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Author Topic: Matching music wire and aluminium tubing size for shaft-bearing  (Read 548 times)
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Ashu
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« on: August 28, 2019, 10:44:37 AM »

Hello
I am a beginner and have used the commercial plastic props for outdoor rubber FF airplanes. I have tried making yogurt cup props too (without freewheeling mechanism) and used a paper clip wire for the shaft and bearing.

Here in India I am unable to find the plastic prop, or the music wire and aluminium tubing to make a stronger and hassle-free shaft-bearing. While there are ready made props to buy from US, I wanted to explore if I can get some music wire-alum tubing through a friend returning from US. I could also compare if that ends up being more cheap. I can make the prop from yogurt cups which serves the purpose. (I have made super cap airplane with my friend John Haren's help, and I can order its materials from China; but it is difficult for kids as the first model and so I want to see how feasible rubber FF will be. I intend to make Darcy's Squirrel and John's XSticksy models with kids as beginner airplanes.).

So here are the queries:

I saw in some plans that 1/16" OD alum tubing is used for 0.025" music wire and it is probably a perfect fit with just 0.23mm remaining wiggle space inside the tubing. But is it suitable ONLY for thinner indoor rubber motors with less tension? Can the 0.025" wire take the tension of a 21" or more loop of 1/8" TSS motor, or a bigger diameter music wire will be needed? What about 3/32" rubber motor? I coudnt make sense of tensile strength chart of music wire, if that is relevant.

Gary has written in his Endless Lift website that 0.039" music wire is the same size as the wire used in commercial plastic prop assembly for outdoors. However, I couldnt find any mention of tubing size for 0.039" wire on that site or elsewhere on internet. The ID of 1/16" OD tubing will be small for it. After 1/16" OD tubing, the next size available is 3/32" OD tubing whose ID will be 1.66mm. So the 0.039" wire will leave a wiggle room of 0.67mm which I think is large and not suitable (??). For the 3/32" OD tubing, the closest will be 0.055" wire which will leave 0.26mm space. But will that be too big/ heavy/ undesirable?

So to make a diy shaft-bearing for for a model with 1/8" TSS motor, what size music wire and aluminium tubing will be a good match? Which tubing to use for 0.039" music wire?



Also, what are cheap and good online sources for getting the wire-tubing (and hopefully doesnt have too high shipping charges). I saw "Kit Kraft", "True Value" and "Grainger". Has anybody purchased from them?

Thanks!
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strat-o
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« Reply #1 on: August 28, 2019, 12:34:10 PM »

These are all good questions.  While I don't have many answers, I can offer this: You can find tubing in pens.  Usually this tubing is plastic but sometimes it is brass.  Either should accept larger diameter music wire.  Gluing propeller blades directly to tubing my be troublesome but if you take a small piece of balsa wood (or possibly a thicker piece of foam plastic), you can easily glue blades to that and it shouldn't be too hard to drill a hole in the balsa wood to accept the tubing from a pen.  This approach should allow you to devise a free-wheeling prop.

Also, wire should be locally available in music stores (hopefully).  See if you can find a source for piano strings or possibly bass guitar strings (but avoid the strings that have a wire wrapping).

Hope these ideas are helpful.  Good luck!  

Marlin
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lincoln
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« Reply #2 on: August 28, 2019, 09:21:59 PM »

The critical factor isn't rubber tension. The size of the prop and the weight and speed of the model are what's important. On an EZB, a prop shaft might be only 0.01", even though the prop is 14 inches, because everything is very light and the model is slow.

Looking at Darcy's Squirrel, with a 6 inch prop, a .025" shaft may be enough.


In the US, lots of hardware stores carry K&S brass tubing and music wire:
http://www.ksmetals.com/26.html
http://www.ksmetals.com/17.html
Brass is a somewhat better bearing material than aluminum, though it's heavier.

If I wanted to use 1/16" OD K&S tubing for a nose bearing, I'd just use 1/32" wire in it. There's enough clearance. 0.023mm is considerably more clearance than you need, though it would probably work ok. Just a bit sloppy.

