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Cowl/Motor alignment

D

Dale B.

Member
I installed the motor in my RV12 and am now attaching the cowling. I found that the prop shaft and cowling are 3/8" off center. I checked, and rechecked my trimming of the cowling and it is exact. After much wailing and mashing of teeth, I measured the motor and found it to be off center. The front end is pointing to the left about 3/8". After pondering, with the aid of several beers, I remembered that the upper portion of the front landing gear did not mate flush with the firewall. When the bottom plate was attached to the bottom of the fuselage, the top section touched the firewall on the left side but was raised about 3/16" from the firewall on the right side. . . . I do remember setting it on the flat edge of the work bench and confirmed it was slightly off square. That was several months ago. I went ahead and installed the engine and tightened everything up and the gap disappeared. Now looking at it I see the firewall at that point is bowed out.

My guess is that the front landing gear was manufactured slightly off which is the cause of the problem.

My questions to the wise people on the forum: Has this happened to anyone else? Do I have to remove the engine to replace the front landing gear? Did I screw up the alignment forever by possibly bending the firewall when I tightened the motor mount bolts? Should I sell the plane and take up gardening?
 
Hi Dale,
I had the same issue with the front gear leg. Not even close to fitting properly. It appeared to be deformed from the welding process during manufacturing. I called Van's and requested a replacement. I would suggest you do the same. Regarding the firewall, see what it looks like after romoving the front gear before you panic. It will probably spring back to the original shape.

Sounds like they might have sent you my rejected front gear :)

Alex
 
Thanks Alex,

It is nice to know my problem and I are not alone in the world. My motor is in, plumbed and wired so it will be a pain to get the front gear off but it will be a project for this weekend. I kind of thought it would be a problem but I just didn't want to question Vans production. My RV-12 kit is so good, 99.9% of the time if it doesn't fit, I just stop and see what "I" did wrong.
 
Dale,
I guess things can go wrong at times. As a general rule with the RV-12 kit, if it don't fit, we screwed up somewhere. This case is a rare exception. Welding steel parts can result in distortion if the welding jig was not set up right, or the part was pulled out of the jig before things cooled properly. Further, there is some talent required, by tacking opposite sides of the structures before full welding to avoid "pulling" of the parts. Anyway, I understand it's going to be a pain to remove the front gear, but it's the right thing to do. Have a great weekend working on the plane. Trust me......it's worth it! I'm about three weeks past my first flight and having a ball.
Alex
 
Dale B. said:
I installed the motor in my RV12 and am now attaching the cowling. I found that the prop shaft and cowling are 3/8" off center. I checked, and rechecked my trimming of the cowling and it is exact. After much wailing and mashing of teeth, I measured the motor and found it to be off center. The front end is pointing to the left about 3/8". After pondering, with the aid of several beers, I remembered that the upper portion of the front landing gear did not mate flush with the firewall. When the bottom plate was attached to the bottom of the fuselage, the top section touched the firewall on the left side but was raised about 3/16" from the firewall on the right side. . . . I do remember setting it on the flat edge of the work bench and confirmed it was slightly off square. That was several months ago. I went ahead and installed the engine and tightened everything up and the gap disappeared. Now looking at it I see the firewall at that point is bowed out.

My guess is that the front landing gear was manufactured slightly off which is the cause of the problem.

My questions to the wise people on the forum: Has this happened to anyone else? Do I have to remove the engine to replace the front landing gear? Did I screw up the alignment forever by possibly bending the firewall when I tightened the motor mount bolts? Should I sell the plane and take up gardening?
Click to expand...

Dale,

Really love this forum...your timely post has probably saved me considerable time, sweat and....well several beers. My nose gear was also deformed (I, like several others assumed this was as should be).. Sterling verified mine was wrong; and they are shipping me a replacement with my engine!!:cool:
 
Hi guys.

I just bought a flying RV-12, completed five years ago. When we did the pre-buy, the cowling was off -- so I didn't notice until I went to pick up the plane that the spinner is offset to the left about 1/4 to 3/8 inch. It flies straight, but I can see the back edge of the spinner from the left seat. After finding this thread this morning, I now have something else to check the next time I am at the hangar.

It looks to me like the cowl is straight and the engine is canted left. Without measurements, though, it's hard to be sure. Are there points I can measure to determine where the misalignment is? I'm pretty sure the engine is off center (which would also explain the unusually large trim wedge on the rudder) but don't want to waste a lot of time chasing the wrong problem.

