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Forum Index : Electronics : SImplest way to use a GTI in stand-alone mode
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| rogerdw Guru  Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks Mark, I was able to get a utility knife in one corner ... but it broke off after a very short while. I will harrass that corner again with your method. I just happened to fluke coming across one of Oztules later threads and he mentioned using a 50 ton brake press to get it off. That's something I don't have, but I'll work something out. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yes, I was surprised about the lack of batteries on offer the last time I looked. I had occasionally looked on eBay and on Gumtree ... and there was always something. I can only suggest trying what I did ... just go to your local fork lift dealer/repairer and ask questions. I was amazed at all the old batteries he had lying around. It probably helped that I know him ... but it's easy to build a relationship with good people. In fact, the first time I visited him several years ago, he gave me an old faulty Power Star inverter ... 2kW, but only 12V I'm afraid. As I mentioned previously, when a fork lift comes back in at the end of a lease ... they fit new batteries before they re-lease it ... so the new owner can be confident he's getting good value. I'm happy to take a punt on some 2 or 3 year old batteries, especially at the price he's talking about. The ones he showed me were about the size of a twin tub washing machine ... a heap of cells contained in a solid steel, open topped box ... with lifting points on the top edge. No question they are going to be heavy ... so I'll have to be ready for them so I don't have to shift them again. The inverter graveyard I visited had a heap of only about a dozen old GTI's ... so I was surprised they had 4 AeroSharp's amongst them. Apparently they had only recently taken out a big heap for recycling ... so I was lucky. I know I should have scrounged through to see what all the others were ... but I didn't want to wear out my welcome or for some reason have them change their mind. When I first rang, the girl in the office was happy to go look what they had lying around ... and almost apologetically told me they sell them for $25 each. Bargain! I'm certain there were only GTI's in the heap ... didn't look like any other shaped inverters there. I found them online when I spotted a couple inverter repair places in Adelaide. I don't know that they actually do repair any ... it may just be an excellent sales angle for attracting people with crook inverters ... and then just sell and fit a new one. There has to be businesses all over Australia that would see these things on a regular basis. Just need to get on the phone and make some calls. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
I'll try that method of getting it out next time, thanks. I did try the multigrips process for twisting off the epoxy lump ... but couldn't shift it. I'll certainly hang onto the rest of the bits ... too good to throw away.  Cheers, Roger |
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Murphy's friend Guru Joined: 04/10/2019 Location: AustraliaPosts: 648 |
Using *anything* metal to prize it off will mark the heat sink. I used wooden wedges (hardwood works better) made from offcuts. About 3 are required. First find a corner where there is a slight gap and hammer a wedge in a bit. Hammer another next to it, you see the gap opening ahead of it. Hammer the third wedge in, by that time the first one will be loose so pull it out and keep working at along just one long side of the heat sink. That Sikaflex type material makes a strong but flexible glue that can only really be 'peeled' apart. So use that idea, once you have the long side off inserting a wedge at each of the short sides 'peels' the heatsink off. Now you still have to get that goo off the heatsink surface. I use a relatively blunt 19 or 25mm chisel that has the corners rounded off so they won't bite into the alu. Carefully scraping, holding the thing at just the right angle, will clean it off with no marks at all. That job gets easier with each following Aerosharp wrecking  . |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Thanks Murph, I did get it off pretty easily in the end ... starting from the corner that had a tiny gap, I gently pressed in a wide chisel to put a bit of pressure on it ... then I used a putty knife to keep sliding in and pushing through the glue ... then swivel it sideways to cut through some more. Worked my way all around and it was off. I like the idea of a hardwood wedges, would be less chance of scratching the aluminium. I'll do that with the next one. Thanks. Cheers, Roger |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Just a question ... I've unwound the first layer of the 3kW AeroSharp torroid ... very messy and tangled in places ... but got it off ok. For the 2nd half of top layer ... do I unwind it 3 at a time the way it was wound ... or do I cut the join and unwind them separately? The mylar tape was fairly stretched and crinkled everywhere ... but I found by anchoring one end and applying pressure and heat from a hot air gun ... it shrunk back and into shape remarkably well. Just have to do the rest now. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
