Kyosho conversion
02-15-2013, 03:52 AM
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Kyosho conversion
I have a nitro kyosho inferno neo r/s and just recently bought the brushless conversion for it. I was wondering what would be a good motor/esc combo for it? I know the ins and outs of the mechanical side of all my rc's, but I am still new to all the different motor setups. My 2 traxxas bashers still have the stock velineon system in them. I know tekin makes a good 1/8th setup, but I am not sure how the kv stuff works, is the higher the better or what? Thanks.
02-15-2013, 04:04 AM
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RE: Kyosho conversion
Hi there,
For a 1/8th buggy you should be looking at around 2000 to 2350 kv (higher is faster per volt; kv=rpm per volt supplied). Higher than 2350 unless geared very conservatively will get very warm especially off road, I personally feel that 2200kv is the sweet spot for a buggy, good speed and not too much heat.
Also, bear in mind that the Tekin system you mentioned is expensive and advanced, imed at dedicated racers. It will be fine for bashing around as well, but somewhat overkill. Expect to pay $300 or thereabouts for a the Tekin 2000kv truggy combo from official sources, perhaps cheaper on ebay (if you do go the Tekin route, get the truggy motors, not the buggy motors, more torque). There is also the famous Castle combo, with the 2200kv motor which is outstanding (and un-sensored, unlike the Tekin system which is sensored. If you're wondering what htis means, it means that the motor requires an additonal sensor cable, and starts up more smoothly). Personally, I do not value smooth startup enough to have the additional point of failure of the sensor and cable, for 1/8th stuff, I prefer simple non-sensored (like the Castle). The Castle is also nearly $300 over the counter, so is not cheap either.
Worth mentioning then, that you can get much cheaper and almost as good hobbywing combos from hobbypartz.com, which has a US warehouse. Consider that for a good 6S capable 2000kv hobbywing combo, you will pay only $190 and have almost no compromises compared to the expensive systems, they are just as powerful and just as reliable. Also consider if you really need to ever run 6S batteries, as equipment for only 4S use will be cheaper again. Going the 6S route obviously allows you to run 4S as well as 6S if the need ever takes you for totally insane power.
Here's some general electric info, no doubt some of it you know, hopefully some of it is useful too...
For a 1/8th buggy you should be looking at around 2000 to 2350 kv (higher is faster per volt; kv=rpm per volt supplied). Higher than 2350 unless geared very conservatively will get very warm especially off road, I personally feel that 2200kv is the sweet spot for a buggy, good speed and not too much heat.
Also, bear in mind that the Tekin system you mentioned is expensive and advanced, imed at dedicated racers. It will be fine for bashing around as well, but somewhat overkill. Expect to pay $300 or thereabouts for a the Tekin 2000kv truggy combo from official sources, perhaps cheaper on ebay (if you do go the Tekin route, get the truggy motors, not the buggy motors, more torque). There is also the famous Castle combo, with the 2200kv motor which is outstanding (and un-sensored, unlike the Tekin system which is sensored. If you're wondering what htis means, it means that the motor requires an additonal sensor cable, and starts up more smoothly). Personally, I do not value smooth startup enough to have the additional point of failure of the sensor and cable, for 1/8th stuff, I prefer simple non-sensored (like the Castle). The Castle is also nearly $300 over the counter, so is not cheap either.
Worth mentioning then, that you can get much cheaper and almost as good hobbywing combos from hobbypartz.com, which has a US warehouse. Consider that for a good 6S capable 2000kv hobbywing combo, you will pay only $190 and have almost no compromises compared to the expensive systems, they are just as powerful and just as reliable. Also consider if you really need to ever run 6S batteries, as equipment for only 4S use will be cheaper again. Going the 6S route obviously allows you to run 4S as well as 6S if the need ever takes you for totally insane power.
Here's some general electric info, no doubt some of it you know, hopefully some of it is useful too...
