Picture time, with a weekend of work behind me.
Throttle body assembled as a test fit.
Back in the day, we were belted (quite literally..with a belt!) if our screws were not perfectly aligned in our work piece...apparently old habits die hard..even on a test fit
The tradesmen who took our classes were from the generation that built these aircraft. So these little touches actually feel quite "right".
The three black markings are for the mounting lugs for the Undercarriage Horn switch units. The roman numerals in pictures further down are marked on the throttle sideplates and the standoffs which are coded together as some of the positions are slightly different sizes, distances. They are matched down to the .001" to keep the throttle sideplates square to each other.
Top plate made and fitted but still needs the grooves cut for the guides to Mixture and Throttle levers. Some further machining was required to bring the flanges down to the correct size and fit. I still have to remachine the side flanges as they are very slightly out from front side to back side due to not clamping them tightly enough the first time I levelled them. Luckily there is still about 1/16" tolerance to work with so I should be able to do that and still be within "spec".
The adjustable stop for the throttle travel made from 3 pieces of 3mm aluinium and aircraft rivetted together. I was most unhappy with the imperfections in this and rivets showing, but figured car bog may crack with the tension on the piece...so I remade it in steel:
It is a small piece and is a delicate L shape with a channel cut through the centre to accept the bolt and adjust position. In the end I decided there was no chance of clamping it and still being able to work with the milling machine collet chuck closely enough to cut it. So I cut it and formed it on the end of a 3" x 7" bar of steel I have and then sliced it off that like a bread slice. It is only one inch by 3/4 inch by 1/8 inch in size!
Next I moved on to the mounting brackets. These are deceptively simple looking...until you work out that they are bent on angles (each one slightly different!!) to mount the throttle at an angle. They are also slightly different shapes left and right of centre. Too close to be easy to tell but too far apart to ignore the difference.
So..on to my tool of absolute last resort...graph paper and my (VERY dodgy) Tech Drawing skills.
I had to do these from looking at detailed photos and a bit of mental "unfolding" as I don't have GAs for them. The first is the bottom bracket, a very wierd shape indeed for a simple triangular bracket. Rather than chance it, I cut the patterns out and actually flded them to make sure that they would work. Apart from a few minor glitches caused by material thickness, they did.
When I first put them next to the photo below, I had a heart attack, thinking they were totally wrong...then I remembered I had blown that photo up and changed the relative width/lengths, to make it fit an A3 sheet and show the biggest detail I could get..so the photo is wildly out of proportion.....the drawing is, however, 1:1...so I couldn't be THAT wrong...could I...
My panic abated when I matched them to the drawing and put them against the throttle body
You can see now, how badly the below picture is "out" but why my heart sank when I put the brackets next to it!!
The aluinium braising on the bottom bracket did not go well.. my torch wasn't even enough, so it will now be filled with an epoxy resin called JB Weld which is strong, can be sanded and is easy to mix.