a quick update as the taiyo edge hovercraft
has had a couple of alterations as it has been working reliably for hours now, as I was always worried about amount of play time vs the speed of the hovercraft (and how much current the motor would be happy pulling). So in this form the current draw of the thrust motors was 7 amps each, but when I changed to a 4 bladed prop with a full battery, the current draw went up to just below 9 amps, but the hovercraft was now planing so it was like going up a gear, and as the voltage loss between the battery and motor was over 0.6V that was roughly 15% of the power lost, so I ditched the original forward/reverse speed controllers and replaced it with forward only speed controllers that I made earlier in this thread.
but instead of using 1 mosfet I used 3 in parallel to reduce the current loss. I did have issues with this working though but a 1K0 current limiting resistor between the servo driver and mosfets sorted that out. I think it could have been the increased capacitance of the mosfets which was increasing the current draw from the servo driver which kept the drive voltage low so the mosfest did start working until a second after power was applied. I also increased the gauge of the wires, so now the voltage drop at 10A was 0.14V and only 0.04V of that was across the mosfets. and now it was planing so the steering at full power can be interesting.
the brushed motors can handle 10 amps, but they were getting a bit warm now as the 50% increase in current draw created more heat so what can you do to cool them?
well this is a hovercraft so, and the air from the lift motor is trying to escape from the body, and as the housings for the thrust motors arn't sealed from main body have the air under light pressure too, so the simple answer is to let the air go past the motor to cool it. but as the heat is generated in the motor, you can use the air more efficiently by going though the motor. in this case is just a case of making a couple of holes bigger, but its an complicated shape to hold, so after a bit of thinking it the propeller housing was held in a 4 jaw chuck and a step drill was used to enlarge the holes from 8mm to 20mm using a pillar drill.
and the new setup
and after 5 minutes continuous running the motor housings arn't warm, although the air going though the motors is, so that was a simple answer to that problem
has had a couple of alterations as it has been working reliably for hours now, as I was always worried about amount of play time vs the speed of the hovercraft (and how much current the motor would be happy pulling). So in this form the current draw of the thrust motors was 7 amps each, but when I changed to a 4 bladed prop with a full battery, the current draw went up to just below 9 amps, but the hovercraft was now planing so it was like going up a gear, and as the voltage loss between the battery and motor was over 0.6V that was roughly 15% of the power lost, so I ditched the original forward/reverse speed controllers and replaced it with forward only speed controllers that I made earlier in this thread.
but instead of using 1 mosfet I used 3 in parallel to reduce the current loss. I did have issues with this working though but a 1K0 current limiting resistor between the servo driver and mosfets sorted that out. I think it could have been the increased capacitance of the mosfets which was increasing the current draw from the servo driver which kept the drive voltage low so the mosfest did start working until a second after power was applied. I also increased the gauge of the wires, so now the voltage drop at 10A was 0.14V and only 0.04V of that was across the mosfets. and now it was planing so the steering at full power can be interesting.
the brushed motors can handle 10 amps, but they were getting a bit warm now as the 50% increase in current draw created more heat so what can you do to cool them?
well this is a hovercraft so, and the air from the lift motor is trying to escape from the body, and as the housings for the thrust motors arn't sealed from main body have the air under light pressure too, so the simple answer is to let the air go past the motor to cool it. but as the heat is generated in the motor, you can use the air more efficiently by going though the motor. in this case is just a case of making a couple of holes bigger, but its an complicated shape to hold, so after a bit of thinking it the propeller housing was held in a 4 jaw chuck and a step drill was used to enlarge the holes from 8mm to 20mm using a pillar drill.
and the new setup
and after 5 minutes continuous running the motor housings arn't warm, although the air going though the motors is, so that was a simple answer to that problem
