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whburling 07-19-18 06:47 PM

Revising wheel chair with though axle bicycle wheels
Hi,I am interested in modifying the wheel chair of a friend. He has been wheel chair bound since 15 and now is 63. He is still a kid, however, wheeling all over the parking lot in the early morning hours. Speed is one of his things. Rain or shine. His wheel chair is cheap as hell. I hate it. . But he loves it. Will not consider a new chair. So when the bearings failed for the second time of a chair 3 years old, I gave the design a good look. The basic design is that a bolt is cantilevered from a nut welded to the chair frame. The bearings are a very loose slip fit on the bolt. The bearings are more tightly fit into the plastic hub. The bolt head applies a force to the inner race of the outer bearing. That force is then supposed to pass through the inner race of the outer bearing through the hub to the inner race of the inner bearing to a collar welded to the chair frame. But I don’t think that happens. I think the bolt force passes through the inner race of the outer bearing through the balls through the outer race of the outer bearing through the hub to the outer race of the inner bearing through the balls to the inner race of the inner bearings to the chair collar. If that is true the bearings would be subject to shear which could be an explanation for the degraded bearings.The fix is to create a sleeve placed between the inner races of the two bearings so that the bolt force passes through the outer bearing inner race through the sleeve to the inner race of the inner bearing to the chair collar sized to press against the inner race only.To make it more simple, I designed an axle with the sleeve integral to the axle. I was quoted $50.00 an axle by the local machine shop. But then I realized that I was caught with a wheel whose manufacture is unknown. what happens when the wheel rubber wears too thin. So I began to consider adopting a bicycle wheel with a solid through axle. A 5/8” axle would work perfectly. It has a handle on it which looks like a quick release lever. But it is not. The lever is used to unscrew the axle from a threaded bolt just like in the wheel chair. So I am wondering if others have actually adapted their wheel chair design to use these axles. I will gladly listen to all experience. Secondly I need to attach some sort of rim used to propel the wheel chair. Does anyone have any ideas how to do that. If I use a road bike rim, there is little rim to attache the propelling ring. So I was thinking of attaching the ring to the spokes close to the rim. Any ideas are welcome.



CliffordK 07-19-18 07:33 PM

I have thought about using through axle hubs for trailers. I think they come up to about 3/4" (19mm) or so which would be mighty stout.

Another option to consider is a "Lefty" hub used on some of the new MTBs, which is designed specifically for one sided mounting.

As far as the rim, if you're relacing, then you could easily relace onto the wheel chair rim.

Another thing to look at would be cheap fixie rims. They frequently have a deep wall aluminum rim that would give you quite a bit of space to add your driving wheel mount.

Are you using 700c?
Is this a standard chair, or a racing wheelchair?

UniChris 07-20-18 02:46 PM

Wheelchair section of the Schwalbe catalog is interesting - also started a youtube adventure on the exploits of Aaron Fotherinham who does flips and rail grinds in his.

Seems like 559 is one size of bike overlap.

It you can split the problem into hub & bearings, rim with a common bike BSD that already has the hand rail, and a bike source tire, then provided you're willing to build wheels (fun learning project, took a long evening) then there could be a fair degree of supply independence and maintainability?

Have you determined current rim BSD is not a common size with multiple tire suppliers? If it is, maybe you can save the rim, and just replace the hub. Custom length spokes should not be any great issue or expense to source as long as they're less then about 300mm, and there are calculators online that work if you have accurate rim and flange measurements.

fietsbob 07-22-18 12:43 PM

there are pins which use a ball in them as a safety catch

larger ones can be operated by pushing a button,
that releases the force pushing the ball out, allowing the pin be removed

Quickie wheel chair hubs use that same principle

so you will be, literally, re inventing the wheel..


whburling 07-23-18 06:55 AM

Thank you for your ideas and time to convey them to me. Much appreciated. Help me.....what does MTB mean?
Do you know where I can look on the web for wheel chair rims?
I did find a few suppliers but i wondered if you knew of some as well. Maybe your selection will give me greater opportunitites
thank you again,

whburling 07-23-18 07:02 AM

700 cc wow......i think my friend is more like 1500cc. he is a tiny guy but strong physically and in heart. His music, by the way, is incredible.
He comes from coal mining territory....and it seems to pervade his music like coal dust penetrates the homes of the region.

