> > The stock renesis oil filter pedestal is very tall. Tracy Crook
> > used a
> > 3rd-generation (FD) pedestal on his Renesis. I found that the
> > intake/output holes don't align exactly -- so he probably honed
> > out the
> > block before the engine was assembled. This is hard to do once the
> > engine is built. Also, the other generations of oil filter
> pedestals
> > won't fit (only the FD and Renesis have the ancillary oil line
> > takeoff).
> >
> > It may be easier to just mount the filter remotely. It is pretty
> easy
> > to make a piece of 1/2" 6061 that fits over the engine block holes,
> > which are about 0.4" ID. Tapping the block out to 3/8" NPT allows
> > a -8
> > fitting to be used, without any reduction in the internal diameter.
> >
> > The FD oil filter pedestal can be mounted almost anywhere. Using an
> > angle bracket gives a lot of options. For Paul: Is 1/4" 6061 with
> > 3/8" NPT threads strong enough to handle the 100 psi or so from
> > the oil
> > system, or must an angle bracket be made of thicker material?
> >
> > Thanks
> >
> > Scott Gettings
> >
> > Hi Scott, Just a suggestion while your in the planning stage:
> If
> > you mount the filter can horizontally some oil will remain in the
> can
> > and you will need to catch it when you change the filter. If you
> have
> > the opportunity to mount it vertically, gravity will drain the oil
> > effectively one way up or leave the can full the other way up.
> Either
> > way up will make oil changes more manageable and if their easier
> > to do
> > they'll get done more frequently. Remember oil quality is especially
> > important to the rotary in aviation use. Dave M
> >
>
> Great suggestion, thanks! I can easily mount this bracket on the back
> of the PRSU plate (pusher configuration) with slightly longer hoses,
> which would give a vertical filter orientation. (My oil pan contains 6
> quarts, too.)
>
> Can anyone answer the above question as to whether the 1/4" 6061 with
> 3/8 NPT threads will be strong enough for the 100 psi or so of the oil
> system? I suppose one approach would be to test it to 300 psi.
>
> Scott Gettings
>
> Hi Scott, The Rule of Thumb is to provide one and a half times
> any thread diameter for that thread's engagement. For example: a
> 1/4-20
> thread should engage 3/8 of an inch. In hard materials (tool steel)
> this
> could be less in soft (aluminum) it should be more. This Rule of Thumb
> provides enough shear area at the thread root to approximately equal
> the
> tensile cross sectional area of the bolt at the thread's minor diameter
> and allows for some manufacturing defects that none of us ever make :)
> Your 3/8 NPT has about a .665 O.D. so multiply that times 1 1/2 and
> your thread engagement should be .997 Therefore your material stock
> should be one inch IN THE AREA OF THE THREAD, for example : you could
> weld a boss onto your aluminum angle iron. Or start with 1 inch stock
> and machine away what you don't need. Or keep it all 1 inch and go into
> the side with your mounting screws ( a 3/8 threaded hole in the 1 inch
> side would need : 3/8 hole + 3/8 wall +3/8 wall = 1.125 stock....walls
> are getting thin I would go with 5/16 threaded holes : 5/16 hole + 5/16
> wall + 5/16 wall = .937 that's within the 1 inch stock proposed to be
> used). The problem is not the pressure as even a thin amount of
> material
> will withstand an enormous amount of internal pressure. The problem
> will
> be vibration causing metal fatigue. Think of a beer can :) there's
> internal pressure but even the very thin aluminum can can restrain it,
> but empty the can...ahhhh.. then fold it and flex it. After two or
> three
> vibrations ( a flex is a slow vibration ) the metal fatigues, and the
> can fractures. I know that 1 inch stock is not what you wanted to hear
> but it is reality so the trick now is to make it lighter somehow,
> basically remove stock where it is not needed. Hope this helps your
> decisions. Dave M
>
>
>
Wow, thanks. This rule of thumb must be pretty loose, since there are
all kind of fittings, holes, etc. that have much less meat than this on
the Renesis engine. I wonder if the rule is different for a bolt vs. a
pipe? If 1/2" 6061 is strong enough to hold the redrive and prop
without fatiguing to failure, I'm surprised it wouldn't be strong
enough to hold my oil filter 8-)
Scott Gettings
Hi Scott, Check Bill's reply, I agree entirely because of the nature
of what the pipe thread is doing. About the redrive, remember those
bolts are NOT threading into the plate, they are passing thru and
getting a washer and nut applied..... totally different animal because
the plate material is being compressed by the tension in the bolt. Think
of it this way: when you apply torque to the bolt (or nut) the
bolt comes up against some resistance (the redrive case and mount plate
stack in this case) the bolt has no choice but to stretch minutely ( a
measureable amount if you'd like to measure it). This is bolt tension
and must be related back into the assembly somewhere.
*IF* the redrive
mounting plate were tapped then the tension force would try to pull the
threads out of the plate (strip the threads). Tracy calculated that
force and the available resistance offered by the threads in ALUMINUM
and determined thread failure was possible so he went to the next
available alternative: pass thru the plate and put a nut on the other
side. The nut has STEEL threads and sufficient engagement to provide
appropiate resistance to the bolt's tension and leaves the plate in
compression along with the redrive housing. This brief description
should also tell you NEVER use a bolt/nut combination where the bolt is
too short to project at least one full thread beyond the nut and it will
also help you understand why "crush plates" are necessary for wooden
props. With regard to the NPT just remember that you are driving a wedge
into the aluminum (the threads are tapered and thus cause a radial
outward force trying to crack the sides of the hole) so be as generous
as you can with the wall around the NPT, or consider using the straight
thread and o-ring style fitting -- it would be a better choice. Dave M
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