Tractor from scrap yard finds.

Have you an battery powered lawn mower or kiddy car or anything that is not designed for the road, be it home made or bought, then this is a area for you
RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Tractor from scrap yard finds.

Postby RobSmith » Thu Aug 12, 2010 11:17 pm

Night Train wrote:Some good news and some bad news.

Good news:
I have video of me, and my Dad, driving the tractor about in first gear. second was a bit too fast and bouncy on the cobbles and there is no padding on the seat.

Me:
Image

Dad:
Image

Bad news:
While playing and falling about laughing with silly EV grins I managed to get a clunk from the transaxle. I think a tooth has broken off.
I will need to see if anything comes out with the oil and look for a stronger replacement one.


I have decided that an electric tractor would be useful if we get the planning permission for our project. I have a suitable old lawn tractor but none of the conversion parts. I see you have plans for greater things so if you decide to sell your tractor / or parts of/ I would be very interested. Rob

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Jeremy
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Location: Salisbury

Re: Tractor from scrap yard finds.

Postby Jeremy » Fri Aug 13, 2010 7:22 am

I've got an unused motor, controller and contactor in the for sale section that would pretty much match the rpm range of the original lawn tractor engine, albeit with a bit more maximum power. On 48V it would run at around 2400rpm maximum, probably fairly close to the operating speed of the original engine.

It might be too expensive for you though, if you're looking for a 'bargain basement' solution.

Jeremy

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Night Train
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Joined: Sat Jun 21, 2008 11:55 pm
Location: Manchester

Re: Tractor from scrap yard finds.

Postby Night Train » Fri Aug 13, 2010 12:35 pm

RobSmith wrote:I have decided that an electric tractor would be useful if we get the planning permission for our project. I have a suitable old lawn tractor but none of the conversion parts. I see you have plans for greater things so if you decide to sell your tractor / or parts of/ I would be very interested. Rob

You could make a tempting offer. :wink:

I am using the tractor as a test bed and will be switching components out of it to get the next project running and legal if I haven't found a cheap controller at that point.

For your existing lawn tractor you would only be looking at a small motor, 6" or 7" will be fine. If it is a belt drive tractor then you only need to fit a similar sized pulley to the motor and then mount in place of the engine.
It may be worth looking for a PM motor or a sepex motor as it won't have the 'run away' tendancy of a series motor if the belt breaks or slips off.
You may be able to find a cheap golf buggy or cart that will give you all the parts you need in one package. You can probably get one for less then the price of a controller. That would save you looking for a controller, throttle pedal, cables, control wiring loom, batteries, charger and, of course, the motor.

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Tractor from scrap yard finds.

Postby RobSmith » Fri Aug 13, 2010 7:14 pm

Night Train wrote:
RobSmith wrote:I have decided that an electric tractor would be useful if we get the planning permission for our project. I have a suitable old lawn tractor but none of the conversion parts. I see you have plans for greater things so if you decide to sell your tractor / or parts of/ I would be very interested. Rob

You could make a tempting offer. :wink:

I am using the tractor as a test bed and will be switching components out of it to get the next project running and legal if I haven't found a cheap controller at that point.

For your existing lawn tractor you would only be looking at a small motor, 6" or 7" will be fine. If it is a belt drive tractor then you only need to fit a similar sized pulley to the motor and then mount in place of the engine.
It may be worth looking for a PM motor or a sepex motor as it won't have the 'run away' tendancy of a series motor if the belt breaks or slips off.
You may be able to find a cheap golf buggy or cart that will give you all the parts you need in one package. You can probably get one for less then the price of a controller. That would save you looking for a controller, throttle pedal, cables, control wiring loom, batteries, charger and, of course, the motor.


The gearbox has a small disc brake on it so running away should not be a problem.
A used golf cart might be the best option like you say.
Also (Newbie question) What is a PM motor? Is that an abreviation or a manufacturer?
Rob

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Night Train
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Joined: Sat Jun 21, 2008 11:55 pm
Location: Manchester

Re: Tractor from scrap yard finds.

Postby Night Train » Fri Aug 13, 2010 9:00 pm

RobSmith wrote:The gearbox has a small disc brake on it so running away should not be a problem.
A used golf cart might be the best option like you say.
Also (Newbie question) What is a PM motor? Is that an abreviation or a manufacturer?
Rob

The runaway in question isn't the tractor it is the motor. If you were, say, pulling something and had full throttle and the belt then slipped off or broke the motor would spin itself to distruction. It is a trait of series wound motors. That is why you would never test one on more then a 12v battery regardless of its rated voltage. It is also why you would want to have a neutral cut out switch so that you wouldn't accidentally power the motor if you are not in a gear.

A PM motor is a permenant magnet motor. Like a seperately excited (sepex) motor the field is not dependent on the current in the armature and so they don't have a runaway problem. A PM motor's speed is entirely dependent on the applied voltage so if it were, say, 10rpm per volt then at 10 volts it would spin at 100rpm and at 100 volts it would spin at 1000rpm. The sepex is even more controllable as you can change the field current independently of the armature current with a sepex controller.

