Drive Prism Sport Scooter.

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Drive Prism Sport Scooter.

Postby WheelieBear » 11 Mar 2019, 21:16

Hi
I have a Drive Prism Sport Scooter.
I was told by Drive Devilbiss that I need to get a 'motor crown' for it as the brushes are built into this and non-removable

It costs about £20 but I wondered if it would be hard to fit?

Any advice would be helpful.
Thanks.
Paul
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 12 Mar 2019, 02:09

Hard is relative. I would not find it hard. If you struggle with these sorts of things you might. You will need to examine the motor commutator, for damage. And smooth it or clean it with fine abrasive paper by spinning it somehow with a driill or lathe or something if its not clean and perfect. Or it wont last.
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 12 Mar 2019, 11:36

Thanks for your reply.

I'm not a mechanic or an engineer of that type, but I used to be an Electronic Engineer, so I think it shouldn't be too difficult a job to change the 'motor crown'.
However, the only thing I have to clean up the commutator is sandpaper. I have no access to a lathe or power drill, do you think that may be sufficient?
I'm guessing that I only have to remove the carbon and any dirt accumulated on the commutator down to the copper??

Thanks.
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 12 Mar 2019, 12:02

It may be fine. Depends on the reason you are swapping the brushes. If its because they wore so badly that you are having driving problems then the commutator may be burned. If its because they are worn but still working it may be fine as it is.

If it looks like this with a film of oxides/carbon and otherwise perfect dont touch it. This is what you are hoping for!

Image
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 12 Mar 2019, 12:05

If its scored or burned slightly, or not looking like the above it may be rescued by careful use of fine abrasive paper whilst spinning.
If its scored or worse like this heavily worn one you will need a lathe to take a few thou off and have a clean cut. Or replace.

Image
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 12 Mar 2019, 12:10

Image

One of these needs a clean in a pillar drill with fine with abrasive paper. The first one needs either remachining on a lathe if it can be rescued or throwing away.

People wonder why old chairs have terrible range. :clap
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 12 Mar 2019, 21:49

Thanks for the info!

My Drive Prism Sport was bought brand new in 2015 so is now 4 years old.
It has never been serviced and I was going through batteries 2 x 12v 20 Amp various makes every 8 to 12 months.

I now have Leoch 12v 22 Amp batteries only 2 months old and they are great, but have the same problem with the scooter.

With a full overnight charge around 10 - 12 hrs (New charger too), when moving forward the analogue needle gauge drops from full to about 70%,
I thought it was because I'm 17 stone, I put my able bodied skinny friend who is 10.5 stone on it and it does the same.

The DMPS (Drive Medical Prism Sport, Scooter) is designed to support 21 stone with heavy duty batteries up to 15 miles.
I only get about 3-4 miles on a full charge before the light flashes and it cuts out. I turn it off and on again then go extremely slowly to get back to my car.

Was very hard to get info from Drive Devilbiss since I'm not a reseller and only an end user, but I shouted enough on the phone to speak to
a technical support engineer. The engineer said the brushes need to be changed every service and the commutator cleaned every 1yr to 18 months.
I then found out that the Drive Prism travel scooters all use 'motor crowns' that's the Prism 3, 4 and heavy duty Sport. These have non removable
brushes apparently so the whole crown needs to be replaced.

So, this is where I am at the moment.

Cheers
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 12 Mar 2019, 22:29

My Drive Prism Sport was bought brand new in 2015 so is now 4 years old.
It has never been serviced and I was going through batteries 2 x 12v 20 Amp various makes every 8 to 12 months.


Here is your problem.
1. your motor is less efficient than when new. Weaker magnets, less accurate running on bearings, worn commutator, worn brushes. But that doesent meant its completely worn out. It does mean you get less miles per Ah.
2. You are overworking the batteries. To high discharge level daily.
3. You are using 20Ah batteries where 50 or 70Ah batteries are really required. Sorry but thats the truth of things.
4. The biggest problem. You are using cheap generic AGM batteries. Those are JUNK, and they have both a short cycle life, and they are too high impedance or internal resistance. Meaning you see a big voltage drop under load. As you already found out.

