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.

All of the Wheels are Laced… and a Big “?”

Yesterday, when I got home from work, I was absolutely shattered and didn’t want to do much of anything other than lay down on the sofa and fall asleep, but as I lay there, struggling to keep my eyes open, I glanced over at the mountain wheelchair parts and decided to crack on!

I’m really glad I did as I managed to get all six wheels laced. Ta-da! Six wheels for the mountain wheelchair!

It’s taken quite a lot of modification for the wheel rims to accommodate the spokes. I think they might be motorbike or scooter spokes? By the time I’d finished the fifth and six wheels, I realised I’d done a much better job of these than I had the first and second wheel. With this in mind, I will definitely need to do two wheels again and perhaps even four. Still, I’m really happy with the result and the spokes look like they’re up to the task of transferring the motor torque to the wheels.

As I was tidying up the mess I’d made in my “living room” whilst lacing the wheels, I decided to throw out the boxes that the motors had arrived in. The sense of elation I got just from throwing out some boxes is, in a sense, quite funny. For me though it signified a step forward. No longer are the motors being kept in storage; I’ve actually started building this thing!

The really cool, yet at the same time worrying thing about having all of the wheels made is that in the process, I realised how quick and easy it would be to make a four-wheel-drive platform for testing purposes. Nothing complicated as I don’t want to waste too much time on it, just a plank of wood laid across four wheels would be sufficient. This would at least allow me to see if four of these motors are capable of carrying a heavy bloke like me up a hill. If not, then it will put a huge question mark over the entire Mountain Wheelchair project!

Mountain Wheelchair Bogie Mockup

It’s taken me the best part of the day to filing away so that the motors fit onto the forks, but it’s done, and all six motors are now sitting in the forks. Shoulder aching, I decided to push on and managed to get another wheel laced, then much to Ada’s delight, mocked up part of the frame (a bogie) for the actual Mountain Wheelchair!

The Mountain Wheelchair has its first Wheel

Woohoo! It’s been a busy day in the shop. The spokes FINALLY arrived from China today and I managed to get the first wheel made.

It’s a motorised mountain wheelchair wheel!

Most of the the time was spent with a drill and file trying to get the separate parts to fit together, so although it’s a little bodged at the moment, it’s taken such a long time to get to this point that it feels like an important milestone.

I got Ada to control the throttle for a moment whilst I let the wheel roll on the floor. It’s much faster than it needs to be, but I think that will add to the fun of driving the wheelchair once it’s finished.

As well as the spokes, the “C Washers” which I had laser cut arrived today too and the guys at Microkerf did an excellent job. They’ve been extremely helpful and I’d definitely recommend them:

As I said in a previous post, I can’t be the only person who needs these washers so have listed them on eBay to try and raise some funds for the wheelchair.

Also currently on its way from the USA is a part which I hope will enable me to make the mountain wheelchair radio controlled – useful for testing purposes and driving it on/off trailers etc.

It’s also worth mentioning that Google doesn’t like us at the moment and we’re currently on page 3 for the search terms “mountain wheelchair”, however, on Bing at least, we are the very first result at the top of page 1.

All in all, a successful day! :D

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