Ken Powell wrote:

Hi Paul,
I need a little engineering help.  I have settled on an engine mount system
like you have drawn on your web site for the RV-4, which uses what I think
you have previously referred to as the Questair mount, in which the forward
motor mount tube passes through the pan.  I am going to build a new oil pan
around this system.  My questions are:
1.  What thickness of 6061 aluminum would you recommend for the oil pan?
2.  What size aluminum should the pan rails be made?
3.  How thick and what diameter would you use for the forward motormount
    tube?

1. Use 0.050 minimum for body and rails. 0.065 would not hurt and would be 
easier to weld. Reinforce the pan in the area of the aluminum tube with doublers.

2. The pan rails doubler can be 0.125 as they will not weigh much and they
do not have to be welded on. Just something to stiffen it between
bolt holes so the gasket does not leak.

3. I would make the 2-1/4 inch OD aluminum tube part .125 wall and 
the two inch OD 4130 tube long tube 0.049 4130. Depending on the length.
Since yours is an RV4 I would guess the length about 16 to 18 inches. 
 

My backup plan is to build the pan from 4130 sheet.  I can oxy/acc weld .030
steel sheet, but learning to oxy/acc aluminum for the above mentioned plan
may be a problem but I want to give it a try.  So, I have the same questions
as above except for 4130 steel.
1.  What thickness of 4130 steel sheet would you recommend for the oil pan?
2.  What size 4130 should the pan rails be made?
3.  How thick and what diameter would you use for the forward motormount
    tube?

Makes more sense for such a short motor mount 4130 tube.
1. 0.035 4130 for body and rails is fine if you can weld that.
2. The pan rails can be cut from .125 aluminum as they just stiffen the 
steel between bolt holes.
3. 0.049 with .035 doublers around the tube where it is welded into the pan.

Two more  questions.
1.  If you were to make the rear motor mount that you presented last week
    out of 4130, what thickness would be needed?
2.  Just how thin a material could a oil pan baffle plate be made if you
    are using 6061 aluminum?  By this, I mean the plate that bolts between
    the oil pan and the engine that is supposed to give the oil time to lose
    the air bubbles.

1.That's a tough question as the design relies on the bending stiffness of
the 1/2 aluminum plate. That half inch plate also happens to be the thickness
the Barry Mount rubber bushings need. Making it out of thin 4130 would be a 
complicated job.


2. Another tough question as you are dealing with possible vibratory modes
that may crack the plate. On the other hand a few cracks would not be
fatal. I would guess .065 might be OK.

Thanks for your help,
Ken Powell

 
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