brushless motor

[bob miller]

does anyone make a brushless motor that produces more torque than rpm , i'm looking for a new motor for my electric retreival boat , i need something that has the power to push heavy gas boats back to shore , i'm currently using a 12 volt automotive bosch motor with a 12 volt 8 amp starter battery , i'm looking to update to more current technology...thanks...bob

 

[lohring]

All electric motors have huge torque at low rpm. Unlike internal combustion motors that quit when overloaded, electric motors keep generating more torque until something melts. I've watched propeller blades break from water loads, set screws sheer the tips off and lots of motors melt the insulation. To answer your question, brushless electric motors have a KV rating. This is the free running rpm per volt from the speed control. You probably don't want to load the motor a long way below that calculated rpm. Outrunner motors usually have lower KV than inrunner motors.

You want to run a low pitch propeller for the most thrust at low speeds. If you are happy with the performance of your current setup, a brushless motor setup with lithium polymer batteries will be much smaller and lighter. Let me know the propeller, rpm,and approximate current draw and I can be more specific about a low cost system.

Lohring Miller

 

[bob miller]

All electric motors have huge torque at low rpm. Unlike internal combustion motors that quit when overloaded, electric motors keep generating more torque until something melts. I've watched propeller blades break from water loads, set screws sheer the tips off and lots of motors melt the insulation. To answer your question, brushless electric motors have a KV rating. This is the free running rpm per volt from the speed control. You probably don't want to load the motor a long way below that calculated rpm. Outrunner motors usually have lower KV than inrunner motors.

You want to run a low pitch propeller for the most thrust at low speeds. If you are happy with the performance of your current setup, a brushless motor setup with lithium polymer batteries will be much smaller and lighter. Let me know the propeller, rpm,and approximate current draw and I can be more specific about a low cost system.

Lohring Miller

lohring , thanks for your input, i'm currently use a 12 volt 8 amp starting battery to power a 12 volt , 10000 rpm automotive motor made by bosch , the motor is mounted to a K/B 45 outboard unit, i'm using a plastic yellow prop that was included with the 45 K/B , don't know the size....i would like to continue using the outbord unit , i need a electric motor that can push heavy boats back to shore and run a long time on one battrey....how long would a lithium polymer battery power an appropriate motor for my needs?....the motor usually runs at a low rpm , never near its full potenial , i don't know the current draw , the battery with a full charge can last about one hour of constant use...bob

 

[lohring]

All the current brushless motors can be mounted on your K&B drive with this adapter:

http://hyperprod.bizhosting.com/7_5_electric_outboard_conversion_kit.html

An outrunner motor like this will give you a little more (around 15,000 loaded)rpm:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11102

This battery http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9963 with this speed control http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8946 should run your boat at least as well as it does now. It's hard to predict how long everything will run without knowing the current draw. This setup can handle 80 amps which would only give you 3 minutes running time. A draw of 5 amps would give you nearly an hour. It all depends on the prop. Putting more batteries in parallel gives you more run time. Each pack will run about an hour at 5 amps, so two packs would support 10 amps for an hour.

You will need bullet connectors like these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=2087 and a balancing charger like this http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14857 That charger will take an hour to charge each battery. Better chargers can charge two batteries in 1/2 hour.

Lithium polymer batteries are much tougher than lead acid batteries. They maintain their voltage even under high current draws. They have limitations, though. Their shelf life is around 2 years regardless of use. They MUST be charged with a balancing charger. Their very low internal resistance means that they discharge VERY quickly if shorted. They are expensive. I think you can run the above motor and speed control with lead acid batteries. The performance will be poorer since the lithium polymer battery will hold close to 15 volts for most of the discharge cycle.

Lohring Miller

 

[raptor347]

Bob,

Just a rough calculation from the numbers you posted. You're running ~100watts average and the motor has roughly 825kV. There are lots of motors that will match the performance of what you're running now.

You can parallel a couple 4S 5000mah LiPos and up your capacity by 25% a well as save weight. Plus you can fast charge the pack with the proper charger. You don't need high discharge rate cells, so you can go cheap on the packs.

