Big motor options

[keithbradley]

I'm looking for insight from anyone who can help. I will soon be building a 73" Mystic and I would like to get it somewhere near 100mph. Everything I do on this cat is incredibly expensive, so I'm trying to find a pair of motors at a decent price. The Neu 2230 and Lehner 30xx are a bit more than what I want to spend. I have Castle 200HV ESCs to use and I plan on running 10s and 12s.

I can get a pair of TP 5850 (58mmx92mm) motors but kv is only 820, and I think I am going to need something closer to 1000kv to get the speed I want.

Leopard makes the 5698 in 910kv and 1100kv, but they are not rated for very high RPM.

Scorpion 5035s are low kv (500)

Neu 2215s and 1530s are both rated for the same power (2500/5000W), but I fear these motors are too small and won't get me the speed I want. I like the high RPM capability of the 1530s, but I've got a big hull to push with such a small diameter motor.

Ideally I could find a great deal on a used pair of 2230s or 3080s/3060s, but those items don't come up for sale often.

Does anyone have any input on these options or know of anything out there I'm not aware of? I'm looking for info from members with experience with large/fast cats. I would rather not have speculation from people who have 60mph small cats. I build a lot of twin cats and I'm fully aware of how to make a cat under 50" go fast on a budget, but this 73" is quite different.

[Rumdog]

Just gas a rhoughr, bud.
Check out this thread:http://forums.offshoreelectrics.com/...ut!-Sneak-peek!
Not too much info yet, but nay end up being a great Lehner alternative for you.

[keithbradley]

Just gas a rhoughr, bud.
Check out this thread:http://forums.offshoreelectrics.com/...ut!-Sneak-peek!
Not too much info yet, but nay end up being a great Lehner alternative for you.

Thanks.
I saw that post a while back, but can't seem to find them for sale anywhere.
If anyone has info, feel free to forward it!

[ron1950]

not sure of the top rated rpm but what about a pair of castle 2028's they will work with 200a esc's think they are 780kv...just a thought

[keithbradley]

not sure of the top rated rpm but what about a pair of castle 2028's they will work with 200a esc's think they are 780kv...just a thought

I considered those as well, but with a 780kv, I would have to turn some monster props to get the speed I'm looking for.
I think they are also rated relatively low in terms of max RPM...something like 9s.

[T.S.Davis]

I don't know if you can push a serious project like that on budget motors. Interesting experiment for sure. I know I'll be watching to see how you fair.

I was going to suggest a 2215/1.5y or maybe a 2220/1y but same problem you're already finding.....$$$$

I wonder if a 2230/.5y is possible. Giant torque beast rotor with giant RPM numbers but extra giant dollars too.

[keithbradley]

I don't know if you can push a serious project like that on budget motors. Interesting experiment for sure. I know I'll be watching to see how you fair.

I was going to suggest a 2215/1.5y or maybe a 2220/1y but same problem you're already finding.....$$$$

I wonder if a 2230/.5y is possible. Giant torque beast rotor with giant RPM numbers but extra giant dollars too.

Well, it depends what you consider "budget". With the cost of the hull, drives, ect., this project is already aproaching a few thousand. I'm not suggesting I have to get motors for $100 a piece, but I don't want to spend another $1600 on motors either.

I considered the 2215, but I'm not sure if they have enough power or not. Believe it or not, the 1530s are rated the same as far as power output goes, only difference is the big RPM numbers they rate the 1530s with (60k). I'm not sure if either of those motors have the potential to swing a x457 at high RPM. I've ran a 2215-1.5y on an x457 on 10s and I felt like I was really at the ceiling of the motor's potential....but I could be wrong.

This guy is running Leopard 5692s, but who knows how long they have lasted, and it's a considerably less speed than what I would like:

http://www.youtube.com/watch?v=_Kx8g7FVX9U

[keithbradley]

By the way, I'm not DEAD SET on a speed range. I would like to get close to 100, but it may be a difficult task without exotic parts. I currently have cats less than half this size that do 90mph (takes a lot less power) and I feel like this big cat is going to seem too slow if it's slower than my little boats.

[T.S.Davis]

I hear ya. What's budget about a monster like this? Not much. Paint could run 500 for a boat this big.

Those 5692's appear to be adequate but you're looking for another 25mph.

I have know idea if any of the 22 series can handle the rpm's. Maybe it's worth a call to Steve. Ya hate to go Lehner but with the RPM your after they might be the best option.

I see why you're struggling to find a combo you're comfortable with.

[T.S.Davis]

We posted at the same time.

[RaceMechaniX]

100mph in a 73" equals cubic dollars. You can try using cheap motors, but be prepared for disappointment and a lot of controllers that end up looking like charcoal. Probably the best option for the price is the Castle 2028, but 30k+ RPM is not advisible on any large motor. And know that big Lehners do not use a wrapped or sleeved rotor so they are the most vulnerable.

