Christmas Puzzle?

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PeteThePen1
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Christmas Puzzle?

Post by PeteThePen1 » Tue Dec 14, 2021 10:16 pm

Hi Steamboating Friends Around the Globe

As the Festive Season approaches I thought you might like to apply your inventive skills to help a friend of mine. To be more precise I ought to admit that you would be helping me figure out how to help that friend.

The problem: The friend's sister is thinking about acquiring a 'hand bike' add on to her wheel chair. I am not sure which one, but I will point you towards the Spanish company Batec as my Kath has one and the connection between the chair and the tractor unit is very efficient and low effort. It is probably the best connector in the UK.

This is the Batec Mini 2, a powered hand bike:

Batec Mini 2.png
Batec Mini 2.png (483.29 KiB) Viewed 4894 times

All of these hand bike style machines tend to have two brake levers and both of them operate on the front wheel making front wheel skids very easy. Thus the plan is to use one brake lever to drive brakes on the wheelchair. The simplest way of achieving that is to fit wheelchair wheels with brake hubs of which the best known is probably the Sturmey Archer.

My own experiments in this area show that the brake lever operating the back brakes must be able to pull a lot of cable to actuate two hubs at the same time. The other problem is to get a simple connection between the tractor unit and the wheelchair that the user can operate easily and quickly. We used to use screwed wire cable connectors which were neither easy, quick or possible for Kath to set up from the wheelchair.

One suggestion is to use hydraulic bike brakes but one would presumably need a double size piston in the lever unit. The other issue is how to handle to connection/disconnection of the chair and tractor unit. My scan of bike hydraulics kit makes me feel that there is not too much stuff out there for the DIY person to modify for special projects. Of course there is a whole lot of automotive kit to be had, but I am not sure how one might use it...

Your thoughts would be welcome.

Seasons Greeting to you all.

Pete
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cyberbadger
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Re: Christmas Puzzle?

Post by cyberbadger » Sun Dec 19, 2021 3:47 pm

Pete,

One important question is how much of a conversion are you willing to fabricate yourself or are you wanting an off the shelf medical device that is complete that may just need a little bit of assembly.

One idea that came to mind are ebike conversion kits available from ebay and elsewhere.

If you search ebay for "ebike kit" they sell wheels with a built in hub motor and typically they come with all the electronics one would need.

Some of these kits also include mechanical brake sets.

-CB
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DetroiTug
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Re: Christmas Puzzle?

Post by DetroiTug » Mon Dec 20, 2021 1:03 am

Mount a small master cylinder on the frame of the wheelchair with an actuator lever and quick disconnect for the pull cable. This same lever could have a handle as well to use sans bike attachment. The only way to brake two independent wheels equally is via hydraulics or pneumatic.
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Lopez Mike
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Re: Christmas Puzzle?

Post by Lopez Mike » Tue Dec 21, 2021 6:47 am

I vote for the hydraulic bike brakes on the large wheels. Two master cylinders as per Ron's suggestion. I've used this on ultralight aircraft which are about the same weight as his setup. Maybe more. It's very mature technology. Works fine when wet as well. And amazingly light!

The Sturmey Archer units I've used have been servo boosted internally and don't work worth a hoot rolling backwards. The English produced some amazing technology especially in steam but I'll pass on Lucas electrical and hub bicycle brakes.

Mike
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PeteThePen1
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Re: Christmas Puzzle?

Post by PeteThePen1 » Sun Dec 26, 2021 10:24 pm

Hi Folks

Many thanks for your thoughts.

The aim would be to modify an existing handcycle/wheelchair combination in which all the braking is currently done by two sets of calipers on a single front wheel disc. My Kath has the Batec version with a custom wheelchair (See https://cyclingotherwise.co.uk/index.ph ... hand-bike/). I am not sure what my friend has in mind but they too have a Batec in the family. My friend's brother in law has recently finished building a foundry in the garden so I suspect that there are metal skills to be had probably beyond my amateur efforts. If we can come up with a design I think Kath would be pleased to adopt it for her machine too.

We used to have a chair with drum brakes for which the brakes shoes plate was fixed to the frame and the wheel with the drum could be removed with a Quick Release axle. I have considered Sturmey Archer drum brakes but they are heavy (770g each) and astonishingly expensive but work well enough forwards. I need to do some research to see if other brands are available. I was also wondering about using standard bicycle disc brake hubs and then perhaps designing a QR mechanism for the caliper. If that worked it would make wheel chair wheel removal possible.

Do you have any links to parts suppliers/catalogues for your aviation hydraulics Mike? I have been promised some junked bike hydraulic bits to dismantle and twiddle with just in case there are any off the shelf parts one could re-purpose.

Regards

Pete
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