True Value is a chain of hardware stores. If your friend doesn't have to return for a few days, he can order something and pick it up at one of these stores without a shipping charge. Or, at least, I think they wouldn't charge shipping. Grainger is a big outfit with stores in many places, though not as many places as you can find hardware stores. (For instance, I can walk to the nearest hardware store in 20 minutes, but the nearest Grainger is 5 miles away. I haven't used them much, but have no reason to think they aren't a good outfit.
For mail order inside the US, McMaster-Carr is fast, but not necessarily cheap cheap. I've ordered quite a few things from them.

Here's a list of links for model airplane suppliers, though most are in the US:
http://flyingacesclub.com/wp/links/
You might check out Pecks, but many of the places on the list could meet your needs.

I'd be surprised, however, if you couldn't find suitable supplies in India. They might be in metric sizes. If you have a drill bit slightly larger than the propeller shaft, then you could drill a piece of plastic or other suitable material to make a nose bearing. Keep in mind that, a lot of times, if you use a 1mm bit in a piece of plastic, the hole might end up 0.95 mm or something because the plastic has some give to it. You might have to improvise. It might not work right the first time, but in that case you can try again.
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Ashu
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« Reply #3 on: August 29, 2019, 02:44:05 AM »

Thank you Marlin and lincoln! Very helpful.

Marlin:
I do have some ideas for making the prop. John too sent some pics. As per Slater, ScienceToyMaker, Dragonfly helicopter design, I used to use the tube from ear buds. That would involve squishing the ends at the desired angle for corred P/D and inserting the prop blades and gluing them. It worked the last time I made it.

The other idea using a wood hub and drilling hole for tubing seems nice too and is similar to what John sent me. I might probably glue 2-3 pop sticks or balsa and make them the hub and drill through them to house the ear bud tubing. The prop blades can be glued to toothpicks and then glued to the centre hub. I will try both methods. The larger inner dia ear bud tube (abt 1.5mm ID) will be ok for gluing inside the prop hub? In this case shaft dia will be just 0.8mm for the 1/32" wire, leaving 0.7mm clearance. Or should the clearance be lesse than this and same 1/16" alum tubing be used at the hub as well? If eqr bud tube works for the prop hub, I can then use the alum tubing for main bearing only.

I also have some ideas for freewheeeling mechanism. John sent me the Grami Goosie prop design. It is somewhat si.ilar to the other design which has a pin drilled and glued on the prop just beside the shaft; I saw it on https://freeflight.org/library/technical-library/ (Freewheel, Simple, PFFT: 3-4/12)


lincoln:
The 1/32" wire will have a theoretical clearance of just 0.08mm. Will that be ok, or too tight? Any chance that the products' dimensions might have fluctuations from the stated values and the wire ends up being snug fit in the tubing? True Value has 0.032" wire which will have even smaller 0.06mm clearance with 1/16" tubing. They do have free shipping to store option. Thanks. I will find out if my friend will have the time to pick up personally.

People do sell music wires here in India (spring steel wire). But it is not sold in small qty online, and online listing is for wholesale large qty purchase only (minimum order several kilograms). Other than that it is not available in shops in or around my location. At least I havent found it yet.

Getting the right size tubing is the bigger issue as I could have used the paper clip wire or 1mm dia GI wire for shaft. I will explore the alternatives ideas for bearing that you and Marlin have suggested. I havent yet found a solid plastic piece that I could drill.
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lincoln
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« Reply #4 on: August 29, 2019, 03:38:37 AM »

If you can find a spring made,of the right size of wire, you can probably straighten it by pulling really hard. Depending on the wire size, it might take hundreds of pounds of force. I've straightened kinked guitar strings that way. I suspect the diameter may end up slightly smaller.

For reference, K&S tubing that I've used fits into the next larger size. Look at the wall thicknesses on the K&S tubing.  They leave a little bit of room.
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lincoln
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« Reply #5 on: August 29, 2019, 03:45:54 AM »

BTW, you might be able to drill holes in the plastic caps that go on the end of the tube from used up ball point pens. Two such caps could make a prop bearing. There are a gazillion ways. Some old model airplane kits had round plugs with holes drilled through for prop bearings. They looked like wood versions of Peck nose buttons. I imagine they needed oil or grease to work well.