Look at the set-ups used by SAW racers and you'll notice a common theme: High quality everything!

[Fluid]

You will need big props with that boat, I suspect that 57mm is too small for optimum efficiency. Using x465 or x665 props may work better for you. To get 90 mph with the x665s you'll probably need around 29,000 rpm on the water to get 90 mph. These rotational speeds are within reason for motors like the Castle 2028s - those in our club are perfectly happy on 10S. Those are big props but on a cat you can run them high to unload the motors. Pitched up a bit they may get you to 100 mph.

I looked long and hard at the 1530 for a 10S single-motor cat project, but decided that it would not have the torque required to spin a 60+mm prop fast enough. I know the large-format motors like the 2215s, 2230s and 3060s have no problem with big props, in part due to the larger diameter rotor.

I would worry about spinning the Leos very fast. They have had known bearing problems (fixable but an added cost), and I don't know how their big magnets will stay in shape at 40,000 rpm. Will they spin a big prop fast enough? Don't know. They are "cheap" but the 2028s are not that much more considering the magnitude of your project. It is cheaper to buy enough motor the first time instead of buying cheap first, finding out that they don't work, then buying the right motors anyway.

Outrunners are rpm-limited, as much by the controller ability as by the motor construction. The Germans seem to do fine with boats this size using Lehners and Schulzes, but that is a top-end cost solution. To my mind for a sport boat you're better off using prop pitch and reasonable rpm to approach your speed goal. If you haven't posted it elsewhere I'd love to see a pic of this hull......



.

[keithbradley]

100mph in a 73" equals cubic dollars. You can try using cheap motors, but be prepared for disappointment and a lot of controllers that end up looking like charcoal. Probably the best option for the price is the Castle 2028, but 30k+ RPM is not advisible on any large motor. And know that big Lehners do not use a wrapped or sleeved rotor so they are the most vulnerable.

Look at the set-ups used by SAW racers and you'll notice a common theme: High quality everything!

I'm finding that doing anything with a 73" cat = cubic dollars.lol

I'm considering the Castle motors, but I'm not sure about the low RPM...I've never been a big fan of super aggressive props.
I can't seem to imagine 1530 motors pushing a hull this large, but it seems like they might push a 57mm prop ok in a twin setup...maybe I'm off on the prop size for this hull? It seems small to me, but going off videos of others, x457s seem to be a popular choice. If x457s will move this thing, I would almost be tempted to try 1530s...they just seem like they would get lost in that hull.

If I go with the castle motors I'm going to need to spin bigger props...even the 2230 would require a larger prop, as the kv is low on that motor also.

I would really like to hear from someone who has gotten good speed out of a hull this size. Even if I'm willing to spend the largest stack of paper possible on motors...I'm still not convinced that one motor is the best option. I'm really at power vs. RPM with nearly every choice.

[keithbradley]

You will need big props with that boat, I suspect that 57mm is too small for optimum efficiency. Using x465 or x665 props may work better for you. To get 90 mph with the x665s you'll probably need around 29,000 rpm on the water to get 90 mph. These rotational speeds are within reason for motors like the Castle 2028s - those in our club are perfectly happy on 10S. Those are big props but on a cat you can run them high to unload the motors. Pitched up a bit they may get you to 100 mph.

I looked long and hard at the 1530 for a 10S single-motor cat project, but decided that it would not have the torque required to spin a 60+mm prop fast enough. I know the large-format motors like the 2215s, 2230s and 3060s have no problem with big props, in part due to the larger diameter rotor.

I would worry about spinning the Leos very fast. They have had known bearing problems (fixable but an added cost), and I don't know how their big magnets will stay in shape at 40,000 rpm. Will they spin a big prop fast enough? Don't know. They are "cheap" but the 2028s are not that much more considering the magnitude of your project. It is cheaper to buy enough motor the first time instead of buying cheap first, finding out that they don't work, then buying the right motors anyway.

Outrunners are rpm-limited, as much by the controller ability as by the motor construction. The Germans seem to do fine with boats this size using Lehners and Schulzes, but that is a top-end cost solution. To my mind for a sport boat you're better off using prop pitch and reasonable rpm to approach your speed goal. If you haven't posted it elsewhere I'd love to see a pic of this hull......



.

Thanks for the input. I was typing my post while you posted your and it looks like you addressed a few of the things I was considering.

I know from reading your posts for the last couple years that you favor turning a larger prop at a lower RPM, and I'm glad you chimed in. I am used to doing the opposite, as I've always been able to keep a hull in the water at high speeds easier with a smaller prop. Pehaps I have painted myself into a FE corner with my affinity for high RPM small prop...this project may force me to go another direction.

I like Neu motors, but it's hard to imagine I could get enough performance out of the 1530s when compared to 2028s.

[RaceMechaniX]

As Jay mentioned, the 2028's on 10S swinging a ~65mm prop will probbaly get you the closest to your target. 15 series Neu's are not going to make it.