Merco 61

Hello, Some very good advice,all taken on board. Progress so far.Cut two new shims from litho,timing checked again,tappets set,stronger spinner fitted.new heavier clunk filter(sintered) tank level raised ,no pressure to tank.OS 3 plug.Instant start,steady idle about 2000,open up to full and ran the tank out.Plug connected throughout.Repeat but motor slowly slowed and stopped at about mid throttle without power to plug,not overly worried by this,will try a few different 4str plugs.The engine is quite a different animal now,quite benign but still turns the 16x6 at 8300 which is adequate for intended model(s) and is noticeably quieter.Still a tendency for prop to slip a few degrees when the starter is applied but this,I think is due to my leather washers bedding in.I think they afford a little shock absorbing so no bad thing in case of any further detonations so kinder to the con rod. Best of all,the prop stayed put!! Still some fine tuning to do but may yet come to like this engine.If the pictures attach,hopefully will show the shims and two models for the engine.P51 is based on the Galaxy kit but with home made cowl,Stuka is from John Carpenter plan. Thanks to you all Cheers for now

Its very nice of all of you to show an interest,I appreciate it very much.These engines were mass-produced probably in considerable numbers on CNC machines so a fundamental design error should not be possible.I repeat,the quality and internal fits are quite amazing and there really seems little scope for errors in final assembly.Its had about two hours running now,albeit,at low to moderate revs and pretty rich.Dont think it would have managed this if something was too far out mechanically.It appears to be a short stroke,perhaps even over-square but I lack the skill to prove this.Initially the compression/resistance was excessive but this has improved ,as has the addition of an extra shim.Thanks Cymaz.I have been cutting some more rings this evening.Wanted more accuracy than compass cut,so did it this way:Cut a piece if 1/16 birch ply,then Evostik two similar sized pieces of litho plate to make a three layer sandwich.Centrepop with small sharp tool and mark out with scriber in metal compasses.You then get a really fine guideline.Then used my finest (000) piercing saw to cut out ring. Finish edges with wet and dry,immerse in a saucer of acetone which will quickly float the wood and litho apart.No ragged edges or buckling and annealing not necessary.I,ve done similar in the past on my little lathe using copper shim,but sawing is almost as accurate and a lot easier to mark out.As far as throwing the prop: this really has to be a backfire/pre-ignition,which in a non-retardable engine has to a weak mixture. doesnt it? I will persist,and with your help,how can we fail?Cheers for now. Look forward to hearing from you Bucksboy.

Hello. Jon,your long stroke 120 is superb,most impressed. What a delightful engine.Sincere respects. I,ve followed all the hints and tips,checked and double checked timing,tappets,leaks,internals are a work of art,modded prop driver.At the test stand,the TT starts first time so a series of ten minute runs at varying speed with no problem.Power increased very slowly to 2/3rds.This is a very powerful engine indeed (reputedly 2.5 HP) and even at this setting would be more than enough for intended airframes,all scratch built scale heavyweights.Then went for full power,holding tachometer just behind prop.Very gradually opened up,squeak,bang whirrr.Bits of shattered nylon spinner,nuts and screws in the face and the prop travelled thirty feet sideways and cleared the 8foot hedge. Rather unsettling to say the least. The responsible thing would to be to put it on the shelf with the other interesting but impractical collectors engines and forget it. However a little voice wonders if further de-regulation by adding another shim,running it on nil-nitro synth fuel,and perhaps incorporating a throttle stop so that it cannot be opened beyond 3/4 might tame it sufficiently to become a "user". Dont think it will ever be a relaxing engine to operate without incorporating a new professionally designed four through-bolt hub but the cost of getting one made would be prohibitive. You must all be heartily sick of reading my posts on this subject,so will promise not to bother you any more.Thanks to you all for your valued imput.

Hello, After a further two days of work,thought my results might be of interest.First,you are quite right Jon,there is a shim in place,fits so well you can hardly see it.I fitted an extra one as an experiment and have found a better way of making them.Fitted engine upright in test stand,16x6 Master,and achieved a start.Opened up a degree,prop went skyward.Refitted everything but this time discarded emery double washers and substituted friction washers cut from 1/16 hard leather.Sourced from an old ladies sandel,stolen from an old ladies shoe cupboard.Easy restart,enough to get slow needle set a little better which permitted a gradual approach to about 3/4 max revs.Richened main needle,one more click open and prop departed again.Decided to establish once and for all where slipping was happening so made up some more back to back washers,only this time cut from the Velco type and this time,put one between the prop driver and prop.Prop let go a further three times but it did show that only the prop driver one was destroyed,the others were fine.Larger leathers washer now fitted,restart and all pretty good.From what I,ve read,the very first motor cars and motor cycles were fitted with cone clutches lined with leather but not sure if they ran dry or in oil.In any event we have some progress and I was able to run out a couple of big tanksful,but not at max as I am a coward.I did notice something else-as the fuel level reduced,air bubbles could be seen in the line and on a couple of occasions were the sure fire prelude to the dreaded bang .and nut loosening.Tank level raised so pick up is now slightly higher than card jet cured this. I want to continue with bench tests before putting it back in the model ,it would be dangerous to clubmates,these are powerful machines and have to be right.Would seem that the "blunt" edges to the knurling (probably die-stamped) is the main cause of all my problems and I,m looking at trying to re-sharpen them with a diamond burr or even a reshaped 1/8" wood chisel.