It's also possible to make a nose bearing from music,wire, but it's tricky.
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Ashu
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« Reply #6 on: August 29, 2019, 06:26:23 AM »

Cool. Just after posting, I was looking at my ball point pen and sketch pen and thinking if I could drill a hole in in with a pin vise and join 2 of them Smiley Sewing machine oil might help. It would be much wider than the 3mm balsa fuselage though.
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strat-o
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« Reply #7 on: August 29, 2019, 11:05:14 AM »

Laminating the hub from pop sticks sounds interesting.  I'd even go for 4 layers.  The image shows how you could notch the ends to accept propeller blades.  You mention ear bud tubes.  Are these tubes very hard plastic?  I think your best bet is to try to get plastic tubes that are hard or semi-hard.  High density polyethylene is common and probably good for this purpose.  Also if you have solid plastic you might be able to drill by heating the wire you intend to use and pierce through it.
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TimWescott
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« Reply #8 on: August 29, 2019, 02:41:02 PM »

OK.  I'm slow.  Are we talking about the bearing that goes in the model?

In that case, a wooden bearing like Lincoln mentions may work well. Comet kits used to come with hardwood bearings; this should be something that you could turn easily from a dowel on a primitive or lashed-together wood lathe (like a drill).  I'd use a good hard wood, like maple or whatever is available locally that's similarly hard.

Rather than trying to oil it, find some cheap beads that fit over your prop shaft wire.  Put a bead or two between your prop and the prop button; those will reduce friction to an astonishing degree, and a little bit of light oil will probably make the situation even better.
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strat-o
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« Reply #9 on: August 29, 2019, 03:30:20 PM »

Tim, I think the gist of this is "How do you make a front end for a very simple stick model without having any source of supplies?"

Ashu, I like lincoln's suggestion of straightening out springs.  I found this description of how to do it on the net:
Quote
The wire of small coil springs found in ball-point pens & elsewhere can be straightened for re-use in different form.
The wire is drawn from the coil by using two metal rods each small enough to slide inside the coil, a vise or a pair of mole grips and a pliers.
Clamp the rods side by side at one end ( oo ) with the spring slipped over one rod near the clamp.
Grip an end of the spring with the pliers and draw it (preferably away from you) over the free rod so that the spring is forced to bend against its curl.
WARNING!! these springs have SHARP ends and are SPRINGY!!  Cry
The angle at which you pull relative to the rods, and how close together the rods are, determines how straight it becomes and you only get one shot at each spring.
With the wire you can make a smaller or larger coil by winding around another rod (about 2/3 of the required diameter but variable) or you can make any shape spring you need.
Pick an appropriate wire diameter for the strength of spring you need but be aware that strong springs can be brittle!

The source of the metal rods might be two small nails.  Also I think it would help if when straightening the spring that you untwist the spring so if the spring is wound clockwise, as you pull the spring apart, untwist it counter-clockwise.  Safety is important here.  Probably good to wear some sort of eye protection because the spring could break and hit you in the face.
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TimWescott
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« Reply #10 on: August 29, 2019, 04:00:49 PM »

Tim, I think the gist of this is "How do you make a front end for a very simple stick model without having any source of supplies?"

Thanks.  As I said, I seem slow on the uptake today.  If it's a stick, that makes things easier yet.

Ashu!!

Folks had this same problem back in the 20's and 30's in the US and other Western countries.  So they made front bearings from pieces of tin can.  Here's a plan from Outerzone that gives an example.  There are a lot of front ends like this out there.  As with my suggestion on a nose button, I suggest using a cheap glass or plastic bead here, too.  It should work well, and the raw materials are as close as your nearest trash bin.

I don't know what to suggest for wire -- I think that pen springs will be too small, but there's all sorts of little springs out there.  Some throttle return springs for small engines or even cars should be about right, if you can straighten them.  OTOH, if all you need is music wire you can make a little bit go a long way -- you should only need two or three inches for each model; that works out to a dozen models per length of K&S wire.  You may be able to order something from China, too, just in the equivalent metric sizes (i.e., 0.5mm to 0.6mm, which should be somewhere between just right and a bit too small for a 16 inch span model).
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Ashu
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« Reply #11 on: September 02, 2019, 09:56:16 AM »

Thanks a lot guys for all the suggestions! Sorry for the delay in replying- I am parallely making a simple backslider 'Coney' bottle rocket (design by Robert Youwens).

Attached is a pic of a paper clip bearing I had made the first time I tried making the bearing for John's XSticksy model 30 cm WS. It was okayish for less number of turns for 3/32" rubber motor. I wouldnt go that route again though, and it would be too tough for kids. The prop blades are inserted into the plastic tube after squishing it at an angle.


