> > > > > > Jerry Hey wrote:
>> > > > >
>> > > > > Paul, I completed the deflection tests. The MMP
deflected .174"
>> > > > > measured at 24 inches. Tracy's adaptor plate deflected
>>.137 inches
>> > > > > measured at 24 inches. I'm dying to find out what
this signifies.
>> > > > >
>> > > > > You need not worry about the test stand deflecting at
all. It was
>> > > > > very rigid and heavily braced. The steel plate is .375
>>thick with a
>> > > > > piece of 3" channel as stiffener from top to bottom.
This was tied
>> > > > > into the stand frame and welded to the 3" plate.
During the test we
>> > > > > kept bubble levels on the stand and saw no movement.
The two foot
>> > > > > tube is 4.188 o.d. Wall thickness is .188"
>> > > > >
>> > > > > Jerry
>> > > > Excellent work Jerry. Thanks a bunch.
>> > > > This is 600 ft pounds of torque applied to the motor plate
>> > > > and 300 pounds of shear load applied to the 10 mm bolts and
>> > > > 3.050 long 1/2 inch thick spacers. 600 ft pounds is the gyroscopic
>> > > > torque you would get from a metal prop rotating at 2500 RPM and
>> > > > pitching at 60 degrees per second. A worst case scenario
>> > > > as we mostly run wood or carbon fiber props.
>> > > >
>> > > > That includes the deflection in the two foot long, 4" dia.
>>188 wall,
>> > > > steel pipe, the steel flange and the 10 mm bolts and
spacers. Not bad.
>> > > > .174 in 24 inches is only an angle of .44 degrees. So
Tracy's stock
>> > > > plate deflected about .42 degrees or so. Hardly any
>>difference. I think
>> > > > if we tested his super light weight plate version it
would probably
>> > > > deflect more than our pocketed plate.
>> > > >
>> > > > I here bye sign it off for production :-)
>> > > >
>> > > > You might unload the 300 pounds and put the dial indicator under
>> > > > the plate and reload the weight to see how much the 10
mm bolts and
>> > > > spacer are deflecting due to the 300 pound shear load.
We will need
>> > > > to do that to prove to Tracy that our spool and our 360
degree 1/4"
>> > > > plate spacer scheme is as stiff as his 1/2 plate spacers.
>> > > >
> > > > > Paul Lamar
RE the 360 degree spacer plate: I think I can do it with .125 thick
aluminum but I don't have anyway to roll .250. Also, putting .250
over the .750 spools exceeds the outer edge of the bell housing.
Half of the wrap around plate would not be touching the bell housing.
If the .250 plate was rolled and then cut into sections it could be
welded to the spools and lined up with the bell housing. But what
a pain! Far better would be a cast spacer. I think the pocketed
plate together with a cast spacer would prove to be the ideal
> combination. I like it better than casting the entire mmp. because
> it allows us to customize the Barry mount locations and it is a
> simple shape to cast. It should very reasonable. Jerry
0.125 is fine if we go most of the way around.
Do you want to take a stab at making a casting pattern?
You will need a draft of 1/64th per inch. Shrinkage for
aluminum is 1/4 inch per foot.
A good heavy duty pattern could be welded up out of tapered
spools and tapered and curved 3/16 plate segments as that is about
the thinnest that can be cast. Don't forget to make it
a bit over sizes for shrinkage.
Paul Lamar
I'd be interested. Two questions, how much is a "bit oversize?"
Secondly, how expensive is it to get small runs cast? No point in
in making a pattern if producing the parts is prohibitive. Jerry
Well .25 inches in 12 inches is 2% over size for shrinkage.
Multiply all the original dimensions by 1.02.
As I recall the bell housing is about 12 inches in diameter.
So the diameter of the pattern would then be 12 1/4 inches.
You will also have to taper the 3/16 inch thick plates in a
mill and make them wedge shaped. .196 on one the thick end
and .103 on the thin end. Probably better to go 0.25 on the thick
end and .157 on the thin end. Make sure you weld each
tapered plate in the same direction on the pattern as you need
pull the pattern out of the sand mold. Also the tapered
plates need to be carefully shimmed up to align with the
spools when welded.
Same goes for the spools. Assume you are using a
.75 inch diameter spool. It must be tapered on one end to .656 on
the small end. The whole Idea is to be able to pull
the pattern out of the sand mold with out destroying the mold.
0.75 is a bit marginal for the two spools that go around the
0.59 diameter hollow dowel pins in the rear end housing. You might
want to go up to .85 and .756 on those two.
All the welds would have to be ground smooth with a nice radii
using a die grinder and polished. One thing about a welded aluminum
pattern. It can be adjusted at the foundry by a bit of die
grinding and polishing if it does not pull from the sand
perfectly.
A casting would cut a lot of welding but the raw cost would be
close to $50 to $100 plus machining cost. Mainly taking
a clean up cut on front and back to final dimensions of 3.05
high and drilling and boring the dowel pin holes.
If you pull that off your next project can be complete cast bell housing
incorporating the motor mount brackets :-)
Paul Lamar
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