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Off road Quad Bike wheels and tyresAn Off Road Power COMPACT Wheelchair with a difference. MK2 version

Part 1 Strip & modify Mk2  1 | 2 | 3

Mk1 | Mk2 | Mk3 versions + Timeline

A completely re-designed & better built powerchair, that is at home walking the dog in the woods in winter as it is in my Van or my Home. For around 1500 to 1700 UK Pounds...    3 pages.


The Original ultimate powerchair project should be read first.  Much of the reasoning and method behind everything is on that page (actually 6) and was completed last month.  Detailed PowerChair Only Menu

the ultimate do everything power wheelchairHow it looks so far! This off road electric powerchair is an ongoing  documented almost daily build...  Finished >>>

A narrow 25.25 inches (640mm) wide at the widest point with 18 inch cushion and 40 inches (1000mm) long including the deep footplate. And seat height variable from 16 inches high!  Currently 18  cushion. That's smaller than many manual powerchairs. And almost all power wheelchairs. And it is all day, very manoeuvrable with no "corners" (casters or swing away footrests) at the rear And it uses full size group 24 75ah batteries and 6mph!

I would just buy an off road power wheelchair but build quality, finish and size issues means you simply can't. So as usual I will just do it myself.                       Powerchair off road  (Under construction)

Because I want an off road chair that I can use all day every day for everything from walking the dog in the woods to driving my van to going to the pub. And no such chair exists. They are all too big.

Even the almost correct Frontier X5 here is a fraction too wide and has a few other problems for my use.

This new page details the quite involved modifications
That allows big fat balloon "off road" tyres and wheels to be fitted in addition to all the other modifications on my other two daily powerchairs here

Reason?  Well they look cool!  And because they are balloon type tyres with big fat sidewalls the ride on our pavements is much nicer!  My spine no longer suffers. They also don't mind mud and grass or sand.

I walk my German Shepherd dog about 5 to 7 miles a day. On grass, forest paths and in the winter. These tyres are opposite to the "Stiletto heel" or a normal powerchair. 

They don't damage surfaces as much either. But the don't sink in soft ground! And they grip! And they are tubeless with the multitude of advantages that gives including much better puncture resistance. And 4 ply construction... (see previous MK1 page!)

This is a completely new powerchair build, still using an ancient old donor powerchair (another Sunrise F55s) although much less detail will be shown regarding much of the build since that's already been done previously here. You should read this first. Most of the bits that are different will be covered in detail should you be daft enough to want to do this yourself.  The other chair was just a simple bedroom build job. This one needs a bit more fabrication although still massively cheaper than a brand new inferior powered wheelchair.

The next incarnation has just started now that I have several suitable, usable, powerchairs built & ready to go.  With that in mind... 05 - Feb 09

The new "version" I am now building has just begun.  I have one (very old and abused F55s powerchair) in the garage right now already stripped down to its basics. Took 35 mins.  It is a very very old and worn out affair -- much like the two on the first build... 

 It wont matter because I am only using a few of the original parts like the main frame and arms. I am only using those because here in my bedroom I cant fabricate better ones! 

Manufactured powerchairs really are horribly designed and made although the F55s Sunrise Medical one is the best designed of them all in my own opinion. Although that can be drastically improved! here The arms in particular are over complex and wear out every few months.

Given the opportunity to start from scratch with a proper workshop it would be easier to do just that. But I have non!  I work under very limited conditions.  

Here is a wider smaller wheel below with a bigger fatter tyre fitted. It came from eBay cheap, along with most of my powerchair stuff. Along with (five others) for a miserable 5 British Pounds each. They come from cheap small kids Quad Bikes. But again with 4 ply tubeless tyres, which are very cheap and easily available. The overall diameter is about the same as a stock F55 is at 14.5 inches. The sidewall is huge though.

Many different tyre tread patterns are available in this 145/70 6 tyre size. Overall diameter is about the same as the original wheelchair wheel/tyres. The advantage is in those huge soft sidewall.

Think "Smooth ride" even when driving over the edge of a curb or pot holes that pass for our pavements. They deform over obstacles. They can run slowly over a 2 inch square block of wood and the rubber just absorbs it and the powerchair hardly rises.

Its because they are balloon tyres with only 4psi pressure. Our pavements are almost as bad as these off road tyres were actually designed for. I will probably use almost slick like tyres but in this same "fat" balloon size in the end. They will ride smoothly over lumps and bumps,  Giving my poor spine a softer smoother ride all the time. These should be standard on all powerchairs...

Any idiot can bolt a set of these to a any wheelchair!  But of course that just leaves the powerchair far too wide for daily normal use. So its easy but pointless. The hard part is making them fit without making your powerchair wider. Every inch REALLY matters. I need to use it in my van and my house. The wheel size is also available in polished alloy if that sort of thing appeals. I would rather just have half a dozen very cheap steel (but will be powder coated) wheels and tyres kicking about as easy swap spares.

Quad Bike wheels

Fat off road wheelchair tyres medium |  Fat off road wheelchair tyres large

It will have big fat off road quad bike tyres on the rear. These are cheap used eBay ones. Thing is I can fit these now should I wish to this MK1 powerchair and I have tried them as the hubs I made to take the trailer wheels, are drilled to take these 3 bolt wheels as well. Just add some longer spacers and away you go!  But that's useless as the powerchair finishes up wider. That's bad. Its the sort of thing "manufacturers" or industry insiders do since they just don't get it.... There is absolutely no point making the total width greater since it makes the chair less usable on a daily basis - the exact opposite to what's actually needed.  So that means a big problem then!  And much work...

