Brian Parker

If anyone is interested, my ‘handful’ of single 120mAh cells arrived today from Component-shop. Solder tagged cells at 40P each and £1 postage.  A 4.8v battery made up from the cells with a surplus plug (from an old servo) costs me £1.60. The 120mAh battery will give ample flying time. The three 3.7g micro servo’s draw 6.1mA each at idle, the Corona dual conversion receiver 15.3mA.  A total 33.6mA. Vigorous stirring of transmitter sticks gave maximum of 140mA. Simulated normal operation up to 2/3 of max. Plus I have a pocketful of spare batteries. The little Discus maiden flight was less than successful the wing bearing shattered on landing. Being a cheapskate I had fabricated the bearing from a ‘Charity’ pen casing and some aluminium tubing I had lying around. On investigation the casing was rendered extremely brittle, probably a reaction from the cyano glue. Back to the drawing board!

Component-shop.co.uk list suitable batteries (1/4AAA NiMH, 1/3AAA etc) but are currently ‘out-of-stock’. They do have single cells in stock to build up your own. The little fox is great fun, I have been flying mine on an ‘ex-toy’ 350mAh NiMH battery but in order to reduce weight intend to change to the Component-shop 1/4AAAs (120mAh) when the cells  arrive. I have also converted the Graupner 650mm span Mini Discus to directional wings (pitcherons). Just waiting for suitable weather to try it out!

Simon, Yes, LT at ends and HT at the centre. HT is around 5Kohms, LT minimal resistance and voltage is 3Volts. Looks like a cardboard version of the modelelectric and micro-model coils. Brian.

Yes..We have to up here, it rains most of the time!

Simon, Yes, you’re probably correct in the posting. The ‘5cc’ is running proof that it is possible although “applied quite easily to any 4 stroke” may be an understatement.   I quite agree that fuel/oil mix doesn’t sit comfortably with a four stroke and has got to be a cop-out. Probably because an oil failure in flight would be terminal, also the higher operational skill needed increases the risk of this happening. As for the Gettig, I’m sure it’s up to the job but at 3-volts operation (same as the Modelectric) it will need a reliable condenser and adequate dwell. Assisting the CB with a transistor would increase contact life and boost the coils magnetic collapse. This would still maintain the integrity of the design. Out of interest do you know the material  is used for the contacts, a tungsten rivet was favoured but not now available. Brian.

Simon, Does this latest posting not belong to your ‘5cc Found’ thread rather that in ‘4 stroke lub? Looking forward to the video. Have you decided on a suitable model yet? A bit late now but I notice that Hemingway Kits, at Bridgnorth are now stocking the ‘Exciter’ ignition coil. Rather heavy at 4.3oz it’s 2 inches long and can handle 6volts. Priced at  £35 including condenser. Rather expensive but probably reflects low volume sales. As you are probably aware with all these coils a 10k ohm series resister in the HT lead will help reduce RF interference (RFI).   Good luck and progress, Brian.

Slope soaring at it’s best? Yesterday, my flying mate and I took the Zagis up the fell for, as we thought, a mornings entertainment. Second flight in, slight drizzle, nothing to worry about, it will soon stop. Mistake!  Sudden downpour drove my zagi into the gorse. After ¾ hours wet and prickly search the sodden (correct term) zagi was recovered. By now the weather had cleared. On with the game. Second mistake! Water logged transmitter decided I needed permanent full throws. Into the gorse again. Recovered but flying over for the day for me. Still mate able to fly. Third mistake! His Zagi decides it has had enough and starts to Ignite! Frantic tearing of the Zagis innards prevented meltdown. Called it a day! Hot air gun to the wayward transmitter soon had it back to full operation.  Epoxy, the odd piece of balsa, a length of cable and a spot of soldering and we are both ready for the off. Raining all day today! Not much different to normal to be honest!

For this to work we would have to create/maintain an appropriate pressure differential between crankcase and rocker housing whilst at the same time provide drainage….difficult.  Also, we are we not fixing what needs no fixing. On a similar but probably irrelevant theme, many years ago (late 1950’s early 60’s) I owned a much modified 1930’s AJS ramped cam ‘competition’ motorcycle with oil nipples/reservoir connected to the open rocker/valve/hair-pin spring mechanism by small bore piping, excess lubrication draining to atmosphere (actually onto the hot exhaust). Are oil nipples a solution to our non-existing problem? As I remember the motorcycle had ample power but limited braking causing apprehension to ‘pilot’ and onlookers.… i.e. much like my flying today!   PS. I sold the AJS on for £5…what would it be worth in todays market?

