Friday, May 20, 2016

More Motors for more Hill Climbing Power
Two small recycled motors are better than one large expensive motor. But you still need two controllers. So learn to build them:

Multiple motors can pump-up the output thrust without increasing the top speed that is set by the fixed gear ratio. A controller for each motor is needed but then you can program them to power-up the extra motors when needed.

What are the advantages? Electric motors loose thrust ability when climbing hills at a slow speed; if you want your high speed gear-ratio to be set at about 20mph and you need a 10mph gear ratio to get enough thrust to climb your hill with only one motor, a second or third should provide enough thrust at 20mph without having to use a larger motor. The bigger motor would take more amperage to keep running at a high speed when cruising on flatter land, where the extra power is not needed. Also motors made for high speed are more efficient than slow speed motors; less energy is turned into heat. These are 3210 Astro Brushless Motors, they are very expensive and powerful. You can use cheaper motors.

Two speed reduction ratios?

I like the idea of using two motors separately the most. One with a large gear ratio reduction and the other with a higher speed reduction. Then the controllers set to turn on the slower gear reduction when needed and the other to turn off. Making it a two speed machine with the same legal wattage.

But with the right motor and gears, you don't really need two motors.

2WD Yuba Mundo V4 (Build Thread) 

Two stage reduction (for single hill climbing gear):

2" diameter pulley ÷ 12.5” rim pulley (on the drive wheel)= 6.25:1 ratio x 7:1 ratio (primary reduction) = 43.75:1 ratio = close to 12 mph

Dual motor

You can do this with One battery pack, One throttle, One 3-Way & Cruise & EBrake using Two controllers paralleled, Two motors individually tied to each controller, and Two CAs - one for each.

The overall power is divided somewhat arbitrarily between the two controllers depending on load.
  • Going uphill, both will pull evenly.
  • On somewhat of a flat whilst in Cruise Control, one will take the lead and the other will go into "slip mode"; pull enough current so that it essentially freewheels... however on the slightest increase in load - it will pick up the slack until Cruise cannot be held.

I don't measure Amps; I measure pack Voltage because the shunts have been modified by trace-beefing and I do not have equipment capable of measuring scant ohms accurately, so I just measure voltage. I know the battery capacity, I know from experience how to set the amount of theoretical current to the wheels, and thus am able to calculate roughly the overall power consumption. The CAs validate this by using Miles per charge; I know how many miles I should have covered by x-amount of voltage drop - which is not exactly linear, but then I understand that too.”


1 comment:

siemens said...

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