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![]() "John Doe" wrote in message ... I have a Bosch 36 V lithium-ion hammer drill motor with batteries and charger. What sort of propeller would be appropriate to stick onto the shaft of that? Would a powered paraglider propeller be too big? I just want to get a rough idea of how much air that motor can push. Any experienced/educated guesses would be appreciated. After I looked at your question again, I see there is one answer I can give you. A powered parachute prop is made for around 30 some HP and up,. probably. Your drill motor is less than one HP. So no, a powered parachute propeller would be about 36 times too big. On top of that, that drill motor is probably designed to turn many more RPM's that a PP motor, so that would make it even more mismatched. You need to find some articles to read on model airplane electric motors, something that talks about the numbers a motor is rated for. I don't remember what those numbers are named, since I don't do electric... You can get two motors that put out the same HP, and draw the same number of watts, but one is designed to turn 3500 RPM's, while the other is designed to turn 12,000 RPM's. The slow one could have a regular two bladed prop mounted directly on the motor. The one that turns 12,000 would be designed to turn a ducted fan. (imitation fighter turbo-jet engine) Yet, they still put out the same power. The ducted engine would be only good at low amounts of thrust, but allow the jet to go really fast, while the prop plane would be able to take off in a shorter distance and climb steeply, but would cruise at much slower speeds. There is a lot to read online to help understand these subjects, if you look a little bit. It sounds like you would be interested. Look in places that talk about remote control airplanes, because that is what even the man carrying experimental airplanes are borrowing knowledge from, on the subject of electric flight. It is just at larger scales. -- Jim in NC |
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"Morgans" jsmorgan charterJUNK.net wrote:
"John Doe" jdoe usenetlove.invalid wrote in message I have a Bosch 36 V lithium-ion hammer drill motor with batteries and charger. What sort of propeller would be appropriate to stick onto the shaft of that? Would a powered paraglider propeller be too big? I just want to get a rough idea of how much air that motor can push. Any experienced/educated guesses would be appreciated. .... You can get two motors that put out the same HP, and draw the same number of watts, but one is designed to turn 3500 RPM's, while the other is designed to turn 12,000 RPM's. The slow one could have a regular two bladed prop mounted directly on the motor. The one that turns 12,000 would be designed to turn a ducted fan. (imitation fighter turbo-jet engine) Yet, they still put out the same power. The ducted engine would be only good at low amounts of thrust, but allow the jet to go really fast, while the prop plane would be able to take off in a shorter distance and climb steeply, but would cruise at much slower speeds. I will consider that when simulation flying. There is a lot to read online to help understand these subjects, if you look a little bit. It sounds like you would be interested. Look in places that talk about remote control airplanes, because that is what even the man carrying experimental airplanes are borrowing knowledge from, on the subject of electric flight. It is just at larger scales. Flight of the Phoenix (2004) ![]() I tried researching the printed numbers on the motor, but got nothing. Does the forward push on an ordinary electric motor cause abnormal wear on the bearings? Or maybe that is countered/supported by the magnetic part of the motor? |
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On 07/28/2010 10:53 AM, John Doe wrote:
"Morgans"jsmorgan charterJUNK.net wrote: "John Doe"jdoe usenetlove.invalid wrote in message I have a Bosch 36 V lithium-ion hammer drill motor with batteries and charger. What sort of propeller would be appropriate to stick onto the shaft of that? Would a powered paraglider propeller be too big? I just want to get a rough idea of how much air that motor can push. Any experienced/educated guesses would be appreciated. ... You can get two motors that put out the same HP, and draw the same number of watts, but one is designed to turn 3500 RPM's, while the other is designed to turn 12,000 RPM's. The slow one could have a regular two bladed prop mounted directly on the motor. The one that turns 12,000 would be designed to turn a ducted fan. (imitation fighter turbo-jet engine) Yet, they still put out the same power. The ducted engine would be only good at low amounts of thrust, but allow the jet to go really fast, while the prop plane would be able to take off in a shorter distance and climb steeply, but would cruise at much slower speeds. I will consider that when simulation flying. There is a lot to read online to help understand these subjects, if you look a little bit. It sounds like you would be interested. Look in places that talk about remote control airplanes, because that is what even the man carrying experimental airplanes