Electric throttle for 48v motor

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Hello,
I am converting a petrol ride on mower/grass tractor to electric for my young son. Instead of the throttle that increases speed of the petrol engine I want to install an electric throttle in its place. The throttle needs to be some sort of lever that stays in place at the point it is moved to and not return to nothing when released. Any help would be appreciated.
Thanks
 
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you dont have a clutch on an electric set up you need it to return to zero for safety reasons otherwise you have an uncontroled missile if he falls off
unless off course i am misunderstanding you??
 
It is very like a steam engine, you have a rheostat on the field, the stronger the field the more torque, the weaker the field the more speed just like notching back a steam engine, and yes the armature supply is often simple on/off.

However we made some units in Algeria to go inside the 42" pipe line, one guy dozed off when coming back out, he shot out of the pipe like a bullet landed on the ground and the trolley landed on top of him, broke two ribs, so yes it does need some sort of dead man's switch.

Today we tend to use mark/space switching to control power, it does depend on the motor, with permanent magnet it can destroy the magnet, the one I have is 24 volt, it's called a mobility scooter, but the electronic units would not be cheap, the normal way is a kit, this for example .
 
Are you intending to use the seat, clutch & other interlock switches through a relay to become a dead mans switch?
 
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I know most lawn mowers the engine has just two speeds, idle and run, the blades need to rotate at set speed, so pointless having a throttle, often travel is engaged by tensioning a belt, which then asks the question what are you trying to do with a throttle?

I used old dynamos as motors and controlling the field allowed a balance between torque and speed, but today common is to use an AC motor and inverter control, and you have given no details other than 48 volt, or even if toy or doing work, my young son (40) has a very different ability to my young grandson (10) young means lower age to yourself, my son has always and will always been young compared to me.
 
Thanks all of you for your input, much appreciated.
Basically the mower I am going to use has a throttle that is a lever that goes from low to high and stays in the position it is put in. This speeds up, slows down the engine. When the clutch pedal is pressed and gear is selected and then clutch released the mower moves forward. In operation I put the throttle to high, choose a gear and then moved forward by releasing the pedal slowly. Stopping by pressing the pedal which is also a brake. The four gears give a good range of speed.
The power to the rear wheels is supplied by a pulley/belt system from a spindle on the engine to one on the gearbox .
My idea is to replace the petrol engine with an electric motor which will likewise drive the pulley/belt system in exactly the same way. The motor I am planning on using wouldn't be a monster but one that would be used to , for instance, power an electric quad bike ( photo attached.) It would be firmly bolted down to the chassis.
I would want the electric motor to perform in exactly the same way as the petrol one, brought up to the correct speed and then using the clutch, pulley system and gears to initiate movement as normal.
I guess the main elements here are an on off button/switch, motor and some way of bringing the motor up to speed and keeping it there.
For the motor I would think that an 800w 48v would be good? (as per, for quad bike) and wondered if a good heavier duty potentiometer with an on /off button or switch might work ?
The mower/tractor will be only used as a ride on/toy and there won't be any blades or blade protector on it just the main body alsoaalso per photo.
Thanks
 
No photo's attached. You may also find there could be a regulation/law that states there has to be an emergency stop device that would quickly stop the vehicle in the case of someone losing control or falling asleep/off/fainting etc. Safety should be paramount on all vehicles and especially ones operable by children.
 
have a look at 4qd.co.uk You'll find loads of equipment and advice on their site to suit what you wish to achieve.
 
Thanks, yes of course there would be safety cut of switches. They are already on the mower under the seat etc. These would cut off power if someone became unseated. The vehicle wouldn't go more than about 8 mph anyway.
 
I understand what you are saying about if someone fell off a seat, our forklift vehicles worked on that principle, but if someone passes out for whatever reason they may simply slump forward and not activate the cut out. Even at 8mph a person, not just a child, could suffer injury if the vehicle came to a sudden stop by crashing into something.
From my days working in H&S it makes a big difference between coming to a sudden stop because of loss of power and coming to a sudden stop because of a collision. You really do need to consider the safety aspects and not disregard them because you think it's unlikely to happen.
 
you need to work out the rpm off the motor then gear down to nearer 8-20 top speed then work out what power you will have with a perhaps 200 to one reduction so this will increase the power by nearing 200 times so at 48v would probably be a very small motor???
 
I assume you were referring to torque. Power cannot be increased by gearing. That way lies perpetual motion.
 
My 4 MPH mobility scooter has a 270 watt motor, and I know my mother was able to run into me without really causing any harm, I stood there to stop her hitting some one else. However I have read reports of accidents with mobility scooters, and one wonders how they managed to cause so much damage.

The problem with mother was compounded by poor eye sight and I know in Rhyl see drove off a curb which she though was a pattern in the pavement, I read about this accident and my thought was yes could see my mother doing the same, the guy likely did not realise there was glass, but true accidents happen because of some thing we have not foreseen, and with any home made item it is hard to work out what might happen.

However judging from size of mobility scooter motor which is designed for an over weight adult, I would say 800 watt is too large. The scooter weighs 67 kg and uses 2 x 35 Ah AGM lead acid batteries, range 25 miles. I hope this gives you some idea was what is needed, max user weight 150 kg. As already said 270 watt motor, rated 16 amp, 3,300 RPM, 8 kg/cm torque, and of course 24 volt.

Your unlikely to build such an efficient unit, but it should give you some pointers. I would guess it uses some pulse width modulated controller which is not really some thing your likely to build at home.

We would all have liked to have built some thing like that for our children, however I did not have the space they could have used it in. May be this social distancing will cause some relaxation in rules for electric powered vehicles, seems mobility scooters are only permitted where you can't walk, electric bikes have a 16 MPH cut off for assistance 14 year old age limit, 250 watt power limit, must be only pedal assist, at least two wheels with brakes, etc. This has resulted in one wheel and scooters all being not allowed on British public places, and the problem with e-bike is not easy to carry on bus or train. So we have all seen the young child with the electric car, and to be far some have a remote for parents so they can remotely switch it off, so you can't really claim not safe, but when restricted to private ground it means they are rare, so nothing much to copy from.
 
My 4 MPH mobility scooter has a 270 watt motor, and I know my mother was able to run into me without really causing any harm, I stood there to stop her hitting some one else. However I have read reports of accidents with mobility scooters, and one wonders how they managed to cause so much damage.

We would all have liked to have built some thing like that for our children, however I did not have the space they could have used it in. May be this social distancing will cause some relaxation in rules for electric powered vehicles, seems mobility scooters are only permitted where you can't walk, electric bikes have a 16 MPH cut off for assistance 14 year old age limit, 250 watt power limit, must be only pedal assist, at least two wheels with brakes, etc. This has resulted in one wheel and scooters all being not allowed on British public places, and the problem with e-bike is not easy to carry on bus or train. So we have all seen the young child with the electric car, and to be far some have a remote for parents so they can remotely switch it off, so you can't really claim not safe, but when restricted to private ground it means they are rare, so nothing much to copy from.

And the ludicrous situation is that there is no mandated test of competence, no mandated registration of electrically powered scooters or bikes and no mandated public liability insurance requirement.
 

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