From the above suggestions, what I find most suitable and simple at present is:
Bearing: Cut a short 9 mm section of color sketch pen tube which has push snug-fit cap. 2 such caps can be inserted into one tube to make the bearing and that wont require gluing unlike the ball point ends. The part of the end cap that sticks out is usually 3 mm long. That will give a 15 mm bearing.

Shaft: I am still searching locally for music wire, but there is a 1.2 mm GI wire that we get here. It is stiffer and thicker than the paper clip wire and also fits inside the small beads I have. I'll try both paper clip wire and GI wire for shaft.


Tim, as you said, I am also considering ordering some 0.8 mm music wire from US through my friend. Maybe a few 1/16" alum tubing too. True Value seems good. That will give me an idea.
AliExpress in China seems to have increased its shipping for many items. The rates for small qty of music wire in general are quite high, but I found one seller who has listed 20m of 0.8 mm wire for $9.56 and 1 kilogram wire for $27...this includes shipping which is 2-3 times the product value Roll Eyes


Marlin:
You had suggested bass guitar strings. Arent those guitar strings usually wrapped with other wire and have a spring like outer texture? Or do they use the bare music wire too?
The ear bud tubes are hard enough. I use them for prop hub for the simple Dragonfly Helicopter design by ScienceToyMaker (Slater).


Prop and prop hub: I am currently not too worried about this as I have made the yogurt cup props before and they worked fine. The idea of cutting slots in pop stick hub is nice. Though I will probably either make slots in the ear bud tube (Dragonfly heli style https://youtu.be/O77Y2dEvi0s?t=291), or glue the prop blades to toothpicks and then glue the toothpicks to the hub. John sent me some pics for that (attached).

Thanks!
More suggestions are welcome Smiley
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Re: Matching music wire and aluminium tubing size for shaft-bearing
Re: Matching music wire and aluminium tubing size for shaft-bearing
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Re: Matching music wire and aluminium tubing size for shaft-bearing
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TimWescott
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« Reply #12 on: September 02, 2019, 06:46:52 PM »

1.2mm wire is probably about right for a 1 to 1.5 meter span rubber powered plane -- but if it's what you can get, it's better than nothing!

Please keep us posted -- there's folks scattered around the world who are in the same situation as you, wanting to build models but unable to find supplies in their countries.  Keeping us all informed of what you can improvise on your own will help them, too.  And if "official" sources of parts ever dry up here, we can go through your posts and stay in the air!
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Ashu
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« Reply #13 on: September 04, 2019, 05:42:02 AM »

I was seeing various sellers of music wire and checking shipping rates. I wrote to McMaster and they said this:
"Thank you for considering McMaster-Carr for your purchase. However, we will not accept orders from your facility
We will not accept orders from your facility due to the cost of complying with US export regulations. Those regulations apply whether the products are shipped directly outside the US or somewhere within the US for later transport."


This reply was after they said this the first time too and I clarified that I will be placing order for within US delivery to my friend, and am not asking for direct shipping to India. Sounds strange that they are denying sale even when my mate is the one who will bring it in his luggage. I mean if I or my friend still order the product, how would it concern them if we then brught it overseas, unless the item itself is prohibited on flight, which would again be the passenger's liability?
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« Reply #14 on: September 04, 2019, 08:30:42 AM »

Hello Ashu! I cant get music wire around here, so I get something similar from fishing rigs. If you have a nearby fishing store, go look for the stainless steel monofilament wire used for attaching the hook to the nylon. You might also get some small brass or copper tubes of the proper diameter, perfect bearing the prop hoock at the nose
https://www.amazon.in/BlacktipH-Shark-Rig-Tackle-Crafters/dp/B01M2DARVW
https://www.ubuy.co.in/search/index/view/product/B000ALE59Q/s/american-fishing-wire-stainless-steel-trolling-wire-single-strand/store/store
https://www.ubuy.co.in/search/index/view/product/B07S1NHQN7/s/5lb-200lb-7-strands-fishing-line-wire-leader-nylon-coated-stainless-steel-leader-wire-with-crimps-sleeves/store/store

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« Reply #15 on: September 04, 2019, 12:47:24 PM »