ORIGINAL: Foxy
Electric guidelines:
Motor
Motors come in 2 basic varieties; brushed and brushless. Brushed motors are older technology and are only really used still in classes that dictate you must use a brushed motor, and other applications that require very smooth throttle response and low speed control, such as Crawling and Drifting. Brushed motors need maintenance every so often, changing the brushes when they wear down and sometimes shaving a layer of metal off the commutator (using a 'comm lathe') to provide a better surface for the brushes.
Brushless motors are the newer technology, requiring no maintenance and delivering significantly more speed and power for the same ratings.
Both types of motor are rated in 'turns', with higher turns being more torque and less speed, and lower turns the opposite. Most brushless motors are also referred to as having a specific KV rating. This is a measure of their maximum rpm per volt. So, for example, if you see a brushless 10.5 turn 4000kv motor, it will turn 4000rpm for every volt supplied at maximum throttle. So the max speed (in rpm) of that motor on a 7.4v lipo battery will be 7.4*4000. In general consider that 3000kv or less is a fairly slow motor for high torque, and a 9000kv motor is a very fast, less torquey motor. The current a motor pulls on startup and under load (amps) goes up with the KV.
Speed controllers
Speed controllers also come in the brushed and brushless variety, indicating what kind of motor they can accept. There are many speed controls which can be switched or switch automatically between brushless and brushed operation. Running the wrong type of speed controller for the motor or running the wrong setting will destroy the speed controller and/or the motor in pretty short order.
The next things to look at on a speed controller are voltage and current ratings, which must not be exceeded. Often a speed controller (hereafter referred to as an ESC) will say first how many volts you can pump through it. Though this is often expressed in how many cells you can use (the number of cells your battery has). NimH old style batteries composed of a number of SubC cells are 1.2V per cell, and Lithium Polymer (lipo) batteries are rated at 3.7v per cell. You may see an ESC say '10 cell/3s max' This means 10 nimh cells (10*1.2=12v), or 3 lipo cells ('S' always refers to lipo cells) (3x3.7=11.1). Or the same speed controller may say 12v max. Once you have identified that the ESC can handle your batteries, you need to look at the current rating (maximum AMPS) and make sure your motor draw will not exceed that. Most motors will say how many amps they draw 'under load' and 'burst'. As long as those amps do not exceed the 'continuous' and 'burst' amp ratings of the ESC, you are good to go. As a general rule of thumb, 25A ESCs are for micro scale stuff, 40A ESCs will do for most 1/10th stuff, 60A ESCs are for the heavy duty (very high kv) 1/10th stuff, 80A for light duty 1/8th stuff, 120A for midrange 1/8th scale stuff, and 150-200A for the really big 1/8th scale stuff.
Batteries
Nimh batteries (made up of smaller 1.2v cells) need to be maintained. After a couple months being flat, they will rarely take a full charge again, at least not without careful resurrection using a complex cycling charger for many hours, apart from that, decent nimh cells should be fine for almost all your current needs, though cannot reach the performance of lipo.
Lipo batteries are a little more trouble, but overall lower maintenance. The thing about Lipos is that they could start a fire if mistreated. Mistreated means; overcharged, overdischarged, badly damaged. These batteries must never be allowed to drop below 2.9v per cell. If this happens, first of all there is the fire risk if high current is still being pulled through it, but also a battery overdischarged in this way will never take a full charge again, and may visibly 'swell'. Therefore it's critical when using lipo batteries to use a speed control that has an automatic lipo cutoff, ideally one which you can set. When I have the option, I always set my lipo cutoff to 3.0v per cell. (so when a 2s (2 cell) 7.4v battery reaches 6.0v, the ESC stops the power to prevent battery damage). These batteries also need to be regularly balanced to make sure that the batteries stay at the same voltage per cell so that the lipo cutoff works properly. The danger of an unbalanced battery, is that eventually, if one cell in the battery were to fall to 2.5v, yet the other was still at 3.6v, that wouldn't be low enough (combined=6.1v) to activate the cutoff, but the first cell is already damaged beyond repair, having dropped too low. Balancing your batteries prevents these voltage mismatches. Most lipo chargers include a balancing charge option, which will do this automatically.
