The Mountain Wheelchair Climbing My Sofa With Ease

It’s Working!!!!

Yesterday was a very busy day but late last night I gave the mountain wheelchair it’s first test-drive and it climbed up my sofa with complete ease:

Keep in mind that it currently doesn’t have any brakes for the descent, but that’s proof of concept right there!

It’s also drives over car batteries and those boxes containing 5 packs of a A4 printer paper, also with incredible ease, hence putting a sofa in front of it. The rocky path up Snowdon should be a doddle :)

As was to be expected though, not everything worked perfectly; it is incredibly difficult, in fact, it’s virtually impossible, to get the thing to steer. It could in part be due to a problem with one of the motor controllers (One of back motors is currently inoperable). Hopefully I can get that fixed today and then see what happens. It could also be due to a problem with the rocker bogie mechanism but I have implemented a solution to this in the smaller prototypes. Hopefully the same solution can be applied here. Failing that, I’m going to have to completely rethink the steering mechanism.

So on the downside, the steering is a big problem that could potentially take much time, effort and money to resolve (although it could also be a quick fix), but on the plus side, the wheelchair looks completely capable of getting up those rocky steps so often encountered in the mountains.

It’s Starting to Look Like a Mountain Wheelchair!

This is just a very quick post to demonstrate (how excited I am) that progress is being made on the wheelchair frame:

Bits of it are cable-tied together at the moment, and one of my welds isn’t straight so I’ll have to redo that part again, but on the whole it’s starting to take shape. When you sit inside it, the dimensions feel perfect. Likewise, when you stand back and look at somebody else sat inside it, everything looks spot on. And my welds are getting better too:

There isn’t really a great deal that needs to be done before I can take it out for its first test drive.

Building of the Mountain Wheelchair has Commenced

At long last, I finally decided to go ahead and start building the mountain wheelchair frame.

For a long time I’ve been using a computer to create simulations of the wheelchair overcoming obstacles and different types of terrain. Every time I do, I notice something new which is going to create a problem. For this reason, I’ve been extremely reluctant to actually start the build process (in case I decide to revise the design).

Something changed the other day, I guess I felt like I was wasting time and it made more sense to get the thing built and see what happens. So with much trepidation, I cut into the forks:

Having finally cut them, this spurred on a wave of activity and by the end of the day I had built something that was starting to look like a Mountain Wheelchair Rocker Bogie:

Wow! It’s actually coming together! And what’s more, I’m really pleased with how straight everything is and how well all of the angles have turned out. I don’t know what’s going to happen once it’s under load, but so far building the mountain wheelchair is going according to plan.

Learning to TIG weld

Whenever I’m sat at home and I turn on the TV, my first port of call is almost always The Discovery Chanel. Many of their shows feature experienced mechanics running beautiful welds as they build custom cars, bikes and such.

Unlike the splattered messes that I’ve been making with my arc welder, this weld is a thing of beauty:

To achieve welds like this, a process called TIG welding (Tungsten Inert Gas) is used. As far as I know, TIG welding is also the only suitable method for welding alloy (the material which is being used to build the mountain wheelchair frame).

The only problem with this is that TIG is generally considered to be the most difficult welding process to learn.

Last week, Dan from Coastal Welding very kindly gave up some of his time to help set up my welder and get me started with TIG welding.

It was clear from the off that Dan is a very skilled craftsman and he was instantly able to get perfect results. The same couldn’t be said for my efforts:

In amongst all of this mess, there are actually some welds which aren’t too bad. For a brief moment I almost felt like I knew what I was doing :)

Lots more practice required but this a big step towards building the actual frame for the mountain wheelchair.

Lots of Adventures, now back to the Wheelchair

Wow! It’s been over two months since I last updated the mountain wheelchair build log!

Several things have attributed to this. For one, I’ve been busy in work. Also, I bought a Land Rover Defender back in April as a means to get Ada back into the mountains. When I bought the Defender I didn’t realise how much of my time would be taken up trying to keep it running. I’ve had to replace so many parts that it’s almost an entirely different car. It’s been absolutely worth it though because thanks to the Defender I’ve been able to get Ada (and myself) back into the great outdoors.

