gear leg bolts through engine mount

[wingnut99]

I have my motor mount with the gear legs mounted on my Waiex and today I have everything measured and the toe in set and all the measurements are on target and I decided it's time to bolt the legs into the mount.
According to the plans the bolts go through these little extensions on the mount and pass through the legs and out the back. Problem is that the front member of the mount is in front of the nipple that the bolt goes through and it's too close, maybe 2" away, to allow the bolt to enter from the front let alone be able to drill through it to locate a spot on the leg and remove and drill it.
This no doubt various with models and engines so has hanyone out there with a B model with a 3300 Jabiru run across this situation? I can install the bolt from the rear and make a access hole in the firewall for removal later if needed but trying to drill through the mount from the rear and ending up with the hole matching up with the 1/4" diameter nipple on the front seems like a long shot. Thanks for your help.

[GordonTurner]

Just getting to that shortly on my Waiex, which is a classic with Corvair motor mount...so not too much in common. Haven’t studied that part of the plans, but is it for definitely sure that the bolt goes through those 1/4 inch extensions?

[sonex1566]

For some lucky fluke I didn't get caught out by this, but I did do mine the reverse of the way you're doing it. Can you put the top bolt in first, then set your wheel alignment and mark holes at the bottom? Trying to drill the holes through the titanium legs by hand is hard work. Those spigots on the mount reinforce the holes to help stop the holes getting chewed out over time. Remember to keep your fingers crossed while drilling the final holes in your drill press. Good luck.

[wingnut99]

Initially I put the gear legs in the mount and the assembly fit right on the firewall once I had obtained the correct bolts, the top and bottom both required the same length which were a 1/4" shorter than the 2 that came in the hardware kit. After putting the axles on and aligning them with each other and setting the toe in with the collars I was able to measure from my straight edge up to the lower longerons and determine how much more I needed to drive the legs into the mount. I pulled it off and made the adjustment and test fitted everything again. Now I have it disassembled to drill those gear leg bolts. Sounds like there's no perfect way to do it. I've marked them as best I can. Guess we'll see how close the first hole is.
FYI, I discovered a good technique for installing and removing the legs. Initially I ised a 5' bar/pipe clamp which was a lot better than beating them in but yesterday I tried using a pneumatic rivet driver and it buzzed them out of there in nothing flat. I had to use a brass drift punch inside the mount to push it through but it worked well. Thanks for your help.

[sonex1374]

...[snip] Problem is that the front member of the mount is in front of the nipple that the bolt goes through and it's too close, maybe 2" away, to allow the bolt to enter from the front let alone be able to drill through it to locate a spot on the leg and remove and drill it.

I only have direct knowledge of the legacy mounts, so this may not apply to your B-model mount. The cross tubes are indeed close to the gear leg bold guides (...the nipples you mentioned), but they are offset just a bit so as to allow the bolt to slip by them. It's possible the mount may have been fabricated incorrectly if the cross tube is truly blocking the bolt path (worth double checking). As for drilling the gear leg thru the guide, you'll need at least a 6" long 1/4" drill bit to make this work, and maybe a bit longer if you can find one. This is one of the toughest things we have to do on the landing gear, but sharp cobalt bits, lots of drill lube, frequent stops to clear chips and cool the bit, and patience will get the job done.

Jeff

[richd]

Anyone ever figure this out? I can't drill from the front side because the bar is right in front of the hole.
Some how you need to drill from the back side and perfectly line up with the hole on the front.
I came up with this tool but, but not sure how well it will work. The bolt hole has to be perfect.
Any thoughts on how you all did this. I have a B model and a Jabiru engine mount.
Is there a tool you can buy to make a hole like this line up from the back?
I will have to test this jig tool out on something other then my engine mount.

[Zack]

I took a bolt and center drilled a #30 hole on the lathe and used this bolt as a drill guide. I repeated this process with larger drill bits until I was ready to final drill. You need to use a 90 or 45 degree drill. You can look up the NAS bolts for a short thread version to leave space against the firewall. I have a Rotax mount so I think I have some more space than you. You could use this method until the drill bits become too long to fit in the space you have available, this should give you a good pilot hole to updrill. I would find someone with a milling machine to do the updrill in this case. The force you need to use on the titanium will likely cause the hole to move or oval without a jig.

[richd]

Thanks, but I don’t have that kind of space for and angle drill.
Kills me that no one has invented a low clearance 90 degree drill.

[Zack]

You can buy 45 and 90 degree drills. https://www.yardstore.com/pneumatic-and-cordless-tools/pneumatic-and-cordless-drills/pneumatic-angle-drills/new/sioux-90-deg-angle-drill-1am1551
Use the longest AN4 bolt that you can fit in that available space to use as a drill bit bushing. The drill bit length will be your limiting factor

[Bryan Cotton]

Thanks, but I don’t have that kind of space for and angle drill.
Kills me that no one has invented a low clearance 90 degree drill.

https://www.yardstore.com/nsearch/?q=pancake+drill

A pancake drill and a short bit works well.