

I'm getting rid of the top stops in the MM sides, they represent extra cost
in machining, complexity and weight we just don't need. I would recommend a
steel nut plate there anyway.

Four 5/16 bolts in single shear is plenty good. If somebody is worried
about it they can go up to 3/8 bolts or use hollow dowel pins. PL

An adjustment here a tweak there and before you know it we will have it
exactly as we want it.

In reality I guess I had to go down this path, to clarify all the issues. I
suppose we are at the nitpicking stage Butch suggested.

George (down under)

 
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