Fly Quietly
New member
Brace yourself, this is a long e-mail, but I think worth it to outline the problem I am trying to solve. I have been requesting guidance from a few motor manufacturers and vendors and getting the polite brush off. Posting on other forums seems to get me referred to e-bike forums by the RC crowd and back to RC forums by the e-bike crowd. Hoping that Flite Test’s open mind towards breaking the odd piece of equipment may find me a culture that can answer a question that is a little outside of the ordinary.
I am a wheelchair user and am unable to push a lawnmower and transfer onto a riding mower is even somewhat beyond my ability. In order to solve the grass cutting problem, I have been working on a yardbot (or more strictly speaking yardROV I guess) project on and off for some time now. My next step is to build a dedicated grass cutting implement to be mounted on the front of this machine. In the video below, I have just taped a salvaged weed trimmer head from a cheap 18 volt trimmer onto the rover and am running it at 24 volts. This works better than I had anticipated. A linear actuator controls the height of the implement attachment on the front of the machine.
https://www.youtube.com/watch?v=eXzM3-uqgwk
I have previously considered a "cutting bar" type mower but have been unable to locate a suitable bar which is light enough for my purposes and centre driven (considered pilfering one off a hedge trimmer). Also considered towing a gas driven lawnmower, but this seems not a very elegant solution.
My current thinking is a cutting bar with two string trimmer heads powered by electric motors. The reason for multiple cutter heads is to keep centre of gravity close to the machine while still achieving a cutting width slightly wider than the machine wheelbase (24"). Similar machines seem to have been done:
https://www.hobbyking.com/hobbyking/forum/forum_posts.asp?TID=43019&PN=1
The difficulty I have been having is that most of the listings for hobby type motors and esc’s are not organized in a way which makes searching for the specifications which are important to my application easy. I am hoping that your experience might be valuable in pointing me in the right direction. I think the following should give an idea of what I am looking for:
• Capable of handling 24 volts
• 750 to 1000 kv (measured 10,000 rpm head speed on the trimmer in the video and lower KV should equal higher torque, correct?)
• At least 1000 watts total power or greater at 24 volts. Based on gas trimmers having 50 cc 2 cycles engines which should put out ~1 hp
• Sealed inrunner design for dusty/dirty environment
• Largest shaft size available due to possible side loading (i.e. “crash” into ground)
• Bearings capable of some occasional side-loading
• Built-in cooling fan or other option if necessary for extended run time
• ESC with amperage rating to match above
• Some form of telemetry might be nice in the ESC to gauge how hard I am running the motor, even after the fact
• Stall protection for motor and ESC
I likely will use a separate receiver (from the one which controls the ROV) mounted on the implement and bound alone to the AUX (preferred) or throttle channel on my 5ch. Spektrum transmitter. This would allow mounting of the implement without having to plug in more than the main power cable. It also means that any ESC I am using should be equipped with a battery elimination circuit to drive both the receiver and, if needed, an auxiliary motor cooling fan. I am willing to spend a bit on motors controllers etc. Consider the cost against purchase of a decent ride-on mower and I have a bit of budget (but still want to keep things reasonable of course). Any ESC considered should have (above all) good stall protection, again in anticipation of the odd “crash” of the trimmer head into the ground.
I am anticipating that I should be able to run pretty big motors (weight and running capacity) for long durations (in comparison with the hobby RC world) as I don't really have the amp/hours limitations of others who have modified hand-held trimmers with outrunner motors. I am running things off of two G22NF wheelchair batteries rated at 55 amp hours. Weight is not an issue and the amp hours available to me are pretty far in excess of those who have modified hand-held trimmers run on Li/po batteries.
Options I have considered so far include the Castle Creations 2028 780kV Sensorless Brushless Motor / Mamba XL 2 34V 8S LiPo 5A BEC Electronic Speed Control Combo. Drawbacks of this system seem to be cost (going to cost me >$1000.00 Cdn.for two units) and complete overkill at something like 10 horsepower capability each motor. I’ve also considered the Turnigy Typhoon Ferrous Loss Free Helicopter Motor 800kv and 120 amp Super Brain ESC. Actually bought this setup just to see what it looked like – exactly the same size motor as seen in the video above. However, the issue with this setup, as far as I can tell, is that the motor is not sealed and has an internal cooling fan. My concern is that, without some elaborate shroud and air filtering system the motor will suck in dirt resulting in damage. I have looked at the e-bike community forums as well, hoping to find a brushed motor or something there. However, the motors commonly used in these applications are commonly outrunners (seem like the revolving can would be susceptible to damage) or cannot achieve the power/speed requirement. The general difficulty I am having seems to be finding something with a low kV value (for high torque) which also runs at 24 volts and is sealed against the elements. However, I know these motors must be possible as cordless line trimmers are a dime a dozen and I can’t imagine the hobby motors I am seeing aren’t built to 10x the capability and quality of cheap Chinese consumer goods motors. I feel like I just need to find the right product.
I realize that this enquiry is way outside of the typical applications seen in this forum. However, I am hoping that someone here may find my problem and end goal interesting enough to consider offering me the benefit of their experience and “feel” for what may work for me.
