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I'm going to get a pair of lehner 3060's but I'm not sure about the wind. I'm wanting something in the 780kv range. Anyone explain what wind gets me there?
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80% of people who claim to hate racing have never been to a race. -
A 9 turn 3060 will get you to pretty much exactly the Kv you want.
Here's the link to the online pdf with all their motors;
Now I gotta know what you are putting them in! ;-) Of course the 72"! -
20161206_164106.jpgGoing in a new Central RC Marine 72 Mystic. Not sure I can drop the cash on MGM's just yet, so I may get a pair of Swordfish 300's and see how long I can make them last. Try to lean the boat and not hammer on the ESC's for a while till I can justify a pair of MGM's. $800 per side seems crazy, but it sounds like they are the way to go. This is my first large scale boat, so I'm pretty excited to get it running.80% of people who claim to hate racing have never been to a race.Comment
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Hey no need to explain about the MGM's, it is a massive amount and I will be feeling guilty for some time from my purchase, it is crazy. I think going with the 9 turn is a good choice for 12S. As long as you keep a close eye on your temps on the maiden run and when trying new props you should be OK with the SF300's. Ideally the X457 props would come in 1/4", sadly they don't and they would be have been perfect. Be sure and only use the 1/4" shafts (and 1/4" cables of course) on your boat, 3/16th stub will not last long and you will lose your prop(s) when they snap. So with that being said you are pretty limited on props that will work well for your setup, most 1/4" props are going to be way too large as they are more aimed at low rpm gas boats. I have not tried them on a full run yet in my boat but the Prop Shop 6514's reduced to 57mm (by Chris-Dasboata) will be a nice prop, need to do an amp log to see. At least you are in no rush and have alot of time...will always be here to help and look forward to sharing my finding and results.Comment
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Thanks for all the info! I have 1/4 shafts on the way. Need to do the carbon inlay and get all the parts here for mockup. Sounds like the 6514 prop is pretty popular. Can you explain how the wind gets to the kv? Plan on running 12s and getting a good prop for faster straight runs and having a different battery/prop setup for playing around. Hope to have it ready for spring.80% of people who claim to hate racing have never been to a race.Comment
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Well the "Kv" of a motor is basically the rpm/volt and determined by the number of "winds" the motor has, lower winds have higher Kv, a higher wind number will give a lower Kv. Multiply the Kv of the motor by the number of volts you are running (12S=roughly 48 volts) to get your rpm (48v x 780=37,440rpm). Of course actual rpm at the prop will be lower for many reasons such as motor efficiency, hull and prop slippage etc and to make matters slightly more complicated, Lehner's are rated under-load, so comparing a 1000Kv Lehner to a 1000Kv TP will be about 10% difference. As far as I know only Lehner gives Kv numbers under-load. Anyways, don't worry too much about it, the 9 turn 3060 will be perfect for your boat and soon all the talk of Kv etc will be a permanent part of your vocabulary, at least while here at OSE.
Use the OSE calculators to mess with some numbers here;
http://www.offshoreelectrics.com/conversion.php
The "Speed Estimate" is about the 6th calculator down the page, fun to plug numbers into that to get a baseline idea. Plugging in the number for Kv (780), Motor efficiency (90...probably more like 95 for a Lehner), 12 cells at 4.0 volts you can see the rpm turns into just under 34,000 (Perfect!)...then you can continue and enter prop numbers for speeds but that is where the calculator goes off noticeably at least for a dual Cat...but interesting nonetheless!
Glad to hear you are doing the layup, make sure you ask all your questions before starting, alot of very skilled guys here that you can learn from.Comment
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I understand the kv to volts to rpm, just wants sure how the winds calculated into it all. I'll have a lot more questions before it's finished. I have an ace up my sleeve with a buddy that designed cars and a few boats for Traxxas, so I'm going to get him down to look the layout over before I start drilling get and mounting.80% of people who claim to hate racing have never been to a race.Comment
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Oh ok sorry for the explanation...tried to keep it short.
Just noticed the pic of your hull further up...NICE! Looks like you have a nice workshop and tools...and having a buddy at your side will be great.
Keep us updated please!
Will be running my beast this weekend so stay tuned.Comment
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Look forward to seeing the run.
Gotta have a shop or I'd go nuts.
Thanks for the explanation, every bit helps. Still curious if there's a calculation to take the wind to kv, but thanks for all the info!80% of people who claim to hate racing have never been to a race.Comment
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It has to do with the gauge of wire, length of that wire per wind. Equation though, mmm, over my head. In the old brushed days one would really have to pay attention to winding to keep the KV the same for two motors. I believe it rings true to brushless as well.Comment
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