Rebuild BM2 green...

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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 20:11

And so far, we have 36 done!!!

These are 36, from the total 82 (84 since I got 2 extra just in case).
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Re: Rebuild BM2 green...

Postby Burgerman » 09 Oct 2015, 13:12

Once all 84 are done, then I will fit wheels to motors, motors to base, and start adding the rest... All ready to go, re powder coated and wrapped in bubble wrap. New motors will get modified cush drive rubber/motor coupling, as these fail.

Why is it important? Because these are known to fail on EMD motors with 100A controller with Lead 24V batteries. And lead batteries are not really 24V under heavy load they fall to around 18 to 20 volts as you wheelie etc.

The Lithium batteries barely drop voltage at all under load, maybe 1 V worst case, and they start off with a nominal 25.6V (3.2V per cell.) But that's misleading. Because they drop from 3.4 to 3.6V in the first few yards, then sit at 3.32x Volts or more for a lot of the day before finally dropping fast to about 2.5V right at the end. So most of the day you have more like is in fact a bit more like 26.x Volts. So those drive coupling have to take a bit more torque than they do with Lead bricks. It also means that there's a small speed increase as many of you using Lithium already noticed, and even more so up hills etc. So a 6.2mph chair may now do 6.4 to 6.5mph.
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Re: Rebuild BM2 green...

Postby flagman1776 » 09 Oct 2015, 16:23

Burgerman, Is there a link tp how you re-engineered the cush drive? The proven fix of known problems... already failed once! Is the great leap forward in every custom build.
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Re: Rebuild BM2 green...

Postby Burgerman » 09 Oct 2015, 16:31

Well I posted here somewhere!

But no clue how to find it now.
But its simple. The rubber crushes up, tries to expand. It then expands the outer metal shel, and it splits, and you stop... I just ordered some steel tubing from ebay, of the correct diameter so that it was a push fit over the whole thing. And cut a slice the same width as the cush drive. Push them together in a vice, and you are done.

Before it gets chance to do this!
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Re: Rebuild BM2 green...

Postby flagman1776 » 09 Oct 2015, 17:35

Thanks. 1 picture worth 1000 words. Nice job. So much better to reinforce it before it leaves you stranded somewhere.

I have repaired an (unavailable replacement) plastic control knob on my RV water system with a pressed on metal collar... also the blend door control on my Dodge pickup... are prone to splitting. I also use the drill press quill as an arbor press sometimes.
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Re: Rebuild BM2 green...

Postby ex-Gooserider » 13 Oct 2015, 05:21

hank wrote:What grade of ally John for discs is it.? Dural


If it's aluminum, and you don't specify a different alloy, its about 95% probable that you will end up with 6061-T6. That is by far the most common aluminum alloy, and generally it's a pretty good choice, as it is good to excellent in pretty much all important respects.... There are other alloys that may be better in one way or another, but they generally aren't as good in the rest, and are more expensive...

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Re: Rebuild BM2 green...

Postby ex-Gooserider » 13 Oct 2015, 05:31

I can understand why you need to do the recharge test on the cells individually, but why not make a fixture to charge serial groups of cells for the original charge that you use to get them all to the same starting point?

Also, if you have to get the individual cells shipped with that sort of packaging, would it be possible to ship an assembled pack as a unit?

(I.e would it be practical to offer to build packs for others and ship them finished packs as a semi-drop in unit?)

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Re: Rebuild BM2 green...

Postby LROBBINS » 13 Oct 2015, 08:18

European (near) equivalent of 6061 goes by a different number - my fallible memory says 6082. Very slight difference in chemistry, but the same mechanical properties. Not the absolute strongest alloy, but pretty tough stuff (not very different from A2 stainless) and readily available. TIG welds nicely, but loses temper along the weld line (as someone here reminded me long ago) so for stressed parts needs to be heat treated after welding.\
Ciao,
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Re: Rebuild BM2 green...

Postby Burgerman » 13 Oct 2015, 09:38

(I.e would it be practical to offer to build packs for others and ship them finished packs as a semi-drop in unit?)


Yes. But much time and effort. And it seems to me that its far better for people going lithium in these non plug and play days, to do it themselves so that they understand the charger, the cells, the wiring and connections, and the why/how of it all or it will all just end badly regardless through ignorance. Its not that its complicated, its not. But you must understand it, and how its working, and so be able to monitor/fix things in the event of some issue to keep on top. Its easy if you know, its impossible if "someone else" did it all for you.
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Re: Rebuild BM2 green...

Postby Burgerman » 13 Oct 2015, 12:11

TIG welds nicely, but loses temper along the weld line (as someone here reminded me long ago) so for stressed parts needs to be heat treated after welding.\


It also just naturally re naturalises and hardens with time and temperature changes. In the same way that an annealed bit of copper is really soft and easy to bend, but 2 weeks later its as hard as a rock. So I wouldn't worry unduly about this stuff in a powerchair. Remember those alloy frames I linked to by my friend Mark? All they do is warm with a gas torch after welding to take out the shrinkage stresses after the weld cools. And wait for them to harden over the next week or two.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 13:43

This is what my bed looks like today...
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 13:45

Another... Making wheel adapters with a pointed bolt, 3 G cramps, some 120mm x 8mm alloy laser cut discs, and the olde worlde taperlocks from the BM2 before I pulled it apart!
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 13:46

This is just propped in place. Frame will miss the wheel by 10mm when fitted properly. And centre disk will have 4x M8 countersunk bolts, and be polished like a mirror...
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 13:48

Another
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 15:07

.
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Re: Rebuild BM2 green...

