motor recommendations

[forescott]

8s in the 1090 will turn a little more rpm, but also the lower kv motor has more torque, therefore can spin a bigger prop.

[08gtrking]

8s in the 1090 will turn a little more rpm, but also the lower kv motor has more torque, therefore can spin a bigger prop.

how much more will the speed difference? be because it going to cost me a lot more to do the 8s set up

[keithbradley]

I like 8s on the 1090 better than 6s on the 1340. Keep current down and voltage up. There are a lot of guys with more boat experience than me here, but I've always liked to go with the highest cell count that I can reasonably fit in the hull and safely run through the esc. Once I figure out my cell count I pick the motor. Running a higher voltage/lower kv keeps current lower and temps down.

I currently have a 452 on my boat, the previous owner ran it with a 455. I have a 457 to try on it if I feel like it but for now I'm ok with staying conservative. Its Rumdog's old boat, ihe has a thread in the boat building section if you want to check it out.

[Ub Hauled]

go 60+ ,what cell count you thinkin about

If you have questions about the size of the motor still, get the measurements and do a mock up version... that will tell you what you need to know.
6s2p on dual drives... that sure is enough to get him to at least 60mph IMO..
granted that it's scratch build and hard to tell due to all the variables that may come from that... but normally, I believe it's doable
On 6s with the 1340kv, she'll be spinning almost 30,000rpm, which is a great range... on 8 it would be almost 40,000rpm... to much for sport driving...
running 6s you'll need HV escs for sure, choose wisely... since that could leave you with a bad taste in your mouth.

[08gtrking]

What the fastest speeds you think ill get with 6s on the 1340 and what is the speeds ill get on 8s with the1090?

[forescott]

I like 8s on the 1090 better than 6s on the 1340. Keep current down and voltage up. There are a lot of guys with more boat experience than me here, but I've always liked to go with the highest cell count that I can reasonably fit in the hull and safely run through the esc. Once I figure out my cell count I pick the motor. Running a higher voltage/lower kv keeps current lower and temps down.

I currently have a 452 on my boat, the previous owner ran it with a 455. I have a 457 to try on it if I feel like it but for now I'm ok with staying conservative. Its Rumdog's old boat, ihe has a thread in the boat building section if you want to check it out.

I thought I recognized that boat. Rum has some nice builds. with you on running higher voltage/low amp setups. It just gets more expensive when you make the jump from 6s. More batteries, and the esc's jump up quite a bit in price.

[keithbradley]

Yeah batteries can get pretty expensive. Thanks to the great customer service at Neutronics I just got 2 for free...that helps!

I think he is going to need a good esc (by good I mean something more than a $100 esc) to push that boat 60+ anyway. If he got a Swordfish 240 he could go either way.

I just ran my boat a couple hours ago on 8s with a 452 prop and after jammin on it for a good 5 minutes temps were 105 on batts, 106 on esc, and 97 on the hottest part of the motor. I love it!

[ray schrauwen]

Very Nice Keith! Thanks for the update. I'm waiting on a few more parts for my build.

I think I will try 8S2P and see what happens. Start off smal on the props... like a 450 oe something...

[keithbradley]

Just to clarify, Im running a Neu 2215 in my boat, not a leopard motor. They are a bit different, so your results with the Leopard may be a little different. I have a Leopard 4074 in my supervee though and it seems to run as good as the Neu 1515 I had in it prior.

[08gtrking]

so i did the horse power calculate and the the 1340 on 6s is 2.9hp and the 1090 on 8s is 5.7hp so i guess im going to go with 1090 on 8s but now i have to see which hardware to get if you guys can help me on this?

[LarrysDrifter]

so i did the horse power calculate and the the 1340 on 6s is 2.9hp and the 1090 on 8s is 5.7hp so i guess im going to go with 1090 on 8s but now i have to see which hardware to get if you guys can help me on this?

What is the formula to calculate hp?

[08gtrking]

What is the formula to calculate hp?

To calculate motor horse power

amps (X) volts (X) efficiency (divided by) 746 = horsepower.

Example: A 540 10XL was using 65 amps X 21.6 volts X .91 eff. / 746 = 1.7hp

[m4a1usr]

You cant get 90%+ eff out of any motor unless everything is perfect as in a testing facility. Plus the only way to achieve that level of eff is to only be in that narrow rpm band where things are as good as they are going to get. Above or below that torque eff band contains numbers very sobering. Like in the 50 to 70% eff. Typically if the motor is even capable of 90%+ eff you will only that possible in less than 10 to 15% of the motors rpm capability.

Another factoid that should always be remembered is even expensive custom hand built motors with a 90% dyno rating are simply very tough to achieve. Any motor manufacturer can spew numbers meant to imply their products are spectacular performers. And they might calculate that by just measuring wasted energy thru heat or btu's being radiated. Thats not how motor eff is calculated. Its a component. But not the definition. Its a bit more complicated then that.

I remember a post on RRR where Joerg was quoting most expensive Euro motors had something like an 80 to 85% eff at their peak performance. Guessing what the chi motors are at? Well,..........how about someone take one to Neu for a bit of testing. One of you guys has to know Steve.


John

[08gtrking]

do you guys think 630dollars is a lot for esc +motor + bats (2 set) + charger and servo ,not including hardware?

[Ub Hauled]

that's not much at all...
if you have to splurge on something in your system, get a decent ESC...
an HV ESC will not cost less then 260 bux, then 2p packs, motor charger and servo...
gee... add another 25% to that...

[forescott]

Yeah batteries can get pretty expensive. Thanks to the great customer service at Neutronics I just got 2 for free...that helps!

I think he is going to need a good esc (by good I mean something more than a $100 esc) to push that boat 60+ anyway. If he got a Swordfish 240 he could go either way.

I just ran my boat a couple hours ago on 8s with a 452 prop and after jammin on it for a good 5 minutes temps were 105 on batts, 106 on esc, and 97 on the hottest part of the motor. I love it!

I've been contemplating getting the 240. I know the one you have in rums old boat was sent back to OSE because it stopped working. When rum received it back it had clear shrink tube on it as opposed to black on the original. I never did hear if it was modified in some way to make it better. Sounds like its working like a champ though!

[keithbradley]

I've been contemplating getting the 240. I know the one you have in rums old boat was sent back to OSE because it stopped working. When rum received it back it had clear shrink tube on it as opposed to black on the original. I never did hear if it was modified in some way to make it better. Sounds like its working like a champ though!

Yeah it has 8 awg wire now, where they didnt before (not sure if it is the same esc or a new one). On the OSE site it says all the SF 240's come with 8 awg wire now. So far it hasnt broke a sweat on my current setup.

[keithbradley]

so i did the horse power calculate and the the 1340 on 6s is 2.9hp and the 1090 on 8s is 5.7hp so i guess im going to go with 1090 on 8s but now i have to see which hardware to get if you guys can help me on this?

You cant really do that because you dont know how many amps you are pulling. 746W=1hp, yes, but to get the boat up to the speed you want it to go is going to take a certain amount of power, regarless of how its done. You can accomplish 2000watts by supplying 100v@20A or by supplying 20v@100A. Thats why I said I like running the higher cell count---running a higher voltage to net you the same power with less current. The 1340kv will pull more current to go the same rpm where as the 1090kv will need more voltage but pull less current. Make sense?

[08gtrking]

yes

[08gtrking]

I did the run time calculated on 5000mah it said ill have around 2 min run times you guys think that's accurate?

[08gtrking]

Any hardware suggestions

[08gtrking]

Any hardware suggestions

any one?