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Discussion Starter #1
hi all I am new to this site been reading up on how to work on a snapper.
I am building a e,ec mower out of a few of them
it comeing along good dose any one know wath years they made a comet 11 ?
my has no s/n
if you want to see what i building goto
http://disgusta.com/pgreen_cut.htm
 

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Hello Dale,
You've started a project many others might track if they knew what you're doing. While this is a Snapper forum, I'm not confident that the most interested target audience will discover your projects existence here.

A few comments. I strongly urge you to add a pulse-type battery-desulfator circuit to your battery bank. Service life of your batteries and their actively-available charge capacity will be greatly enhanced by that addition.

Your Comet's operator seat does not appear to be correctly oriented while supporting your operator's weight. It should not be tilting downward toward the front. In fact, the seat bottom should tilt slightly rearward.

You didn't explain which wheels will be driving. I assume that only the front wheel pair of the rear double axles will be pushing. Is that correct?

Comet operator descriptions have often included favorable comments about how sharply the stock-design is able to turn. Operators can execute EXTREMELY sharp turns by locking the rear wheel brake which enables roughly Zero Turning Radius turns. Your extended rear with the second non-steering wheels will be heavily loaded by your storage batteries. I expect that the turning radius of your proposed design will be miserably wide and cause accelerated tire-wear due to extreme tire scrubbing during every turn. Your design changes eliminated one of Comet's most endearing features, which is its excellent turning radius.

I also have strong reservations about required horsepower output from your electric motor and its duty-cycle. Mowing tends to require longer duty cycle periods than many people expect. Rejecting heat quickly becomes a duty-cycle period limiting factor for electric motors which have low efficiency and high output demand. I doubt that your used golf cart DC electric motor's efficiency is better than 80%. If that expectation is true, and your combined mowing plus wheel-driving load only requires 5 horsepower, your motor must reject 20% of 5 horsepower = 1 horsepower as waste heat. The conversion of one horsepower as waste heat can be expressed as 745.7 watts, Trying to reject about 75% of a kilowatt as waste from a motor that size would take some serious cooling efforts. But if the motor also drives a fast-spinning fan, it might not become self-destructively hot. Pushing a golf cart is a MUCH smaller load than trying to drive a rotary mower's blade. What blade side do you hope to spin?

Peak loads caused by rotary blades are better predicted by swept area under the blade(s) rather than total cutting width. One possible explanation for that is that blade strikes occur repeatedly rather than only at the blade's swath leading edge.

General Electric produced the Elec-Trac, a storage battery powered tractor with front mounted mower attachment during the 1960s and 1970s. You might learn from how they approached design decisions. You are creating a new design.

Good luck.
John
 

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More thoughts about your Comet II electric conversion project.

For the moment, I'll "assume away" your project's battery-bank usable capacity and electric motor steady-state power capacity and duty-cycle limits.

If those issues are resolved, I think you should return to Comet II's original excellent design. I see from your photos that your salvage purchased Comets included one with the older narrow rear wheels & tires and one with the later wider wheels and tires. Factory suggested air pressure for those rear tires was 20 psi according to some sources. All tire makers include some reserve capacity. A Goodyear tire engineer with whom I worked on a project about 30 years ago said that running 20% higher pressure is always within working capacity even though it would relieve Goodyear of any liability for failures which might occur at higher than "rated" pressure. I believe that you can use your wider tires well within their functional load limits to support your 3-golf-cart flooded-type batteries.

The design feature which limits how far forward those batteries can be mounted is the seat back. First work out your seat mount problems so it will comfortably support your 79-year-old driver (classy lady - we like her spirit), with the seat bottom tilted slightly rearward. That seated position is much less fatiguing than the current foward-tilting orientation. That will reveal to you how much rear deck room you can use for battery storage behind the seat.

The battery support deck can extend out to each side over your large tires. I think you will have enough room back there on each side to mount two of your batteries orienting their long dimension with the mower's length. Leave enough clearance between them and the seat's travel to prevent contact between them during seat bouncing during maximum seat-suspension travel. Then mount your third battery side-to-side on that same deck behind the two side batteries.