are borrowing knowledge from, on the subject of electric flight. It is just at larger scales. Flight of the Phoenix (2004) ![]() I tried researching the printed numbers on the motor, but got nothing. Those numbers are DeWalt part, inventory, date code, or (not very likely) serial numbers. DeWalt would consider the motor specifications to be proprietary information, so you'll not get your hands on it! Even if the motor isn't made by DeWalt it'll still be custom made _for_ DeWalt, and the motor manufacturer would be contractually obliged not to divulge details. So you're kind of on your own there. Does the forward push on an ordinary electric motor cause abnormal wear on the bearings? Or maybe that is countered/supported by the magnetic part of the motor? It is _not_ supported by the magnetics. It may, indeed, cause objectionable wear -- that depends on whether the motor bearings can absorb the thrust of the prop (assuming you prop it directly). For all but outrunner motors, you'd want a gear box anyway. Any non-planetary gear box (or belt drive) will put a side load on the motor shaft, but its much more likely that the motor is designed for that. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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Tim Wescott tim seemywebsite.com wrote:
John Doe wrote: .... Does the forward push on an ordinary electric motor cause abnormal wear on the bearings? Or maybe that is countered/supported by the magnetic part of the motor? It is _not_ supported by the magnetics. It may, indeed, cause objectionable wear -- that depends on whether the motor bearings can absorb the thrust of the prop (assuming you prop it directly). For all but outrunner motors, you'd want a gear box anyway. How about a "thrust bearing"? "Handles thrust loads, also called an axial or side load, which is a load parallel to a shaft. Facilitates smooth rotation between surfaces like other rotary bearings, but their design supports higher thrust loads. Choose from plain and ball bearing designs. " -- Any non-planetary gear box (or belt drive) will put a side load on the motor shaft, but its much more likely that the motor is designed for that. -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html Path: news.astraweb.com!border2.newsrouter.astraweb.com! news-out.octanews.net!indigo.octanews.net!news.glorb.co m!postnews.google.com!news1.google.com!Xl.tags.gig anews.com!border1.nntp.dca.giganews.com!nntp.gigan ews.com!local2.nntp.dca.giganews.com!nntp.web-ster.com!news.web-ster.com.POSTED!not-for-mail NNTP-Posting-Date: Wed, 28 Jul 2010 14:09:29 -0500 Date: Wed, 28 Jul 2010 12:09:22 -0700 From: Tim Wescott tim seemywebsite.com User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.11) Gecko/20100713 Thunderbird/3.0.6 MIME-Version: 1.0 Newsgroups: rec.models.rc.air,rec.aviation.homebuilt Subject: What size propeller for a 36 V DC motor? References: 4c4a79ed$0$10434$c3e8da3 news.astraweb.com cHD3o.31959$o27.1368 newsfe08.iad 4c506eb6$0$32564$c3e8da3 news.astraweb.com In-Reply-To: 4c506eb6$0$32564$c3e8da3 news.astraweb.com Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Message-ID: 4JydnbyIjd_0Hc3RnZ2dnUVZ_oqdnZ2d web-ster.com Lines: 71 X-Usenet-Provider: http://www.giganews.com X-Trace: sv3-3f6ZqoviT9tUhuxFEwtz+e0eEar1X3L+uFi96q8mp/fWtGBbodHJVP8/QENBOQyVlP3qGSX4R7Haqp2!shd6REk2Bn6QAmn+u9kFW/8C6BKc6K08f2BCO44dFVpNARa+e+9MmzKxy7Kbayyd9e4ksbSa pgOK!WQ9ZDggqBsY8JWU= X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 |
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![]() Does the forward push on an ordinary electric motor cause abnormal wear on the bearings? Or maybe that is countered/supported by the magnetic part of the motor? Very good point. The bearings do take all of the load, called thrust, and it depends on the type of bearing whether it can stand the end load. Most likely that motor would not do well. It would be best to use a geared adapter to turn the prop, and that will remove the thrust load from the motor. Check model supply places for a suitable gearbox. I seriously doubt that you are going to get more than 8 pounds of thrust out of that motor, even with the ideal gearbox and prop. Probably not going to do well to move a person on skates. -- Jim in NC |
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On 07/28/2010 12:40 PM, Morgans wrote:
Does the forward push on an ordinary electric motor cause abnormal wear on the bearings? Or maybe that is countered/supported by the magnetic part of the motor? Very good point. The bearings do take all of the load, called thrust, and it depends on the type of bearing whether it can stand the end load. Most likely that motor would not do well. It would be best to use a geared adapter to turn the prop, and that will remove the thrust load from the motor. Check model supply places for a suitable gearbox. I seriously doubt that you are going to get more than 8 pounds of thrust out of that motor, even with the ideal gearbox and prop. Probably not going to do well to move a person on skates. I hadn't realized this was part of the whole skater thing. You'll do much better to drive the skate wheels with the motor -- driving a vehicle by pushing on the air is just not efficient, it makes little sense to do so if you can drive a wheel. (For obvious reasons you can't make an airplane go by driving the wheels -- hence, propellers). -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" was written for you. See details at http://www.wescottdesign.com/actfes/actfes.html |
