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Savannah Motor Mount Question


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I have a question on how the motor mount attaches to the lower aluminum angles on my Savannah S.   The lower motor mount bracket is L shaped and it is supposed to attach to the aluminum angular.  However, the aluminum angular has two rivets attaching it to the forward end of the cabin floor.  Am I to get the L shaped motor mount as tight as possible and drill the bolt hole so that it is tight up against the rivets or am I supposed to remove the rivits so the the L shaped motor mount is tight to the aluminum angle? Thank you.  -steve 

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Hi Bodie.

The manual certainly doesn't spell it out. It made no sense to me to be bolting steel down onto raised rivet heads.

I certainly removed the very front rivet.

I'm pretty sure I filed a small scallop into the rear of the steelwork to clear the second rivet back.

I'll have a look when next out to the hangar, but it could be a couple of days: the weather is no good here at present.

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Later: when you put those bottom bolts through, you will use the 6x24 'penny' washers provided on the inside.

I clearly remember filing a scallop in the edge of the washers to clear that second rivet back. So my second rivet back remained in.

 

The first rivet would definitely have been removed. Which is fine: it is holding the angular extrusion (and bottom skin) to the firewall. Since the engine mount is bolted to both the angular extension and the firewall at this point (so holding them together) the rivet is not required.

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If it were me, I'd remove both rivets.  The steel motor mount is held on with AN bolts so the strength from those would be greater than the first 2 rivets anyway.  If you feel you need that second rivet then I'd move it so it clears the engine mount.  

But your best bet would be advice from the manufacturer, if in any doubt.

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Yep  flick those 2 rivets..the strength is the bolt through it..and a wide washer is needed as well on the inside on the floor. If I was at home I could post a pic of the sav version but I am away for another 5 days

 

 

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Thanks guys!  I appreciate the help.  In most places the instruction are excellent, and in some places, less than stellar.  It seems that there is so much that depends on the cabin being tied correctly to the motor mount through the firewall. 

I'm just pleased that I finally got my firewall forward kit. It was a little over a year process as Covid shut Italy down for quite some time.  Glad to be back at it!   

 

-steve

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Hi Steve

which holes did you drill first? I am about to do the same thing, Ive squeezed up the skin around the firewall and will rivet that in place before going for the engine mount, Does the top mounting plate line up with the cabin frame? I assume so but haven't tried it yet. I also have a mass of bolts and washers with no way of identifying which to use here, did you get a set of decent instructions or is it the standard "attach the motor mount using bolts" 

Thanks Richard

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Posted (edited)

I bought my kit in two parts.  The fuselage and firewall forward (motor mount, motor, guages etc).  The motor mount bolts and washers were in the firewall forward kit in a separate bag.  

After removing the two rivets on each side of the aluminum angulars as recommended by folks in the previous posts, I held the front of the fuselage down at the lower nose gear bracket, then lifted the motor mount up with a cherry picker while pulling rearward on the motor mount with a ratchet strap attached to the main gear.  By pulling the mount rearward I actually moved the hole I was to drill almost 1/4 to 3/8"  (I'm a Yank) rearward.  I pulled the lower motor mount brackets as inward as possible to the aluminum angular.  I drilled the bottom holes first (they ended up being almost exactly between the two rivets that were removed.  I then drilled the lower firewall holes.  I then went to the top holes to align the front cabin frame to the motor mount.  The motor mount actually had to be "stretched" about 1/2" to properly mate up with the cabin frame.  The middle holes were then drilled without any adjustment.  It seemed to me that pulling up the bottom first by putting those bolts in tension made sense, and if I had drilled the middle holes next I wouldn't have been able to properly align the top holes with the cabin frame bracket.  Hope this helps.     And, I got the same instructions...."attach the motor mount using bolts".

Edited by Bodie
forgot something
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I got the internal support brackets fixed and they seem to be ok. the rest of the photos show the lower engine mount brackets just held in place and an upside down shot of the upper bengine mount bracket. It seems to fit ok.....

 

 

 

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Found three bags of bolts that seem to be for the engine bay The end one os what I think is the right order for the engine mount. AD3F03B1-BACD-4D93-9DB6-FFDF592DF7C4.thumb.jpeg.2c4e9059e2c514b2ce4c49ace559195b.jpeg42C938C7-8DFE-4188-BDA3-2FE43364DAA1.thumb.jpeg.bdad312f6bb9e431b834520cf480b523.jpeg28F4EEDA-F4C1-46B6-813B-B4E9A376A34B.thumb.jpeg.09aaf6a1cdda72c2478168ad4ffcacdf.jpeg441F5B0C-DA50-4BCA-BBFD-9BC1BE1C8C07.thumb.jpeg.160685ac60e1cdf2a729ba1bf5664192.jpeg

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RMorton, the hardware.....nuts bolts and washers......are identified in the list of materials at the start of each chapter. Measure them to locate the correct ones. The AN# is the diameter of the bolt in sixteenths of an inch and the ##A suffix is the length, in eighths of an inch. So AN4-06A is 4/16" diameter, 6/8" long, or 1/4"diemater, 3/4" long.

 

5 x AN4-06A bolts

2 x AN4-07A bolts

2 x AN5-17A bolts

Nylock nuts and washers to fit all those, plus 6 x 24 penny washers.

 

The instructions are less than clear, but the order of assembly is as per the order of illustrations etc in the manual:

1. Bottom mounts.

2. Top mount.

3. Side mounts.

 

The top mount is pulled into place as you tighten the bolts. I used cheap overlength bolts to start pulling this into place, then replaced them with the correct aircraft bolts.

 

Once all this is in place, you will find that the underside of the front fuse, including the extruded aluminium angles, is now curved.

 

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By tying the fuselage down I was able to get the lower L shaped bracket pulled up tight with a lift and pulled back tight against the firewall (first pic)...

 

I was then able to pull it tight to the aluminum angle (second pic)...

 

Third pic is where the top motor mount lined up for me in conjuction with the lightening hole.  At this position it matched the cabin frame.  Notice the arrow pointing to the test hole that was wrong...(just another lightening hole now....

 

The middle holes were a breeze!  -steve

 

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As an alternative to tying the fuse down:

I predrilled the top holes  by pulling the cabin steel to the firewall with a clamp and block

I hung the motor mount on the fuse with light strops, to hold it there while I worked on the bottom mounts.

I then pulled the top mount together with cheap longer bolts, then replaced them with the correct bolts.

(Note: the pics show clekos, but all rivets were in before final fitting of the engine mount).

 

 

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That reassures me greatly! I am now confident that it will fit and with plenty of checks it might even be square! I have postponed the installation of the frame nd motor mount to re-organise a little as I was struggling for head room and space. Should be back to work (sadly day job as well) next week. Many thanks gents The pictures are fantastic

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Not sure if I put this in my original XL blog. But obviously I did this again with the rebuild. The two bottom mounts on the engine mount first than did them up. I just used some straps on the top of the mount to pull it to the firewall. Then once it was nice to the firewall and dead centre of the vertical alu support I drilled the top holes from the engine mount side at the top. I then fixed it temporarily with 2 bolts and drilled the middle ones into the steel support brackets. I then pused the cabin frame front up to meet at the tops and used longer sts boltes to pull the cabin frame to the motor mount. Only took me 30 mins or so. It helps of course if you have done it more than once 🙂

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