Rebuild BM2 green...

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Re: Rebuild BM2 green...

Postby Burgerman » 21 Nov 2015, 20:21

Next job. Making the powerchair RELIABLE!

Stock powerchair motor couplings, on most powerchair motors, or rubber cush drives if you prefer, fail with monotonous regularity. As soon as you fit decent low resistance batteries (throw away those gels), fit decent wiring, and program the chair to turn, stop, and go.

I have a draw full of these failed ones. From 3 different motor manufacturers. It feels like a gearbox failure, but in reality its a £2 part... Most are similar. What happens is that suddenly you put some real torque through them. And the outside case splits, jams under load as it expands.

I fix these now BEFORE they can fail.

The problem: (Good one on the right...)
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Nov 2015, 20:23

The fix.

EBay for a short bit of stainless steel or steel tube. The CORRECT size so it is a push fit (with a hammer) over the weak cush drive. And cut a few 11mm long slices. That virgin cush drive is from my brand new motors.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Nov 2015, 20:25

Put cut tube over the cush drive, after coating in 5 min epoxy, and tap on with a hammer...
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Nov 2015, 20:26

Once set, file the sharp edges off, and refit!

I have not done either of those here! Yet.

Now it cannot fail. I win.
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Re: Rebuild BM2 green...

Postby hank » 21 Nov 2015, 21:40

Burgerman wrote:Don't remember where... Maybe here? http://www.minibikecraze.co.uk/shop/mad ... 0-10-tire/ The 4 inch wide rims open them out wider.

But UK.

Remember that these are bigger overall diameter, so are going to raise your chairs rear end... Unless you modify things. Not sure how well it will work out yet.


Thanks John.
Will ring them Monday. Only 20mins away from ours. 8-)
f55s bm1 clone.
quickie groove Brushless
BM3 clone
Foldawheel PW 1000 XL.
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Re: Rebuild BM2 green...

Postby Burgerman » 25 Nov 2015, 15:56

Image

And another!
This is a destroyed cush drive and some friends from my draw from years ago.
When did you last check yours :D :roll:

Image

Pushed together in the vice. Before filing.

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Re: Rebuild BM2 green...

Postby Burgerman » 19 Dec 2015, 14:32

Cush drives installed.

And now motors fitted...

The snot green chair is growing on me... And yes tyres are backwards. Temporarily fitted. The wheels need swapping left/right. After they are polished.

810_1042.JPG

810_1041.JPG

810_1040.jpg
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Re: Rebuild BM2 green...

Postby Burgerman » 19 Dec 2015, 15:34

To lightly load the caster stem bearings, on any chair should you get caster shake issues, I always fit these: http://www.ebay.co.uk/itm/A2-Stainless- ... 8716ca83b2

Larger one at bottom, and smaller one on top. Then you can use a NYLOCK nut, and tighten until the casters are just slightly stiff to turn. Grease them. This allows for things to bed in and wear in, but still never get loose and free. The bendy spring washer takes up any slack and maintains a lightly loaded bearing top and bottom.
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Re: Rebuild BM2 green...

Postby hank » 19 Dec 2015, 16:19

John did you decide on a seat setup ;)
f55s bm1 clone.
quickie groove Brushless
BM3 clone
Foldawheel PW 1000 XL.
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Re: Rebuild BM2 green...

Postby Burgerman » 19 Dec 2015, 16:31

No. But will probably just do the usual basic setup, sling back, my cushion. Not pretty but its very practical for me compared to messing about with race car seats etc..

You wouldn't believe this is the same chair that has seen and lived through huge dog walking sessions, winter roads, a dozen sets of motors, 5 different rebuilds, 5 different types of rear wheels, 7 different types of tyres and boxes of front caster tyres, and at least 10 sets of lead brick batteries.