This suggestion's objectives are to restore your Comet II's original excellent turning radius, and to restore its "back standing" service position capability. The Comet Owner's Manual suggests removing the flooded battery (for those with electric start) then lifting the front and standing the mower on it's rear supports to gain bottom access for service work. What a beautifully simple way to access blade sharpening with an angle grinder and other bottom-access work. Your extended rear double-rear axle configuration destroyed the best features of this mower's design. I see no reason which should prevent you from mounting your 3-battery bank 36-volt power supply on a rear deck surface. You should leave about 1 inch vertical clearance minimum between your rear tire tops and your rear deck's bottom. The reason for that clearance is that if mud ever adheres to the rear tires, they do not easily become friction locked. I'd add a mud scraper bar forward from deck to limit mud thickness that can stay attached to your tires before that tire surface passes under your deck.

Perhaps half of your clam-shell storage unit can become a sun deck? Could you support it by extensions from your mower's vertical rear support bars. High winds with high center of gravity and large sail-like top decks sound like a prescription for upset. But on calm windless days on flat terrain, sun shade while mowing would make the experience much more pleasant. I think it would appear wonderfully cool. It would not surprise me if we are told that others have supported canvas awnings over Comets by extending those strong rear support bars.

You wanted feedback Dale. I hope I haven't offended. I've been involved with many prototype building projects from which sometimes-humbling experiences I've learned that the best time to abandon bad designs is as soon as a better design path is discovered. Ego attachments to bad design have cost many talented men years of their lives.

Have you considered running a separate electric motor drive to each rear wheel? If you did that and then swapped front caster support for the front steering mechanism, you'd have converted your Comet II into a conventional ZTR with electric drive. The most common money-pit failure system within conventional ZTR mowers is their failure-prone high-pressure hydraulic systems. You might eliminate that failure-prone solution, retain flip-up bottom access capability, add a rear-support-mounted canopy and add your "Green" rechargeable battery drive system. That would arguably put you machine among the "bleeding edge" of current mower designs. Electric wheel chair joy stick controls can be adopted to enable single hand operation from a comfortably-positioned right-arm rest. That would still leave the left side open for operator entry and exit. This left-side access combined with right hand controls worked well on Toro Groundsmasters.

Good Luck and thanks for providing the pleasant "mind candy."
John
 

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Discussion Starter #4
heat on the motor is not a problem. this same motor goes into a 875 that designed to carry around 3000 lb plus its own weight of over 1000 lb
Horsepower (kW) 8.0 hp (6 kW) @ 1600 rpm
it has a Speed Controller Solid State 400 Amp Rated
and the batteries are rated at a 50 amp draw for 102 mins x 3
the longest I will sit on any mower is one hour in the ga heat it should go 2 1/2hours on a charge.
there is no way to fit these batteries and the motor / Speed Controller /and selinoid on the deck of a snapper that why i made it longer and to keep it from digging in to the ground due to the weight '
yes i know the turning will be wider how much is unknown till i get the motor in it and see. yes it will take jacking it up and putting it on a stand to work on it but i have not gone under my 12.5 gas snapper 10 times in 20 years
the seat is not in place yet it is going to move back another 4 inches so that my mother can put it in rev easier or she can leave it in 1 or 2 and hit the f&r swicth and go backward that way.
and there is noway you could flip it with 240 pounds of batteries even if i got them back on the maib deck. what i may end up doing if the exter two wheels keep it from trunning to bad is replace them with one tanded wheel in back but we going to try working with the 4 rear wheel first one thing abouth a fun homemade toy you can always go back and modify it Getting other opinions counter to what i am doing is good makes me think but I am hard headed more of a try it to see person
 

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Here's a Snapper Comet in its "service position" as described in the Owner's Manual.


I just bought a Comet from a fellow. He and his father had owned and use it for 35 years. Yet he had no idea that Comets were intended to be stood on their rear end for bottom servicing as suggested in the Owner's Manual. They had struggled by lying on ground next to the machine to gain access to its underside.

How much do each of your 12-volt batteries weigh? I've seen a small Kubota tractor with Front End Loader picking up about 600 pounds which required adding a lot of extra weight to its rear end since the front wheels were behaving like a pivot point. It's front tires were carrying the full tractor's weight as the rear tires lifted from the ground, plus the FEL weight, plus the driver's weight, plus bucket-load weight. Yet its front tires were smaller than the wider rear tire set on your Comet. They didn't APPEAR to be over stressed though they must have been operating outside their load rating. I'm confident that adding the weight of the three 12-volt batteries shown in your photos would not come close to overloading a pair of those wider rear tires. I'm familiar with Trojan T-105 6-volt golf cart batteries. I bought 16 of them for my photovoltaic system which has two 48-volt input inverters. Those Trojans each weigh 62 pounds. So to make a single series 36 volt battery pack, you'd need 6 of them which would weigh 6 x 62 = 372 pounds. I expect the 3 12-volt batteries shown in your photo weigh considerably less than that.

