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Discussion Starter #1
hello all. apologies for the long post, I hope some have the patience to hear me out and offer ideas.

My name is Reid Allaway, I’m an organic vegetable farmer and tinkerer in les Cèdres Quebec, west of Montreal, and I’ve just joined DIY Electric Car to seek assistance with some new EV projects for our farm.

I’ve had only a few months experience with EVs since being infected with the bug by forum member Yabert who is a kindred spirit and great guy who helped me rebuild Bob, an old Taylor Dunn utility cart who is now in constant use for a multitude of tasks on our farm.

Success with Bob and the realization that the era of lead batteries is well and truly over has lit a figurative fire under my backside to do more of this wonderful work so I’m currently planning at least 3 conversions. This post is about converting my Toro Z500 commercial zero-turn mower to full electric.

I’ve read all the other posts here at DIY-EC pertaining to zero-turn mowers and I’ve learned a lot but I also think this is a different enough project to merit a new thread. My goal is to convert a large (550kg) commercial mower with 60" deck to a truly fantastic electric mower. Think "half as good as the $40K Green Machine on 1/10th the budget". At least I already own the mower :). And I de-ICED it last weekend. Anyone wanna buy a 20hp Kohler twin ICE?:D

Attached image is stock photos of Z500 machine factory config. Mine is much dirtier but also lighter and more svelte without engine, fuel tanks or hydraulic components. Of course it doesn't presently do anything but that will change.

So far the basic design of my mower conversion is governed by the following requirements - please disabuse me of any ideas that are wrong or concepts that are misunderstood:
• I want to abolish all hydraulic components and drive the wheels and mower with 3 separate motors
• each drive wheel (rears for this mower) requires independent control with perfectly fluid contactorless reversing (so sepex or PM motors only if I’ve understood correctly).
• drive wheels probably need only 1-2 kW apiece based on original config of 20hp engine + hydraulic effy losses + mower eating 3/4 or more of the power demand.
• a separate motor and controller, or perhaps simply a contactor, will be required to run the mower deck. Mower motor is probably 5-10kW, maybe even larger, and should be compound or shunt-wound if I want to belt-drive the unmodified deck.
• I want to keep the deck as-is and not mount individual motors for each blade because the existing spindles are super beefy commercial-grade units so I can’t imagine putting whimpy chinese PM motors in their stead and hoping for the best.
• my final product needs to be as easy to operate as original gas-powered version (easier if possible) so that farm employees who don't know !#$?-all about electric whatever can operate it safely and easily without doing the machine any harm.

So far I have two ideas in mind for the drive setup and I want input and suggestions. As for the mower motor I’m eager for ideas on where to source a used 5-10kW motor that can be used for a belt-drive application and which doesn’t weigh more than 150lbs.

My battery setup is flexible. I have a complete first gen Chevy Volt battery cut up in blocks waiting for this and other projects and I can allocate up to 4 of the 12S(48V 2kW) modules to this project. Hopefully that’ll give me an hour or more of mowing time?

DRIVE OPTION 1. twin sepex drives
Much of what I’ve learned about EVs, and especially sepex motors and controllers, comes from a very nice Crown electric pallet truck (jigger) which I bought at auction and fixed up. I love the fluidity of the drive and the way the sepex controller manages plug braking and super fluid transitions from forward to reverse. It can also move 2000kg with easy using a 1.6kW motor from AMD. There’s a nicely engineered oil-bath reduction gear unit, a Zapi SEM-zero controller and all the pots and whatsits to make a perfect drive system for one rear wheel. So if I can find a matched pair of identical pallet jiggers with Sepex motors going for less than $400 each I’m going to go that route. Of course, matched pairs of electric pallet jiggers aren’t something you find every day.

What’s wrong with this approach if I get lucky enough to find my donor machines?
24V is the only flaw I can see. Mower motor might want to be higher voltage to reduce wire gauges and resistance losses.

DRIVE OPTION 2. industrial PM motors and worm gear reducers
My second drive option is to use a pair of PM motors (either 90V industrial-type as I’ve already got a matched pair of 1hp) or maybe a pair of 2hp 24VDC motors that I’ve found on Kijiji if that pans out. I’ve been thinking of running them through a worm gear reducer for final drive and possibly mounting that reducer straight onto a bearing-supported stub axle to drive each hub. Using this approach the motors are easy to come by but I’ll have a hard time finding matched gear reducers used so I might have to spend money there and possibly pay more to get Al gearboxes with hollow output to save space in mounting.