If you rebuild literally as new, they *are* new. No reused bolts, rose joints, paint, loom, arm tops, uprights, footplates, bearings, upholstery, etc. Any part that is subject to wear is replaced. And part that doesn't look new is replaced, re powder coated. Anything subject to corrosion or failure is replaced with stainless steel, or blasted, repolished or strengthened or redesigned for reliability. Result is better than any new chair for 1/3rd the cost but 10x the effort.
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Re: Rebuild BM2 green...

Postby hank » 19 Dec 2015, 16:53

:lol: Looking good.Like a race chair on steroids 8-)
f55s bm1 clone.
quickie groove Brushless
BM3 clone
Foldawheel PW 1000 XL.
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Re: Rebuild BM2 green...

Postby Burgerman » 19 Dec 2015, 17:29

Its amazing what a set of wheels and tyres and a lithium battery and a quick rebuild can do. But it wont be fast. I lengthened it 10mm to account for a lighter 120Ah lithium, and my heavier weight -- Also seat 10mm further forwards. Both to compensate for its higher C of G :oops: Or it will shake casters and tip me out.

Instead I am going for silly range. 120Ah lithium (usable) to replace its stick 56Ah Sonnenschein gel (or my 68Ah Odyssey). (about 30 to 40Ah usable)

Slightly higher nominal voltage, (25.6 instead of 24) and a goof couple of volts less voltage drop under load in use, along with bigger diameter rims/tyres will mean 6.2mph is now about 7mph. But more importantly these 6 ply scooter tyres have a lower rolling resistance than the typical 14 inch powerchair wheels/tyres.

So this, along with the 50lb weight loss, of the battery alone, and the 50+ lb weight loss of the chair itself, means better miles per Ah too.

Maybe 10% better per Ah. So I expect around a 3.5 to 4x range increase over the stock F55 chair and its motors. We will see.
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Re: Rebuild BM2 green...

Postby Burgerman » 20 Dec 2015, 17:18

810_1046.JPG


Front wheel now polished alloy to match the rear wheels. Sat in approx. correct place with a long thin screwdriver as axle...
I spent this morning polishing the metal caster wheels. :shock:
They were old, powder coated, and corroded and dull. All I can say is my fingers now hurt!
And I will regret it in the long run as they will corrode and go dull again so will need repolishing periodically. That's why I normally powder coat everything. But this chair is supposed to look pretty too.

Note the night bags dumped on the floor! :oops:

810_1047.JPG


Distorted and shortened because of camera being too close and high up. and because I made a mistake resizing it I think! This makes it look short and wheels not round...

810_1049.JPG


The other wheel, also polished. Needs stainless round head Allen bolts (if I don't countersink the bolts), and a black or alloy valve cap. And rebalancing - not that it matters much on a slow chair, but I feel better having it right. A 14 year old wheel "rejuvenated"!
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Re: Rebuild BM2 green...

Postby shirley_hkg » 21 Dec 2015, 02:27

Be nice to yourself, add tilt/recliner to chair.

You will benefit from it and love it. :)
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Dec 2015, 13:40

No. Too heavy, too much extra mass high up, reduces stability, mean too high seating, etc. If I wanted that I would make the base longer, more nose heavy, and with a lot more weight lower down. But this ruins its light "feel" and performance.

And I tried tilt and still have it on one chair since it does not add much weight, height etc. But don't actually use it -- too slow. Its faster just to wheelie and tip it back onto its anti tips wheels while stationary -- say in the pub while I drink...

And I tried a riser. Some F55 chairs have them stock. I bought an old one with this fitted. On my shorter, lighter, narrower chairs with rearward CG, It causes all the problems I mention above. Although can be useful at times. But I am not prepared to add all the weight or raise the CG. Rather have a faster turning, more nimble chair that is closer to a typical sport manual chair. If I ever add a riser again, I will do a different chair. Or just buy a typical overweight one such as the Sunrise R2 http://www.sunrisemedical.co.uk/powered ... rs/jive-r2

But I tested one of those a year ago. Compared to my pared down shorter, lighter chairs, it felt like a bus. Horribly "big" and sluggish. So only for the days where I need the height to wash my van or similar. I have considered that.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Dec 2015, 13:51

For anyone wondering what the corner of my bedroom where I build chairs looks like, heres a pic!
Note fire extinguisher, and my bench drill now is floor standing. (I bought a stainless steel 60mm pipe...)
And an old lathe, toolbox, vice, drills, saws, metals, tyres (at the top) etc.
There is more along the bench on the left you cant see, for parts, soldering, working on stuff. And mostly I use my bed as a table!

