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107G weight reduction
My attempt to reduce weight on my 107G so I can put a larger battery on it :-)
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Helgi Rudd
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November 30, 2012 - 4:52 pm

I recently bought a 107G... so much fun out of the box, but I couldn't help starting the process of modifying it, with the aim to reduce weight so I can replace the stock battery with a larger one!

 

Here's what it looks like so far.... ugly, but it fly's really well (so far). I've had quite a few crashes and it's still going strong.

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These are the parts I've removed so far...

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I'm planning on doing some more weight trimming:

  • Replace the remaining two aluminium plates with X shaped plastic supports I'm going to make from plastic similar to credit card plastic... minimal volume of plastic... just a simple X brace with the four screw holes.
  • Remove as much plastic from the black plastic 'tray' that the circuit board rests on.
  • Maybe attempt to reduce the weight in the gyro stabilizer

Hopefully I can put a 240mAh battery in a get a decent fly time :-)

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Syma Freak
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November 30, 2012 - 6:05 pm
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Good post and neat photos-CPD is always worth touching base with and Raptor as they are into lots of mods -link here http://syma107.com/forum/gener.....ndom-mods/

"Fly like a butterfly sting like a Syma" http://syma107.com

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CPD
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December 1, 2012 - 2:28 am

Just a few quick tips--make sure when you add the larger battery that wou add some weight to the rear of it so it's not too awefully nose heavy, or it'll just be a bullet and ram into your walls, and do something to hold the motors in place. The original frames have little tangs that hold them down, but if you don't have the upper frame on there, they can just pop out. (and trust me, that's not good at all to be flying, and have a motor just pop out of place)

 

Hope you have good luck with that! Keep us in touch!

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Helgi Rudd
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December 1, 2012 - 6:30 pm

Thanks for that link Syma Freak... so many amazing mods in there... getting into the guts of the electronics is some next level stuff, incredible!

Cheers CPD, I'm going to carefully put a tiny drop of super glue to hold the motors in place... since I've taken the top bracket off one of the motors has already popped out once! I'm still deciding what to do with the circuit board and battery after my recent modification (below). I had a thought about the battery... I have already ordered a few from eBay (which won't arrive for a while yet)... one order I placed was for two 150mAh batteries... I thought maybe what I could do is hook them up in parallel and place one either side of the core body... not at the front at all. I suppose with all the weight reductions I'm making I'll have to play with the weight balance.

I've had a go at modifying the undercarriage, quite pleased with the results so far. It seemed to me the main importance was to keep the original functionality provided by the black plastic 'tray' that the circuit board was mounted on... the part that the rotor spindle (terminology!? lol) drops into... it stops it from dropping down too far and the gear slipping below the drive gear.

 

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In the picture you can see the white plastic replacement I've installed... and in the foreground my first failed attempt

I'm awaiting delivery of a dremel tool to make life a bit easier, at the moment I'm working with a swiss army knife (I love the hole borer on it, I've drilled through all sorts of things with that!).

Anyway, this modification means I can do away with the remaining aluminium side plates, and the plastic tray underneath.

Next I'll decide what to do with the circuit board and the battery... and maybe add a few 'crash protection' features ;-)

For this modification I took a plastic card... like the plastic cards that go in a wallet. I carefully sliced a long even strip, then drilled a hole in the middle that was just the right fit for the protruding metal rotor spindle. From the middle of the center hole I lightly scored at 7mm on both sides then carefully bent in the direction away from the scores. The plastic sort of splits a bit when bent but there's a strong enough connection to finish the job and strengthen the bend at the end. Next I measured 30mm from the center hole in both directions and drilled the holes for the screws to go in. After screwing in I very carefully applied the smallest amount of super glue to the 90 degree bends... nice and strong.

