Scale Soaring UK

I need to fashion a tailskid from 18swg spring steel, any idea of a source for such material and how does one go about cutting/shaping it? Or maybe there is a more practical elternative??

Stephen,
When I made up the multi-leaf tailskid for a 1/3 scale Slingsby T21 a year or so back, I recall that I may have needed to anneal thigh carbon steel in order to be able to cut/form it, but then certainly had to re-temper it to get the required spring (to a light blue colour.)
I remember having to have 2 goes at getting enough spring without it being brittle. First attempt was a little too soft.
I cannot now remember where I got the spring steel from, although I think I bought a length of suitable width/thickness carbon steel strip on Ebay & cut that up into lengths, drilled, curved the ends as required.
There may be some additional info. in my Jilles Smits 1/3 scale T21 build thread.

Stephen,
T21 build thread is here viewtopic.php?f=12&t=755&start=40#p9910.
Mention of the tail skid in on page 5 & it definitely appears that I started with annealed carbon steel strip, cut this as required, then tempered the resultant pieces.
I will see if I can find any reference to the material I bought.
Peter

Thanks for that Peter, I'll take a look at your T21 thread for further detail.

Sold by Reeves2000. This is the sort of thing. They do other sizes, search for spring steel.

https://www.ajreeves.com/search/for/spring+steel/



BC

I seem to recall I used a short length of wing joiner bar on mine...

Barry, thanks for the link, it looks very similar to wing joiners as alluded to by Chris.

chris williams wrote: ↑04 Dec 2019, 21:34 I seem to recall I used a short length of wing joiner bar on mine...

No you didn't, I made it for you. (or maybe that was another one....)

Well I found another option, an old saw:


A stroke of luck, at 1.2mm the blade was the correct thickness so a few minutes work with the Dremel and I had the blank made:

Well done Stephen.
There is often a solution to hand if you use the grey cells
Not sure how much carbon is in your material, but you may be able to re-temper if necessary to alter springiness.
(Note that local heat from your Dremel cutting may have altered the saw material hardness).

Well, the next problem is how do you drill it??

I've tried a normal drill bit at varying speeds and a diamond bit in the Dremel, neither of them have any effect whatsoever.

Failing me not being able to drill the steel are there any suggestions for a different material to produce the tailskid from?

If you use this:-

https://www.ajreeves.com/search/for/spring+steel/

You can drill it, and then temper it after drilling and bending.

BC

Barry,
If Stephen finds it difficult to get hold of suitable annealed steel in Hungary, I suppose he could try annealing what he has (by heating to red heat), drilling & bending as required) then tempering the result?
Worth a try?

Edit: I now see that modern hacksaw blades are usually made as a strip of harder tool steel (teeth) electron beam welded to a backing strip of softer material for the main blade in order to give hard wearing teeth on a less brittle blade.
Thus not sure what the carbon content is of the main part of the blade (which is presumably what Stephen has cut away for his skid).

Thanks for the helpful replies Barry and Peter, I had looked at that source of steel previously but baulked at the shipping cost to Hungary. I cut the blank from a large cross cut saw not a hacksaw blade if that makes any difference Peter. To "soften" it do I heat it to red hot then let it cool naturally or dip it in water, which I understand is the process of annealing it??

Stephen,
If it was a normal wood saw blade then I should think you have suitable carbon steel as another website I looked at said that one of the popular uses of spring steel as used for leaf springs etc. was saws.

Yes, I think you will find that heating to a red heat (theoretically held at temperature for a while for thicker sections) & then allowed to cool slowly should achieve an annealed material. (Don’t quench). (Industrial annealing uses ovens which are programmed to follow temperature/time profiles, holding at temperature for an hour or more, then slowly reducing temperature over several hours - Google Annealing process.)

Tempering needs steady heating to get the whole workpiece to a chosen colour (colour is a good indicator of temperature) to achieve the desired hardness, quickly quenching in water when the colour/temperature has been reached to ‘fix’ the hardness state.
I think I went for a light blue colour temperature, but cannot remember now (May have been straw )

You can always rough check hardness by drawing a file across an edge before a bend test by flexing between fingers.
Too soft & it will just bend whilst too hard will make it brittle/break.
Look up a tempering colour chart on the web for guidance.
If too soft then you can try a higher colour.
If you overdo the temperature then you can re-anneal & start again.

I’m sure Barry will chip in if I haven’t got this right

Thank you Peter, very helpful.

Try a cobalt drill used them on stainless steel.

