How do anti-tip wheels work on Quickie 636?

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How do anti-tip wheels work on Quickie 636?

Postby cyborg5 » 11 Apr 2016, 03:59

As I mentioned in a previous thread, a couple weeks ago I got a new Quickie series 6 power chair. It would be considered a rearwheel drive as opposed to the newer style six wheeled Ms. wheel drive. However it does have two small caster wheels sticking out the back as an anti-tip mechanism. I've had similar "wheelie bars" on other wheelchairs that were just a fixed small wheel with no mechanism to them. I promptly took them off. There are many places I go where I need to go up a curb or a single step onto a porch for example. Always of course with the assistance of an able-bodied person.

But the wheels on this new chair have some sort of strange mechanism that looks like a suspension system. There is a cable running from each one to the front of the chair and connects to a small motor.

I've looked through the user manuals I've seen exploded parts diagrams for replacement parts that I for the life of me cannot figure out what all of this complicated mechanism really does. I don't drive much outdoors except for across a parking lot. I never go over rough terrain. I don't take exceptionally steep ramps unless absolutely necessary and then only with assistance. So I really don't think I need an anti--tip mechanism. I know if I ask a dealer or the factory they cannot tell me that it is safe to take them off because that might make them liable if something happened.

It's not just that they are an annoyance (at least in my opinion) but they also make it difficult to fit my wheelchair onto the lift on my van.

So basically I have two questions…
1). If we remove them, is there some sort of safety system that's going to shut down the wheelchair because my anti-tip mechanism has been tampered with?
2). Just out of curiosity what is all of that crazy mechanism really for?

By the way this chair has tilt and recline in the seat. However my legs are rather short from my hips to my knees. That means that the backrest has been adjusted very far forward which means that my center of gravity is pretty far forward as well. Even in full tilt and recline it does not feel like the chair is in danger of tripping over and of course there is the safety that will not let you drive the chair once it's passed a certain angle which I like.

Any insights you can share are much appreciated.
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Re: How do anti-tip wheels work on Quickie 636?

Postby LROBBINS » 11 Apr 2016, 08:29

Don't know the mechanics of that system, but the purpose is pretty straightforward. In normal use, those anti-tips should be off the ground. If seat tilt, recline or lift would make it unstable, they lower down to prevent tipping backwards.
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Re: How do anti-tip wheels work on Quickie 636?

Postby Step » 11 Apr 2016, 09:38

The 636 is not a rearwheel drive chair.
It's an in between rear and midwheel drive making it very tippy on slopes and curbs etc.
I would strongly advise you to leave the antitips on for your safety
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Re: How do anti-tip wheels work on Quickie 636?

Postby rustyjames » 11 Apr 2016, 21:00

If you're chair has tilt/recline the anti tippers lock when in the tilt position. When you go into tilt a pawl engages to accomplish this. In the normal position the anti tippers have considerable travel for going up small curbs/thresholds, etc. Quickie 626, 636 and 646 are all pretty much the same. The ones without tilt/recline use a different anti tip arrangement that never locks.

@ Step, I have to respectfully disagree with your statement that the 636 is a mid wheel drive chair :P
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Re: How do anti-tip wheels work on Quickie 636?

Postby Burgerman » 12 Apr 2016, 02:06

Its in between. Too tippy for read drive only without anti tip casters. *Much like my own chairs. And the Amy Systems "rear" drive chair. The advantage is stability at speed, no fishtailing, no rear casters digging in in reverse, better manoeverability indoors. But annoying long rear caster anti tips. *In my own similar chair layout I just accept I will fall out occasionally!
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Re: How do anti-tip wheels work on Quickie 636?

Postby expresso » 12 Apr 2016, 22:16

yes leave them there - you may need them - i have the same chair - but mines was touched before i got it - seating etc, and that wire and motor for the anti tippers was removed - so they dont work as the orginal ones -

mines have some travel to move when i go up enough to make them hit the floor and do its job - i use them alot - if not i would be flipping over back for sure -
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Re: How do anti-tip wheels work on Quickie 636?

Postby cyborg5 » 13 Apr 2016, 03:39

LROBBINS wrote:Don't know the mechanics of that system, but the purpose is pretty straightforward. In normal use, those anti-tips should be off the ground. If seat tilt, recline or lift would make it unstable, they lower down to prevent tipping backwards.

I've not yet had the opportunity to take it up or down a curb. Under normal level ground operation they are a bit off the ground but they do not seem to have any give to them. They seem to be quite solidly in the position they are in. Have also not noticed them touching the ground when reclining but I will do some experimenting.
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Re: How do anti-tip wheels work on Quickie 636?