If I go with PM motors will I have enough torque, even when multiplied through a worm gear reducer? My math and a quick verification with a torque wrench suggests that 50 lb-ft of torque will move the machine from a stop on flat ground and that 100 to 150 should be adequate for slopes but maybe I’m wrong. I don’t want to spend time and money on a drive system that won’t haul this 1200+ lb beast up a slight incline. I have NO big hills but I don’t want to put $1000 or more into whimp-ass drive setup.

I can assemble a 96-volt battery for the 90V industrial motors but then it’s callenging finding a controller. Roboteq seems to have an appropriate 2 channel controller though it’s far from free. At least I'd only have to buy one. Anybody used a robotics-oriented controller before? I like reading manuals at least:)

I don’t know much about PM motors, their torque at low RPM, and their capacity to tolerate plug braking and contactorless reversing control. Please advise.

I know that the worm-gear reducers will sap some energy and generate some heat and also spin to an immobilized halt almost immediately but I don’t think these are show-stoppers for a zero-turn mower. You never coast with a mower like this anyway, it’s always under power or braking or stopped. No need for a parking brake :)

Thanks to any and all who have the patience to read through and offer any insights.

~ reid
 

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Discussion Starter #2 (Edited)
progress - sepex motors found

I seem to have gotten lucky in a local industrial auction and when I picked up my loot today I was happy to discover that I now own five motors from Advanced Motors & Drives, all identical :), each with a flaw :(. Luckily most flaws are moderate and I'm pretty sure I can rebuild 2 or 3 of them by combining parts. In fact I got one done this evening. Of course I don't have a spare sepex controller sitting around for testing. Does anyone know a clever trick for testing a sepex motor? I presume I don't want to run the field in series as the windings are much smaller gauge but should I do so briefly at 12V to test that a motor spins up or wait until I can use a controller?

oldest is XP 3656? (hard to read nameplate) from yr 2000 by date code
the other 4 are all model DD0-4002. Three from 2005 and one from 2012 - with a broken shaft:mad:

I'm optimistic that these 6.7" motors will provide adequate power for my two "wheel drive" units. AM&D suggests that 6.7" motors go up to 7kW at 96V and 5000 rpm. Can I hope for 3.5kW at 48V? I think I need about 2 or 3 kW per wheel.

Now I need to figure out gear reducers for them. I'm still leaning towards worm gear reducers but someone please let me know if that's crazy.

Any suggestions for what controller to use for 48V sepex control. I want fluid contactorless reversing with plug-braking and I have to buy two identical so cheaper is better. Kelly? Curtis? Zapi? that other one I can't remember? Any two-channel controllers out there that could suit my needs?

All ideas are most welcome.
 

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Discussion Starter #3
Sleep is such a great tool.

"clever trick" for testing sepex motors without a controller? Duh... It's a variant of a shunt-wound configuration isn't it? Shunt the field maybe?

Glad I went to sleep before testing with the field winding in series.

~ reid
 

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Discussion Starter #4
4 of 5 motors work fine with field winding wired as shunt.
1 of 5 has already been cannibalized to rebuild the one with broken output shaft.

Looking good. Still need help on:
- choosing Sepex controller. anyone used a Kelly KDZ? any 2-channel options?
- choosing and mounting gear reducers for drive wheels
- locating a used compound wound or PM motor for mower deck. Need about 10 to 15kW.
 

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Why worm gears? They can do a lot of speed reduction in one step, but they're not efficient compared to spur gears.

I'm no controller expert, and I'm sure that this has been addressed in the other zero-turn discussions mentioned, but the operator needs speed control to steer, not the usual torque control; that is, if I'm running the thing and I hold both levers forward the same amount (or whatever control action is equivalent in the scheme you choose), I need it to run both wheels at the same speed (not apply the same torque to both, as would be expected with the controller configuration of a typical car).
 

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Re: progress - sepex motors found

Can I hope for 3.5kW at 48V? I think I need about 2 or 3 kW per wheel.
That is a nice little cache there. Yah you should be in the ballpark if that 7kw figure is right. Make sure they are neutrally timed so you can reverse them.