I want to be in this thing in my van, in the house, in the pub all day every day. I wont put up with any extra total width!  Or smaller batteries.  Any moron can just fit some big wheels and do that, but I want a daily all day powerchair for indoors and out.  So I have to do some serious modifications and somehow manage to fit full size motors/batteries as well as 12 inches of rubber into 25.25 inches (640mm)! Not easy.

wide tyres powerchair

wide powerchair tyres medium |  wide powerchair tyres large

But that means that the batteries either need to be smaller as the motors will need to be moved in by 2.25+ inches each side so the tyres don't hit them, in order to keep it narrow. So I am probably going to use much more efficient and better lithium iron, or lithium polymer (or safer Lithium Phosphate) batteries in this newest incarnation. If I can find a  volunteer / sponsor...  They have around 10 times the energy density weight for weight so can be much smaller and lighter. Trouble is they are also ten times the price.  (As of April 09 no sponsor found so have to somehow get 2x 75 amp hour lead acid batteries in there!)

Lithium's could easily give better range as well as more performance from a smaller and lighter package. Although really expensive. It will give a smoother ride on those balloon type tubeless tyres too so no suspension will be needed. And so yet more weight saving. And it will not sink in soft ground or sand as easily. So to keep the same or in fact much better level of range and performance the batteries can be much lighter but that's no problem with lithium's other than cost.

They are better at high discharge currents than equivalent sized lead based batteries, have greater cycle life and also don't spill and stay charged for long periods. They can also be fast charged. But charge them incorrectly and they can explode or catch fire violently. Fortunately there are safe solutions out there that can be used already packaged. Help, sponsors!

While I am at it I would like to go up to 36 or 48volts or above for a 50 to 70 percent speed gain and use a bigger amp roboteq controller since the wheelchair industry still insist on using inefficient old 24v 100 amp controllers and heavy old lead acid batteries...  (If I cant organise that at a sensible price I will see if for now I can find a way to get a pair of 70ah deep cycle batteries in there...) And I may have to do. so unless a sponsor volunteers their services! (Which is what happened...)

And with that in mind I have just stripped powerchair no. 3 down to its very basic parts...  Here is some of it..

Stripped down powerchair

This one was donated free by a reader (Thanks!) but if you fancy a project most used powerchairs sell for only a few hundred on eBay. It looked quite good when it arrived! 35 mins later it looks like this. Sadly wrecked.

And it has already been cannibalised for parts for the previous powerchair build. Its now going to be rebuilt properly with narrowed battery tray, (to allow me to fit the wheels/motors inboard) off road balloon tyres, as well as all the other mods shown in the other modified powerchair pages. I may even get away without  having to go to lithium batteries (and their stupid cost) just yet if I can turn one of the batteries around and redesign the battery tray in order to get enough space for those wheels/tyres -- one things for sure,

I will keep the total tyre width to the same size as it is now. 25.25 inches. Wider is easy. I could just fit the wheels but then its too cumbersome and wide for the house and my van. Notice the bigger wheels and tyres in that pile.. They are 6 inches wide each. That's 12 inches of rubber! Doesn't leave much room for batteries and motors. My head is starting to hurt. Now you know why they are not seen on any other nice narrow powerchair other than the Frontier X5 Mid drive one and that's too wide. After this they will appear probably!

Junk Pile...

Doesn't look very hopeful here does it? Trust me it soon will!

Power Wheelchair Front Wheels

I plan on using these eBay wheels for the front because they were (a) cheap! (b) prettier than the stock ones (c) lighter. They will also look brand new once blasted and powder coated. They are from a kids quad 50cc "minibike". (eBay of course!)

partly assembled power wheelchair

This is how wide and complicated the original battery tray and rear swinging arm suspension used to be on a stock powerchair. This image is stolen from part 1 page. The space where the battery goes is about 4.5 inches wider than the new simplified one. And we don't need springs as the big balloon type tyres do a much better job.

Rear View fat tyred Powerchair

working out the width medium |  working out the width large

Heres the new "project" Wheelchair. A quick look with the ruler shows me that space for those huge 145mm wide tyres is a big problem. Here the battery is turned through 90 degrees. Making it over 4 inches narrower overall from motor to motor...  Me I have a hacksaw and a brain. I knew this would be all but impossible without very expensive lithium (or Ni-Cad or Nickel Metal Hydride) but they are stupidly expensive at the moment (AWAITING SPONSORS!???) and I am not made of money!

So if its remotely possible to fit those wide tyres while still keeping the stock wheelchair overall track / width the same and also keeping the same range and 70ah stock battery capacity I will do it...  If not I will need to spend lots of cash. My ruler and a long look at battery capacity/size and availability of the stock type lead based batteries tells me that it CAN just about be done. I need to keep total width to 25.25 inches max. Or 640mm -- wider isn't going to happen Who needs a wider powerchair!

If I turn the batteries sideways (long-ways) on then that reduces the battery width by some 4 inches. 275 mm (280 clearance) wide is now 175 (180) or 4 inches if you are analogue... So we now have the following items to get in at the rear::

140mm (left tyre) -- 90mm (left motor) -- 180mm (single battery width) -- 90mm (right motor) -- 140mm (right tyre)

Allow an extra couple mm for tyre clearance and the total width "could" be just 640mm!  So I am building a new battery tray today. Now that the batteries are turned long ways around this tray will only need to be 180mm wide.

But the batteries total length back to front in the chair is now a lot longer. At least if I am to get the same group 24 sized batteries in. So the batteries will have to sit at a 5 degree angle rising towards the front and slide in from the rear on two bits of 25 mm angle iron welded to the insides of the new battery tray...  They will need to be higher at the front to miss the 50mm frame rail as they will sit above it now at the front edge.

