Rotisserie Hardware Finally Arrives

 I finally got my hardware that I ordered about a month ago. COVID sucks. Bad weather - the worst snow storm of the year that the news media said would only amount to 5 inches that turned into 15 - also sucks. Then there is UPS, but I digress. I guess I should just be thankful that I got anything at all.

The list is as follows:

50  NAS1352-08-8P 1/2 inch socket head cap screws - to replace the Vans pan head screws used to attach the access plate to the inboard fuel tank rib to make it easier to service/remove/replace with the tank mounted on the plane. 

50 AN960-8 thick washers for the above screws

50 AN960-8L thin washers in case a thin washer is required for proper screw depth

4 AN7-11A 7/16th inch thick bolts to potentially replace the metric bolts that came with the engine stand

4 AN8-11a 1/2 inch thick bolts that should fit the hole in each spider arm a bit better than the AN7s will. I bought both so I could choose which one I would like to use.

4 AN 960-716 thick washers for the 7/16th inch bolts

4 AN 960-716L thin washers in case those are needed for proper fit.

4 AN 960-816 thick washers for the 1/2 inch bolts

4 AN 960-816L thin washers

4 AN3-7A 3/16th inch bolts to firmly attach the angle to each spider arm I already have enough washers and bolts from my previous order for these bolts so I did not need to order any more of those.

4 AN365-720A Nylon Lock nuts for the 7/16th inch bolts

4 AN365-820A Nylon Lock nuts for the 1/2 inch bolts

The primer had to be back ordered - apparently until April sometime. Oh well. The plus side to that is that I will be reasonably assured that the 2 year shelf life will still be in tact, instead of already being expired or close to it as usually happens. Here is a pic of the hardware:

The steel angle will be attached to each spider arm, and while the big 1/2 inch sized hole allows for a large heavy bolt to be torqued down against both parts, there is still a possibility that the parts could shift while rotating the fuselage, and that could spell disaster. TO ensure that this does not happen, one more hole needs to be drilled into the spider arm in between the lug on one end and large bolt hole on the other, so that one more bolt can be added to secure the angle to the arm and prevent it from turning. Most have used a small AN3 bolt for this, and at 122,000 psi tensile strength (AN hardware specs) I am not concerned about shearing any of the smaller AN3 bolts used in this assembly.  

The next step was to set up the drill press to drill the additional hole in each spider arm, and then I can use that hole as a guide to match drill the hole in the angles once I cut those to size. I used a 3/16th inch metal drill bit, and set the belts on my drill press to 990 rpm per the recommended setting for drilling mild steel. this is much slower than the 3100 rpm commonly used for wood. Drilling metal builds up heat very fast, so keeping the drill bit and the work piece as cool as possible is important. 

I measured the distance between the edge of the lug and the edge of the bolt hole and more or less split the difference, so that the new hole would be about half way between the edges of both holes. This turned out to be  about 1 11/16th inches or so.

The white powder in the following pics is Boe-lube that I sprinkled on the drill bit and in the hole of the spider arm. It is a Boeing product that is very much like candle wax but probably has some other stuff in it. It acts as a coolant and lubricant and is highly recommended when drilling into metal.

I used the straight edges of pieces of masking tape and a sharpee to mark the center point of each each hole, then marked it with my center punch so that the drill bit would seat properly. Then ot was just a matter of playing the drill table and vise to get it all lined up properly.

The holes in all 4 arms came out pretty well, and the drill bit plowed through the steel with ease as I slowly lowered the quill. You drill a little and then back it off, then add some more boelube if necessary, and do it again until the hole is drilled completely. The above pic was the first hole that I did not line up quite right, so it is a little off center. The other 3 are much better. If I need to drill another hole in this one later on I will do that.

And finally a trial fit with an AN3 bolt just to check the fit in the new hole.

This is not the same bolt I will use to attach the angle to each arm - it was just handy so I used the super long one just to check the fit.

Finally, after I was done drilling the 4 new holes in each arm, I noted something strange on my drill press. IT has a laser unit, and on the side as shown in the next pic I noticed that the locking ring screw post that is mounted to the edge of the laser unit was slanted to one side. as I moved the quill I could see it change from being off center to moving back to straight vertical. As I repeated this several times I noticed that it was the entire laser unit that was moving. There is a set screw in the back of the unit that secures it to the drill assembly. Sure enough, as I put my hand on either side of it I discovered I could move it from side to side. Not good. 

So I grabbed an allan wrench and tightened it down a bit and verified it no longer moved from side to side. I had been wondering why my laser lines always seemed to be off target during my latest drilling sessions, and now I know why. If you look just below the silver part of the press where the center of the laser unit is positioned, at the small black flange just above it, you will see that it is at an angle. The laser unit should be sitting in this flange so that it is completely level, and obviously this is not the case. A couple turns of the clamping screw took care of that problem. I guess it had come loose after many years of vibration and use. Glad I solved that problem.

Next steps are to cut the angles to size and drill the required holes on both sides. then I will finally be able to position the center plate, mount each of the arms, and try this thing out.

KPR