Scooburban

[migraineman]

Restoration fundamentalists be forewarned ... here there be dragons.

I am in the process of converting a 1967 Sears Suburban over to electric drive using readily available scooter parts. Yes, this frankentractor shall be known as the Scooburban. The donor tractor is missing it's engine and was about to be sent to the recycle heap. The steering, frame, and transaxle are all in good working order. I purchased a Currie Technologies scooter motor (600W), 40A speed controller, and twist-grip throttle. The intended uses of this vehicle are:
- allow the wife to haul mulch, dirt, plants, etc without being intimidated by the gas tractors
- haul the kids around the neighborhood at Halloween
- supplement the gas tractors for the upcoming GarageMajal build
- build an EV (something I've wanted to do for years)

The first order of business was to drop the transaxle (yes, I had a little help.)



There's plenty of space under the frame ahead of the transaxle, so I'm fabbing a bracket that mounts directly to the transaxle case. The drive section will be mounted as a unit.













I ran out of daylight today, but you get the general idea. The motor will mount on a plate with slots to allow the belt to be tensioned. I plan to use Group 24 or 27 marine deep cycle flooded batteries. With no pesky motor to get in the way, they should mount up front without issue. The brake starter-interlock switch will be tied into the speed controller's brake switch input. More details as I invent 'em.

A note about the hunk-of-unistrut-bracket - the trans case has draft on the sides. Two 5/16-18 nuts were match-welded to the bracket such that the inner edge of the unistrut contacts the case. The outer edge was shimmed such that the forward face of the bracket is perpendicular to the transmission input pulley. This relationship is easily verified with a large framing square placed across the face of the input pulley. The assembly was fussy to align, but it bolts up really nicely.

[jeepersmitty]

Looking good.It is always nice to have help. Keep us updated as you go along.

[walter g]

Looking foward to this build.Looks like a neat project.

[Jim_WV]

Quite an unusal project for sure, looks great so far, keep us informed and for sharing .

[david doyle]

Great project. Can you tell us about what you expect in terms of Battery needs etc. Love to learn more about it. a silent run around tractor would be be great!

[Titanium]

I'd be interested in the cost of materials, if it's not too nosy to ask.

I've been thinking about repowering an oldie, for my youngin to play with.

I hadn't considered going electric!

Bravo!

[Justin]

To add to all the other questions, how much power will that little motor provide? I know its 600 watts, but what does that equate to? How many batteries do you plan on using. Looks really cool, looking forward to future posts.

[Big10]

[migraineman]

Please ask questions ... I don't mind. I'm making this up as I go along, so having an opportunity to discuss things is highly desirable. I'm assuming you have the necessary tools for a job like this, so I'm not including them in the "costs" section.

Costs -
- Donor tractor $50
- 600W electric motor $28 from All Electronics (unfortunately, sold out)
- 40A 24V speed control $33 from All Electronics
- 24V twist grip throttle $13 from All Electronics
- 2x Group 24 marine deep cycle battery ~$70 ea. (Sears, WalMart, etc)
- 10ft. Unistrut $18 from Home Depot (near the conduit in the electrical dept.)
- Anderson Power Pole connectors and crimper from Powerwerx.com, not expensive
- 50A battery disconnect switch $5 from Harbor Freight
- in-line fuse socket with 40A fuse, not expensive
- 2" drive pulley $6 from the local TSC
- brass tube from the junk bin

Need to buy -
- 24V battery charger
- more Anderson Power Pole connectors
- 8AWG stranded wire
- ring lugs (I already have an appropriate crimp tool)
- 1/2" drive belt (need to finish the bracketry to determine size)
- battery mount hardware

Performance -
I expect the motor to draw about 25A average. Group 24 batteries have a typical Reserve Capacity (RC) of about 100 minutes. RC is measured at a draw of 25A, so I expect about 100 minutes of operating time (decreasing as the batteries age.) This particular motor is rated for 600W output. With a 24V 36A input (that's what the label says) of 864W, the motor's efficiency is about 70%. Not stellar, but not horrible either. At the full 36A current, the batteries should be depleted in about 60 minutes. Moving up to a Group 27 battery would increase the RC rating from 100 minutes to about 150 minutes.

