Here is what it looks like with a 3 inch inner tube and socket
head metric 10 mm bolts. I think this is an improvement but
we can still test what we have. This is a minor change in the
over all scheme of things.
Paul Lamar
That works too. My thought was to extend the three "paddles". By
extending the paddles, there is more space for the silicone.
FWIW - From looking at the welded up assy, I don't see how this little
assy will be able to absorb 350 hp.
Mark
Two ways to get HP. Torque or RPM.
The rotary is RPM. Lets say it generates 350 HP at 7500 RPM.
What is the torque?
HP = T X RPM /5252
350 = T X RPM / 5252
350 X 5252 / 7500 = T = 245 foot pounds.
3000 inch pounds. Divided by 5 inch diameter = 600 pounds total force.
3 rubber lumps 200 pounds per rubber lump.
One inch high by 1.4 inches is 1.4 square inch.
142 psi.
It is hard to quantize rubber for compressive strength
because it expands in other directions 90 degrees to the load.
The tear strength is 580 pounds per square in or about 4 MegPas.
Cut 4 pieces 1 inch by 1 inch. One square inch. Stack them up on the
floor. 3/8th of an inch thick roughly. Best to glue them together
with red RTV and let it cure for 24 hours.
Put the heal of your shoe on the rubber stack and balance with on foot.
See if it springs back to shape.
Paul Lamar
Paul,
If this thing is bigger than 5" and 5" is actually the distance to the
center of the paddles, ignore this. I didn't want to go back and dig up
dimensions.
You should only take credit for the diameter to the center (or so) of
your
metal paddles if you want a closer estimate of the force reacted by the
rubber. Using the 5" diameter of the outside of the pipe assumes all of
the force is reacted by the rubber at the outside edge, which isn't the
case.
Josh
Yes Josh I know :) It is six inch OD and three inch ID.
Paul Lamar
Here is another test Mark.
Get a 3 pound sledge and see if you can beat that silicone rubber into
submission.
Paul Lamar
Sounds like a fun test. I'll give it a try today after work.
How about "bunching" of the plies? As I cut them initially, the force
will
be applied to the edges of the plies of silicone. Should I cut some new
ones and stack them like a loaf of bread so that all the force is
applied across the faces, or does it even matter?
Mark
Don't bother glue those together and see how it goes.
Paul Lamar
Mark, I had this old tube of clear silicone RTV lying
around. It had solidified in the tube. So I pealed off the covering
and performed the 3 pound hammer test.
Here is the video.
Paul Lamar
That looks like it should do the trick. Maybe we should assemble it with
liquid RTV and let it cure, then test it. The rtv would help hold
it together.
Mark
--
It is all the same stuff. You can get it in clear or red.
The red is supposedly higher tenp.
Smack what you got :) You can't hurt it.
Paul Lamar
Mark,
Pep Boys has some silicone hose in three different sizes per package.
1/8 3/16 and 1/4. About 27 feet of it.
Cut lengths to about 1 inch long and insert them in the mold
to provide voids.
Paul Lamar
Paul,
I cut the wooden spacers today and did a fit-check. I only have enough
silicone sheet cut for one section at this time, so that's what you'll see
in the pictures. Next step is to drill holes in the spacers for the bolts,
and to drill the #10 bolt holes in the spline piece, but that will require
me to remove the psru from the a/c. I don't really want to do that right
now as I have my BFR due soon and could use some practice beforehand.
Also, I need to cut more silicone. The bunch in the pictures is 9 layers,
so I'll need to cut 18 more. Not sure if I have enough material on hand.
Then I need to bond the silicone pieces together an let them cure. The
Texas sun should handle that task nicely.
Mark
I am not ready to come down there anyway yet.
Maybe in a week or two.
I am having a heck of a time finding socket head 10 mm bolts 1.0
(threads per mm) 17 or 18 mm long (grip Length).
We need these to go with a 3 inch diameter center steel tube.
I am getting to the point where I recommend drilling
to a 29/64 (.4531) and tapping with a 1/2 20 fine thread tap.
5/8th of an inch long.
At least we can buy socket head screws in that size.
If your building a heavy duty engine this is what you do
with the tension bolts.
Paul Lamar
Would Kevlar fabric (layers on any axis)improve the buffer modules performance? With a
pour your own, you get lots of options. Even vac. bagging of mold.
C. Smith
I think it would stiffen it too much.
With that chunk of curred pure clear that I have the 3 pound
sledge hammer had no effect on it.
I suspect we will wind up with a lot of void in the bumper.
Short pieces of silicone rubber hose surrounded with
curred silicone liquid.
Paul Lamar
I have it on good authority that 10 MM 1 mm pitch socket head metric bolts are not made.
So we are going to make some.
I am going to make the 10 mm socket head bolts on an NC lathe.
We start with a two inch long grade eight 7/16th 20 and re thread for 10 MM 1 mm pitch.
It is a metric socket head bolt with a 3/8 Allen head socket.
Six of them will be part of the coupling kit.
Paul Lamar
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