Why's my powerchair such a rock hard ride?

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Why's my powerchair such a rock hard ride?

Postby Scooterman » 06 May 2019, 09:50

Whenever I go over even a small bump/lip it's got no give whatsoever in the suspension. In fact at top speed you often hear the batteries clunk as they take off and land back down again.

I pump the tyres up firm'ish with a cheapo bicycle pump, but never up to their rated pressure.

Are the coil springs too high a rating as I've lightened the chair quite considerably?

Or is it because the powerchair has a short wheelbase?

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Re: Why's my powerchair such a rock hard ride?

Postby Burgerman » 06 May 2019, 09:56

Thats one reason I use fatter wider and lower pressure tyres. Its a combination of, hard tyre, short suspension travel, hard suspension spring rate, and your light weight.

The chair is lightened. Estimate it at 80kg absolute max with your weight on top. My salsa is 185Kg and a 20 stone me on top... I suggest softer shock spring. 3 different ones available on the order form.
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Re: Why's my powerchair such a rock hard ride?

Postby Scooterman » 06 May 2019, 10:17

Burgerman wrote:Thats one reason I use fatter wider and lower pressure tyres. Its a combination of, hard tyre, short suspension travel, hard suspension spring rate, and your light weight.

The chair is lightened. Estimate it at 80kg absolute max with your weight on top. My salsa is 185Kg and a 20 stone me on top... I suggest softer shock spring. 3 different ones available on the order form.

Ooh are there, I didn’t realise that! I think the ones on it are 250lb but I will check :thumbup:

But I plan to go lithium like you (old LA’s at moment) so that will lighten it even more. But I was think of only 8 x 90Ah or 105Ah cells (whatever available). As only use chair outdoors a few times a week and don’t go far usually (4-6 miles or so). And don’t want to replace lead bricks with new lead bricks when 8 x lifepo4 not much more expensive. :Thumbup:
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Re: Why's my powerchair such a rock hard ride?

Postby Burgerman » 06 May 2019, 10:37

Too high loading. You may damage those low rate cells if you only use 8. Order 16. Or the 176Ah ones. The cellswill likely swell or bulge, go high impedance if there isnt enough Ah.
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Re: Why's my powerchair such a rock hard ride?

Postby Scooterman » 06 May 2019, 10:48

Burgerman wrote:Too high loading. You may damage those low rate cells if you only use 8. Order 16. Or the 176Ah ones. The cellswill likely swell or bulge, go high impedance if there isnt enough Ah.

Oh really, I didn't realise that, I shall save up :thumbup:

I can't wait for you to do yours.

I learned some of what not to do with the scooter packs, but i wanted to get them done and was useless at soldering then but am better now. :thumbup:
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Re: Why's my powerchair such a rock hard ride?

Postby Burgerman » 06 May 2019, 10:58

My issue right now is money. I just rebuilt my house after insurance paid to do floors and walls in 3 rooms after a slow 6 month leak... While I was on my bed with a sore. So just recovering from a 3 or 4k redecorating, new sofas, new oled TV, new lights, UK flag, carpets through all 5 downstairs rooms. And new light switches, etc etc. Then the fridge failed, 900 to replace. Followed by the dryer, on mon, and the washing machine wed... That was all over xmas and end of last year. Still paying for all that $$$$$$$$$$$$ on benefits!

And I need...
Motors for BM3
Footplate for /and green chair finishing.
100 smaller things.
THEN I can get to the 16 cell 200Ah lithium pack...

Time and money holding me up :cussing
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Re: Why's my powerchair such a rock hard ride?

Postby wheelie junkie » 06 May 2019, 11:59

Another vote for bigger tyres, mine is much more comfortable with the 120/70 x 8 tyres. I've also replaced the front casters with tubes.

I'm now looking at springs, the front is too soft and compresses when I slow down quickly, with a rearward COG the front lifts under acceleration then dives as I slow down. I'm only 65kg so not very heavy, lithium batteries on order so chair weight will come down but I still feel that firmer springs will help albeit at the expense of a firmer ride.