There are other screw holes available on the mast, potential to save a tiny bit more weight, but without proper tools this was the best I could do.

edit: researching battery weights... I don't have scales to weigh, but eBay searching reveals 4.0g for 150mAh, 5.6g for the 240mAh batteries I have already bought... and 15g for 500mAh.  My gut feeling at the moment is that 2 x 240mAh batteries is going to be the way to go... then I can place one either side and have much more freedom to adjust weight balance. Pretty sure I can remove 11.2g of weight.... if I do that then I'll have the original stock weight but with 480mAh instead of 150mAh... more than three times the flight time!

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Helgi Rudd
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December 2, 2012 - 6:11 pm

I've built a rudimentary 'cradle' for the PC board... which also has legs to protect the bottom and allow landings.

When I get the Dremel tool I'm going to lighten this cradle significantly... still working with the 'credit card' plastic, which is PVC... one of the heavier plastics... it's very sturdy though... I'm planning on thinning the parts I've fabricated with the Dremel tool.

 

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Here's a picture of it all put together... for the moment I've just sticky taped the battery on the front.

 

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It looks a bit like a dragon fly :-)

Hover test at about 5 feet gave 11.5 minutes fly time. Still on the stock battery so pretty happy with that.

In this configuration it creeps backwards slowly... so it's tail heavy. I've ordered some carbon fibre tubing which will lighten up the tail end.

Still planning on strapping 240mAh batteries (wired in parallel) onto either side of the body.

It flys brilliantly still... very responsive and accurate.

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CPD
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December 3, 2012 - 5:52 am

Looks good. PVC's a good, strong material to use. Personally, I'm used to using Polystyrene that you get for modeling buildings, but that sounds like a good material to use. I wouldn't be suprised if it still is too heavy with two 240mah batteries, though. These little guys seem like they have a fair bit of lift, but they really don't.

Somebody really should try to find if there's any blades that will work on these things that have more lift. These blades are alright for a stock heli, but if you want to have anything heavier than stock, they're no good. (like if you want to put the guts of the heli into a plastic model of a different real heli)

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Helgi Rudd
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December 3, 2012 - 10:30 am

Polystyrene sounds great... do you buy that in sheets from a hobby store?

When I get some scales I'll be able to work out what the weight limits are... but if the stock 150mAh battery is 4g and the 240mAh is 5.6g then I need to remove only (2 x 5.6) - 4 = 7.2g  (I made a mistake in my previous calculation... forgot to subtract the weight of the stock battery I'm planning on removing).

I've come across posts on the internet of people getting the weight down to just over 18g (less than HALF the stock weight)... I only saw a picture of just over 20g though.

The stock weight is about 38g... so I would only need to get it down to 38 - 7.2 = 30.8g to end up with a version that has the same original weight but with 480mAh instead of 150mAh.

Replacing the blades seems like a great idea to me! I only have this 107G and a really bad rip-off version that inspired me to find something that actually flies properly! (hence I'm here playing around with 107G's :-) )

When I did that hover test I was surprise how cool the motors were at the end of it... I could barely detect any heat at all... would struggle to call them warm let alone hot.

Can't weight to get those scales... miss-spelling pun intended ;-)

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CPD
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December 3, 2012 - 4:47 pm

Yeah, depending on what your hobby shop does. None of the ones near me carry it, so I either have to go about an hour away if I wanted some or buy it online. (well, ok, I have a train shop by home and a train shop up by where I'm going to college, the hobby shop closed about 2006 because they weren't doing THAT great of buisness and the guy wanted to retire)

 

It's a low density plastic, and you use specialty glue on it that melts it, then welds it together. Very strong bond for models, and decent for these. One thing I like and would recomend, is save your little shavings and bits of scrap somewhere, because if you get a gap in your parts from a cut not being straight or need a slight shim, you can take the shavings, add a fair bit of cement to the joint and they will basically become plastic brazing.

