Electric Wheelchair Design "hyperchair"

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Fri Mar 07, 2014 6:26 pm

Below is the drawing for the two bearing housings:
bearing_housing.jpg (56.33 KiB) Viewed 4016 times
The bearing clearance is to allow for distortion whan the housings are welded into the frame. After welding the bearing housings into the frame it was found that a small amount of filing was required at the top where the metal had melted and was obstructing the bearings from being pushed in. Once enough clearance had been provided to allow the bearing to drop in the first 4mm or so they could be hammered home using a ring spanner which was of a suitable size to push just the outer ring of the bearing into the housing. The lower bearings are now a tight fit after welding and will need some bearing loctite to stop them rotating when in use.

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Sat Mar 08, 2014 6:17 pm

After cutting X, X', Y and Y' down to 17cm, they were welded into place along with S and S'.
After welding S and S' into place it appears that although strong enough in the assembled configuration they will need reinforcing with corner bracing.
The photo below shows the top section in place:
chair_trial5.jpg (98.82 KiB) Viewed 4016 times
Still to do:
1) Keyways still need cutting on hubs. (Completed on 10/03/2014)
2) reinforcing needs adding to S and S'. (Completed on 13/03/2014)
3) AE, AE', S and S' need drilling and 10mm bar welded across middle (to stop top frome jamming to bottom frame when assembling/disassembling) (Drilled & Riveted 14/03/2014)
4) AC, AD and AD' need drilling and 10mm bar welded across middle (used to stop arm rests and joystick tubes from rotating). (Drilled & Riveted 14/03/2014)
5) AC, AD and AD' need welding onto top frame. (Completed 21/03/2014)
6) AG needs drilling ready for bolting to joystick module and welding to AF. (Completed 21/03/2014)
7) arm rests need cutting from 5mm steel (may need reinforcing with tube underneith) and welding to AI and AI'. (Cut 22/03/2014)

Each 5mm arm rest plate has now had 3 M5 holes tapped into it and the tubes which will be welded to AI and AI' have been drilled and bolted to the arm rests, this will make the 5mm plate part of the arm rests removeable for upholstering at a later stage.

8) Weld arm rest tubes onto AI and AI'.
9) N and N' need 3mm plate welding on both ends, reaming out to 10mm and welding into place. (22/03/2014 Welded plates on one end, ground down to appoximate circle and centre drilled)
10) Q and Q' need cutting to length a thread cutting on one end and welding to already assembled footrest.

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Mon Mar 24, 2014 12:45 pm

Parts LIst (Not including tools used)t:

Rear Tyres
2 x 15x6.00-6 4 Ply Kenda K500 Super Turf with K-SHIELD
total cost=85.9
Rear Rims
Hegar 2 x 6” Spun Aluminium half 2.5”
Hegar 2 x 6” Spun Aluminium half 2” + £24.04 duty
supplier=Hegar (USA)
cost=$100 (£63.83)
delivery=$40 (£25.59)
total cost=113.46
Front Forks
Pair of Front Wheels, Tyres, Forks from Betterlife Wheelchair
supplier=Ebay (yellabelly72)
total cost=16.98
Front Wheels
E300 Front Wheels for Razor E300 Scooter ( 2 off )
total cost=52.95
Motor Quick Release Blocks
Aluminium Square Bar – 2.1/2”x2.1/2”x125mm Long
supplier=Ebay (forwardmetals)
total cost=19.28
Bar for Quick Release Blocks
Bright Mild Steel Bar 5mm Dia x1000mm (4 off)
supplier=Ebay (ukfab12)
total cost=8.95
plate for Quick Release Blocks
mild steel plate 250mm x 250mm x 3mm pack of 2
supplier=Ebay (ajdfansltd)
total cost=3.4
Bolts for Quick Release Blocks
M6 A2 Stainless Steel locknut pack of 20
M6 A2 Stainless Steel Allen cap 35mm bolt pack of 20
M6 A2 Stainless Steel allen cap 20mm boltpack of 10
supplier=Ebay (abolt-fromtheblue)
total cost=4.68
Rear Wheel Hubs
Aluminium Round Bar 3.1/4 Dia 150mm long
supplier=Ebay (alum-droitwich)
total cost=30.41
Gasket for Hegar split rims
Rubber Sheet 3mm Smooth Finish Neoprene 100mmx100mm
supplier=Ebay (parki.babs2012)
total cost=2.54
tube to extend freewheel bars
Steel Precision Tube 10mm O/D x 300mm long 2mm Wall
supplier=ebay (brilliant2buy)
total cost=5.03
Bearings (for castors)
Bearing R8 2RS SS 1/2 X 1 1/8 X 5/16 STAINLESS R82RS SS
supplier=ebay (bearingoptions)
total cost=22
16 off M8 washers for wheels
16 off Titanium M8 Washers, Lightweight
supplier=ebay (tibenn)
total cost=16.92
20 off M8 bolts for wheels
20 off M8 Allen Cap Head Screw Bolt Stainless A2
supplier=Ebay (abolt-fromtheblue)
total cost=3.44
7/8” x 16swg (1.62mm) 6 metres x 2
total cost=39.312
joints between frame sections
1” x 18swg (1.21mm) 6 metres
total cost=17.976
inner tube for bearings (castors)
1.1/8x14swg tube 3m
total cost=18.9
tube for bearings (castors)
1.1/4x10swg tube 3m
total cost=27.156
For retracting footrest 10mm dia bright mild steel round bar 3m
total cost=13.332
For front forks
50mmx5mm mild steel bar (3 metres)
total cost=28.524
Titanium Assembly Lubricant (Molyslip Copaslip)
£6.15 inc delivery (ebay)
Loctite 641 (To stop bearings rotating in housing)
£0.99 + £2.60 delivery = £3.59 (ebay)

