# New zero-turn mower project - no hydrostats



## Reid_in_QC (Sep 5, 2017)

*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

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.


----------



## Reid_in_QC (Sep 5, 2017)

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


----------



## Reid_in_QC (Sep 5, 2017)

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.


----------



## brian_ (Feb 7, 2017)

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).


----------



## dcb (Dec 5, 2009)

*Re: progress - sepex motors found*



Reid_in_QC said:


> 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.


----------



## piotrsko (Dec 9, 2007)

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.


----------



## dcb (Dec 5, 2009)

piotrsko said:


> 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.


----------



## brian_ (Feb 7, 2017)

piotrsko said:


> 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.


----------



## dcb (Dec 5, 2009)

brian_ said:


> The blades do need brakes


Nah. 


Edit: if your controller HAPPENS to have regen, then might as well use it, but I wouldn't go out of my way on a diy.


----------



## brian_ (Feb 7, 2017)

dcb said:


> 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.


----------



## dcb (Dec 5, 2009)

brian_ said:


> 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-R...put-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.


----------



## brian_ (Feb 7, 2017)

dcb said:


> 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.


----------



## dcb (Dec 5, 2009)

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.


----------



## Ivansgarage (Sep 3, 2011)

Check out right angle drives for wheelchairs would be perfect for lawn mower applications.

--


----------



## brian_ (Feb 7, 2017)

Ivansgarage said:


> Check out right angle drives for wheelchairs would be perfect for lawn mower applications.


For a smaller mower, perhaps, but this is not a small mower:


Reid_in_QC said:


> ...
> My goal is to convert a large (550kg) commercial mower with 60" deck...


----------



## Reid_in_QC (Sep 5, 2017)

> 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


----------



## Reid_in_QC (Sep 5, 2017)

*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
•I gather a compound wound motor in the 10 to 15kW size would be suitable but is a rare thing to locate.
•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
•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


----------



## Reid_in_QC (Sep 5, 2017)

*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


----------



## major (Apr 4, 2008)

*Re: motor options for belt-drivie to mower blades*



Reid_in_QC said:


> ...
> 
> 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.
> 
> ...












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


----------



## Reid_in_QC (Sep 5, 2017)

Thanks for the insights Major. I was hoping to get your opinion on motors for the mower deck. I had seen yours and it was part of what encouraged me to go ahead with a big mower build.

As for keeping the hydrostatic drive setup it's not even up for debate as I've got problems with one pump and I've already stripped it and won't go back. The challenge of the drive setup is part of what I like about this project.  That smiley strikes me as the proberbial sh*t-eating grin. Let's hope I don't end up eating too much to prove my point.

Yes original ICE was 20hp so I'm aiming for 2kW per wheel and 10 to 15kW for the mower.

Can you comment on my list of motor criteria and correct any misunderstandings



> •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
> •I gather a compound wound motor in the 10 to 15kW size would be suitable but is a rare thing to locate.
> •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 unless I can't find another solution. Are 15kW Sepex motors available?
> •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


----------



## major (Apr 4, 2008)

Mower blade load is like a fan load. Actually good use for series wound motor. Broken belt over speed... How about microswitch on belt tensioner where it opens contactor powering motor? Can even use FWD to limit contact arc. Also series motors are best for contactor starting, less arcing on inrush.

You could rewind 2 of the 4 series field coils to shunt and convert to compound.

SepEx, shunt and PM all arc on full voltage starts. They all suffer armature reaction on inrush meaning low torque and longer accel time with comm/brush arcing. They tend to field weaken as they heat meaning increased current. I typically badmouth PMDC for blades due to thermal issues. Magnets typically are good insulators keeping heat in the armature. 