His chair is a cheapo. You know....made on Mars. heavy as hell. Frame overdone as if a 300 pound person was the user. armrests. Not like the
chairs I see on YouTube with the gals talking about features they like. I love their reasoning. I love their chairs. I am 73. When I am 93 and in a chair I know exactly which chair I am getting. One of their's. So to answer your question, the chair is not designed for racing, but my friend would win any race if he enterred. He may be 63 but he is in shape and a fierce competitor under that placid facade of his.

whburling 07-23-18 07:08 AM

Thank you for your excellent ideas, references, and willingness to help another person out.

I did not know about that is a great first step.

I am definitely going to check out the exploits of Aaron Fotherinham. I love how he is not letting his
disability get in the way of doing stuff I would not even consider doing. I think that is why i loved the
girls on Youtube who have movies about features they liked. It was apparent that they did not treat
their disability as a disability. It just means they have to find ways of coping in this world in a different
manner than other people. we all have to cope. We are all "disabled" in some way.

This message box is in the way so i need to send this one, read the part of your message that I can not see and then respond to you once again.
pardon the interrupt.

whburling 07-23-18 07:36 AM

sorry about that....i was logged off!

ok...took notes so I can respond to the rest of your letter.

what does 559 mean?

I love how you split the problem up. Awesome. I need to do that more in my life, at least in my mind. I am not sure if my wife would apprecaite, "Now Honey, lets split this discussion into parts so we can better handle it". That attitude might work with some people, but not for others :)

In addition to splitting up problems, another good problem solving approach is to break the solution into versions. My friend suggested that as he is getting tired of waiting for a fixed wheel chair. So my first version is to just get a set of good bearings into his existing wheel. The second version I will create (oh I feel like a roman God) a wheel out of parts.

Yes....Eventually I got on the binge of checking out every bicycle wheel component. Rims, spokes, hubs, bearings,axles, and wheel chair components that
the mfr used to connect wheel to chair. (nut or bushing...the two predominant choices).

I started with the bearings as I wanted my friend to try out the design and come back to me with a jaw dropped in awe. That is my hoped for payback. I know, I know, no strings attached when giving. the price range is from 6.00 to 100 plus per bearing. I chose ceramic hybrid technology. I chose Boca as the manufacture only because their site gave me the opportunity to sort out types of bearings more readily. They do have a decent reputation, which helps. I chose a bearing which would fit into his existing chair as nearly as possible. Only the outside dimensions were important for that as I am designing the axle (which defines the inside dimension)
I chose the Ultra Seal Ceramic. 32 mm OD, 15 mm ID and 9mm thick. because I am designing the axle, I can avoid having to purchase ea bearing with a flange (original manufacture design required one). I chose that bearing over the Yellow Seal Ceramic as the Ultra Seal Ceramic has a non contact seal. The Yellow had a more robust seal but it is a "contact" seal and I wanted my friend's jaw to D-R-O-P.

The hub is another animal. I am beginning to realize I had better write about my findings in another note. You guys might already be sleeping.

Oh (looking at my notes of your reply) friends dirt cheap wheel chair has dirt cheap plastic wheels (no spokes) with plastic hubs with poor design.

whburling 07-23-18 08:14 AM

Thank you for your excellent suggestions and references.

It took me awhile to realize there are predominately three types of axles.
(1) Thread on axle which requires a bushing and nut attached to the chair. In the past, this axle required tools to put on and take off.
A revamped version of the above is the standard for off road bicylces. It is called a Thru Axle. Instead of having a bolt head which requires a wrench, the
design has an integral handle which allows one to screw the axle into and out of the nut attached to the chair. The advantages of this approach is
that the solid axle is strong and the connection to the wheel chair very solid. Disadvantages are that removal and attachment requires more effort and bearing
replacement requires special tools.

