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But you aren't running any implements off the PTO...
Motor for small tractor
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If you overvolted it to 60v you would almost have 4kW 3720w about 5hp although I doubt it is a continuous rated motor especially with the overvolting.
later floyd
Remember that motor ratings are typically Continuous and ICE ratings are Peak. But a bigger motor won't heat up as much. You can typically go quite high on voltage with brushed motors but you wouldn't need to. My Electrak is a 36V system and while I only use it cut grass these days, for many years I also moved snow with it. I don't know how much current it draws but I'll bet max output's in the 2-4 HP range.
Oh - for inspiration:
John's gone now but he always had an interesting perspective on things.
Oh - for inspiration:
John's gone now but he always had an interesting perspective on things.
This article discusses his tractor in more detail (near the bottom) and gives some operating parameters: Mother Earth News
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Not sure if this helps, I had a GT3000 with an ME1004 for many years. it was a 48V system, with an Alltrax controller.
It would pull about 20A tooling around with a small trailer. It had no problems moving a heavy load - it could tow our water trailer (5000lbs) around, but traction was a problem on anything but flat.
One mistake I made was to put the batteries up front - it made steering very heavy.
Good luck with the project!
It would pull about 20A tooling around with a small trailer. It had no problems moving a heavy load - it could tow our water trailer (5000lbs) around, but traction was a problem on anything but flat.
One mistake I made was to put the batteries up front - it made steering very heavy.
Good luck with the project!
This is mine during early testing:
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It works, but not the most efficient setup due to hydrostatic transmission and the belt/pulleys. Eventually I want to shove a Chinese transaxle with a motor onto it, and keep the front motor for running the deck only. No motor controller used - motor runs straight from the battery, which reduces the cost of the conversion.
It works, but not the most efficient setup due to hydrostatic transmission and the belt/pulleys. Eventually I want to shove a Chinese transaxle with a motor onto it, and keep the front motor for running the deck only. No motor controller used - motor runs straight from the battery, which reduces the cost of the conversion.
But that's not true. Electric motors are routinely rated according to various non-continuous duty cycles.
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I think part of the reason you are having trouble finding the right motor is because you are focusing on the wrong things. The original ICE engine has 12hp but that is not directly comparable to an electric motor.
Horsepower is a function of torque, so what you really want is an electric motor that makes 12hp at 3600 RPM. That is about 18 ft-lbs at 3600 RPM.
Motors are rated for an RPM usually at a certain voltage. More voltage more RPM, less voltage less RPM. So a secondary consideration is if you pick a motor that has a maximum RPM at a certain voltage, then when the battery is low the maximum RPM will also be lower. So you want to pick a motor/battery combination that will allow you to have a full range of usable power through the full range of usable battery voltage.
Also note that maximum RPM is also a lot of time rated with no load on the motor, so if you add a load the RPM will be lower.
I would also open up the idea of 72 or even 96 volts. More voltage more RPM more area under the curve to get work done. Less current less heat and faster charging are also benefits.
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That 12HP ran a PTO for things like a mower deck and provided traction power. He is not running implements, so the gas equivalent is no more than my 3HP minibike was to move rider and tractor.
Now add in the rolling resistance of a roller and his harrows and he's at around 5-6HP GAS engined.
Now add in the rolling resistance of a roller and his harrows and he's at around 5-6HP GAS engined.
What your kW requirement is depends on force x distance at speed, i.e. if you are pulling a scraper or some implement then the force is much higher than a trailer full of dirt. Choose your motor power and the cooling/duty cycle based on your worst case load and desired speed requirement. Combine with desired operating time at that load gives battery capacity required. Volts and Amps are the same as torque and rpm, and also force x speed, once you have added in efficiency of each energy conversion and assuming you aren't going up and down hills. Time converts from power to energy and therefore gives run time from the amount of work available in the battery. Spreadsheet time
One of the simplest ways of working out energy use is to monitor gas consumption, if that is an option still.
Lets say you settle on a 5kW electrical power brushed series forklift motor, you'll be rejecting about 1kW of heat under full load, enough to heat a bedroom comfortably in mild winter. Spending a hundred times that on an more modern AC motor you'll need to reject 300-400W. Choose your cooling based on your expectations of run time vs cooling time vs average load vs budget. Engineering
One of the simplest ways of working out energy use is to monitor gas consumption, if that is an option still.
Lets say you settle on a 5kW electrical power brushed series forklift motor, you'll be rejecting about 1kW of heat under full load, enough to heat a bedroom comfortably in mild winter. Spending a hundred times that on an more modern AC motor you'll need to reject 300-400W. Choose your cooling based on your expectations of run time vs cooling time vs average load vs budget. Engineering
Using which efficiency numbers ?
10% seems pessimistic to me, although it might be a reasonable approximation. Specific fuel consumption (amount of fuel consumed per unit of shaft energy produced) is readily available for many engines. I couldn't find a BSFC chart for any small engine in a quick seach, but some list consumption at rated power, such as a Honda GX160 consuming 1.4 L/h at 3,600rpm to produce 2.9 kW - that's about 0.5 L/kWh (or 0.5 L/h or 0.13 US gal/h per kW of output). In mass terms, it's roughly 360 g/kWh or about 23%. Consumption will be better at lower speed and full load, and worse at part load.
yup, just a rule of thumb, average eff at optimum load won't be equal to total eff etc. A five minute google comes up with this graph
Yes, but running at half power in the cases shown in that graph only lose about 25% of peak efficiency... getting down to 10% means starting really low. That paper studies some very low compression ratios in a research engine, with the point being to compare compression ratios and fuels, rather than to represent typical commercially available engines.
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What do you need RPM for?
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