Springs lighter than 250lb might be hard to find but remove spring from shock, measure the overall length and internal diameter and hunt in mountain bike and scooter/monkey bike shock makers catalogues. I've struggled to get lighter springs for my off road wheelchair and ended up replacing coil with air spring running low pressure. Not very cheap to do however.
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Re: Why's my powerchair such a rock hard ride?

Postby Burgerman » 06 May 2019, 12:46

I second a set of these on your salsa...
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Re: Why's my powerchair such a rock hard ride?

Postby ex-Gooserider » 07 May 2019, 03:07

Another factor that isn't really changeable, but is going to make most all chairs rougher riding is that you have a very high 'un-sprung weight' - or %age of the chairs weight that is not supported by the suspension, but instead rides more or less directly on the road...

In a car, this is basically the tires and swingarms or other suspension bits... The total is a fairly low %age of the total car's weight but since lower is better, is one of the reason why big cars tend to ride better than little ones.... Same deal applies to bikes...

On most chairs, if there is a suspension, it is usually designed with the motors as part of the un-sprung weight since the motors are usually attached to the swingarms - which has the advantage of letting the wheels fasten directly to the motor output shafts instead of needing drive chains or similar linkages, but makes the suspension less able to respond to bumps...

Essentially the added weight increases the inertia of the un-sprung parts so that it takes more force to get the suspension moving in either direction to soak up a bump or return afterwards... In turn this means more springing and damping is needed to compensate, which helps and hurts at the same time... (lots of compromises involved....)

Most chairs are also limited to very short 'travel' in the suspension by the nature of their design, which means they have less distance to use in soaking up bumps...

Not much can be done about either, the best that can possibly be done is to try and get a balance of spring tension that gives a reasonable compression while sitting still, while not topping or bottoming to badly on bumps, and getting the damping as low as possible while not 'pogo-sticking' after hitting a bump... How much can be done is limited by parts availabliity - though the suggestion of checking out the small motorcycle and pedal bike shock market has merit...

Also running larger tires at lower pressures will help by letting the tires absorb more of the abuse...

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Re: Why's my powerchair such a rock hard ride?

Postby Mechniki » 13 May 2019, 19:26

Scooterman wrote:Whenever I go over even a small bump/lip it's got no give whatsoever in the suspension. In fact at top speed you often hear the batteries clunk as they take off and land back down again.

I pump the tyres up firm'ish with a cheapo bicycle pump, but never up to their rated pressure.

Are the coil springs too high a rating as I've lightened the chair quite considerably?

Or is it because the powerchair has a short wheelbase?

Image

Image

Those springs and shocks look adjustable to me, and they look like they're in a "soft" position. I doubt if they offer much more than a motor dampener for when the chair motor stalls a little when it encounters a bump or pebble. Cannot see from the pictures, if under the side panel there is a swinging arm? Often they're over tightened and unlubricated, generally I use copper grease there.

The batteries jumping around in their containers is a separate issue, normally caused by lack of padding. The old 5mm mouse mats work quite well for padding or a newer version 3mm mat rolled up. Most armchairs have springs then cushions, but most wheelchairs have a solid base to which a cushion is fitted to act as your suspension. It may be a simple matter of changing the cushion for something with more spring, Unfortunately that means going to a dealer or having an OT visit to get the right type for you, not something you want to buy off the internet as they can be expensive. Personally I find GEL cushions more comfortable. But have used GEL with memory foam (2 separate cushions), but then one has a tendency to move off the chair. SO then you have to get a cover made to fit both.

A scooter seat is padded and sprung, much like a car seat, often providing more comfort than padding alone. I
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Re: Why's my powerchair such a rock hard ride?

Postby Mechniki » 13 May 2019, 19:40

Looking at the sag in the back cushion and the sun bleaching, that could probably do with a replacement pad too. The seat cushion looks like the invacare, 2/3 inch Gel a 4 inch would probably be better
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