I'm thrilled to have an airplane to fly (once I get a few squawks cleared up), but man, after three years of building in my garage it's a real pain to have to drive to the airport every time I need to look at or do something - only to find that the tool I really need is still at home!!
 
Hi Dale B. This is Dale B (Dale Boorsma in Bakersfield, CA). A follow up to my post earlier this year, I remover the motor mount and front landing gear, checked everything, sanded and filed a few places and reinstalled everything assured that all would be straight. And *#&#!!! It wasn't! It was still of the same amount!! Now, I consider myself a relatively mild mannered guy but this pushed me over the edge. Luckily there was no sledge hammer within reach! In a hissy fit of rage, I grabbed the engine hub and gave it a couple tugs in the correct direction while addressing the innate object as if it were a Son of #*&%!! Low and behold it centered perfectly into the center of the cowling.... the clouds parted and the sun shown bright on my shiny little RV-12. Ok, before all my friends on this form begin to berate me, let me tell you, I am well educated and adhere to good engineering and logical principals. However, I have learned, after being married for 36 years and raising two daughters through adolescence, when the moon phases align no amount of logic, science, or advanced engineering technology can stand up to pure rage. Some times, life is not logical. . . go figure.
 
Dale B. said:
In a hissy fit of rage, I grabbed the engine hub and gave it a couple tugs in the correct direction while addressing the innate object as if it were a Son of #*&%!! Low and behold it centered perfectly into the center of the cowling.... the clouds parted and the sun shown bright on my shiny little RV-12.
Click to expand...

OK. I can certainly understand the application of a little bit of "mechanical adjustment". Has it stayed centered since then (and are you flying it), and did you figure out what moved? Something had to have moved. I wonder if there is enough free play in the bolts attaching WD-1201 to the bottom of the fuselage to allow the whole thing to move a little if the bolts are loosened.
 
Hi Dale,

The motor has stayed in place so far. I haven't finished construction as yet but everything seams to be ok for now.

Dale
 
Dale B. said:
Hi Dale,

The motor has stayed in place so far. I haven't finished construction as yet but everything seams to be ok for now.

Dale
Click to expand...

Dale,

I'm at the same point in construction....how has the fit up of your top and bottom cowl progressed? That is my next item on my 30 odd punch list work off list.
 
Think

I'm glad that you 'solved' the problem but I sure would like to know what changed when you yanked the engine. Please let us know what you find!

For sure, something moved and if no tightened up (or re welded), it may cause your airplane to be unairworthy. Not criticizing just sayin....
 
Hi Ric,

The two halves of the cowling matched up fine and attached to the frame nicely. I did cause the bottom cowling to distort some when I attached the cooling air duct to it. I am working on repairing that now.

E.D.,

For the life of me, I don't know what really moved if anything other than the frame itself bending a little or things just shifting into place. I can't tell any difference other than it is now straight. Like the other Dale wrote, it may have needed just a little "mechanical adjustment". I believe a very, very small movement at the firewall will make for a much bigger movement at the hub. All four bolts are torqued correctly. As to what really happened, I don't know, except it is OK now.
 
Although I am not a man of the cloth I do believe the laying on of hands can have miraculous results as you have proven!😜
 
Tonight my son wanted to see my new toy, so we went over to the hangar where said toy is sitting, un-cowled.

I found that I can give a firm tug and move the engine to the right to where it will align nicely with the cowl. It's not loose, but it will move. It won't stay there; it moves back to its original position when released -- to me it acted like a rubber isolater with not enough bolt torque. Anyway, I tugged while he looked for movement. Then he told me where to look and he tugged while I looked. The upper right bolt attaching WD-1221 to the firewall looks OK at rest, but seems to have not been properly torqued. There's a castle nut and cotter pin, but I can get s good millimeter or so of movement. We'll see how fixing that affects things.

So, "other" Dale, you might check the bolt torque again. I know I plan to re-torque all of them, just to be on the safe side.
 
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When I mounted my nose gear I also put in a couple small bolt on the FW to keep it from flexing when I raised the fuse. I did notice a slight offset but was able to get a couple bolts in. I don't have anything past the nose gear but I suspect there's a mount and drilling out for bigger bolts.

Can anyone tell me if they believe they noticed the gear deformation when they just mounted it. Sounds to me from the replies it was noticeable when mounting up the bottom of the gear.
 
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