Any advice to assist me in achieving what I am out to do without creating too much expensive white smoke would truly be appreciated. Am I even on the right track? Feel free to spec this whole thing out for me. Spend my money.
I do understand that I would be running this equipment in a manner that would void any warranty offered. Anywhere.
I am a wheelchair user and am unable to push a lawnmower and transfer onto a riding mower is even somewhat beyond my ability. In order to solve the grass cutting problem, I have been working on a yardbot (or more strictly speaking yardROV I guess) project on and off for some time now. My next step is to build a dedicated grass cutting implement to be mounted on the front of this machine. In the video below, I have just taped a salvaged weed trimmer head from a cheap 18 volt trimmer onto the rover and am running it at 24 volts. This works better than I had anticipated. A linear actuator controls the height of the implement attachment on the front of the machine.
https://www.youtube.com/watch?v=eXzM3-uqgwk
I have previously considered a "cutting bar" type mower but have been unable to locate a suitable bar which is light enough for my purposes and centre driven (considered pilfering one off a hedge trimmer). Also considered towing a gas driven lawnmower, but this seems not a very elegant solution.
My current thinking is a cutting bar with two string trimmer heads powered by electric motors. The reason for multiple cutter heads is to keep centre of gravity close to the machine while still achieving a cutting width slightly wider than the machine wheelbase (24"). Similar machines seem to have been done:
https://www.hobbyking.com/hobbyking/forum/forum_posts.asp?TID=43019&PN=1
The difficulty I have been having is that most of the listings for hobby type motors and esc’s are not organized in a way which makes searching for the specifications which are important to my application easy. I am hoping that your experience might be valuable in pointing me in the right direction. I think the following should give an idea of what I am looking for:
• Capable of handling 24 volts
• 750 to 1000 kv (measured 10,000 rpm head speed on the trimmer in the video and lower KV should equal higher torque, correct?)
• At least 1000 watts total power or greater at 24 volts. Based on gas trimmers having 50 cc 2 cycles engines which should put out ~1 hp
• Sealed inrunner design for dusty/dirty environment
• Largest shaft size available due to possible side loading (i.e. “crash” into ground)
• Bearings capable of some occasional side-loading
• Built-in cooling fan or other option if necessary for extended run time
• ESC with amperage rating to match above
• Some form of telemetry might be nice in the ESC to gauge how hard I am running the motor, even after the fact
• Stall protection for motor and ESC
I likely will use a separate receiver (from the one which controls the ROV) mounted on the implement and bound alone to the AUX (preferred) or throttle channel on my 5ch. Spektrum transmitter. This would allow mounting of the implement without having to plug in more than the main power cable. It also means that any ESC I am using should be equipped with a battery elimination circuit to drive both the receiver and, if needed, an auxiliary motor cooling fan. I am willing to spend a bit on motors controllers etc. Consider the cost against purchase of a decent ride-on mower and I have a bit of budget (but still want to keep things reasonable of course). Any ESC considered should have (above all) good stall protection, again in anticipation of the odd “crash” of the trimmer head into the ground.
I am anticipating that I should be able to run pretty big motors (weight and running capacity) for long durations (in comparison with the hobby RC world) as I don't really have the amp/hours limitations of others who have modified hand-held trimmers with outrunner motors. I am running things off of two G22NF wheelchair batteries rated at 55 amp hours. Weight is not an issue and the amp hours available to me are pretty far in excess of those who have modified hand-held trimmers run on Li/po batteries.
Options I have considered so far include the Castle Creations 2028 780kV Sensorless Brushless Motor / Mamba XL 2 34V 8S LiPo 5A BEC Electronic Speed Control Combo. Drawbacks of this system seem to be cost (going to cost me >$1000.00 Cdn.for two units) and complete overkill at something like 10 horsepower capability each motor. I’ve also considered the Turnigy Typhoon Ferrous Loss Free Helicopter Motor 800kv and 120 amp Super Brain ESC. Actually bought this setup just to see what it looked like – exactly the same size motor as seen in the video above. However, the issue with this setup, as far as I can tell, is that the motor is not sealed and has an internal cooling fan. My concern is that, without some elaborate shroud and air filtering system the motor will suck in dirt resulting in damage. I have looked at the e-bike community forums as well, hoping to find a brushed motor or something there. However, the motors commonly used in these applications are commonly outrunners (seem like the revolving can would be susceptible to damage) or cannot achieve the power/speed requirement. The general difficulty I am having seems to be finding something with a low kV value (for high torque) which also runs at 24 volts and is sealed against the elements. However, I know these motors must be possible as cordless line trimmers are a dime a dozen and I can’t imagine the hobby motors I am seeing aren’t built to 10x the capability and quality of cheap Chinese consumer goods motors. I feel like I just need to find the right product.
I realize that this enquiry is way outside of the typical applications seen in this forum. However, I am hoping that someone here may find my problem and end goal interesting enough to consider offering me the benefit of their experience and “feel” for what may work for me.
Any advice to assist me in achieving what I am out to do without creating too much expensive white smoke would truly be appreciated. Am I even on the right track? Feel free to spec this whole thing out for me. Spend my money.
I do understand that I would be running this equipment in a manner that would void any warranty offered. Anywhere.
