17 replies to this topic

[HullMedStudent]

Hello again everyone.

A while back I made a post and survey regarding a student project for manual wheelchair propulsion.
After some work me and my group have come up with an idea and have got some initial concept pictures for you to have a look at (they are in preliminary stages so it's a bit rough around the edges and not all features have been added).
If you have the time to give some feedback that would be excellent! (See links below)

Concept Picture 1

Concept Picture 2

Overview of concept:
(The main wheel attachment)
Basically the device clips onto a customised hand-rail that allows a combination of three rollers to slide smoothly.
The main lever is spring loaded and pivoted about the central axis on the housing.
The hand lever is pushed forwards and down (natural motion) and a braking surface on the underside of the rail locks - driving the wheel forwards.
The lever can then be lifted upwards and backwards at the end of a propulsive cycle and slid back to repeat the motion.
(Although they aren't shown there are additional parts which limit the device movement

Any opinions on the appearance, function, etc are greatly appreciated - I'll do my best to clear up any queries about the concept.

Thanks again

Jack

[Tinbasher]

Just some first thoughts.

What are the benefits?

It appears to allow a much shorter propulsion stroke.

it will get in the way when fine manouvering is needed.

Does any benefit outweigh (pun intended) any added weight?

Looks like a finger trap.

Over complex, would a straight lever to a rachet on the hub be any less efficient?

[HullMedStudent]

Hi

The objective of the device is to reduce the amount of effort required in the propulsive stroke - I beleive a lever like movement (opposed to the normal handrail pushing method) require approx. 25% less work to propel. (Can't remember the actual data or sourcing of this at the moment) The vertical handles also require less gripping force as opposed to a handrail.

After some product research into the existing devices just about every hub mounted rachet / chain driven type device has either been patented or developed already - as the aim of the project was to develop something new this wasn't much of an option - so we had attempt to design something that was rail mounted.

The current pictures are of the barebones design currently; should it be developed further there would be consideration into a casing and other features that would eliminate any trapping of clothing or fingers.

In terms of fine manouvering I can see the issue as the device may be a little awkward - however I beleive it is the type of movement that one would become more used to over time.

More work with a few prototypes will allow us to see how the lever angle and length can maximumise the propulsive stroke.

Thanks for the feedback

Jack

[edlee]

One more thing. Braking,, both to stop or slow,, and also for maneuvoring. Once one attains speed on a flat surface,, it is usually slowing one side or the other that provides steering.

Pulling back would have to provide the friction needed,,, but would be a hinderance if it occurred every time you pulled back for the next stroke.

The other thing, was something I imagined when first looking at your concepts,, and that was,,, what it it hung up going down a hill??? If they locked up,, you might launch yourself quire a distance.

I love the basic idea,,, but there is some work left.
ed

[HullMedStudent]

Hi

We've considered the locking of the device - the fulcrum point is spring loaded to ensure the braking surface is not actually in contact with the rim unless force is applied - and two limiters (not shown) stop the device from rolling out of reach when let go.
The braking method is initiated by a downwards motion on the lever and is much like a bike brake (as in it can be applied with variable force) so the desired braking for steering and manouvering on either side can be achieved. The lever is currently at a 2:1 length ratio (Handgrip : braking side) so effectively reduces force required to fully lock.
From your point of view would this be feasible in terms of use?

Thanks again for the feedback - it really helps us look at everything and make the best of the project!

Jack

[davjed]

To me, it looks like an interesting concept that might help those with limited grip. Certainly worthy of further development and testing. Have you tried hooking up with a rehab hospital as a source of suggestions for improvement and a source of testing prototypes.

[xxm]

Your pictures are not accessible in my country. Please upload on another server or send to my e-mail: xxm@vip.bg.

[HullMedStudent]

Davjed - Currently I have not been able to prototype full scale models - I'm limited by the size of our rapid prototyper bed! Should a full scale model be fabricated after further work then we would be trialling at as many places as possible.
Our priority with this project at the moment is to see if a device (in general) can be built and made viable for production at a lower cost than other devices - some are priced (un-powered) much higher than I ever would have imagined (I've seen some at $5000) - it would be great if something that would reduce effort could be made much more inexpensive.
xxm - I have sent you an e-mail with attached images.

Jack

[megatrig]

Hi Jack,

Great to always see people pushing boundaries. I think the best way is to get something up and running to try out.

I've seen similar things to the lever propulsion. I had a quick go. Anything to make "pushing" easier is worth toying around with until it clicks.

Good luck with the development.

[xxm]

Dear Jack,

Thank you for the pictures.

1. I have no grip movement and from my point of view a key point of your project must be developing a hand grip for quads with no finger movements.
2. I see the device as attachable to be used only outside where you don't need fine maneuvers. So it must be fitted to rails that are handy for conventional use - at least for breaking.

I'll be very happy to see the development of your project helping as I can.

Wish you success.

