Announcement

Collapse
No announcement yet.

Tuning in a trial ZRA chair

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Tuning in a trial ZRA chair

    It is an interesting exercise with decisions that will stay with me for the next period after issue of a new chair.
    I have tried out different configurations with this ZRA.
    Then the other night, while you tubing wheelchair videos I noticed the larger number of wheelchair drivers that had a good 1-2" gap between the seat cushion and behind their knee.
    A eureka moment?? All my seated life I have used a 18" x 18" cushion as originally prescribed which abutted up against my knee/calf.
    I am short in the leg and longer in the torso.
    Perhaps the main culprit may be my cushion depth?
    So today I sat forward on my cushion and discovered that with the added clearance I could comfortably tuck my legs and bring my feet back where they no longer protruded beyond the foot plate.
    It felt better for that short time.
    Today I shortened the ZRA sling. I have removed the sling supports from the ZRA and folded back under the first section of sling then reattached the supports to the chair frame.
    I threw on the cushion from my wifes' 16 x 16 loan chair and am about to give it a test run. I also dropped the RSH another two notches to 15 3/4" - FSH is 18 1/2" and changed the COG.
    Here is hoping that I have come closer to comfort and efficiency.
    What distance do others maintain between their cushion and knee?
    Last edited by slow_runner; 5 Apr 2021, 9:24 PM.

    #2
    I use two finger widths or 1-2" gap from seat front to back of the knee. Being a T6/7, I use a 4 inch drop front to rear with approx. 92o back angle. For cog, I line up where my fingers are about in the middle of the axle button holding on the wheel. I used to have the cog a bit more forward to where if I leaned back the front wheels would lift easily. Now that I'm older I don't do wheelies near so much. Main thing is any changes to the ZRA make sure the front casters are at 90o.

    Comment


      #3
      Originally posted by Patrick Madsen View Post
      I use two finger widths or 1-2" gap from seat front to back of the knee. Being a T6/7, I use a 4 inch drop front to rear with approx. 92o back angle. For cog, I line up where my fingers are about in the middle of the axle button holding on the wheel. I used to have the cog a bit more forward to where if I leaned back the front wheels would lift easily. Now that I'm older I don't do wheelies near so much. Main thing is any changes to the ZRA make sure the front casters are at 90o.
      Hi Pat. I made the changes described previously and ran about with it yesterday. A nice difference with the gap behind my knees - how long have I 'ran' with my knees against the cushion? A lot !
      The Agility back feels like it needs to be moved further back but there is no more adjustment that I can see. I feel like I need to sit further back into the chair - I will check the back angle.
      Question- is the back angle measured from horizontal or relative to the frame seat rail?
      The Roho Hybrid Elite does a good job of locating my thighs and stopping my leg from falling to the right and causing my calf to pressure the frame. It is good for that but feels way too high - 4" from memory. My OT is sourcing the lower version to test.

      The front castors are wee 3" plastic units that I will replace with a pair of old worn 4" soft rolls as I prefer them. For this trial they will gain me an extra 1/2'.
      At this point I am considering 80* frame with an extra 1" frame length and height.
      ?? All just thoughts at this point.??

      Not much achieved today. A late start as my wife had her hospital bed delivered and set up. She loves it; no more propping up on pillows and aggravating her tumours.Then the day just got away so I flowed with it.
      More on the chair tomorrow.
      As always, thanks for your experience and input Pat. Be well.

      Have you ever balanced on a large icecube? https://www.youtube.com/watch?v=lwDyrespV7s
      Last edited by slow_runner; 7 Apr 2021, 3:23 PM.

      Comment


        #4
        I can barely fit a hand between my upper calf and my cushion, but my legs are also at maybe a 75 degree angle making the most forward part of my chair/body the footplate followed closely by my knees. That was i have the shortest possible turning radius and as an added bonus i can use the footplate to help push open doors without worrying about injuring my feet.

        Comment


          #5
          Originally posted by funklab View Post
          I can barely fit a hand between my upper calf and my cushion, but my legs are also at maybe a 75 degree angle making the most forward part of my chair/body the footplate followed closely by my knees. That was i have the shortest possible turning radius and as an added bonus i can use the footplate to help push open doors without worrying about injuring my feet.
          Hi funk. 75 degree as in the right image ? I have a large carpenters protractor in the shed that I need to access...now, where is it?

          Click image for larger version

Name:	75.png
Views:	138
Size:	7.1 KB
ID:	2908394

          Comment


            #6
            Originally posted by slow_runner View Post

            Hi funk. 75 degree as in the right image ? I have a large carpenters protractor in the shed that I need to access...now, where is it?

            Click image for larger version

Name:	75.png
Views:	138
Size:	7.1 KB
ID:	2908394
            I guess it depends on which way you assume the chair is facing, but yes the right image if the chair is facing to the right. So my toes are basically directly in line under my knees.

            Comment


              #7
              Thanks for the clarification Funk. There was bugger all progress today with other matters needing attention. I did swap out the casters for 4" softs; for now they are floating on the axles as the outer spacers are later issue and I couldn't be stuffed swapping out the bearings as well. Moved the COG forward 5mm. The rain started in so I retreated inside with the chair in the hope of a trial before hitting the sack.
              Just weighting the back canes by hand, it could be a touch tippy? No trial though, that stomach bowel feeling was presenting so rather than risk mishap in mid transfer, I have left it for Saturday.
              Last edited by slow_runner; 9 Apr 2021, 6:47 AM.