Keith

I also have had success with a cobalt drill turning at low speed on spring steel for holes on my MU13 tail skid. Regards John.

If you let me know what size you want I'll have a look and see if I have the size.

Keith

To be a little pedantic regarding hardening and tempering. Normally this is a two stage process - heat and soak the components at a temperature which ensures crystalline phase change in the steel to austenite. Quench in water or oil (the latter is gentler due to the temperature transfer rate). The parts are now very hard, but also brittle. Next comes tempering - heat the parts to a lower temperature (< 200C) to start the phase transformation from the martensite structure created when the parts were quenched. Tempering also requires some time. I would recommend playing around with the process to get the correct amount of hardness.

Once all your fabrication is done, with the thin section of the material being used you could quench it in oil, then it may be OK to use without further processing. I guess you want it stiff enough not to bend when it contacts the ground. Brittleness may not be such an issue in this case. Of course you won't be able to do any more work on it in the hardened state (as you have found).

Wikipedia has more information: https://en.wikipedia.org/wiki/Tempering ... ched-steel

(I did a materials science degree in 1983-1987!! It's been a long time...)

Keith wrote: ↑18 Dec 2019, 15:44 If you let me know what size you want I'll have a look and see if I have the size.

Keith

Very kind of you Keith, I need to drill a clearance hole for a 2mm bolt, but you do know I'm in Hungary??

Is this the right approach: I should first heat the saw blade up and then allow it to cool naturally, fashion and drill it then re-heat and quench in water/oil to harden it. I'm going to have to get a blow torch before I can do this.

This is turning in to a lot of work for such a small component!

Stephen,
As far as I can see, you have the right idea about the basic annealing/tempering method (what a friend did for me whilst heat treating my multi-leaf skid parts anyway).
I have annealed small parts, but we can usually get can pre-annealed material as the starting point in UK.

Presumably there is no-one to hand near you (another flyer?) who happens to have some kit/experience - especially power fliers who often need to fashion undercarriages/exhaust piping.

I have used a small butane type torch for the small parts - one which has a simple burner head that screws onto a standard gas cylinder roughly 80mm dia. (I used to use it for home plumbing DIY )
It also helps if you can make a small hearth to reflect heat off bottom & rear to help get more even temperature over the whole part, but this really needs firebrick material ideally, but some solid concrete items may help (don’t use ordinary bricks as the heat is likely to cause then to fly apart as trapped air expands).

It’s a good idea to have the tempering colour chart in your mind when heating, as you can then follow the colour change progression & be ready to stop when the correct colour comes up.

As you say, it’s a lot of trouble for a small part, but there isn’t much alternative unless you can grind a small hole with a conical dremel or a drill which is harder than your strip material.

Peter, I was going to buy a small blow torch as you described but your mention of firebricks/hearth has given me another idea. I wonder if I put the part in my log burner, left it in all day then allowed it to cool overnight before fishing it out the following morning and working on it. Then reverse the process to harden it only pulling it out whilst hot and quenching in water. Or is that too imprecise a method?

I've never come across another RC flyer around here, unless you count dr***es

Hi SteveB I have a couple of 2.2mm drills if you send me your address I'll send them to you.

Keith

Stephen,
I think your on burner idea may be rather too imprecise as you suspect.
I asked my learned friend with heat treatment experienced if my thoughts on annealing & tempering were correct & it seems that I had missed out the intermediate re-hardening stage before tempering. See his reply below:

“Hi Peter, almost, to anneal do as you say and heat to dull cherry red and allow to cool, ideally in pre heated sand in a bucket which will allow the material to cool more slowly, drill with a sharp bit at slow speed with plenty of oil and firm down pressure. If the material work hardens then use a masonry bit with tungsten carbide tip. To re-treat heat to mid cherry red and quench in oil, this gives a slightly slower quench and allows grain structure to form more evenly. The material will now be very hard and consequently brittle, the hardness needs letting down by the tempering process. Clean the surface with emery cloth to a bright finish, then warm with a soft flame very slowly watching for the surface to start changing colour. Take it very slowly and have the oil bath ready below the workpiece, as the colour starts to show move the flame away, wait a few seconds, re-apply the flame by wafting it gently over the workpiece, watch the colour go from light straw though dark straw and making sure the colour is even across the whole surface quench immediately mid blue is seen. This is the correct colour for springs. Good luck, take it slowly! “

Hopefully, you find a way to make the skid one way or another.
Peter