They (batteries) will come about 4 inches past the front frame rail. So with that in mind and because I am working with no budget and from my bedroom (!) I cant be bothered to make new motor mounts. I will simply cut the old ones off the now unused rear swinging arms. Below.

Ctting motor mount off

cutting wheelchair parts medium  |  cutting wheelchair parts large

This is long suffering Brian. He is sweating doing this. And then he has to file it...


file medium |  file large

If you look closely (large image) you can see the filings coming off to prove he was actually working...


The net result is a ready made motor mounting (the left half!) complete with anti tip extension ready to weld to my new home designed narrower battery tray. We obviously did 2 of these...  As you will see from the marvellous engineering drawing done in the pub last night that is the new battery tray.


So I ordered some steel. I would do all of this in Aluminium Alloy but I cant weld that myself. So it needs to be steel. If I was a real manufacturer I would build the frame, the battery tray and most of the rest from light alloys too but I am not and they don't because nobody cares or understands and powerchairs don't seem to evolve in decades.:

1 off -- 440 x 180 x 5 (or 3/16 inch) plate (It has to be this heavy because it will also have my wheelchair clamp fixing welded to the bottom...
1 off -- 50 x 240 x 6 (or 1/4 inch) plate
2 off -- 550 x 25mm x 25mm angle strip

And did this...


All just leaned together above. Needs welding. The new battery tray will also be the motor mounting and the rear suspension will be gone!  No rear swinging arms or shock absorbers! They waste space and are heavy. The new balloon style tyres will give a much better ride anyway. Big soggy sidewalls. And they are cooler looking and less puncture prone compared to tyres with tubes... However if you prefer grey tyres on your powerchair you may want to give this mod a miss! They don't make tubeless 4 ply off road 4x4 tyres in grey. It will be clearer once construction starts!

new battery tray welded up

Now welded... Living a few hundred metres from a technical college is very useful, they have lots of metal, and TIG welders... And guys that know how to use them. My welding is crap. This cost me a beer.

battery tray welding

The bottom. Once finished (more parts to add and weld on) it will go to be shot blasted and powder coated and will look better than a bought part ever can.  This will then allow me to fit those wider off road tyres. It allows the motors to sit two inches (50mm) closer in, Giving a total four inch narrower rear end. Making room for the wider rubber without making the chair wider because that would be the easy but stupid way out. Who needs a wider powerchair..  I want mine as narrow and as short as possible since I have to use it in the real world which seldom makes room for bulky powerchairs. Shame the manufacturers don't seem to realise this.  

weld tig close up

This welding lark took about 5 mins but jigging it up accurately took me about 15 mins. Best to only weld it the once!

This of course means the batteries either have to be smaller (NO! That's what a manufacturer would most likely do!  I don't do compromises) or they have to be fitted in the other way around. And its a real problem. Space is at a bit of a premium here! Now since I didn't design the frame I have to work around it. The battery tray will have two rails that allow the batteries to be loaded from the rear and slide up inside at a small angle over the front of the existing frame rail. Its easier to wait for a photo in a few days...

Much more to come about this latest build when I have some more images and info to add hopefully..

part done narrowed motor mounting

With a thin coat of matt black paint (so I can work clean and I can mark the metal for drilling etc) it looks a bit tidier! The motors now bolt straight to this battery tray. with some 25mm alloy spacers. The gearboxes are thinner than the 90mm across motors. That leaves a space of 180 mm for the batteries. Since the batteries are not quite this wide it leaves JUST enough room for some domed headed Allen bolts (polished stainless steel of course!) to hold the motors on. This sort of thing is dead easy if you are working for a wheelchair manufacturer but damned hard work if you are working in a bedroom! As is scrounging metal and welding time at the local college that I don't even go to. 

I would DEFINITELY do this in light alloy (Aluminium) if I had a proper workshop. And the main frame. Its hugely lighter and doesn't rust... So why don't the "real" manufacturers do things properly? Either they cant or just don't get it or the bean counters wont let them. Or they don't care and think we don't know the difference. Well they are wrong.

narrowed battery tray welded

Bigger size  |  Really big image!

So here is an unfinished battery tray. Awaiting some 25mm (1 inch) angle so I can continue. This is the bottom. The wheels and tyres are about 20mm smaller overall than the 3.50 x 8 ones on the other two chairs so I mounted the motor plates a little lower down, hence the bolt holes being accessible from the bottom. This will mean that the actual powerchair frame is exactly the same height as the other two powerchairs here. It has to be the same as it also has to fit my vans wheelchair tie down. Just like the other two.

Testing motor fit

check assembly medium |  check assembly large

Well after drilling and tapping the two holes at the front so I can try it bolted in place and after attaching two old motors temporarily we get a figure of 364 mm wide between the outsides of the motor cases. This is the bit that the new tyres have to miss. So if we add the 2 x 145 mm tyre widths we get a total rear width of 654mm, Realistically we need about 5mm of clearance between the rear tyres and the motor casings so that will be a total rear width of 664 mm when completely finished. That's 26.1 inches! That's less than it is now... And less than my manual wheelchair. So we can still get 70ah batteries, as well as 145mm wide tyres in there without needing to make the completed chair any wider of have any less range.

Powerchair frame

4x4 powerchair assembly medium |  4x4 powerchair assembly large

A view from the front. The motors are very "inboard" now and the batteries fit long ways around and will slide in from the rear on two angle iron strips welded to the battery tray to give more strength and also to give me a mounting point for the seat front. You will need to wait and see! Today I am busy doing normal stuff...

