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Landing gear mount. 25-3

M

mciaglia

Well Known Member
This may have been covered in a previous thread but I searched quite extensively and couldn't find anything. I seem kind of stumped and was looking to the experts for some advice. I followed the steps outlined on page 25-3 of the fuse build exactly. I temporarily mounted the landing gear amount after final drilling the top row of holes with a #12 drill. I used the F drill bushing, a #30 drill followed by removal and final drill with a #12. When I go to remount the WD-1021 the holes don't exactly line up and it's **** near impossible to pass an AN-3 in any hole.
What am I missing?
The mounts are not warped as some others builders have encountered.
Do you match drill once it's all on?
I can't even imagine installing this with all the skins surrounding it

Thanks in advance for any help
 
After I drilled each hole with #12 bit, I put in a bolt with a bit of grease and let the threads help "pull" the bolt thru the hole and then I would drill the next hole to #12 size. (I will need to throw away most of these bolts.) So I drilled one hole to #12, installed a bolt, drilled next hole to #12 installed a bolt until all were done. I tried to start drilling in the middle of each pattern of bolt holes and drilled one hole to left then one hole to the right, etc..

Not sure if any of this will help if all holes have already been drilled to #12 size. Try the bolt with a bit of grease and driver on electric drill, the bolts may pull the weldment into place?


Steve
 
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I have found a #12 reamer cleans out the holes after drilling. If the holes do not line up make sure you have not mixed up the left and right.
When you do the final install it is a challenge you will need small hands to reach those bottom nuts.
 
Do you have any pics? This step is pretty straight forward so misalignment of the match drilled holes is peculiar. IMO you shouldn't need to ream or use grease to get the bolts to pass through.
 
At this point, reaming is probably your best bet. If the hole misalignment is great, you might be wise to start over - possibly weld the holes you've drilled and try again.

For those that haven't gotten to this step, here's how I did it and no problems lining things up. First, since I knew I was going to be removing the mounts several times, I used #12 clecos at the top of the mount. If this doesn't seem secure enough for you, use bolts with wing-nuts for speedy removal. Second, make sure the tabs you will be drilling are clamped to the spar. Back-drilling through the bushing can push them out of alignment. Drill a hole, remove the mount, enlarge the hole, then replace the mount with a bolt in the just-drilled hole and do the next one. Repeat as needed. Resist the urge to drill all the pilot holes at once.

When enlarging the pilot holes, use a drill press. Drilling free-hand invites chatter and misalignment. Before you clamp the mount for drilling, use the drill bit to center the hole - Bring the chuck down until the drill is touching the pilot hole and turn it by hand to center it. Once the hole is centered, clamp it and then drill normally using lots of cutting oil. Eyeballing the work for clamping is no good and the drill press will pretty much ignore your pilot hole if you haven't centered it.

I was strongly tempted to use the pilot bits I had used for the mounts in my RV-6A project. I think they'd work fine but in the end I followed the instructions.
 
Here are some photos
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This is a noodle scratcher. Was the drill guide loose in the hole or so tight that you couldn't insert it very far into the hole? I ask because assuming you bolted in on exactly the same way at the same locations and there is no fit interference anywhere (like where you had to trim the center section lower flange), the only thing I can think of is the #30 pilot hole was drilled slightly off center due to misalignment of the drill guide in the center section holes or if you didn't clamp the tab down, the bit pushed it out a bit while drilling causing the hole to be a bit offcenter.
 
Todd,
The drill guide was super tight as well as the #30 drill in the guide. I actually spun it on my 6" scotchbrite pad to get it to fit. In the pic it hadn't pushed it all the way in yet. I didn't clamp the small attachment point when drilling, but went slow and let the "drill do the work" instead of muscling the drill with pressure. Even if it did push it away won't the holes be lower not higher? I think if I clamp the bottom portion in the same way when I drilled it it will line up, but I don't think that will work when its time for final install.
 
mciaglia said:
Todd,
The drill guide was super tight as well as the #30 drill in the guide. I actually spun it on my 6" scotchbrite pad to get it to fit. In the pic it hadn't pushed it all the way in yet. I didn't clamp the small attachment point when drilling, but went slow and let the "drill do the work" instead of muscling the drill with pressure. Even if it did push it away won't the holes be lower not higher? I think if I clamp the bottom portion in the same way when I drilled it it will line up, but I don't think that will work when its time for final install.
Click to expand...

The misalignment doesn't appear huge -- maybe you could use a drift to get the holes aligned. In any event you might want to give the mothership a shout and see what they think. Wish I had better answers.
 
Spoke with The Mothership....they recommended drift pin and not being such a weakling. Get the rubber mallet out.
 
TomSpencer46 said:
Remember you are not building a solid gold Rolex
Click to expand...

Generally good advice but this is one of those areas where you want as good a fit as possible. A sloppy fit here will allow those bolts to 'work' on every landing or even every bounce while taxiing - not what you want for long term peace of mind. Same for the leg to mount attachment, which is why the instructions are so exact about how to do it.
 
Take one of the AN3 bolts and scothchbrite wheel the threads off of it to make a smooth slightly tapered alignment pin...worked for me
 
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