Wednesday, June 15, 2016

Rethinking Lower Coolant Hose's Adel Clamp Mounting

Frequent readers of the DOG Aviation Blog may recall a photo on a previous post showing the parts that would be used to support the Adel clamp for the lower coolant hose that would normally be screwed into the nose gear weldment. However, because of the missing hole in the nose gear assembly, the idea to use a hose clamp with a screw welded onto it seemed like and easy fix … but during a trial fit to determine the position for the screw initial measurements, it was discovered the hose clamp was being knife edged by the edge of the hole in the gear weldment. I guess a half moon shaped rounded insert could be placed in the hole to prevent the sharp edges of the hole from cutting into the hose clamp … but that seems like a lot of extra work.
Hose clamp with a stainless screw welded onto it. During the initial trial fitting it was discovered the sharp edges of the lightening hole in the nose gear weldment was creating a knife-edge situation. The point my finger is pointing to is beginning to developing a crease and the clamp was not even really snugged yet.

Even though the above method would work  for installing the Adel clamp, I fear over the long term it will likely become a point of failure, so another method was devised. The lower portion of the nose gear weldment that attaches onto the bottom of the fuselage has a couple of tooling holes that look promising as a location to support a bracket. Unfortunately, the tooling holes are quite large so very precise measurements were made so a bracket could be fabricated from bar stock that would allow a much smaller 10-32 screw to just catch the forward edge of the tooling hole while the aft end of the brackets sits snug against the fuselage skin thus preventing fore and aft movement. On the bottom side of the nose gear weldment, an oversized washer or piece of bar stock will be used to span the hole so when the mounting bolt or screw is tightened, the bracket will become sandwiched to the nose gear weldment.  Below is a photo of the new bracket. Note: the bracket will NOT be installed at the location shown in the photo … the left side as shown is just for camera access. The actual mounting location for the bracket will be using the other tooling hole on the right side of the gear weldment between the gascolator and nose gear tubing … which is a low point for the coolant hose so that location will offer the most support for the hose.
A tooling hole in the base of the nose gear weldment will be used to mount the bracket for the Adel clamp. Note the bracket was placed on the left side of the gear weldment just for photographic purposes … the bracket will actually be installed on the other side of the gear weldment adjacent to the gascolator which is the low point for the coolant hose. So that location should offer the most support for the coolant hose.

Mounting the Adel clamp to the base of the nose gear weldment will mean the coolant hose will be taking a little lower path than it normally would, but fortunately there is still an abundance of clearance. The hose will still need to be raised up to get on the Adel clamp which means the Adel clamp will be offering strain relief and support for the coolant hose. Now all that is left to do is prime and paint the bracket and close this chapter of the build.