Total Cost = £540.88

Not included so far:
DK-PMB01 Dynamic Shark Controller
DK-REMD01 Dynamic Shark Joystick
Cable to connect Controller and Joystick
Power Cables to connect controller to Batteries
1444870 (Invacare part number) Right Motor
1444871 (Invacare part number ) Left Motor
Vinyl Seat Back
Seat cushion (made from plywood sheet, metal clips, cloth cover and upholstry foam)

All of the above could be obtained from a second hand Harrier Plus or Spectra Plus wheelchair - it would need to be a newer model as they used to use P&G controllers - seen on ebay for £150, (need to find local seller).

Arm rest upholstry (made from cloth cover and upholstry foam)
LiFePo4 batteries to run chair - plan is to use 16 batteries in two sets of 8 - Cost approx £320
Boxes for LiFePo4 batteries - plan is to purchase aluminium sheet and weld together to make 2 boxes.
Under seat box for odds and end - plan is to make a hook-on box from aluminium.
Powder Coating of Frame.

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Mon Mar 31, 2014 1:57 pm

A trial assembly was carried out to ensure that the batteries would not rub on the tyres when the chair is in use. an additional cross-member has been added behind the batteries as they were rubbing on the rear tyres.

After the trial assembly it was decided to tack on the footrest as a temporary measure to check the position - The chair is now useable , although the footrest bracket still needs finishing and swapping with the temporary tube currently holding the footrest in postion.
The photo below shows the chair as of 29/03/2014:
chair_trial6.jpg (99.95 KiB) Viewed 3993 times
Items still to do:

1) N and N' have some 3mm plate welded on both ends, but still need reaming out to 10mm.
2) N and N' need welding together and then welding onto frame.
3) Q and Q' need cutting to length a thread cutting on one end and welding to already assembled footrest.

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Mon Mar 31, 2014 4:02 pm

Mass of individual parts (kg):

Part Mass (kg)
lower frame 11.5
upper frame 3.26
Seat 2.66
Joystick 0.64
Arm rest(No 1) 1.01
Arm rest(No 2) 0.97
Wheel Assy (No 1) 9.86
Wheel Assy (No 2) 9.81
Battery (No 1) 15
Battery & Controller & cables 16
Back rest 2.56

Total Mass 73.27

If light weight batteries (LiFePo4) - 7kg and 8kg[inc cables and controller]) the heaviest part becomes the lower frame at 11.5kg - if the footrest is unbolted it is likely to become around 10kg.
If the lower frame was re-manufactured without the extra bits of weld that was added due to it essentially being used as a welding practice project it would likely be 10kg including the footrest.
The lower frame will be re-manufactured once the rest of the project has been completed.

