Steve biplane

Erfolg writes :- "I have purposely avoided talking about austenite phase, pearlite, or the detailed composition of Piano wire, silver steel etc. As I do not think it would add anything." . Unfortunately you are confusing the processing of 'carbon tool steel' and 'piano wire' and the explanation why they behave differently depends on what you avoided referring to. . Both start by taking the steel above its transition temperature (approx 750 to 800 degC, depends on the steel). . With a carbon tool steel the rapid quench from above the transition temperature produces martensite. Try cold drawing that and two things will happen (a) it will crack because it has no ductility and (b) it will wreck the die because it is rock hard. The subsequent tempering (between 210 and 300 degC depending on what you want to use the tool for) gives the steel toughness and reduces its brittleness. . With piano wire the cooling from above the transition temperature is carefully controlled and held at a temperature to produce a very fine grained pearlite, this is very tough and has sufficient ductility to enable it to be cold drawn. The cold drawing work hardens the steel, the trick is knowing how much work hardening you can do and still leave sufficient ductility in the final product (otherwise it will snap when you bend it, hands up all those who have bought piano wire like that!). . I hope you can see that by starting with steels which may appear to be chemically similar, but giving them very different processing, you can end up with two products that will behave differently when you come to apply the levels of heat associated with soft soldering. The quenched tool steel will behave differently to the work hardened piano wire because its structure is completly different. So quoting what happens to a quenched tool steel if you were to temper it at the temperatures associated with soft soldering is irrelevant for piano wire. Test evidence shows that subseqently heating piano wire to 300 to 350 degC does not affect its strength; some manufacturers used to do this, it produces a nice blued finish, but few do now. . Production of good quality piano wire requires a lot of material processing know-how to end up with a suitable product which has the required strength and ductility and is the reason, I suspect, why there is so much foreign rubbish currently for sale to aeromodellers. This is the last post I'm making on the topic. Steve

Peter, the last thing I want is to get into an argument with you over this topic, especially as we agree! Steve

MGTF, I'm impressed that you can manage to measure the magazine dimensions to the nearest hundreth of an inch. Or are you, as I suspect, a closet metric man with a calculator but you don't want to admit it! Only joshing, Steve

Peter, The reason I feel confident in saying that soft soldering will not degrade the properties of cold drawn piano wire is that some manufacturers have an additional heat treatment cycle AFTER the cold drawing; this is at around 300 to 350 degC. The evidence is that this produces a slight increase in tensile strength. The strength increase is not much (less than 5%) but in some instances you want might everything you can get. 40/60 or 50/50 lead/tin solders (by far the most common types, and the cheapest) are liquid above 230 degC and solid below 180 degC. If you want to prevent overheating the piano wire then use the solder as the temperature indicator and remove the heat as soon as the solder melts and 'wicks' into the joint. Steve

Erfolg, If you are using true cold drawn piano wire you will not have any effect on the properties as long as you do not heat it above 300 degC but go above that and the strength properties drop (by about 50% by the time you get to 600 degC). So soft soldering at less than 250 degC is ok but silver soldering, which needs in excess of 600 degC, is not. Steve.

Albert, I think the two motors on the top wing are going to make the model prone to tipping onto its nose on take-off so be careful how you open up the throttles (or fit two less powerful engines up there). I hope it works out for you, it will look really impressive in the air. Did you know there are plans to build a flying replica - now that will be impressive - but it is a very long term project and won't be cheap. For details (and a lot of other info on Imperial Airways) go to :- http://www.imperial-airways.com/Menu_page.html Steve

Albert, On the right-hand-side of this screen there is a large blue square that flashes '3000 plans', it's about on the same level as your original message. Left Click on that square and it takes you straight to the plans website. Type in fsp615 into the window labelled 'Search by' and then left click on the button labelled Search. Details of the HP42 plan should come up.

I know what you mean about the guards around machines in schools. A couple of years ago I went to a local school's open day and watched a kid on a drilling machine. I don't think he could see a thing through (a) his ordinary glasses (b) his safety goggles (c) the plastic swarf guard on the drill. It looked more like a game of pin the tail on the donkey than engineering!

It's one thing to obtain the corrugations in the balsa but then you have to apply surface finish and rub down (EVENLY) sufficiently well to represent a metal surface. It would need a lot more patience than I've got, good luck. There's got to be a better way.

If you are going to cast lead then please make sure you do it in a well ventilated space (preferably outside) and don't breath in the fumes. Leather gloves and a pair of goggles are also sensible precautions. Health and safety legislation gets a lot of stick in the media but it is there to protect people working in factories who otherwise, in this case, would be exposed to lead fumes from industrial scale soldering. The same can be said for cadmium or solvents or any number of nasty substances just waiting to overload our bodies with heavy metals or cancer producing agents. Is the legislation worth having? Well if you retired from a lifetime in industry in the 50's or 60's you would probably die before you got to 70, these days you will probably reach 80. I think some of that increase has got to be down to healthier environments in the factories, and the houses surrounding them. As long as we take sensible precautions when we very occasionally use things producing lead or cadmium fumes we should be ok. Steve

For the HP42 go to the plans website Dave gave and search for fsp615 (don't bother with the category) the plan is still available. 65 inch wingspan and that's 1/24th scale.