Postby hank » 21 Oct 2015, 16:40

Looking good.
Getting there now. ;)
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 17:01

Yes. Currently drilling carefully marked holes in the round plates. Carefully! Marked the bolt circle diameters in my lath,
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Re: Rebuild BM2 green...

Postby hank » 21 Oct 2015, 17:16

John your reason to use these wheels?
Is it for less drag more distance.Easier to fit than using hegar wheels -turf tyres.
Sorry to hear loss of your dog. Was that why you switched to this setup now not
going off road now.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 17:53

Several reasons.
When rebuilding a BM2 that has survived hell and 3 previous rebuilds I decided to make a cheap chair that looks cool for going to the pub or whatever if needed. But mostly as spare chair. A cheap rebuild. All old 100A controller etc. But built for reliability, daft range, and looking cool.

So I went kawasaki green because I like the colour, low profile tubeless but very wide tyres because the alloys look cool the rims are light and tubeless, and because I wanted a larger rolling radius to give an easy ride. Easier to roll too for distance, (6 ply, strong tyre, bigger diameter, tubeless but still curved slightly even though its fitted to a too wide rim, so less power wasted on turning etc). And I want huge range so it is getting a 120Ah 8S headway 25.6v battery. Mostly because I cant bring myself to buy another hopeless lead brick... Its just wasted.

Total rebuild from scratch with lithium (almost 4x bigger range than lead) and new upholstery, tyres, bearings, loom, footplate, wheels, tyres, puncture fluid, bolts, motors, etc is approx:

1200 battery and loom
600 motors
160 wheels/tyres
100 footplate, upholstery, bolts
120 powder coat all parts.
+ the old f55 frame or parts.
£2180 total???

Lets call it £3000 if you were starting from scratch, needed a scrap F55 frame, seat frame, control system, lithium charger sertup etc to start, and needed to get a centre section, bars etc all made up.

At that it will be basically better than any new chair. With 4x the range and a 10 year battery life. Its rude not to do it.
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Re: Rebuild BM2 green...

Postby hank » 21 Oct 2015, 19:38

Bit of a dilemma.?
Using f55 4pole motors.odysseys.100amp PM.in My BM1clone.
Got Hegar rims and Kevlar Turf tyres.For a BM2-Bm3 clone.
With lead would i be better Buying wheels and Tyres like your latest ones.
Or use Hegars-Tyres i have. Would there be much Advantage in battery drain
on tarmac use mainly to switch.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 20:27

The turf tyres are wide.
They can run at 5psi and give lots of comfort, floatation, and so on, and they eat batteries mostly while turning left/right indoors fast. Outdoors, mostly in straight lines like footpaths its not a problem. Esp if you have the pressures at a higher level. Swings and roundabouts...

The tyres I have now, are bigger diameter by about 2 inches. So you could try those - depending on how you built your chair. They will eat less battery power, and should offer reasonable comfort, but ride height will increase. Again I don't really know until I try it! Maybe too big, maybe horrid ride... Dunno yet! I like experimenting. Its why I have 4 chairs...

You MAY be better off with some wider 8 inch rims with say 130/70 8 tyres. Its more "normal", and had more sidewall.
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Re: Rebuild BM2 green...

Postby hank » 21 Oct 2015, 20:45

Cheers John for your advice.Will look on tyre availibility for 8 inch rims first.
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Re: Rebuild BM2 green...

Postby Burgerman » 21 Oct 2015, 22:41

DURO TUBELESS 120/70 8 on a 3.5 wide inch rim should be about right...

http://www.shirebikes.co.uk/products/12 ... eless-tyre
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Re: Rebuild BM2 green...

Postby hank » 22 Oct 2015, 09:18

Cheers for link. ;)
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Re: Rebuild BM2 green...

Postby Burgerman » 22 Oct 2015, 09:39

Fitted on 3.5 rim. 4may be better, will stretch it out. Problem is finding a tubeless rim.
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Re: Rebuild BM2 green...

Postby hank » 22 Oct 2015, 09:56

Pity they dont do a 4 inch rim. Would look better.
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Re: Rebuild BM2 green...

Postby nandol » 22 Oct 2015, 20:08

[quote="Burgerman"]DURO TUBELESS 120/70 8 on a 3.5 wide inch rim should be about right...

http://www.shirebikes.co.uk/products/12 ... eless-tyre[/quo

John,not so long ago I put you the question is we could put 8 inch rims in our power chairs~,and you`ve sayd " well if it was possible i had it already..."
seems that I was right at the time,and yes in fact it is possible ;)
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Re: Rebuild BM2 green...

Postby Burgerman » 22 Oct 2015, 20:56

They have 8 inch rims when you buy them. Almost all new stock chairs?
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Re: Rebuild BM2 green...

Postby Burgerman » 26 Oct 2015, 15:45

Wheel adapter plates, are:
120mm by 8mm thick laser cut alloy disks. (online).

These are bolted to the old BM2 taperlock pulley adapter designed for the quad bike rims... So an adapter on an adapter!

These are to be drilled with 4x M8 threaded holes for the wheel bolts.

This was drilled by measuring, by hand, in my vice and countersunk on my bed!
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Re: Rebuild BM2 green...

Postby Burgerman » 26 Oct 2015, 16:23

But actual bolts used here will be high tensile ones, greased so they dont corrode. Because there are just 3 and high tensile are stronger. And I had some the right length!

These parts will be disassembled, countersunk by another 1mm, tidied up, painted/polished etc as required, and will never be seen! Covered by the wheel. Spacers are alloy ebay skateboard wheel spacers.
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