Regards,

major


----------



## Reid_in_QC (Sep 5, 2017)

major said:


> Mower blade load is like a fan load. Actually good use for series wound motor. Broken belt over speed... How about microswitch on belt tensioner where it opens contactor powering motor? Can even use FWD to limit contact arc. Also series motors are best for contactor starting, less arcing on inrush.
> 
> You could rewind 2 of the 4 series field coils to shunt and convert to compound.


great ideas. Microswitch on tensioner seems a simple solution to allow use of series-wound motor. That lets me focus on other challenges rather than having to spending ages finding an exceedingly rare motor.

many thanks.


----------



## dain254 (Oct 8, 2015)

I have contemplated building an electric mower, among most other things imaginable - what I concluded is that while eliminating the hydrostat increases the efficiency a bit, I believe a person would simply get overwhelmed with having 3 separate motors and motor controllers required to do a zero turn. My recommendation is simply replace that V-Twin with a single somewhat powerful 15-20kw continuous rated motor and spend the rest you would have spent on the extra controls/nightmares on increasing your battery capacity! The reason hydrostat works so great is it allows the engine to run your blades constant while varying the drive in a somewhat efficient manor. 10kwh worth of Chevy Volt cells would probably yield somewhere around 2 hrs of mowing w a 60" deck, but since I don't know the EXACT duty cycle of the mower engine it is just a guess!


----------



## Reid_in_QC (Sep 5, 2017)

Valid critiques Dain and thanks for the power estimates.

I'm afraid I'm in it for the fun and the challenge of a multi motor setup more than from a practical perspective. For a straightforward electric mower conversion this is not the way to go nor the machine to start with but I'm inclined to disregard practicality for this project. My goal is to learn a lot about EV design, motor and controller configuration, and possibly build a great mower in the process. I do have some simpler more practical projects in the pipe but somehow I'm less excited about them, and I need less help with them, so it'll take a few more late nights before I get them posted for feedback.

I swear I have pragmatic moral fibre at my core. It's just not being employed much in this project. 

~ reid


----------



## Reid_in_QC (Sep 5, 2017)

Making progress on sourcing parts for this project but still no luck finding an affordable matched pair of worm gear or other gear reducer. I did have the pleasure of learning about cycloidal gear reducer in repairing one from a lift steering motor - those are so cool! but the space in the mower chassis is such that the right angle configuration of worm drives seems really desirable.

So far I've got:
• my drive motors (2x AMD DD0-4002)
• drive controllers (2x Curtis 1244)
• a candidate mower motor (8" forklift pump motor, series. Remains to be seen how I can manage the female shaft puzzle)
• Volt batteries (hopefully 3 x 2kWh 12S modules is enough)
• a bunch of little stuff: contactors, pots, switches, etc.

That's it for now. Got a bit distracted with another project but trying to keep some momentum by updating here.

Today's question for you all: Do motor rebuild shops commonly press out and replace armature shafts or is that just a crazy Jim Husted trick I read about somewhere here? I know I should just call local rebuilders and ask them but here I am typing...

~ reid


----------



## major (Apr 4, 2008)

Motor shops may be accustomed to shaft replacement on larger motors and generators, but unlikely for the size used in fork trucks. To my knowledge fork motors were/are not designed with the required spacer behind the comm which facilitates pressing a shaft out and in without distortion of the armature windings. Jim did it often by boring the original shaft from the center of the comm. Then he used a mean loose fit on the new shaft/comm. I doubt he ever made a cent on those jobs.

And I doubt you want to really use worm gears as they don't back drive. That would tear up your lawn terribly. Use spiral bevel (ring and pinion) or even straight bevel gears for right angled drives.

major


----------



## dh1 (Dec 21, 2015)

Great project and I could be wrong here but 
I think the drive motor you want to use are Series Wound and they will not hold there rpm as the load changes. The rpms change too much as the load on them changes.
Not sure what is the best type of motor to use but you want one that holds it's rpm, or try's to, as the load, (hills, grade, soft spots in the lawn) so you are not constantly correcting so much.

2 drive motors, 2 controllers, 1 for each wheel would work just like the original Hydro would as far as motion control.


----------

