10 replies to this topic

[quintooo]

salut all,
i got my new chair, a tilite zra2, just over two months ago. there were a few bumps in the ride, so to speak, in the ordering process - originally i'd ordered it with transit tie-down brackets at the front, but during production i decided against them and wanted the frame shortened the 2,75" that it had been lengthened to accommodate the brackets, but it was too late. thus, the chair is almost 3" too long, which is interesting to live with. i had also originally ordered it with 5" casters, then after renting a chair with 4", i decided on those. there's also not even close to enough dump in it - i think i'm at about 3" and would rather be around 6" or 7". i sometimes use 1" or 2" foam wedges to give myself a bit more of an angle and to raise seat height when i'm wearing thick-soled shoes. ANYWAY. a short while into owning this new chair, which i had fallen in love with, i started feeling something i'd never felt before - caster wobble. i'm not talking about a little bit ; i mean the right caster was nearly spinning 360 degrees at times while i was rolling. having wobble that extreme acted like a front brake and would often jerk me off to one side while i was rolling down the sidewalk. that led to some interesting experiences. i must have been into the shop four or five times by now, and not only have they been unsuccessful thus far in fixing the issue, they don't even have any idea what the hell is wrong with it, and neither does tilite. this is frightening to me. i was wondering if anyone else has ever had issues with caster wobble in a zra model where the chair appears to be in great mechanical condition and isn't being treated particularly badly by its occupant. i'm at my wit's end with this thing - went in to the shop yesterday to get it fixed yet again, but in about three days from now it'll be back its wobbly self, mark my words. ugh. if anyone has ideas, those are welcome too.

[Edinburgh Colin]

First, 2 things come to mind, bent frame and missaligned rear axle.
If you have extreme dump then if one axle bracket is further back than the other it will raise up that corner of your chair thus reducing the downward load on the front caster on the same side. It would need to be a fair bit out as the frame is quite flexible and will soak up a bit of missalignment.
Does it pull to one side when you are on a really flat, level floor like a shopping mall? If so look at that
It's almost impossible to do but, are the rear floor to sear heights set differently?
Lastly maybe they just completely botched the frame, the front caster mounting oval curved tube is not formed correctly, is bent or is not welded in the right place.

These are all fairly major screw ups and you would like to think this kind of thing doesn't happen. Unfortunately it can.

I hope for your sake it's a simple alignment issue, good luck.
EC

[quintooo]

Edinburgh Colin, on 08 December 2011 - 09:51 AM, said:

First, 2 things come to mind, bent frame and missaligned rear axle.
If you have extreme dump then if one axle bracket is further back than the other it will raise up that corner of your chair thus reducing the downward load on the front caster on the same side. It would need to be a fair bit out as the frame is quite flexible and will soak up a bit of missalignment.
Does it pull to one side when you are on a really flat, level floor like a shopping mall? If so look at that
It's almost impossible to do but, are the rear floor to sear heights set differently?
Lastly maybe they just completely botched the frame, the front caster mounting oval curved tube is not formed correctly, is bent or is not welded in the right place.

These are all fairly major screw ups and you would like to think this kind of thing doesn't happen. Unfortunately it can.

I hope for your sake it's a simple alignment issue, good luck.
EC

okay...
i don't consider the dump on this chair to be extreme - front height is 18,5" and dump is 3".
the wobble isn't an issue on super flat ground, like in a shopping mall (which i never go to) or an institution (hospital, rehab, etc.), or inside the university. i never feel that strong pull when i'm on a superflat surface the way i feel it on a sidewalk. i'll check the rear floor-to-seat heights and get back to you on that.
i am starting to believe that your last possibility may be the truth - i think they may have just royally f*ed up the frame. what in the christ do i do if it ends up being that ? what would happen to the chair ? would it have to be scrapped, or what ? how could i ask my technician to check for an error like that ?
thanks so much for your thoughts, i super appreciate hearing from someone who isn't a jerkoff technician who just wants to get me the hell out of their shop.

[Edinburgh Colin]

3" is not extreme but you mentioned wanting more and wedges and things, does not change the basics of geometry just reduces the effect. It pulls on the sidewalks because of the chamber on the sidewalk. It's designed to be agile, having said that do the rear wheels have chamber and is it the same/are the plugs fitted properly?
If the frame is botched and you can prove it by getting it measured then TiLite should replace it. Measuring is going to be difficult as your talking really small tolerances and it should have been made on a jig which should make a screw up impossible. But it happens.

Good luck and let us know how youn get on.
EC

[quintooo]

Edinburgh Colin, on 08 December 2011 - 10:17 AM, said:

3" is not extreme but you mentioned wanting more and wedges and things, does not change the basics of geometry just reduces the effect. It pulls on the sidewalks because of the chamber on the sidewalk. It's designed to be agile, having said that do the rear wheels have chamber and is it the same/are the plugs fitted properly?
If the frame is botched and you can prove it by getting it measured then TiLite should replace it. Measuring is going to be difficult as your talking really small tolerances and it should have been made on a jig which should make a screw up impossible. But it happens.