If it goes around the toriod more than once, its obviously not going to be possible to unwind it one strand at a time. Unless you have the luck of the Irish, its probably going to have to come off the way it went on. Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Makes sense. I was surprised at how many places it was overlapped and difficult to unwind without lots of jiggling and straining. Probably more to do with the auto winding of the original I suppose. With the first section, I very quickly ended up cutting the joiner off and unwound each strand bit by bit ... as far as it would go ... then tackle the next strand. I was gentle with it ... but still nervous about re-using it ... that enamel must be good stuff! Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
The easiest way to tackle this job, is to wind the wire lengthwise around a fairly long piece of wood with very deep notches cut into the ends. Its best not to cut the wire unless absolutely necessary. Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Yes, the long pieces of wood worked well ... it was just the tangles that worried me. This next section is coming off much more easily. Thanks.  Cheers, Roger |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 513 |
Make sure you recycle the scrap copper, if you get a good place its considered " burnt copper " and its about 6 bucks a kilo.. easy to get a few kg, i stripped 4 and just the leftovers after rewinding i got 90 odd bucks back.. although they did cost a heck of a lot more than that, its still better than a kick in the guts.. I think it works !! |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Wow, that sounds worthwhile. You've never had any trouble when re-using it? I'm just nervous about any scratches or nicks causing shorted turns ... especially at 240V. Cheers, Roger |
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| noneyabussiness Guru Joined: 31/07/2017 Location: AustraliaPosts: 513 |
Ive had no dramas on the 2 ive done, and they are not neat by any description, I think the legend oztules wrote a very desciptive tutorial on it somewhere here.. just be as careful as possible, but its pretty tough stuff at the same time. He puts epoxy on each layer to protect it better... I think it works !! |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
There is only going to be typically about one volt between adjacent turns anyway, and unless the damage is outrageously bad (obvious), there should not be any problems in recycling the wire. If you think $6 per Kg scrap value is high, just wait until you get a quote for new replacement wire. If you were in the trade, and buy wholesale in bulk, its like $1,900 for a 100Kg drum without GST. If you are Joe public, and wander into a transformer winding business, and ask for a few miserable Kg, the best you will probably be able to get it for might be about $25 a Kilo, and probably more if they don't like the look of you. Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
That's encouraging. Just seeing how time consuming it is to unwind one, gives me some idea how hard it will be to actually wind one. Won't want to do it any more times than I absolutely have to. Again, that is encouraging to be able to re-use the wire ... thanks. I'm not sure where to buy new stuff over here nowadays (South Aus). I used to buy it from OH O'Briens and also Warburton Franki (I think) ... but that was 30 - 40 years ago. Some phone calls needed I guess. I recall that 2 - 2.5kg used to cost me $50+ back then ... so I'm surprised it's only $25/kg now. They obviously didn't like the look of me back then ... could be even worse now.  I used to modify lighting systems on dirt bikes for competition work as a sideline. Probably wound a thousand or more coils ... but the simple formers they used were very easy. It was the winding and rewinding to get the best output at the right revs range that was the tricky bit. As I always needed heavier wire ... I don't recall ever re-using any ... I assumed it was too much risk anyway. The later ones were more of a challenge ... the radial ones ... smaller versions of the F&P Smart Motors ... thick heavy wire and lots of sharp edges just waiting to catch you out. One of the poles was used for ignition and was many (can't remember) turns of .125mm. Actually made a machine to wind it ... and worked very well ... but did a lot by hand before I went to that trouble. Cheers, Roger |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
I used to buy my wire from O'Briens in Melbourne as well, around the same time period too. Back then I had a transformer manufacturing business. These days I buy wire from a mate that lets me have it for trade price, which is what I based the above figures on. Just about everyone here recycles their wire, including me. So hang on to what you have there, it will definitely come in useful eventually if not right now. Regarding heavier wire. What the guys here usually do, is put on multiple layers, then parallel the finished windings. Most of the grid tie inverters use 1.6, 1.8 or 2.0mm wire which can often work out rather well when you work out the details of your new design. Anything much heavier is just too difficult to handle anyway. Cheers, Tony. |
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| rogerdw Guru Joined: 22/10/2019 Location: AustraliaPosts: 852 |
Good to hear all that, thanks. I never throw anything away, so I'll certainly keep it. I've still got a box full of various size enameled copper wire ... but most are getting low ... and the biggest I have is 1.8mm, but only about 1kg left. I certainly remember it being painful to use ... trying to form it into shape with my thumbs.  Cheers, Roger |
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| Davo99 Guru Joined: 03/06/2019 Location: AustraliaPosts: 1578 |
Wrong section Edited 2019-11-15 13:53 by Davo99 |
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