Initially you were working with paper clips.  The steel in small paper clips is somewhat weak and too easily bent.  However, you can change the temper of a paper clip and make it stiffer and more brittle and I think it is worthy of experiment.  You can change the temper of the steel whire by heating it to red heat, then quickly quenching it in water.  I think you can probably heat the wire using a candle.  If you see a bit of red glow of the wire I think that this should be sufficient temperature. If a candle doesn't work, I know you should be able to get good results with a simple bunsen burner that uses alcohol fuel.
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« Reply #16 on: September 04, 2019, 01:56:14 PM »

Quote from: Ashu
I mean if I or my friend still order the product, how would it concern them if we then brught it overseas, unless the item itself is prohibited on flight, which would again be the passenger's liability?
You wouldn't believe how much expensive red tape there is around what companies can and cannot export, most of it seemingly concerned with controlling anything that can be used as part of a weapons system or enforcing economic sanctions.  It's highly improbable that piano wire could ever find its way into that sort classification even under the various "dual use" regulations but there are some suprisingly mundane articles on some of the lists.  Companies are also legally obliged, under threat of utterly ruinous fines and very long gaol sentences for individuals, to make sure that such materials don't get exported by any means, especially "back door" routes such as local purchase, unless and until appropriate licences are in place.

If I were running the company and knowing a little of the administrative burden (my employer, a multi-national Co. has several large departments given over to the care and feeding of export licence arrangements and all us drones are subject to annual refresher courses on the main points of US, UK and EU legislation on the matter) then I too would simply say, "Sorry we don't sell stuff for direct or indirect export."

This doesn't help you one iota I know, but at least you now know that they do have sensible reasons for refusing your custom.

Lurk.
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TimWescott
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« Reply #17 on: September 04, 2019, 02:12:57 PM »

You wouldn't believe how much expensive red tape there is around what companies can and cannot export, most of it seemingly concerned with controlling anything that can be used as part of a weapons system or enforcing economic sanctions...

Yup.  And it's the law, so it doesn't have to make sense.  I used to work for a company that sold defense articles, and some of the regulations are downright stupid (like, if the Royal Danish Navy sent back a system that we built, and we fixed it back to the condition that it was in when we sent it the first time, we still needed to get an export license to send it back -- and the Danes are some of the closest allies the US has).

Now, if your friend gets some music wire and does not tell anyone what he's doing with it then it's on him (and maybe you).  And it can be gotten from a hobby shop, or Amazon, or whatever.

Initially you were working with paper clips.  The steel in small paper clips is somewhat weak and too easily bent.  However, you can change the temper of a paper clip and make it stiffer and more brittle and I think it is worthy of experiment.  You can change the temper of the steel whire by heating it to red heat, then quickly quenching it in water.  I think you can probably heat the wire using a candle.  If you see a bit of red glow of the wire I think that this should be sufficient temperature. If a candle doesn't work, I know you should be able to get good results with a simple bunsen burner that uses alcohol fuel.

Note that
  • you need to quench it while it is still hot, which can be tricky with fine wire.
  • the magic temperature for tempering is exactly the same magic temperature where it no longer attracts a magnet.  So you can test it as you heat (don't overheat the magnet, though -- keep it cold)
  • different paperclips will have different amounts of carbon in the steel, so your mileage not only may vary, it almost inevitably will

Hello Ashu! I cant get music wire around here, so I get something similar from fishing rigs. If you have a nearby fishing store, ...

May not be many more fishing stores in his country than hobby shops.

But this makes me think -- aside from finding a source of springs to straighten, you may want to look around for cables that have strands the right diameter.  If you can get a length of that (possibly out of a dumpster -- I'm all for dumpster-diving) then you could tease out the individual wires and straighten them.  The nice thing about that is that cable should have wires of about the right temper for music wire.
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« Reply #18 on: September 04, 2019, 03:14:15 PM »

Hypodermic needles are a useful source of thin wall stainless steel tubing. Cut by rolling under a knife blade. Aside from medical use needles are also used for glue dispensing. Do you have a medical equipment manufacturer or supplier locally - who might also have a scrap or reject bin with fine plastic or metal tubes and guide wires.
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« Reply #19 on: September 05, 2019, 03:24:04 AM »

Thanks Yagua for the suggestion and links. I will look for them, although my inland location doesnt have such fishing supplies stores...we do get the nylon fishing line. Larger cities, riversides or coastal areas are likely to have this.