Worm gear is probably fine for a lawn mower fwiw, cheap and very torquey (make sure they can reverse too) I don't know about ratios or what top speed you are looking for. I would look at lithium batteries all the same (salvage leaf/chevy volt/etc), don't mess with lead acid.
 

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Only problem that I know of with worm drive is that they tend to shear the teeth when the output shaft suddenly stops, like hitting a rock with the mower blade, ratios are really high, generally more than 20:1 so you need some monster motor rpm to get decent blade rpm.
 

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when the output shaft suddenly stops, like hitting a rock with the mower blade,
fwiw, I think this is for the drive wheels, on grass and stuff. There's a few different meshes as well, presumably trading friction for durability.

so, lets say (complete swag) 6" radius tires, 20:1, 2500 rpm (48v), that is about 9mph top speed, possibly more with field control.
 

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Only problem that I know of with worm drive is that they tend to shear the teeth when the output shaft suddenly stops, like hitting a rock with the mower blade, ratios are really high, generally more than 20:1 so you need some monster motor rpm to get decent blade rpm.
As already mentioned, the worm drives are for the wheels, not the blades; see the first post. It is true that they don't coast, but I assume that would be handled by the controls (limiting the rate of speed change), as it presumably is in a power wheelchair... a common place to find worm gear drives.

This aspect of speed control is essentially the same for worm gear drives as it is for hydrostatic motors - you really don't want anything that allows an instantaneous drop to zero speed except as an emergency stop.


The blades do need brakes, presumably the same ones which are probably already part of the belt drive which is being retained, although the belt drive clutch is no longer needed. Whatever control is used to turn the mower on and off should both release the brakes and close the contactor for mower power, and vice versa.
 

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There's a few different meshes as well, presumably trading friction for durability.
I believe that the tradeoff is between manufacturing cost (lowest for non-enveloping), and all of the positive attributes (strength, durability, efficiency) which are better with single-enveloping and best with double-enveloping.
 

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I believe that the tradeoff is between manufacturing cost (lowest for non-enveloping), and all of the positive attributes (strength, durability, efficiency) which are better with single-enveloping and best with double-enveloping.
I don't think he is going into the EV mower production business, but rather salvaging surplus, so manufacturing cost isn't gonna be all that relevant. I bring it up in case he is worried about stripping teeth and wants to take a look inside whatever he brings home. If I opened up my $20 worm gears and found double-enveloping I wouldn't be too worried. If I found neither enveloping, I would be more worried. If I found brass gears I wouldn't know what to think.

I would use input and output shaft size as something of a rough guide for torque capability in lieu of definitive data as well (the input should at least be the motor shaft diameter, and the output should be able to handle i.e. 20x the motor shaft torque).

edit: after perusing surplus center, and looking at costs and weights and rpm limitations and other complications with right angle drives,
http://www.surpluscenter.com/Gear-Reducers/Right-Angle-Gear-Reducers/Cast-Iron-Shaft-Input-Gear-Reducers/?page_no=1&page_length=9999

I'm gonna guess V1 will be chain drive :) Maybe with some nice hand made covers. Pretty sure 20:1 isn't required, but extra cooling air might be. There may already be gearing on the thing that can be reused.
 

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I don't think he is going into the EV mower production business, but rather salvaging surplus, so manufacturing cost isn't gonna be all that relevant. I bring it up in case he is worried about stripping teeth and wants to take a look inside whatever he brings home. If I opened up my $20 worm gears and found double-enveloping I wouldn't be too worried. If I found neither enveloping, I would be more worried. If I found brass gears I wouldn't know what to think.
Sure, that all makes sense. It means that if given a choice of boxes to salvage, he should prefer ones with double-enveloping gears, and should expect to find crappy (less reliable, less durable, higher drag) non-enveloping gears in the cheapest (because they cost the least to make ;)) boxes.

My point was just that there seems to be no technical reason (such as friction) to choose the cheaper non-enveloping style.