Peter, Perhaps it is worth resurrecting the old Aeromodelling Plans star system for indicating the level of experience the builder is expected to possess. I think these were :- * Beginner, plan self explanatory. ** Some experience (has already built a couple of * plans) so, for instance, only needs hinge positions indicating because builder knows how to fit a hinge. *** Experienced builder, expected to sort out details for him/herself. **** Expert builder, I think the CAP 21 plan would be in the ** category. Steve

Mark, Are you the Mark Lubbock of Midge home-built diesel engine fame? Steve

Tom, a good site, thanks for the link. Steve

Peter, sometime back in 1920's Rolls-Royce set up a company called 'High Duty Alloys Ltd' to develop high strength aluminium alloys. They were particularly interested in were increasing the strength of alloys at temperature so they could be used for pistons and cylinder heads. They also developed alloys that didn't age harden at room temperature after heat treatment but had to be 'artificially aged' by heating to ~170 degC. They were given the designations like 'hiduminium RR56' taking bits out of the words HIgh DUty aluMINIUM. I didn't know these alloys were used for rivets though. Steve

Peter wrote :- "Now even a gentle landing will bend torsion bars back and leave them bent back." Whilst looking at the bent remains of my undercarriage after an 'arrival' I've never used the excuse that it is the wire's fault - but I'm sure I will! Steve

I don't know the geometry of the undercarriage but here are some thoughts on Bob Cotsford's question. (1) If the main u/c legs are designed to carry all the landing loads then the extra bracket could be soft soldered into position as the temperature reached (~200 degC) won't harm the piano wire. You could make sure the extra strut carries no load by having the other end disappear into a tunnel in the fuselage. (2) The most likely way of incurring damage to a model undercarriage leg in a heavy landing is by imposing too great a 'bending moment' on it (bending moment is force at right angles to the leg times the distance from the point where the force is applied [in this case the wheel]). If the bracket is located close to the wheel then it may be ok to silver solder at that location because, although the silver soldering weakens the piano wire, the bending moment at that location will be low. BUT you would need to ensure the rest of the u/c leg didn't get too hot while you silver soldered the lug on. Model engineers have been known to do this by pushing the part to be kept cool into a raw potato (it holds it in position as well as keeps it cool) and you have to be quick with the soldering. Has the added advantage that you can chip, fry and eat your new workshop accessory when the job is done! Steve

The old rule of thumb for the 'soaking period' ie. how long you keep steel at cherry red before you quench is 1 hour per inch of section. So for 0.1 inch diameter rod that is one tenth of an hour or 6 minutes. BUT You will not return true piano wire to its original state by carrying out this procedure because piano wire is 'cold drawn' (ie work hardened) to achieve its high strength not heat treated. So bend it cold and make sure any bends are radiused. Steve ps. Some of the wire I've seen supplied with ARTF's is a poor quality Chinese imitation of real piano wire.

Chris, I've just reaised that if you do the search on that site it brings up 3 books on the DXXI (but two are Finnish!) I never realised it was so popular! Steve

Hi Chris, By coincidence, today at the Shuttleworth Airshow on a bookstall I noticed a new book has been published on the Fokker DXXI. It's a Dutch/English text with some good colour profiles, cost=£9. (It's an English company). They have a webpage where you can take a look, make enquiries, order etc. http://www.aviationbookcentre.com/__12_product_info3_asp3_5_prdID4_57557_prdName61_Dutch_Profile_Fokker_D.XXI_History%2C_Camouflage_and_Markings5_usrID36_5DE44046-0163-4CBF-AED3-8A8CA230B9841.html That's a long link and I don't know how it will post (may go outside the window) but I got to it by going to :- www.aviationbookcentre.com and search on fokker Regards Steve

Myron, Thanks for your quick reply. Unfortunately (for me) that means the cowl is ~0.7 inch too small for my needs. Back to plan B then and make one out of GRP. It's a good job it's a simple shape and Avro's had painted cowls. Thanks again, Steve

Hi All, Can one of the Puppeteer builders do me a favour and measure the diameter of the cowl? I'm looking to build a one sixth scale Avro 504K and need a 7.5 inch diameter aluminium cowl and was wondering if the Puppeteer cowl would do the job (Assuming its available as a spare from Flair). Thanks in advance, Steve

I think you will find the reason for fabric covered control surfaces in a lot of cases was to reduce the inertia of the control surface in order to prevent flutter.

Hi, While we are on the topic of servos, and as David Ashby is reading/replying to this thread, can I make a request that model plans state the min torque rating required for the servos in different positions (or what the designer used). For the safe functioning of the model this is just as important as stating the engine size which every plan does as a matter of course. Years ago it didn't matter, we just had standard servos, but now there is a very confusing choice and the guy building the model is just expected to know what to use. Steve

Graham, A nice looking model. Are there plans by Jerry Bates for other planes? Have you got a web address for them? Regards, Steve