Thanks for the export license related info! Certainly 'if it's the law, it doesnt have to necessarily make sense'  Cheesy


Annealing idea seemed interesting and I also had a look at some videos which showed the process. I heated the wire red hot over LPG cooking gas stove and quenched in cold water. But was surprised that the clip seemed more easy to bend and not brittle. Tried a couple more times but same thing. Not much difference than original wire, but did seem easier to bend and broke in much the same way as before. I even tried uaing a colder water with ice pieces to lower the temp. Am I missing something? This video shows lots of carbon precipitating (if that's not burnt plastic): https://youtu.be/fLvZkZxiXnE Mine precipitated much less.


Hypodermic needles. Interesting! Would they be strong enough? I saw this chary of needle OD, ID and wall thickness
https://en.m.wikipedia.org/wiki/Birmingham_gauge
17 gauge seems to be appropriate for the 1.05mm paper clip wire...not sure if I will get that exact size. I have some 2/2.5ml syringes with needles which match OD of 24/25 gauge. I guess the 17 gauge needle might be for a about 3 times larger volume syringe. I'll check out.


I dont know about guitar strings, but a friend said that 'low B' or 'E' string of bass guitar could give me a plain spring steel wire around 0.8 or 0.9mm. Marlin had suggested this above. Any more info on this? The shop I had enquired over phone didnt know about 'music / piano wire' but he might have bass guitar strings.
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« Reply #20 on: September 05, 2019, 08:46:18 AM »

I got the #18 hypodermic needle. Wikipedia chart says its ID should be 0.033" or 0.838mm. And it is smaller than the OD of my paper clip.  The OD of 1.20mm written on the pack matches the wikipedia OD of 1.270mm. So the chart seems reliable. The needle costs just $0.03- $0.05 and is sturdy.

#17 needle is not available but there is #16 needle which should have ID of 0.047" or 1.194mm. I think that will work for the 1mm+ paper clip. The #18 needle will work for the 0.031" and 0.032" music wires.


A slight diversion, but Gary has this nice post on making a propeller hanger assembly with shrink tube that can be changed http://www.endlesslift.com/prop-hanger-for-stick-fuselages/ What would be an appropriate shrink tubing size for 3 x 9 mm cross section fuselage for Squirrel?
At one place it also mentions that the tubing was squeezed in drill chuck as it was larger and the shaft was sloppy. I guess same could be done for the needle too, if it gives in.
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« Reply #21 on: September 05, 2019, 09:49:24 AM »

Not sure a needle can be squeezed in, but just have to try and see!

Late to the party, but here is an interesting adjustable prop hanger used on a profile/nocal model by Mark Fineman.  The brass tubing is soldered to the wire, but could be wrapped and glued to the wire "U."  Scuffing the tubing along the line of contact, and filing small transverse "notches" on the tubing should provide enough bonding support.  (Extra 400 article was in Oct 2003 Flying Models Magazine)   The caption refers to prop spars but there is just a one piece spar that supports two blades.  A brass tube with a freewheel "notch" is used for the hub bearing.
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TimWescott
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« Reply #22 on: September 05, 2019, 03:02:42 PM »

Annealing idea seemed interesting and I also had a look at some videos which showed the process. I heated the wire red hot over LPG cooking gas stove and quenched in cold water. But was surprised that the clip seemed more easy to bend and not brittle. Tried a couple more times but same thing. Not much difference than original wire, but did seem easier to bend and broke in much the same way as before. I even tried uaing a colder water with ice pieces to lower the temp. Am I missing something? This video shows lots of carbon precipitating (if that's not burnt plastic): https://youtu.be/fLvZkZxiXnE Mine precipitated much less.

First, a terminology nit: "annealing" is what you do to make steel soft: you heat it up, then cool it down slowly (and "slowly" depends on the alloy -- it's complicated).  "Hardening" is what you want, or possibly hardened and tempered, which means heat it up, quench it (to harden) and then bring it up to to hot but much lower temperature (enough to turn blue, but not enough to glow).

If it's getting softer, then it's probably cooling down below the transition temperature before it hits the water.  A steel that's just iron and carbon needs to be glowing red when it goes into the water -- if it cools in the air, that's too slow and you may well be annealing the clips rather than hardening them.  Either that, or it's made with steel with such a low carbon content that it just won't harden at all.