Good luck and let us know how youn get on.
EC

rear wheels have 4deg of camber and i have a 2deg tube lying around but i prefer the 4. every time i go in they do check the camber on the rear wheels and it doesn't seem to be shifting much - just the first check-up i had it had shifted, but i think they expected that with settling into the new chair.

what exactly would i/my technician be measuring, can you say ? i like to give my techs super specific instructions because at this shop they tend to f* around with you and don't like to get the job done right. they're very particular folk. i wonder, if i ended up proving that the frame was botched, if they would consider making some changes to it when they were replacing it. there are a couple tings i would have changed if i could.
i just don't think my shop is going to want to go along with it... they seem reluctant to do stuff like replacing parts/making a fuss, etc., and this would definitely fall under the category of making a fuss. they tend to tell me i'm overreacting, but at the end of the day they're not the ones who're living in this contraption.

so ye, if you could let me know what i would be having measured exactly, that'd be flex. i'm new to the world of chairs and most often have no idea what i'm doing.

[russ1]

Caster wobble is almost certainly related to the vertical axle the caster pivots around not being at 90 degrees to the floor, a quick adjustment will sort it but you'll need some sort of square to set it right, there's usually a surface on the caster fork that you can work off that lines up with the pivot axle.

[quintooo]

russ1, on 08 December 2011 - 11:26 AM, said:

Caster wobble is almost certainly related to the vertical axle the caster pivots around not being at 90 degrees to the floor, a quick adjustment will sort it but you'll need some sort of square to set it right, there's usually a surface on the caster fork that you can work off that lines up with the pivot axle.

actually russ, funny you should mention that. the second time i went in for repairs for this issue, they checked out the angle. it was off a bit, and they ended up setting both casters to 92deg, which seemed to help for a while, and then... not so much. tilite was telling them to set the casters to 88deg, but that didn't end well. none of the adjustments seemed to do anything for very long.

[megatrig]

Any "wheelchair" company/seller should have a "flat bed". Basically a bit of steel that sits dead flat!

You stick the chair on it and any misaligned angles show up. Anyone who knows wheelchairs can then look at the 4 points of contact to the ground and go "ahhhhhhhh" its the ........ XXXXXXXXXXX ........ that needs adjusting/replacing.

As a start that you can do yourself is the castors. Look at the one that is juddering to try to see if it is angled in anyway or on a hard floor at home if it is not touching the floor.

I have bent the stem bolts (ummm bolts that run through the frame to the castor forks) on my outdoor chair due to its set up and that causes this wobble.

It should be an easy fix. They should know what they are looking for. As you an see from the replies we have all knida picked up on the "mechanics" of a wheelchair. Something you tend to do over time.

Yes it might be a frame that has become misaligned. That is always a worrying thing when flying as the frame can get "pinched", "squashed" in the hold. You then get it back and think ehhhh ....... what the xxxxx. So you may have been unlucky in getting that one frame that is out of true.

If it is wobbling takke the guy outside and say "look" and push up and down so he can see it happening. Lso print this page off too. Save it as a last resort though!!! lol

Good luck. Keep us posted!

[quintooo]

megatrig, on 08 December 2011 - 03:27 PM, said:

Any "wheelchair" company/seller should have a "flat bed". Basically a bit of steel that sits dead flat!

You stick the chair on it and any misaligned angles show up. Anyone who knows wheelchairs can then look at the 4 points of contact to the ground and go "ahhhhhhhh" its the ........ XXXXXXXXXXX ........ that needs adjusting/replacing.

As a start that you can do yourself is the castors. Look at the one that is juddering to try to see if it is angled in anyway or on a hard floor at home if it is not touching the floor.

I have bent the stem bolts (ummm bolts that run through the frame to the castor forks) on my outdoor chair due to its set up and that causes this wobble.

It should be an easy fix. They should know what they are looking for. As you an see from the replies we have all knida picked up on the "mechanics" of a wheelchair. Something you tend to do over time.

Yes it might be a frame that has become misaligned. That is always a worrying thing when flying as the frame can get "pinched", "squashed" in the hold. You then get it back and think ehhhh ....... what the xxxxx. So you may have been unlucky in getting that one frame that is out of true.

If it is wobbling takke the guy outside and say "look" and push up and down so he can see it happening. Lso print this page off too. Save it as a last resort though!!! lol

Good luck. Keep us posted!

thanks megatrig ! i'll need the luck at this rate.
i don't think i have any true flat surfaces in me home ( last tenant was in there for 14 years and wasn't too gentle on the place ).
at the shop though, they have replaced the stem bolt before on the right ( trouble ) side. where would i be looking for angle though ? sorry if i seem a bit thick, this is just a whole new world for me and i'm diving into it, but i kinda suck at swimming at the moment. hah. i am just getting discouraged because it's been into the shop so many times with no solution, and they've gotten tilite's engineers involved in this fiasco and they seem to be totally stumped as well. it seems strange to me that a bunch of wheelies on a forum can come up with tons more ideas than a bunch of technicians. i dunno. maybe they just want me to go away. they're not too keen on me there.

[megatrig]

No pun intended but! Time to stamp your feet!

I'm surprised people higher up aren't more helpful!

You have been unlucky!!

[SCI_OTR]

It may be a "floating caster" caused by the frame being slightly torqued. If that is the case, it may be possible to straighten it out by loosening the footrest clamp and camber tube clamp and realigning the frame. Refer to the owner's manual.