Thanks to the Defender we don’t have to walk far to get that mountain experience, which is good because Ada still gets very tired and whilst we’re out walking her legs will often give way without any warning.

When this happens it usually means that I have to carry her back to the car. This is not always an easy task and has lead to many improvised carrying devices using whatever is to hand at the time. Accordingly, we try to plan our adventures based on how much we think Ada is able to achieve but this can vary from one day to the next.

That being said though, her health is constantly improving and each month she is able to do more than the last. Having the Defender has, in my opinion, had a huge influence on this! It’s made getting outdoors much easier and spurred us on from one adventure to the next:

As I proof-read this post, it’s great to see so many photos of Ada smiling again!

Last week Ada did the biggest walk (6km) since being diagnosed with M.E. Compared to where we were this time last year, this is such an enormous change. It was only in December that we had tears of Joy when Ada was able to stand on her own two legs again.

We’ve even done some multi-pitch climbing!

Ada’s happy, she’s enjoying life, and that has always been the driving force behind the mountain wheelchair project. Having achieved that goal, where does this leave the mountain wheelchair?

We have been so incredibly lucky to see continued improvements but this isn’t the case for everybody. There are so many other people who could benefit from the wheelchair that it would be doing a tremendous disservice to discontinue the build. So with this in mind, watch this space…

All Six Motors for the Mountain Wheelchair are Working

There were a couple of tasks that had been causing me a bit of a mental block and preventing progress with the mountain wheelchair so it’s really pleasing to have them ‘done and dusted’ so that I can get back to it.

One task was to disassemble all of the wheels, make some modifications and then reassemble them all. Having done this, all of the spokes in the wheel rims are sitting far better than they were before.

The other task was to change and re-wire the connectors on all of the controllers and motors. Having done this, I could finally go ahead and get all six motors wired up:

As Ada said in the video, there are many things which need doing in terms of wiring for the wheelchair, but it is an enormous relief to see all six motors turning and relieve myself of the concerns I’d been having. It shouldn’t be long now before I start building the rocker-bogie for the wheelchair frame…

Words of Encouragement for the Mountain Wheelchair

As I’ve said many times before, my engineering background is extremely limited, yet this mountain wheelchair project demands experience in a wide range of engineering disciplines. As such, I have needed to spend considerable time in online forums seeking advice from people with more experience than myself. The forums, and the advice received, have been instrumental and I would not have been able to get this far without them. That being said, at times, some of the feedback I’ve received has been a little disheartening. For example:

“I don’t think I would let my daughter climb up a path like that in a vehicle on wheels and especially knowing she would need to roll down again”.

“Are you really planning on letting your daughter descent those steep parts on 6 bicycle disk brakes all the way down?  That will be a workshop with a ‘steep’ learning curve in down hill biking”.

“The more I think this through the more I dislike the idea. Especially as you don’t seem to be very knowledgeable in this area (neither am I BTW) so it looks like this might end in tears. Please rethink this challenge and don’t risk your daughters health or worse with what seems a noble cause”.

Whilst I’m able to shrug these comments off with what might be considered determined ignorance, Ada on the other hand hasn’t yet developed this skill and comments like this have somewhat diminished her sense of hope in the project.

Although these comments have no impact on my desire to keep pushing on,  I have of late been coming home from work completely exhausted and finding it difficult to keep working on the wheelchair.

To try and reduce my workload, I had been questioning how useful this blog is. I mean, who actually reads it anyway?  Less time blogging means more time for building right?

As chance would have it, just as thoughts of discontinuing the blog were starting to run through my mind, in quick succession we received a number of messages through our Facebook page. For example:

“I am watching what you are achieving with great interest”.

“I love reading your site. Keep it up! I’m 33 now and have grown up in a wheelchair my whole life. There is nothing I haven’t been able to do with a little bit of planning, effort and engineering”.

“I used to be a fell runner and miss getting out on the hills […] This wheelchair would give me the opportunity to get out and explore and enjoy the off beat track again. I want this chair! I love the design it is so upbeat and mountain cracking!”.

“Good luck with everything you are both inspirational”.