Note: Hardening steel is complicated.  The carbon content determines how hard you can get it, and the alloy determines how much time it'll take.  If you ever read about "air hardening steels", those are steels that are high-alloy enough that they can cool down really slowly and still harden.  "Water hardening steels" are the opposite -- they're low alloy or no-alloy, just iron and a lot of carbon.  They need to be cooled down quickly, or they won't harden at all.
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« Reply #23 on: September 06, 2019, 06:22:18 AM »

Indoorflyer:
Thanks for the pic. I am not sure if it can be used for wider 1/8" rubber motor. I think at this point I will prefer the simple thrust block at the bottom of the fuse stick.


Tim:
It could have lost the red hot state, though I quenched it almost immediately after it was red hot . I didnt heat it thr 2nd time though, as you mention. I will try that again and see if it makes a difference.
I think the 1mm+ paper clip wire I have, though not a match for spring steel, could stand the 1/8" motor. It is probably thicker than what you get in US (0.8mm?). I will try adding long set epoxy to the hook section to see if it gives some more rigidity.


I am yet to get the #16 needle for my paper clip; #18 was small but should be good for 0.031 music wire. In fact, my friend Slater (sciencetoymaker.org) had sent me some pieces of 0.8mm MIG welding wire long back to try for Dragonfly prop shaft (he sells these wires in his heli kit). They are quite light, though not too rigid. But they work with the smalll 11" loop of 1/8" TSS motor that the Dragonfly uses. I inserted it into the #18 needle and it is a good fit. (Pic1)
Unfortunately, I didnt get the MIG welding wire here as well when I was searching for it long back (I did find a 0.8mm TIG wire, which is 3 times heavier and was only available in spools of 13.5kg). But now I know that the ID of #18 needle is good fit for 0.8mm wire.

A friend of mine searched for guitar strings in Delhi. The plain wire strings were too thin (0.2mm) and the 0.8mm string had a wrapping around the steel core. (Pic2)


http://www.endlesslift.com/prop-hanger-for-stick-fuselages/ What would be an appropriate shrink tubing size for 3 x 9 mm cross section fuselage for Squirrel?
At one place it also mentions that the tubing was squeezed in drill chuck as it was larger and the shaft was sloppy. I guess same could be done for the needle too, if it gives in.
Any suggestions for the shrink tube size?
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« Reply #24 on: September 11, 2019, 09:52:10 AM »

Hi Guys
A friend in Delhi helped by visiting the big market there to search for spring steel wire. The shops making springs had 2 kinds of wires from shich they were making springs- shiny stainless steel and the blackish wire (which the sellers said 'is not steel wire but iron, because it rusts'). I believe spring steel comes in the stainless variety too? Ball point pen springs should be of that kind. And 'steel' rusts too. Have attached pics (pic 1 and 2) for springs made from both kinds of wire that the shops had. Since they were making spring with both wires, I asked him to buy both kinds. It was $0.69 for 4m of the blackish wire, and $1.39 for 4m of the stainless wire. 0.8mm dia. (The terminology used in markets here can be different, and confusing, from the technical name/specs of the product...so I though that the blackish 'iron' wire is also spring steel, but uncoated). Any thoughts on this?


I got the wires and they are perfect fit in the #18 hypodermic needle. Pic 3 (this one is the stainless steel wire shaft). The wire is stiffer to bend and cut with pliers so I guess it's the correct material.


I dont have steel cutting tools, but used mini hacksaw the first time, and a normal craft cutter (the bigger one 'box cutter/ snap-off blade knife") the second time. Wasnt too easy though. I get two 15mm lengths from a needle which I think should be enough length.

The first time I cut the pointed tip of needdle with mini hacksaw, I cut on one side until there was a hole, and since it was still lots to go, I tried to bend and break it with plier. It broke but the needle bent. I had to then open up the tube. Second time, with the knife (which was old and little rusty), it was easier and I could cut through cleanly without squeezing the tube. In both cases, I filed the exposed part with a metal file. I think the not-smooth blade of the old knife provided the grip...maybe sanding the surface a little first will help as the furst time I tried cutting with a new knife blade, it didnt cut.

The needle tubings leave little wiggle-room, slip smoothly and are strong.

The plastic end too has some needle in it which could maybe make a 3rd bearing (it is just 7.5mm long though)...?

I havent yet made the sketch pen tube bearing with paper clip wire, or the #16 needle bearing for the paper clip wire.
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