              Comment


                #8
                TiLite backrest angle is measured from the horizontal plane (floor), not the frame.

                I have ~1" clearance behind my calves. My feet sit tucked under my knees though, pulling the calves back a lot. Maybe 2-2.5" clearance otherwise.
                "I have great faith in fools; self-confidence my friends call it." - Edgar Allen Poe

                "If you only know your side of an issue, you know nothing." -John Stuart Mill, On Liberty

                Comment


                  #9
                  Perhaps once you get it dialed in; just order a ZR or better yet a Tr. One of the big obstacles I found with the ZRA, other than the larger tubing was getting the two front casters both aligned so there wasn't one of them floating in turns. The extra 1" extension before the bend was a big plus for me.

                  The guys explained the back angle in earlier posts. For myself, it was just a matter of moving the screws defining the angle to the next hole to 92o forward.

                  Comment


                    #10
                    Hi Pat.
                    Yeah, this one has the floating caster characteristic. with straight line running it doesn't give any indication because of the weight(?) but I imagine that in turns when weight shifts, it would lighten the inboard caster.
                    I am leaning toward a TRA and hoping they can supply one for comparison (frame flex ..).
                    A shorter seat gives me that clear frame for transferring- I may go 80*, assuming 19" FSH that will give another 1 3/4" at the front. My legs don like being tucked.
                    This morning I had a run with it. it is better balanced. I'm still not happy with it.

                    Thanks for the information Odd.

                    Originally posted by Patrick Madsen View Post
                    Perhaps once you get it dialed in; just order a ZR or better yet a Tr. One of the big obstacles I found with the ZRA, other than the larger tubing was getting the two front casters both aligned so there wasn't one of them floating in turns. The extra 1" extension before the bend was a big plus for me.The guys explained the back angle in earlier posts. For myself, it was just a matter of moving the screws defining the angle to the next hole to 92o forward.
                    Last edited by slow_runner; 9 Apr 2021, 9:29 PM.

                    Comment


                      #11
                      Basically, once you know the dump, width of chair,1" added to frame length, seat length and front and rear seat height along with if you want a tapered front end, front frame angle and width of footplate; there's nothing more needed. Caster size wheel, wheel size and cog doesn't make much difference because they can be adjusted either by the holes in the fork for caster size and rear wheel size along with the cog adjustment makes it easy to adjust and no messing around trying to get the casters both to not float in a turn. Also would be much lighter. Back angle adjusts.

                      Standard dump for most is if you have good lower core 1-3" dump; for higher injury around 4" is standard. I order a 4 inch deep ridgidizer bar to the extra depth needed if I use a solid back.

                      I'm a T6/7 with 18x18" frame width and length with 80o frame anglewith 12.5" footplate width which gives enough width to wear boots if I choose or attach my Freewheel. 4"x1.5" softroll casters, 559 rear wheels and added 1" between front of seat and where bend begins for better gripping the frame when needed and 0 degree camber because I like a narrower chair and use the Stricker attachable handcycle allowing me to lift the front wheels off the ground with no drag when bike is attached. I can change the back angle and height if I buy a different type cushion and cog easily.
                      You've been around chairs long enough where you may not need an adjustable because you already know the dump, width and seat length along with front and rear seat height.

                      I can't seem to attach my order form so will send you via email







                      Attached Files
                      Last edited by Patrick Madsen; 10 Apr 2021, 3:52 AM.

                      Comment


                      • Oddity
                        Oddity commented
                        Editing a comment
                        Looking at why those files didn't attach. They did, but the identifiers in the database for the files got changed. Did you happen to edit the post during the process or just after? Looks like a bug happens when editing posts with attachments being added at the same time...might have been that. Otherwise I'll send it to vBulletin support to look at.

                      #12
                      I think I did edit the post just after and probably tried reattaching a couple of times. It was late and wanted to get it off to S-R. I sent him an email with the photos.

                      Comment


                        #13
                        I received your email Patrick, cheers. Any further action on this chair is on the backburner for the short term as I have a butt tissue issue that is not resolving itself. I suspect a carer with less than reasonable care and attention.


                        Originally posted by Patrick Madsen View Post
                        I think I did edit the post just after and probably tried reattaching a couple of times. It was late and wanted to get it off to S-R. I sent him an email with the photos.

                        Comment


                          #14
                          Oh boy, hate hearing that SR. If it's not healing as expected, get the flap done and save yourself months or years of grief laying down. I think of the years wasted because I didn't want to get laid up for 6 weeks laying down 24/7 in a Clinitron. Once, it got resolved, I haven't had an issue going on 5 years now. I thought laying down for a couple hours a day then up for the rest of the day was okay; it wasn't.

                          First thing is to get a seating eval and proper cushion, what may good for your wife, may be the opposite for you. Rohos are not necessarily the best cushion to use. For me, they were the worst in the eval.

                          Stay strong; you'll get thru this.

                          Comment


                            #15
                            Yes! Injured in 95, I played on the tracks with my butt and though I was better than that.
                            Then, after 17 years, the shit hit the fan: stage IV ischial ulcer.
                            I got the flap surgery and spent 2 months on my back in a Clinitron.
                            Can't imagine how I could do it but it wasn't terrible!

                            Since then I'm a whole lot more careful. Don't want to go through it again.
                            69yo male T12 complete since 1995
                            NW NJ

                            Comment

                            Working...
                            X