On top of this, in the very same week, I was sat at my desk in work when a colleague came in brandishing an envelope which she suspected belonged to me. I didn’t know of any other G Davidson in the college so I proceeded to open it. I was absolutely gobsmacked when I did! It was a letter of encouragement from the Welsh Assembly! The letter reads;

“Dear Mr and Miss Davidson, I am writing to congratulate you both on your inspiring ambition to create a specialised mountain wheelchair in order to continue your adventurous outdoor exploits.

I understand that Myalgic Encephalomyelities, or ME, can make it very difficult to continue pursuing a variety of activities, particularly as the models of mobility aids available are not designed for the rich and wild terrains that we have in [North Wales]. Therefore, your determination to continue pursuing the activities you enjoy, and think creatively to solve these problems is especially commendable, and should be a model for us all.

With all the hard work and gritty determination that you have both shown, I have every confidence that you will fulfil your ambition to reach the top of Snowdon, and i hope you take the time to reflect on your journey there when you do.”

The kind words both from the assembly member and from the followers on Facebook offered an immense boost in motivation and I’d like to thank you all for taking the time to write to us. It couldn’t have come at a better time for me and has given me the impetus to keep the blog going. When Ada read the messages her face lit up, then she walked away doing a little dance with a smug look look on her face :)

Whilst I’m here, I’d also like to say thank you to one person on Facebook who consistently shares all of my posts and helps to encourage interest in the mountain wheelchair project. If you’re reading this Mervyn, then thank you, your support is deeply appreciated.

What’s Next?

It’s Friday today and in a few hours the college will be breaking up for Easter. Hopefully this means a short break for myself to recharge my batteries and then it’s back to building the mountain wheelchair with renewed focus and fewer distractions. Lots of parts and tools have arrived from overseas so hopefully I’ll be able to make substantial progress. Watch this space…

Working Radio Controls for the Mountain Wheelchair

At long last I managed to get the radio controls for the Mountain Wheelchair to work!

It’s taken so much and time and effort to get this to work. Not wanting to get too technical, I basically needed a way to convert an RC Receiver 1-2milisecond pulse to an analogue 0-5volts. I tried all sorts! In the end I found a very elegant, simple and cost effective solution from an American company called Astro Flight. There were some issues with the shipping but once the item arrived it was a very simple plug-and-play and at last, the mountain wheelchair has a working radio control system.

As I’ve said before, it was extremely important to get this working because it will allow me to drive the wheelchair into the mountains without needing to be concerned for the safety of the driver.

The Mountain Wheelchair Project now has a Tube Bender

At long last, I now have a Tube Bender! This means that I can actually start fabricating the frame for the Mountain Wheelchair!

There were lots of tube benders to choose from, all of which were beyond on my budget, that is until I found this. This “Affordable Bender” came all the way from America, complete with dies to bend the two sizes of alloy tube I intend to use, and all for approx £500. Considering that the dies alone usually cost about £400, this was an absolute bargain!

I don’t expect this to last a lifetime, or to be able to produce complex bends, but it should be sufficient to get at least one Mountain Wheelchair built. In fact, given what I paid for it, I’m rather impressed with the performance. It produces smooth bends without kinks and is quite easy to operate. I’ve also been pleasantly surprised at how well the alloy tube copes with being bent. According to what I’ve read, alloy has a tendency to snap rather than bend. So all in all, it’s looking positive for the wheelchair.

The Mountain Wheelchair Braking System

Most of my time of late has been spent working on the electronics for the mountain wheelchair and more recently building the wheels, however, I have, for some time now, been thinking about the brakes…

When testing the smaller prototypes for the mountain wheelchair, I discovered that:

“When [the mountain wheelchair is] overcoming obstacles such as large steps, the front wheels are pushed into the step and with the traction created with all six wheels, the front wheels ‘drive’ up the step. The problem is that the front wheels don’t always get traction [and sometimes just wheel-spin, or even worse, get stuck]”.

To prevent this from happening, I had been thinking about using hydraulics or linear actuators to lift the front wheels off the ground before approaching the obstacle. A far simpler method is just to use the motors and brakes which are already on the wheelchair therefore requiring very few additional parts and reducing the overall weight of the wheelchair.

To demonstrate this; if you were to apply power to the front and middle wheels, whilst at the same time applying the brakes to the rear wheels, then the front wheels would lift off the ground resulting in an increased possibility to overcome large steps. Like so:

This seems incredibly easy to achieve from an engineering point of view, the problem is making it easy for the driver of the wheelchair to operate. If you only had rear brakes, then the wheelchair would skid under braking, so you need brakes on all wheels.