JCB Powerchair

JCB style powerchair medium  |  JCB style powerchair large

Why am I doing this? Because it will look cool! And it will go off road, and look at that big sidewall! It will give me a smooth ride. I just propped it in place so I can see how it will look. Its almost in the right place here.

Off road wheelchair

measuring overall width medium |  measuring overall width large

Its in exactly the correct place here. With the new narrow battery tray, inboard motors, and everything the total overall tyre track or width is actually less than a standard Sunrise F55s Power Wheelchair. 

You have to ask, if they look so cool, ride better on those soft low pressure balloon tyres (which are tubeless and don't puncture anything like as easily as tubes do), save weight (no swinging arms or rear suspension units) use less parts easier to clean and are more easily swappable in the event of a problem then why don't the manufacturers do it this way?  Then I wouldn't have too...

They all seem to be stuck in the dark ages. Pride in particular seem hell bent on persuading us that mid wheel drive chairs are a good idea! (other than for marketing).

Where is the corrosion free carbon monocoque one piece autoclaved ultra light frame, battery housing and motor mount with seat?  Where are the 200 amp per channel higher voltage and higher efficiency controllers and fast charging lighter lithium battery power with brushless motors that I already use with my model helicopters and aircraft?

Its expensive but I don't care, its my legs. What are yours worth? Its all available and all easily possible. And it won't get cheaper unless people use it!  But sadly we all still have iron powerchairs with steel / iron railway engine construction and tubed tyres with lead batteries. I find it all very sad. I could do massively better with a small budget here in my bedroom!

All of the small changes detailed on the previous powerchair modifications page make a huge improvement to the chairs day to day usability. Even the decent batteries and 1 hour charge capability frees me to go out in the evening in complete confidence. This current wheel and tyre mod makes it better again. If I can do this stuff in a bedroom then what's their excuse? Right Got to go!  I am fed up with scrounging TIG (Tungsten Inert Gas) welders and getting others to do the welding so I am ordering a cheap TIG welder online. Tools are so cheap now. (less than 300 for 150 amp TIG with Gas ready to go. And another 80 for a decent mask that goes dark automatically) And the Angle Iron that I was waiting for just turned up!  Along with some more pre cut 3mm sheet steel. Work to do.

New powerchair battery box ready for welding up

OK -- now after about 30 mins with an Olde hacksaw we have the angle iron strips cut to length, (one longer than the other since it has to provide a seat support mounting and is yet to be drilled) and two sides.

Oh and the front plate laid on the floor. I took it to the local college to scrounge a little more welding time (mines not here yet) and would you believe they are missing again!  Do teachers ever go to work?  Half term.  So I am temporarily stuck until either they go back to work or my new TIG welder turns up. 

Well at lest you can see what the plan is. The batteries slide up those two angle strips, over the front chassis rail.  Once its all been welded and bolted in place and tested for battery fit, motor fit, frame fit etc etc it will be shipped off to the powder coaters.  It should really be built from aluminium with super neat welds and mirror polished - as should the main frame. But I don't have the equipment here.

Again if the manufacturers built a proper lightweight alloy powerchair I wouldn't need to anyway would I?  Of course loads of so called industry experts will tell you its not practical, too expensive, has all kinds of safety or structural issues yada yada yada but that's just crap. It stems from little competition and large profit margins and easily satisfied customers. How do I know? Because that's just what the Japanese bike companies said in the 60s 70s and 80s. Guess what they build now? Yep lightweight alloy chassied short sharp road rockets with fat tyres and decent suspension tons of horsepower and decent brakes...  I could have told them that in the 70s.

That's why all sports bikes come with light alloy frames that are stiffer too. Steel frames are now thought of as bad handling overweight dinosaurs. As below. In the eighties the only alloy frames were built by individuals and specialist companies like Spondon Engineering in Derby.  That's why in the 70s and eighties bikes didn't handle well and the frame was so heavy it was hard to carry.  Now they can be carried with one hand easily. On a powerchair there are MANY steel heavy badly designed parts that should be alloy or better still carbon fibre or simply designed out altogether.

But I digress...

Back to work..




completed narrowed powerchair battery tray

narrowed f55 battery tray medium  |  narrowed f55 battery tray large

Now its all welded together and given a quick spray can matt black paint finish so its clean to work with. Can you see how it works?  If I had a proper workshop like the manufacturers have rather than a bedroom this would be a simpler design and be aluminium. It would be stronger and lighter and would be prettier and anodised black or silver. No need for paint or corrosion!

So why don't they build like I want or would do? Options: (a) They don't know how. (b) They don't understand the need or the advantages.  (c) been counters -- cost, unlikely as I don't see why a lighter simpler design costs more.  (d) easy life, lack of competition? Maybe... (e) they think we don't know the difference...  Paint it a jazzy colour, they will think its great! I like black as it happens.

rear view new wheelchair

The batteries slide long ways up this chute from the rear (!) and over the front Frame rail. This means that the batteries are as big as before but they are the other way around making room for the fat tyres and inboard motors.

