With the exterior paint work done, I have to get the propeller shafts installed before retiring Tent Model IX. The tent goes all the way to the ground, which keeps out any breeze that might blow away the argon shielding gas from weld areas…and the prop shaft cutlass bearing housings have some very critical welded joints.
Our Roamer originally came with 1.5″ Aquamet 17 shafts that worked fine for the 400hp twin turbo and intercooled Super Seamaster engines that were in the boat when we first got it. But when we decided to upgrade to Cummins 430hp Diamonds, with all of that power coming online at 2600rpm (vs 3200rpm for the Seamasters), the result was a safety factor of three. Since the recommended safety factor is at least five, that meant we had to replace the shafts with 1-3/4″ ones. While the original shaft log would accommodate the larger diameter, I had to cut off the cutlass bearing housings (with brand new, practically unused cutlass bearings installed back in 2009!) and have new ones made up and welded in place.
The good thing about aluminum is that woodworking tools can be used to cut and shape it. A sawsall and circular saw with carbide blades got the old cutlass bearing housings off the boat fairly quickly.
Before we could weld the new cutlass bearing housings onto the original 3/4″ 6061 plates that make up the V struts, we had to ensure that the the struts were cut to the proper angle. The collets in the picture above are sized to fit around the new shafts, then slide inside the new housings.
The cutlass bearings are made of rubber and phenolic, neither one of which responds well to the kind of heat we’ll generate when the housings get welded in. The two-piece collets are a tight fit to the shafts and a snug fit inside the housings, but not too tight…we need to be able to remove them after the welding is done and everything has cooled down.
When we raised the shaft/collet/housing assemblies into place, we found the V-strut cuts were pretty much where they needed to be. In the engine room, I verified that the shafts were dead center in the shaft log. I used a jack to raise the housings as high as the V-strut plate cuts allow before blocking them up.
Welding this intermediate strut assembly will prove to be a challenge, since my Miller Spoolmatic 30a has a straight nozzle. With only six inches between the hull and the bearing housing, it doesn’t have much room to allow us to weld inside the V.
My Miller Trailblazer 280NT and the spool gun performed flawlessly while the fabricator made multiple passes to fill in the “vee’d out” welded joint. On the rear strut, he was able to weld inside the vee as well as outside. For the intermediate strut though, the straight nozzle on my spoolgun just won’t work. We’ll have to take another crack at it with a flexible nozzle the fabricator will bring from his shop. Since we had both housings welded in (as far as we could with my equipment) on the starboard side, we prepared to swap the collets out so we could rig up the housings and shafts on the port side.
The two collets on the intermediate housing came right out, but on the rear strut the rear collet took a bit of nudging with a hammer and chisel. Unfortunately, the forward collets just wouldn’t budge…at all…not even with a 10# mallet. So, we have to wait until next weekend to attack again. We’ll use a bit of heat and maybe a hydraulic cutlass bearing press to remove the collets and set them up on the other side. We’ll also have the fabricator’s welding gear that can weld in the tight space of the intermediate struts.