Postby shirley_hkg » 13 Apr 2016, 06:39

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Re: How do anti-tip wheels work on Quickie 636?

Postby Step » 13 Apr 2016, 09:36

@ Rustyjames
No worries about disagreeing.

I didn't say it's a midwheel chair. It's an inbetween chair. A rearwheel with advanced rearwheel position.
Handicare did the same thing with the short wheelbase Alex.

To me, they tried to find the best of both worlds but ended with a compromise that inherited the bad traits of both layouts.
A tippy, front heavy chair with limited outdoor capabilities due to limited curb and slope climbing, that feels agile indoors but is actually quite bulky due to oversized anti tips.
I tested one on the gravel forest trails, mild off-road and uneven sidewalks that I use almost daily and it didn't do nearly as well as my normal rearwhweel Alex.

But others will disagree because it probably does well in wheelchair friendlier terrains.
It's only one guys opinion
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Re: How do anti-tip wheels work on Quickie 636?

Postby ex-Gooserider » 14 Apr 2016, 01:37

My understanding from the 626 I have, and the discussions about this that I have seen elsewhere is that the 6x6 anti-tips are spring loaded, and may have some adjustment in the height of the casters off the ground.

I think I've seen notes of people swapping out the wheels for smaller roller-blade wheels.

The amount of ground contact seems to have increased over the years - reportedly the newer chairs have them in contact all the time, while the older chairs had them off the ground.

They are spring loaded, and in some cases, particularly chairs with tilt/recline or other COG shifting stuff, may have mechanical stuff to either lock them or stiffen the springs when the COG shifts backwards.

I have seen reports of people putting blocks or other stuff into the mechanism to pre-load the springs and get the wheels off the ground.

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Re: How do anti-tip wheels work on Quickie 636?

Postby expresso » 14 Apr 2016, 02:28

i seen a few new models 636 and i have a new 646se over a year old now

from what i was told - and i seen many older models - the anti tippers were in constant contact on the ground in the past - was a problem - and the few new chairs i seen that came direct from sunrise -

there are OFF the ground about a inch at least - they dont touch the ground at all - they have some motor with a cable which if you tilt back enough or wheelie high enough
they suppose to lock up at some point to limit the travel back so you dont flip over and keep it stable if tilting back all the way -


now depends how you have a new chair set up - in my case - my chair came from sunrise - then went to motion concepts to add the seating - lift tilt etc, before i got -

first thing i noticed when i got my chair was - that my tippers were very close to the ground which i know thats not how sunrise gave them my chair -

so i refused to take it unless they lifted them up - turns out - - they did find a way to lift them up - and the reason there were lower down - was Motion concepts - decided when adding the extras on my chair - that it didnt need the motor with the cable to control the wheels - instead they removed it and my wheel were lower because of that -
they still kept me from flipping back and have some spring tension to it - but hit the ground -

they made a part to add - sort of a washer bolt - and that solved it - my tippers are off the ground all the time now - and only when i go up curbs high etc or wheelie some - they make contact and keep me stable -

i can further make it higher by just changing out the wheels to 3 inch models instead of the 4 i have now -

and worst case if nothing worked - -bolt it up - smaller wheel and done - but glad i didnt have to do that - i got them to fix it -

look at the pics -
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646 Anti tipper solution.png
646 Anti tipper solution.png (225.15 KiB) Viewed 327 times
Quickie P222se - - 36ah ADD on pack -
Quickie S646se - - 105ah LifePo4 Pack
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Re: How do anti-tip wheels work on Quickie 636?

Postby cyborg5 » 19 Apr 2016, 23:57

A follow-up on my original post in this thread. Among my papers that came with the wheelchair we found the attached document that explains the little blocks that go into the anti-tip mechanism. My chair had the flat blocks installed and we were provided with the wedge shaped blocks.

One strange behavior… When I first got the chair, the anti-tip wheels appeared to be locked in a downward position perhaps a half inch off the ground. They remained locked there regardless of tilt or recline angle of the seat. This was making it impossible to go up even a modest curb or ramp. We experimented with a rounded curb in front of my house and it would get stuck with the drive wheels coming off the ground and the chair resting on the front and rear casters.

For some strange reason and we don't know why… a few days later the anti-tip wheels unlocked. While they were spring-loaded you could easily reach down and pull one up with your hand. The chair could then easily go up or down a small curb perhaps with attendant assistance.

Anyway for the time being we're leaving everything alone. I don't know why the wheels were locked when they shouldn't have been. I don't know what spontaneously unlocked them. I don't know what the wedge-shaped blocks are supposed to do. At this point I've got bigger problems as you might see from other messages I posted here.
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