Invacare Aviva Storm RX20

[Flagmax]

b y the way the suspension on this chair is not good at all. You feel every little bump. The suspension on that Quantum I linked looks light years better.

Hi Jay, at most I'd call it rubber dampers or shock absorbers in the front. I would not call it suspension. But I can tell it does softens the blows when going over thresholds compared to my old Torque 3.

So I have not been able to get any details how your Aviva casters were fixed. I was wondering, did they happened to email you the repair order?

[Burgerman]

What facinates me is that the only powerchair I ever tested or owned that had a GOOD smooth ride with well controlled long travel and well damped suspension was the INVACARE chair! The Xplore 4 here below. Note also 12 inch caster wheels. And those are stock. They also help greatly.

So we know that they CAN do this and make a great system when they choose to. Rather than a marketing "suspension"...

[Burgerman]

Hold on, Amylior offers lithium batteries? Bounder does? Quantum does? what?

I didn't know any of these manufacturers offered that.

They dont really...
What they offer is pretty much the word "lithium" - the buzz without the huge advantages. Its all a big con, a marketing trick. People dont know much about lithium and they think its "better" because its "lithium".

But lithium is only better BECAUSE its more energy dense, meaning its possible to go from 80Ah lead to a huge 230 to 245Ah lithium in the very same volume as the lead that came out.
That is the thing that makes lithium better. But they dont do that. They typically fit exactly the same sort of Ah as the lead bricks they replace. Entirely missing the point. Because they just dont get it. When you do that you throw away most of the lithium advantages. And add a BMS with potential reliability issue on top.

Lithium CAN offer a huge 600% gain in range if you maximise the Ah properly. It can also then (because of that huge capacity) mean, charging weekly. This shallow discharge level, and/or infrequent charging means at least 20+ years service life. And then you will still have some 60 or 70 miles range remaining once they are knackered!

But they are not offering that at all. They offer the buzz. The word. Its got "lithium"... A small gain in range only. And for hopefully for twice as long as lead but dont hold your breath. And any gain in range, is beause you are running it lower than the lead because you can. Which also means that because of the small capacity offered - typically 70 to 85Ah (instead of 230Ah+) that they get cycled much more deeply on average and at a higher current per Ah. And then charged more frequently. And in so doing that you are throwing away all the benefits that lithium could give by using a far too small pack. At a huge cost££ outlay! They still dont get it.

The gains begin to be pretty worthwhile at around the 120Ah mark. That will get you double the range of lead and a little reserve meaning longer life not stranded suddenly. Or bigger still is better. And get simply HUGE advantages at double that capacity. Because the energy density allows this. And you can do that with 6x the range and 230Ah lithium for less than the cost of lead amazingly enough in 2025. But even though it fits in the same space, they dont...

[Flagmax]

The $2 Aviva's casters fix

I am happy to report that I have fixed all my Aviva's casters issues. Now the casters swivel easily, smoothly and silently. The nose heavy feeling is gone. The Aviva feels like a new chair. I am ecstatic.

I purchased the: Thrust Needle Roller Bearings 0.75 Inch Bore 1.25 Inch OD.
https://www.amazon.com/dp/B09CG2TFJM

They fit the forks shaft perfectly. The bearings are 4mm thick so you can't over tighten the nyloc nut. Perhaps grinding the bevel used for the bronze spacer will allow the thrust bearing to sit flush on the fork is an option. But I kept the bronze spacer in place without adverse affects.

Hope this cheap and easy fix will work for other Aviva owners.

Big thanks to BM and all who offered input.

I added some Mystik JT-6 Hi-Temp Grease.

[Burgerman]

Take out the brass/bronze washer it no longer does anything and is not letting the caster fit up high enough.

Also, just like the one in the video on the pride chair it will corrode to death. Replace with a stainless steel one?

[Flagmax]

Take out the brass/bronze washer it no longer does anything and is not letting the caster fit up high enough.

Also, just like the one in the video on the pride chair it will corrode to death. Replace with a stainless steel one?

Can't do that unless the bevel is removed from the shaft or perhaps need get larger bearings otherwise there is about 3mm gap with these.

I was not sure this fix was going to work so got the cheapest bearing to size. I packed them good with grease. But yah 19mm or 20mm stainless would be nice.

[Burgerman]

I was not sure this fix was going to work so got the cheapest bearing to size. I packed them good with grease. But yah 19mm or 20mm stainless would be nice.

Ebay, in my links up above a few posts back. Yes I would use 20 or 22 even. So that the fillet part you show isnt an issue. Or at least add a thinner 22mm washer.
I think if it was mine I would remove whats there and fit proper bearings though for a complete long term fix.

[Flagmax]

I was not sure this fix was going to work so got the cheapest bearing to size. I packed them good with grease. But yah 19mm or 20mm stainless would be nice.

Ebay, in my links up above a few posts back. Yes I would use 20 or 22 even. So that the fillet part you show isnt an issue. Or at least add a thinner 22mm washer.
I think if it was mine I would remove whats there and fit proper bearings though for a complete long term fix.