 

There are two main companies that produce it, Plastruct and Evergreen Plastics. I would go the route of Evergreen Plastics, they're MUCH cheaper than plastruct for the same material. The only thing I would use plastruct for is some of their bulk sheeting is VERY cheap, and they have a lot more specialty stuff for modeling, like ladders, translucents, etc. You don't need too thick, since these are just little guys and not landing too hard, but since your design calls for a solid frame, including skids, you need thicker than I would otherwise recomend. I would go maybe max of 1/16 (0.0625") of an inch, min of 1/32 (0.03125") of an inch. The standard is to sell it by decimal inch/decimal cm, so you'll have to remember the decimal number. I would also say it might be worth a shot to try to laminate thinner sheets, where you can have very thin at the very top, and put just the right amount of added structure where called for. (although thicker sheets can be trimmed to be thinner with a razor/X-actor knife.)

 

http://www.hobbylinc.com/htm/p.....s91104.htm That's where I got my stuff from before, and that's about the right thickness I would recomend for something like this. (maybe a little more, maybe a little less) Their bulk packs are VERY reasonable, especially compaired to everything else by plastruct. I would also get some angle styrene to re-enforce joints and whatnot.

 

Anyway, it's VERY easy to work with, lightweight, cheap (if you buy the right stuff) and quite durable. Nowhere close to credit card plastic durable, but it gives some, and doesn't break, just bends. I wouldn't be suprised if the plastic on the military heli bodies are some sort of polystyrene.

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Helgi Rudd
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December 6, 2012 - 10:51 am

Love the idea of the glue that 'welds' it together... sounds toxic, but fun!!! :-)

I'm planning on trimming down that cradle I've made to see how much I can reduce the weight while still keeping strength... I haven't received the dremel tool I ordered yet and I'm thinking I'll need a fair bit of practice before tackling anything worthwhile. That Polystyrene sounds perfect for making a very lightweight 'shell' for the helicopter... I've spent a fair bit on equipment already... I can see this being an expensive hobby, but hey, that's what makes working for $ worthwhile right?

 

I have some scales now! Just came in today... I've weighed a few things:

 

- Parts removed = 12.88g

- Current helicopter, including the plastic PVC bits I've added = 27.63g

 

Looks like I've already taken off enough to be able to replace the stock 150mAh battery with TWO 240mAh batteries and still be under stock weight!

I also taken delivery of a long piece of carbon fibre rod... intending on replacing the tail boom with that... once I get hold of that dremel tool :-)

When I was younger and tinkering around with electronics I didn't have access to 'breadboards'... lived in a remote area and we were quite poor... so I soldered my circuits without an board... I called it three dimensional soldering... I would end up with balls of circuitry... they worked though and were much lighter without the board obviously. Crazy thoughts of getting the 107 circuit diagram and doing some three dimensional soldering to reduce even more weight! Would have to practice my soldering skills... a LOT... ha ha, those little chip resistors / capacitors are fiddly enough on a circuit board!

 

Also got excited reading through a webpage showing in a fair amount of detail how to replace the infra red with radio control. I've never had an excuse to own a oscilloscope... this might be my chance!  http://www.brasswings.com/rcsyma.html

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zedorda
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December 6, 2012 - 4:38 pm

Thanks for posting this project it has been very informative. I was thinking of doing something similar but not as extensive. I want to add a 350mAh plus plugs to enable battery swapping. I also intend to mount the battery between the skids and I am perfectly ok with adding some additional grams but not sure how much to allow yet.

 

Have you considered using balsa wood maybe treated/painted with something to increase surface hardness?

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Helgi Rudd
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December 6, 2012 - 10:11 pm

No worries at all zedorda... I'm having heaps of fun with it already, happy to post anything that might help.

What I'll do tomorrow is weigh each part separately and put together the weight saving for each weight saving step... for example how much weight is saved by just removing the canopy and nothing else... or perhaps just removing the tail supports... or by removing the metal plates in the guts of the middle etc. etc.