This will of course have a door so battery swapping takes seconds. All my batteries already have a wiring loom attached and they just plug in. I have a LOT of different batteries!  I test them so you don't have to!  Please excuse the crappy weld on the left! The original paint made it not go quite right. Well it might not look pretty but its strong... And all of this will get a thick layer of powder coating once everything has been fitted together to test. Just like the other chair here


The bottom

inverted battery tray

Upside down again showing the front. One part has been left longer to allow the seat support to bolt on. Needs a hole drilling 8mm yet.  And the whole part then needs a mounting welding to it so that the vans wheelchair clamp can safely "grab" my van. I may also add a strengthening piece to the front plate as this is all that stops the batteries from continuing forwards in the event of a vehicle crash. As it is I suspect it would be strong enough but we will see.

assembly trial

Ok here it is bolted to the frame... With a motor in position.  Bigger size  |  Really big image!

wheel/motor/narrowed battery tray showing the look of the rear

powerchair medium  |  powerchair  large

Ok here it is bolted to the main frame. And it has a motor bolted on, with all the wrong bolts and spacers in temporary fashion. Ignore the spacers and bolts that are sticking inside where the battery needs to be -- the bolts were a bit long! And the wheel is just propped in place in the shaft since I am waiting for the machine shop to return my new mountings designed again on a beer mat!

Now you see how it all will go together. Direct drive motors inside the wheel would have been slimmer and no need for the new centre section but where is the fun in that?

Constructio detail electric wheelchair

Right. Now I have machined some 16mm alloy bars to support the rear end/battery tray/motors. It is easy to buy these 8mm Rose Joints, Rod ends, Spherical bearings or whatever they are called for about 2 pounds each on the Bay of E. I buy them by the box as you can see...

Remember that this is all a trial fit to find all the right spacer, rod lengths etc. Which is why the horizontal one currently has a stack of washers! And to measure up for the correct polished stainless steel domed headed bolts. All these alloy bars, battery tray, and frame will be shot blasted and then powder coated and it wont look all rough like this on final assembly.  And new 4 pole motors with the tallest gearing available. Fast is good.

rose joints and alloy bars

Another rear view so you can see how it goes together.  The reason for 4 alloy upright bars is to make damned sure that the very outboard wheels don't bend the motor mountings inwards in heavy use like when leaping off curbs... Stops them twisting.

dry build to see how it goes together

Here you can see how the main frame is attached. The weight is transferred directly to the motors (actually the gearboxes) rather than the battery tray.

on end powerchair

And here you can see how well the wide wheels and tyres now tuck under the frame. Its actually NARROWER than a stock powerchair whilst still allowing the use of group 24, 75 Amp Hour batteries...

another view of wide tyred 4x4 powerchair

Here is another View.

battery door

battery door medium |  battery door  large

It needs a battery door. Not an elegant solution but strong and easy to implement in a home workshop -- Stainless Steel door hinges bolted on with 6mm stainless steel bolts and nuts!  the door itself is just 3mm steel plate. eventually it will be powder coated and pretty of course. Now its easy to load and unload batteries as you just open the door and slide them in or out.

battery door closed

Battery door closed.  battery door medium |  battery door large

batteries installed

And with some big full size (MK) Group 24, 73ah batteries in place to check they fit well.  They should unless my ruler is broken...  Not all batteries are EXACTLY the same size though. My new home built battery tray thingy allows batteries that are  175mm wide, 225mm high and 270mm long maximum. Fortunately that means lots of choice of the type and size (capacity) of batteries that I prefer. These MK batteries were free to test (thanks!) but they wouldn't be my first choice! 

I am using them here only to check that they fit in the space. They cannot make the currents I need without voltage drop being a problem. So much so that wheelies and even hard acceleration make the joystick lights go dim and power is lacking. All Gel batteries do this at a good solid 100 amps per channel. (both motors)  For most peoples needs these MK's are as good as it gets though as they just don't need this power. Personally I will use AGM batteries. They are way better at fast energy release but don't do as many "cycles". Hawker Odyssey or Optima in are my choice this case.

See: Inverters and Chargers  &  All about Powerchair and vehicle batteries and  Which batteries to buy and http://www.wheelchairdriver.com/powerchair-batteries.htm

off/on road powerchair  larger view

Rear view. Trust me it will look as good if not better than this one does once its all been fully built, then totally stripped apart and all the bits sent off to the powder coaters. 

wheelchair wheel adapters

wheelchair wheel adapter medium |  wheelchair wheel adapter  large

Wheel mounting plates/adapters and spacers. All made from old pulleys... Don't worry it will all look better than new eventually when powder coated and reassembled after this trial build.

off road power wheelchair

fat tyre wheelchair medium |  fat tyre wheelchair  large

Wheels fitted on those adapters. Motors removed temporarily for weight reasons. This looks wide.

But its actually the same as a stock F55s powerchair at just under 26 inches... Its a delusion! 

I will get a softer ride if it kills me. The standard thin tyres with "shock absorber suspension" simply didn't! Its all in the bin now... Saved the weight of those swinging arms, the shock absorbers etc. This is just as compact, narrow, "floats" over soft ground like sand and the huge sidewalls and 7 to 10 psi tyre pressures give a very soft ride. And of course being 4 ply and tubeless all but puncture proof. So we ill get the same full range, full power as a full size powerchair but with the compact measurements of a small indoor only powerchair and with big fat fun tyres! I love it when a plan comes together.

Wheelchair sat on fat knobby tyres

wheelchair kitchen medium |  wheelchair kitchen  large

How it will sit. Notice the shoes on Brian's feet...

cool powerchair!

off road style powerchair medium |  off road style powerchair  large

Well that's all the basic engineering done at the rear end. It all just awaits stripping down, shot blasting, powder coating and re assembly.

drill the front caster

Caster fork being drilled medium | caster fork being drilled large

Now the new front casters and new eBay front wheels.  The new wheels have 10mm diameter shaft/bearings. The original ones that were in the original "expensive and weak" wheels were 12mm with a 12mm shaft. It located up to the caster fork and had a nasty 8mm bolt that held it in place. They work loose and so a tab washer had to be included. I just drilled the new caster fork out so that a 10mm new stainless steel axle can slide completely through the fork, the spacers (alloy, 16mm bar, 16.4mm long and bored out 10mm and currently being made) and the bearings in the wheel. Actually the bearings will be stainless steel ones on final assembly as stock ones corrode, and drag in hair as they rotate. This lets water and road crud in and they corrode on the inside too... 