The good thing about Lipos is that they charge fast (can be charged in an hour at the most, and many can be fully charged in half an hour), they do not lose much charge over time sitting around, they deliver incredible amounts of current, and last a very long time. Despite the extra care, these batteries are VASTLY superior to the other type, and I strongly recommend getting some and getting used to their idiosyncracies. Dont be put off by the extra care they require, follow these simple rules and they are very easy to own and will serve you well for many many charge cycles.
Charge and discharge rating... When you buy a lipo battery, as well as the number of cells (2S, 3S, 4S, etc, which determine the voltage, 7.4, 11.1, and 14.8 respectively), and the duration expressed in mAh (milliamp hours), you will also see a discharge rating, expressed in 'C', for example, '2s 7.4v 5000mAh 25C'. This means it is a 2 cell 7.4v battery which will last for 5000miliamp hours and the maximum discharge rate is 25C. The C rating is an expression of how much continuous current (Amps) the battery can deliver safely (exceeding this can damage the battery and/or the ESC). The C rating is calculated based on the capacity. So, 25C on a 5000mAh battery is 25x5 (remember 5000mA=5A), so this battery can deliver 125A of maximum continous current. A 40C battery of the same capacity would be able to deliver 200A of continuous current (40x5A=200A). Once again, it is important to match the battery to what your motor and ESC are capable of. To be honest, most batteries of 4000mAh or more at 20C or more are good enough for most applicatoins, it only starts to be a problem in the really high power 1/8th applications, where a 2650kv motor pulls say 150A regularly. You would need to make sure that the C rating of your battery multiplied by its capacity makes at least 150 in order not to risk damage to the battery and/or ESC
The same applies when charging. You may see a battery say it can be charged at 1C or 2C. Lets take the 5000mAh example again. 1C as we said=5A, 2C=10A etc. So a 'Charge at 2C' battery with 5000mAh capacity can be charged at 10A maximum.
Electric guidelines:
Motor
Motors come in 2 basic varieties; brushed and brushless. Brushed motors are older technology and are only really used still in classes that dictate you must use a brushed motor, and other applications that require very smooth throttle response and low speed control, such as Crawling and Drifting. Brushed motors need maintenance every so often, changing the brushes when they wear down and sometimes shaving a layer of metal off the commutator (using a 'comm lathe') to provide a better surface for the brushes.
Brushless motors are the newer technology, requiring no maintenance and delivering significantly more speed and power for the same ratings.
Both types of motor are rated in 'turns', with higher turns being more torque and less speed, and lower turns the opposite. Most brushless motors are also referred to as having a specific KV rating. This is a measure of their maximum rpm per volt. So, for example, if you see a brushless 10.5 turn 4000kv motor, it will turn 4000rpm for every volt supplied at maximum throttle. So the max speed (in rpm) of that motor on a 7.4v lipo battery will be 7.4*4000. In general consider that 3000kv or less is a fairly slow motor for high torque, and a 9000kv motor is a very fast, less torquey motor. The current a motor pulls on startup and under load (amps) goes up with the KV.
Speed controllers
Speed controllers also come in the brushed and brushless variety, indicating what kind of motor they can accept. There are many speed controls which can be switched or switch automatically between brushless and brushed operation. Running the wrong type of speed controller for the motor or running the wrong setting will destroy the speed controller and/or the motor in pretty short order.
