Richard Hansford

Have a look at the Loc8tor.  A small unit on goes onto the model and you can then find your model using the hand held direction meter.   The battery in the model's unit should last at least six months so you will have plenty of search time!

Hi Steve. The Mk 1 OS 70 is a good engine but not as good to use as  the current ASP / SC /Magnum 70 fourstrokes  which would also come with a warranty ! Richard 

Hi Jonathan. If you still have the original carb on your HB 12 it will be a PERRY carb.  These are good carbs and normally run well, certainly better than the OS air-bleed carbs.  The HB 12's  PERRY carb has a black plastic body. It is not an air-bleed carb - the mixture is adjusted with the large diameter brass wheel at the base of the main needle.  As Eric says do not have your low speed mixture too rich otherwise you could be too weak on the main needle. The little screw on top of the carb does not have a spring and is, as you said, to set the idle speed.  On my HB12  the throttle can close completely. Contest 10 or Sport 5 fuel will work well.  The F5 plug is also OK but I use a Model Technics Maxflash M6 which seems to give throttle response. Some points to check: The plastic carb can be ruined if it has been cleaned with petrol.  The carb spindle should turn smoothly and have NO slack movement other than a very slight end float. The main needle is indeed quite sharp and is a constant taper.  Does yours have a groove worn onto it where the needle has been fully screwed in in the past ? Sensitive needle settings can sometimes be due to too much exhaust back pressure pressurising the fuel tank.  The std HB12 does not use exhaust pressure for the fuel tank. Is your prop too big or small?  You should ideally have a prop that gives 12,000 RPM on the ground with this engine. At what height is the fuel tank on your test stand relative to the carb?  The tank needs to be reasonably shallow and be centred about 10mm below the carb needle height.  If your tank is any higher you will be weakening the needle setting with a full tank  and that will then be too weak as the tank empties. Are your engine's piston and liner gummed with castor oil varnish?  If so that can have an effect like you describe.   NB  'Fairy Power Spray' is excellent at removing old castor. Hope this helps Richard   

Hi All. 4 mm bolts are plenty strong enough for holding a 120 size engine mount providing the bolts and blind nuts are good quality  and fit well.   Some bolts and blind nuts provided in kits have poor threads so check yours well. I have used 4 mm socket head bolts for years on up to 30cc engines and have never had a problem with the bolts breaking. Nowadays I do not use  'T' shape spike nuts for any stressed fixing. Firstly,  because the metal is quite soft (so that they can be made) and so the threads are soft also. Secondly,  the thread length tends to be quite short.  For a soft metal the good practice is to have threads that are at least twice as long as the bolt diameter,  ie at least 8 mm for a 4 mm bolt.  How much tread is there in your spike nuts ? Thirdly,  they are often very difficult to fix in place especially for engine mounts.  I use nuts from  'Model Fixings'  that are put into place from the front surface of the bulkhead.  The nuts have angled blades around their outside which screws them back into the bulkhead.  They are really easy to use and are very strong.  I give them a spot of thin cyano to finalise them into the ply and have never ever had one fail or loosen.  I can highly recommend them!    Moderator - please tell Alex Whittaker about them, its time he stopped struggling with spike nuts!! Hope this has helped. Richard 

Hi Phil. From your description it may well be a British (Luton) made Magnum but with a different carb.  If you email me your address I will send you a copy of the instruction sheets that I have with my own Magnum. Richard  [[email protected]] 

A friend of mine successfully tows 4mtr gliders using a tug powered with an ST 2500 so you should be OK

As Eric says, just behind the back of the wing is ideal and also some wire, or similar, from the top of the fin down to each end of the tailplane will prevent the tow line snagging in the elevator or rudder. Martin...you said "towhook" but I hope you meant a "tow release" so that you can release the towline in flight when you need to! Providing your runway is long enough, use a longer towline (I use 40 mtrs) rather than a short one because the long line will give a smoother tow. 

Just Engines have Model Technics glowplugs so I intend trying to get some of the new plugs from them when I next order something.  I live in France so I try and combine orders because of postage charges.  You could contact Model Technics and ask them which shop in your area stocks their plugs. I avoid having two strokes fully inverted because they are often less reliable running at low revs and idle than when mounted a bit sideways with the silencer under the middle of the model.  A two stroke engine at idle, even with a correct mixture, has neat fuel sloshing around in the crankcase after a short while and with an inverted engine that fuel falls into the ports and affects the running.  Hence with an inverted engine the tendency is to weaken the idle mixture too much to try and stop the plug getting flooded. Using a four stroke plug that has an extended nose helps stop the plug element becoming flooded.  Not all fourstroke plugs have an extended nose like the OS'F' .  I have used an OS'F' plug often to help other flyers having trouble with their inverted two strokes and results have always been good once the carb settings have been reset properly from where they were after people messed around with them trying to get their engines running better! An OS'F' fourstroke plug is a Medium Heat Range plug and as such also suits most two stroke engines  and does not alter the ignition timing. Be carefull though before putting an extended nose plug into a small engine, such as a 15 size, in case the plug nose hits the piston!   To make sure that there is enough clearance firstly instal the plug without a washer and then gently turn the engine to make sure that there is no contact.  Then refit the washer on the plug and you will have a safe clearance. People also often have their fuel tank too high, relative to the carb spraybar, with an inverted engine.  So it is always worth checking and fixing.  The tank should be centred on or preferably a little below the spraybar. Hope this helps someone!! 

Include me too please.  Thanks

There is a new glowplug by Model Technics intended for two stroke engines.  As well as improved throttle response for 3D flying it also has an extended nose to help avoid flooding the plug if neat fuel runs down into the combustion chamber of an inverted engine.  Anyone tried it yet?

Hi Phil. If you search on the FFAM (French equivalent of the BMFA) site you should find the clubs and contacts listed by areas.  I do not have the site bookmarked since changing my computer but it was easy to find before. I fly in the Dordogne region of France and we have some really excellent sites here.  The club at Bergerac has a new flying site with 150 metre long 10 metre wide tarmac strip.  No restrictions on flying times or days either!   The weather is also much better than UK.  You would be made welcome Richard 

Colin. The British Magnum was made in Luton.  I have checked and confirmed that I do have the instructions.   I am on a weak dial-up service in france so probably could not send you a file as an attachment so will send you a hard copy if you email ([email protected])  me your address.  Best Regards Richard 

Kevin. Model Technics' Propower 10% Nitro is excellent and will run cleaner than Formula Irvine Contest 10.  Propower has the 18% oil content that OS specify for warranty. Regarding the nitro level be aware that nitro content can be by weight or volume.  You get less of the expensive nitro in your fuel if the blend is by weight because nitro is relatively heavy.  Roughly speaking a fuel with 15% nitro by weight has the same ammount of nitro as 10% nitro by volume.  American fuels are often blended by weight and I suspect that the OS specification reflects that also.  The Model Technics fuels are blended by volume  so 10% nitro Propower matches 15% American fuel. Enjoy your return to flying. Richard 

I have a 90 size version of the British Magnum 4str.  Would a copy of those instructions be any use to you? Richard