The only way I even have a fighting chance to make it to NATS this year is to simplify the Deutschland design I already have. To be perfectly honest, I still don't think I'll be able to make it this year. Even if it doesn't work out; I wanted to produce a simplified Deutschland anyway. To call the original design complicated, would be an understatement. It's a 3-unit Heavy Cruiser with 6x cannons, rotating cannons with convergence, and anti-roll stabilization. I'm quite proud of it, but it can be simpler. For this revision, my goals are to simplify: Two Cannons only - Eliminate the valves, firing boards, and a lot of complex wiring. Larger Pump, designed for IRCWCC. IRCWCC rudder. Big props, preferably plastic. Improve water flow around the batteries/bottle. Keep both cannons rotating, so it can fight in Big Gun. One cannon per turret in Big Gun config Two cannon in aft turret in IRC config. Simplify the motor mounts. Create F360 parts for anything that I can reuse later on Tiger. Deck seals everywhere, not just the aft deck. Implement magnetic decks for key areas only.
I had some time tonight. I removed the superstructure from the project completely then I pulled the servos and servo mounts into a part file and reused them. I continued by rearranging everything in my timeline; moving everything that I wanted to work on right (later in the timeline). - The pump, batteries, motors, valves, cannon rotate, CO2 bottle, valves, and ESCs are now the last things in the timeline so they are faster to change. I then started removing things. The 2 firing boards and 4 valves are now gone. I learned I like deleting F360 objects almost as much as I enjoy deleting code. I want to give my pump more room, because I want to try out larger diameter impellors. This also helps me clean up the ESC wires which were getting crushed in the first revision. I moved all the CO2 systems forward in the hull. The ship's balance point was pretty good before, but it was weighted toward the aft. I'm hoping this will improve the overall ship balance. I'd love to know a simple way to model this in F360.... ..and that's all I have time for tonight. Next time, I want to start revising the pump.
Had a little more time tonight. I was able to move the pump to the new area I created for it. - I also enlarged it to for a 2.25" impellor. - The motor is still too small, so that'll be the next project. I kept with the exchangeable pump outlet, so I can use a reduced outlet for IRC and an unrestricted for Big Gun. - I would much prefer pushing the reducer somewhere into the hull, but I want to print my water pipes more.
Why such a large impeller? I can get 3.5gpm easily with a 1.125in impeller. Diameter only increases strain on the motor.
Ok. So let’s talk.. I assumed that a larger impeller would move more displacement per rotation. I would expect it will take more torque to rotate, which will be more current draw per RPM. To compensate, I’m hoping a lower RPM will be required to get the same flow rate. Lastly, I’m assuming with the IRC restrictors, there is a point of diminishing returns on max effective flow rate. So I expect there is a balance point of impeller size vs speed/current. I took a wag that larger impellers could show some improvement, so I started there. And yes, I’ll prolly try a normal one and a smaller one. What do you guys expect will happen?
Rainy day progress. I did a little reading online, learning a little about the types of impellors, the ratio of the channel width, and shape of the intake. The space between the impellor and the motor mount is the rubber O-Ring between the motor mount and the pump housing. - I'm not sure where the Air bleed should go. I put it at the top impellor blade, pointed horizontal.
You'll waste a lot of electricity, burn up a motor, get poorer results. Generally, the sweet spot is considered to be "slightly smaller than your motor diameter". I go with 1.125" for battleship pumps, etc. Now, if you used a 700 size motor, something like 1.5, or even 1.75" might be appropriate. Never tried that, but I'd only do it for something in the 35+ lbs category.
Justin it really comes down to two different paths. Either you are scaling an existing pump design or making a new one. when scaling off of diameter and rpm, the pumps will generally follow the plots below unless the specific speed range takes the design out of where it is the correct design. Note that these curves are NOT how the pump will perform at a specific operating point, this is how you scale the entire pump curve. Once the pump curve is scaled, then the system pressure drop vs flow equation can be fit to the new pump curve to find your new operating point. if on the other hand, you are engineering a pump impeller around a specific operating point and RPM, then the story is a bit different. Optimal diameter will end up being a function of the specific speed you are operating at, the RPM and the pressure rise. As your targeted RPM drops or targeted pressure rise increases, the optimal diameter will increase. Add to that , that peak efficiency tends to drop as specific speed drops, that tends to drive you to RPM's that put the impeller in the ~1-1.5 inch diameter range fairly commonly for our application. One more thing to keep in mind... tip clearances need to be small. large tip clearances result in large leakage flows unless you are trying for more of a pitot tube pump than a centrifugal pump. Fully shrouded impellers help with tip clearances but the efficiency gains seen with the shroud in the primary flow path are often offset by the need for seals and drag on the outside of the shroud.
The typical setup for this ship for IRCWCC would be triple stern guns and half unit pump. I have the small BC pump in mine and I think it still took around 100 holes to sink, which is way more damage than any cruiser should take in a fleet battle. I’d guess that pump puts out less than 1gpm, so if you’re trying to finish a boat for nats, I’d focus on getting the core functionality right
It’s all gotta be done, but understood… don’t burn a lot of time on it. Slam something in and move on.
Part of his point I think also relates to your expected division of combat units. 3.5 unit ship with 2 cannons isn't the best way to build a AGS for IRCWCC. Basically universally accepted that they're 3 single unit guns, half unit pump, boats. The hull is so small there's no reason for any more than a .5 u pump.