Rudy

[Edinburgh Colin]

 HullMedStudent, on 20 January 2012 - 11:29 AM, said:

some are priced (un-powered) much higher than I ever would have imagined (I've seen some at $5000) - it would be great if something that would reduce effort could be made much more inexpensive.

Jack

You have hit the nail square on the head.
The minute "disabled" comes into play the price rockets! Not sure why, possibly industry collusion and Insurance gouging?
Anyway good luck at getting something to market, making a "reasonable" profit and keeping the sell price down.
EC

[cruiserkb]

I think this a great concept that you are developing.

One sugestion is to posibly make the handle unlock and pivot down so that it is out of the way for transfers. Any obstruction can make the transfer process dificult.

Also is the design for a specific wheel size? I know 24" is about the standard but this could be usefull if it was available for larger sizes.

I am verry interested in this since I compete in 5K,10K and half marathons in a a standard wheelchair. This could posibly elevate me to a full marathon status in a standard chair.

Keep us posted.

[edlee]

I'm trying to picture the braking mechanism. Am I to understand that the brakes are applied at the point at which the lever meets the "limiter"? I can't see how it could be applied,,, by forward pressure on the lever,,,, unless this were the case. It would then be necessary to have a movable limiter,, to account for seating position,, arm length,, preferred length of stroke. Or am I mistaken?
ed

[evilmac64]

i AM READY TO TRY ONE EMAIL ME

[HullMedStudent]

Thanks everyone for the positive feedback!
The method of attachment to a customised rim would mean a range of sizes could be possible.

Edlee - the braking pad that can be seen underneath the rail and upon a forward / downwards motion the pivot brings the braking pad into contact with the underside of the rail - making it interlock / slow down. The limiters would purely be there to stop the device from falling to the ground should they be let go of. The lever position could be altered by an adjustable attachment at the grip handle. I'm looking at the possibility of having an adjustable main lever so the length and stroke length could be altered.

The transfer obstruction might be overcome by an simple 'clip-on' attachment for removal - or perhaps a folding mechanism. I shall look into it.

I will also have to see about the possibility of designing the handle for users with reduced grip - a quick idea maybe a wrist based support?

I'm currently revising and working for exams / reports so the project is on hold for the time being. A 0.4 x scaled prototype with a 'mock' wheelchair has been created using rapid prototyping and sheet aluminium. It's been simplified but it demonstrates the principle - as soon as I get some pictures I'll post them up.

Mac - At this stage a full scale prototype is a long way off - depending upon how and if I can take it further at university.
Thanks again everyone

Jack

Edited by HullMedStudent, 22 January 2012 - 03:45 PM.

[edlee]

Thank you , Jack,, for responding,, because I do see merit, here. As I understand you,, the same mechanism that "locks" the device to the rim to provide the forward movement of the wheel,, is also used to slow down,, instead of pushing down and forward, one would push down,, and hold back.

As for transferring,, you need only provide another limiter to prevent the "arm" from going too far back ( beyond the seat back),, and it would be out of the way in that position.

Be careful of trying to get too much mechanical advantage,, as the more you get,, the slower the speed (forward progress) for each stroke. The advantage of not having to grip the wheel or rim is quite enough.

I should also guess,, that by pushing down and pulling back,, you would be able to go backward enough for fine maneuvering.

Very innovative.
ed

[russ1]

That actually looks really really good - I'm usually one of the first to come on saying seen that! it's been done! it won't work but I'm strugging to see a downside to that attachment which would be great for off road or for when you just want a bot more ommpf! make it so it can be levered off and on easily as it's needed and it'll be awesome, surely for transfer you just let it slide round the rim out of the way?

anyway hope you progress this one

Russ

 HullMedStudent, on 22 January 2012 - 03:38 PM, said:

Thanks everyone for the positive feedback!
The method of attachment to a customised rim would mean a range of sizes could be possible.

Edlee - the braking pad that can be seen underneath the rail and upon a forward / downwards motion the pivot brings the braking pad into contact with the underside of the rail - making it interlock / slow down. The limiters would purely be there to stop the device from falling to the ground should they be let go of. The lever position could be altered by an adjustable attachment at the grip handle. I'm looking at the possibility of having an adjustable main lever so the length and stroke length could be altered.

The transfer obstruction might be overcome by an simple 'clip-on' attachment for removal - or perhaps a folding mechanism. I shall look into it.

I will also have to see about the possibility of designing the handle for users with reduced grip - a quick idea maybe a wrist based support?

I'm currently revising and working for exams / reports so the project is on hold for the time being. A 0.4 x scaled prototype with a 'mock' wheelchair has been created using rapid prototyping and sheet aluminium. It's been simplified but it demonstrates the principle - as soon as I get some pictures I'll post them up.

Mac - At this stage a full scale prototype is a long way off - depending upon how and if I can take it further at university.
Thanks again everyone

Jack

[HullMedStudent]

Prototype

As promised, here is a photo of the first rough prototype,
- Sheet aluminium 'mock' wheelchair with rapid prototyped device at 0.4x scale.

Jack

Edited by HullMedStudent, 24 January 2012 - 11:50 PM.