The next things to look at on a speed controller are voltage and current ratings, which must not be exceeded. Often a speed controller (hereafter referred to as an ESC) will say first how many volts you can pump through it. Though this is often expressed in how many cells you can use (the number of cells your battery has). NimH old style batteries composed of a number of SubC cells are 1.2V per cell, and Lithium Polymer (lipo) batteries are rated at 3.7v per cell. You may see an ESC say '10 cell/3s max' This means 10 nimh cells (10*1.2=12v), or 3 lipo cells ('S' always refers to lipo cells) (3x3.7=11.1). Or the same speed controller may say 12v max. Once you have identified that the ESC can handle your batteries, you need to look at the current rating (maximum AMPS) and make sure your motor draw will not exceed that. Most motors will say how many amps they draw 'under load' and 'burst'. As long as those amps do not exceed the 'continuous' and 'burst' amp ratings of the ESC, you are good to go. As a general rule of thumb, 25A ESCs are for micro scale stuff, 40A ESCs will do for most 1/10th stuff, 60A ESCs are for the heavy duty (very high kv) 1/10th stuff, 80A for light duty 1/8th stuff, 120A for midrange 1/8th scale stuff, and 150-200A for the really big 1/8th scale stuff.
Batteries
Nimh batteries (made up of smaller 1.2v cells) need to be maintained. After a couple months being flat, they will rarely take a full charge again, at least not without careful resurrection using a complex cycling charger for many hours, apart from that, decent nimh cells should be fine for almost all your current needs, though cannot reach the performance of lipo.
Lipo batteries are a little more trouble, but overall lower maintenance. The thing about Lipos is that they could start a fire if mistreated. Mistreated means; overcharged, overdischarged, badly damaged. These batteries must never be allowed to drop below 2.9v per cell. If this happens, first of all there is the fire risk if high current is still being pulled through it, but also a battery overdischarged in this way will never take a full charge again, and may visibly 'swell'. Therefore it's critical when using lipo batteries to use a speed control that has an automatic lipo cutoff, ideally one which you can set. When I have the option, I always set my lipo cutoff to 3.0v per cell. (so when a 2s (2 cell) 7.4v battery reaches 6.0v, the ESC stops the power to prevent battery damage). These batteries also need to be regularly balanced to make sure that the batteries stay at the same voltage per cell so that the lipo cutoff works properly. The danger of an unbalanced battery, is that eventually, if one cell in the battery were to fall to 2.5v, yet the other was still at 3.6v, that wouldn't be low enough (combined=6.1v) to activate the cutoff, but the first cell is already damaged beyond repair, having dropped too low. Balancing your batteries prevents these voltage mismatches. Most lipo chargers include a balancing charge option, which will do this automatically.
The good thing about Lipos is that they charge fast (can be charged in an hour at the most, and many can be fully charged in half an hour), they do not lose much charge over time sitting around, they deliver incredible amounts of current, and last a very long time. Despite the extra care, these batteries are VASTLY superior to the other type, and I strongly recommend getting some and getting used to their idiosyncracies. Dont be put off by the extra care they require, follow these simple rules and they are very easy to own and will serve you well for many many charge cycles.
Charge and discharge rating... When you buy a lipo battery, as well as the number of cells (2S, 3S, 4S, etc, which determine the voltage, 7.4, 11.1, and 14.8 respectively), and the duration expressed in mAh (milliamp hours), you will also see a discharge rating, expressed in 'C', for example, '2s 7.4v 5000mAh 25C'. This means it is a 2 cell 7.4v battery which will last for 5000miliamp hours and the maximum discharge rate is 25C. The C rating is an expression of how much continuous current (Amps) the battery can deliver safely (exceeding this can damage the battery and/or the ESC). The C rating is calculated based on the capacity. So, 25C on a 5000mAh battery is 25x5 (remember 5000mA=5A), so this battery can deliver 125A of maximum continous current. A 40C battery of the same capacity would be able to deliver 200A of continuous current (40x5A=200A). Once again, it is important to match the battery to what your motor and ESC are capable of. To be honest, most batteries of 4000mAh or more at 20C or more are good enough for most applicatoins, it only starts to be a problem in the really high power 1/8th applications, where a 2650kv motor pulls say 150A regularly. You would need to make sure that the C rating of your battery multiplied by its capacity makes at least 150 in order not to risk damage to the battery and/or ESC
The same applies when charging. You may see a battery say it can be charged at 1C or 2C. Lets take the 5000mAh example again. 1C as we said=5A, 2C=10A etc. So a 'Charge at 2C' battery with 5000mAh capacity can be charged at 10A maximum.