 Are Glow Plug  threads  not 1 /4 X 32 TPI ?

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They are the pushrod tubes. If the dent is such that the pushrod is fouling, then replace. If you have had to ask this question then you will probably need some assistance to repair.

Once again someone leaps in without properly reading through all the postings on the thread. In retrospect, perhaps my reply to Timbo’s question was a little flippant but regarding the indexing through the change gear wheels…. The lathe is not turning and is isolated from the mains, no torque is being transmitted through the gears (in any event, working from the lower change gear upwards would result in a torque reduction, typically in the order of 16:1[if there was any at all]) and obviously care would be used when ‘locking’ the gears, as I stated originally.  In fact, because of the gearing and the lack of torque, it is possible to complete the operation by just holding the lower change wheel with the right-hand and advancing the slide/tool post with the left-hand with very little loss of angular precision, indeed it’s probably as accurate as using a baulk of timber. We are talking aluminium after all. I will continue in my usual practice!

The circuit probably lacks a ‘soft start’ ie.. a thermister in series from the supply to Eric’s smoothing capacitor.

To back up Eric’s argument on mobile phone and frequency separation I connected my trusty ‘scope to an e-sky 35Mhz 6 channel receiver and used Futaba Sky Sport 6, T6EXA and a JR Apex 7 channel Transmitter. Result… No interference at all from ‘phone either when close to transmitter or receiver or with transmitters at bottom of garden (with aerial part down). Only glitching encountered was from the 6EXA independent from the ‘phone  (limit of range?). Images below. Excuse un-calibrated probe. No glitch. Glitch.

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Paxolin is composite material similar to printed circuit board (PCB) material. Tufnol is also a similar material. Both can be machined. Just use a modern hinge material.

Alex,  The air bleed will be pre-set and should be left as set, particularly during running-in.  As a guide only........ Any subsequent adqustment (if needed) should be done 1/8th of a turn at a time and with patience. With a warm engine at idle, open the throttle fully, if slow to pick-up and excess white smoke, engine is rich, screw clockwise 1/8th turn. Let engine idle, try again until engine picks up cleanly. If engine has no smoke on opening throttle and cuts, the engine mixture is weak, screw out 1/8th turn. Let idle, try again, repeat the above until correct, with patience.

 Simon, Progress! Congratulations! Of some relevant interest on the subject of Ignition Systems. Last week I managed to pick up a ‘Modelelectic’ style coil (Micro Model Engineering) complete with a TIM4 module, both unused, from e-bay for less than the price of a TIM6 kit. Actually I was more interested in the coil, the TIM is basic but it will save me having to build one, so I will probably use it. Are you familiar with these units? They are obviously not as efficient as a CDI module, but are compact, run off 3volts (3 nicads), would suit your engine and also enable you to retain the CB. They have no auto-advance, so this needs to be overcome. The longer duration spark, as compared to a CDI unit  can for many engines be an advantage despite the much lower HT volts. They can of course be used with Hall effect if desired. Although no longer in production the coils (and the TIMs) do appear on e-bay from time to time. I was the only bidder for mine and so got them for the starting price (higher than I would have liked but you can’t win them all).   

Or this?

Like this?

Simon, I’ve been re-reading through the thread. Could there be something amiss with the set-up? On the endurance test, the engine, on its original carburettor, was inverted. The oil scavenge must at that time have been effective or surely the inverted engine would have been overcome soon after starting.

Suspended more likely!    

Yes, Simplified, Thermoclines are the result of Temperature inversions. In water the temperature is a critical factor 4 degrees C for fresh water and -2 degrees for the ocean.  Not sure if there is a critical  temperature for air. This is way of topic, better look out for Timbo!

Thermoclines ….Yes, perhaps not relevant but interesting, causes warm water to float on cold water (KISS) and clouds to sit at the bottom of mountains. A possible alternative energy source?