Some of the Americans on the DIY Electric Car forum will advise against a series motor with a belt or chain drive due to runaway and recently when someone found a batch of sepex motors and controllers going cheap so they were bought to power the mower blades on their electric lawn tractors.

Here are some videos of my friend, Jim, and his electric pulling tractor. Don't know if I have posted them before.
http://www.youtube.com/watch?v=aSs1y0SI0Eo&feature=related
http://www.youtube.com/watch?v=0shCm6swxXg&feature=channel
http://www.youtube.com/watch?v=pQRQXGx_5Lg&feature=channel
He is the chap that inspired me to build the tractor.

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Tractor from scrap yard finds.

Postby RobSmith » Fri Aug 13, 2010 9:12 pm

Ahh.

PM....Permanent Magnet......doh....I knew that one
Series wound running away....I did not realise they did that.
Sepex...Separately exited. I presume that is what the Curtis controllers use as they have a separate field connection and I presume it swaps the polarity to reverse the motor?

Rob

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Night Train
Posts: 350
Joined: Sat Jun 21, 2008 11:55 pm
Location: Manchester

Re: Tractor from scrap yard finds.

Postby Night Train » Fri Aug 13, 2010 9:22 pm

RobSmith wrote:Ahh.
Sepex...Separately exited. I presume that is what the Curtis controllers use as they have a separate field connection and I presume it swaps the polarity to reverse the motor?

Rob

The more common sepex controller you will come across is the Alltrax though Curtis do have a couple.
On the usual series controller the Curtis had a connection to the field to control plug braking. From what I have gathered on mine, when I select forward or reverse on the controller the motor is free to spin but if I select neither then the motor plug brakes and stops. It is for pedestrian controlled and some slow speed vehicles where the drive is controlled by a centre sprung joystick. When the joystick is released or reversed the controller will stop the motor from turning rather then just switching off the current and letting it freewheel.

You would still need a reversing contactor to reverse the motor as the field need to have both ends swapped around. For you lawn tractor, if it has a reverse gear then you won't need to reverse the motor so that will save you some money on the contactor.

RobSmith
Posts: 37
Joined: Sun Jul 25, 2010 9:32 pm

Re: Tractor from scrap yard finds.

Postby RobSmith » Fri Aug 13, 2010 10:57 pm

The gearbox does have reverse. That could be confusing to have a reversing control and reverse gear. You could have the motor reversed and in reverse gear and go forwards.
It would be better to keep the motor rotating the same way as the engine did.
Reversing the input to the gearbox might cause thrust problems if the gears are helical cut and any oil system and other items may be designed to work in just one direction.
Rob

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Night Train
Posts: 350
Joined: Sat Jun 21, 2008 11:55 pm
Location: Manchester

Re: Tractor from scrap yard finds.

Postby Night Train » Sat Aug 14, 2010 3:42 pm

Yes, driving the gearbox in the 'normal' direction is advised. Makes life so much simpler too.

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Night Train
Posts: 350
Joined: Sat Jun 21, 2008 11:55 pm
Location: Manchester

Re: Tractor from scrap yard finds.

Postby Night Train » Thu Feb 24, 2011 9:30 pm

While the weather has been georgeous today (well relatively so for a February day in Manchester) I decided to do a bit of work on the tractor.

Yesterday I carefully wheeled the tractor out of the trailer/garage and with about a 50 point turn I managed to make it face the other way so that it was nose inwards. That made it easier to work on the transaxle and get it removed.

A while ago I bought this little thing, it is a Wheelhorse tractor and it should do fine as a replacement transaxle.
Image

I also picked up a Murrey mower axle to start a little kart/tractor for Dad too and with the front of the Wheelhorse removed I decided to see how it looked mated to the mower axle. A little short that way but I think it will eventually work out.
Image
Dad thinks it is a cute size and so I will be starting another EV build. Another thread for the much hoped for new forum.

Anyway, with the tractor in the trailer I began the rear end strip down. I jacked up the back and put it on stands leaving the batteries in the front as ballast to keep the transaxle up in the air. The wheels came off first and then all the ancillaries.
Image

I wanted to leave the brake calipers intact to save draining fluids for now and all the electrics are still connected. I can remove the reversing contactor in due course as the tractor has a 3F 1R transmission.
The transaxle came off in one easy lump.
Image

I took the transaxle into the workshop to have a look at what was broken and on picking it up there was a distinct rattle from the inside. The sort of rattle that sounds bigger then a few missing teeth!
Image
I'm sure I drained the oil when I put her away last August. I am sure of it.

Count the bits of crown wheel! It has exploded into shrapnal, six big pieces, a load of teeth, some crumbs and the two spider gears!
Image

If anyone is a little worried about how much torque a little series DC motor can produce then here is a lesson the hard way.
Granted I was pulling wheelies on 48V at the time. :wink:

I thought it best to checkover the Wheelhorse transaxle too.
Image
The wheels came off and I decided to actually drain the oil on this one before opening it up.
Hmmm, about two pints of water and a pint of mayo came out.

I will definately be splitting this one later to have a look. I will need to replace the axle oil seals in any case as it has been leaking on the slabs outside.

Anyone got a PDF of the insides of one of these? A service manual would be good but a parts image would let me know what I am in for when it is open.
Cheers.


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