Nose gear attach bolt, hole in firewall?

[mark donahue]

We were just installing the engine mount to the firewall and looking at the plans and noticed that they call for a hole to be drilled in the firewall to allow for the nosegear attach bolt to be installed from the backside. One place on the plans calls for a 1" hole and another calls for a 3/4" hole, but the thing is that the bolt can go in from the front/top just fine without drilling any hole. What have you guys done? Is there some sort of interferance with the exhaust system or something that makes installing the bolt from the front/top impossible with the engine installed? Even so, I don't really see any reason I'd ever need to remove that bolt unless the gear was damaged. I don't like the idea of drilling any more holes in the firewall than I need to.

Thanks for the help.

 

[plehrke]

If it is like the 6A then there is not enough room for the nut and the bolt tail (2 threads past the nut) for it to be on the bottom.

I never planned for the nose cross bolt to be removed (no hole in the fire wall) and now regretting it as for the nose gear service bulletin I need to remove the nose gear leg and to do so will mean pulling the engine off the fire wall to get the cross bolt out.

The best advise is to assume every thing will need to come apart at some time in the life of the aircraft. It is called design for maintainability.

 

[LifeofReiley]

On mine there was no way to get the bolt in from the top without the hole. I used a 1" hole and the stainless plug that comes with the kit sealed in place. Some are putting the bolt in from the bottom with locktite on the threads.

 

[mark donahue]

On mine the bolt will fit in from the front/top and if I put a washer under the head of the bolt it won't hit the firewall, so I think there will be 2 threads or so remaining above the top of the nut and it won't hit the firewall.

Did you put the bolt in from the back/bottom without the hole? is that why you have to remove the engine to remove the gear? Can you just drill the hole now to remove it?

 

[Greg Arehart]

Mark,

On my 9A, I drilled the hole in the FW but don't think I really needed it. If you can get the bolt in andout without the hole, my advice is don't drill the FW. Or you could put the bolt in from the bottom (as noted by others) and use a castle nut on a drilled bolt to assure yourself that it won't drop out unless you want it to do so.

greg

 

[Pilottonny]

Position of the hole, per plans, was not OK !

I drilled the hole per plans, but was not able to install the bolt from the bottom anyway (misallignment). So I installed the bolt from the top and made a special cover with a "bulge" in it, to clear the nut.

Regards, Tonny.

 

[plehrke]

Did you put the bolt in from the back/bottom without the hole? is that why you have to remove the engine to remove the gear? Can you just drill the hole now to remove it?

Yes. in from the bottom with no hole. Putting the hole in now maybe an options but the bolt head on the bottom is so close it will be difficult drilling the stainless. Another option is to remove the nut on top/front, let the bolt drop down a couple thousanths to get space between the mount and bolt head, and cut the bolt head off. Then remove the bolt from the top.

 

[panheadmark]

No hole in mine......

On the advice of one of our tech guys I did not drill a hole in my 9A firewall but instead used a ball peen hammer with a block of dense foam on the back side to put a "recess" in the firewall. There's just enough room to make it fit.

Mark
RV9A
Getting close

 

[rvbuilder2002]

On the advice of one of our tech guys I did not drill a hole in my 9A firewall but instead used a ball peen hammer with a block of dense foam on the back side to put a "recess" in the firewall. There's just enough room to make it fit.

Mark
RV9A
Getting close

That works, but if you ever have to remove the leg after a few years have passed and it is frozen in, you will have a very difficult time getting the bolt out (compared to just tapping aft on it with a punch).

Someone else mentioned using washers under the bolt head to space it fwd and prevent interfearence with the firewall...be very careful doing this. The bolt shank needs full penetration of the motor mount socket to help prevent the leg getting loose in the socket.

 

[Rick6a]

An Alternative

.....if you ever have to remove the leg after a few years have passed and it is frozen in, you will have a very difficult time getting the bolt out.......

It is fair to assume Scott has real world experience dealing with this issue and knows better than most what he is talking about.

I shaved a few bolt threads in an angle to assure positive clearance with the firewall. After a few years of operational service, I did have to remove the leg to comply with the SB. The bolt came out just fine. I figure if at some point the bolt does get frozen into place, long before I would consider loosening the engine mount, I will access the area from between the rudder pedals, cut in a hole per plans, tap the bolt free, then go with a SS plug from that point on. Sounds easy to do on paper, likely to be a PITA in practice but I'm betting I'll never have to go there.