You don't think the larger size bearing will wobble or go of center of the 19mm shaft? Also it needs to be 4mm thick. Another thing I can do is add a small 4mm washer on the threads.

[Burgerman]

No the very way it works will centre it. That tapered fillet will also centre it.

[Flagmax]

No the very way it works will centre it. That tapered fillet will also centre it.

Looks like 22mm then. But I will keep the 19mm with bronze spacer for now. Made the marketing suspension better

[Burgerman]

Whats doing most of the work right now is that grease. But it will eventually squeeze out and dry up. If you plan on keeing that setup I suggest drilling and tapping for a grease nipple.

Drill a 5.0mm hole near the centre of the caster barrel in the frame. right into the middle. Tap that with an M6 tap. Fit one of these:
https://www.amazon.co.uk/sourcing-map-N ... =8-30&th=1

I have a box of those things someplace from the days of cars and motorcycles. The manufacturers stopped fitting them. They would rather sell you suspension ball joints, new prop shafts, etc. And on motorcycles, the swing arm and suspension linkages dry out. So at service time, a quick pump with a cheap grease gun and good to go!

[Flagmax]

Whats doing most of the work right now is that grease. But it will eventually squeeze out and dry up. If you plan on keeing that setup I suggest drilling and tapping for a grease nipple.

Drill a 5.0mm hole near the centre of the caster barrel in the frame. right into the middle. Tap that with an M6 tap. Fit one of these:
https://www.amazon.co.uk/sourcing-map-N ... =8-30&th=1

I have a box of those things someplace from the days of cars and motorcycles. The manufacturers stopped fitting them. They would rather sell you suspension ball joints, new prop shafts, etc. And on motorcycles, the swing arm and suspension linkages dry out. So at service time, a quick pump with a cheap grease gun and good to go!

That sound good but not something I can do.

So I ordered 22mm ID bearings to try out and will try to slip this seal over the bearing after heavy packing with grease. Its better than nothing. Where I live nothing rusts and barely rains.

[shirley_hkg]

Is it suitable ?

[Flagmax]

The diameter of forks stem is 19mm and 55mm in length. So if the ball bearing is 10mm thick x 2, then you will need 35mm of spacing. You will need a spacer between top and bottom inside the headtube and about 10mm between bottom bearing and fork. So that 25mm might be just right.

I was thinking getting a tolerance ring for 36mm OD bearings.
https://maedlernorthamerica.com/partsho ... yzAvKJhfiP

[Jay_x]

Great to hear its fixed! Sorry I was not more help to you

[Flagmax]

Great to hear its fixed! Sorry I was not more help to you

I am still curious how they fixed yours and what both "arms" got replaced. In your post you said it still locked up after last fix then magically one day it started working fine. One thing I noticed is that thin wave washer that sits in the groove of the bronze spacer likely pops out because of bad tolerances. This binds the top of bronze spacer to the 1mm wall sleeve in the bushing. Then the fork can only swivels at bottom of bronze spacer until it unjams on the top.

Anyways, adding the needle roller thrust washers made it smoother than like never before. Rolling will always supersede sliding.

[Flagmax]

One fella wrote,

Replaced the washers on my lawn tractor front spindles with these, and the ease of turning was amazing.
This is a must have upgrade for your lawnmower.

If its good for a tractor its good for a wheelchair.

[Jay_x]

Great to hear its fixed! Sorry I was not more help to you

I am still curious how they fixed yours and what both "arms" got replaced. In your post you said it still locked up after last fix then magically one day it started working fine. One thing I noticed is that thin wave washer that sits in the groove of the bronze spacer likely pops out because of bad tolerances. This binds the top of bronze spacer to the 1mm wall sleeve in the bushing. Then the fork can only swivels at bottom of bronze spacer until it unjams on the top.

Anyways, adding the needle roller thrust washers made it smoother than like never before. Rolling will always supersede sliding.

Here is what happened. It was super sticky and near undrivable. My tech came out and loosened up the bolt on both casters and it was improved but still bad. Meanwhile they talked to Invacare about total replacement. then there was a long pause due to some things at the VA (my provider is the VA) so for several weeks I just drove it like that. But then it would suddenly get way better out of the blue and be nearly just fine, then worsen again. Randomly, for no discernable reason. Super sticky, then nearly fine, then back to being sticky again.

Finally the VA and Invacare got their shit together and Invacare agreed to replace the whole thing. I actually did not get a work order because it was all paid for by Invacare so I am unclear exactly precisely what they did. But I can say after that replacement it now drives very nice, very smoothly.

[BCrip71]

Bounder offers a 100Ah one, way too small really but better than nothing at crazy prices. The other will be even worse drop in lead brick replacements. Agai n at stupid prices. But doing it that way offers little gain for big cost. Kind of wastes all the huge advantages of doing the lithium thing to begin with and misses the point.

Quantum rep recommended against them.