The motor turns at a little over 2600 rpm. The Tecumseh that powered this beast originally was set for 3600 RPM. I'm running a slightly undersized drive pulley, so I don't expect top speed to be the same. I'm not looking for that, but swapping in a larger drive pulley to match the belt rate isn't out of the question (but I don't think the 600W motor will pull as hard as the 12hp Tec mill.) The brass tube stock brings the motor's drive shaft up to 1/2", at which point I can swap in other pulleys in the future. I'm designing the tension mechanism to account for a future swap opportunity.

[migraineman]

Oh, a final comment on why I've chosen what I did. Scooter parts are readily available ... in fact there's a "donor" scooter in the garage with dead batteries. Being mass manufactured consumer goods, the prices are quite reasonable. Most are 24V, though the bigger ones use 36V electrics. At some point I plan to put a sinewave inverter on the Scooburban to supply electricity far from the house. Inverters expect 12V, 24V and 48V inputs. 36V doesn't line up with the long term plans.

Similarly, if I want to step up to a larger electric motor, I can get one as a replacement part for a Black and Decker CMM1000 or CMM1200 (which I also own, and have recently dissected.) This particular motor is available from DeWalt service for about $150. It too is 24V based, and claims 5hp equivalency. I also found another 24V motor from the American Lawn Mower Company for $77 - part number 3610139 that's part of the Earthwise 60020GT 24V electric mower. For any of the upgraded motors, I'd need to move to heavier wiring and a beefier speed controller, but the batteries would translate directly.

Finally, 1hp is roughly 750W. The 600W motor should be equivalent to 8/10hp. Applied properly, that should be quite useful. Consider that farmers used to pull a small plow behind a single mule or horse. A horse trots in the 10mph range. Honestly, I'm eager to see what I can do with "about 1hp."

[Titanium]

Weren't some of the old hit and miss engines under 1 HP?
They did a lot of work!

The mower pictured in my avatar, is about 1.75 HP at top rpm.
But, you wouldn't want to get your toes under it! Ha Ha

[Tractor-Holic]

Put a starter motor in it,and hang on!... I saw a video of a mini-bike some car techs mounted a ford starter on,direct chain drive to the rear sprocket,and they only had a solenoid and an on off switch--the driver has to just about sit on the handlebars when he hits the switch,otherwise it'll just about flip over backwards!..it only had one battery too!..

With the low gearing a Suburban has,it doesn't take much HP to get one moving..I put a 7 HP Briggs on a SS-12,and I hardly feel any difference in power,as far as pulling goes--probably wouldn't mow that great though..

[david doyle]

Thanks alot for the info. I have an 12.5/38 MTD without a motor which might be just perfect for this type of project and you have done 90% of the leg work already!
Please post your updates here (time permitting) really enjoy seeing smart people do smart things

[migraineman]

We'll see. I'm not above doing stupid things.

I've seen a couple of MTD electric conversions that involve putting a motor in place of the IC vertical shaft engine. Belts to the transaxle and deck are run as stock. Battery placement is an issue, mostly because the motor is sitting in the best place for batteries. I haven't seen anyone hang the electric motor directly off the transaxle, but I don't see why that would be an issue. I actually considered getting an MTD tractor for this effort, simply because all the modern machines are manufactured by MTD ... mostly. I do, however, have a soft spot for the older machines. This Suburban was acquired on a trip to purchase a 3-point hitch for the SS12. Not what I intended, but I learned long ago to seize the opportunities when they are presented. (and yes, I caught hell from the wife for bringing *another* broken tractor home.)

[Titanium]

Originally Posted by migraineman

(and yes, I caught hell from the wife for bringing *another* broken tractor home.)

Wiat until you've got it all fixed up and running well. She'll be happy using it!