Silver Hawk cowl interference

I-MROB · #1 02-01-2007, 03:33 PM

Listers,

I am in the process of installing the FAB to the SilverHawk EX servo on a Lycoming O-360 B2B. (parallel valve vertical induction).

The FAB ended up very close to the left side of the lower cowl air scoop, but that was cured by fabricating a new mount plate and moving the whole FAB a little to the right.
I now have a minimum of 1/2" clearance between FAB and left side of scoop.

The problem is now with the servo mixture lever.
in the most forward position it is only 3/16" from le left side of the air scoop.
Doesn't look like much clearance!

Has anyone had the same problem?
Have I missed something?

Regards,
Roberto
RV-8 FWF

hevansrv7a · #2 02-01-2007, 03:58 PM

My mixture control arm was too close to the cowl, but I have a different cowl (SJ). The arm my engine came with was joggled. I traded for a straight one and gained additional clearance equal to the distance of the joggle. Without a picture, I'm not sure if that will work for you, but maybe it will help.

randylervold · #3 02-01-2007, 08:48 PM

Quote:

Originally Posted by I-MROB

The problem is now with the servo mixture lever.
in the most forward position it is only 3/16" from le left side of the air scoop.
Doesn't look like much clearance!

Has anyone had the same problem?
Have I missed something?

Roberto, did you get the "mixture arm inversion" option on your Silver Hawk servo? If not, you should.

More info...
http://www.romeolima.com/RV3works/FW...allforward.htm

I-MROB · #4 02-02-2007, 12:42 AM

Randy,
I have the standard configuration.
I was considering the alternate configuration, due to interference with the FAB, but was told to just make a 1" extension below the servo to bring the FAB where it would have been with the original carb. That took care of the FAB iterference, but I just didn't see the air scoop interference coming.

Not sure if I can change now!

Capflyer · #5 02-02-2007, 04:34 AM

I have a similar issue on my Mattituck TMX IO-360. The engine does not come with the Inverted Mixture Arm on the Silver Hawk and it is not retrofitable. I called Precision Airmotive and they said I could send it back to them and for additional $$ they could send me out the one with the inverted mixture arm. Mahlon at Mattituck suggested a spacer.

(Note to Mahlon, you guys may want to address this when you sell an engine for an RV)

I am about 3/4 done with my spacer that is 1" thick. Couldn't find for any reasonable price under $100 a delrin block to make it out of so I used a commercial cutting board which is made of a very similar material and is heat and chemical resistant.

Next week when it's done I'll post a picture of it.

There are some picutes on the Precision site geared towards this as well. http://precisionairmotive.com/

randylervold · #6 02-02-2007, 09:26 AM

I'm confused, what are you guys spacing off 1"? If you space the FAB down 1" it would likely hit the bottom of the intake scoop and also require the inlet to be at a really awkward down angle.

JonJay · #7 02-02-2007, 11:53 AM

I had the same issue. I ordered my engine "mixture arm up" or "reversed" but the straight short arm interfered with screws on the servo and the longer bent arm stuck too far out and hit the inside of the scoop.
I took the arm to a trusted tig welder and we cut and modified the arm to be short and joggle only about 1/4". Kind of like a smaller version of the stock mixture arm. Works perfect.

I-MROB · #8 02-02-2007, 02:24 PM

Quote:

Originally Posted by randylervold

I'm confused, what are you guys spacing off 1"? If you space the FAB down 1" it would likely hit the bottom of the intake scoop and also require the inlet to be at a really awkward down angle.

Randy,

the servo is 1" shorter than the carb, so putting a 1" spacer under the servo simply brings the FAB back down to its original place.

I-MROB · #9 02-02-2007, 02:38 PM

Ok guys,

thank you all for your help.

Today I found a solution that seems to work.
I tried mounting the rod end bearing from the mixture cable on the inside of the arm.
The throttle cable interfered of course with the servo during movement, but that was taken care of by moving the cable attach bracket 1/2" to the left.
I fabricated a bracket extension that will get riveted to the original bracket.
I now have smooth and clear mixture movement and the whole affair is more than 1/2" from the cowl scoop.
Very nice

randylervold · #10 02-02-2007, 03:28 PM

Quote:

Originally Posted by I-MROB

the servo is 1" shorter than the carb, so putting a 1" spacer under the servo simply brings the FAB back down to its original place.

That's weird, when I went through this I found that the servo was 7/8" taller than the O-320 carb and the same height as the O-360 carb (MA4-5).