(2) Quick Release (wheel chair design).....which is the axle you described. A hollow shaft with balls or pins that prevent the wheel from coming off.
Various methods (rods or wires) permit the locking balls or pins to retract into the hollow shaft allowing the wheel to easily come off. This approach requires
NO nut on the wheelchair. Only a bushing. Its advantage is ease of wheel removal or attachment. The drawback is that the inner race is not press fit onto the
axle and hence the wheel can sometimes turn on the axle and not on its inner race.

(3) Quick Release (bicycle design). This design can not be easily cantilevered as the rear wheels on wheel chairs are. The axles are hollow. a small diameter rod
tightens up clamps on both sides of the wheel hub clamping the wheel to the the bike fork. its advantage is light weight and the ability to use open bearings
which permit balls, inner race, and outer race to be separately maintained and replaced. I mention this approach as it is the current standard for road (not off
road) bikes and could be adapted for use on wheelchairs.

I favor the Thru Axle for my friend. He does not have a need to remove his wheels and wants to go fast. In that case, I want his wheels to rotate on the bearing
races. I believe, that wheel chair users give up the performance of a bearing for wheel removal convenience. I believe tthey could have better performance if they
had press fit bearings instead of the slip on fit they use. I may be wrong. I have been wrong many many times in my life. But I would like to point out that in most
mechanical designs incorporating bearings, both inner and outer races have interference fits intended to guarantee rotation takes place IN the bearing and NOT on
the axle. Have you ever wondered whey so many Quick Release axles are sold? Maybe the bearings gawl the axle? I have no idea.

UniChris 07-23-18 03:14 PM

Originally Posted by whburling (Post 20463992)
what does 559 mean?

This project would probably be helped along a lot if you did some background reading on bicycle wheels - Sheldon Brown, Jobst Brandt, etc...

I started with the bearings...I chose ceramic hybrid technology.
Enthusiasm is a great thing, but for a functional prototype, conventional steel bearings are probably going to be a lot cheaper and easier to work with... it's almost inevitable you'll be ruining some components while getting the ideas sorted out, so pick basic, proven, rugged ones where you can afford to make mistakes.

A wheelchair doesn't sound like a performance vehicle, but maintainability with widely available components would be great. It happens for example that entry level unicycles use a bearing size that's standard in snowmobiles.

CliffordK 07-23-18 03:32 PM

How many wheels have you built in the past?

It involves more than just inserting spokes in a hub and rim. Not an insurmountable task for a beginner, but it takes work and patience, more than just researching the perfect parts.

Browse through the tire sizing information:
Tire Sizing Systems

MTB is an abbreviation for mountain bikes... a bit more stout than the typical road bikes.

Bicycle wheel sizes basically have two ratings, the outside diameter of the tire, and the rim diameter.

So, a typical road bike wheel will be 700c (about 700mm overall diameter), on a 622 mm bead seat diameter rim. With different tire size designations, that same 622 BSD rim can mount 700c, 28", or 29" tires.

26" mountain bike wheels use a 559 BSD rim.

Some of the common wheelchair rim sizes are different from bicycle rim sizes. That may or may not be an issue for your build, but you may choose to start with the proper sized wheel.

Racing wheelchairs can also be unique.

squirtdad 07-23-18 04:41 PM

OP, get your post count up to 10 and post a pic of the wheelchair. It would also help to have the brand and some wheel measurements.

79pmooney 07-23-18 05:13 PM

Two cautions (from someone who spent real time observing and talking to wheelchair users as well as looking at the wheels from a design point (25 years ago and standards have changed a lot).

One - don't have anything that extends beyond the plane of the outside edge of the tires, handrim and hub your friend is now using. Not one mm. If you do, it will take paint off or do more damage to doors and furniture (or break). Wheelchair users come to know their chairs like we know our bodies. They also adapt either their chair or their surroundings to fit each other. Put a slightly wider wheel on a chair that was custom made to just get into the bathroom of his house and trust me, you will be off his favorites' list very fast. (Custom doorway for a stock chair - same issue.)

Second, consider that wheelchair tires are made with rubbers that don't leave skid marks. Adopting bicycle wheels and tires will make you very unpopular with those who have spent good money for immaculate floors. (I second Clifford's idea of getting the bike hub right, then lacing on a wheelchair rim.)


