Why are military generators so big?

[jimbo913]

In regards to the Military fuel/durability testing, it seems strange that they would document the generator failures in the test when they had no clue how many hours were on the generators or the maintenance history. The only new unit was a 30kw.

 

[m16ty]

Mine is self portable. 500 watt 24 volt DC motor driving a 2 speed riding mower transaxle and front steering axle with a draw-steer bar and directional control switch. All surplus gear I fabricated, welded and bolted together. Even got the reduction ratio about right. Low gear climbs the steepest gradient on the property, high gear is a slow walking pace.

That's a pretty slick setup when you don't have other means to move it easily.

I have to ask though, why go with a DC motor and not a AC motor?

 

[rustystud]

That's a pretty slick setup when you don't have other means to move it easily.

I have to ask though, why go with a DC motor and not a AC motor?

I was wondering about that also. Was it so you didn't have to start up the generator to move it ?

 

[Rebel635]

Its pretty obvious. 24DC batteries onboard the generator are all ready there. 24V DC motor controllers are cheap and plentiful from all the electric bikes as well as the 24V DC motors.

That's a pretty slick setup when you don't have other means to move it easily.

I have to ask though, why go with a DC motor and not a AC motor?

 

[m16ty]

Its pretty obvious. 24DC batteries onboard the generator are all ready there. 24V DC motor controllers are cheap and plentiful from all the electric bikes as well as the 24V DC motors.

You've also got 5kw of ac power already on board.

I suspect the reason he went with a dc motor is that's just what he had lying around. Nothing wrong with a 24v dc motor, you'd just pull a lot less amps on 120v.

 

[Rebel635]

AC voltage motor controllers and motors are a lot more expensive than DC stuff.

 

[Keith_J]

I was wondering about that also. Was it so you didn't have to start up the generator to move it ?

I didn't need it to go fast, 500 watts is a bit over 1/2 HP so I ran numbers looking at a walking pace, gear ratio torque multiplication and percent grade it would need to climb at 1200 pounds. And bam, there it was.

Yes, it really needs a speed controller if the motor was any more powerful. What I used instead of a speed controller is a directional control switch and a nifty little component called a negative temperature coefficient variresistor. This component starts off at about 2 ohms of resistance, when it gets warm from the current flowing through it to the motor, the resistance drops to a few milliohm. What it does is just a soft start motor.

500 watts at 24 volts is 21 amps, give or take. Nothing 12 gauge wire cannot handle easily. Plus I tap the slave port for the power.

 

[Keith_J]

You've also got 5kw of ac power already on board.

I suspect the reason he went with a dc motor is that's just what he had lying around. Nothing wrong with a 24v dc motor, you'd just pull a lot less amps on 120v.

I bought the motor from the same surplus shop where I got the lawn tractor transaxle, wheels and directional control switch. If I were REALLY ambitious, it would have been hydrostatic.