Now just to make the spindle for the front wheels and get them fitted below...

fasterners - special washer

special washer medium | special washer large

OK. New 10mm diameter axle made.. Simply by using 10mm bar cut to length (107mm to be exact!) and drilled and tapped M6 on the ends. It goes straight through the castor fork, wheel, spacers and everything. It is held in place by two special alloy anodised black washers and two M6 countersunk screws as shown.

Looks neater than stock (a rust prone M8 hex Bolt & tab washer!) and is stronger since the thread takes no loading because the axle fits accurately inside the fork leg. So it wont come loose and needs no tab washer... Who designs these things?   Ignore the bearing. Its there just for measuring purposes. A stainless steel sealed one (4) will be fitted as stock ones rust and fail.  Again since Stainless steel ball races are no dearer to buy why do they fit steel ones in this situation? God knows.

Front wheelchair axle

Axle = 10mm stainless steel bar with tapped M6 ends, some fancy alloy eBay washers, (available in many colours and sizes) and some countersunk (to be polished) stainless bolts... Not too hard!  AND IT WONT RUST or sieze...

Wheelchair spacers

Now the spacers. These are 10mm bore (10.4 actually to allow some clearance) and 17.00 mm long... Made from 16mm bar alloy. Instead of steel as per original. These too will be powder coated... Eventually.  My Olde trusty Myford lathe is very useful. 4 needed obviously...

Cool OFF ROAD powerchair

Cool off road electric wheelchair medium |  Cool off road electric wheelchair  large

Heres how it looks at the moment. The anti tip bars have been shortened. It means I can reverse even further back to the wall and they will not hit anything behind me when manoeuvring. This further helps this powerchairs agility indoors. It was already shorter than my manual chair before cutting 2 inches off...

They will be fitted with 44mm skateboard wheels and stainless steel bearings eventually. They will allow a slightly higher tip angle than stock setup. That's good!  I sit balanced on those wheels in the pub... They are also further inboard by 4 inches compared to a stock powerchair on each each side. Further keeping them out of the way. When it comes to all day powerchairs every inch (or even less) makes a huge difference. I wish the manufacturers would realise that. They seem to add weight and inches everywhere willy nilly for no good reason. Oh and the front wheels/casters are fitted so I can see that they clear the new centre section/battery tray etc. 

I have removed masses of metal, brackets, extended "bits", and other overweight rust prone bits during this build. I have half a room full of oversized overweight parts that are just better removed. E.g. have you ever used indicators in a powerchair? How daft - they both get in the way, look crap and weigh a ton at the same time.  Weight MATTERS. It effects range, battery longevity (due to average discharge cycle depth) as well as performance. 

The original front casters, wheels and bearings and axle (shown fitted here) alone weigh a ton!  The new wheels are much lighter with smaller bearings and shaft too as well as being almost free at 20 up pounds for 4 complete wheels and tyres! But the caster forks themselves are still very heavy and still prone to bending if you wheelie a lot... They should be alloy and a better design that can stand side loads when you land and they are pointing the wrong way. I am looking at making some lighter stronger ones once this chair is done from carbon fibre and a friend with an autoclave..

Wheel centre disks fitted. These are turned and countersunk in the centre for a countersunk stainless steel cap screw. But I have non here yet so its got the wrong bolt in. Both it and the wheel will be shot blasted and powder coated eventually after the trial build before final assembly.

New footplate parts. Pretty self explanatory. The footplate is 3mm alloy sheet. Cut out with a jig saw and a file to clean it up. The bit that goes around the back was a limp of 2 inch aluminium angle strip just cut out with a saw and a file. When marking out I just drew around a pair of size 12 shoes and used CDs for the rounded corners. Nothing very high tech...


Underneath, taped up ready to drill for six rivets! Then like all the rest it will be assembled, tested, then dismantled and sent for blasting and powder coating.

footplate mounting drawing

Here's the actual footplate cut from 3mm alloy sheet. Its actually the same depth (side to side in this picture) as a sheet of A4 paper. Mostly because I designed it by sticking a pair of my shoes on a page and drawing around the heels! So you should be able to draw your own from this pattern.  Bigger view

The paper sat on it is my plan for the footplate mounting shown below.  Its as good as most of my engineering drawings. So you should be able to copy this if you prefer this type of footplate to those awful "swing away" ones that this chair has as standard. This is the latest incarnation!  The long Allen bolt that you will need is M8 X 140mm. Not easy to get locally but orderable online.

Wheelchair is facing up and we are looking at the bottom. This is how the new footplate attaches. The two gold coloured bits are Rose Joints (roast joints according to my carer Jenny). They are important. The whole rear of the wheelchair attaches by two M8 bolts from the bottom, and they screw into the rose joints which serve as nuts.  Why rose joints? 1.60 each on eBay... And because we need the complete footplate to hinge up and down with the seat so my legs can stay the same length. And because they are strong!  This shows the long bolt going straight through the alloy bar since its drilled 8.3mm down the middle.