I'm also interested in cataloging a reliable reference for battery weights... I find so much inconsistency when looking at the various battery sizes (150mAh, 240mAh, 350mAh... etc.)  I'm hoping to end up with a formula which takes into consideration power and weight variables to identify the best market battery available for longest possible fly time.

If you just replace the stock 150mAh with the 350mAh and add plugs etc. without removing some weight I think you might be stressing the motors a bit beyond the reasonable. Without having an idea of how much the 350mAh battery weighs it's hard to know what you might need to remove to get a nice stable setup. Hopefully the table of part weights I'll put together tomorrow will give an easy way to assess the options if you do know the battery weight!

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CPD
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December 7, 2012 - 4:27 am

zedorda said
Thanks for posting this project it has been very informative. I was thinking of doing something similar but not as extensive. I want to add a 350mAh plus plugs to enable battery swapping. I also intend to mount the battery between the skids and I am perfectly ok with adding some additional grams but not sure how much to allow yet.

Have you considered using balsa wood maybe treated/painted with something to increase surface hardness?

I've worked a lot with balsa--good, cheap, easy to work. If you coat it with simple white glue, it becomes a LOT harder, but it's still too soft for these things. The big problem is that the screws and whatnot on the heli aren't that long, and balsa's too thick. Plus, styrene sheeting costs about as much, if not less, and is just as easy, if not easier to work with. (plus, when you do something with balsa, I've had a tendacy to notice it doesn't look very "professional" while anybody with the right stuff can make styrene look half decent.)

 

The only downside I've seen to styrene yet for anything is the glue you have to use for it comes in a jar that is VERY easy to knock over. Not good when you spill half of a $3.79 jar of cement all over the basement floor... (it's thinner than water and runs VERY easilly.) I bought a dollar tree stone candle holder for mine, about the perfect size, and nice and heavy to keep the bottle from getting knocked over.

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zedorda
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December 7, 2012 - 12:20 pm

This is one I am considering but not sure if 25C is too much current.

 

http://www.cheapbatterypacks.c.....-Pack.aspx

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Helgi Rudd
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December 7, 2012 - 12:25 pm

As promised, here is an image showing various parts you could remove and their weights.

 

Note the pile of 5 screws in the top right... these belong somewhere in the mix (I'm using them to attach my custom bits of PVC)... but you're getting a fairly accurate idea of where the weight lies from this image.

 

If you added a battery that was 3g heavier than the stock you could simply remove the nose cone and you're up and running... if you could make a super lightweight replacement nose cone weighing about a third of a gram all the better. Lots of ways to reduce weight to compensate for adding weight on in other ways!

 

Note that my version has the small weight in the nose cone... and the LED is in the nosecone I've removed as well.

 

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Helgi Rudd
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December 7, 2012 - 12:39 pm

The C rate defines how much current can be drawn... too high is not a problem, too low is though.

 

You can work out how much the maximum current is with the following formula:
 
C Rating x mAh / 1000... so for that 350mAh rated at 25C you can pull a maximum of 350 x 25 / 1000 = 8.75 amps... they advertise 8 amps which is probably a good thing since you wouldn't want to go right up to the limits.

 

No idea how much current the 107 pulls... could roughly work it out from flight time I suppose...

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zedorda
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December 7, 2012 - 1:01 pm

I am also tossing around the idea in my head of maybe using some of my old cell phone batteries. I have one that is 840mAh at 19g. Yes it is on the heavy side but there seems to be enough weight to remove to make it possible. The flight time could be 40+ mins but the charge time would suck.

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Helgi Rudd
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December 7, 2012 - 1:44 pm

That would be brilliant if you could pull it off! I want to see record breaking flight times :-)

On the topic of the C rating... I wonder if the cell phone battery would be able to handle the current discharge needed? Apparently the last thing you want is an exploding LiPo battery... it's meant to be spectacular!

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Helgi Rudd
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December 7, 2012 - 2:17 pm

Dremel's are fun aren't they!?  I've been missing out all these years! 

