Mobility scooter/wheelchair "growling"

As SWMBOs ability to walk is worsening, I've tried to use the advantage of time, to snap up some bargains for mobility.
Have currently amassed 3 portable "Aqua soothe" scooters, and a Roma Medical UL7 "Vienna" electric wheelchair.
The Scooter is a godsend (hence having more than one - a failure would be problematic). Currently, we have "good" on, which whizzes along quietly, with plenty of power.
Which leaves the 2 "spares" which are fully functional. However, they both make a "growling" noise when going along.
As does the powerchair.
Has anyone ever risked opening the sealed motor/gear assembly ? If so, what did you find ? (Hopefully not nylon gears). I note the only spares available seem to be brushes - however I doubt they'd cause the noise I'm hearing.
The powerchair needs new back tyres at £65 a pop (each), so I'm trying to avoid spending money if it'll be a waste.
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Just as a (genuine) matter of interest have you read, or even heard of, Highway Code for MSUs? Of the 52 [police forces in the UK only 24 have properly recorded and reported accidents with MSs and from these there were 5 fatalities so the total is probably twice that. If you injure a pedestrian you could be liable for significant damages so you may wish to consider insurance?
I ask because it is something I'm currently involved in.
--
bert

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On Monday, 15 June 2015 21:32:08 UTC+1, bert wrote:

I guess those figures apply to the 8mph road-giong ones, not the 4mph ones.
NT
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On Mon, 15 Jun 2015 13:18:35 +0000 (UTC), Jethro_uk

The speed control on these things uses pulse width modulation (PWM) which at lower speed control settings often produces a noticeable growling noise - is it there at full throttle?
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On Mon, 15 Jun 2015 22:15:32 +0100, Peter Parry wrote:

Ah, well we *think* it is ... I wonder if this is how the (eye wateringly expensive) control units start to fail ....
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wrote:

The pulse width might not exceed 50% for each motor [alternates left to right, keeps down current draw]. Might need to connect motor directly to test it.
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Unlike powered wheelchairs which use two motors for manoeuvrability most mobility scooters are built to the highest Chinese standards and only have one motor.
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The Chinese will build to any specification required.
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Problem seems to be those who sell them. I do realise they might not sell many - compared to pints of milk - but the prices seem astronomical. Especially for spares. Perhaps they're used to a local authority picking up the tab?
--
*What was the best thing before sliced bread?

Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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wrote:

They're targetted at an age group who are seen as having money available, even if only by "freeing up" the equity in their homes. They're certainly not targetted at the old dears you see shuffling around in a zimmer frame at around 0.2 mph.
But older people with money to spare are seen as any easy target for something which would improve the quality of life for their remaining years. And where cost might not be the first consideration.
Similar cynical reasoning might determine that none of these things are designed to last for say, 20 years. Unlike conventional mobility aids.
michael adams
...
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On Tue, 16 Jun 2015 16:36:56 +0100, michael adams wrote:

SWMBOs first wheelchair was US-made "Quadra Express". Absolutely first class piece of engineering. They went bust after US insurance companies found them "too expensive", and wouldn't pay for them.
It lasted 20 years, and the frame is as good as new. It finally got retired as (a) it had become unsuitable and (b) it was impossible to get a new front caster (this is despite living in Birmingham, the supposed birthplace of light engineering).
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On Tue, 16 Jun 2015 15:02:21 +0100, Peter Parry wrote:

The scooter has a single motor/gearbox assembly.
The wheelchair has 2 independent. Googling suggests the controller programming is quite complex, and can be adjusted quite a bit ....
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On Mon, 15 Jun 2015 22:15:32 +0100, Peter Parry wrote:

Would worn brushes amplify this effect ?
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