As I’m planning to use hydraulic disc brakes off a mountain bike, this does present some problems. These brakes usually have one brake lever for each brake caliper. For a six-wheel-drive wheelchair requiring six brakes, having six brake levers, I think, would be difficult to operate.

I have however found this hydraulic hose splitter made by Hope Tech. If I were to use these, then I could theoretically operate three brakes from one lever (one lever for the left, and one for the right). This way you could skid-steer the wheelchair down a mountain just by operating the left or right brakes.

If you have one lever to operate the three brakes on one side of the wheelchair, and another lever for the three brakes on the opposite side, how then do you apply the brakes to the rear wheels only? With a solenoid valve on the hydraulic lines which feed the front brakes perhaps?

At the flick of a switch, maybe a thumb operated switch on the top of the joystick, a solenoid valve would close, thus prevent the hydraulic fluid from reaching the front brakes. To help illustrate this, I made this (very) rough sketch:

As you can see in the sketch, I plan to have the brake lever upside down and mounted to the joystick levers (You can see this more clearly here). For testing purposes, I made this:

As an aside, the picture above shows a disc brake on one of the motors. This is a very cheap disc brake that I found in the back of my shed, it’s about 20 years old and the pads are worn down. It does at least allow me to do some testing; if I squeeze the brake lever as hard as I can, the motor still has sufficient torque to keep turning. I’ve run the motor like this for five minutes trying to get it to overheat in order to test the thermal protection mechanism which I installed. After five minutes the disc brake was almost glowing hot and smoking, but the motor showed no signs of warming up. A positive outcome.

Anyway, back to the topic at hand…

Hydraulic brakes on a mountain bike have a reservoir built into the lever to hold the hydraulic fluid. When you squeeze the brake lever, the pressure moves the fluid from the reservoir to the brake calipers, thus forcing them to close. This is great, except that the levers are designed to operate one caliper only, not three. Actually, and this is where the gaps in my experience of engineering start to appear again, I’m not sure that it’s the reservoir that causes the problem, but rather the levers don’t create enough pressure to operate multiple calipers?

I spoke to Hope Tech and they’ve reassured me that their “Tech 3 Lever” will operate two of their “X2 calipers”, but not three. This is great for two reasons..

First of all, they both come in purple, so this will make Ada happy:

Perhaps more importantly though, I think it might be better not to have brakes on the front wheels and I’ve made this video to help illustrate why. The video represents the wheelchair rolling down a hill and then applying the front brakes. As you watch the video, imagine what would happen next.

Just like on a mountain bike, it would want to “throw you over the handle bars”. On the mountain wheelchair this effect is amplified because of the rocker-bogie suspension mechanism. In the video, it’s easy to imagine how the centre of gravity moves to the front of the wheelchair and would result in quite a nasty accident with the full weight of the wheelchair, its heavy motors, batteries and frame coming down on top of you.

Ultimately, I think this is going to be a trial and error thing during which time there are some other ideas which are worth exploring.

It would still be possible to have brakes on all six wheels, it would just have to be setup so that there wasn’t much braking force at the front wheels.

As well as this, the motors in the wheels have some resistance anyway; they act as generators which recharge the batteries. I plan to have a “knob” near the joysticks which lets the rider adjust how much regeneration the motors are doing. In effect, this  dial would adjust the rolling resistance of the wheels. In this regard, perhaps brakes aren’t needed on the front wheels?

Perhaps the best solution though would be to replicate what happens on a bicycle. i.e. have one lever for the front brakes and one for the rear. This would give the rider complete control of the braking balance between front and rear wheels. In fact, this would then remove the need for the solenoid valve. To lift the front wheels off the ground, you would just have to squeeze the left brake lever (which would operate the rear brakes) and drive forwards. Far simpler than having to operate switches as well as brake and drive at the same time and for people who previously were passionate cyclists, this setup might be more familiar to them. The only problem with this is that it removes the ability to steer the wheelchair by operating the brakes. As I say, I think this is largely going to be trial and error.

This page was last updated on April 18th, 2018 by .
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