 

I've whittled away what I'm able to (with my total of half an hour Dremel experience lol) from my PVC parts...

 

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With the six screws needed, they come in at 0.83g... the screws make up 0.29g of that.

 

The PVC is quite strong, with better Dremel skills I could take it a bit further.... but I'm happy with this setup for the moment. The electronics board sits nice and snugly on that flat bar... I've removed areas where chip resistors / capacitors were in the way... so it's nice and flat on the remaining surface. The other PVC part comes down and sits snugly on top of the circuit board so it's well enough supported.

 

The picture below is of my current 'bare bones' 107G... it weighs in at 26.08g... with the above PVC parts attached so it can actually take off, that's a grand total of 26.08 + 0.83 = 26.92g

I haven't touched the weights in the balance bar... or replaced the tail boom with carbon fibre rod... but I suspect that people saying they can get their setup to just over 20g are cheekily weighing without the battery... maybe not though... we'll see soon enough.

 

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Next job, cleaning the soldering iron with the dremel tool and breaking out the carbon fibre rod!!!

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CPD
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December 7, 2012 - 3:15 pm

Wonder if there's carbon fibre tubes you could get that would be a close enough match for the main shafts that you could swap them out... Probably could shave off a few more grams, and probably could drill small, well-aligned holes in the gears too. You would just have to make sure they were PERFECTLY aligned so it wouldn't be the slightest bit unbalanced. You could probably shave down where the tail boom goes into the corpus if you decide to cement it in there instead of screwing it too.

 

If I had the time, a dremel and a heli to spare, (well, ok, it wouldn't be spared) I would have to try this out sometime... For now, I have a friday, kinda sorta have a weekend, then finals week... Oh dear...  Not gonna be fun...

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Helgi Rudd
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December 7, 2012 - 11:45 pm

Love the idea of drilling holes in the gears... I'm not competent enough to do that right now, but it's a brilliant idea... so many parts are over engineered, a few holes in the right places would reduce weight without reducing critical strength at all. Hmmm... rotational energy in the spinning parts too, making those gears as light as possible seems like a great idea!

 

I put my modified copter into play tonight... had some fun outdoors with a bit of a crowd gathering wondering what on earth this tiny flying thing was! Flying close to power lines was fun, it's amazing how high it can go... limited very much by the psychology of flying something that's infra red controlled... I'm very much tempted to do the radio frequency mod on the web page I linked above... VERY much tempted... I want a light weight radio frequency version... if the best that is available is the website I linked above then I'll go for it... I reckon I can trim down that receiver circuit board to less than a couple of grams.

 

I have to say... PVC is not the right material to work with. I've broken bits off the parts I've fabricated in posts above, left right and center. It's too brittle at this scale. I have an alternative plastic I'm going to work with next... it's very dense, but very flexible and... well, it just 'feels' like the right thing to use... I will try my best to identify it, as I think this one is going to be the one to work with for parts that are structurally important.

 

I replaced the stock tail boom with the carbon fiber tubing I bought. By chance as much as anything else the CF tube I bought fit perfectly inside the stock metal tubing... when I say fit, I mean that it fit to within a few hundredths of a millimeter. I sliced three quarters of an inch of the stock metal tail boom from either end... so I have all the fancy connector bits ready to go (like the groove in the original metal that fits perfectly into each end of the receiving plastic bits).

 

So I replaced the stock metal boom with a carbon fiber boom that is longer.... it weighs LESS than the original boom but is longer... and by the leverage principal it gives better forward and backward movement.... i.e. something giving thrust further out than originally when connected by a lever (aka the tail boom) is going to give faster forward and backward movement.

 

In the picture below you can see I've rigged up a makeshift battery support... so I can give some temporary weight to the front end, until I get my two battery packs that I'll place either side of the mid section.

 

I am playing a waiting game on battery delivery now... tempted to remove weight from the balance bar weights.

 

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