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Bob uk
Unregistered guest
Posted From: 94.197.122.90
Posted on Thursday, 29 May, 2014 - 09:03:   Edit PostDelete PostView Post/Check IP

This morning I pop into see a mate who is mucking around with a golf cart

The system is 36 volt lead acid series field DC motor

He has upped the volts to
144

Control system turns
the power on and off fast

The longer pulse the more power the motor produces
If the pules is on say 10% of the time then the average volts is
14.4

Series motors give very high torque when stalled as the rpm rises the torque drops off

The was a big flash from 1the controller and the pulse width went
100% the cart jumped forward

The motor snapped the drive shaft
And went to silly rpm and exploded

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 549
Registered: 1-2008
Posted on Friday, 30 May, 2014 - 22:08:   Edit PostDelete PostView Post/Check IP

He quadrupled the voltage on an electronically controlled motor and didn't expect problems? Why on earth did he think that all the components in the speed controller would be over rated to that extent?

It's little different to taking a stock car engine and adding a huge turbo- or super-charger and assuming that the cylinder compression won't cause problems! I can only suggest that you stand well back the next time you have a look at any of his future dimwitted experiments!
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Bob uk
Unregistered guest
Posted From: 94.197.122.76
Posted on Saturday, 31 May, 2014 - 06:34:   Edit PostDelete PostView Post/Check IP

What actually happened was
A capacitor which runs a 555 timer chip failed and the 555 applied a signal to the thyristor which caused the thyristor gate to close

It should have been ok

The motor was rated at 10hp continuous

Volts is speed and amps is torque

The volts didn't damage the motoro
Series wound DC motors will go vvery fast and shed the windings if the load suddenly goes as in snapped drive shaft

The timer circuit runs on 9volts

It was just unfortunate that a 6 penny capacitor failed

He is redesigning the pulse circuit so that it fails in safe mode

He is a wealth man from selling his patents

He is interested in my design of a speed controller}

(Message approved by david_gore)
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Bob Reynolds
Frequent User
Username: bobreynolds

Post Number: 92
Registered: 8-2012
Posted on Saturday, 31 May, 2014 - 11:31:   Edit PostDelete PostView Post/Check IP

I was just wondering how he 'upped' the volts from 36 to 144 from a lead-acid battery.

That would be about 66 cells in series. Possible I suppose, but a bit cumbersome in a golf cart!
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Bob uk-
Unregistered guest
Posted From: 94.197.122.91
Posted on Sunday, 01 June, 2014 - 03:27:   Edit PostDelete PostView Post/Check IP

He is using 66 lead acid deep discharge cells they are in a trailer

He is fitting an AC motor synchronized motor with vector control and viable frequency invertor controller

Wikipedia give a good explanation of how this system works

Nissan leaf for instance

Once he has sorted the problems he is going to build a system to fit a 1 ton van

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 551
Registered: 1-2008
Posted on Sunday, 01 June, 2014 - 20:47:   Edit PostDelete PostView Post/Check IP

IIRC the torque 'curve' of an electric motor is much the same as a steam engine - flat!
As such a direct connection to one or more wheels is all that's needed to get the plot moving and keep it moving all the way to top speed without the complication of a gearbox to soak up/waste any of the input energy.
Doubtless Crewe had a quiet fiddle with something along those lines in the past and I strongly suspect that BMW are also investigating the possibilities for some future Silver Electra (copyright 2014) to avoid problems with average emissions.
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Bob uk
Unregistered guest
Posted From: 94.197.122.82
Posted on Monday, 02 June, 2014 - 08:56:   Edit PostDelete PostView Post/Check IP

72 cells not 66

Volts equals speed
Amps equals torque

Volts X amps equals power

Speed X torque equals power

I love it when a formula comes together like that

When applied to electric motors

If the motor is stalled the amps go up
Amps X volts is power

And speed X torque is power

But the motor is stalled

Zero speed X torque equals power

The motor is taking volts and amps

Then the only way for formula to hold up is for the torque to be infinite

In practice the motor get hot

Just before it burns out the motor will develop huge torque in comparison to a piston engine

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 552
Registered: 1-2008
Posted on Tuesday, 03 June, 2014 - 19:38:   Edit PostDelete PostView Post/Check IP

Another advantage to DC electric motors is the ability to reverse the current flow - in both senses of the meaning - to either make them rotate the 'opposite' way and/or generate current by being driven. ie. Regenerative braking.

If the primary source of the electrical current is taken from an infernal combustion engine it can be set to run at a fixed speed - much like most electrical generators do - so that the fuel feed system is simpler and the fuel consumption can be reduced considerably compared to taking the motive effort straight from the motor.
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Bob uk
Unregistered guest
Posted From: 94.197.122.91
Posted on Wednesday, 11 June, 2014 - 09:10:   Edit PostDelete PostView Post/Check IP

I went to see golf cart man for up date

He has designed a 50kW ac motor
The max power for 2 mins is 200kw

Which is about 280hp

The torque is flat to 4500 rpm and drops off a lot by 6000 rpm motor is safe to 8000 rpm

The battery is 400volt lithium

The motor is geared at 18mph per 1000 rpm

The control is a pulse width modulated dc which is then split into 6 phases at 300volts 0-300hz

When the motor is started the controller outputs 50 volts at 2hz
This is soft start

Then as rpm increases the voltage increases

As the motor approaches the same speed as the frequency the slip angle between the rotor and stator gets smaller and then the frequency is increased then more volts and so on

The motor rpm chases the frequency which makes torque if the rpm overtakes the frequency the motor goes regenerative braking mode