Softer materials are normally used on the wheel than the worm, so while the worm should likely be steel, the wheel might reasonably be bronze or brass. These things slide on the contact face much more than other forms of gearing, so lubrication issues and corresponding material choices are not the same as a common spur gear. I don't know what to set as a minimum standard, either. :confused:
 

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if you throw more money at it hoping it will be double enveloped... better to get a couple cheap ones and see how they are put together since who the hell knows. But I predict chain (or existing) drive anyway, since right angle is a can of worms.
 

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Discussion Starter #17 (Edited)
but the operator needs speed control to steer, not the usual torque control; that is, if I'm running the thing and I hold both levers forward the same amount (or whatever control action is equivalent in the scheme you choose), I need it to run both wheels at the same speed (not apply the same torque to both,
That's an intersting point about constant torque vs. constant speed control. I'd be inclined to build it and see how much it matters. Inefficient worm reductions might just make it a moot point? I guess I should at least consider the possible need to fit transducers/tachs as I'm designing the drive setup. Thanks for the heads-up Brian.

Yes the worms are for drive only. Mower is to be driven by separate motor (still unknown what precisely). I hadn't planned to brake the mower drive it as there was never any provision in original design nor did I find it lacking in operation.

Yeah I had ruled out anything from wheelchairs on account of weight and power disparity.

I actually like right angle for this build if I can find appropriate wormy boxes. The right angle config seems like it would fit nicely in the space available. I'll take some photos of the de-ICEd hull. I do actually need 20:1 or higher and don't have any experience building multi-step chain drives so the appeal of the worm remains intact. Torque arm type reducers, which I assume are spur gear, could also work if I could find a suitable pair used. Yes I also checked surpluscenter.com and realized there's a budget question here.

I'll let you know if I find anything worth debating :)
 

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Discussion Starter #18
motor options for belt-drivie to mower blades

One option I spotted for the mower motor, assuming I have to go with new instead of used, is a Motenergy ME1004. This is a PM motor with 16 brushes and capable of 200A continuous at 48V, 400A peak for 30s. I'm sure some of you have experience with this or whatever it's a copy of (Etek or some such)

What do people think about using a motor like this to spin three 21" blades through grass. Is there too much risk of overheating and damaging the motor? I have a hard time imagining a 30lb motor can actually do this.

Can you all help me better understant my mower motor options?

•I take it I can't use a series wound motor because of the belt drive and potential of no-load self-destruction. fair enough:eek:
•I gather a compound wound motor in the 10 to 15kW size would be suitable but is a rare thing to locate.:confused:
•I don't think a sepex motor of appropriate power is likely to fall in my lap and I don't need a controller for the mower motor otherwise so sepex doesn't seem like best fit:mad:
•Is a big shunt-wound motor an option? where would I find one?:(
•I believe that a PM motor might be an appropriate solution and some options exist for new motors of this sort. Not so much available in used unless I'm mistaken:confused:
 

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Discussion Starter #19
another gear reducer option

I found another option for gear reducers. 29lbs each but inline 2-stage helical gear reducers instead of worm. Ratio isn't as low as I'd like but I can limit top end in controller I guess. Here are a couple pics. Local industrial surplus business has several, asking $200 each. Specs sound promising. I'll have to go see about fitting them in the physically available space and complexity of mating to the motors.

Any reason to steer clear of helical gear reducers?

I'm really not sure there will be space to fit this configuration.

~ reid
 

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Re: motor options for belt-drivie to mower blades

...

What do people think about using a motor like this to spin three 21" blades through grass. Is there too much risk of overheating and damaging the motor? I have a hard time imagining a 30lb motor can actually do this.

Can you all help me better understant my mower motor options?
...


Here's a 3-blade deck I helped a friend electrify. Best electric multiple blade deck I've ever seen. Uses a 7.2" dia compound wound motor basically a forklift hoist pump motor. Some large floor cleaning machines also used motors like that.

IMO, the blade takes the bulk of the power from your ICE riding mower unless you have some steep hills. If your mower was powered by a 25hp ICE, I'd look to use a couple hp for propulsion and like a 10 hp electric motor with peak capability of 25-30 hp (for at least a couple of minutes). That PM brushed motor could be a problem. Maybe use two of them.

And on the propulsion, elimination of the hydraulics sounds nice, but for all the trouble, mechanical and control-wise, I'd just drive the existing pump(s) with a single motor. Here something like that PM might do.

Regards,

major
 
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