79pmooney 07-23-18 05:30 PM

whburling, two reasons to go with a standard wheelchair quick-release system. One, they work. The axle is hardly going to spin, It is a cantilever with half the weight of the user plus chair sitting 3" beyond the end of the sleeve. (If it does spin, those "bearings" are in desperate need of service or replacing.) Second, with a standard QR wheel, your friend can go to any pharmacy and get a replacement. (He may have to send a clueless friend since once one of his wheels dies, he is going nowhere.)


CliffordK 07-23-18 06:29 PM

Originally Posted by 79pmooney (Post 20465306)
One - don't have anything that extends beyond the plane of the outside edge of the tires, handrim and hub your friend is now using. Not one mm. If you do, it will take paint off or do more damage to doors and furniture (or break).

Oh, I can just imagine little hub notches ground out of every doorway, public, private, wherever he goes. :innocent:

I wonder if that is a reason that many wheelchairs have angled wheels, so at least if the bottom part of the wheel goes through, it will push the chair over a little bit.

There are narrow front hubs, 70mm, 74mm, & 79mm, although I'm not sure about through axles.

However, in a sense, any sealed bearing hub could support a custom axle.

Wheels can be dished to the outside. Burley used to do that on many of their bike trailers.

Of course, that is a skill for someone who has built a few front and rear bicycle wheels already.

CliffordK 07-23-18 06:31 PM

Another thing I'd do.. measure the target wheelchair, then start prowling local thrift stores, and classifieds for a good donor chair.

It is often cheaper to buy something whole and strip it than buying all new parts.

squirtdad 07-24-18 10:18 AM

On reflection I think there is a whole lot of re inventing the wheel, so to speak, that may not be needed

just looking on the web you can get wheel chair specific parts and chairs of various prices, qualties

your can get clearance wheel chairs pretty cheap Manual Standard Wheelchairs - Standard Wheelchairs - Wheelchair Parts.Net

same place has bearings, wheels, axels etc.
Wheelchair Bearings at
Rear Wheel Axles for Manual Wheelchairs
Rear Wheelchair Wheels

sun rim wheels Rear Wheels - Sun Spoke Rims - Wheelchair Parts.Net

easy to just replace a bearing

fietsbob 07-24-18 11:51 AM

Note you see wheelchairs made in all sorts of configurations for competitive sports

At the LBS a couple years ago a customer
wanted to get rid of the institutional never go flat foam rubber innertube
and put a regular pneumatic tube in it .

Asking the medical supply shop down the street they said we ship them out to change tires

A machine like the car tires get installed with may be there..

so we cut up the tire and that rubber ring..

the wheel and hand ring were a one piece thing,

Skyway one manufacturer of that sort of thing, molded in Fiberglass filled Nylon..


CliffordK 07-24-18 12:01 PM

Something like tubes vs tubeless would be an issue with the person's overall mobility.

Imagine what it is like to fix a flat on a bicycle. Then for the wheel chair, hop out of the seat, and work on one's wheelchair tire, then hop back in.

Tannus makes reasonably good quality solid rubber bicycle tires. I don't know about wheelchair specific sizes, but perhaps they would be similar. A pain to mount, but they last a good long time once mounted.

Of course, racers likely worry about small efficiency differences, just like many cyclists.

unterhausen 07-25-18 02:29 PM

a TA isn't really appropriate for this application. If you really wanted to make it into a project, a lefty hub is the place to start. I know Phil Wood makes wheelchair hubs if you want something really nice. I see them for less than $250.

79pmooney 08-01-18 08:59 AM

Originally Posted by CliffordK (Post 20465433)

I wonder if that is a reason that many wheelchairs have angled wheels, so at least if the bottom part of the wheel goes through, it will push the chair over a little bit.


The angled wheels are to improve ergo dynamics. The more angle, the better the hand motion on the wheel lines up with your shoulder muscles. But that angling has the drawback of widening the chair so serious uses often have several chairs so they can use the widest, most angled wheeled chair that works in the environment they will be in. Typically, they need narrower chairs to go to work. A lawyer working n an old building might have a very narrow chair built to just fit through the narrowest door and a nice comfortable, wide chair for his home that is designed for good wheelchair accessibility.


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