Examine this image showing how these tree batteries are currently loading your single rear axle.

Since their combined weight center is almost aligned with the wider rear tire's axle, almost all of their weight is currently carried on that single axle. The next axle toward the front is contributing almost no support. Yet the wider rear tires do not appear to be significantly compressed from this load.

The extra axle appears to contribute no performance advantage but does impose a huge performance liability. It also makes standing on end after battery removal impossible.

"i made it longer . . . to keep it from digging in to the ground due to the weight."

According to my notes, the earlier Comets were fitted with 4.80/4.00-8 rear tires on wheels secured by 4 lug bolts. Later Comets were fitted with 16-6.50x8" rear tires on wheels secured by 3 lug bolts.

I think you're over reacting to the relatively modest weight carrying penalty compared to the stock rear wheel/tire carrying capacity. I just found one reference to a 4-ply 16x6.50x8 tire rated to carry up to 1400 pounds per tire. That's the size of your wider tires.

I'd be interested in others' opinions about how much weight can safely be added directly over a Comet's rear axle supported by wide tires.

So far as power load distribution, I expect 85% to 90% of your power load will typically originate from spinning your cutting blade. Little power is needed to roll mowers or golf carts over level ground compared to power needed to sustain cutting blade loads. Similarly, pushing loaded a golf cart about at low speed doesn't require much power. If you want quick golf cart acceleration and hill climbing ability, that will demand many times more power.
Good Luck,
John
 

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Discussion Starter #7 (Edited)
yea it works. I dont see how he can change gears with the battey there. also my 400 amp Controller is much bigger than his Two Albright SW-80 contactors. The battery i got are bigger also plus i dont want parts to be seen or rained on.
I am going to build a smaller version also while i wait on my mounting plate and shaft about two week away i got the parts to build the other one and some plans for it.

http://disgusta.com/pgreen_cut.htm
 

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"Your extended rear with the second non-steering wheels will be heavily loaded by your storage batteries. I expect that the turning radius of your proposed design will be miserably wide and cause accelerated tire-wear due to extreme tire scrubbing during every turn."

Well I commented on this on the first forum he posted too. I expect you can take the front wheel off and it will still stand straight out. Also, IF only one set of rear wheel are driving, when on not too much of a hump or depression, it is going to "high center". IF it must be similar to this to hold all parts, seems an "articulating" configuration between the two sets of rear wheels would solve turning and high center problems.

Walt Conner
 

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Discussion Starter #9 (Edited)
After working on the deck a little more i have all the battery right behine the seat and the Controller move back I might have to add weight to the front end
We will see when it running in two or 3 weeks. I will have both setup up at the same time I plan to start on the short one tomorrow.
I get snappers for 25 bucks each and I got abouth 4 elec system from old golf cars:drunkie: in the shed and a few golf cars to boot so we can try lot of things I just like the 4 wheel look on the back who know I got a extra set of mags for a golf car maybe i see if I can put them on the short verson one I going to build
 

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Gotta love green energy conversions! I applaud you, even though I enjoy the fresh smell of raw gasoline fumes in the morning. :D
 

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Does that show up on a drug test? Maybe gas is the way to go
Not to my knowledge... Some side effects do include the sudden urge to perform burnouts in the driveway (may not be applicable to tractors).

I've been meaning to ask -- how does your battery operated snapper perform while mowing? How long can you mow until you run out of juice?
 

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Discussion Starter #14
"I've been meaning to ask -- how does your battery operated snapper perform while mowing? How long can you mow until you run out of juice?"

I dont know yet I think I will get about 2 hours on a golf car it will go about 4 hour flat land we will post when we get the mounting plate in and mow the yard
http://disgusta.com/pgreen_cut.htm
 

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Discussion Starter #15
Well rigg up a support today for the moter did not work very well but it did let me run around the yard eveyone on here was right it trun way worst then i figer it would do. We park it in back till we can think about it awhile
pick up another unit we will make a short one and work on moter plate
will post when we get stated on it maybe next weekend
it still cute hope I can figher a way to save it
 

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Dale, I applaud your energy and willingness to explore new paths which are not just minor tweaks on others previous designs. Essentially, you abandoned Snapper's design and just used their parts to create your own design. So even though its performance was disappointing, your spirit is to be celebrated.