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"Morgans" jsmorgan charterJUNK.net wrote:
.... I seriously doubt that you are going to get more than 8 pounds of thrust out of that motor, even with the ideal gearbox and prop. Probably not going to do well to move a person on skates. Right... Just depends on how easy it is to try. But maybe I can get a feel for what sort of electric motor would do. Propeller powered inline skating has been done with small gasoline/petrol motors. http://www.youtube.com/results?searc...e+jetpack&aq=f The first clip is on topic after the cool hang gliding introduction. But I would not want to use a noisy gasoline motor. Thanks. |
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"Morgans" jsmorgancharterJUNK.net wrote:
Look in places that talk about remote control airplanes, because that is what even the man carrying experimental airplanes are borrowing knowledge from, on the subject of electric flight. It is just at larger scales. I believe that, but how come you never see a real airplane standing on its tail? Looks like that would be a neat way to simulate a Harrier landing, and takeoff. |
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On Jul 30, 5:09*am, John Doe wrote:
"Morgans" jsmorgancharterJUNK.net wrote: Look in places that talk about remote control airplanes, because that is what even the man carrying experimental airplanes are borrowing knowledge from, on the subject of electric flight. *It is just at larger scales. I believe that, but how come you never see a real airplane standing on its tail? Looks like that would be a neat way to simulate a Harrier landing, and takeoff. Actually you can do it. It is just too expensive and dangerous. As for your project. The best is to experiment with it. As a starter, you should calculate the power that you need. Power is a function of battery, not motor. The motor rated power is the sustained power that the motor and windings can withstand for along time. the motor power is defined by rpm x torgue. rpm is proportional to voltage How much rpm can your motor stand for a short time, mechanically. torgue is proportional to current. How much current can your motor stand for a short time. Current creates heat so the limit is heat. If you can put cooling system to this motor you can operate it at high torgue, at least for a short time. Propeller theory. Propeller is just like a screw. How far does it go per RPM. At low speed, the air need not travel so fast, so low pitch is desirable. In order to increase the thrust, you need high volume running at low speed. Long propeller. You don't need maths. Just a sense of balance. So adjust the pitch and diameter of the propeller to match the voltage and current rating of your electric motor. You can exceed these ratings, but take special precautions, such as cooling the coils. In fact I like to experiment with overcurrent and its effects. Over RPM is dangerous because it is mechanical. Over current is just heat which we can control. |
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["Followup-To:" header set to rec.models.rc.air.]
On 2010-07-29, John Doe wrote: | "Morgans" jsmorgancharterJUNK.net wrote: | | Look in places that talk about remote control airplanes, because | that is what even the man carrying experimental airplanes are | borrowing knowledge from, on the subject of electric flight. It | is just at larger scales. | | I believe that, but how come you never see a real airplane | standing on its tail? Because you don't look in the right places? http://en.wikipedia.org/wiki/Lockheed_XFV http://en.wikipedia.org/wiki/Convair_XFY Ultimately, yes, for electric flight, most of the innovation is happening with models and UAVs because that's where it's more practical. Once you get into planes large enough to carry humans, the cost difference between electric and internal combustion becomes huge. For example, for a powered parachute, somebody mentioned a 30 hp engine. You could have that engine for a few hundred dollars, perhaps a thousand, but a comparable electric setup would cost way more, and something that will keep you up for an hour or two will weigh way more than the equivalent gasoline powered setup and cost even more. Full scale electric planes do exist, and I would expect more work in that area, but it's not going to really be practical for most uses until battery or fuel cell technology gets a lot better (or at least cheaper.) And also, if your model fails, you've got a pile of sticks to fix up. If your full scale plane fails, you might be dead. But good ideas certainly do flow in both directions. | Looks like that would be a neat way to | simulate a Harrier landing, and takeoff. Yes, though the examples I gave had massive problems. The first was never even taken off vertically! -- Doug McLaren, COFFEE.EXE missing - Insert cup and press any key. |
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