Hi Cymaz, Thats very encouraging.To clarify-was metal actually missing from piston skirt? Sorry,I,m not a pro engineer so dont understand what dialled in means. From what I,ve read,TT 130s seem to have suffered in the piston department.Perhaps I,m not the only one to have bought one with the shim missing? Good of you to offer push rods,will get back to you if needed.Many thanks.

Hello , Having spent a couple of days of careful but sweaty fiddling to no real avail,have removed the engine from the model and thoroughly ,cleaned it ready for some dismantling. So far,have not found a clear exploded view on the Web, but notice that a gasket set is(was) offered on a site.It shows what is obviously an alloy head gasket..When cyl head was removed,no sign of any gasket.Engine Doc was quite right.Pretty sure we now know the reason for the excessive compression and the feeling that the engine is grossly over-advanced.Also,one push rod quite badly bent but was easily hammered straight. I am now in the process of cutting some gaskets,some from new food trays,some from litho.A few fails with the shonky plastic compass cutter but hoping persistence will reward. I want to experiment with different thicknesses to see if I can calm this engine down a bit.Internally,everything is as new and looks and feels very good indeed so the big black depression cloud is lifting gradually. I may yet be forced to resort to fitting a couple of drive pins into the face of prop driver as the peaks on the spiral "knurling" are now quite blunted and cannot be easily re- sharpened,therefore not much bite into the rear of prop hub .This would be a permanent commitment to wood props,given the variety of moulding patterns in nylon prop hubs and making a drilling jig would be next to impossible.My thanks to all for your kind help.

Hello again. Many thanks to all for your kind advice,particularly Jon,an amazing offer which I may well take up.Tried the short reach plug and richened everything to ridiculous level,still kicking the prop off. I feel that until I can keep the prop in place ,I stand no chance of adjusting the carb to get a true picture of the engines characteristics.I,m now cogitating furiously to come up with a material to make friction washers from.Having doubts about the back to back glued emery disks-don't see how it can possibly dig into a steel washer.Am looking some thin leather at the moment and will give it a try.Giving them a thin coat of contact adhesive might be an idea.Friction is what is needed.Shame about all this messing about,I think I was seduced by the undeniable good looks of the 130. Will persist.

About three weeks ago,I was loitering at home in Lincoln,awaiting the return of the Lancaster from Duxford after its repairs.It eventually approached from the South,but most unusually it was at great altitude.BBMF aircraft normally pass over us at about 500 feet,often much lower.Which I like very much.On this occasion I estimate it at about 6000.It then circled three or four times with a Gryphon Spit on its wing tip.What was different was the engine sound.The engines or engine was really howling and I was actually quite alarmed.I have never heard a Merlin revved so hard except in "The Dam Busters"when they are trying to clear the high ground.It most certainly sounded as if something was badly amiss ,or I was witnessing the severest of engine tests.I expected her to then head up towards Coningsby,but she turned and headed back South.

Thanks very much for the response boys,some good and sound advice.To clarify my question,I,m using 5% with half and half synthetic/castor and OS F plug (new) Plug running from a separate batt via usual mosfet panel.16x6 Master broad blade. Starter from car batt. Woodruff firmly in place.The supplied lock nuts are useless,as you say,as there are only two or three threads on the internal coned outer nut.I,m using a substantial ring spanner on SC nuts but am not accustomed to having to use so much force-feels excessive and brutal.I like the idea of lowering compression,the comp on this engine is massive.A bit like trying to flick start a BSA Gold Star! I would not dream of hand starting this one. I,ve lost the settings on slow needle which is probably the problem.My method is to set main needle to full power,close barrel down onto a pin,connect a bit of fuel tube to carb inlet and blow,adjusting slow needle until I can just detect a hiss.Old as the hills but usually gives an approximate set up ready for fine adjustment.But it aint working on this engine.Cymaz,could you please tell me more about your mods to piston skirt,and what I should be looking for with back plate off.Finally,valve clearances are now spot on but did notice that there was no oil residue in rocker cover.Again,my sincere thanks to you all. PS Re Nats.Am I the only one who wishes the sound of those lovely aero engines on the display line had not been drowned out by all those speakers pumping out loud musack and verbal irrelevance?