There are lots of ways to build what you want, depends a lot on how much you want to spend. Here's a combination that should be pretty much bullet proof for your application. Everything is rated at 10x the calculated load.

Motor:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11143

ESC:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7360

Battery:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6500

FWIW. that at least gives you an idea of what you're looking for. This is assuming you want to match or exceed the towing power of what you have now.

 

[bob miller]

All the current brushless motors can be mounted on your K&B drive with this adapter:

http://hyperprod.bizhosting.com/7_5_electric_outboard_conversion_kit.html

An outrunner motor like this will give you a little more (around 15,000 loaded)rpm:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11102

This battery http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9963 with this speed control http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8946 should run your boat at least as well as it does now. It's hard to predict how long everything will run without knowing the current draw. This setup can handle 80 amps which would only give you 3 minutes running time. A draw of 5 amps would give you nearly an hour. It all depends on the prop. Putting more batteries in parallel gives you more run time. Each pack will run about an hour at 5 amps, so two packs would support 10 amps for an hour.

You will need bullet connectors like these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=2087 and a balancing charger like this http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14857 That charger will take an hour to charge each battery. Better chargers can charge two batteries in 1/2 hour.

Lithium polymer batteries are much tougher than lead acid batteries. They maintain their voltage even under high current draws. They have limitations, though. Their shelf life is around 2 years regardless of use. They MUST be charged with a balancing charger. Their very low internal resistance means that they discharge VERY quickly if shorted. They are expensive. I think you can run the above motor and speed control with lead acid batteries. The performance will be poorer since the lithium polymer battery will hold close to 15 volts for most of the discharge cycle.

Lohring Miller

thanks for the info , it looks like i have a lot to learn about up dating my equipment, i'm looking forward to assembling a new system....bob

 

[bob miller]

Bob,

Just a rough calculation from the numbers you posted. You're running ~100watts average and the motor has roughly 825kV. There are lots of motors that will match the performance of what you're running now.

You can parallel a couple 4S 5000mah LiPos and up your capacity by 25% a well as save weight. Plus you can fast charge the pack with the proper charger. You don't need high discharge rate cells, so you can go cheap on the packs.

There are lots of ways to build what you want, depends a lot on how much you want to spend. Here's a combination that should be pretty much bullet proof for your application. Everything is rated at 10x the calculated load.

Motor:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11143

ESC:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=7360

Battery:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=6500

FWIW. that at least gives you an idea of what you're looking for. This is assuming you want to match or exceed the towing power of what you have now.

raptor , thanks for the advise bob

 

[bob miller]

All the current brushless motors can be mounted on your K&B drive with this adapter:

http://hyperprod.bizhosting.com/7_5_electric_outboard_conversion_kit.html

An outrunner motor like this will give you a little more (around 15,000 loaded)rpm:

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11102

This battery http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=9963 with this speed control http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=8946 should run your boat at least as well as it does now. It's hard to predict how long everything will run without knowing the current draw. This setup can handle 80 amps which would only give you 3 minutes running time. A draw of 5 amps would give you nearly an hour. It all depends on the prop. Putting more batteries in parallel gives you more run time. Each pack will run about an hour at 5 amps, so two packs would support 10 amps for an hour.

You will need bullet connectors like these http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=2087 and a balancing charger like this http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=14857 That charger will take an hour to charge each battery. Better chargers can charge two batteries in 1/2 hour.

Lithium polymer batteries are much tougher than lead acid batteries. They maintain their voltage even under high current draws. They have limitations, though. Their shelf life is around 2 years regardless of use. They MUST be charged with a balancing charger. Their very low internal resistance means that they discharge VERY quickly if shorted. They are expensive. I think you can run the above motor and speed control with lead acid batteries. The performance will be poorer since the lithium polymer battery will hold close to 15 volts for most of the discharge cycle.

Lohring Miller

lohring , will this motor and esc run in reverse , i need a reverse ...bob

 

[lohring]

The Hobbyking ESC has the option to program in reverse. It comes with this disabled and transmitter programming is hard to do. They make a programmer that I have, but I haven't started toi use it.

Lohring Miller