Because little to gain doing it their way, with BMS, possible reliability issues and so problems in future probably.

Regardless of this, do you think a 10A lithium battery charger used through the joystick and/or using lithium batteries damage the R-Trak electronics or motors?

[Burgerman]

No.
ONE proviso.

If for whatever reason the built in stupid BMS chops off power as they are inclined to do then the chair rolls a few feet. Its motors are pushed, spun, by the user/chair mass and the energy from the motors has to go someplace. What normally happens it that the power module shoves it back into the battery as a regeneration spike as you decelerate. But if that battery gets cut off by a relay in tje BMS, theres no place for the energy to go. So the voltage spikes up to an extremely high figure and can kill off the power module or at least its mosfets.

Some companies have a warning, like roboteq explaining this and insisting a big diode that by passes an off switch, or a BMS is fitted.

How likely is that? Dont know. Depends on the BMS fitted, the design of the power module etc.

[Arima]

Wow this is super helpful!! I have the same chair and the same issues.

[Burgerman]

You mean the casters?

[Arima]

Yes the casters .

[Flagmax]

Wow this is super helpful!! I have the same chair and the same issues.

Are you thinking about trying thrust bearings or ball bearings?

Invacare chose to go with the "plain bearing" vs "ball bearing" design on the Aviva RX20 available in North America vs Europe.

There are few drawbacks going with this "plain bearing" design.
Disadvantages:

Load Carrying Capacity: Plain bearings generally have lower load capacity compared to ball bearings. In a wheelchair caster, which can experience various forces, this might limit the performance in heavier or more demanding environments.
Friction: Plain bearings typically create more friction than ball bearings, which can reduce the ease of movement and potentially make the caster harder to push, especially on uneven surfaces.
More friction: Could reduce the lifespan of the bearing or cause discomfort for the user if not managed properly.
Limited Speed and Efficiency: Plain bearings may not be as efficient in high-speed applications, but the primary concern is smooth and easy maneuverability for wheelchair users.

In my opinion the "plain bearing" design is not as good as the time proven "two ball bearings" design. The "plain bearing" design uses a single bronze spacer washer to take all the rotational load force. It greatly depends on the weight of the user. Heavier users will feel the wheelchair is harder to turn compared to forks that use normal "two ball bearing" design.

The research showed that for users who require high performance, smooth operation over long periods, or have heavier needs, "ball or roller bearings might be better suited." It's essential to consider factors like the user's weight, the surfaces they typically use the wheelchair on, and their need for "smoothness" and longevity in their casters when making a decision.

[Flagmax]

Two designs,
Aviva RX20 North America

Aviva RX20 Europe

I do want to say that the Aviva RX20 North America elastomer bushings used in casters headtubes do add some ride comfort. There is less vibration transfer to user compared to ball bearings design. So I think adding the thrust bearing is a good option to go with. Its cheap and easy route to go.

[Burgerman]

Of course MOST of this problem is caused by the way they nmake them so nose heavy and long, with the user sat over the front of the chair. That means enormous weight on the castors. And a long chair that is steered by the two drive wheels that are too far behind you. With little traction and a lot more work to do.

So as per usual with every stock rear drive chair you MUST get that seating moved back! You should have a lot more mass over the rear wheels, with them under your backside. Even moing the seat back an inch. Or 2 inches makes a massive difference here. It makes it much lighter to steer, to turn. And shorter indoors. And better traction.

[Flagmax]

Burgerman, I agree with you 100%. But most people are not able to or not willing to move the seat back. Its not an easy task especially if its heavy rehab sitting. They should have shifted the batteries 3 to 4 inches back and put the controller in the front as it was with previous model and go with ball bearings on Aviva RX20 USA like the Europe version. Other than time its a pretty good chair and nice looking, IMHO of course.

[Burgerman]

As soon as I see a chair that is stupidly nose heavy, I look and think its unusable that way.

And they are pretty much. The main reason for the rise of mid drive or front drive. Both of which for other reasons are terrible!

So to me its the only solution.

[Flagmax]

Just a follow up on Aviva RX20 Fix.

I have done the fix to another Aviva RX20 with the same positive result. Adding thrust needle roller bearings gives 300% improvement.

I did a crewed test with a fish scale, pulling on the legrest receiver, I measure how many kg's it took to get the casters to swivel.

Test was done without the user in the chair and the brakes disengaged on smooth floor.

The original "plain bearing" bronze spacer design took 9.8kg to swivel. The casters were "serviced" by a DME tech a week ago (cleaned, lubed).

The addition of the "thrust needle roller bearings" took only 2.4kg to swivel.

How it looks after adding thrust bearing.

[Burgerman]

Hopefully the dme has not used copper grease which is anti seIze on steel things that dont move like bolts and its very abrasive not intended as a lubricant. Thats how it looks?
It needs either a synthetic lithium grease or silicone grease. Because steel/plastic...

The casters were "serviced" by a DME tech a week ago (cleaned, lubed).