Hello

[Aubrie]

Hi all, I'm in the US and have muscular dystrophy. I started using mobility devices when I was a teenager.

I'm in the market for a new power chair, as my current Quantum Q6 Edge 3 is more than five years old, and its motors have started failing.

I'm working with National Seating and Mobility to hopefully find something great for me. I've never had a rear-wheel drive chair, but after trying it, I think I like it. It was a smoother ride over train tracks than is my MWD, and much smoother than the FWD I tried (a Permobil F3).

I have so many questions, but I'll leave it at that for now.

[Burgerman]

Which rear drive?

The big problem with 99% of them is that they are all far too nose heavy.
This makes them steer badly and feel as long as an oil tanker.

On many chairs this can be fixed with a little work. Move seat back a few inches, centre mount footplate allows heels to then move back 4 or 5 inches between front casters. This change transforms them indoors and makes them turn under you and be much shorter. It also fixes the rear wheel traction or "lifting" issues outdoors and then just work way better. Espeially once programmed correctly.

Do these few things and a rear drive is far superior outdoors and as good indoors as any mid drive. Front drive? No way!

[Aubrie]

I tried the Invacare Aviva Storm RX. Great to know about the seat and heel positioning. I like having my heels tucked back anyway. Here's a picture of me in the demo chair.

I always drive tilted back to stabilize my sitting. I don't like having my feet extended outward. I want to be able to have my feet go back much further. I'm not even sure if that's possible with center post. I've heard it can go back a little, but can it really go back enough?

In a few weeks, I'll be comparing it with the Quantum R-Trak. Unfortunately I don't have many options beyond that if I want high speed, high speed at elevation, and a smooth ride. At least that's what I'm understanding.

[Burgerman]

You are small and light. So CG position doesent matter that much compared me or any bigger overgrown human! But you are sat a long way forwards. That may feel a bit unweildy indoors. And lose rear traction (and steer control) on uneven surfaces.
You might want to cut off that huge spike sticking out behind the headrest as it will hit everything around you indoors and confined spaces.

You seem to be tilted back a little. Maybe 12 dgrees. Its more stable, and less bouncy (greater rigidity) if instead you adjust the base tilt angle (the initial dump angle) so that it is where you want it to be when the seat is at its fully lowest position. I always do that so that my initial "dump" angle is 6 degrees on my chairs for my own purposes. So that theres no bounce or flex in the tilting mechanism. Feels much nicer to drive that way.

How far back the footrest and your heels can go is determined by a guy with the tools, and the front casters. These must be free to rotate as you manoever around without hitting the footplate. Even a 3mm gap between tyres and footplate is enough.

Then theres programming. A huge thing to me at least!

The problem for me would be that I couldnt program either of those chairs to steer properly and work well as that needs OEM level access programmers. Usually. And its not available to even the techs without a fight or at all with prides stuff. Its possible but difficult to do with Invacare controllers.

So that may or may not bother you. ALL stock chairs steer in what I call hovercraft mode. It can be improved partly with dealer level programming tools. Because of that I choose chairs with r-net control systems. But rear drive in the US is highly problematic. Not much choice.

I just aquired a goverment funded rear drive chair and actually have had four different full rehab ones here. The last 3 are all R-net control systems though.

[Aubrie]

Great advice. About the huge spike—my plan and hope is to get a backrest that goes up higher and also serves as a headrest, so that I don't need a separate headrest attachment. Have you seen anyone do this?

Programming is so difficult for me to get right. I didn't know the techs didn't necessarily have OEM programmers.

What kind of rear drive chair are you getting now?

Interesting idea about adjusting base tilt. But is more rigidity / less flex better? I felt as if the FWD I tried was a much rougher ride because of how rigid it was. The tech also said programming can make it less bumpy. How is that possible?

I made a comparison video:
https://youtu.be/B1GEJynyGiE

[Raro]

Hi Aubrie.
Even if you like to drive so upright, you should not have the backrest so reclined. You have less stability than if you were supported and you would suffer less jolts in large potholes. If possible, I would also raise the tips of your feet a little. It always gives a little stability if you allow it. your physiognomy It's just advice, everyone decides in their own way in the end.

