Hi Eric,
Are you sure about the 200 pound limit? According to my favorite bicycle wheel book ever, aptly named, _Bicycle Wheel_ by Jobst Brandt,
If its spokes are tensioned to 1000 N, a 36-spoke wheel will support approxi- mately 400 kg. This is considerably greater than the average rider's weight. However, loads of 400 kg or more sometimes occur when a wheel strikes a bump in the road at high speed. If such overloads occur often, the nipples of slack spokes can unscrew, reducing tension to affect both wheel alignment and strength. Although radial overloads rarely cause wheel collapse, they can make the wheel lose alignment.
Wheels are crazy strong radially, but not so much laterally (lateral strength is only about one-tenth of a wheels radial strength according to Jobst), however, for this application, I don't think lateral strength would be much of a factor.
This is a tall task, in fact, the commercial bike walkers I have seen so far don't support the weight requirement, including the one sent by Rebecca, and an Angel (called York) with an intriguing tricycle design - https://youtube.com/shorts/QOa7C-Vx790?si=3b5_3w2BmMXfE63K ( https://www.thealinker.com/pages/faq )
We used to receive adaptive bikes out of warranty from https://www.varietypittsburgh.org/my-bike/overview/ , but I don't think these bikes would work for the application either.
Keep sending those ideas, I am loving the thinking going on.
-Jonathan
On 2024-07-04 08:02, eric--- via TheThinkTank wrote:
Hello Fellow Community Bike Shop Folks,
This is an interesting project and something that all of us have a certain amount of skills to build. However it is a bit of a tall task for all of us. One concern is this situation is for a medically critical patient. Also the weight limit required for this patient is very high. Weight limits for most common wheels is probably around 200 pounds each.
We all are used to solving issues recognize our limits.
Eric Brozell Erie Bike Recyclery/Pedal Mettle
On Jul 4, 2024, at 2:46 AM, Yate Community Bike Hub via TheThinkTank thethinktank@lists.bikecollectives.org wrote:
The description reminded me a little of this sort of walking bike mobility aid, which are not very common here but the people I have seen with them have raved about how good they are.
https://www.vanraam.com/en-gb/our-bikes/walking-aid/cityI wish the OP the very best and hope that a clever solution can be built. Would love to see the end product if you have chance to share back to the list.
Love, peace and bicycle grease, Rebecca
Rebecca Bennett (she/her) Co-Director, Yate Community Bike Hub CIC
_Find out more at:_ www.yatecommunitybikehub.co.uk [1] _You can find all our links, including our socials, on_ linktree [2]
On Tue, 2 Jul 2024 at 07:04, Jonathan Rosenbaum via TheThinkTank thethinktank@lists.bikecollectives.org wrote:
Our collective, Positive Spin, has received the request below. I know there are some members with good fabrication experience on this list. Has anyone worked on a similar project, have design plans that would fit these specifications, or advice on how to proceed?
Greetings:
I'm writing to you in hopes that you might be able to literally help me save my life. Between some bad genetics and acquired injuries I'm currently not able to walk in any meaningful way. Some little bit during physical therapy. I've lost significant muscle mass and things are getting worse.
I'm a tall person 201cm (6'7") before the accident wherein my spine suffered a compression injury I'm now 196cm (6'5"). This injury also caused lymphedema in both legs so my weight can vary by hundreds of pounds from 165kg -320kg (360# -700#). Walking and bicycling helps control the lymphedema immensely.
I've given much thought to what I need and what I want. A doctor friend asked me what I was wanting and I'm going to incorporate my response to him in this letter as I believe it provides a very good idea of what I'm wanting and a bicycle repair shop would be just the place to make this happen.
Upfront I'm not currently working I'm on a fixed disability income so I need to keep costs as low as possible; on the other hand we are talking about regaining my life versus dying slowly so I'll find a way to meet the financial requirements to make this happen.
What I want to build: I want to build a walker. Because of my injuries and loss of muscle mass a traditional walker can't be used and a wheelchair or powerscooter won't help me walk again or build muscle mass.
Kind of a side by side bicycle with step through (girls) frame, 4 wheels (two in front and two rear) but relatively close together (like a wheelchair it needs to fit through doors). A bench seat is preferred but if I must use a bicycle seat I'm going to get a Hobson Pro. Either way the seat will need to be low enough as to be out of the way when walking but there should a my hip or back fail and I drop. Needs to be high enough that I can continue to "walk" even while seated. I also want front and rear brakes as this is WV and we have steep hills. I want some method of locking the wheels so the walker won't roll about while I'm mounting or dismounting. Some place to carry my crutches would be great as would a cargo area (basket, underseat???) and water bottle cage (couple 2 liter bottles). I'm thinking BMX sized fat tires (idk 16" - 20") so I can go in the grass as well as sidewalks and buildings. I believe at its widest it should be no more than 32" and likely no longer than 54",
maybe less, as it will also need to fit into elevators and exam rooms.
That step through frame will need to be narrow to accommodate a normal leg spread with normal gait and stride (may require a bit of tube [frame] bending or cutting and welding). It will also need to be quite strong to accommodate my weight and my falling weight should my hip or back fail and I take an uncontrolled seat. An alternative to the narrow central frame might be a frame that I stand between. My illustration shows both ideas. Speaking from an engineering stand point I've no idea which would be stronger. To be honest one luxury option I'd like to be able to put on it would be the ability to turn the seat sideways so I could cook at a stove or work in my garden or in my workshop.
This walker would immediately release me from the forced captivity in which I'm trapped. Help me regain muscle mass. Help me recover my physical health. Do activities I love and miss and it could even get me back to work.
I most sincerely hope that you are willing and able to help.
Thank you,
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[1] http://www.yatecommunitybikehub.co.uk/ [2] https://linktr.ee/ycbh