Ralph Coles and I started work on his SMS Seydlitz this morning. When he made the mold for the Tuttles years ago he included the bosses on the hull where the 4 prop shafts exit. By chance the centers of the inner shafts are 1 9/16" apart, just right for the Battlers Connection dual output gear drive, but too close together for a pair of 500/550 motors unless they're staggered. I'm sure a BC dual output drive will be OK for Indefatigable but the Seydlitz is 1/3 heavier and a faster model so we don't know if a single motor will provide enough speed. I used a single 545 motor and a 2.5/1 MFA belt drive, driving a set of Dumas gears for two shafts, and 1.5" props in HMS Courageous (a 24 sec model) but Seydlitz will be 15-20% heavier. Looks like the shafts will be so close to the hull that we'll be limited to 25-30mm props (1"-1.2"). Has anyone had experience with the BC dual output drive in models over 20 lbs.? What propulsion is used for Derfflingers? Seydlitz might be able to use a similar drive system. All advice appreciated!
Thanks Nick, I suspected we'd have to use two 500/550s for Seydlitz. She'll be just a bit lighter than a Derfflinger. Do you know the gear ratio you're using? I expect Ralph will want to use the shaft features molded as part of his hull rather than file them off (which would result in two holes in the bottom and more fiberglassing). Not moving the shafts outboard will limit us to 1.2"props but 4 and 5 blade props are available. If we can find motors with shafts on both ends we could couple them and still use the BC dual output gear drive. Alternatively we can stagger the motors fore and aft and use one per shaft.
I think i have 19:28 installed right now but thats not very informative without shaft rpm numbers. The mabuchis i have seem to be slower than the commonly used johnsons
I have never been accused of feeling the need for perfect scale. If it were me I would be tearing into that hull to make the best prop - rudder arrangement. I also place my motors as wide as possible with a little toe in. If I can get the pump between the drive motors is save space. I think that the toe in give just a little better maneuverability. No I have neither the money or motivation to prove it out. Keith
I agree - with the exception of Hood I've installed prop shafts where I can fit the optimum prop size with the props close to the rudder(s). My Hood mold (now Strike's) has the prop shaft locations molded but the inner prop shafts are fine in the scale position due to Hood's sharply tapering stern lines. I don't have any 500/550 motors with shafts on both ends so they can be coupled, so it looks like we'll have to abandon the plan to use the BC dual ouput shaft system in Seydlitz. I'm going to try to persuade Ralph to install the prop shafts further outboard, but he may want to try 1"- 1.2" multi-blade props in the scale position first.
I've been working on the Seydlitz hull this week trying to get it to the same stage of construction as Indefatigable. Although all four shaft positions are molded on the hull the inner shafts are just far enough apart to install 35mm diameter (~1.4") props. I can't see it needing larger props - the only time I've gone for bigger ones was on HMS Hood (40mm). We'll be using two 545 6V 'low draw' motors from the UK; the same type I used in Courageous. I'm trying to find a second 2.5/1 MFA belt drive (used in model airplanes and in Courageous) but no luck so far. Might have to go for Traxxas or BC gear boxes if they'll fit close enough together.
My BC hull has 1-1/4" 4blade 40pitch props on GB500's here is video of it turning. Note after the video I speed tested found it to be 32sec. She turns much better now at 24 and nearly goes backwards in a turn View: https://www.youtube.com/watch?v=SXN-9pS01kE&feature=youtu.be