I now have Leoch 12v 22 Amp batteries only 2 months old and they are great, but have the same problem with the scooter.
With a full overnight charge around 10 - 12 hrs (New charger too), when moving forward the analogue needle gauge drops from full to about 70%,
I thought it was because I'm 17 stone, I put my able bodied skinny friend who is 10.5 stone on it and it does the same.

Because the batteries are TOO HIGH IMPEDANCE (Resistance). So as you draw Amps, the voltage falls.

The real answer is Odyssey low impedance batteries. And a proper charger. And dont discharge as deeply every day, or get a proper sized scooter with 70Ah batteries. Or go lithium.
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 16 Mar 2019, 10:22

Hey Burgerman,
I respect your opinions and expertise, but I'm limited in battery size with the battery box mate.
only 2 x 22ah or less fit the box.

battery box.JPG

prism sport2.JPG

prism sport3.JPG


Maybe it's a new motor and drive shaft that will be needed.
It ran great for the first 3 years, then the problems started.

Cheers.
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 16 Mar 2019, 11:05

Wrong scooter for purpose. Its a shopping centre machine for your car boot.
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 16 Mar 2019, 11:16

OK, thanks. I thought that was what is was.
I guess I'll need to get rid of it somehow.

cheers.
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 16 Mar 2019, 11:22

Its like using a moped to cross continents. You can. It wont be comfortable. It wont be easy. It will wear out fast and struggle on hills. Dont expect it to be trouble free!

But its worse with batteries and tiny electric motors.
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Re: Drive Prism Sport Scooter.

Postby flagman1776 » 16 Mar 2019, 18:02

What are you trying to do with it? How far do you need to go in a day? How much comfort do you require? How much time do you spend on the scooter? Do you need to disassemble to transport?
If it's the wrong type for the task, then replace it.
I you need a take-apart for transport, then you would benefit from a Lithium (actually we recommend LiFePO4 chemistry). You could also do an add external on pack. All of this pre-supposes you have brought the motors up to spec.
There are a lot of take apart scooters available now.
no longer able to use my TravelScoots
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 16 Mar 2019, 18:21

Hi

I only use it to go to the town to pick up a few bits of shopping, I usually drive into town and have someone with my to help
assemble and disassemble it, in and out of the car.

I only use it 2 - 3 times a week when I go out.
But it's only short journeys, in the town centre and the shopping centre, it hates inclines of more than 10° so I try to go on relatively flat areas.
I never take it off road / pavement.

Thanks.
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 16 Mar 2019, 19:47

If it doesent like slopes its not capable.
If it comes back with dead or even 50% used batteries every day then its not up to what you are doing with it.

It doesent matter if you feel its not far, it matters only if IT thinks its too far. But 20Ah batteries are just daft. Enough to run up and down the street and around your garden for half an hour.

To give you an idea, you will only get a real 10 to 12Ah from those batteries because they are loaded heavily. Thats the same Ah my lithium powerd bot has, and it doesent have a massive human crushing it. Same Ah as this:

http://www.wheelchairdriver.com/gopro/bot2.mp4
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Re: Drive Prism Sport Scooter.

Postby WheelieBear » 17 Mar 2019, 10:29

Your lithium powered bot is brilliant, I'm guessing you built it yourself?
Your bungalow looks gorgeous too.

I see from some of your posts that your not a fan of any of the powerchairs or compact scooters built by the mobility industry.
Neither am I, I believe a lot of them are overpriced underpowered pieces of junk.

cheers
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Re: Drive Prism Sport Scooter.

Postby Burgerman » 17 Mar 2019, 11:13

Yes. I built it. Not the house! The point was to show that the tiny bot has almost as much available Ah battery, as your scooter. And it hasnt got a 1 ton human sat on top! I was trying to show that your expectations from a shopping centre scooter are unrealistic in spite of the manufacturers claims about range or whatever.

The bot usually sleeps in that dog kennel if its raining. Its camera feeds its image to my laptop via radio signal. And I drive it from my bed via radio control. So I see what it does realtime on my screen. So I can keep an eye on the property outside, and the street at night time. Freaks out cats quite well. I can turn on its two "eyes" at night. Or creep around slowly in darkness or hide under my van or neibours cars. The camera sees at night quite well but in monochrome.
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