Rebuild BM2 green...

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Re: Rebuild BM2 green...

Postby hank » 05 Oct 2015, 17:10

Lovely wheel choice. :ugeek:
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Re: Rebuild BM2 green...

Postby Burgerman » 05 Oct 2015, 17:29

Choosen because of, tubeless, and width, and offset (1 inch inboard). And price! And because that centre makes it easy to cut a 108mm disc with 4 holes and polished to finish off the centre.
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Re: Rebuild BM2 green...

Postby Burgerman » 06 Oct 2015, 20:27

http://www.lasermaster.co.uk/metal-laser-cutting

For those looking at these wheels and rims.
And I just ordered 4x 120mm aluminium disks, from above online. (see quick order on left.)

2 are 6mm thick, and will sit on the recess at the front after polishing with 4x wheel bolts visible.
2 are 8mm thick and will sit behind the wheel in the opposite recess, and these will be drilled to suit the old wheel adapters. And the 3 existing bolts for the old rims, hidden. So it will all look pretty.
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Re: Rebuild BM2 green...

Postby hank » 06 Oct 2015, 21:14

What grade of ally John for discs is it.? Dural
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Re: Rebuild BM2 green...

Postby Burgerman » 06 Oct 2015, 21:32

No idea. As long as it polishes! Its 8mm plate, and more than strong enough as an adapter plate regardless of alloy. Unless its super, super, soft... Even if it is, it will just deform.
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Re: Rebuild BM2 green...

Postby hank » 06 Oct 2015, 21:49

Like you say will polish up nice to match wheels :shock:
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Re: Rebuild BM2 green...

Postby Burgerman » 06 Oct 2015, 22:25

Why shocked? Dont worry it will be stronger than the rims or the output shaft!

Get a lump of 8mm alloy plate, the same size as a CD, and try bending it. You will be convinced very quickly!
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Re: Rebuild BM2 green...

Postby hank » 07 Oct 2015, 08:53

Did not think of it like that John.Like you say could not bend it on a 8mm cd size alloy disc. ;)
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Re: Rebuild BM2 green...

Postby Burgerman » 07 Oct 2015, 09:26

Get a lump of 8mm alloy plate, the same size as a CD, and try bending it. You will be convinced very quickly!


Or look at the thin 1mm steel all terrain wheel rims, or at the 2mm thick hegar rim material.
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Re: Rebuild BM2 green...

Postby snaker » 07 Oct 2015, 10:16

Can you estimate the BM2's weight (the chair only, without batteries or human :P )?
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Re: Rebuild BM2 green...

Postby Burgerman » 07 Oct 2015, 12:48

Not really. But its a hell of a lot lighter than the original F55s chair it started life as.

viewtopic.php?f=2&t=5428
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 16:24

Tyres fitted to the over wide rim, and it fattens them up just right, makes them put more rubber on the ground, and allows a lower pressure to give some ride improvement, and they look great. This is a 130/60 on a 4" wide wheel. The wheel stood upright has also had a very quick 2 minute polish, and it already looks better...

These are 5 and a third inches wide. And 16 inches and a fraction total diameter. So not much taller than the 3.50/8 tyres. But about 1.5 inches taller than the turf or 145/70 all terrain tyres.
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Re: Rebuild BM2 green...

Postby hank » 08 Oct 2015, 16:29

Want them. :D
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 16:50

This isn't inflated, and it isn't polished yet. Just put 400cc of tyre "off road" sealer in, and replaced the valve core... Punctures are not going to happen.

Tubeless tyres don't puncture easily. Especially lightly loaded low pressure wide ones. Especially 6 ply ones! And if they do then they don't deflate normally anyway. And just in case I have added a lot of the best off road sealer I know of!

OKO off road. http://www.amazon.co.uk/Off-Road-Tyre-S ... B006THGZZ2

This stuff seals massive holes. http://www.oko.com/videos/
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Re: Rebuild BM2 green...

Postby hank » 08 Oct 2015, 16:56

John did you have tyres fitted. Or you used tyre levers.
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 17:57

Took them to my local motorcycle shop. Its too hard to do tubeless 6 ply low profile tyres in a wheelchair... I let them do it on a machine.

Here's another pic, boxes of lithium cells, motors, bubble wrapped parts in the background, wheels, tyres, in the corner of my room... Expensive pile of bits to make a 6mph chair with ridiculous 4.3x as much range as a stock F55!
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 17:59

It just occurred to me that I may be a bit mad.

And may change it to roboteq while I am at it...

And that the 6.2 mph EMD motors with 14 inch wheels are now actually 7.1 mph motors with 16 inch tyres on.
A 14 percent increase in speed and a 14 percent decrease in torque.
So...
The 150A Roboteq will address that, with a huge 50 percent torque increase possible... Set to say 114A max it will be the same as before. And the Roboteq allows for full battery voltage too, so up from 22 from the lead/pilot plus, to 25.x from the lithium/Roboteq. Another 14% percent speed! So... That would now allow 8.1 mph. But at great expense... And much more work.
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 19:07

This build wont be doing anything ground breaking, its more for looks, and silly amounts of range.

It will look cool though!
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 19:59

OK. Turns to the Lithium cells. I ordered 84, will use 82.
They arrived tax free from www.evassemble.com via a well known US shipping company, in 5 days flat.
They arrived as 7 separate packages since shipping lithium is hazardous, with all the regulatory certificates etc.

Each package contained boxes with 2 cells in each. All were 3.371V (+/- 0.05) which means fully charged plus a month sitting around.

They arrive looking like this x 42 boxes:
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Re: Rebuild BM2 green...

Postby Burgerman » 08 Oct 2015, 20:09

Now, each individual cell is to be fully charged to 3.600V and sit at this CV voltage until its current falls to 20mA. At which point it then has 1000mA drained from it, and it goes into a pile in a box to wait for 1 month.

CHARGE 3.600V 5A
TERMINATION POINT 20mA.
REMOVE 1000mA exactly (at 5A Discharge)
STORE IN A BOX!

After 1 month, each will be fully charged once again, back to 3.600V and terminate at 20mA, and the actual mAh that was returned to each cell, (-1000) will be written on the cell in marker pen. This figure is the amount that the cell has SELF DISCHARGED (over and above the 1000mA we already removed) over the month.

This allows us to build 8 separate parallel groups, that have the same TOTAL self discharge, before assembling into the Series connected battery. It means that if we store the battery for a few months it will discharge each group at the same rate. So it will remain in balance.

2 at a time, takes FOREVER!
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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.\
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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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