The plans call for the trunnion tube to have a .125" wall. Unfortunately it seems that Wicks and Aircraft Spruce carry it in .120" wall thickness with .188" as the next step. There is .01" of play between the 2.5"x.120" and the tube it slides over(upper leg) which is 2.25" OD. This is sloppy to me so I got the 2.5x.188(2.125"ID) and bored it on the lathe to 2.25" ID. This is time consuming as you can't take deep cuts with the extended boring bar(too much flex). In front of my hand is the boring tool and in my hand is a snap gauge. You put the gauge in and let it spring open, lock it and measure it with an outside micrometer. A dial caliper can give false measurements unless you are very careful to position it properly in the hole. You should make several measurements after each cut if you are using a dial caliper to make sure you aren't in error. A set of cheap snap gauges goes for $10.00 and you could use them with your caliper for increased accuracy if you don't want to buy micrometers.
Because I'm building parts for another WAR builder I thought it would be nice to make a trunnion stamp. ( I would also like to have the best parts available) The trunnion horns hold the upper gear leg tube in which the rest of the assembly rotates as well as support the gears. As I said before it is critical to have these gears mesh properly. The alignment of the "horns" also affects how the landing gear will tuck up into the narrow well when retracted. When installed to the trunnion tube the 3/4" holes need to be aligned. This is accomplished by making a welding jig capable of positioning everything in proper relation to one another.
The trunnion plate layout in the plans is obsolete due to a revision. You can take a trip to the library or buy the FAA book which tells you how to caculate your layout.(Bend lines that take radius into account etc...) If you are very careful and use a bench vise with a tube sanwiched in the jaw you can achieve the proper radius and bend. Thank God you only have to make four of them!
IMPORTANT!! The 3/4" holes need to be reamed. Don't think that you will get a 3/4 " hole with a 3/4"drill bit. A reamer is a tool that capable of cutting an extemely precise diameter while giving a great finish. The next page deals with welding jig suggestions and how to fashion the trunnion horns in your shop.
The beginings of the trunnion horn stamp. You don't need one of these to make your trunnion "horn" . This tool made uniform bends but failed to do the 13 degree bend well. That's OK the vise worked just fine to do these. In hindsight I would have just made a flat bar with radiused (3/4" radius) sides as the male part of this stamp.