Seriously this is way more than you need. Most stuff can be farmed out either online or local machine shops.

Boxes on left contain 80 lithium cells. White stuff, still packaged on the right, is freshly powder coated parts - waiting to go back together.
This is a minor redesign/tweak to one of my old BM2 chairs. It now has bigger rims, 120Ah lithium battery, and a new colour and a new everything that can wear or that isn't as new. Nothing fancy, I just don't like old/unreliable/tatty looking chairs! This one is a full time workhorse from 97...
download/file.php?id=4162&mode=view

Once you build one of these or something that suits YOU then a "rebuild" every few years is simple. Just a case of blasting and re-powder coating every metal part. New motors, tyres, rims in this case, rose joints, bolts, upholstery, and bolting it all back together. Making any improvements that either allowed you to break down, or to allow it to work better than previously as you go.
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Re: Rebuild BM2 green...

Postby JJ1212 » 21 Dec 2015, 18:23

Why make this one not as fast as your current one?
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Re: Rebuild BM2 green...

Postby JJ1212 » 21 Dec 2015, 18:38

& it looks very nice, the black on green really has a nice contrast, really pops.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Dec 2015, 19:16

Its just a quick cheap refresh for a daily runner. Changing to roboteq, different motors, new complex loom, makes for many more £££ and time... Next chair will be roboteq and higher voltage etc. This one uses shorter geared new motors (that I already had), and now has lower rolling resistance tyres of larger diameter, for stupid range @ 7mph with its new 120Ah lithium battery... Its no racing chair, but will be built to last many years, with absolute attention to detail, stainless bearings, tubeless rubber, strengthened cush drives, better quality loom, etc. Its not for playing but reliable long term service and daft range.

I have a 16mph chair. This one will go further per Ah. But slower. And will look cool.

The next one will probably use four HD 4MPH motors be 4x4 and use 45 volts so that I have simply tons of torque, and adequate range even with skid steer. And still be 8mph because of the doubled voltage and 150A per channel. All good! Different chairs for different jobs.
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Re: Rebuild BM2 green...

Postby Burgerman » 28 Dec 2015, 15:05

I have had 3 emails, and 2 questions on tis board asking why I don't use 8.5mph motors on this chair.

I am looking to maximise range on this chair above all else. That means 6mph motors, since these take about 20% less Amps from the battery at all times and speeds. That means 20% better range. For the same reason I fitted bigger diameter low profile radial rubber tyres. Low rolling resistance. Again saving battery power over a typical fat tyre and over a typical powerchairs 14 inch tyre.

This F55 chair (at least its motors! - not much left of the rest of it) has an ISO range figure of 25 miles with 56Ah Sonnenschein Gel batteries. That's about 37Ah usable till it completely stops.

My modified version has 120Ah usable lithium. Or some 3.25x more battery power. It also has:
-Less rolling resistance
-120lb less weight
-Less wasted power for turning as the CG is much further back.

So these three things add an unknown amount. Lets call it 10% (although its probably nearer 25 in reality) Actually it should be better still as voltage is also increased slightly so Ah used decreases.

So 3.25 + 3.6 (rounded up v.slightly)

So that should give me the original ISO x 3.6 = 90 miles! Now we know that the ISO test isn't realistic. A 25 mile chair typically dies at about 15 miles. So it will be around 50 to 55 miles actual range. Then after an Ah per mile test measured around my town, to be sure, I can go on long slow days out!
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