Before you do anything to change it, how about trying Walt's speculation about floating its front end without a driver in the driver's seat. Take off the front wheels and see if the battery weight and distance behind the drive wheels is enough to generate enough upward pivoting thrust to the front end to float those front axles in the air. If it works, by all means, take some photos. Great idea Walt!

Dale, your electric drive system doesn't need a fuel tank that occupies space over the left rear wheel. It doesn't need an exhaust system that occupies space over the right rear wheel. So how about welding up two battery-support shelves, one over each drive wheel? That would mean you only need to fit one battery and the electric motor behind the driver's seat. Honestly, those original rear drive wheels can carry that extra weight without any problem.

All the best to you,
John
 

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Discussion Starter #17 (Edited)

what I am planning on doing after I build the short one is move the drive deck to the back and remove the 2nd axle keeping the batterys right behine the seat
that should fix a lot of it by keeping the car carrier I will be able to add the inverter so I can plug in the weed eater that also will store in it
it look somethig like the pic at the top
 

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You apparently have access to some Georgia bone yard where you can buy these old Snappers for $25 a pop for your trials. That's great.

But have you priced a belt long enough to run from the deck drive pulley back to your proposed extended rear drive electric motor pulley location? I think you'll find that priced higher than $25. Even then, belt stretch is best predicted by percentage of total length. The longer the belt, the more it is likely to eventually stretch. That can be corrected by an adjustable idler tensioning pulley. Remember that this deck clutch configuration functions by removing and restoring that belt's tension with an existing idler. Sizing and maintaining that extra-long belt in proper adjustment will be made more difficult by your new belt's longer length.

That's without even considering that it is a "double V" belt. You could easily chew up most of a $100 bill just getting that very special belt if you choose to go that way. But then, perhaps you feel that lessons learned during Snapper's trials which caused them to go with the more expensive "double V" belt configuration won't apply to your similar configuration.

You must love that storage pod. To save it you've elected to ignore the easy choice of mounting your inverter on a shelf above your front-electric motor and battery storage area. That would keep the mower's original short length yet include your inverter. I know that big inverters can be heavy. I think my big Trace inverters each weigh 136 pounds. Does your inverter weigh enough to importantly affect your machine's center of gravity?

By removing the original rear axle, which is your modified machine's middle axle, you will be removing the tire scrubbing, over-centering problems, and the front won't tend to float in the air as Walt wisely speculated. But it's turning radius will be so wide that mowing sharp corners will require big gentle loops or other time-consuming steering procedures like stopping, backing up while turning your steering to opposite lock, stopping again, then steering to lock opposite until you can align you new path with the new mowing path. Requiring your mother to make those efforts at every mowing corner would not a kind thing to do. How about running a steering trial that does not require moving your drive system to the back axle? Just remove the middle wheels from their axles so those axles just float in the air. Then ask a friend push you around while you steer it to see if you think you might be satisfied with that extended wheel base rear-wheel drive configuration. Or your mom can steer while you push. That way you can try the 4-wheel extended wheel base steering without buying that expensive belt and remounting your drive system to your extended back axle.

I expect that you'll prefer how your short version performs compared to your extended wheel base versions.

You said, "It (is) still cute hope I can figher (figure) a way to save it."

Agreed. It's cute.
You can save it without much difficulty. Figure out how to mount your batteries so they fit forward of the original rear end position. Mount them there. Take your gas axe and cut off that extended rear end. Then transfer the back end's rear stand onto the new rear end so you can stand it up on its back end when you want bottom access. That way you even get to use your original "double V" belt.
Good luck,
John
 

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Discussion Starter #19 (Edited)



As you can see the batterys take the whole deck even with the seat support cut off now add a 6"x4"by 10" tall speed controller and a 8 inch round motor the batterys are taller than the bottom of the seat so putting them there is out.
There are all kinds of mower and belts at the bone yard I think I can find one to work even if I have to add exter pulley to take up room

On the short version I plan to put controller under the seat one battery on front end
then build a deck out over both tires for other two batteries, box it in and install charger plug that is 4" deep thru wall. this will set 83 lb dead on front wheels I have never been concerned about tires holding the weight but the ground sinking in as i ride over it. I might have to pick up a set of the 4 lug hubs from the bone yard and add a spacer to installed golf car tire to keep from rutting the yard .may be for real need or just because I think a set of mags tire (that i have in shop) would look cool on it most likey I will build deck out of wood untill it all works then go back and build metal deck after i know what it going to look like
by the way no gas ax was or is needed it was bolted to gether useing the hold of the rear stand and two side plate. and with the added deck there would not be support for car carrier
 
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