[biscuit]

programming can make it less bumpy. How is that possible?

It is totally possible, like adjusting the house thermostat according to your own preferences over time, anyone can do it if they want to. I like many others here do it as a matter of course on any wheelchair I get, to make it steer properly and also to get a smoother ride. I have had much help with this from this forum. I find the VSI (and VRS) controllers programmable enough for my needs (it looks like I'm about the same build as you). And it is fairly intuitive, though some values can't be guessed. I have never used the R-net system, I think these other PG Drives systems are not as versatile as that.

[Burgerman]

At weights like you are say 50kg? Then a 90A controller is enough for 6mph, (VR2?) and you only need to go to r-net 120A for 8mph speeds.

I am heavy. I need 120A for reliable control on 6mph chairs.

Also consider that a basic chair with "full sized" 70 to 80Ah batteries and no seating options is approx 100kg. Or less. When you add power options, it adds an enormous amount of mass. Lift, tilt, foortrest, recline, lights on a typical rehab syyle chair will mean 170 to 200KG for the chair. Double the weight! Its not just the user weight that matters.

Its total weight. More mass means more Amps...
R-Net can be 60 80 90, or 120A depending on order.
https://www.cw-industrial.com/en-gb/med ... ility/rnet
Can be very complex systems if needed.
https://www.cw-industrial.com/sites/def ... ochure.pdf

nVR2 can be 40A on basic drive only folding chairs, VR2 60,70 to 90A max. Limited seating and programming options. A simpler more basic system.
https://www.cw-industrial.com/en-gb/med ... controller
https://www.cw-industrial.com/sites/def ... System.pdf

Yes dont lean forwards, make sure seat depth is correct. Configure EVERYTHING to fit you! This takes at least half a day with a fully equipped workshop, and programming takes a week to fine tune to your preferences. You learn what is best as you go. I still make small changes 20 years later.

TOO MANY amps is never an issue. Too few is always a problem as you dont have adequate torque. Theres never a reason to want less.

ADDED.
In your picture you look to be sitting on the friont edge of a seat that is too wide and too deep. And so too far forwards. And in a position that isnt stable. And yes footrest angle needs to come up at the front as you seem to be "standing on tippy toes" if you see what I mean. EVERYTHING including arm top height, forward position, joystick position, etc is all adjustable to fit you. If its not you need a guy that gets it, with a saw or a drill.

[Burgerman]

Great advice. About the huge spike—my plan and hope is to get a backrest that goes up higher and also serves as a headrest, so that I don't need a separate headrest attachment. Have you seen anyone do this?

Me. I take any chair, that suits my requirements, then I ADJUST, SAW, CHANGE PARTS, MODIFY ETC as required to make it work properly.
I mean all of it!

Programming is so difficult for me to get right. I didn't know the techs didn't necessarily have OEM programmers.

Its much worse. They wont set it correctly for you, or change much at all even if they have the tools which they usually dont and dont undrstand what they are doing in my 36 years in a chair experience.
So getting hold of an OEM level tool, is pretty much essential to me.
The only game in town is now R-Net as invacare, pride etc are all locked down...



In your vid on the road hump, you nearly fell out of the chair because you are sat over the front! TOO FAR FORWARDS and sat upright with no weigh on the backrest. And so as soon as the front wheels on the rear drive chair touch the start of the speed hump it launches you into the air! Your backside needs to be over the drive wheels! And you need to be leaning on the backrest. Not sat up hanging over the front!

What kind of rear drive chair are you getting now?

I only ever get rear drive.

Heres a few of them.
NOTE that all are modified a little or a lot depending on what needed to be done to configure them properly! With me seated correctly, and programmed to steer and drive properly.

I got this for free, UK government, my assessement etc.
https://www.wheelchairdriver.com/board/ ... =2&t=12461
Scroll...
It fitted my requirements. Not how far back the seat is.
A reflection so I can photograph my position...
Also note headrest mountings. All shortened and some of it thrown away so is compact.

BUT NOTE ESPECIALLY the position of my backside in relation to the drive wheels...
This is true of all my chairs (to a greater or lesser degree) regardless of what it took to achieve. Or they all drive crap!!!