The reason I've chosen 10kg as a maximum mass is because that is the maximum mass that should be lifted from the height of the chair (as it is dismantled) to the approximate height of a car boot (assuming the car boot is between knuckle and elbow height) for a woman according to the recommendations of the HSE (Health and Safety Executive) http://www.hse.gov.uk/pubns/indg143.pdf (page 8). For a man the relevant mass is 15kg.
For anything above 10kg (15kg for a man) it is recommended that a more detailed Health and Safety Assessment is carried out.

A maximum mass of 10kg should be achievable (although new batteries will need to be purchased).

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Mon Jul 13, 2015 4:30 pm

Lessons learned etc:

Some parts on the chair didn't work out as well as hoped:

1) The motors had more movement than I liked because of the quick release blocks and as I wasn't using them to dismantle the chair I have removed them and attached the motors directly to the frame. I'm not sure if it was a design issue or the way I made them - although I think there were issues with both.
2) I don't believe the motors are designed to be used in the vertical configuration and I've had some issues with leaking oil and one of the motors making noise.
3) The top plate of each of the front forks is made from 3mm steel, which is too thin (I should have used 5mm) and I've had problems with it bending, although because there is a lot of clearance around the front wheels it hasn't caused any problems.
4) The retractable footrest as originally designed wasn't supported well enough and eventually one of the welds at the bottom broke, I re-welded it and also welded the two rods together at the top (where the nuts are), this made it a lot stronger and I've not had any problems with it since.

I've now made a back rest and back rest brackets, I also used the backrest material from a donor chair (which includes a large pocket at the back held shut with velcro).

The original blue bag is now tucked under the seat at the front and provides quite a lot of storage.

I've made a ramp that I hang off the arm of the chair, which is useful where there isn't any disabled access - I'll try to get some drawings done for the website.

At some point I'll cut off the foot rest and re-weld it without the retractable part, so as to not impinge on the storage space at the front - although the retractable bit does work I haven't found it particularly useful as my feet overhang the front of the footrest.

I've made a couple of aluminium battery boxes each holding 8 Headway LifePo4 40152S 15Ah cells which are temporarily hung just under the seat - I still need to make a steel frame attached to the underside of the seat to support them.

Because the standard wheelchair motors get very hot when used for more than a short period and are not really powerful enough I have purchased a couple of 750W 24V 4 Pole industrial motors (similar to the attached image), which I imported direct from China, these are designed to run 8 hours a day 365 days a year - so should never overheat with the use I'll be putting them through.

I also tend to get wheel-spin on uneven surfaces and so have decided to add suspension which should increase traction.

The new version will have one motor in the vertical configuration and the other sticking forward at a slight upward angle - the motors will overlap with each other, but even so the overall width will need to be increased by approx 1cm.

The way the new lower frame will be dismantled is using two sizes of box section with one sliding inside the other one in front and one behind the motors (the motors will act as part of the frame), then the vertical motor's gearbox will be attached to the front section via a pair of box section pieces which will slide inside another pair, which in turn will be welded to some large box section which will attach to the inner bolt of a pair of large bearings centrally located near the front of the chair, the outside housing of which will be attached to the front section of the frame. At the back will be a pair of spring/shock absorbers (normally used on mountain bikes) attached to the bottom of the seat, the bottom of the shock absorbers will be joined to a cross bracket which will drop into square section pieces attached to the rear motors.

Because of the size of the new motors the motor/wheel assemblies will unfortunately be more than 10kg each.

I've got more or less all of the bits to re-engineer the chair, however it will take me months to get it sorted out, I'll try to get some drawings and photos to update the webpage some more.

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Re: Electric Wheelchair Design "hyperchair"

Post by admintrev » Mon Jul 13, 2015 8:45 pm

As the weight of all of the parts of my new design of chair (apart from the motor/wheel assemblies) is well under 10kg it wouldn't be too hard to have that as a maximum weight.
This could be achieved by using a spanner to remove the single centre nut from each axle to separate the wheels from the motors for transport.
The wheels are on keyed shafts, so the nut on each wheel doesn't need to be tight and so could be easily removed for transport, the only caveat is that the keys would need to be locktighted onto the shafts to ensure they don't fall out during transport.
Another option would be to look at the circlips at the other end of the axle shafts - using some larger and more easily removable circlips may be an option

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