Cheap Motor(s) For Experimental Snowmobile?

[electromateria]

I'm thinking 4 of the same type of washing machine motor driving a track. They're free to salvage and powerful / lots of torque from what I hear. Is there any issue powering and controlling 4 of these at once? I want to keep things as cheap as possible while pushing LOTS of power.

I don't really want to spend money on expensive motors and a speed control unit. I want to build something out of salvaged parts.

What's the best battery type and how many would I need to power the motors for 30 mins? (ideally the batteries could be quickly swapped into other projects)



 

[amyk]

Could you be more specific? To my knowledge, washing machines have used universal motors (series, brushed) and various forms of induction motors.

[james_s]

Washing machines have used all sorts of motors. Traditionally American machines used single phase induction motors while British/European machines used series wound universal motors. In the early 2000's some American front load washers started using switched reluctance motors and other washers used direct drive BLDC motors. I think now most front loaders use BLDC motors and top loaders I think still use induction motors. The induction and switched reluctance motors aren't very powerful by vehicle standards, maybe 1/4hp. BLDC motors can be rewound to develop substantially more power. Automotive alternators can also be converted into fairly powerful BLDC motors.

[floobydust]

How cold ?  Batteries perform quite poor at Canadian winter temperatures. You'd benefit from transferring motor heat to the batteries.

[Ian.M]

A BLDC or VFD controlled induction motor in a washing machine is likely to be designed to run at mains voltage, so isn't suitable for operation from a low voltage battery pack without rewinding.     As James suggested, look at automotive alternators. Its relatively simple to remove the diode plate and reguator, and bring out the three stator winding connections and the brush connections for the field.  At its simplest you can apply a fixed field current via a rheostat and drive the stator with a sensorless BLDC controller, though better performance can be achieved by driving the field with a PWM controller to maintain a target current, increasing it for more torque at low speed and decreasing it to reduce the voltage required to operate at high speed.

See https://hackaday.com/2020/01/16/car-alternators-make-great-electric-motors-heres-how/

[Nominal Animal]

How cold ?  Batteries perform quite poor at Canadian winter temperatures. You'd benefit from transferring motor heat to the batteries.

Do you happen to know what happens when a fully-charged Li- or NiMH battery (say, charged at +10'C battery temperature) gets cold (say, slowly cools to -25'C)?

I am still not sure if it is just the capability of releasing the stored energy that diminishes as temperature decreases, or if there is a chemical reaction that actually damages the battery (similar to overcharging).  Or, whether the excess energy is harmlessly turned to heat, essentially just slowing down the cooling of the battery.

[Circlotron]

If you used a converted car alternator you would have to use a sensorless BLDC controller. Unlike sensor type ones, these don't always work well at very low speeds. Also, at startup they make the motor jiggle back and forth a little to generate a bit of back emf so the controller can figure out what's going on. If the motor is held more or less stationary by the mass of whatever it is connected to (e.g. road wheels) so that it can't do this initial jiggle it may not actually begin to rotate. Best to try it on something first.

[joeqsmith]

Interesting project.   Any idea on the total weight or the machine and riders?  The target speed, range?   Really the part I am curious about, the amount of loss trying to drive the track.   

[Syntax Error]

What is the power to weight ratio of four washing machine motors at apx 500 watts each plus battery pack, versus a 2.5hp gasoline engine with fuel tank? Better or worse? And how would you sync (consist) the motors so they were outputting the same rpm/torque?

[fcb]

I know virtually nothing about snow-mobiles, but I do know electric cars, bikes, motor-bikes and boats.

I'd imagine 2.5HP would barely get over the friction of the tread bearings/rollers, probably require at least 10x that to make progress on anything other than level ground at more than walking pace.

The battery temperature would defo need to be considered - would suggest large aluminium clad LiFePO4 cells with an insulated jacket round them (and the inverter) and perhaps a heater resistor to keep them above freezing if the vehicle is left outside for long periods.  You can take LiFePO4 cells to something like -15C (5F), but have to warm them up evenly with a gentle charge before thwacking them.

[Nominal Animal]

I'd imagine 2.5HP would barely get over the friction of the tread bearings/rollers, probably require at least 10x that to make progress on anything other than level ground at more than walking pace.

The track isn't that lossy, although you're not far off.

A good comparison machine would be Ski-Doo Elan (1971-1996): weighed about 140 kg, with a 12 to 24 hp motor.

I drove one lots when a child, and although nothing like the current speed beasts, it could drag a sled with people and skiers behind it at respectable speeds.  I'd guess 12 hp ≃ 9 kW would suffice for the snowmobile to be useful, and reach speeds of say 60 km/h on ice or hard-packed snow, and be able to climb at least modest hillsides.

Something like 5 kW would probably be unable to pull anything, but might still work as a single-person conveyance, say something to let kids ride in controlled conditions.

(The best thing about the Elan was that if you got stuck, it was light enough to lift solo.  I don't mean clear off the ground, I mean enough to turn it around and return using the track you already made.  If you had a snow shovel with you, getting stuck wasn't that big of a deal.  With the current speed beasts with their narrow tracks and heavier weight, I'd be much more worried about getting stuck in snowdrifts.  Which reminds me: weight distribution is also very important to make it ride-able.  You don't want it to be so front-heavy it becomes a snow-submarine, nor so front-light the skids won't steer.)