Seat moved back, correct static dump angle, armrests confiured etc.

[Raro]

Standing on tiptoe is typical of this disease, which is why I say correct it if you can...

[Burgerman]

Some of my other rear drive chairs, all similarly set up.. All feel same to drive.

DIETZ SANGO ADVANCED
And INVACARE STORM 4 XPLORE...

[Burgerman]

SALSA best of the lot!!!

[Burgerman]

And a BM1, BM2, BM3, etc...

All same layout, similar programming, same seating position, same CG etc.

BM1, BM2, BM3... A series of chars, all similar and all different!

[Burgerman]

Q700 R (Sunrise Medical)

Martin my carer...

More...

[Burgerman]

Theres more but you get the idea...
ALL are fine tuned and configured - regardless of work needed - to fit ME and to work correctly. Once you do that, they all drive pretty much identically. Hard to tell one from the other.

But my ass sits very rearward. Over the drive wheels. So the casters do not have me sat over them. And I lean back on the backrest as thats essential.

[Aubrie]

Raro—thank you. The backrest is only that reclined because of how much tilt I needed. It won't come up any more than that at that level of tilt.

biscuit—what parameters do you change for a smoother ride? Do you have a front-wheel drive?

Burgerman—wow, what a fleet! That's amazing. Great photography, too. I'm envious.

The problem is, I can't sit against the backrest the way others do, because I have severe lordosis. In those demos, my bottom actually is sat back in the chair, but the curve of my spine makes my torso crane forward from there. The back of my shins are against the seat cushion and footrests. I will have to ask about moving the whole seat pan back. I'm not sure if that would affect my transfering. I'm less than 40kg and get manually lifted by an attendant (no hoist).

I'm still parsing your advice about what the amps mean and what my options are.

How would I go about fine-tuning the programming? Do I have to call them every time, or can I get something myself?

[Burgerman]

Theres literally hundreds of intereactive settings. Forget permobil as that wont ever steer well. Front drive just cant.

You couldnt expect anyone else to program a chair properly for you, as only you can experiment with so many variations or settings. You need to change them one at a time from one extreme to the other to feel what it does. Then set it where you think you need it for now and lock that feel away in memory... Then change another etc.

I know what I am doing and I couldnt set up a chair at all speeds etc that I would want in one go. Its a thing you configure over time. The idea that you could get some "expert" (they dont have a clue, or the gear, or the will) to do that for you is unrealistic. The best you will do is get a few minor changes done but wont know what if anything they have done.

Settings... I tried counting but its too complex. I gave up at 200.
Really you need a programmer.

As for your seating seup, if it were me I would adjust the seat base width, narrower from what saw. Set that level of tilt you need as the base angle. And that may need drills, etc. Cant know until you do it. Then adjust the backrest linkage so that in fully "forward" position it is in the right place to support your back. Then put the joystick in the correct place. Footrest etc as needed. Since you have so much tilt, as a base angle your feet can go back a lot as they are above the casters. Anyway its a case of a man with tools, knowledge, attitude, and sort it out! The issue is to find that person wont be easy. Chair techs tend to be pretty useless across the industry. Thats why I ended up doing everything myself.

[martin007]

Welcome to the forum Aubrie!

I have SMA.
> https://en.wikipedia.org/wiki/Spinal_muscular_atrophy

Do you run that many miles?

[biscuit]

My chair is RWD. I wouldn't want a FWD one. I watched your video, a good comparison. My health fluctuates wildly and I got rid of all my heavy chairs with heavy machinery, actuators and other controllers some years ago when I realised they were overkill for me. The one I use outdoors now is a supposedly folding 4mph wheelchair with a VSI joystick. It has lead batteries (safer than the popular lithium ion, but as heavy as lead) and 2-pole motors. And a VSI I can programme - and it needed it urgently too, as it was a dangerous bucking bronco to start with.

Burgerman is correct as always (BTW thanks for the controller info, Burgerman!). You have to do your own programming. Over time. Nobody else will do it better than you. My settings are brilliant for me, but most likely rubbish for anyone else.