At 3000rpm the volts are 300

The settings are programmed into the controller via a laptop

And it can perform clever tricks such as traction control and speed hold and vicious braking or no braking and all the shades between.
merely by turning 2 knobs on the dashboard

If it works it kicks piston engines into the weeds

It will work because the gods of lighting at the university are interested

Range is.100 miles

The battery costs 6000 motor 4000
controller 1500

To convert a 1ton payload van is about 15k plus overheads

The drawings now go to his paymasters for yes or no

I wish someone would give me money for blowing up.golf carts

(Message approved by david_gore)
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Bill Coburn
Moderator
Username: bill_coburn

Post Number: 1531
Registered: 4-2003
Posted on Wednesday, 11 June, 2014 - 18:43:   Edit PostDelete PostView Post/Check IP

Now that I have realised you are using the English language I have to say the whole setup of the golf cart demolisher is redolent of the famed Segway, a machine I spent some four hours on and even fell off, in Munich (sp) last year. All power (no pun) to him!
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Jan Forrest
Grand Master
Username: got_one

Post Number: 553
Registered: 1-2008
Posted on Wednesday, 11 June, 2014 - 20:55:   Edit PostDelete PostView Post/Check IP

Even the inventor of the Segway fell off his. In his case he did it next to a significant drop and died from his injuries.
They'll never replace the car with such dross.
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Bob uk
Unregistered guest
Posted From: 94.197.122.73
Posted on Thursday, 12 June, 2014 - 05:36:   Edit PostDelete PostView Post/Check IP

The segway is not a replacement for the car

I have a 4mph disability 5
4 wheel scooter 15mile range

I have dodgy legs

The scooter is brilliant

Anybody can drive it with 5min lesson and no lessons if they can already drive a car

It comes apart in 1 minute put the bits in the boot 2 minutes to assemble no tools required no rush

I drive the car to within a mile of where I need and do the short stop.start bits on the scooter

I made a small trailer out of a rusty pram and a plastic bakers tray I can get a week's food and more on it

I drive around it around Tescos

It had a knob which limits max speed down to 1/2 mph

It has auto brake just let go of thumb lever and it stops fast

The furthest I have been was 5 miles to get a new battery for the car

The scooter is made by pearl and has a psagm motor drive lithium battery cost 700 with charger in 2007

The battrey is still ok and.costs 120 to replace

Best car in the world this scooter is close

In the rain I get wet

(Message approved by david_gore)
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Jan Forrest
Grand Master
Username: got_one

Post Number: 554
Registered: 1-2008
Posted on Thursday, 12 June, 2014 - 22:18:   Edit PostDelete PostView Post/Check IP

Apart from being a bit too large to readily disassemble and chuck in the boot of most cars, my scooter is much the same. Also it uses old type lead/acid traction batteries. Originally they were just 25A/H each, but I replaced them with 140 A/H ones (around 70 each IIRC)and modified the frame to fit over them. Max and min speed are about the same.
The BIL gave me a pair of larger chunky drive tyres for the rear and I bought a pair of similar sized steering tyres for the front which means that I've had to lift the body a couple of inches with some wooden bearers relative to the steel chassis so they clear the arches.
How far it will go on a single charge I couldn't say, but I've ridden it into town (3 miles) twice around Rotherham town centre, out to the car auctions, around the show lot and then back home in a single trip. (8 miles? 10?)
The only time the battery gauge showed any drain was on 'final approach' to my street up a significantly steep hill. Even so the gauge was back to just one 'bar' short of full on the last few tens of yards on the flat as I approached my front gate.
This one is just the latest in a series of 2, 3 and 4-wheel scooters or similar going back around 15 years or so since my osteo arthrosis got serious.
One 2-wheeled electric bike was capable of over 20mph on the flat and soon exceeded its braking capacity on steep downhill stretches. Unfortunately UK law limits motor power to just 200 watts so hill climbing ability was severely restrained and pedaling became necessary. Unfortunately my hips aren't up to that kind of punishment so I didn't have it for long.
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Bob Reynolds
Frequent User
Username: bobreynolds

Post Number: 99
Registered: 8-2012
Posted on Thursday, 12 June, 2014 - 23:21:   Edit PostDelete PostView Post/Check IP

These small mobility scooters can be bought from ebay for as little as 50 to 100. This is because they are almost always collection only, so if you are prepared to travel there are great bargains to be had. Me and the wife have got one each. The small collapsible type that can fit in a car boot. We take them everywhere: shopping, to the park, festivals, on holiday, etc.

They are absolutely brilliant. You can go anywhere, including inside shops, and no more parking charges! It's like riding aound in your favourite armchair, and when you get to wherever you are going you've got a seat to sit on! Because they are only small they are very manouverable and can get through narrow gaps and aisles, and they don't have the stigma attached to them like full-blown mobility scooters weighing half a ton.

They are very advanced technically, with regenerative braking and PWM speed control with constant torque. Simple forward and reverse control to drive. I've added cruise control! 12 miles on a single charge. Cost when new: anything from 850 to 1250. No VAT to pay on batteries or spares.

Yes it's not very nice when it rains, but no worse than riding a bike or walking. We do have umbrella storage under the seats! Fortunately we don't have much rain in the UK.

We are often asked 'Where did you get the scooters from?'. We could have sold them many times over.
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Bob uk
Unregistered guest
Posted From: 94.197.122.86
Posted on Friday, 13 June, 2014 - 08:07:   Edit PostDelete PostView Post/Check IP

The furture is electric

Which is why I got interested in the golf cart man's design

Electric Shadows

(Message approved by david_gore)