Roast Joints

This shows the same bolt screwed into the alloy bar on the left. As is the short 30mm bolt on the left.

powerchair footplate modification

And this shows a 20mm square bar fitted into the gap! It obviously is also drilled 8.3mm so as to make this possible! Now it just needs cutting to length and have the footplate bolted on to it. Then as per usual it will all come apart and be powder coated and sent back for final assembly.

footplate solution medium | footplate solution large

Seat frame fitted. Still to have the front bits that stick out cut off. They were for those pre historic looking "swing away" ones that the standard wheelchair comes with. Awful things, look terrible, get in the way when transferring, weak and add "corners" preventing manoeuvrability in tight areas. And the footplate is riveted together and fitted.  Note all the rose joints and more 16mm bar used again. Good job they are cheap on eBay! 

The roast Joints (copyright Jenny) allow the seat frame to tilt (if I decide to fit an actuator) and the footplate follows. Everything is corrosion proof neat well engineered and strong. And amazingly light compared to the huge pile of old iron parts that is piling up as I throw away all the cheaply made badly engineered bits from the original powerchair...

Wheelchair Footplate

footplate powerchair front medium | footplate powerchair front large

The other side. Try to ignore the tyre fitted backwards...  You can see that the footplate is hinged up and down on rose joints (spherical bearings, rod ends or whatever you call them) and the seat position is fixed by the one that is on the right of this image.

powerchair rear

powerchair rear view medium | powerchair rear view large

The rear end. It will get its battery door eventually! And a seat back.

powerchair rear quarter view medium | powerchair rear quarter view large

Rear quarter We are slowly getting there. Like British Rail. Only they never did. I will not be fitting the seat back, the rear door, the batteries, or the various control pods/power modules yet since this is just a fabricate/trial build and I now know everything I need to send all the bits you see here along with many that you cant both old, fabricated and new to be blasted, and then powder coated..

So the basic modifications are done. Now all that remains is to re assemble it with care and a tub of grease and polish all those stainless steel bolts.   Reassembly but better than new as per the other powerchairs over hereI wont repeat many of the build detail here as they are on this page too. which you really need to read first since this new page follows on from it..

Skate Wheels medium | Skate Wheels large

Trial fitted to a dirty tatty but mechanically completed powerchair. Now as you can see I have fitted small ones. They allow for a tip angle of about 40 degrees. I like wheelies and do them all the time like a loony...  It will all look cool once powder coated and rebuilt is about a week.

I fitted four because I have fell out of the back several times when they sink into softer ground! So with the 4 wheels and the bar going right across its hard to see how than can still happen. We will see! Bigger wheels would help here and its what the safety Nazi manufacturers would do.

But I refuse to lose any manoeuvrability.. My way is better. Remember they are shortened by 2.5 inches as well. Much better than sodding great castors sticking out like mid drive chairs! And it reminds me of my drag racing days!

Battery door finished. Now rigid, strong and light. Hinges are stainless steel, not too elegant but very functional! Batteries slide down the chute. All carefully planned so that the door closes inside the battery tray area.

Battery door medium | Battery door big

Like this. The middle top bolt holds it closed. And the batteries in. Easy swap batteries...

These are good examples of how extreme I am when rebuilding properly! They are just Skateboard Wheels.

I use these to replace the horrid grey rubber ones that have no bearings with these. The ones I use in all of my powerchairs. They are available in all kinds of sizes.

Off road the bigger 70mm black and yellow ones are better. On road where they will not "sink" in soft ground the smaller black ones allow higher wheelies and even allow me to sit in the pub balanced on these and the main wheels while I have a beer. They are available wider if you prefer for off road use too.

Or you can fit four rather than two by using a longer bolt. All skate/board/inline skates use the same sized bearings. All have an 8mm hole in the centre for an M8 bolt. The same as your wheelchair! So buy 22 x 8 bearings to go with them. All available from eBay...

The bearings are of course Stainless Steel  As you know by now I don't do corrosion and rust! They are the same price almost anyway... Why don't the manufacturers do this? Don't know.

They last longer! The black ones are hard. The yellow ones are soft urethane. Many different ones available. The stock rubber ones last about a week if you wheelie all over the place. 

More to come tomorrow. 9 May 09...

Actually there is no more for a few days. On Tuesday it will be disassembled and all bits shipped to the Powder coater.

They will be cleaned in acid and blasted. Then ALL parts will be powder coated.

No manufacturers thin layer of semi gloss paint here! We want complete easy to clean long lasting corrosion proof good looks years from now.

All the salt and road crap should be able to be washed off and the powerchair look as if its just been built. Standard ones don't do that! They look wrecked after a year.

The next section will be added when we start to assemble everything again. Burgerman.  In the meantime:

Cant decide if I should fit Optima or Odyssey batteries. Both are equally good. Both are the same price.  Both are capable of starting a truck so no issues with lack of current like I always have with all Gel batteries.  Still not sure. Both do 400 cycles or so at 80 percent depth of discharge. The odyssey is heavier, bigger and has slightly greater capacity. Both outperform Gel batteries when I use them by miles. Maybe I will get one of each! (Joke)...

Either way these ones are dead (Jim) and non too healthy.


(Part 1 | 2 | 3)

That's all the fabricating and modifications all done. Now to send all the parts away to be powder coated and rebuild it!

Added a footnote:

Just been looking at how much of this powerchair is actually modified, fabricated and original.  These chairs of mine evolved slowly over ten years of adaptation and improvement as I fought to fix bad design and bad finish etc. I just realised how much is changed after looking at yet another cheap eBay chair in my garage...

Original stuff:

  • Main frame (although powder coated)  I could design better for my needs but not in a bedroom!

