Somebody asked me to describe my propulsion setup for my USS Indiana (BB-58), so I thought I'd post it here as well. - Motors are a pair of Mabuchi RS-550SH, wired to run opposite directions. These are easily available at surplus electronics sources for about $5 or less. Part number decoding at: http://www.mabuchi-motor.co.jp/en_US/technic/t_0302.html Apparently, this exact motor is obsolete, but a reasonable equivalent ought to be RS-540PC/VN, with specs at: http://www.mabuchi-motor.co.jp/cgi-bin/catalog/e_catalog.cgi?CAT_ID=rs_550pcvc Here's a source that I've used plenty of times & still has them available at a pretty good price: http://www.allelectronics.com/cgi-bin/item/DCM-104/400200/3_-_6_VDC_MOTOR_.html - I use a 6V electrical system. I like to use 6V because I can run everything, including receiver, servos, etc. from the same source. I use CSB model GP 6110, 6v 11AH gel cell batteries. That model is obsolete but models in that same series are now available with greater AH ratings (GP 6120; 6V, 12AH). I've had mine for years with no problems. I like the gel cells because they tolerate abuse very well & can be charged with no problems on the cheapest motorcycle battery chargers I could find. CSB seems to be able to cram a few more AH into the same sized package as other battery makers, such as Power Sonic, etc. I use 2 per ship & have no idea how long they'll run because I've never managed to run them down. See: http://www.csb-battery.com/english/01_product/01_series_01series.php?fid=5 - Props are 4-blade, 1-7/8" diameter, & I believe the blade angle is 25 degrees, on the inner shafts. I have 5-blade props on the outer shafts, but only drive the inners. I've found that driving the inner shafts only provides the best maneuverability, keeping the full propwash directed over the rudders all the time. I bought the props from RC Naval Supply (I understand that he's since scaled back & only makes 3-blade props now): http://www.rcnavalsupply.com/ An alternative source of props, if you need them, is Loyalhanna Dockyards. I've only ever bought a couple of things from them (not props, that I recall) but they have a very good reputation in the scale ship modelling community. See: http://www.loyalhannadockyard.com/ - Speed control is a MSonik RV ECO 20 running both motors. I prefer their Marine ECO, but those weren't available when I needed one. This is the same size & power rating, & is also waterproof. The only drawback is that there's a delay of about 2 seconds when going into reverse, that the Marine ECO doesn't have, but I can live with that - just got to be a little more careful to avoid rams. - Drive is a 1:4 reduction using ServoLink sprockets & chain: http://www.servolink.com/ I've used their products since my 1st ship, CA-72, & also use their chain to turn the rudders. It's easy to use & holds up very well. I've only ever thrown a drive chain once, when I originally powered all 4 shafts on CA-72 - I made the mistake of turning hard away from shore when I was too close, & the stern swung into the bank. The bank itself was concrete, at about a 45 degree angle, & the outer prop "walked" up the concrete for awhile before throwing off the chain on that side (I was driving 2 shafts off each motor at the time). It was easy to switch that ship over to center-only, just by taking a few links off the chain, so I never had that problem again as well as improving maneuverability. BB-58 has 8-tooth sprockets on the motors & 32-tooth sprockets on the prop shafts for a 4:1 ratio of motor-turns to prop-turns. Assuming that the motor runs at 9000 RPM, that would turn the shafts at 2250 RPM (that would be no-load, including the friction of the drive system - probably closer to 2000 RPM in reality, for whatever that might be worth). The motors are mounted onto a bracket made from 1-1/2" x 6" long x 1/8" thick aluminum channel, available at hardware stores everywhere. I don't have my notes anymore, with the hole sizes, spacing, etc., but it was pretty easy to measure & figure everything out. I cut a channel down the center so that it doesn't act as a water dam. The motors are face-mounted to the bracket, shafts-forward so that the drive train is "folded back". This helps free up space forward & everything tucks up under the #3 turret (which is a little tight vertically; the gun is mounted on a T-shaped plate that sits on top of the inner shafts). The bracket also served as the inside jig for aligning the inner stuffing tubes & it's attached to the fiberglass hull using a product called BondoGlass. BondoGlass is a product of the Bondo corp., & contains glass fibers suspended in a resin. When a hardener is added, it makes a thick paste that works very well for attaching, forming, & mounting parts. I buy it at Home Depot. I drilled some holes through the horizontal portion of the motor bracket, laid a thin layer of BondoGlass under the bracket, then more over the top, forcing it through the holes so that what's above joins with what's below - it's now a permanent part of the hull & won't come out without serious grinding. Stuffing tubes are my own design, as documented here: http://www.ntxbg.org/pgOnTheWays/pgStuffTube.htm I always use 1/8" shafting for everything, because it's easier to connect the parts together when they're all the same size & 1/8" is easy to find. I pick motors that have 1/8" shafts & order props the same way. Way back when I built CA-72, the biggest problem I had was that all the torque from the motors would just spin the sprockets on the prop shafts (motor shafts are splined, so that they dig into the sprockets nicely). The sprockets don't have setscrews & are available as press-fit only. I tried several different ideas to keep them from spinning on their shafts, including drilling & tapping for setscrews (didn't work well in the soft Delrin material that the sprockets are made from) & shaft collars on each side, with star washers, pressed tightly (almost impossible to get them on tightly enough). What I finally ended up with worked very well & was also very simple: File a notch in the shaft, where the sprocket goes, & dab a drop of thick CA into it. Then, slide the sprocket over the notch & let it set. I've never had one slip, but they're still fairly easy to pry off in the rare event that it's needed (for example, CA-72 doesn't have the clearance to pull them out to the inside, leaving the sprockets attached, so they have to come out to the outside; BB-58 doesn't have that issue). As I recall, I originally had 28-tooth sprockets on the shafts, but that ran too fast so I swapped them for 32-tooth. One of the great things about using chain drive is that it's easy to change ratios if you need to. It makes a little noise, but not enough to be annoying. Belts would be quieter, & the same ratio should produce similar performance. If the exact same motor can't be found, there are a lot available in the same physical form-factor, & sprocket sizes can be changed as needed to get the desired performance. The result of all this is a South Dakota-class ship that runs just a tad over its max. scale speed of 40.2 sec/100' (28kts) wide open. This is exactly where I want it, so that I can trim back a little on the transmitter's endpoint adjustment & have a little room to work with, but not too much, so it's easy to dial it in precisely. Here are a couple of photos of the setup:
Very neat how you use sprockets and chain for your propulsion. Most folks in the WWCC use direct-drive maxon motors, with 1/8 inch fuel or vaccuum line to connect motors to shafts. Question: Is there any chance you could expand this into a full tour of your ship, showing all the different systems, from guns to pumps to how everything fits in?
Sure. I'm planning to get some good photos taken soon (barter with a pro photographer - I don't even own a camera anymore) so shortly after that gets done. JM
Paul, or bb26 as he is on the forum, is building a SoDak. I will have to mention this to him, he has questions he needs answered.
