I was hoping to use a ratio of about 1:1.3; but I think that is a bit too short. What do you run? 1:2.5?
Whatever works with the combination of ship, motors, & props to get to the correct speed. I don't use oversized props - they generally won't fit in the scale location (clearance to hull) & moving them outboard looks goofy, & ruins the shaft angles. I've got 2 warships with direct drive (i.e. 1:1), 1 at 4:1, & another at 4:3 (20:15). I'm curious why you hope to use any particular ratio? JM
First: I'm using a (watercooled) ESC; so no matter what ratio I use... it will work. (provided I can get the motors to spin slow enough) However, the higher the ratio the more weed/muck chomping torque (which can be an issue here) but the lower the operating time (higher speed = higher current draw) Why 1:1.3? I wanted to use helical gears because I wanted to see what kind of sound difference it would make on a model. Back story: I've seen a custom "1:1" car that used straight gears in its transmission & it sounded like a rc car. I wanted to pull out my spektrum & drive it around. I'm curious what would happen the other way around. Car transmissions use variants on the helical gear for quieter operation (among other things). So I went looking for some helical gears in our size & all of them are $15/ea... It's not worth it for me to spend $105 (4 shafts, 3 motors) on gears that I may or may not be happy with. A couple days ago, I found a set of nylon helical ~1" gears for $1 / set... The problem? They have an overall ratio of 1:1.3. If 1:1.3 isn't enough: one option is create a gear train... 3 sets would get me near to 1:2.5 ratio. I've created gear trains on robots before, and if you think matching 2 gears is tough.... 3 is tougher. The problems with using a gear train... 1) it would create more noise 2) it would make make the system that much weaker 3) it would add one more place for the system to break 4) it adds complexity I think helicals would be great, but at their cost & the complexity of a geartrain... I think if 1:1.3 is not enough then I need to throw away the concept.
1:1.3 is good, but like you say, not as much weed-crunching torque. I'd be hesistant to use nylon gears, though... I'd think they'd be prone to stripping. Good with chicks, bad with gears. The ESC should be able to make anything work speed-wise, although the higher gear ratio will allow the motors to run in their most efficient speed band (higher speeds).
So what do we say? Worth my time & effort or throw 'em away? Remember its for a 50lbs Iowa class battleship. I also want to say helical gears would be less likely to strip because at any one time there are more gripping surface area.
You might want to consider a belt drive, in particular a Gilmer (i.e. toothed or "timing") belt. Belt drives are very quiet, & are quite tolerant of misalignment (unlike gears). It's also a lot easier to mix/match different pulleys than gears, since the center locations aren't as critical. It's pretty easy to make a movable motor mount or an idler to take up slack in the belt. I've used chain drive on a couple of ships & it works out well, except that it's a little noisy. Nothing like improperly-meshed gears, but there's an audible whine. Chain has the same advantages as belts in terms of tolerance to misalignment & flexibility of sprocket choice. JM
Well, I am not sure why my reply was eaten, but here it goes again. Check out the tirpitz pictures thread, it will link to the pictures of my beltbox for my tirpitz. I am using an MXL timing belt with gears that I bought from either mcmaster.com or sdp-si.com. I have not run it yet (still working on it) but it looks like it ought to work well. If you want counter rotating props, you can get a double sided belt and make a belt box that counter rotates the propellers as well. -Greg
My 31 lbs Scharnhorst is propelled by one 2 inch three blade prop. Driven by a 1.2a no load 550 size motor. Motor is mounted to a Traxxas Villian gear box. 14 tooth steel pinion on the motor. 28 tooth nylon gear on a 5/32 prop shaft. Both gears are 32 pitch. Gears are the simple straight cut type. The 28 tooth gear has never stripped in 6 years. Been mossed dozens of time. Gear lasts two seasons. Even though the steel pinion wears less, I change them both at the same time. Same gear box for all six years. Gear box is Traxxas #1521R, $15, but you get two boxes in one package. You must cut the aluminum motor plate in half to seperate it into two gear box units. 28 tooth gear is Traxxas #1526, $2.9 ea, one per package. 14 tooth pinion, $3.4 each. Mark
Hi mark! Welcome back! Looks like you got your computer working! Yeah, I have the traxxas villian casing in the back of my mind... I just can't shake some of the things dave was saying last weekend about its noise. When it comes down to it, noise does not matter much. I just like to explore all options, you know me! Also, I decided it take your advise & not complicate the cannon assembly with that spinny thing I was brainstorming about. I'll just buy one valve every two weeks until I have enough.
My Yamato is using the Traaxis gears though my aluminum steel plate did not need to be cut as it was already precut for each gear box. I don't know why Traaxis make them like this but I wish they went back to making the plate as an individual section for each gear box. I use a 12 tooth pinino on a 28 tooth nylon gear. System is fairly quite when it is lubricated and the stuffing tubes are lubricated well. I've run a variety of sized props. Currently have 25 pitch 4 blade counter rotating brass props sized dia 2 1/4 inch. This pushes my Yamato at 54 lbs too fast. I used to run 100 feet in 24 seconds with my original props 4 blade 25 pitch 1 3/4 in props and that worked very well on the gears. Originally the gears had a 14 tooth pinion but even with the orignial 1 3/4 in props it was too fast till I switched the pinion for a 12 tooth pinion. I like the Traaxis gears as it's great for large battleships easy to setup and maintain. Curt
I've decided its not worth fussing over, I should have the new helical gears tonight; Three gearbox won't be that hard with my current machining setup... I'm just going to "do it" & if there is not enough torque halfway through the season... I'll just have to drill another couple of holes! Either way, we'll all learn somethin'! Done.
Well, after giving it the old college try I decided it helical gears just were not going to work out for me. So I broke down & got some straight gears last night & guess what? As of this morning, I have 1 of 3 transmissions finished! YEAH!
Well, after giving it the old college try I decided it helical gears just were not going to work out for me. So I broke down & got some straight gears last night & guess what? As of this morning, I have 1 of 3 transmissions finished! YEAH!
My new gear ratio is 1:2.9 & after 1 hour of desk tests it seems reliable enough to move forward to install onto the boat for lake tests. Thanks everyone!
So all 3 gearboxes are done? Are you lubricating the gears? I've wondered if that'd help the noise issue (since I hate gearbox whine in my boats).
I am lubing the gears... And to tell the truth, when lub'd up they are not that noisy. Sound like a power drill. However, the boat's hull works like a sounding board & they become just as noisy as every other geartrain out there.