I have been struggling to master a new Thunder Tiger 130 for about a week.I am pretty experienced with four strokes and most other aero engines but this one has me beaten. It is throwing props.I,ve tried all the usual fixes-plugs,emery washers,very rich needle settings,various fuels,but it keeps loosening the prop nuts with an alarming "crack".I have achieved a few runs but have been unable to get it to run burbling rich which is a worry-almost as if the main needle is too short.I,ve tried various GFP props between 15 and 18" and some wood,which are even worse..Sometimes I can get a very slow run with the throttle closed right down to a pinhole-almost oscillating-but even opening up using just a click on the throttle trim is enough to provoke a bang and a dive to avoid the flying prop.Have also tried reducing power to plug to reduce "over-advanced" syndrome. Please,can anyone release me from this tyranny?

Hello onetenor, Thankyou-twice in a day, Sounds interesting and not too difficult.As you say-nothing to lose,everything to gain. Will give it a try.

Thanks Manish and onetenor,I,m sure you are both right. I was just following the Saito instructions for two cell arrangement ,and,which,incidentally insist that I use 15% castor! Here we go again,more fuel angst. Back in the 60s,it was common practice to take a large wood saw and cut a cell off the end of a redundant car battery.A bit messy but would yield a reliable free 2 volt cell for glow which only needed a charge once a year.

Hi, Thanks for your help,quite reassured that your Saito will haul 12 lbs.Can I ask another question? I have not run the engine yet and am wondering about glow connections.I dont have much faith in the little glo-stick 1.2 volt gadgets,and I,m wary of using two leads in parallel from flight box panel.DMStech.co.uk offer substantial single cell lead acid batts at 2 volts 2.5 Ah.A pair of these would seem to be an idea. How do you do it? Merco.

Hello all, Many thanks for your interest and advice.Particularly intrigued by Cymaz CDI conversion,and that others have found a liquid prime necessary on this particular engine. That powerful starter from J,en with lipo makes a lot of sense too. As I already have a couple of CDI rigs,is it a case of carefully drilling the (huge) prop driver for the magnet at the required position? Can the mag and flywheel then be removed completely?Any additional work to do after flywheel removed? Merco.

Hello, Can anyone make my life easier? I have a Kalt/Zenoah 23 mag petrol engine,which I,ve used for a number of years in WW1 and other scale models.It is a nice quality engine,which idles like a watch but has ample power at full throttle with nice transition.It is,however a blighter to start. My method is to finger choke and flip half a dozen times,open throttle fully then apply-and lean on-a 12 volt starter powered by a small car batt..Not ideal and probably dangerous.Fuel pipes and felt filter are spot on,diaphragm new,carb clinically clean inside and out,fresh petrol at 50-1.After a few minutes run,the engine can be stopped and thereafter will hand start fairly easily at low throttle.Sometimes. I,ve thought about a liquid prime. My Briggs lawn mower needs a hefty 3 squirt prime. I do so envy the other flyers who dont have to lug a car battery around. Please tell me where I,m going wrong.

Hello, I,ve just completed a Balsa USA J3 Cub 1/4 scale.I,ve fitted a Saito boxer mainly because it looks nice and balances the model perfectly.Does look very small though. Model weighs just under 10 lbs,less than specs, I have no intention of doing aeros,but am apprehensive that power might be too marginal for a safe test flight.Specs state a 60 glow is sufficient.Intended prop will be a 15x4 if I can find one. Any opinions,please?

I,ve not built a TSR2,but have some experience of FD2.Mine is from an original Veron kit circa 1956,but modded a lot,to pusher electric.I,ve no experience of PSS but can say with confidence that the FD2 flies very well indeed and is my favourite model.I had some difficulties initially,due to a centre hatch lifting and causing severe pitch down at speed.Remedied by changing hatch fixing and blocking off the big intakes.It does look very nice in the air,although not true scale. Can see no reason why a TSR2 should not fly perfectly well.If you step back from the plan view,it is quite an orthodox layout that just happens to have a long nose! As a bit of light relief from demanding projects,I made a series of pusher jets-DH110,Cutlass,Sukhoi 25,F15 etc,some with elevator separate,some with tailerons.All flew in much the same way.Surprisingly stable and fast.Good fun.

Hello Chris, A pic of the silencers for my Mossie,1/16" brass,silver soldered,quite heavy at 3 ounces each,but effective on OS 25 FSRs.Quieter than standard silencer and the silicon outlet tube will help further.As per plan.Also a pic or two of the UC,again as per plan.More on the album.Hope this helps.