With the Omaha builds progressing slowly but surely (Shirley), I'm getting to the point to start thinking about how to put in the propulsion system. There are a few options available: - twin direct drive motors - twin gearboxed motors - single motor, twin shaft gearbox - single motor direct drive with gears to drive the second shaft I don't like the idea of twin motors. They take up a lot of room. My Gloire has twin Speed 400s with a built in gearbox. It works, but is noisy and takes up a lot of room in a small hull. The Omaha hulls are even more cramped for space in the stern area. So a single motor twin shaft setup sounds like the way to go. Frank mentioned something about Dave finding a small single motor twin shaft gearbox someplace. Dave, do you think it'll work? Where did you find it? The other single motor option may be promising too if I use 1" or 7/8" diameter props. The idea is to put a gear on each shaft, mesh the gears so that when one shaft turns the other shaft turns too, then connect the motor to one shaft either via direct drive or a gear to one of the shaft gears. I used the gear to gear method in my little Mogador destroyer, but haven't seen how it'll perform on the water yet. Any other options you guys can think of?
I like the single motor, twin shaft box. If you are really tight on space, a brushless motor will save some space over brushed. If the Omaha is similar to the Karlsruhe in dimensions, and you choose to go that route, you could copy my setup on my karlsruhe, although if this is for big gun rather than fast gun, you could readily use the next size smaller motor.
Good point Greg. I actually have a few small diameter brushless motors on hand from various park flyer projects. One of those would be nice. By the way, what is a good brushless ESC for our ships? Where did you find a single motor twin shaft gearbox at?
I made my own gearbox, as the BC one available at the time just did not fit like I wanted it to. After I get moved, I hope to be able to make a few things for folks again as my mill will be set up next to my study room. If you do go brushless, my best suggestion (for fast gun, this is directly applicable) is that something in the 1000kV range for 6-9V usage. I'll have to look at what exactly is in the karlsruhe, but I do remember that the gear ratio is between 1:1 and 1.1:1, give or take (don't remember exactly what I settled on) Mtroniks makes a brushless controller, Justin has one. I have been using a home-waterproofed castlecreations mamba ESC, partly for the programability. you can plug it into your computer and set most of its settings to anything you want. I've had mine since 2005 or so. they also have the sidewinder series which replaced my mamba in their product lineup.
Mike, I ran one in 2002 nats in houston with little success. Actually sank it running backwards, didn't take too long to do that. Once it went down, due to a faulty box it was done for the week (thankfully it was a secondary ship). If I had to do it again I would look at doing an extra long shaft and get the motors near the middle of the boat to make enough room for the guns in the stern. I did run two motors with dogbones so I could move the 390's to the outside of the channel and leave room for the pump. Watching the build with great interest. Lou
While reading some of the old Lars Nats stories, I found out that Stan Watkins ran a Detroit in the 97 Nats. So the ship has been around a while. On my build, the ships will have solid stern decks, i.e. no hatches for water to enter the ship. I think that will go a long way to keeping these things on top of the water. Heh. If we discount the Omaha's stern deck, the ship will actually sit about 1/4" higher at the stern in the water than my Gloire CL, and even higher at the bow. I'm leaning heavily towards a single motor solution. I can run the cannons on either side of the motor. I would also like to keep the motor towards the stern for weight since the rudder servo will not be under the stern deck .... instead the servo will be moved up under the main deck and a pushrod used to move the rudder. Soooo ... either a single motor twin shaft gearbox, or the single motor direct drive dual shaft gears method. A gearbox would keep it simple.
Yup. Kinda figuring that a 380/400 sized motor would be needed to spin two shafts. I would very much like one of those gearboxes if possible. It would keep things simple.
Won't be able to make the May battle ... I've already committed to the Armed Forces battle the same weekend before our region's date was set.
The gearbox, I have is one of Greg's. Got it like 2 or 3 years ago, and have not used it as of yet. Was planning on using it in the Omaha actually.
Just sent the PM Clark. What is the distance from center to center of the gearbox shafts? I can start planning the prop shaft installations.
That sounds right, if you look at the pic of the driveshafts on Almirante Villar, those are 1" props offset to allow fitting, got about 1/4" clearance from prop tip to opposite shaft.
One of the things I did in the karlsruhe that I really like how it turned out (particularly for a single rudder ship) was to use three bladed props set such that the blades on the props overlap while the props running. you have to keep the timing right (or you eat props/dogbones) but it brings the props in towards where they should be scale wise and seems to get good flow over the rudder.