  • Front casters powder coated as the original paint is dull and thin. But using my lighter better wheels on my axles and bearings in (stainless steel) Did I mention I hate corrosion and failure?

  • Seat frame/upholstery. Although mounted further back on my fabricated mounting plates and supported at the front with alloy bar and rose joints. And the front mountings for the swing away footrests cut off. And again its WAY too heavy! And the arms fail every few months and go all loose and rattly where they mount... Arm side plates replaced by lighter better bars And powder coated. At some point I will have to replace this with my own lighter alloy more simple and elegant longer lasting design since it annoys me.

  • Motors (6mph 4 pole)  As fitted to the latest Sunrise F55s with the Cush Drives replaced with a metal strip as they fail. They are big heavy and non too efficient!  I would really love to replace them with brushless gearless ones and may well do so soon as I am looking at some now...

Fabricated / replaced stuff:

  • Bolts / fasteners - Every last one!  Replaced with Stainless polished cap screws or Allen bolts. They look good and do not seize or corrode...  Since powerchairs cost as much as a small car why are they finished like a Chinese bicycle?

  • Swing away footrests. Too big, too far forwards, and they make your chair have corners! And transferring is hard as they are in the way. I made a better lighter smaller stronger single one that helps manoeuvrability.

  • Seat mounting plates. Fabricated because the whole powerchair is way too nose heavy! So I moved the seat back about 3 inches.

  • Kerb climber - heavy and pointless. I can now do bigger curbs just by popping the front wheels up with the C of G corrected and better programming etc.

  • All kinds of iron bracketry, A big box of heavy un needed bits, everything from spacers to brackets that hold brackets. All over weight and not needed.

  • Plastic fake carbon battery covers - binned

  • Battery box - no longer needed

  • Rear suspension swinging arms - Binned not required with fat balloon tyres

  • Rear suspension units - to stiff and too heavy and too short travel. Binned not required with fat soggy low pressure balloon tyres

  • Lights - heavy steel and glass things! - Binned non needed. Kept the rear ones because I don't want to get killed on the way home from the pub...White reflectors are all I need on the front. Not strictly legal but who cares.

  • Main 80 amp power controller - Stored replaced by reprogrammed 100 amp unit.

  • Full power / Lighting actuator - Stored... Legally required on a 6mph+ chair (road legal!), as it works the lights. But ridiculous all the same just more weight and wires etc. Lighter is better.

  • Rear wheels and tyres/tubes. Replaced by less puncture prone smoother riding tubeless off road "quad" tyres.

  • Front wheels - replaced by lighter prettier cheaper eBay wheels in the same size (4 inch diameter,3 inch wide rims

  • Wheel and Caster bearings - replaced with stainless steel ones since they fail due to hair/corrosion.

  • main frame/centre section, battery and motor mounting replaced with my own narrowed one piece unit.

  • Anti tip wheels - replaced by harder wearing smaller skate wheels with stainless bearings as long wheelies wear them out fast. And they sound better!

  • Batteries. Gel batteries can't cope with the currents required with tall gearing, 100 amps and above controllers and my weight! Replaced by top of line AGM batteries.

  • Plenty more but I'm bored now...

Seems not much of the original left!  How did that happen?

And the following is just some cheap junk bought off eBay.

off road wheelchair wheelsThe rear tyres above NEED grip off road. Especially on sand or wet grass etc. (Update - And snow! Couldn't get to the pub last night...) So a tread pattern like this one opposite on the drive wheels is a good idea. The drive wheels control where you go and drive you along. You COULD also fit these tyres opposite (and the wheels should you wish) to your stock powerchair - they are the correct size to fit straight on to the front castors.

They are an "off road" tread pattern, designed for grip and they match the style of the new fat rear ones. But you wouldn't be too bright if you did!  Only people that don't quite understand real powerchair dynamics or even basic physics would see this as a good idea...

The reason? The front casters job is to go wherever the rear wheels steer the powerchair. And the easier they turn around on the spot or move the better. For this reason grip is the very last thing you want here!  The less there is under any circumstances the better. On carpet, grass, sand, or tarmac. So even on a powerchair that will be taken off road its always better to fit the smoothest and most rounded profile tyres you can find. So they have as little grip as possible. Like the stock ones... HERE Anything else is just style over function and makes no sense at all. 

I bought 4 similar to the above eBay image myself. Not to use the tyres but to use the wheels as they are lighter and better designed and look prettier than overpriced powerchair ones. And they are the exact same size. That is 4 inch diameter rims x 3 inches wide.

The whole package below was 20 UK Pounds for 4x wheels and tyres on eBay. It includes 4 tyres (to be re sold on eBay) 4 wheels with bearings and spacers and four inner tubes!  The tubes alone cost that much from a mobility dealer! See below:

So for reasons of better more functional manoeuvrability I will not be fitting these 3.00 x 4 tyres to the front!
I only bought these eBay ones just for the wheels and will be eBaying the tyres...  Or it will just suck more amps and make turning more difficult while ripping up carpets and grass and defeating the object of a free moving caster at the front! I will fit these tyres HERE  (Added, I already have fitted just the wheels!  Make me an offer for the tyres?)

In the meantime here's Vera again looking confused by her phone

Fit bird with phone

Fit Fit bird with phone (Large)  |  Fit bird with phone (Larger)

This is Brian. (Brain) he does all the stuff I cant. Long suffering because I am a perfectionist and he does everything twice... And is getting very good at building powerchairs at the moment.

(Part 1 | 2 | 3)

That's all the fabricating and modifications all done. Now to send all the parts away to be powder coated and rebuild it!

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