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RockEight Engine Mount

G

GR8 8

Member
I'm hoping for a little help from the forum on a design issue.:confused:

Essentially it is a Super 8 design, but with the engine moved a little further aft than what has been done so far. So no-one makes a mount that will accomplish this for me. In designing a mount, I see Van's stock RV8 mount uses a 3/4" offset for torque. A Cherokee 6 that I measured with a 300 Hp Lyc uses about an inch when measured at the same location... Does anyone know what the Rockets mounts have dialed in for torque? A measurement of where the case halves parting lines would extend to the firewall (relative to the engine mounts) would be a big help.:D Thanks.
 
I've been told....

Can't verify this but have been told by the powers that be that the F1 evo Rocket has zero offset..... much like a P51 :D
 
well, MAYBE!

gstone said:
Can't verify this but have been told by the powers that be that the F1 evo Rocket has zero offset..... much like a P51 :D
Click to expand...

Hey Greg:

I had a quick conversation with "The Powers that Be":

The 550 mount, like yours, is straight; the Lyc mount has offset. I see very little difference, except the 550 needs less left rudder in the descent. Fin offset and rudder tabs do not seem to be needed, but the F1 rudder lets the owner tune the rudder itself to set the ball in the middle.

Why put the engine in straight? The answer lies in this question: why would you vector your thrust? Does it make the ship faster? Reno participation has taught me a few tricks, including the statement "I have never seen an idea so good that I couldn't copy it." A couple of Glasair drivers straightened their mount, and picked up a fair amount of speed. So, since that seemed like a good idea,...

BTW the Cirrus 550 is also set straight; the 360 powered version has offset. I did not know this until after I had already started down the 'straight' path.

I can see a bit of down angle (1/2 deg or so) for what we know as 'proper' prop rotation direction....this seems to reduce the propeller effect during maneuvering, as North American found with the P-51A.

I hope this helps!

BTW GR8 8: do a bit of math regarding the firewall 4130 weldments, so you keep that big ol' engine and prop attached as intended! Might have a look at the .032 skin too, assuming you want to keep the original G rating. One change begets a few more...

Carry on!
Mark
 
RockEight Mount

Thanks gentlemen! I've got the firewall lugs built and the Lord mount lugs made as well. I'll be lining up the engine and fuselage in a week or two and connect the dots. Thanks for the help. Mark, we modified the top skin to .040" and added a fifth lug in the (top) center of the firewall as well. Hoping to keep that big engine in front of me.
:rolleyes: Hmmm... Sure makes it easier to make the mount straight... I've talked to a couple of aero engineers on this, and both said any offset is a guess. So, your experience with both ways of setting the thrust angle is the best info I've got. I'll post some photos in a week or two. JR
 
Got 'er DONE!

Finished the engine mount last week and installed it. It turned out a couple pounds heavier than hoped at 8.4 Lbs. Better two pounds too heavy than one once too light though.... Photos attached.
542DE798.jpg.html

http://s1281.beta.photobucket.com/user/Gr8-8/media/Snapbucket/E1736FE8.jpg.html
http://s1281.beta.photobucket.com/user/Gr8-8/media/Snapbucket/D208D796.jpg.html
http://s1281.beta.photobucket.com/user/Gr8-8/media/Snapbucket/88BF41B5.jpg.html
http://s1281.beta.photobucket.com/user/Gr8-8/media/Snapbucket/C3384F50.jpg.html
http://s1281.beta.photobucket.com/user/Gr8-8/media/Snapbucket/603FC512.jpg.html
http://s1281.beta.photobucket.com/u...4-F5E2CFE876AB-9232-0000111DE333EB1C.jpg.html
 
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